TreeTransform.h

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//===------- TreeTransform.h - Semantic Tree Transformation -----*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//===----------------------------------------------------------------------===//
//
//  This file implements a semantic tree transformation that takes a given
//  AST and rebuilds it, possibly transforming some nodes in the process.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_LIB_SEMA_TREETRANSFORM_H
#define LLVM_CLANG_LIB_SEMA_TREETRANSFORM_H

#include "CoroutineStmtBuilder.h"
#include "TypeLocBuilder.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ExprObjC.h"
#include "clang/AST/ExprOpenMP.h"
#include "clang/AST/Stmt.h"
#include "clang/AST/StmtCXX.h"
#include "clang/AST/StmtObjC.h"
#include "clang/AST/StmtOpenMP.h"
#include "clang/Sema/Designator.h"
#include "clang/Sema/Lookup.h"
#include "clang/Sema/Ownership.h"
#include "clang/Sema/ParsedTemplate.h"
#include "clang/Sema/ScopeInfo.h"
#include "clang/Sema/SemaDiagnostic.h"
#include "clang/Sema/SemaInternal.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/Support/ErrorHandling.h"
#include <algorithm>

namespace clang {
using namespace sema;

/// A semantic tree transformation that allows one to transform one
/// abstract syntax tree into another.
///
/// A new tree transformation is defined by creating a new subclass \c X of
/// \c TreeTransform<X> and then overriding certain operations to provide
/// behavior specific to that transformation. For example, template
/// instantiation is implemented as a tree transformation where the
/// transformation of TemplateTypeParmType nodes involves substituting the
/// template arguments for their corresponding template parameters; a similar
/// transformation is performed for non-type template parameters and
/// template template parameters.
///
/// This tree-transformation template uses static polymorphism to allow
/// subclasses to customize any of its operations. Thus, a subclass can
/// override any of the transformation or rebuild operators by providing an
/// operation with the same signature as the default implementation. The
/// overriding function should not be virtual.
///
/// Semantic tree transformations are split into two stages, either of which
/// can be replaced by a subclass. The "transform" step transforms an AST node
/// or the parts of an AST node using the various transformation functions,
/// then passes the pieces on to the "rebuild" step, which constructs a new AST
/// node of the appropriate kind from the pieces. The default transformation
/// routines recursively transform the operands to composite AST nodes (e.g.,
/// the pointee type of a PointerType node) and, if any of those operand nodes
/// were changed by the transformation, invokes the rebuild operation to create
/// a new AST node.
///
/// Subclasses can customize the transformation at various levels. The
/// most coarse-grained transformations involve replacing TransformType(),
/// TransformExpr(), TransformDecl(), TransformNestedNameSpecifierLoc(),
/// TransformTemplateName(), or TransformTemplateArgument() with entirely
/// new implementations.
///
/// For more fine-grained transformations, subclasses can replace any of the
/// \c TransformXXX functions (where XXX is the name of an AST node, e.g.,
/// PointerType, StmtExpr) to alter the transformation. As mentioned previously,
/// replacing TransformTemplateTypeParmType() allows template instantiation
/// to substitute template arguments for their corresponding template
/// parameters. Additionally, subclasses can override the \c RebuildXXX
/// functions to control how AST nodes are rebuilt when their operands change.
/// By default, \c TreeTransform will invoke semantic analysis to rebuild
/// AST nodes. However, certain other tree transformations (e.g, cloning) may
/// be able to use more efficient rebuild steps.
///
/// There are a handful of other functions that can be overridden, allowing one
/// to avoid traversing nodes that don't need any transformation
/// (\c AlreadyTransformed()), force rebuilding AST nodes even when their
/// operands have not changed (\c AlwaysRebuild()), and customize the
/// default locations and entity names used for type-checking
/// (\c getBaseLocation(), \c getBaseEntity()).
template<typename Derived>
class TreeTransform {
  /// Private RAII object that helps us forget and then re-remember
  /// the template argument corresponding to a partially-substituted parameter
  /// pack.
  class ForgetPartiallySubstitutedPackRAII {
    Derived &Self;
    TemplateArgument Old;

  public:
    ForgetPartiallySubstitutedPackRAII(Derived &Self) : Self(Self) {
      Old = Self.ForgetPartiallySubstitutedPack();
    }

    ~ForgetPartiallySubstitutedPackRAII() {
      Self.RememberPartiallySubstitutedPack(Old);
    }
  };

protected:
  Sema &SemaRef;

  /// The set of local declarations that have been transformed, for
  /// cases where we are forced to build new declarations within the transformer
  /// rather than in the subclass (e.g., lambda closure types).
  llvm::DenseMap<Decl *, Decl *> TransformedLocalDecls;

public:
  /// Initializes a new tree transformer.
  TreeTransform(Sema &SemaRef) : SemaRef(SemaRef) { }

  /// Retrieves a reference to the derived class.
  Derived &getDerived() { return static_cast<Derived&>(*this); }

  /// Retrieves a reference to the derived class.
  const Derived &getDerived() const {
    return static_cast<const Derived&>(*this);
  }

  static inline ExprResult Owned(Expr *E) { return E; }
  static inline StmtResult Owned(Stmt *S) { return S; }

  /// Retrieves a reference to the semantic analysis object used for
  /// this tree transform.
  Sema &getSema() const { return SemaRef; }

  /// Whether the transformation should always rebuild AST nodes, even
  /// if none of the children have changed.
  ///
  /// Subclasses may override this function to specify when the transformation
  /// should rebuild all AST nodes.
  ///
  /// We must always rebuild all AST nodes when performing variadic template
  /// pack expansion, in order to avoid violating the AST invariant that each
  /// statement node appears at most once in its containing declaration.
  bool AlwaysRebuild() { return SemaRef.ArgumentPackSubstitutionIndex != -1; }

  /// Whether the transformation is forming an expression or statement that
  /// replaces the original. In this case, we'll reuse mangling numbers from
  /// existing lambdas.
  bool ReplacingOriginal() { return false; }

  /// Returns the location of the entity being transformed, if that
  /// information was not available elsewhere in the AST.
  ///
  /// By default, returns no source-location information. Subclasses can
  /// provide an alternative implementation that provides better location
  /// information.
  SourceLocation getBaseLocation() { return SourceLocation(); }

  /// Returns the name of the entity being transformed, if that
  /// information was not available elsewhere in the AST.
  ///
  /// By default, returns an empty name. Subclasses can provide an alternative
  /// implementation with a more precise name.
  DeclarationName getBaseEntity() { return DeclarationName(); }

  /// Sets the "base" location and entity when that
  /// information is known based on another transformation.
  ///
  /// By default, the source location and entity are ignored. Subclasses can
  /// override this function to provide a customized implementation.
  void setBase(SourceLocation Loc, DeclarationName Entity) { }

  /// RAII object that temporarily sets the base location and entity
  /// used for reporting diagnostics in types.
  class TemporaryBase {
    TreeTransform &Self;
    SourceLocation OldLocation;
    DeclarationName OldEntity;

  public:
    TemporaryBase(TreeTransform &Self, SourceLocation Location,
                  DeclarationName Entity) : Self(Self) {
      OldLocation = Self.getDerived().getBaseLocation();
      OldEntity = Self.getDerived().getBaseEntity();

      if (Location.isValid())
        Self.getDerived().setBase(Location, Entity);
    }

    ~TemporaryBase() {
      Self.getDerived().setBase(OldLocation, OldEntity);
    }
  };

  /// Determine whether the given type \p T has already been
  /// transformed.
  ///
  /// Subclasses can provide an alternative implementation of this routine
  /// to short-circuit evaluation when it is known that a given type will
  /// not change. For example, template instantiation need not traverse
  /// non-dependent types.
  bool AlreadyTransformed(QualType T) {
    return T.isNull();
  }

  /// Determine whether the given call argument should be dropped, e.g.,
  /// because it is a default argument.
  ///
  /// Subclasses can provide an alternative implementation of this routine to
  /// determine which kinds of call arguments get dropped. By default,
  /// CXXDefaultArgument nodes are dropped (prior to transformation).
  bool DropCallArgument(Expr *E) {
    return E->isDefaultArgument();
  }

  /// Determine whether we should expand a pack expansion with the
  /// given set of parameter packs into separate arguments by repeatedly
  /// transforming the pattern.
  ///
  /// By default, the transformer never tries to expand pack expansions.
  /// Subclasses can override this routine to provide different behavior.
  ///
  /// \param EllipsisLoc The location of the ellipsis that identifies the
  /// pack expansion.
  ///
  /// \param PatternRange The source range that covers the entire pattern of
  /// the pack expansion.
  ///
  /// \param Unexpanded The set of unexpanded parameter packs within the
  /// pattern.
  ///
  /// \param ShouldExpand Will be set to \c true if the transformer should
  /// expand the corresponding pack expansions into separate arguments. When
  /// set, \c NumExpansions must also be set.
  ///
  /// \param RetainExpansion Whether the caller should add an unexpanded
  /// pack expansion after all of the expanded arguments. This is used
  /// when extending explicitly-specified template argument packs per
  /// C++0x [temp.arg.explicit]p9.
  ///
  /// \param NumExpansions The number of separate arguments that will be in
  /// the expanded form of the corresponding pack expansion. This is both an
  /// input and an output parameter, which can be set by the caller if the
  /// number of expansions is known a priori (e.g., due to a prior substitution)
  /// and will be set by the callee when the number of expansions is known.
  /// The callee must set this value when \c ShouldExpand is \c true; it may
  /// set this value in other cases.
  ///
  /// \returns true if an error occurred (e.g., because the parameter packs
  /// are to be instantiated with arguments of different lengths), false
  /// otherwise. If false, \c ShouldExpand (and possibly \c NumExpansions)
  /// must be set.
  bool TryExpandParameterPacks(SourceLocation EllipsisLoc,
                               SourceRange PatternRange,
                               ArrayRef<UnexpandedParameterPack> Unexpanded,
                               bool &ShouldExpand,
                               bool &RetainExpansion,
                               Optional<unsigned> &NumExpansions) {
    ShouldExpand = false;
    return false;
  }

  /// "Forget" about the partially-substituted pack template argument,
  /// when performing an instantiation that must preserve the parameter pack
  /// use.
  ///
  /// This routine is meant to be overridden by the template instantiator.
  TemplateArgument ForgetPartiallySubstitutedPack() {
    return TemplateArgument();
  }

  /// "Remember" the partially-substituted pack template argument
  /// after performing an instantiation that must preserve the parameter pack
  /// use.
  ///
  /// This routine is meant to be overridden by the template instantiator.
  void RememberPartiallySubstitutedPack(TemplateArgument Arg) { }

  /// Note to the derived class when a function parameter pack is
  /// being expanded.
  void ExpandingFunctionParameterPack(ParmVarDecl *Pack) { }

  /// Transforms the given type into another type.
  ///
  /// By default, this routine transforms a type by creating a
  /// TypeSourceInfo for it and delegating to the appropriate
  /// function.  This is expensive, but we don't mind, because
  /// this method is deprecated anyway;  all users should be
  /// switched to storing TypeSourceInfos.
  ///
  /// \returns the transformed type.
  QualType TransformType(QualType T);

  /// Transforms the given type-with-location into a new
  /// type-with-location.
  ///
  /// By default, this routine transforms a type by delegating to the
  /// appropriate TransformXXXType to build a new type.  Subclasses
  /// may override this function (to take over all type
  /// transformations) or some set of the TransformXXXType functions
  /// to alter the transformation.
  TypeSourceInfo *TransformType(TypeSourceInfo *DI);

  /// Transform the given type-with-location into a new
  /// type, collecting location information in the given builder
  /// as necessary.
  ///
  QualType TransformType(TypeLocBuilder &TLB, TypeLoc TL);

  /// Transform a type that is permitted to produce a
  /// DeducedTemplateSpecializationType.
  ///
  /// This is used in the (relatively rare) contexts where it is acceptable
  /// for transformation to produce a class template type with deduced
  /// template arguments.
  /// @{
  QualType TransformTypeWithDeducedTST(QualType T);
  TypeSourceInfo *TransformTypeWithDeducedTST(TypeSourceInfo *DI);
  /// @}

  /// The reason why the value of a statement is not discarded, if any.
  enum StmtDiscardKind {
    SDK_Discarded,
    SDK_NotDiscarded,
    SDK_StmtExprResult,
  };

  /// Transform the given statement.
  ///
  /// By default, this routine transforms a statement by delegating to the
  /// appropriate TransformXXXStmt function to transform a specific kind of
  /// statement or the TransformExpr() function to transform an expression.
  /// Subclasses may override this function to transform statements using some
  /// other mechanism.
  ///
  /// \returns the transformed statement.
  StmtResult TransformStmt(Stmt *S, StmtDiscardKind SDK = SDK_Discarded);

  /// Transform the given statement.
  ///
  /// By default, this routine transforms a statement by delegating to the
  /// appropriate TransformOMPXXXClause function to transform a specific kind
  /// of clause. Subclasses may override this function to transform statements
  /// using some other mechanism.
  ///
  /// \returns the transformed OpenMP clause.
  OMPClause *TransformOMPClause(OMPClause *S);

  /// Transform the given attribute.
  ///
  /// By default, this routine transforms a statement by delegating to the
  /// appropriate TransformXXXAttr function to transform a specific kind
  /// of attribute. Subclasses may override this function to transform
  /// attributed statements using some other mechanism.
  ///
  /// \returns the transformed attribute
  const Attr *TransformAttr(const Attr *S);

/// Transform the specified attribute.
///
/// Subclasses should override the transformation of attributes with a pragma
/// spelling to transform expressions stored within the attribute.
///
/// \returns the transformed attribute.
#define ATTR(X)
#define PRAGMA_SPELLING_ATTR(X)                                                \
  const X##Attr *Transform##X##Attr(const X##Attr *R) { return R; }
#include "clang/Basic/AttrList.inc"

  /// Transform the given expression.
  ///
  /// By default, this routine transforms an expression by delegating to the
  /// appropriate TransformXXXExpr function to build a new expression.
  /// Subclasses may override this function to transform expressions using some
  /// other mechanism.
  ///
  /// \returns the transformed expression.
  ExprResult TransformExpr(Expr *E);

  /// Transform the given initializer.
  ///
  /// By default, this routine transforms an initializer by stripping off the
  /// semantic nodes added by initialization, then passing the result to
  /// TransformExpr or TransformExprs.
  ///
  /// \returns the transformed initializer.
  ExprResult TransformInitializer(Expr *Init, bool NotCopyInit);

  /// Transform the given list of expressions.
  ///
  /// This routine transforms a list of expressions by invoking
  /// \c TransformExpr() for each subexpression. However, it also provides
  /// support for variadic templates by expanding any pack expansions (if the
  /// derived class permits such expansion) along the way. When pack expansions
  /// are present, the number of outputs may not equal the number of inputs.
  ///
  /// \param Inputs The set of expressions to be transformed.
  ///
  /// \param NumInputs The number of expressions in \c Inputs.
  ///
  /// \param IsCall If \c true, then this transform is being performed on
  /// function-call arguments, and any arguments that should be dropped, will
  /// be.
  ///
  /// \param Outputs The transformed input expressions will be added to this
  /// vector.
  ///
  /// \param ArgChanged If non-NULL, will be set \c true if any argument changed
  /// due to transformation.
  ///
  /// \returns true if an error occurred, false otherwise.
  bool TransformExprs(Expr *const *Inputs, unsigned NumInputs, bool IsCall,
                      SmallVectorImpl<Expr *> &Outputs,
                      bool *ArgChanged = nullptr);

  /// Transform the given declaration, which is referenced from a type
  /// or expression.
  ///
  /// By default, acts as the identity function on declarations, unless the
  /// transformer has had to transform the declaration itself. Subclasses
  /// may override this function to provide alternate behavior.
  Decl *TransformDecl(SourceLocation Loc, Decl *D) {
    llvm::DenseMap<Decl *, Decl *>::iterator Known
      = TransformedLocalDecls.find(D);
    if (Known != TransformedLocalDecls.end())
      return Known->second;

    return D;
  }

  /// Transform the specified condition.
  ///
  /// By default, this transforms the variable and expression and rebuilds
  /// the condition.
  Sema::ConditionResult TransformCondition(SourceLocation Loc, VarDecl *Var,
                                           Expr *Expr,
                                           Sema::ConditionKind Kind);

  /// Transform the attributes associated with the given declaration and
  /// place them on the new declaration.
  ///
  /// By default, this operation does nothing. Subclasses may override this
  /// behavior to transform attributes.
  void transformAttrs(Decl *Old, Decl *New) { }

  /// Note that a local declaration has been transformed by this
  /// transformer.
  ///
  /// Local declarations are typically transformed via a call to
  /// TransformDefinition. However, in some cases (e.g., lambda expressions),
  /// the transformer itself has to transform the declarations. This routine
  /// can be overridden by a subclass that keeps track of such mappings.
  void transformedLocalDecl(Decl *Old, ArrayRef<Decl *> New) {
    assert(New.size() == 1 &&
           "must override transformedLocalDecl if performing pack expansion");
    TransformedLocalDecls[Old] = New.front();
  }

  /// Transform the definition of the given declaration.
  ///
  /// By default, invokes TransformDecl() to transform the declaration.
  /// Subclasses may override this function to provide alternate behavior.
  Decl *TransformDefinition(SourceLocation Loc, Decl *D) {
    return getDerived().TransformDecl(Loc, D);
  }

  /// Transform the given declaration, which was the first part of a
  /// nested-name-specifier in a member access expression.
  ///
  /// This specific declaration transformation only applies to the first
  /// identifier in a nested-name-specifier of a member access expression, e.g.,
  /// the \c T in \c x->T::member
  ///
  /// By default, invokes TransformDecl() to transform the declaration.
  /// Subclasses may override this function to provide alternate behavior.
  NamedDecl *TransformFirstQualifierInScope(NamedDecl *D, SourceLocation Loc) {
    return cast_or_null<NamedDecl>(getDerived().TransformDecl(Loc, D));
  }

  /// Transform the set of declarations in an OverloadExpr.
  bool TransformOverloadExprDecls(OverloadExpr *Old, bool RequiresADL,
                                  LookupResult &R);

  /// Transform the given nested-name-specifier with source-location
  /// information.
  ///
  /// By default, transforms all of the types and declarations within the
  /// nested-name-specifier. Subclasses may override this function to provide
  /// alternate behavior.
  NestedNameSpecifierLoc
  TransformNestedNameSpecifierLoc(NestedNameSpecifierLoc NNS,
                                  QualType ObjectType = QualType(),
                                  NamedDecl *FirstQualifierInScope = nullptr);

  /// Transform the given declaration name.
  ///
  /// By default, transforms the types of conversion function, constructor,
  /// and destructor names and then (if needed) rebuilds the declaration name.
  /// Identifiers and selectors are returned unmodified. Sublcasses may
  /// override this function to provide alternate behavior.
  DeclarationNameInfo
  TransformDeclarationNameInfo(const DeclarationNameInfo &NameInfo);

  /// Transform the given template name.
  ///
  /// \param SS The nested-name-specifier that qualifies the template
  /// name. This nested-name-specifier must already have been transformed.
  ///
  /// \param Name The template name to transform.
  ///
  /// \param NameLoc The source location of the template name.
  ///
  /// \param ObjectType If we're translating a template name within a member
  /// access expression, this is the type of the object whose member template
  /// is being referenced.
  ///
  /// \param FirstQualifierInScope If the first part of a nested-name-specifier
  /// also refers to a name within the current (lexical) scope, this is the
  /// declaration it refers to.
  ///
  /// By default, transforms the template name by transforming the declarations
  /// and nested-name-specifiers that occur within the template name.
  /// Subclasses may override this function to provide alternate behavior.
  TemplateName
  TransformTemplateName(CXXScopeSpec &SS, TemplateName Name,
                        SourceLocation NameLoc,
                        QualType ObjectType = QualType(),
                        NamedDecl *FirstQualifierInScope = nullptr,
                        bool AllowInjectedClassName = false);

  /// Transform the given template argument.
  ///
  /// By default, this operation transforms the type, expression, or
  /// declaration stored within the template argument and constructs a
  /// new template argument from the transformed result. Subclasses may
  /// override this function to provide alternate behavior.
  ///
  /// Returns true if there was an error.
  bool TransformTemplateArgument(const TemplateArgumentLoc &Input,
                                 TemplateArgumentLoc &Output,
                                 bool Uneval = false);

  /// Transform the given set of template arguments.
  ///
  /// By default, this operation transforms all of the template arguments
  /// in the input set using \c TransformTemplateArgument(), and appends
  /// the transformed arguments to the output list.
  ///
  /// Note that this overload of \c TransformTemplateArguments() is merely
  /// a convenience function. Subclasses that wish to override this behavior
  /// should override the iterator-based member template version.
  ///
  /// \param Inputs The set of template arguments to be transformed.
  ///
  /// \param NumInputs The number of template arguments in \p Inputs.
  ///
  /// \param Outputs The set of transformed template arguments output by this
  /// routine.
  ///
  /// Returns true if an error occurred.
  bool TransformTemplateArguments(const TemplateArgumentLoc *Inputs,
                                  unsigned NumInputs,
                                  TemplateArgumentListInfo &Outputs,
                                  bool Uneval = false) {
    return TransformTemplateArguments(Inputs, Inputs + NumInputs, Outputs,
                                      Uneval);
  }

  /// Transform the given set of template arguments.
  ///
  /// By default, this operation transforms all of the template arguments
  /// in the input set using \c TransformTemplateArgument(), and appends
  /// the transformed arguments to the output list.
  ///
  /// \param First An iterator to the first template argument.
  ///
  /// \param Last An iterator one step past the last template argument.
  ///
  /// \param Outputs The set of transformed template arguments output by this
  /// routine.
  ///
  /// Returns true if an error occurred.
  template<typename InputIterator>
  bool TransformTemplateArguments(InputIterator First,
                                  InputIterator Last,
                                  TemplateArgumentListInfo &Outputs,
                                  bool Uneval = false);

  /// Fakes up a TemplateArgumentLoc for a given TemplateArgument.
  void InventTemplateArgumentLoc(const TemplateArgument &Arg,
                                 TemplateArgumentLoc &ArgLoc);

  /// Fakes up a TypeSourceInfo for a type.
  TypeSourceInfo *InventTypeSourceInfo(QualType T) {
    return SemaRef.Context.getTrivialTypeSourceInfo(T,
                       getDerived().getBaseLocation());
  }

#define ABSTRACT_TYPELOC(CLASS, PARENT)
#define TYPELOC(CLASS, PARENT)                                   \
  QualType Transform##CLASS##Type(TypeLocBuilder &TLB, CLASS##TypeLoc T);
#include "clang/AST/TypeLocNodes.def"

  template<typename Fn>
  QualType TransformFunctionProtoType(TypeLocBuilder &TLB,
                                      FunctionProtoTypeLoc TL,
                                      CXXRecordDecl *ThisContext,
                                      Qualifiers ThisTypeQuals,
                                      Fn TransformExceptionSpec);

  bool TransformExceptionSpec(SourceLocation Loc,
                              FunctionProtoType::ExceptionSpecInfo &ESI,
                              SmallVectorImpl<QualType> &Exceptions,
                              bool &Changed);

  StmtResult TransformSEHHandler(Stmt *Handler);

  QualType
  TransformTemplateSpecializationType(TypeLocBuilder &TLB,
                                      TemplateSpecializationTypeLoc TL,
                                      TemplateName Template);

  QualType
  TransformDependentTemplateSpecializationType(TypeLocBuilder &TLB,
                                      DependentTemplateSpecializationTypeLoc TL,
                                               TemplateName Template,
                                               CXXScopeSpec &SS);

  QualType TransformDependentTemplateSpecializationType(
      TypeLocBuilder &TLB, DependentTemplateSpecializationTypeLoc TL,
      NestedNameSpecifierLoc QualifierLoc);

  /// Transforms the parameters of a function type into the
  /// given vectors.
  ///
  /// The result vectors should be kept in sync; null entries in the
  /// variables vector are acceptable.
  ///
  /// Return true on error.
  bool TransformFunctionTypeParams(
      SourceLocation Loc, ArrayRef<ParmVarDecl *> Params,
      const QualType *ParamTypes,
      const FunctionProtoType::ExtParameterInfo *ParamInfos,
      SmallVectorImpl<QualType> &PTypes, SmallVectorImpl<ParmVarDecl *> *PVars,
      Sema::ExtParameterInfoBuilder &PInfos);

  /// Transforms a single function-type parameter.  Return null
  /// on error.
  ///
  /// \param indexAdjustment - A number to add to the parameter's
  ///   scope index;  can be negative
  ParmVarDecl *TransformFunctionTypeParam(ParmVarDecl *OldParm,
                                          int indexAdjustment,
                                          Optional<unsigned> NumExpansions,
                                          bool ExpectParameterPack);

  /// Transform the body of a lambda-expression.
  StmtResult TransformLambdaBody(LambdaExpr *E, Stmt *Body);
  /// Alternative implementation of TransformLambdaBody that skips transforming
  /// the body.
  StmtResult SkipLambdaBody(LambdaExpr *E, Stmt *Body);

  QualType TransformReferenceType(TypeLocBuilder &TLB, ReferenceTypeLoc TL);

  StmtResult TransformCompoundStmt(CompoundStmt *S, bool IsStmtExpr);
  ExprResult TransformCXXNamedCastExpr(CXXNamedCastExpr *E);

  TemplateParameterList *TransformTemplateParameterList(
        TemplateParameterList *TPL) {
    return TPL;
  }

  ExprResult TransformAddressOfOperand(Expr *E);

  ExprResult TransformDependentScopeDeclRefExpr(DependentScopeDeclRefExpr *E,
                                                bool IsAddressOfOperand,
                                                TypeSourceInfo **RecoveryTSI);

  ExprResult TransformParenDependentScopeDeclRefExpr(
      ParenExpr *PE, DependentScopeDeclRefExpr *DRE, bool IsAddressOfOperand,
      TypeSourceInfo **RecoveryTSI);

  StmtResult TransformOMPExecutableDirective(OMPExecutableDirective *S);

// FIXME: We use LLVM_ATTRIBUTE_NOINLINE because inlining causes a ridiculous
// amount of stack usage with clang.
#define STMT(Node, Parent)                        \
  LLVM_ATTRIBUTE_NOINLINE \
  StmtResult Transform##Node(Node *S);
#define VALUESTMT(Node, Parent)                   \
  LLVM_ATTRIBUTE_NOINLINE \
  StmtResult Transform##Node(Node *S, StmtDiscardKind SDK);
#define EXPR(Node, Parent)                        \
  LLVM_ATTRIBUTE_NOINLINE \
  ExprResult Transform##Node(Node *E);
#define ABSTRACT_STMT(Stmt)
#include "clang/AST/StmtNodes.inc"

#define OPENMP_CLAUSE(Name, Class)                        \
  LLVM_ATTRIBUTE_NOINLINE \
  OMPClause *Transform ## Class(Class *S);
#include "clang/Basic/OpenMPKinds.def"

  /// Build a new qualified type given its unqualified type and type location.
  ///
  /// By default, this routine adds type qualifiers only to types that can
  /// have qualifiers, and silently suppresses those qualifiers that are not
  /// permitted. Subclasses may override this routine to provide different
  /// behavior.
  QualType RebuildQualifiedType(QualType T, QualifiedTypeLoc TL);

  /// Build a new pointer type given its pointee type.
  ///
  /// By default, performs semantic analysis when building the pointer type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildPointerType(QualType PointeeType, SourceLocation Sigil);

  /// Build a new block pointer type given its pointee type.
  ///
  /// By default, performs semantic analysis when building the block pointer
  /// type. Subclasses may override this routine to provide different behavior.
  QualType RebuildBlockPointerType(QualType PointeeType, SourceLocation Sigil);

  /// Build a new reference type given the type it references.
  ///
  /// By default, performs semantic analysis when building the
  /// reference type. Subclasses may override this routine to provide
  /// different behavior.
  ///
  /// \param LValue whether the type was written with an lvalue sigil
  /// or an rvalue sigil.
  QualType RebuildReferenceType(QualType ReferentType,
                                bool LValue,
                                SourceLocation Sigil);

  /// Build a new member pointer type given the pointee type and the
  /// class type it refers into.
  ///
  /// By default, performs semantic analysis when building the member pointer
  /// type. Subclasses may override this routine to provide different behavior.
  QualType RebuildMemberPointerType(QualType PointeeType, QualType ClassType,
                                    SourceLocation Sigil);

  QualType RebuildObjCTypeParamType(const ObjCTypeParamDecl *Decl,
                                    SourceLocation ProtocolLAngleLoc,
                                    ArrayRef<ObjCProtocolDecl *> Protocols,
                                    ArrayRef<SourceLocation> ProtocolLocs,
                                    SourceLocation ProtocolRAngleLoc);

  /// Build an Objective-C object type.
  ///
  /// By default, performs semantic analysis when building the object type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildObjCObjectType(QualType BaseType,
                                 SourceLocation Loc,
                                 SourceLocation TypeArgsLAngleLoc,
                                 ArrayRef<TypeSourceInfo *> TypeArgs,
                                 SourceLocation TypeArgsRAngleLoc,
                                 SourceLocation ProtocolLAngleLoc,
                                 ArrayRef<ObjCProtocolDecl *> Protocols,
                                 ArrayRef<SourceLocation> ProtocolLocs,
                                 SourceLocation ProtocolRAngleLoc);

  /// Build a new Objective-C object pointer type given the pointee type.
  ///
  /// By default, directly builds the pointer type, with no additional semantic
  /// analysis.
  QualType RebuildObjCObjectPointerType(QualType PointeeType,
                                        SourceLocation Star);

  /// Build a new array type given the element type, size
  /// modifier, size of the array (if known), size expression, and index type
  /// qualifiers.
  ///
  /// By default, performs semantic analysis when building the array type.
  /// Subclasses may override this routine to provide different behavior.
  /// Also by default, all of the other Rebuild*Array
  QualType RebuildArrayType(QualType ElementType,
                            ArrayType::ArraySizeModifier SizeMod,
                            const llvm::APInt *Size,
                            Expr *SizeExpr,
                            unsigned IndexTypeQuals,
                            SourceRange BracketsRange);

  /// Build a new constant array type given the element type, size
  /// modifier, (known) size of the array, and index type qualifiers.
  ///
  /// By default, performs semantic analysis when building the array type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildConstantArrayType(QualType ElementType,
                                    ArrayType::ArraySizeModifier SizeMod,
                                    const llvm::APInt &Size,
                                    Expr *SizeExpr,
                                    unsigned IndexTypeQuals,
                                    SourceRange BracketsRange);

  /// Build a new incomplete array type given the element type, size
  /// modifier, and index type qualifiers.
  ///
  /// By default, performs semantic analysis when building the array type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildIncompleteArrayType(QualType ElementType,
                                      ArrayType::ArraySizeModifier SizeMod,
                                      unsigned IndexTypeQuals,
                                      SourceRange BracketsRange);

  /// Build a new variable-length array type given the element type,
  /// size modifier, size expression, and index type qualifiers.
  ///
  /// By default, performs semantic analysis when building the array type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildVariableArrayType(QualType ElementType,
                                    ArrayType::ArraySizeModifier SizeMod,
                                    Expr *SizeExpr,
                                    unsigned IndexTypeQuals,
                                    SourceRange BracketsRange);

  /// Build a new dependent-sized array type given the element type,
  /// size modifier, size expression, and index type qualifiers.
  ///
  /// By default, performs semantic analysis when building the array type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildDependentSizedArrayType(QualType ElementType,
                                          ArrayType::ArraySizeModifier SizeMod,
                                          Expr *SizeExpr,
                                          unsigned IndexTypeQuals,
                                          SourceRange BracketsRange);

  /// Build a new vector type given the element type and
  /// number of elements.
  ///
  /// By default, performs semantic analysis when building the vector type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildVectorType(QualType ElementType, unsigned NumElements,
                             VectorType::VectorKind VecKind);

  /// Build a new potentially dependently-sized extended vector type
  /// given the element type and number of elements.
  ///
  /// By default, performs semantic analysis when building the vector type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildDependentVectorType(QualType ElementType, Expr *SizeExpr,
                                           SourceLocation AttributeLoc,
                                           VectorType::VectorKind);

  /// Build a new extended vector type given the element type and
  /// number of elements.
  ///
  /// By default, performs semantic analysis when building the vector type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildExtVectorType(QualType ElementType, unsigned NumElements,
                                SourceLocation AttributeLoc);

  /// Build a new potentially dependently-sized extended vector type
  /// given the element type and number of elements.
  ///
  /// By default, performs semantic analysis when building the vector type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildDependentSizedExtVectorType(QualType ElementType,
                                              Expr *SizeExpr,
                                              SourceLocation AttributeLoc);

  /// Build a new DependentAddressSpaceType or return the pointee
  /// type variable with the correct address space (retrieved from
  /// AddrSpaceExpr) applied to it. The former will be returned in cases
  /// where the address space remains dependent.
  ///
  /// By default, performs semantic analysis when building the type with address
  /// space applied. Subclasses may override this routine to provide different
  /// behavior.
  QualType RebuildDependentAddressSpaceType(QualType PointeeType,
                                            Expr *AddrSpaceExpr,
                                            SourceLocation AttributeLoc);

  /// Build a new function type.
  ///
  /// By default, performs semantic analysis when building the function type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildFunctionProtoType(QualType T,
                                    MutableArrayRef<QualType> ParamTypes,
                                    const FunctionProtoType::ExtProtoInfo &EPI);

  /// Build a new unprototyped function type.
  QualType RebuildFunctionNoProtoType(QualType ResultType);

  /// Rebuild an unresolved typename type, given the decl that
  /// the UnresolvedUsingTypenameDecl was transformed to.
  QualType RebuildUnresolvedUsingType(SourceLocation NameLoc, Decl *D);

  /// Build a new typedef type.
  QualType RebuildTypedefType(TypedefNameDecl *Typedef) {
    return SemaRef.Context.getTypeDeclType(Typedef);
  }

  /// Build a new MacroDefined type.
  QualType RebuildMacroQualifiedType(QualType T,
                                     const IdentifierInfo *MacroII) {
    return SemaRef.Context.getMacroQualifiedType(T, MacroII);
  }

  /// Build a new class/struct/union type.
  QualType RebuildRecordType(RecordDecl *Record) {
    return SemaRef.Context.getTypeDeclType(Record);
  }

  /// Build a new Enum type.
  QualType RebuildEnumType(EnumDecl *Enum) {
    return SemaRef.Context.getTypeDeclType(Enum);
  }

  /// Build a new typeof(expr) type.
  ///
  /// By default, performs semantic analysis when building the typeof type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildTypeOfExprType(Expr *Underlying, SourceLocation Loc);

  /// Build a new typeof(type) type.
  ///
  /// By default, builds a new TypeOfType with the given underlying type.
  QualType RebuildTypeOfType(QualType Underlying);

  /// Build a new unary transform type.
  QualType RebuildUnaryTransformType(QualType BaseType,
                                     UnaryTransformType::UTTKind UKind,
                                     SourceLocation Loc);

  /// Build a new C++11 decltype type.
  ///
  /// By default, performs semantic analysis when building the decltype type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildDecltypeType(Expr *Underlying, SourceLocation Loc);

  /// Build a new C++11 auto type.
  ///
  /// By default, builds a new AutoType with the given deduced type.
  QualType RebuildAutoType(QualType Deduced, AutoTypeKeyword Keyword) {
    // Note, IsDependent is always false here: we implicitly convert an 'auto'
    // which has been deduced to a dependent type into an undeduced 'auto', so
    // that we'll retry deduction after the transformation.
    return SemaRef.Context.getAutoType(Deduced, Keyword,
                                       /*IsDependent*/ false);
  }

  /// By default, builds a new DeducedTemplateSpecializationType with the given
  /// deduced type.
  QualType RebuildDeducedTemplateSpecializationType(TemplateName Template,
      QualType Deduced) {
    return SemaRef.Context.getDeducedTemplateSpecializationType(
        Template, Deduced, /*IsDependent*/ false);
  }

  /// Build a new template specialization type.
  ///
  /// By default, performs semantic analysis when building the template
  /// specialization type. Subclasses may override this routine to provide
  /// different behavior.
  QualType RebuildTemplateSpecializationType(TemplateName Template,
                                             SourceLocation TemplateLoc,
                                             TemplateArgumentListInfo &Args);

  /// Build a new parenthesized type.
  ///
  /// By default, builds a new ParenType type from the inner type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildParenType(QualType InnerType) {
    return SemaRef.BuildParenType(InnerType);
  }

  /// Build a new qualified name type.
  ///
  /// By default, builds a new ElaboratedType type from the keyword,
  /// the nested-name-specifier and the named type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildElaboratedType(SourceLocation KeywordLoc,
                                 ElaboratedTypeKeyword Keyword,
                                 NestedNameSpecifierLoc QualifierLoc,
                                 QualType Named) {
    return SemaRef.Context.getElaboratedType(Keyword,
                                         QualifierLoc.getNestedNameSpecifier(),
                                             Named);
  }

  /// Build a new typename type that refers to a template-id.
  ///
  /// By default, builds a new DependentNameType type from the
  /// nested-name-specifier and the given type. Subclasses may override
  /// this routine to provide different behavior.
  QualType RebuildDependentTemplateSpecializationType(
                                          ElaboratedTypeKeyword Keyword,
                                          NestedNameSpecifierLoc QualifierLoc,
                                          SourceLocation TemplateKWLoc,
                                          const IdentifierInfo *Name,
                                          SourceLocation NameLoc,
                                          TemplateArgumentListInfo &Args,
                                          bool AllowInjectedClassName) {
    // Rebuild the template name.
    // TODO: avoid TemplateName abstraction
    CXXScopeSpec SS;
    SS.Adopt(QualifierLoc);
    TemplateName InstName = getDerived().RebuildTemplateName(
        SS, TemplateKWLoc, *Name, NameLoc, QualType(), nullptr,
        AllowInjectedClassName);

    if (InstName.isNull())
      return QualType();

    // If it's still dependent, make a dependent specialization.
    if (InstName.getAsDependentTemplateName())
      return SemaRef.Context.getDependentTemplateSpecializationType(Keyword,
                                          QualifierLoc.getNestedNameSpecifier(),
                                                                    Name,
                                                                    Args);

    // Otherwise, make an elaborated type wrapping a non-dependent
    // specialization.
    QualType T =
    getDerived().RebuildTemplateSpecializationType(InstName, NameLoc, Args);
    if (T.isNull()) return QualType();

    if (Keyword == ETK_None && QualifierLoc.getNestedNameSpecifier() == nullptr)
      return T;

    return SemaRef.Context.getElaboratedType(Keyword,
                                       QualifierLoc.getNestedNameSpecifier(),
                                             T);
  }

  /// Build a new typename type that refers to an identifier.
  ///
  /// By default, performs semantic analysis when building the typename type
  /// (or elaborated type). Subclasses may override this routine to provide
  /// different behavior.
  QualType RebuildDependentNameType(ElaboratedTypeKeyword Keyword,
                                    SourceLocation KeywordLoc,
                                    NestedNameSpecifierLoc QualifierLoc,
                                    const IdentifierInfo *Id,
                                    SourceLocation IdLoc,
                                    bool DeducedTSTContext) {
    CXXScopeSpec SS;
    SS.Adopt(QualifierLoc);

    if (QualifierLoc.getNestedNameSpecifier()->isDependent()) {
      // If the name is still dependent, just build a new dependent name type.
      if (!SemaRef.computeDeclContext(SS))
        return SemaRef.Context.getDependentNameType(Keyword,
                                          QualifierLoc.getNestedNameSpecifier(),
                                                    Id);
    }

    if (Keyword == ETK_None || Keyword == ETK_Typename) {
      QualType T = SemaRef.CheckTypenameType(Keyword, KeywordLoc, QualifierLoc,
                                             *Id, IdLoc);
      // If a dependent name resolves to a deduced template specialization type,
      // check that we're in one of the syntactic contexts permitting it.
      if (!DeducedTSTContext) {
        if (auto *Deduced = dyn_cast_or_null<DeducedTemplateSpecializationType>(
                T.isNull() ? nullptr : T->getContainedDeducedType())) {
          SemaRef.Diag(IdLoc, diag::err_dependent_deduced_tst)
            << (int)SemaRef.getTemplateNameKindForDiagnostics(
                   Deduced->getTemplateName())
            << QualType(QualifierLoc.getNestedNameSpecifier()->getAsType(), 0);
          if (auto *TD = Deduced->getTemplateName().getAsTemplateDecl())
            SemaRef.Diag(TD->getLocation(), diag::note_template_decl_here);
          return QualType();
        }
      }
      return T;
    }

    TagTypeKind Kind = TypeWithKeyword::getTagTypeKindForKeyword(Keyword);

    // We had a dependent elaborated-type-specifier that has been transformed
    // into a non-dependent elaborated-type-specifier. Find the tag we're
    // referring to.
    LookupResult Result(SemaRef, Id, IdLoc, Sema::LookupTagName);
    DeclContext *DC = SemaRef.computeDeclContext(SS, false);
    if (!DC)
      return QualType();

    if (SemaRef.RequireCompleteDeclContext(SS, DC))
      return QualType();

    TagDecl *Tag = nullptr;
    SemaRef.LookupQualifiedName(Result, DC);
    switch (Result.getResultKind()) {
      case LookupResult::NotFound:
      case LookupResult::NotFoundInCurrentInstantiation:
        break;

      case LookupResult::Found:
        Tag = Result.getAsSingle<TagDecl>();
        break;

      case LookupResult::FoundOverloaded:
      case LookupResult::FoundUnresolvedValue:
        llvm_unreachable("Tag lookup cannot find non-tags");

      case LookupResult::Ambiguous:
        // Let the LookupResult structure handle ambiguities.
        return QualType();
    }

    if (!Tag) {
      // Check where the name exists but isn't a tag type and use that to emit
      // better diagnostics.
      LookupResult Result(SemaRef, Id, IdLoc, Sema::LookupTagName);
      SemaRef.LookupQualifiedName(Result, DC);
      switch (Result.getResultKind()) {
        case LookupResult::Found:
        case LookupResult::FoundOverloaded:
        case LookupResult::FoundUnresolvedValue: {
          NamedDecl *SomeDecl = Result.getRepresentativeDecl();
          Sema::NonTagKind NTK = SemaRef.getNonTagTypeDeclKind(SomeDecl, Kind);
          SemaRef.Diag(IdLoc, diag::err_tag_reference_non_tag) << SomeDecl
                                                               << NTK << Kind;
          SemaRef.Diag(SomeDecl->getLocation(), diag::note_declared_at);
          break;
        }
        default:
          SemaRef.Diag(IdLoc, diag::err_not_tag_in_scope)
              << Kind << Id << DC << QualifierLoc.getSourceRange();
          break;
      }
      return QualType();
    }

    if (!SemaRef.isAcceptableTagRedeclaration(Tag, Kind, /*isDefinition*/false,
                                              IdLoc, Id)) {
      SemaRef.Diag(KeywordLoc, diag::err_use_with_wrong_tag) << Id;
      SemaRef.Diag(Tag->getLocation(), diag::note_previous_use);
      return QualType();
    }

    // Build the elaborated-type-specifier type.
    QualType T = SemaRef.Context.getTypeDeclType(Tag);
    return SemaRef.Context.getElaboratedType(Keyword,
                                         QualifierLoc.getNestedNameSpecifier(),
                                             T);
  }

  /// Build a new pack expansion type.
  ///
  /// By default, builds a new PackExpansionType type from the given pattern.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildPackExpansionType(QualType Pattern,
                                    SourceRange PatternRange,
                                    SourceLocation EllipsisLoc,
                                    Optional<unsigned> NumExpansions) {
    return getSema().CheckPackExpansion(Pattern, PatternRange, EllipsisLoc,
                                        NumExpansions);
  }

  /// Build a new atomic type given its value type.
  ///
  /// By default, performs semantic analysis when building the atomic type.
  /// Subclasses may override this routine to provide different behavior.
  QualType RebuildAtomicType(QualType ValueType, SourceLocation KWLoc);

  /// Build a new pipe type given its value type.
  QualType RebuildPipeType(QualType ValueType, SourceLocation KWLoc,
                           bool isReadPipe);

  /// Build a new template name given a nested name specifier, a flag
  /// indicating whether the "template" keyword was provided, and the template
  /// that the template name refers to.
  ///
  /// By default, builds the new template name directly. Subclasses may override
  /// this routine to provide different behavior.
  TemplateName RebuildTemplateName(CXXScopeSpec &SS,
                                   bool TemplateKW,
                                   TemplateDecl *Template);

  /// Build a new template name given a nested name specifier and the
  /// name that is referred to as a template.
  ///
  /// By default, performs semantic analysis to determine whether the name can
  /// be resolved to a specific template, then builds the appropriate kind of
  /// template name. Subclasses may override this routine to provide different
  /// behavior.
  TemplateName RebuildTemplateName(CXXScopeSpec &SS,
                                   SourceLocation TemplateKWLoc,
                                   const IdentifierInfo &Name,
                                   SourceLocation NameLoc, QualType ObjectType,
                                   NamedDecl *FirstQualifierInScope,
                                   bool AllowInjectedClassName);

  /// Build a new template name given a nested name specifier and the
  /// overloaded operator name that is referred to as a template.
  ///
  /// By default, performs semantic analysis to determine whether the name can
  /// be resolved to a specific template, then builds the appropriate kind of
  /// template name. Subclasses may override this routine to provide different
  /// behavior.
  TemplateName RebuildTemplateName(CXXScopeSpec &SS,
                                   SourceLocation TemplateKWLoc,
                                   OverloadedOperatorKind Operator,
                                   SourceLocation NameLoc, QualType ObjectType,
                                   bool AllowInjectedClassName);

  /// Build a new template name given a template template parameter pack
  /// and the
  ///
  /// By default, performs semantic analysis to determine whether the name can
  /// be resolved to a specific template, then builds the appropriate kind of
  /// template name. Subclasses may override this routine to provide different
  /// behavior.
  TemplateName RebuildTemplateName(TemplateTemplateParmDecl *Param,
                                   const TemplateArgument &ArgPack) {
    return getSema().Context.getSubstTemplateTemplateParmPack(Param, ArgPack);
  }

  /// Build a new compound statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildCompoundStmt(SourceLocation LBraceLoc,
                                       MultiStmtArg Statements,
                                       SourceLocation RBraceLoc,
                                       bool IsStmtExpr) {
    return getSema().ActOnCompoundStmt(LBraceLoc, RBraceLoc, Statements,
                                       IsStmtExpr);
  }

  /// Build a new case statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildCaseStmt(SourceLocation CaseLoc,
                                   Expr *LHS,
                                   SourceLocation EllipsisLoc,
                                   Expr *RHS,
                                   SourceLocation ColonLoc) {
    return getSema().ActOnCaseStmt(CaseLoc, LHS, EllipsisLoc, RHS,
                                   ColonLoc);
  }

  /// Attach the body to a new case statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildCaseStmtBody(Stmt *S, Stmt *Body) {
    getSema().ActOnCaseStmtBody(S, Body);
    return S;
  }

  /// Build a new default statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildDefaultStmt(SourceLocation DefaultLoc,
                                      SourceLocation ColonLoc,
                                      Stmt *SubStmt) {
    return getSema().ActOnDefaultStmt(DefaultLoc, ColonLoc, SubStmt,
                                      /*CurScope=*/nullptr);
  }

  /// Build a new label statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildLabelStmt(SourceLocation IdentLoc, LabelDecl *L,
                              SourceLocation ColonLoc, Stmt *SubStmt) {
    return SemaRef.ActOnLabelStmt(IdentLoc, L, ColonLoc, SubStmt);
  }

  /// Build a new label statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildAttributedStmt(SourceLocation AttrLoc,
                                   ArrayRef<const Attr*> Attrs,
                                   Stmt *SubStmt) {
    return SemaRef.ActOnAttributedStmt(AttrLoc, Attrs, SubStmt);
  }

  /// Build a new "if" statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildIfStmt(SourceLocation IfLoc, bool IsConstexpr,
                           Sema::ConditionResult Cond, Stmt *Init, Stmt *Then,
                           SourceLocation ElseLoc, Stmt *Else) {
    return getSema().ActOnIfStmt(IfLoc, IsConstexpr, Init, Cond, Then,
                                 ElseLoc, Else);
  }

  /// Start building a new switch statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildSwitchStmtStart(SourceLocation SwitchLoc, Stmt *Init,
                                    Sema::ConditionResult Cond) {
    return getSema().ActOnStartOfSwitchStmt(SwitchLoc, Init, Cond);
  }

  /// Attach the body to the switch statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildSwitchStmtBody(SourceLocation SwitchLoc,
                                   Stmt *Switch, Stmt *Body) {
    return getSema().ActOnFinishSwitchStmt(SwitchLoc, Switch, Body);
  }

  /// Build a new while statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildWhileStmt(SourceLocation WhileLoc,
                              Sema::ConditionResult Cond, Stmt *Body) {
    return getSema().ActOnWhileStmt(WhileLoc, Cond, Body);
  }

  /// Build a new do-while statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildDoStmt(SourceLocation DoLoc, Stmt *Body,
                           SourceLocation WhileLoc, SourceLocation LParenLoc,
                           Expr *Cond, SourceLocation RParenLoc) {
    return getSema().ActOnDoStmt(DoLoc, Body, WhileLoc, LParenLoc,
                                 Cond, RParenLoc);
  }

  /// Build a new for statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildForStmt(SourceLocation ForLoc, SourceLocation LParenLoc,
                            Stmt *Init, Sema::ConditionResult Cond,
                            Sema::FullExprArg Inc, SourceLocation RParenLoc,
                            Stmt *Body) {
    return getSema().ActOnForStmt(ForLoc, LParenLoc, Init, Cond,
                                  Inc, RParenLoc, Body);
  }

  /// Build a new goto statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildGotoStmt(SourceLocation GotoLoc, SourceLocation LabelLoc,
                             LabelDecl *Label) {
    return getSema().ActOnGotoStmt(GotoLoc, LabelLoc, Label);
  }

  /// Build a new indirect goto statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildIndirectGotoStmt(SourceLocation GotoLoc,
                                     SourceLocation StarLoc,
                                     Expr *Target) {
    return getSema().ActOnIndirectGotoStmt(GotoLoc, StarLoc, Target);
  }

  /// Build a new return statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildReturnStmt(SourceLocation ReturnLoc, Expr *Result) {
    return getSema().BuildReturnStmt(ReturnLoc, Result);
  }

  /// Build a new declaration statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildDeclStmt(MutableArrayRef<Decl *> Decls,
                             SourceLocation StartLoc, SourceLocation EndLoc) {
    Sema::DeclGroupPtrTy DG = getSema().BuildDeclaratorGroup(Decls);
    return getSema().ActOnDeclStmt(DG, StartLoc, EndLoc);
  }

  /// Build a new inline asm statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildGCCAsmStmt(SourceLocation AsmLoc, bool IsSimple,
                               bool IsVolatile, unsigned NumOutputs,
                               unsigned NumInputs, IdentifierInfo **Names,
                               MultiExprArg Constraints, MultiExprArg Exprs,
                               Expr *AsmString, MultiExprArg Clobbers,
                               unsigned NumLabels,
                               SourceLocation RParenLoc) {
    return getSema().ActOnGCCAsmStmt(AsmLoc, IsSimple, IsVolatile, NumOutputs,
                                     NumInputs, Names, Constraints, Exprs,
                                     AsmString, Clobbers, NumLabels, RParenLoc);
  }

  /// Build a new MS style inline asm statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildMSAsmStmt(SourceLocation AsmLoc, SourceLocation LBraceLoc,
                              ArrayRef<Token> AsmToks,
                              StringRef AsmString,
                              unsigned NumOutputs, unsigned NumInputs,
                              ArrayRef<StringRef> Constraints,
                              ArrayRef<StringRef> Clobbers,
                              ArrayRef<Expr*> Exprs,
                              SourceLocation EndLoc) {
    return getSema().ActOnMSAsmStmt(AsmLoc, LBraceLoc, AsmToks, AsmString,
                                    NumOutputs, NumInputs,
                                    Constraints, Clobbers, Exprs, EndLoc);
  }

  /// Build a new co_return statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildCoreturnStmt(SourceLocation CoreturnLoc, Expr *Result,
                                 bool IsImplicit) {
    return getSema().BuildCoreturnStmt(CoreturnLoc, Result, IsImplicit);
  }

  /// Build a new co_await expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCoawaitExpr(SourceLocation CoawaitLoc, Expr *Result,
                                bool IsImplicit) {
    return getSema().BuildResolvedCoawaitExpr(CoawaitLoc, Result, IsImplicit);
  }

  /// Build a new co_await expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildDependentCoawaitExpr(SourceLocation CoawaitLoc,
                                         Expr *Result,
                                         UnresolvedLookupExpr *Lookup) {
    return getSema().BuildUnresolvedCoawaitExpr(CoawaitLoc, Result, Lookup);
  }

  /// Build a new co_yield expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCoyieldExpr(SourceLocation CoyieldLoc, Expr *Result) {
    return getSema().BuildCoyieldExpr(CoyieldLoc, Result);
  }

  StmtResult RebuildCoroutineBodyStmt(CoroutineBodyStmt::CtorArgs Args) {
    return getSema().BuildCoroutineBodyStmt(Args);
  }

  /// Build a new Objective-C \@try statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildObjCAtTryStmt(SourceLocation AtLoc,
                                        Stmt *TryBody,
                                        MultiStmtArg CatchStmts,
                                        Stmt *Finally) {
    return getSema().ActOnObjCAtTryStmt(AtLoc, TryBody, CatchStmts,
                                        Finally);
  }

  /// Rebuild an Objective-C exception declaration.
  ///
  /// By default, performs semantic analysis to build the new declaration.
  /// Subclasses may override this routine to provide different behavior.
  VarDecl *RebuildObjCExceptionDecl(VarDecl *ExceptionDecl,
                                    TypeSourceInfo *TInfo, QualType T) {
    return getSema().BuildObjCExceptionDecl(TInfo, T,
                                            ExceptionDecl->getInnerLocStart(),
                                            ExceptionDecl->getLocation(),
                                            ExceptionDecl->getIdentifier());
  }

  /// Build a new Objective-C \@catch statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildObjCAtCatchStmt(SourceLocation AtLoc,
                                          SourceLocation RParenLoc,
                                          VarDecl *Var,
                                          Stmt *Body) {
    return getSema().ActOnObjCAtCatchStmt(AtLoc, RParenLoc,
                                          Var, Body);
  }

  /// Build a new Objective-C \@finally statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildObjCAtFinallyStmt(SourceLocation AtLoc,
                                            Stmt *Body) {
    return getSema().ActOnObjCAtFinallyStmt(AtLoc, Body);
  }

  /// Build a new Objective-C \@throw statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildObjCAtThrowStmt(SourceLocation AtLoc,
                                          Expr *Operand) {
    return getSema().BuildObjCAtThrowStmt(AtLoc, Operand);
  }

  /// Build a new OpenMP executable directive.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildOMPExecutableDirective(OpenMPDirectiveKind Kind,
                                           DeclarationNameInfo DirName,
                                           OpenMPDirectiveKind CancelRegion,
                                           ArrayRef<OMPClause *> Clauses,
                                           Stmt *AStmt, SourceLocation StartLoc,
                                           SourceLocation EndLoc) {
    return getSema().ActOnOpenMPExecutableDirective(
        Kind, DirName, CancelRegion, Clauses, AStmt, StartLoc, EndLoc);
  }

  /// Build a new OpenMP 'if' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPIfClause(OpenMPDirectiveKind NameModifier,
                                Expr *Condition, SourceLocation StartLoc,
                                SourceLocation LParenLoc,
                                SourceLocation NameModifierLoc,
                                SourceLocation ColonLoc,
                                SourceLocation EndLoc) {
    return getSema().ActOnOpenMPIfClause(NameModifier, Condition, StartLoc,
                                         LParenLoc, NameModifierLoc, ColonLoc,
                                         EndLoc);
  }

  /// Build a new OpenMP 'final' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPFinalClause(Expr *Condition, SourceLocation StartLoc,
                                   SourceLocation LParenLoc,
                                   SourceLocation EndLoc) {
    return getSema().ActOnOpenMPFinalClause(Condition, StartLoc, LParenLoc,
                                            EndLoc);
  }

  /// Build a new OpenMP 'num_threads' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPNumThreadsClause(Expr *NumThreads,
                                        SourceLocation StartLoc,
                                        SourceLocation LParenLoc,
                                        SourceLocation EndLoc) {
    return getSema().ActOnOpenMPNumThreadsClause(NumThreads, StartLoc,
                                                 LParenLoc, EndLoc);
  }

  /// Build a new OpenMP 'safelen' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPSafelenClause(Expr *Len, SourceLocation StartLoc,
                                     SourceLocation LParenLoc,
                                     SourceLocation EndLoc) {
    return getSema().ActOnOpenMPSafelenClause(Len, StartLoc, LParenLoc, EndLoc);
  }

  /// Build a new OpenMP 'simdlen' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPSimdlenClause(Expr *Len, SourceLocation StartLoc,
                                     SourceLocation LParenLoc,
                                     SourceLocation EndLoc) {
    return getSema().ActOnOpenMPSimdlenClause(Len, StartLoc, LParenLoc, EndLoc);
  }

  /// Build a new OpenMP 'allocator' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPAllocatorClause(Expr *A, SourceLocation StartLoc,
                                       SourceLocation LParenLoc,
                                       SourceLocation EndLoc) {
    return getSema().ActOnOpenMPAllocatorClause(A, StartLoc, LParenLoc, EndLoc);
  }

  /// Build a new OpenMP 'collapse' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPCollapseClause(Expr *Num, SourceLocation StartLoc,
                                      SourceLocation LParenLoc,
                                      SourceLocation EndLoc) {
    return getSema().ActOnOpenMPCollapseClause(Num, StartLoc, LParenLoc,
                                               EndLoc);
  }

  /// Build a new OpenMP 'default' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPDefaultClause(OpenMPDefaultClauseKind Kind,
                                     SourceLocation KindKwLoc,
                                     SourceLocation StartLoc,
                                     SourceLocation LParenLoc,
                                     SourceLocation EndLoc) {
    return getSema().ActOnOpenMPDefaultClause(Kind, KindKwLoc,
                                              StartLoc, LParenLoc, EndLoc);
  }

  /// Build a new OpenMP 'proc_bind' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPProcBindClause(OpenMPProcBindClauseKind Kind,
                                      SourceLocation KindKwLoc,
                                      SourceLocation StartLoc,
                                      SourceLocation LParenLoc,
                                      SourceLocation EndLoc) {
    return getSema().ActOnOpenMPProcBindClause(Kind, KindKwLoc,
                                               StartLoc, LParenLoc, EndLoc);
  }

  /// Build a new OpenMP 'schedule' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPScheduleClause(
      OpenMPScheduleClauseModifier M1, OpenMPScheduleClauseModifier M2,
      OpenMPScheduleClauseKind Kind, Expr *ChunkSize, SourceLocation StartLoc,
      SourceLocation LParenLoc, SourceLocation M1Loc, SourceLocation M2Loc,
      SourceLocation KindLoc, SourceLocation CommaLoc, SourceLocation EndLoc) {
    return getSema().ActOnOpenMPScheduleClause(
        M1, M2, Kind, ChunkSize, StartLoc, LParenLoc, M1Loc, M2Loc, KindLoc,
        CommaLoc, EndLoc);
  }

  /// Build a new OpenMP 'ordered' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPOrderedClause(SourceLocation StartLoc,
                                     SourceLocation EndLoc,
                                     SourceLocation LParenLoc, Expr *Num) {
    return getSema().ActOnOpenMPOrderedClause(StartLoc, EndLoc, LParenLoc, Num);
  }

  /// Build a new OpenMP 'private' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPPrivateClause(ArrayRef<Expr *> VarList,
                                     SourceLocation StartLoc,
                                     SourceLocation LParenLoc,
                                     SourceLocation EndLoc) {
    return getSema().ActOnOpenMPPrivateClause(VarList, StartLoc, LParenLoc,
                                              EndLoc);
  }

  /// Build a new OpenMP 'firstprivate' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPFirstprivateClause(ArrayRef<Expr *> VarList,
                                          SourceLocation StartLoc,
                                          SourceLocation LParenLoc,
                                          SourceLocation EndLoc) {
    return getSema().ActOnOpenMPFirstprivateClause(VarList, StartLoc, LParenLoc,
                                                   EndLoc);
  }

  /// Build a new OpenMP 'lastprivate' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPLastprivateClause(ArrayRef<Expr *> VarList,
                                         SourceLocation StartLoc,
                                         SourceLocation LParenLoc,
                                         SourceLocation EndLoc) {
    return getSema().ActOnOpenMPLastprivateClause(VarList, StartLoc, LParenLoc,
                                                  EndLoc);
  }

  /// Build a new OpenMP 'shared' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPSharedClause(ArrayRef<Expr *> VarList,
                                    SourceLocation StartLoc,
                                    SourceLocation LParenLoc,
                                    SourceLocation EndLoc) {
    return getSema().ActOnOpenMPSharedClause(VarList, StartLoc, LParenLoc,
                                             EndLoc);
  }

  /// Build a new OpenMP 'reduction' clause.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPReductionClause(ArrayRef<Expr *> VarList,
                                       SourceLocation StartLoc,
                                       SourceLocation LParenLoc,
                                       SourceLocation ColonLoc,
                                       SourceLocation EndLoc,
                                       CXXScopeSpec &ReductionIdScopeSpec,
                                       const DeclarationNameInfo &ReductionId,
                                       ArrayRef<Expr *> UnresolvedReductions) {
    return getSema().ActOnOpenMPReductionClause(
        VarList, StartLoc, LParenLoc, ColonLoc, EndLoc, ReductionIdScopeSpec,
        ReductionId, UnresolvedReductions);
  }

  /// Build a new OpenMP 'task_reduction' clause.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPTaskReductionClause(
      ArrayRef<Expr *> VarList, SourceLocation StartLoc,
      SourceLocation LParenLoc, SourceLocation ColonLoc, SourceLocation EndLoc,
      CXXScopeSpec &ReductionIdScopeSpec,
      const DeclarationNameInfo &ReductionId,
      ArrayRef<Expr *> UnresolvedReductions) {
    return getSema().ActOnOpenMPTaskReductionClause(
        VarList, StartLoc, LParenLoc, ColonLoc, EndLoc, ReductionIdScopeSpec,
        ReductionId, UnresolvedReductions);
  }

  /// Build a new OpenMP 'in_reduction' clause.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *
  RebuildOMPInReductionClause(ArrayRef<Expr *> VarList, SourceLocation StartLoc,
                              SourceLocation LParenLoc, SourceLocation ColonLoc,
                              SourceLocation EndLoc,
                              CXXScopeSpec &ReductionIdScopeSpec,
                              const DeclarationNameInfo &ReductionId,
                              ArrayRef<Expr *> UnresolvedReductions) {
    return getSema().ActOnOpenMPInReductionClause(
        VarList, StartLoc, LParenLoc, ColonLoc, EndLoc, ReductionIdScopeSpec,
        ReductionId, UnresolvedReductions);
  }

  /// Build a new OpenMP 'linear' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPLinearClause(ArrayRef<Expr *> VarList, Expr *Step,
                                    SourceLocation StartLoc,
                                    SourceLocation LParenLoc,
                                    OpenMPLinearClauseKind Modifier,
                                    SourceLocation ModifierLoc,
                                    SourceLocation ColonLoc,
                                    SourceLocation EndLoc) {
    return getSema().ActOnOpenMPLinearClause(VarList, Step, StartLoc, LParenLoc,
                                             Modifier, ModifierLoc, ColonLoc,
                                             EndLoc);
  }

  /// Build a new OpenMP 'aligned' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPAlignedClause(ArrayRef<Expr *> VarList, Expr *Alignment,
                                     SourceLocation StartLoc,
                                     SourceLocation LParenLoc,
                                     SourceLocation ColonLoc,
                                     SourceLocation EndLoc) {
    return getSema().ActOnOpenMPAlignedClause(VarList, Alignment, StartLoc,
                                              LParenLoc, ColonLoc, EndLoc);
  }

  /// Build a new OpenMP 'copyin' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPCopyinClause(ArrayRef<Expr *> VarList,
                                    SourceLocation StartLoc,
                                    SourceLocation LParenLoc,
                                    SourceLocation EndLoc) {
    return getSema().ActOnOpenMPCopyinClause(VarList, StartLoc, LParenLoc,
                                             EndLoc);
  }

  /// Build a new OpenMP 'copyprivate' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPCopyprivateClause(ArrayRef<Expr *> VarList,
                                         SourceLocation StartLoc,
                                         SourceLocation LParenLoc,
                                         SourceLocation EndLoc) {
    return getSema().ActOnOpenMPCopyprivateClause(VarList, StartLoc, LParenLoc,
                                                  EndLoc);
  }

  /// Build a new OpenMP 'flush' pseudo clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPFlushClause(ArrayRef<Expr *> VarList,
                                   SourceLocation StartLoc,
                                   SourceLocation LParenLoc,
                                   SourceLocation EndLoc) {
    return getSema().ActOnOpenMPFlushClause(VarList, StartLoc, LParenLoc,
                                            EndLoc);
  }

  /// Build a new OpenMP 'depend' pseudo clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *
  RebuildOMPDependClause(OpenMPDependClauseKind DepKind, SourceLocation DepLoc,
                         SourceLocation ColonLoc, ArrayRef<Expr *> VarList,
                         SourceLocation StartLoc, SourceLocation LParenLoc,
                         SourceLocation EndLoc) {
    return getSema().ActOnOpenMPDependClause(DepKind, DepLoc, ColonLoc, VarList,
                                             StartLoc, LParenLoc, EndLoc);
  }

  /// Build a new OpenMP 'device' clause.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPDeviceClause(Expr *Device, SourceLocation StartLoc,
                                    SourceLocation LParenLoc,
                                    SourceLocation EndLoc) {
    return getSema().ActOnOpenMPDeviceClause(Device, StartLoc, LParenLoc,
                                             EndLoc);
  }

  /// Build a new OpenMP 'map' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPMapClause(
      ArrayRef<OpenMPMapModifierKind> MapTypeModifiers,
      ArrayRef<SourceLocation> MapTypeModifiersLoc,
      CXXScopeSpec MapperIdScopeSpec, DeclarationNameInfo MapperId,
      OpenMPMapClauseKind MapType, bool IsMapTypeImplicit,
      SourceLocation MapLoc, SourceLocation ColonLoc, ArrayRef<Expr *> VarList,
      const OMPVarListLocTy &Locs, ArrayRef<Expr *> UnresolvedMappers) {
    return getSema().ActOnOpenMPMapClause(MapTypeModifiers, MapTypeModifiersLoc,
                                          MapperIdScopeSpec, MapperId, MapType,
                                          IsMapTypeImplicit, MapLoc, ColonLoc,
                                          VarList, Locs, UnresolvedMappers);
  }

  /// Build a new OpenMP 'allocate' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPAllocateClause(Expr *Allocate, ArrayRef<Expr *> VarList,
                                      SourceLocation StartLoc,
                                      SourceLocation LParenLoc,
                                      SourceLocation ColonLoc,
                                      SourceLocation EndLoc) {
    return getSema().ActOnOpenMPAllocateClause(Allocate, VarList, StartLoc,
                                               LParenLoc, ColonLoc, EndLoc);
  }

  /// Build a new OpenMP 'num_teams' clause.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPNumTeamsClause(Expr *NumTeams, SourceLocation StartLoc,
                                      SourceLocation LParenLoc,
                                      SourceLocation EndLoc) {
    return getSema().ActOnOpenMPNumTeamsClause(NumTeams, StartLoc, LParenLoc,
                                               EndLoc);
  }

  /// Build a new OpenMP 'thread_limit' clause.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPThreadLimitClause(Expr *ThreadLimit,
                                         SourceLocation StartLoc,
                                         SourceLocation LParenLoc,
                                         SourceLocation EndLoc) {
    return getSema().ActOnOpenMPThreadLimitClause(ThreadLimit, StartLoc,
                                                  LParenLoc, EndLoc);
  }

  /// Build a new OpenMP 'priority' clause.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPPriorityClause(Expr *Priority, SourceLocation StartLoc,
                                      SourceLocation LParenLoc,
                                      SourceLocation EndLoc) {
    return getSema().ActOnOpenMPPriorityClause(Priority, StartLoc, LParenLoc,
                                               EndLoc);
  }

  /// Build a new OpenMP 'grainsize' clause.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPGrainsizeClause(Expr *Grainsize, SourceLocation StartLoc,
                                       SourceLocation LParenLoc,
                                       SourceLocation EndLoc) {
    return getSema().ActOnOpenMPGrainsizeClause(Grainsize, StartLoc, LParenLoc,
                                                EndLoc);
  }

  /// Build a new OpenMP 'num_tasks' clause.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPNumTasksClause(Expr *NumTasks, SourceLocation StartLoc,
                                      SourceLocation LParenLoc,
                                      SourceLocation EndLoc) {
    return getSema().ActOnOpenMPNumTasksClause(NumTasks, StartLoc, LParenLoc,
                                               EndLoc);
  }

  /// Build a new OpenMP 'hint' clause.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPHintClause(Expr *Hint, SourceLocation StartLoc,
                                  SourceLocation LParenLoc,
                                  SourceLocation EndLoc) {
    return getSema().ActOnOpenMPHintClause(Hint, StartLoc, LParenLoc, EndLoc);
  }

  /// Build a new OpenMP 'dist_schedule' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *
  RebuildOMPDistScheduleClause(OpenMPDistScheduleClauseKind Kind,
                               Expr *ChunkSize, SourceLocation StartLoc,
                               SourceLocation LParenLoc, SourceLocation KindLoc,
                               SourceLocation CommaLoc, SourceLocation EndLoc) {
    return getSema().ActOnOpenMPDistScheduleClause(
        Kind, ChunkSize, StartLoc, LParenLoc, KindLoc, CommaLoc, EndLoc);
  }

  /// Build a new OpenMP 'to' clause.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPToClause(ArrayRef<Expr *> VarList,
                                CXXScopeSpec &MapperIdScopeSpec,
                                DeclarationNameInfo &MapperId,
                                const OMPVarListLocTy &Locs,
                                ArrayRef<Expr *> UnresolvedMappers) {
    return getSema().ActOnOpenMPToClause(VarList, MapperIdScopeSpec, MapperId,
                                         Locs, UnresolvedMappers);
  }

  /// Build a new OpenMP 'from' clause.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPFromClause(ArrayRef<Expr *> VarList,
                                  CXXScopeSpec &MapperIdScopeSpec,
                                  DeclarationNameInfo &MapperId,
                                  const OMPVarListLocTy &Locs,
                                  ArrayRef<Expr *> UnresolvedMappers) {
    return getSema().ActOnOpenMPFromClause(VarList, MapperIdScopeSpec, MapperId,
                                           Locs, UnresolvedMappers);
  }

  /// Build a new OpenMP 'use_device_ptr' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPUseDevicePtrClause(ArrayRef<Expr *> VarList,
                                          const OMPVarListLocTy &Locs) {
    return getSema().ActOnOpenMPUseDevicePtrClause(VarList, Locs);
  }

  /// Build a new OpenMP 'is_device_ptr' clause.
  ///
  /// By default, performs semantic analysis to build the new OpenMP clause.
  /// Subclasses may override this routine to provide different behavior.
  OMPClause *RebuildOMPIsDevicePtrClause(ArrayRef<Expr *> VarList,
                                         const OMPVarListLocTy &Locs) {
    return getSema().ActOnOpenMPIsDevicePtrClause(VarList, Locs);
  }

  /// Rebuild the operand to an Objective-C \@synchronized statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildObjCAtSynchronizedOperand(SourceLocation atLoc,
                                              Expr *object) {
    return getSema().ActOnObjCAtSynchronizedOperand(atLoc, object);
  }

  /// Build a new Objective-C \@synchronized statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildObjCAtSynchronizedStmt(SourceLocation AtLoc,
                                           Expr *Object, Stmt *Body) {
    return getSema().ActOnObjCAtSynchronizedStmt(AtLoc, Object, Body);
  }

  /// Build a new Objective-C \@autoreleasepool statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildObjCAutoreleasePoolStmt(SourceLocation AtLoc,
                                            Stmt *Body) {
    return getSema().ActOnObjCAutoreleasePoolStmt(AtLoc, Body);
  }

  /// Build a new Objective-C fast enumeration statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildObjCForCollectionStmt(SourceLocation ForLoc,
                                          Stmt *Element,
                                          Expr *Collection,
                                          SourceLocation RParenLoc,
                                          Stmt *Body) {
    StmtResult ForEachStmt = getSema().ActOnObjCForCollectionStmt(ForLoc,
                                                Element,
                                                Collection,
                                                RParenLoc);
    if (ForEachStmt.isInvalid())
      return StmtError();

    return getSema().FinishObjCForCollectionStmt(ForEachStmt.get(), Body);
  }

  /// Build a new C++ exception declaration.
  ///
  /// By default, performs semantic analysis to build the new decaration.
  /// Subclasses may override this routine to provide different behavior.
  VarDecl *RebuildExceptionDecl(VarDecl *ExceptionDecl,
                                TypeSourceInfo *Declarator,
                                SourceLocation StartLoc,
                                SourceLocation IdLoc,
                                IdentifierInfo *Id) {
    VarDecl *Var = getSema().BuildExceptionDeclaration(nullptr, Declarator,
                                                       StartLoc, IdLoc, Id);
    if (Var)
      getSema().CurContext->addDecl(Var);
    return Var;
  }

  /// Build a new C++ catch statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildCXXCatchStmt(SourceLocation CatchLoc,
                                 VarDecl *ExceptionDecl,
                                 Stmt *Handler) {
    return Owned(new (getSema().Context) CXXCatchStmt(CatchLoc, ExceptionDecl,
                                                      Handler));
  }

  /// Build a new C++ try statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildCXXTryStmt(SourceLocation TryLoc, Stmt *TryBlock,
                               ArrayRef<Stmt *> Handlers) {
    return getSema().ActOnCXXTryBlock(TryLoc, TryBlock, Handlers);
  }

  /// Build a new C++0x range-based for statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildCXXForRangeStmt(SourceLocation ForLoc,
                                    SourceLocation CoawaitLoc, Stmt *Init,
                                    SourceLocation ColonLoc, Stmt *Range,
                                    Stmt *Begin, Stmt *End, Expr *Cond,
                                    Expr *Inc, Stmt *LoopVar,
                                    SourceLocation RParenLoc) {
    // If we've just learned that the range is actually an Objective-C
    // collection, treat this as an Objective-C fast enumeration loop.
    if (DeclStmt *RangeStmt = dyn_cast<DeclStmt>(Range)) {
      if (RangeStmt->isSingleDecl()) {
        if (VarDecl *RangeVar = dyn_cast<VarDecl>(RangeStmt->getSingleDecl())) {
          if (RangeVar->isInvalidDecl())
            return StmtError();

          Expr *RangeExpr = RangeVar->getInit();
          if (!RangeExpr->isTypeDependent() &&
              RangeExpr->getType()->isObjCObjectPointerType()) {
            // FIXME: Support init-statements in Objective-C++20 ranged for
            // statement.
            if (Init) {
              return SemaRef.Diag(Init->getBeginLoc(),
                                  diag::err_objc_for_range_init_stmt)
                         << Init->getSourceRange();
            }
            return getSema().ActOnObjCForCollectionStmt(ForLoc, LoopVar,
                                                        RangeExpr, RParenLoc);
          }
        }
      }
    }

    return getSema().BuildCXXForRangeStmt(ForLoc, CoawaitLoc, Init, ColonLoc,
                                          Range, Begin, End, Cond, Inc, LoopVar,
                                          RParenLoc, Sema::BFRK_Rebuild);
  }

  /// Build a new C++0x range-based for statement.
  ///
  /// By default, performs semantic analysis to build the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult RebuildMSDependentExistsStmt(SourceLocation KeywordLoc,
                                          bool IsIfExists,
                                          NestedNameSpecifierLoc QualifierLoc,
                                          DeclarationNameInfo NameInfo,
                                          Stmt *Nested) {
    return getSema().BuildMSDependentExistsStmt(KeywordLoc, IsIfExists,
                                                QualifierLoc, NameInfo, Nested);
  }

  /// Attach body to a C++0x range-based for statement.
  ///
  /// By default, performs semantic analysis to finish the new statement.
  /// Subclasses may override this routine to provide different behavior.
  StmtResult FinishCXXForRangeStmt(Stmt *ForRange, Stmt *Body) {
    return getSema().FinishCXXForRangeStmt(ForRange, Body);
  }

  StmtResult RebuildSEHTryStmt(bool IsCXXTry, SourceLocation TryLoc,
                               Stmt *TryBlock, Stmt *Handler) {
    return getSema().ActOnSEHTryBlock(IsCXXTry, TryLoc, TryBlock, Handler);
  }

  StmtResult RebuildSEHExceptStmt(SourceLocation Loc, Expr *FilterExpr,
                                  Stmt *Block) {
    return getSema().ActOnSEHExceptBlock(Loc, FilterExpr, Block);
  }

  StmtResult RebuildSEHFinallyStmt(SourceLocation Loc, Stmt *Block) {
    return SEHFinallyStmt::Create(getSema().getASTContext(), Loc, Block);
  }

  /// Build a new predefined expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildPredefinedExpr(SourceLocation Loc,
                                   PredefinedExpr::IdentKind IK) {
    return getSema().BuildPredefinedExpr(Loc, IK);
  }

  /// Build a new expression that references a declaration.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildDeclarationNameExpr(const CXXScopeSpec &SS,
                                        LookupResult &R,
                                        bool RequiresADL) {
    return getSema().BuildDeclarationNameExpr(SS, R, RequiresADL);
  }


  /// Build a new expression that references a declaration.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildDeclRefExpr(NestedNameSpecifierLoc QualifierLoc,
                                ValueDecl *VD,
                                const DeclarationNameInfo &NameInfo,
                                NamedDecl *Found,
                                TemplateArgumentListInfo *TemplateArgs) {
    CXXScopeSpec SS;
    SS.Adopt(QualifierLoc);
    return getSema().BuildDeclarationNameExpr(SS, NameInfo, VD, Found,
                                              TemplateArgs);
  }

  /// Build a new expression in parentheses.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildParenExpr(Expr *SubExpr, SourceLocation LParen,
                                    SourceLocation RParen) {
    return getSema().ActOnParenExpr(LParen, RParen, SubExpr);
  }

  /// Build a new pseudo-destructor expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXPseudoDestructorExpr(Expr *Base,
                                            SourceLocation OperatorLoc,
                                            bool isArrow,
                                            CXXScopeSpec &SS,
                                            TypeSourceInfo *ScopeType,
                                            SourceLocation CCLoc,
                                            SourceLocation TildeLoc,
                                        PseudoDestructorTypeStorage Destroyed);

  /// Build a new unary operator expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildUnaryOperator(SourceLocation OpLoc,
                                        UnaryOperatorKind Opc,
                                        Expr *SubExpr) {
    return getSema().BuildUnaryOp(/*Scope=*/nullptr, OpLoc, Opc, SubExpr);
  }

  /// Build a new builtin offsetof expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildOffsetOfExpr(SourceLocation OperatorLoc,
                                 TypeSourceInfo *Type,
                                 ArrayRef<Sema::OffsetOfComponent> Components,
                                 SourceLocation RParenLoc) {
    return getSema().BuildBuiltinOffsetOf(OperatorLoc, Type, Components,
                                          RParenLoc);
  }

  /// Build a new sizeof, alignof or vec_step expression with a
  /// type argument.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildUnaryExprOrTypeTrait(TypeSourceInfo *TInfo,
                                         SourceLocation OpLoc,
                                         UnaryExprOrTypeTrait ExprKind,
                                         SourceRange R) {
    return getSema().CreateUnaryExprOrTypeTraitExpr(TInfo, OpLoc, ExprKind, R);
  }

  /// Build a new sizeof, alignof or vec step expression with an
  /// expression argument.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildUnaryExprOrTypeTrait(Expr *SubExpr, SourceLocation OpLoc,
                                         UnaryExprOrTypeTrait ExprKind,
                                         SourceRange R) {
    ExprResult Result
      = getSema().CreateUnaryExprOrTypeTraitExpr(SubExpr, OpLoc, ExprKind);
    if (Result.isInvalid())
      return ExprError();

    return Result;
  }

  /// Build a new array subscript expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildArraySubscriptExpr(Expr *LHS,
                                             SourceLocation LBracketLoc,
                                             Expr *RHS,
                                             SourceLocation RBracketLoc) {
    return getSema().ActOnArraySubscriptExpr(/*Scope=*/nullptr, LHS,
                                             LBracketLoc, RHS,
                                             RBracketLoc);
  }

  /// Build a new array section expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildOMPArraySectionExpr(Expr *Base, SourceLocation LBracketLoc,
                                        Expr *LowerBound,
                                        SourceLocation ColonLoc, Expr *Length,
                                        SourceLocation RBracketLoc) {
    return getSema().ActOnOMPArraySectionExpr(Base, LBracketLoc, LowerBound,
                                              ColonLoc, Length, RBracketLoc);
  }

  /// Build a new call expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCallExpr(Expr *Callee, SourceLocation LParenLoc,
                                   MultiExprArg Args,
                                   SourceLocation RParenLoc,
                                   Expr *ExecConfig = nullptr) {
    return getSema().BuildCallExpr(/*Scope=*/nullptr, Callee, LParenLoc, Args,
                                   RParenLoc, ExecConfig);
  }

  /// Build a new member access expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildMemberExpr(Expr *Base, SourceLocation OpLoc,
                               bool isArrow,
                               NestedNameSpecifierLoc QualifierLoc,
                               SourceLocation TemplateKWLoc,
                               const DeclarationNameInfo &MemberNameInfo,
                               ValueDecl *Member,
                               NamedDecl *FoundDecl,
                        const TemplateArgumentListInfo *ExplicitTemplateArgs,
                               NamedDecl *FirstQualifierInScope) {
    ExprResult BaseResult = getSema().PerformMemberExprBaseConversion(Base,
                                                                      isArrow);
    if (!Member->getDeclName()) {
      // We have a reference to an unnamed field.  This is always the
      // base of an anonymous struct/union member access, i.e. the
      // field is always of record type.
      assert(Member->getType()->isRecordType() &&
             "unnamed member not of record type?");

      BaseResult =
        getSema().PerformObjectMemberConversion(BaseResult.get(),
                                                QualifierLoc.getNestedNameSpecifier(),
                                                FoundDecl, Member);
      if (BaseResult.isInvalid())
        return ExprError();
      Base = BaseResult.get();

      CXXScopeSpec EmptySS;
      return getSema().BuildFieldReferenceExpr(
          Base, isArrow, OpLoc, EmptySS, cast<FieldDecl>(Member),
          DeclAccessPair::make(FoundDecl, FoundDecl->getAccess()), MemberNameInfo);
    }

    CXXScopeSpec SS;
    SS.Adopt(QualifierLoc);

    Base = BaseResult.get();
    QualType BaseType = Base->getType();

    if (isArrow && !BaseType->isPointerType())
      return ExprError();

    // FIXME: this involves duplicating earlier analysis in a lot of
    // cases; we should avoid this when possible.
    LookupResult R(getSema(), MemberNameInfo, Sema::LookupMemberName);
    R.addDecl(FoundDecl);
    R.resolveKind();

    return getSema().BuildMemberReferenceExpr(Base, BaseType, OpLoc, isArrow,
                                              SS, TemplateKWLoc,
                                              FirstQualifierInScope,
                                              R, ExplicitTemplateArgs,
                                              /*S*/nullptr);
  }

  /// Build a new binary operator expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildBinaryOperator(SourceLocation OpLoc,
                                         BinaryOperatorKind Opc,
                                         Expr *LHS, Expr *RHS) {
    return getSema().BuildBinOp(/*Scope=*/nullptr, OpLoc, Opc, LHS, RHS);
  }

  /// Build a new rewritten operator expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXRewrittenBinaryOperator(
      SourceLocation OpLoc, BinaryOperatorKind Opcode,
      const UnresolvedSetImpl &UnqualLookups, Expr *LHS, Expr *RHS) {
    return getSema().CreateOverloadedBinOp(OpLoc, Opcode, UnqualLookups, LHS,
                                           RHS, /*RequiresADL*/false);
  }

  /// Build a new conditional operator expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildConditionalOperator(Expr *Cond,
                                        SourceLocation QuestionLoc,
                                        Expr *LHS,
                                        SourceLocation ColonLoc,
                                        Expr *RHS) {
    return getSema().ActOnConditionalOp(QuestionLoc, ColonLoc, Cond,
                                        LHS, RHS);
  }

  /// Build a new C-style cast expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCStyleCastExpr(SourceLocation LParenLoc,
                                         TypeSourceInfo *TInfo,
                                         SourceLocation RParenLoc,
                                         Expr *SubExpr) {
    return getSema().BuildCStyleCastExpr(LParenLoc, TInfo, RParenLoc,
                                         SubExpr);
  }

  /// Build a new compound literal expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCompoundLiteralExpr(SourceLocation LParenLoc,
                                              TypeSourceInfo *TInfo,
                                              SourceLocation RParenLoc,
                                              Expr *Init) {
    return getSema().BuildCompoundLiteralExpr(LParenLoc, TInfo, RParenLoc,
                                              Init);
  }

  /// Build a new extended vector element access expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildExtVectorElementExpr(Expr *Base,
                                               SourceLocation OpLoc,
                                               SourceLocation AccessorLoc,
                                               IdentifierInfo &Accessor) {

    CXXScopeSpec SS;
    DeclarationNameInfo NameInfo(&Accessor, AccessorLoc);
    return getSema().BuildMemberReferenceExpr(Base, Base->getType(),
                                              OpLoc, /*IsArrow*/ false,
                                              SS, SourceLocation(),
                                              /*FirstQualifierInScope*/ nullptr,
                                              NameInfo,
                                              /* TemplateArgs */ nullptr,
                                              /*S*/ nullptr);
  }

  /// Build a new initializer list expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildInitList(SourceLocation LBraceLoc,
                             MultiExprArg Inits,
                             SourceLocation RBraceLoc) {
    return SemaRef.BuildInitList(LBraceLoc, Inits, RBraceLoc);
  }

  /// Build a new designated initializer expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildDesignatedInitExpr(Designation &Desig,
                                             MultiExprArg ArrayExprs,
                                             SourceLocation EqualOrColonLoc,
                                             bool GNUSyntax,
                                             Expr *Init) {
    ExprResult Result
      = SemaRef.ActOnDesignatedInitializer(Desig, EqualOrColonLoc, GNUSyntax,
                                           Init);
    if (Result.isInvalid())
      return ExprError();

    return Result;
  }

  /// Build a new value-initialized expression.
  ///
  /// By default, builds the implicit value initialization without performing
  /// any semantic analysis. Subclasses may override this routine to provide
  /// different behavior.
  ExprResult RebuildImplicitValueInitExpr(QualType T) {
    return new (SemaRef.Context) ImplicitValueInitExpr(T);
  }

  /// Build a new \c va_arg expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildVAArgExpr(SourceLocation BuiltinLoc,
                                    Expr *SubExpr, TypeSourceInfo *TInfo,
                                    SourceLocation RParenLoc) {
    return getSema().BuildVAArgExpr(BuiltinLoc,
                                    SubExpr, TInfo,
                                    RParenLoc);
  }

  /// Build a new expression list in parentheses.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildParenListExpr(SourceLocation LParenLoc,
                                  MultiExprArg SubExprs,
                                  SourceLocation RParenLoc) {
    return getSema().ActOnParenListExpr(LParenLoc, RParenLoc, SubExprs);
  }

  /// Build a new address-of-label expression.
  ///
  /// By default, performs semantic analysis, using the name of the label
  /// rather than attempting to map the label statement itself.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildAddrLabelExpr(SourceLocation AmpAmpLoc,
                                  SourceLocation LabelLoc, LabelDecl *Label) {
    return getSema().ActOnAddrLabel(AmpAmpLoc, LabelLoc, Label);
  }

  /// Build a new GNU statement expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildStmtExpr(SourceLocation LParenLoc,
                                   Stmt *SubStmt,
                                   SourceLocation RParenLoc) {
    return getSema().ActOnStmtExpr(LParenLoc, SubStmt, RParenLoc);
  }

  /// Build a new __builtin_choose_expr expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildChooseExpr(SourceLocation BuiltinLoc,
                                     Expr *Cond, Expr *LHS, Expr *RHS,
                                     SourceLocation RParenLoc) {
    return SemaRef.ActOnChooseExpr(BuiltinLoc,
                                   Cond, LHS, RHS,
                                   RParenLoc);
  }

  /// Build a new generic selection expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildGenericSelectionExpr(SourceLocation KeyLoc,
                                         SourceLocation DefaultLoc,
                                         SourceLocation RParenLoc,
                                         Expr *ControllingExpr,
                                         ArrayRef<TypeSourceInfo *> Types,
                                         ArrayRef<Expr *> Exprs) {
    return getSema().CreateGenericSelectionExpr(KeyLoc, DefaultLoc, RParenLoc,
                                                ControllingExpr, Types, Exprs);
  }

  /// Build a new overloaded operator call expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// The semantic analysis provides the behavior of template instantiation,
  /// copying with transformations that turn what looks like an overloaded
  /// operator call into a use of a builtin operator, performing
  /// argument-dependent lookup, etc. Subclasses may override this routine to
  /// provide different behavior.
  ExprResult RebuildCXXOperatorCallExpr(OverloadedOperatorKind Op,
                                              SourceLocation OpLoc,
                                              Expr *Callee,
                                              Expr *First,
                                              Expr *Second);

  /// Build a new C++ "named" cast expression, such as static_cast or
  /// reinterpret_cast.
  ///
  /// By default, this routine dispatches to one of the more-specific routines
  /// for a particular named case, e.g., RebuildCXXStaticCastExpr().
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXNamedCastExpr(SourceLocation OpLoc,
                                           Stmt::StmtClass Class,
                                           SourceLocation LAngleLoc,
                                           TypeSourceInfo *TInfo,
                                           SourceLocation RAngleLoc,
                                           SourceLocation LParenLoc,
                                           Expr *SubExpr,
                                           SourceLocation RParenLoc) {
    switch (Class) {
    case Stmt::CXXStaticCastExprClass:
      return getDerived().RebuildCXXStaticCastExpr(OpLoc, LAngleLoc, TInfo,
                                                   RAngleLoc, LParenLoc,
                                                   SubExpr, RParenLoc);

    case Stmt::CXXDynamicCastExprClass:
      return getDerived().RebuildCXXDynamicCastExpr(OpLoc, LAngleLoc, TInfo,
                                                    RAngleLoc, LParenLoc,
                                                    SubExpr, RParenLoc);

    case Stmt::CXXReinterpretCastExprClass:
      return getDerived().RebuildCXXReinterpretCastExpr(OpLoc, LAngleLoc, TInfo,
                                                        RAngleLoc, LParenLoc,
                                                        SubExpr,
                                                        RParenLoc);

    case Stmt::CXXConstCastExprClass:
      return getDerived().RebuildCXXConstCastExpr(OpLoc, LAngleLoc, TInfo,
                                                   RAngleLoc, LParenLoc,
                                                   SubExpr, RParenLoc);

    default:
      llvm_unreachable("Invalid C++ named cast");
    }
  }

  /// Build a new C++ static_cast expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXStaticCastExpr(SourceLocation OpLoc,
                                            SourceLocation LAngleLoc,
                                            TypeSourceInfo *TInfo,
                                            SourceLocation RAngleLoc,
                                            SourceLocation LParenLoc,
                                            Expr *SubExpr,
                                            SourceLocation RParenLoc) {
    return getSema().BuildCXXNamedCast(OpLoc, tok::kw_static_cast,
                                       TInfo, SubExpr,
                                       SourceRange(LAngleLoc, RAngleLoc),
                                       SourceRange(LParenLoc, RParenLoc));
  }

  /// Build a new C++ dynamic_cast expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXDynamicCastExpr(SourceLocation OpLoc,
                                             SourceLocation LAngleLoc,
                                             TypeSourceInfo *TInfo,
                                             SourceLocation RAngleLoc,
                                             SourceLocation LParenLoc,
                                             Expr *SubExpr,
                                             SourceLocation RParenLoc) {
    return getSema().BuildCXXNamedCast(OpLoc, tok::kw_dynamic_cast,
                                       TInfo, SubExpr,
                                       SourceRange(LAngleLoc, RAngleLoc),
                                       SourceRange(LParenLoc, RParenLoc));
  }

  /// Build a new C++ reinterpret_cast expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXReinterpretCastExpr(SourceLocation OpLoc,
                                                 SourceLocation LAngleLoc,
                                                 TypeSourceInfo *TInfo,
                                                 SourceLocation RAngleLoc,
                                                 SourceLocation LParenLoc,
                                                 Expr *SubExpr,
                                                 SourceLocation RParenLoc) {
    return getSema().BuildCXXNamedCast(OpLoc, tok::kw_reinterpret_cast,
                                       TInfo, SubExpr,
                                       SourceRange(LAngleLoc, RAngleLoc),
                                       SourceRange(LParenLoc, RParenLoc));
  }

  /// Build a new C++ const_cast expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXConstCastExpr(SourceLocation OpLoc,
                                           SourceLocation LAngleLoc,
                                           TypeSourceInfo *TInfo,
                                           SourceLocation RAngleLoc,
                                           SourceLocation LParenLoc,
                                           Expr *SubExpr,
                                           SourceLocation RParenLoc) {
    return getSema().BuildCXXNamedCast(OpLoc, tok::kw_const_cast,
                                       TInfo, SubExpr,
                                       SourceRange(LAngleLoc, RAngleLoc),
                                       SourceRange(LParenLoc, RParenLoc));
  }

  /// Build a new C++ functional-style cast expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXFunctionalCastExpr(TypeSourceInfo *TInfo,
                                          SourceLocation LParenLoc,
                                          Expr *Sub,
                                          SourceLocation RParenLoc,
                                          bool ListInitialization) {
    return getSema().BuildCXXTypeConstructExpr(TInfo, LParenLoc,
                                               MultiExprArg(&Sub, 1), RParenLoc,
                                               ListInitialization);
  }

  /// Build a new C++ __builtin_bit_cast expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildBuiltinBitCastExpr(SourceLocation KWLoc,
                                       TypeSourceInfo *TSI, Expr *Sub,
                                       SourceLocation RParenLoc) {
    return getSema().BuildBuiltinBitCastExpr(KWLoc, TSI, Sub, RParenLoc);
  }

  /// Build a new C++ typeid(type) expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXTypeidExpr(QualType TypeInfoType,
                                        SourceLocation TypeidLoc,
                                        TypeSourceInfo *Operand,
                                        SourceLocation RParenLoc) {
    return getSema().BuildCXXTypeId(TypeInfoType, TypeidLoc, Operand,
                                    RParenLoc);
  }


  /// Build a new C++ typeid(expr) expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXTypeidExpr(QualType TypeInfoType,
                                        SourceLocation TypeidLoc,
                                        Expr *Operand,
                                        SourceLocation RParenLoc) {
    return getSema().BuildCXXTypeId(TypeInfoType, TypeidLoc, Operand,
                                    RParenLoc);
  }

  /// Build a new C++ __uuidof(type) expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXUuidofExpr(QualType TypeInfoType,
                                        SourceLocation TypeidLoc,
                                        TypeSourceInfo *Operand,
                                        SourceLocation RParenLoc) {
    return getSema().BuildCXXUuidof(TypeInfoType, TypeidLoc, Operand,
                                    RParenLoc);
  }

  /// Build a new C++ __uuidof(expr) expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXUuidofExpr(QualType TypeInfoType,
                                        SourceLocation TypeidLoc,
                                        Expr *Operand,
                                        SourceLocation RParenLoc) {
    return getSema().BuildCXXUuidof(TypeInfoType, TypeidLoc, Operand,
                                    RParenLoc);
  }

  /// Build a new C++ "this" expression.
  ///
  /// By default, builds a new "this" expression without performing any
  /// semantic analysis. Subclasses may override this routine to provide
  /// different behavior.
  ExprResult RebuildCXXThisExpr(SourceLocation ThisLoc,
                                QualType ThisType,
                                bool isImplicit) {
    return getSema().BuildCXXThisExpr(ThisLoc, ThisType, isImplicit);
  }

  /// Build a new C++ throw expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXThrowExpr(SourceLocation ThrowLoc, Expr *Sub,
                                 bool IsThrownVariableInScope) {
    return getSema().BuildCXXThrow(ThrowLoc, Sub, IsThrownVariableInScope);
  }

  /// Build a new C++ default-argument expression.
  ///
  /// By default, builds a new default-argument expression, which does not
  /// require any semantic analysis. Subclasses may override this routine to
  /// provide different behavior.
  ExprResult RebuildCXXDefaultArgExpr(SourceLocation Loc, ParmVarDecl *Param) {
    return CXXDefaultArgExpr::Create(getSema().Context, Loc, Param,
                                     getSema().CurContext);
  }

  /// Build a new C++11 default-initialization expression.
  ///
  /// By default, builds a new default field initialization expression, which
  /// does not require any semantic analysis. Subclasses may override this
  /// routine to provide different behavior.
  ExprResult RebuildCXXDefaultInitExpr(SourceLocation Loc,
                                       FieldDecl *Field) {
    return CXXDefaultInitExpr::Create(getSema().Context, Loc, Field,
                                      getSema().CurContext);
  }

  /// Build a new C++ zero-initialization expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXScalarValueInitExpr(TypeSourceInfo *TSInfo,
                                           SourceLocation LParenLoc,
                                           SourceLocation RParenLoc) {
    return getSema().BuildCXXTypeConstructExpr(
        TSInfo, LParenLoc, None, RParenLoc, /*ListInitialization=*/false);
  }

  /// Build a new C++ "new" expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXNewExpr(SourceLocation StartLoc,
                               bool UseGlobal,
                               SourceLocation PlacementLParen,
                               MultiExprArg PlacementArgs,
                               SourceLocation PlacementRParen,
                               SourceRange TypeIdParens,
                               QualType AllocatedType,
                               TypeSourceInfo *AllocatedTypeInfo,
                               Optional<Expr *> ArraySize,
                               SourceRange DirectInitRange,
                               Expr *Initializer) {
    return getSema().BuildCXXNew(StartLoc, UseGlobal,
                                 PlacementLParen,
                                 PlacementArgs,
                                 PlacementRParen,
                                 TypeIdParens,
                                 AllocatedType,
                                 AllocatedTypeInfo,
                                 ArraySize,
                                 DirectInitRange,
                                 Initializer);
  }

  /// Build a new C++ "delete" expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXDeleteExpr(SourceLocation StartLoc,
                                        bool IsGlobalDelete,
                                        bool IsArrayForm,
                                        Expr *Operand) {
    return getSema().ActOnCXXDelete(StartLoc, IsGlobalDelete, IsArrayForm,
                                    Operand);
  }

  /// Build a new type trait expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildTypeTrait(TypeTrait Trait,
                              SourceLocation StartLoc,
                              ArrayRef<TypeSourceInfo *> Args,
                              SourceLocation RParenLoc) {
    return getSema().BuildTypeTrait(Trait, StartLoc, Args, RParenLoc);
  }

  /// Build a new array type trait expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildArrayTypeTrait(ArrayTypeTrait Trait,
                                   SourceLocation StartLoc,
                                   TypeSourceInfo *TSInfo,
                                   Expr *DimExpr,
                                   SourceLocation RParenLoc) {
    return getSema().BuildArrayTypeTrait(Trait, StartLoc, TSInfo, DimExpr, RParenLoc);
  }

  /// Build a new expression trait expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildExpressionTrait(ExpressionTrait Trait,
                                   SourceLocation StartLoc,
                                   Expr *Queried,
                                   SourceLocation RParenLoc) {
    return getSema().BuildExpressionTrait(Trait, StartLoc, Queried, RParenLoc);
  }

  /// Build a new (previously unresolved) declaration reference
  /// expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildDependentScopeDeclRefExpr(
                                          NestedNameSpecifierLoc QualifierLoc,
                                          SourceLocation TemplateKWLoc,
                                       const DeclarationNameInfo &NameInfo,
                              const TemplateArgumentListInfo *TemplateArgs,
                                          bool IsAddressOfOperand,
                                          TypeSourceInfo **RecoveryTSI) {
    CXXScopeSpec SS;
    SS.Adopt(QualifierLoc);

    if (TemplateArgs || TemplateKWLoc.isValid())
      return getSema().BuildQualifiedTemplateIdExpr(SS, TemplateKWLoc, NameInfo,
                                                    TemplateArgs);

    return getSema().BuildQualifiedDeclarationNameExpr(
        SS, NameInfo, IsAddressOfOperand, /*S*/nullptr, RecoveryTSI);
  }

  /// Build a new template-id expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildTemplateIdExpr(const CXXScopeSpec &SS,
                                   SourceLocation TemplateKWLoc,
                                   LookupResult &R,
                                   bool RequiresADL,
                              const TemplateArgumentListInfo *TemplateArgs) {
    return getSema().BuildTemplateIdExpr(SS, TemplateKWLoc, R, RequiresADL,
                                         TemplateArgs);
  }

  /// Build a new object-construction expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXConstructExpr(QualType T,
                                     SourceLocation Loc,
                                     CXXConstructorDecl *Constructor,
                                     bool IsElidable,
                                     MultiExprArg Args,
                                     bool HadMultipleCandidates,
                                     bool ListInitialization,
                                     bool StdInitListInitialization,
                                     bool RequiresZeroInit,
                             CXXConstructExpr::ConstructionKind ConstructKind,
                                     SourceRange ParenRange) {
    SmallVector<Expr*, 8> ConvertedArgs;
    if (getSema().CompleteConstructorCall(Constructor, Args, Loc,
                                          ConvertedArgs))
      return ExprError();

    return getSema().BuildCXXConstructExpr(Loc, T, Constructor,
                                           IsElidable,
                                           ConvertedArgs,
                                           HadMultipleCandidates,
                                           ListInitialization,
                                           StdInitListInitialization,
                                           RequiresZeroInit, ConstructKind,
                                           ParenRange);
  }

  /// Build a new implicit construction via inherited constructor
  /// expression.
  ExprResult RebuildCXXInheritedCtorInitExpr(QualType T, SourceLocation Loc,
                                             CXXConstructorDecl *Constructor,
                                             bool ConstructsVBase,
                                             bool InheritedFromVBase) {
    return new (getSema().Context) CXXInheritedCtorInitExpr(
        Loc, T, Constructor, ConstructsVBase, InheritedFromVBase);
  }

  /// Build a new object-construction expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXTemporaryObjectExpr(TypeSourceInfo *TSInfo,
                                           SourceLocation LParenOrBraceLoc,
                                           MultiExprArg Args,
                                           SourceLocation RParenOrBraceLoc,
                                           bool ListInitialization) {
    return getSema().BuildCXXTypeConstructExpr(
        TSInfo, LParenOrBraceLoc, Args, RParenOrBraceLoc, ListInitialization);
  }

  /// Build a new object-construction expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXUnresolvedConstructExpr(TypeSourceInfo *TSInfo,
                                               SourceLocation LParenLoc,
                                               MultiExprArg Args,
                                               SourceLocation RParenLoc,
                                               bool ListInitialization) {
    return getSema().BuildCXXTypeConstructExpr(TSInfo, LParenLoc, Args,
                                               RParenLoc, ListInitialization);
  }

  /// Build a new member reference expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXDependentScopeMemberExpr(Expr *BaseE,
                                                QualType BaseType,
                                                bool IsArrow,
                                                SourceLocation OperatorLoc,
                                          NestedNameSpecifierLoc QualifierLoc,
                                                SourceLocation TemplateKWLoc,
                                            NamedDecl *FirstQualifierInScope,
                                   const DeclarationNameInfo &MemberNameInfo,
                              const TemplateArgumentListInfo *TemplateArgs) {
    CXXScopeSpec SS;
    SS.Adopt(QualifierLoc);

    return SemaRef.BuildMemberReferenceExpr(BaseE, BaseType,
                                            OperatorLoc, IsArrow,
                                            SS, TemplateKWLoc,
                                            FirstQualifierInScope,
                                            MemberNameInfo,
                                            TemplateArgs, /*S*/nullptr);
  }

  /// Build a new member reference expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildUnresolvedMemberExpr(Expr *BaseE, QualType BaseType,
                                         SourceLocation OperatorLoc,
                                         bool IsArrow,
                                         NestedNameSpecifierLoc QualifierLoc,
                                         SourceLocation TemplateKWLoc,
                                         NamedDecl *FirstQualifierInScope,
                                         LookupResult &R,
                                const TemplateArgumentListInfo *TemplateArgs) {
    CXXScopeSpec SS;
    SS.Adopt(QualifierLoc);

    return SemaRef.BuildMemberReferenceExpr(BaseE, BaseType,
                                            OperatorLoc, IsArrow,
                                            SS, TemplateKWLoc,
                                            FirstQualifierInScope,
                                            R, TemplateArgs, /*S*/nullptr);
  }

  /// Build a new noexcept expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildCXXNoexceptExpr(SourceRange Range, Expr *Arg) {
    return SemaRef.BuildCXXNoexceptExpr(Range.getBegin(), Arg, Range.getEnd());
  }

  /// Build a new expression to compute the length of a parameter pack.
  ExprResult RebuildSizeOfPackExpr(SourceLocation OperatorLoc,
                                   NamedDecl *Pack,
                                   SourceLocation PackLoc,
                                   SourceLocation RParenLoc,
                                   Optional<unsigned> Length,
                                   ArrayRef<TemplateArgument> PartialArgs) {
    return SizeOfPackExpr::Create(SemaRef.Context, OperatorLoc, Pack, PackLoc,
                                  RParenLoc, Length, PartialArgs);
  }

  /// Build a new expression representing a call to a source location
  ///  builtin.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildSourceLocExpr(SourceLocExpr::IdentKind Kind,
                                  SourceLocation BuiltinLoc,
                                  SourceLocation RPLoc,
                                  DeclContext *ParentContext) {
    return getSema().BuildSourceLocExpr(Kind, BuiltinLoc, RPLoc, ParentContext);
  }

  /// Build a new Objective-C boxed expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildConceptSpecializationExpr(NestedNameSpecifierLoc NNS,
      SourceLocation TemplateKWLoc, SourceLocation ConceptNameLoc,
      NamedDecl *FoundDecl, ConceptDecl *NamedConcept,
      TemplateArgumentListInfo *TALI) {
    CXXScopeSpec SS;
    SS.Adopt(NNS);
    ExprResult Result = getSema().CheckConceptTemplateId(SS, TemplateKWLoc,
                                                         ConceptNameLoc,
                                                         FoundDecl,
                                                         NamedConcept, TALI);
    if (Result.isInvalid())
      return ExprError();
    return Result;
  }

    /// \brief Build a new Objective-C boxed expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildObjCBoxedExpr(SourceRange SR, Expr *ValueExpr) {
    return getSema().BuildObjCBoxedExpr(SR, ValueExpr);
  }

  /// Build a new Objective-C array literal.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildObjCArrayLiteral(SourceRange Range,
                                     Expr **Elements, unsigned NumElements) {
    return getSema().BuildObjCArrayLiteral(Range,
                                           MultiExprArg(Elements, NumElements));
  }

  ExprResult RebuildObjCSubscriptRefExpr(SourceLocation RB,
                                         Expr *Base, Expr *Key,
                                         ObjCMethodDecl *getterMethod,
                                         ObjCMethodDecl *setterMethod) {
    return  getSema().BuildObjCSubscriptExpression(RB, Base, Key,
                                                   getterMethod, setterMethod);
  }

  /// Build a new Objective-C dictionary literal.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildObjCDictionaryLiteral(SourceRange Range,
                              MutableArrayRef<ObjCDictionaryElement> Elements) {
    return getSema().BuildObjCDictionaryLiteral(Range, Elements);
  }

  /// Build a new Objective-C \@encode expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildObjCEncodeExpr(SourceLocation AtLoc,
                                         TypeSourceInfo *EncodeTypeInfo,
                                         SourceLocation RParenLoc) {
    return SemaRef.BuildObjCEncodeExpression(AtLoc, EncodeTypeInfo, RParenLoc);
  }

  /// Build a new Objective-C class message.
  ExprResult RebuildObjCMessageExpr(TypeSourceInfo *ReceiverTypeInfo,
                                          Selector Sel,
                                          ArrayRef<SourceLocation> SelectorLocs,
                                          ObjCMethodDecl *Method,
                                          SourceLocation LBracLoc,
                                          MultiExprArg Args,
                                          SourceLocation RBracLoc) {
    return SemaRef.BuildClassMessage(ReceiverTypeInfo,
                                     ReceiverTypeInfo->getType(),
                                     /*SuperLoc=*/SourceLocation(),
                                     Sel, Method, LBracLoc, SelectorLocs,
                                     RBracLoc, Args);
  }

  /// Build a new Objective-C instance message.
  ExprResult RebuildObjCMessageExpr(Expr *Receiver,
                                          Selector Sel,
                                          ArrayRef<SourceLocation> SelectorLocs,
                                          ObjCMethodDecl *Method,
                                          SourceLocation LBracLoc,
                                          MultiExprArg Args,
                                          SourceLocation RBracLoc) {
    return SemaRef.BuildInstanceMessage(Receiver,
                                        Receiver->getType(),
                                        /*SuperLoc=*/SourceLocation(),
                                        Sel, Method, LBracLoc, SelectorLocs,
                                        RBracLoc, Args);
  }

  /// Build a new Objective-C instance/class message to 'super'.
  ExprResult RebuildObjCMessageExpr(SourceLocation SuperLoc,
                                    Selector Sel,
                                    ArrayRef<SourceLocation> SelectorLocs,
                                    QualType SuperType,
                                    ObjCMethodDecl *Method,
                                    SourceLocation LBracLoc,
                                    MultiExprArg Args,
                                    SourceLocation RBracLoc) {
    return Method->isInstanceMethod() ? SemaRef.BuildInstanceMessage(nullptr,
                                          SuperType,
                                          SuperLoc,
                                          Sel, Method, LBracLoc, SelectorLocs,
                                          RBracLoc, Args)
                                      : SemaRef.BuildClassMessage(nullptr,
                                          SuperType,
                                          SuperLoc,
                                          Sel, Method, LBracLoc, SelectorLocs,
                                          RBracLoc, Args);


  }

  /// Build a new Objective-C ivar reference expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildObjCIvarRefExpr(Expr *BaseArg, ObjCIvarDecl *Ivar,
                                          SourceLocation IvarLoc,
                                          bool IsArrow, bool IsFreeIvar) {
    CXXScopeSpec SS;
    DeclarationNameInfo NameInfo(Ivar->getDeclName(), IvarLoc);
    ExprResult Result = getSema().BuildMemberReferenceExpr(
        BaseArg, BaseArg->getType(),
        /*FIXME:*/ IvarLoc, IsArrow, SS, SourceLocation(),
        /*FirstQualifierInScope=*/nullptr, NameInfo,
        /*TemplateArgs=*/nullptr,
        /*S=*/nullptr);
    if (IsFreeIvar && Result.isUsable())
      cast<ObjCIvarRefExpr>(Result.get())->setIsFreeIvar(IsFreeIvar);
    return Result;
  }

  /// Build a new Objective-C property reference expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildObjCPropertyRefExpr(Expr *BaseArg,
                                        ObjCPropertyDecl *Property,
                                        SourceLocation PropertyLoc) {
    CXXScopeSpec SS;
    DeclarationNameInfo NameInfo(Property->getDeclName(), PropertyLoc);
    return getSema().BuildMemberReferenceExpr(BaseArg, BaseArg->getType(),
                                              /*FIXME:*/PropertyLoc,
                                              /*IsArrow=*/false,
                                              SS, SourceLocation(),
                                              /*FirstQualifierInScope=*/nullptr,
                                              NameInfo,
                                              /*TemplateArgs=*/nullptr,
                                              /*S=*/nullptr);
  }

  /// Build a new Objective-C property reference expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildObjCPropertyRefExpr(Expr *Base, QualType T,
                                        ObjCMethodDecl *Getter,
                                        ObjCMethodDecl *Setter,
                                        SourceLocation PropertyLoc) {
    // Since these expressions can only be value-dependent, we do not
    // need to perform semantic analysis again.
    return Owned(
      new (getSema().Context) ObjCPropertyRefExpr(Getter, Setter, T,
                                                  VK_LValue, OK_ObjCProperty,
                                                  PropertyLoc, Base));
  }

  /// Build a new Objective-C "isa" expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildObjCIsaExpr(Expr *BaseArg, SourceLocation IsaLoc,
                                SourceLocation OpLoc, bool IsArrow) {
    CXXScopeSpec SS;
    DeclarationNameInfo NameInfo(&getSema().Context.Idents.get("isa"), IsaLoc);
    return getSema().BuildMemberReferenceExpr(BaseArg, BaseArg->getType(),
                                              OpLoc, IsArrow,
                                              SS, SourceLocation(),
                                              /*FirstQualifierInScope=*/nullptr,
                                              NameInfo,
                                              /*TemplateArgs=*/nullptr,
                                              /*S=*/nullptr);
  }

  /// Build a new shuffle vector expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildShuffleVectorExpr(SourceLocation BuiltinLoc,
                                      MultiExprArg SubExprs,
                                      SourceLocation RParenLoc) {
    // Find the declaration for __builtin_shufflevector
    const IdentifierInfo &Name
      = SemaRef.Context.Idents.get("__builtin_shufflevector");
    TranslationUnitDecl *TUDecl = SemaRef.Context.getTranslationUnitDecl();
    DeclContext::lookup_result Lookup = TUDecl->lookup(DeclarationName(&Name));
    assert(!Lookup.empty() && "No __builtin_shufflevector?");

    // Build a reference to the __builtin_shufflevector builtin
    FunctionDecl *Builtin = cast<FunctionDecl>(Lookup.front());
    Expr *Callee = new (SemaRef.Context)
        DeclRefExpr(SemaRef.Context, Builtin, false,
                    SemaRef.Context.BuiltinFnTy, VK_RValue, BuiltinLoc);
    QualType CalleePtrTy = SemaRef.Context.getPointerType(Builtin->getType());
    Callee = SemaRef.ImpCastExprToType(Callee, CalleePtrTy,
                                       CK_BuiltinFnToFnPtr).get();

    // Build the CallExpr
    ExprResult TheCall = CallExpr::Create(
        SemaRef.Context, Callee, SubExprs, Builtin->getCallResultType(),
        Expr::getValueKindForType(Builtin->getReturnType()), RParenLoc);

    // Type-check the __builtin_shufflevector expression.
    return SemaRef.SemaBuiltinShuffleVector(cast<CallExpr>(TheCall.get()));
  }

  /// Build a new convert vector expression.
  ExprResult RebuildConvertVectorExpr(SourceLocation BuiltinLoc,
                                      Expr *SrcExpr, TypeSourceInfo *DstTInfo,
                                      SourceLocation RParenLoc) {
    return SemaRef.SemaConvertVectorExpr(SrcExpr, DstTInfo,
                                         BuiltinLoc, RParenLoc);
  }

  /// Build a new template argument pack expansion.
  ///
  /// By default, performs semantic analysis to build a new pack expansion
  /// for a template argument. Subclasses may override this routine to provide
  /// different behavior.
  TemplateArgumentLoc RebuildPackExpansion(TemplateArgumentLoc Pattern,
                                           SourceLocation EllipsisLoc,
                                           Optional<unsigned> NumExpansions) {
    switch (Pattern.getArgument().getKind()) {
    case TemplateArgument::Expression: {
      ExprResult Result
        = getSema().CheckPackExpansion(Pattern.getSourceExpression(),
                                       EllipsisLoc, NumExpansions);
      if (Result.isInvalid())
        return TemplateArgumentLoc();

      return TemplateArgumentLoc(Result.get(), Result.get());
    }

    case TemplateArgument::Template:
      return TemplateArgumentLoc(TemplateArgument(
                                          Pattern.getArgument().getAsTemplate(),
                                                  NumExpansions),
                                 Pattern.getTemplateQualifierLoc(),
                                 Pattern.getTemplateNameLoc(),
                                 EllipsisLoc);

    case TemplateArgument::Null:
    case TemplateArgument::Integral:
    case TemplateArgument::Declaration:
    case TemplateArgument::Pack:
    case TemplateArgument::TemplateExpansion:
    case TemplateArgument::NullPtr:
      llvm_unreachable("Pack expansion pattern has no parameter packs");

    case TemplateArgument::Type:
      if (TypeSourceInfo *Expansion
            = getSema().CheckPackExpansion(Pattern.getTypeSourceInfo(),
                                           EllipsisLoc,
                                           NumExpansions))
        return TemplateArgumentLoc(TemplateArgument(Expansion->getType()),
                                   Expansion);
      break;
    }

    return TemplateArgumentLoc();
  }

  /// Build a new expression pack expansion.
  ///
  /// By default, performs semantic analysis to build a new pack expansion
  /// for an expression. Subclasses may override this routine to provide
  /// different behavior.
  ExprResult RebuildPackExpansion(Expr *Pattern, SourceLocation EllipsisLoc,
                                  Optional<unsigned> NumExpansions) {
    return getSema().CheckPackExpansion(Pattern, EllipsisLoc, NumExpansions);
  }

  /// Build a new C++1z fold-expression.
  ///
  /// By default, performs semantic analysis in order to build a new fold
  /// expression.
  ExprResult RebuildCXXFoldExpr(SourceLocation LParenLoc, Expr *LHS,
                                BinaryOperatorKind Operator,
                                SourceLocation EllipsisLoc, Expr *RHS,
                                SourceLocation RParenLoc,
                                Optional<unsigned> NumExpansions) {
    return getSema().BuildCXXFoldExpr(LParenLoc, LHS, Operator, EllipsisLoc,
                                      RHS, RParenLoc, NumExpansions);
  }

  /// Build an empty C++1z fold-expression with the given operator.
  ///
  /// By default, produces the fallback value for the fold-expression, or
  /// produce an error if there is no fallback value.
  ExprResult RebuildEmptyCXXFoldExpr(SourceLocation EllipsisLoc,
                                     BinaryOperatorKind Operator) {
    return getSema().BuildEmptyCXXFoldExpr(EllipsisLoc, Operator);
  }

  /// Build a new atomic operation expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
  /// Subclasses may override this routine to provide different behavior.
  ExprResult RebuildAtomicExpr(SourceLocation BuiltinLoc, MultiExprArg SubExprs,
                               AtomicExpr::AtomicOp Op,
                               SourceLocation RParenLoc) {
    // Use this for all of the locations, since we don't know the difference
    // between the call and the expr at this point.
    SourceRange Range{BuiltinLoc, RParenLoc};
    return getSema().BuildAtomicExpr(Range, Range, RParenLoc, SubExprs, Op,
                                     Sema::AtomicArgumentOrder::AST);
  }

private:
  TypeLoc TransformTypeInObjectScope(TypeLoc TL,
                                     QualType ObjectType,
                                     NamedDecl *FirstQualifierInScope,
                                     CXXScopeSpec &SS);

  TypeSourceInfo *TransformTypeInObjectScope(TypeSourceInfo *TSInfo,
                                             QualType ObjectType,
                                             NamedDecl *FirstQualifierInScope,
                                             CXXScopeSpec &SS);

  TypeSourceInfo *TransformTSIInObjectScope(TypeLoc TL, QualType ObjectType,
                                            NamedDecl *FirstQualifierInScope,
                                            CXXScopeSpec &SS);

  QualType TransformDependentNameType(TypeLocBuilder &TLB,
                                      DependentNameTypeLoc TL,
                                      bool DeducibleTSTContext);
};

template <typename Derived>
StmtResult TreeTransform<Derived>::TransformStmt(Stmt *S, StmtDiscardKind SDK) {
  if (!S)
    return S;

  switch (S->getStmtClass()) {
  case Stmt::NoStmtClass: break;

  // Transform individual statement nodes
  // Pass SDK into statements that can produce a value
#define STMT(Node, Parent)                                              \
  case Stmt::Node##Class: return getDerived().Transform##Node(cast<Node>(S));
#define VALUESTMT(Node, Parent)                                         \
  case Stmt::Node##Class:                                               \
    return getDerived().Transform##Node(cast<Node>(S), SDK);
#define ABSTRACT_STMT(Node)
#define EXPR(Node, Parent)
#include "clang/AST/StmtNodes.inc"

  // Transform expressions by calling TransformExpr.
#define STMT(Node, Parent)
#define ABSTRACT_STMT(Stmt)
#define EXPR(Node, Parent) case Stmt::Node##Class:
#include "clang/AST/StmtNodes.inc"
    {
      ExprResult E = getDerived().TransformExpr(cast<Expr>(S));

      if (SDK == SDK_StmtExprResult)
        E = getSema().ActOnStmtExprResult(E);
      return getSema().ActOnExprStmt(E, SDK == SDK_Discarded);
    }
  }

  return S;
}

template<typename Derived>
OMPClause *TreeTransform<Derived>::TransformOMPClause(OMPClause *S) {
  if (!S)
    return S;

  switch (S->getClauseKind()) {
  default: break;
  // Transform individual clause nodes
#define OPENMP_CLAUSE(Name, Class)                                             \
  case OMPC_ ## Name :                                                         \
    return getDerived().Transform ## Class(cast<Class>(S));
#include "clang/Basic/OpenMPKinds.def"
  }

  return S;
}


template<typename Derived>
ExprResult TreeTransform<Derived>::TransformExpr(Expr *E) {
  if (!E)
    return E;

  switch (E->getStmtClass()) {
    case Stmt::NoStmtClass: break;
#define STMT(Node, Parent) case Stmt::Node##Class: break;
#define ABSTRACT_STMT(Stmt)
#define EXPR(Node, Parent)                                              \
    case Stmt::Node##Class: return getDerived().Transform##Node(cast<Node>(E));
#include "clang/AST/StmtNodes.inc"
  }

  return E;
}

template<typename Derived>
ExprResult TreeTransform<Derived>::TransformInitializer(Expr *Init,
                                                        bool NotCopyInit) {
  // Initializers are instantiated like expressions, except that various outer
  // layers are stripped.
  if (!Init)
    return Init;

  if (auto *FE = dyn_cast<FullExpr>(Init))
    Init = FE->getSubExpr();

  if (auto *AIL = dyn_cast<ArrayInitLoopExpr>(Init))
    Init = AIL->getCommonExpr();

  if (MaterializeTemporaryExpr *MTE = dyn_cast<MaterializeTemporaryExpr>(Init))
    Init = MTE->GetTemporaryExpr();

  while (CXXBindTemporaryExpr *Binder = dyn_cast<CXXBindTemporaryExpr>(Init))
    Init = Binder->getSubExpr();

  if (ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(Init))
    Init = ICE->getSubExprAsWritten();

  if (CXXStdInitializerListExpr *ILE =
          dyn_cast<CXXStdInitializerListExpr>(Init))
    return TransformInitializer(ILE->getSubExpr(), NotCopyInit);

  // If this is copy-initialization, we only need to reconstruct
  // InitListExprs. Other forms of copy-initialization will be a no-op if
  // the initializer is already the right type.
  CXXConstructExpr *Construct = dyn_cast<CXXConstructExpr>(Init);
  if (!NotCopyInit && !(Construct && Construct->isListInitialization()))
    return getDerived().TransformExpr(Init);

  // Revert value-initialization back to empty parens.
  if (CXXScalarValueInitExpr *VIE = dyn_cast<CXXScalarValueInitExpr>(Init)) {
    SourceRange Parens = VIE->getSourceRange();
    return getDerived().RebuildParenListExpr(Parens.getBegin(), None,
                                             Parens.getEnd());
  }

  // FIXME: We shouldn't build ImplicitValueInitExprs for direct-initialization.
  if (isa<ImplicitValueInitExpr>(Init))
    return getDerived().RebuildParenListExpr(SourceLocation(), None,
                                             SourceLocation());

  // Revert initialization by constructor back to a parenthesized or braced list
  // of expressions. Any other form of initializer can just be reused directly.
  if (!Construct || isa<CXXTemporaryObjectExpr>(Construct))
    return getDerived().TransformExpr(Init);

  // If the initialization implicitly converted an initializer list to a
  // std::initializer_list object, unwrap the std::initializer_list too.
  if (Construct && Construct->isStdInitListInitialization())
    return TransformInitializer(Construct->getArg(0), NotCopyInit);

  // Enter a list-init context if this was list initialization.
  EnterExpressionEvaluationContext Context(
      getSema(), EnterExpressionEvaluationContext::InitList,
      Construct->isListInitialization());

  SmallVector<Expr*, 8> NewArgs;
  bool ArgChanged = false;
  if (getDerived().TransformExprs(Construct->getArgs(), Construct->getNumArgs(),
                                  /*IsCall*/true, NewArgs, &ArgChanged))
    return ExprError();

  // If this was list initialization, revert to syntactic list form.
  if (Construct->isListInitialization())
    return getDerived().RebuildInitList(Construct->getBeginLoc(), NewArgs,
                                        Construct->getEndLoc());

  // Build a ParenListExpr to represent anything else.
  SourceRange Parens = Construct->getParenOrBraceRange();
  if (Parens.isInvalid()) {
    // This was a variable declaration's initialization for which no initializer
    // was specified.
    assert(NewArgs.empty() &&
           "no parens or braces but have direct init with arguments?");
    return ExprEmpty();
  }
  return getDerived().RebuildParenListExpr(Parens.getBegin(), NewArgs,
                                           Parens.getEnd());
}

template<typename Derived>
bool TreeTransform<Derived>::TransformExprs(Expr *const *Inputs,
                                            unsigned NumInputs,
                                            bool IsCall,
                                      SmallVectorImpl<Expr *> &Outputs,
                                            bool *ArgChanged) {
  for (unsigned I = 0; I != NumInputs; ++I) {
    // If requested, drop call arguments that need to be dropped.
    if (IsCall && getDerived().DropCallArgument(Inputs[I])) {
      if (ArgChanged)
        *ArgChanged = true;

      break;
    }

    if (PackExpansionExpr *Expansion = dyn_cast<PackExpansionExpr>(Inputs[I])) {
      Expr *Pattern = Expansion->getPattern();

      SmallVector<UnexpandedParameterPack, 2> Unexpanded;
      getSema().collectUnexpandedParameterPacks(Pattern, Unexpanded);
      assert(!Unexpanded.empty() && "Pack expansion without parameter packs?");

      // Determine whether the set of unexpanded parameter packs can and should
      // be expanded.
      bool Expand = true;
      bool RetainExpansion = false;
      Optional<unsigned> OrigNumExpansions = Expansion->getNumExpansions();
      Optional<unsigned> NumExpansions = OrigNumExpansions;
      if (getDerived().TryExpandParameterPacks(Expansion->getEllipsisLoc(),
                                               Pattern->getSourceRange(),
                                               Unexpanded,
                                               Expand, RetainExpansion,
                                               NumExpansions))
        return true;

      if (!Expand) {
        // The transform has determined that we should perform a simple
        // transformation on the pack expansion, producing another pack
        // expansion.
        Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(getSema(), -1);
        ExprResult OutPattern = getDerived().TransformExpr(Pattern);
        if (OutPattern.isInvalid())
          return true;

        ExprResult Out = getDerived().RebuildPackExpansion(OutPattern.get(),
                                                Expansion->getEllipsisLoc(),
                                                           NumExpansions);
        if (Out.isInvalid())
          return true;

        if (ArgChanged)
          *ArgChanged = true;
        Outputs.push_back(Out.get());
        continue;
      }

      // Record right away that the argument was changed.  This needs
      // to happen even if the array expands to nothing.
      if (ArgChanged) *ArgChanged = true;

      // The transform has determined that we should perform an elementwise
      // expansion of the pattern. Do so.
      for (unsigned I = 0; I != *NumExpansions; ++I) {
        Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(getSema(), I);
        ExprResult Out = getDerived().TransformExpr(Pattern);
        if (Out.isInvalid())
          return true;

        if (Out.get()->containsUnexpandedParameterPack()) {
          Out = getDerived().RebuildPackExpansion(
              Out.get(), Expansion->getEllipsisLoc(), OrigNumExpansions);
          if (Out.isInvalid())
            return true;
        }

        Outputs.push_back(Out.get());
      }

      // If we're supposed to retain a pack expansion, do so by temporarily
      // forgetting the partially-substituted parameter pack.
      if (RetainExpansion) {
        ForgetPartiallySubstitutedPackRAII Forget(getDerived());

        ExprResult Out = getDerived().TransformExpr(Pattern);
        if (Out.isInvalid())
          return true;

        Out = getDerived().RebuildPackExpansion(
            Out.get(), Expansion->getEllipsisLoc(), OrigNumExpansions);
        if (Out.isInvalid())
          return true;

        Outputs.push_back(Out.get());
      }

      continue;
    }

    ExprResult Result =
      IsCall ? getDerived().TransformInitializer(Inputs[I], /*DirectInit*/false)
             : getDerived().TransformExpr(Inputs[I]);
    if (Result.isInvalid())
      return true;

    if (Result.get() != Inputs[I] && ArgChanged)
      *ArgChanged = true;

    Outputs.push_back(Result.get());
  }

  return false;
}

template <typename Derived>
Sema::ConditionResult TreeTransform<Derived>::TransformCondition(
    SourceLocation Loc, VarDecl *Var, Expr *Expr, Sema::ConditionKind Kind) {
  if (Var) {
    VarDecl *ConditionVar = cast_or_null<VarDecl>(
        getDerived().TransformDefinition(Var->getLocation(), Var));

    if (!ConditionVar)
      return Sema::ConditionError();

    return getSema().ActOnConditionVariable(ConditionVar, Loc, Kind);
  }

  if (Expr) {
    ExprResult CondExpr = getDerived().TransformExpr(Expr);

    if (CondExpr.isInvalid())
      return Sema::ConditionError();

    return getSema().ActOnCondition(nullptr, Loc, CondExpr.get(), Kind);
  }

  return Sema::ConditionResult();
}

template<typename Derived>
NestedNameSpecifierLoc
TreeTransform<Derived>::TransformNestedNameSpecifierLoc(
                                                    NestedNameSpecifierLoc NNS,
                                                     QualType ObjectType,
                                             NamedDecl *FirstQualifierInScope) {
  SmallVector<NestedNameSpecifierLoc, 4> Qualifiers;
  for (NestedNameSpecifierLoc Qualifier = NNS; Qualifier;
       Qualifier = Qualifier.getPrefix())
    Qualifiers.push_back(Qualifier);

  CXXScopeSpec SS;
  while (!Qualifiers.empty()) {
    NestedNameSpecifierLoc Q = Qualifiers.pop_back_val();
    NestedNameSpecifier *QNNS = Q.getNestedNameSpecifier();

    switch (QNNS->getKind()) {
    case NestedNameSpecifier::Identifier: {
      Sema::NestedNameSpecInfo IdInfo(QNNS->getAsIdentifier(),
                          Q.getLocalBeginLoc(), Q.getLocalEndLoc(), ObjectType);
      if (SemaRef.BuildCXXNestedNameSpecifier(/*Scope=*/nullptr, IdInfo, false,
                                              SS, FirstQualifierInScope, false))
        return NestedNameSpecifierLoc();
    }
      break;

    case NestedNameSpecifier::Namespace: {
      NamespaceDecl *NS
        = cast_or_null<NamespaceDecl>(
                                    getDerived().TransformDecl(
                                                          Q.getLocalBeginLoc(),
                                                       QNNS->getAsNamespace()));
      SS.Extend(SemaRef.Context, NS, Q.getLocalBeginLoc(), Q.getLocalEndLoc());
      break;
    }

    case NestedNameSpecifier::NamespaceAlias: {
      NamespaceAliasDecl *Alias
        = cast_or_null<NamespaceAliasDecl>(
                      getDerived().TransformDecl(Q.getLocalBeginLoc(),
                                                 QNNS->getAsNamespaceAlias()));
      SS.Extend(SemaRef.Context, Alias, Q.getLocalBeginLoc(),
                Q.getLocalEndLoc());
      break;
    }

    case NestedNameSpecifier::Global:
      // There is no meaningful transformation that one could perform on the
      // global scope.
      SS.MakeGlobal(SemaRef.Context, Q.getBeginLoc());
      break;

    case NestedNameSpecifier::Super: {
      CXXRecordDecl *RD =
          cast_or_null<CXXRecordDecl>(getDerived().TransformDecl(
              SourceLocation(), QNNS->getAsRecordDecl()));
      SS.MakeSuper(SemaRef.Context, RD, Q.getBeginLoc(), Q.getEndLoc());
      break;
    }

    case NestedNameSpecifier::TypeSpecWithTemplate:
    case NestedNameSpecifier::TypeSpec: {
      TypeLoc TL = TransformTypeInObjectScope(Q.getTypeLoc(), ObjectType,
                                              FirstQualifierInScope, SS);

      if (!TL)
        return NestedNameSpecifierLoc();

      if (TL.getType()->isDependentType() || TL.getType()->isRecordType() ||
          (SemaRef.getLangOpts().CPlusPlus11 &&
           TL.getType()->isEnumeralType())) {
        assert(!TL.getType().hasLocalQualifiers() &&
               "Can't get cv-qualifiers here");
        if (TL.getType()->isEnumeralType())
          SemaRef.Diag(TL.getBeginLoc(),
                       diag::warn_cxx98_compat_enum_nested_name_spec);
        SS.Extend(SemaRef.Context, /*FIXME:*/SourceLocation(), TL,
                  Q.getLocalEndLoc());
        break;
      }
      // If the nested-name-specifier is an invalid type def, don't emit an
      // error because a previous error should have already been emitted.
      TypedefTypeLoc TTL = TL.getAs<TypedefTypeLoc>();
      if (!TTL || !TTL.getTypedefNameDecl()->isInvalidDecl()) {
        SemaRef.Diag(TL.getBeginLoc(), diag::err_nested_name_spec_non_tag)
          << TL.getType() << SS.getRange();
      }
      return NestedNameSpecifierLoc();
    }
    }

    // The qualifier-in-scope and object type only apply to the leftmost entity.
    FirstQualifierInScope = nullptr;
    ObjectType = QualType();
  }

  // Don't rebuild the nested-name-specifier if we don't have to.
  if (SS.getScopeRep() == NNS.getNestedNameSpecifier() &&
      !getDerived().AlwaysRebuild())
    return NNS;

  // If we can re-use the source-location data from the original
  // nested-name-specifier, do so.
  if (SS.location_size() == NNS.getDataLength() &&
      memcmp(SS.location_data(), NNS.getOpaqueData(), SS.location_size()) == 0)
    return NestedNameSpecifierLoc(SS.getScopeRep(), NNS.getOpaqueData());

  // Allocate new nested-name-specifier location information.
  return SS.getWithLocInContext(SemaRef.Context);
}

template<typename Derived>
DeclarationNameInfo
TreeTransform<Derived>
::TransformDeclarationNameInfo(const DeclarationNameInfo &NameInfo) {
  DeclarationName Name = NameInfo.getName();
  if (!Name)
    return DeclarationNameInfo();

  switch (Name.getNameKind()) {
  case DeclarationName::Identifier:
  case DeclarationName::ObjCZeroArgSelector:
  case DeclarationName::ObjCOneArgSelector:
  case DeclarationName::ObjCMultiArgSelector:
  case DeclarationName::CXXOperatorName:
  case DeclarationName::CXXLiteralOperatorName:
  case DeclarationName::CXXUsingDirective:
    return NameInfo;

  case DeclarationName::CXXDeductionGuideName: {
    TemplateDecl *OldTemplate = Name.getCXXDeductionGuideTemplate();
    TemplateDecl *NewTemplate = cast_or_null<TemplateDecl>(
        getDerived().TransformDecl(NameInfo.getLoc(), OldTemplate));
    if (!NewTemplate)
      return DeclarationNameInfo();

    DeclarationNameInfo NewNameInfo(NameInfo);
    NewNameInfo.setName(
        SemaRef.Context.DeclarationNames.getCXXDeductionGuideName(NewTemplate));
    return NewNameInfo;
  }

  case DeclarationName::CXXConstructorName:
  case DeclarationName::CXXDestructorName:
  case DeclarationName::CXXConversionFunctionName: {
    TypeSourceInfo *NewTInfo;
    CanQualType NewCanTy;
    if (TypeSourceInfo *OldTInfo = NameInfo.getNamedTypeInfo()) {
      NewTInfo = getDerived().TransformType(OldTInfo);
      if (!NewTInfo)
        return DeclarationNameInfo();
      NewCanTy = SemaRef.Context.getCanonicalType(NewTInfo->getType());
    }
    else {
      NewTInfo = nullptr;
      TemporaryBase Rebase(*this, NameInfo.getLoc(), Name);
      QualType NewT = getDerived().TransformType(Name.getCXXNameType());
      if (NewT.isNull())
        return DeclarationNameInfo();
      NewCanTy = SemaRef.Context.getCanonicalType(NewT);
    }

    DeclarationName NewName
      = SemaRef.Context.DeclarationNames.getCXXSpecialName(Name.getNameKind(),
                                                           NewCanTy);
    DeclarationNameInfo NewNameInfo(NameInfo);
    NewNameInfo.setName(NewName);
    NewNameInfo.setNamedTypeInfo(NewTInfo);
    return NewNameInfo;
  }
  }

  llvm_unreachable("Unknown name kind.");
}

template<typename Derived>
TemplateName
TreeTransform<Derived>::TransformTemplateName(CXXScopeSpec &SS,
                                              TemplateName Name,
                                              SourceLocation NameLoc,
                                              QualType ObjectType,
                                              NamedDecl *FirstQualifierInScope,
                                              bool AllowInjectedClassName) {
  if (QualifiedTemplateName *QTN = Name.getAsQualifiedTemplateName()) {
    TemplateDecl *Template = QTN->getTemplateDecl();
    assert(Template && "qualified template name must refer to a template");

    TemplateDecl *TransTemplate
      = cast_or_null<TemplateDecl>(getDerived().TransformDecl(NameLoc,
                                                              Template));
    if (!TransTemplate)
      return TemplateName();

    if (!getDerived().AlwaysRebuild() &&
        SS.getScopeRep() == QTN->getQualifier() &&
        TransTemplate == Template)
      return Name;

    return getDerived().RebuildTemplateName(SS, QTN->hasTemplateKeyword(),
                                            TransTemplate);
  }

  if (DependentTemplateName *DTN = Name.getAsDependentTemplateName()) {
    if (SS.getScopeRep()) {
      // These apply to the scope specifier, not the template.
      ObjectType = QualType();
      FirstQualifierInScope = nullptr;
    }

    if (!getDerived().AlwaysRebuild() &&
        SS.getScopeRep() == DTN->getQualifier() &&
        ObjectType.isNull())
      return Name;

    // FIXME: Preserve the location of the "template" keyword.
    SourceLocation TemplateKWLoc = NameLoc;

    if (DTN->isIdentifier()) {
      return getDerived().RebuildTemplateName(SS,
                                              TemplateKWLoc,
                                              *DTN->getIdentifier(),
                                              NameLoc,
                                              ObjectType,
                                              FirstQualifierInScope,
                                              AllowInjectedClassName);
    }

    return getDerived().RebuildTemplateName(SS, TemplateKWLoc,
                                            DTN->getOperator(), NameLoc,
                                            ObjectType, AllowInjectedClassName);
  }

  if (TemplateDecl *Template = Name.getAsTemplateDecl()) {
    TemplateDecl *TransTemplate
      = cast_or_null<TemplateDecl>(getDerived().TransformDecl(NameLoc,
                                                              Template));
    if (!TransTemplate)
      return TemplateName();

    if (!getDerived().AlwaysRebuild() &&
        TransTemplate == Template)
      return Name;

    return TemplateName(TransTemplate);
  }

  if (SubstTemplateTemplateParmPackStorage *SubstPack
      = Name.getAsSubstTemplateTemplateParmPack()) {
    TemplateTemplateParmDecl *TransParam
    = cast_or_null<TemplateTemplateParmDecl>(
            getDerived().TransformDecl(NameLoc, SubstPack->getParameterPack()));
    if (!TransParam)
      return TemplateName();

    if (!getDerived().AlwaysRebuild() &&
        TransParam == SubstPack->getParameterPack())
      return Name;

    return getDerived().RebuildTemplateName(TransParam,
                                            SubstPack->getArgumentPack());
  }

  // These should be getting filtered out before they reach the AST.
  llvm_unreachable("overloaded function decl survived to here");
}

template<typename Derived>
void TreeTransform<Derived>::InventTemplateArgumentLoc(
                                         const TemplateArgument &Arg,
                                         TemplateArgumentLoc &Output) {
  SourceLocation Loc = getDerived().getBaseLocation();
  switch (Arg.getKind()) {
  case TemplateArgument::Null:
    llvm_unreachable("null template argument in TreeTransform");
    break;

  case TemplateArgument::Type:
    Output = TemplateArgumentLoc(Arg,
               SemaRef.Context.getTrivialTypeSourceInfo(Arg.getAsType(), Loc));

    break;

  case TemplateArgument::Template:
  case TemplateArgument::TemplateExpansion: {
    NestedNameSpecifierLocBuilder Builder;
    TemplateName Template = Arg.getAsTemplateOrTemplatePattern();
    if (DependentTemplateName *DTN = Template.getAsDependentTemplateName())
      Builder.MakeTrivial(SemaRef.Context, DTN->getQualifier(), Loc);
    else if (QualifiedTemplateName *QTN = Template.getAsQualifiedTemplateName())
      Builder.MakeTrivial(SemaRef.Context, QTN->getQualifier(), Loc);

    if (Arg.getKind() == TemplateArgument::Template)
      Output = TemplateArgumentLoc(Arg,
                                   Builder.getWithLocInContext(SemaRef.Context),
                                   Loc);
    else
      Output = TemplateArgumentLoc(Arg,
                                   Builder.getWithLocInContext(SemaRef.Context),
                                   Loc, Loc);

    break;
  }

  case TemplateArgument::Expression:
    Output = TemplateArgumentLoc(Arg, Arg.getAsExpr());
    break;

  case TemplateArgument::Declaration:
  case TemplateArgument::Integral:
  case TemplateArgument::Pack:
  case TemplateArgument::NullPtr:
    Output = TemplateArgumentLoc(Arg, TemplateArgumentLocInfo());
    break;
  }
}

template<typename Derived>
bool TreeTransform<Derived>::TransformTemplateArgument(
                                         const TemplateArgumentLoc &Input,
                                         TemplateArgumentLoc &Output, bool Uneval) {
  const TemplateArgument &Arg = Input.getArgument();
  switch (Arg.getKind()) {
  case TemplateArgument::Null:
  case TemplateArgument::Integral:
  case TemplateArgument::Pack:
  case TemplateArgument::Declaration:
  case TemplateArgument::NullPtr:
    llvm_unreachable("Unexpected TemplateArgument");

  case TemplateArgument::Type: {
    TypeSourceInfo *DI = Input.getTypeSourceInfo();
    if (!DI)
      DI = InventTypeSourceInfo(Input.getArgument().getAsType());

    DI = getDerived().TransformType(DI);
    if (!DI) return true;

    Output = TemplateArgumentLoc(TemplateArgument(DI->getType()), DI);
    return false;
  }

  case TemplateArgument::Template: {
    NestedNameSpecifierLoc QualifierLoc = Input.getTemplateQualifierLoc();
    if (QualifierLoc) {
      QualifierLoc = getDerived().TransformNestedNameSpecifierLoc(QualifierLoc);
      if (!QualifierLoc)
        return true;
    }

    CXXScopeSpec SS;
    SS.Adopt(QualifierLoc);
    TemplateName Template
      = getDerived().TransformTemplateName(SS, Arg.getAsTemplate(),
                                           Input.getTemplateNameLoc());
    if (Template.isNull())
      return true;

    Output = TemplateArgumentLoc(TemplateArgument(Template), QualifierLoc,
                                 Input.getTemplateNameLoc());
    return false;
  }

  case TemplateArgument::TemplateExpansion:
    llvm_unreachable("Caller should expand pack expansions");

  case TemplateArgument::Expression: {
    // Template argument expressions are constant expressions.
    EnterExpressionEvaluationContext Unevaluated(
        getSema(),
        Uneval ? Sema::ExpressionEvaluationContext::Unevaluated
               : Sema::ExpressionEvaluationContext::ConstantEvaluated,
        /*LambdaContextDecl=*/nullptr, /*ExprContext=*/
        Sema::ExpressionEvaluationContextRecord::EK_TemplateArgument);

    Expr *InputExpr = Input.getSourceExpression();
    if (!InputExpr) InputExpr = Input.getArgument().getAsExpr();

    ExprResult E = getDerived().TransformExpr(InputExpr);
    E = SemaRef.ActOnConstantExpression(E);
    if (E.isInvalid()) return true;
    Output = TemplateArgumentLoc(TemplateArgument(E.get()), E.get());
    return false;
  }
  }

  // Work around bogus GCC warning
  return true;
}

/// Iterator adaptor that invents template argument location information
/// for each of the template arguments in its underlying iterator.
template<typename Derived, typename InputIterator>
class TemplateArgumentLocInventIterator {
  TreeTransform<Derived> &Self;
  InputIterator Iter;

public:
  typedef TemplateArgumentLoc value_type;
  typedef TemplateArgumentLoc reference;
  typedef typename std::iterator_traits<InputIterator>::difference_type
    difference_type;
  typedef std::input_iterator_tag iterator_category;

  class pointer {
    TemplateArgumentLoc Arg;

  public:
    explicit pointer(TemplateArgumentLoc Arg) : Arg(Arg) { }

    const TemplateArgumentLoc *operator->() const { return &Arg; }
  };

  TemplateArgumentLocInventIterator() { }

  explicit TemplateArgumentLocInventIterator(TreeTransform<Derived> &Self,
                                             InputIterator Iter)
    : Self(Self), Iter(Iter) { }

  TemplateArgumentLocInventIterator &operator++() {
    ++Iter;
    return *this;
  }

  TemplateArgumentLocInventIterator operator++(int) {
    TemplateArgumentLocInventIterator Old(*this);
    ++(*this);
    return Old;
  }

  reference operator*() const {
    TemplateArgumentLoc Result;
    Self.InventTemplateArgumentLoc(*Iter, Result);
    return Result;
  }

  pointer operator->() const { return pointer(**this); }

  friend bool operator==(const TemplateArgumentLocInventIterator &X,
                         const TemplateArgumentLocInventIterator &Y) {
    return X.Iter == Y.Iter;
  }

  friend bool operator!=(const TemplateArgumentLocInventIterator &X,
                         const TemplateArgumentLocInventIterator &Y) {
    return X.Iter != Y.Iter;
  }
};

template<typename Derived>
template<typename InputIterator>
bool TreeTransform<Derived>::TransformTemplateArguments(
    InputIterator First, InputIterator Last, TemplateArgumentListInfo &Outputs,
    bool Uneval) {
  for (; First != Last; ++First) {
    TemplateArgumentLoc Out;
    TemplateArgumentLoc In = *First;

    if (In.getArgument().getKind() == TemplateArgument::Pack) {
      // Unpack argument packs, which we translate them into separate
      // arguments.
      // FIXME: We could do much better if we could guarantee that the
      // TemplateArgumentLocInfo for the pack expansion would be usable for
      // all of the template arguments in the argument pack.
      typedef TemplateArgumentLocInventIterator<Derived,
                                                TemplateArgument::pack_iterator>
        PackLocIterator;
      if (TransformTemplateArguments(PackLocIterator(*this,
                                                 In.getArgument().pack_begin()),
                                     PackLocIterator(*this,
                                                   In.getArgument().pack_end()),
                                     Outputs, Uneval))
        return true;

      continue;
    }

    if (In.getArgument().isPackExpansion()) {
      // We have a pack expansion, for which we will be substituting into
      // the pattern.
      SourceLocation Ellipsis;
      Optional<unsigned> OrigNumExpansions;
      TemplateArgumentLoc Pattern
        = getSema().getTemplateArgumentPackExpansionPattern(
              In, Ellipsis, OrigNumExpansions);

      SmallVector<UnexpandedParameterPack, 2> Unexpanded;
      getSema().collectUnexpandedParameterPacks(Pattern, Unexpanded);
      assert(!Unexpanded.empty() && "Pack expansion without parameter packs?");

      // Determine whether the set of unexpanded parameter packs can and should
      // be expanded.
      bool Expand = true;
      bool RetainExpansion = false;
      Optional<unsigned> NumExpansions = OrigNumExpansions;
      if (getDerived().TryExpandParameterPacks(Ellipsis,
                                               Pattern.getSourceRange(),
                                               Unexpanded,
                                               Expand,
                                               RetainExpansion,
                                               NumExpansions))
        return true;

      if (!Expand) {
        // The transform has determined that we should perform a simple
        // transformation on the pack expansion, producing another pack
        // expansion.
        TemplateArgumentLoc OutPattern;
        Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(getSema(), -1);
        if (getDerived().TransformTemplateArgument(Pattern, OutPattern, Uneval))
          return true;

        Out = getDerived().RebuildPackExpansion(OutPattern, Ellipsis,
                                                NumExpansions);
        if (Out.getArgument().isNull())
          return true;

        Outputs.addArgument(Out);
        continue;
      }

      // The transform has determined that we should perform an elementwise
      // expansion of the pattern. Do so.
      for (unsigned I = 0; I != *NumExpansions; ++I) {
        Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(getSema(), I);

        if (getDerived().TransformTemplateArgument(Pattern, Out, Uneval))
          return true;

        if (Out.getArgument().containsUnexpandedParameterPack()) {
          Out = getDerived().RebuildPackExpansion(Out, Ellipsis,
                                                  OrigNumExpansions);
          if (Out.getArgument().isNull())
            return true;
        }

        Outputs.addArgument(Out);
      }

      // If we're supposed to retain a pack expansion, do so by temporarily
      // forgetting the partially-substituted parameter pack.
      if (RetainExpansion) {
        ForgetPartiallySubstitutedPackRAII Forget(getDerived());

        if (getDerived().TransformTemplateArgument(Pattern, Out, Uneval))
          return true;

        Out = getDerived().RebuildPackExpansion(Out, Ellipsis,
                                                OrigNumExpansions);
        if (Out.getArgument().isNull())
          return true;

        Outputs.addArgument(Out);
      }

      continue;
    }

    // The simple case:
    if (getDerived().TransformTemplateArgument(In, Out, Uneval))
      return true;

    Outputs.addArgument(Out);
  }

  return false;

}

//===----------------------------------------------------------------------===//
// Type transformation
//===----------------------------------------------------------------------===//

template<typename Derived>
QualType TreeTransform<Derived>::TransformType(QualType T) {
  if (getDerived().AlreadyTransformed(T))
    return T;

  // Temporary workaround.  All of these transformations should
  // eventually turn into transformations on TypeLocs.
  TypeSourceInfo *DI = getSema().Context.getTrivialTypeSourceInfo(T,
                                                getDerived().getBaseLocation());

  TypeSourceInfo *NewDI = getDerived().TransformType(DI);

  if (!NewDI)
    return QualType();

  return NewDI->getType();
}

template<typename Derived>
TypeSourceInfo *TreeTransform<Derived>::TransformType(TypeSourceInfo *DI) {
  // Refine the base location to the type's location.
  TemporaryBase Rebase(*this, DI->getTypeLoc().getBeginLoc(),
                       getDerived().getBaseEntity());
  if (getDerived().AlreadyTransformed(DI->getType()))
    return DI;

  TypeLocBuilder TLB;

  TypeLoc TL = DI->getTypeLoc();
  TLB.reserve(TL.getFullDataSize());

  QualType Result = getDerived().TransformType(TLB, TL);
  if (Result.isNull())
    return nullptr;

  return TLB.getTypeSourceInfo(SemaRef.Context, Result);
}

template<typename Derived>
QualType
TreeTransform<Derived>::TransformType(TypeLocBuilder &TLB, TypeLoc T) {
  switch (T.getTypeLocClass()) {
#define ABSTRACT_TYPELOC(CLASS, PARENT)
#define TYPELOC(CLASS, PARENT)                                                 \
  case TypeLoc::CLASS:                                                         \
    return getDerived().Transform##CLASS##Type(TLB,                            \
                                               T.castAs<CLASS##TypeLoc>());
#include "clang/AST/TypeLocNodes.def"
  }

  llvm_unreachable("unhandled type loc!");
}

template<typename Derived>
QualType TreeTransform<Derived>::TransformTypeWithDeducedTST(QualType T) {
  if (!isa<DependentNameType>(T))
    return TransformType(T);

  if (getDerived().AlreadyTransformed(T))
    return T;
  TypeSourceInfo *DI = getSema().Context.getTrivialTypeSourceInfo(T,
                                                getDerived().getBaseLocation());
  TypeSourceInfo *NewDI = getDerived().TransformTypeWithDeducedTST(DI);
  return NewDI ? NewDI->getType() : QualType();
}

template<typename Derived>
TypeSourceInfo *
TreeTransform<Derived>::TransformTypeWithDeducedTST(TypeSourceInfo *DI) {
  if (!isa<DependentNameType>(DI->getType()))
    return TransformType(DI);

  // Refine the base location to the type's location.
  TemporaryBase Rebase(*this, DI->getTypeLoc().getBeginLoc(),
                       getDerived().getBaseEntity());
  if (getDerived().AlreadyTransformed(DI->getType()))
    return DI;

  TypeLocBuilder TLB;

  TypeLoc TL = DI->getTypeLoc();
  TLB.reserve(TL.getFullDataSize());

  auto QTL = TL.getAs<QualifiedTypeLoc>();
  if (QTL)
    TL = QTL.getUnqualifiedLoc();

  auto DNTL = TL.castAs<DependentNameTypeLoc>();

  QualType Result = getDerived().TransformDependentNameType(
      TLB, DNTL, /*DeducedTSTContext*/true);
  if (Result.isNull())
    return nullptr;

  if (QTL) {
    Result = getDerived().RebuildQualifiedType(Result, QTL);
    if (Result.isNull())
      return nullptr;
    TLB.TypeWasModifiedSafely(Result);
  }

  return TLB.getTypeSourceInfo(SemaRef.Context, Result);
}

template<typename Derived>
QualType
TreeTransform<Derived>::TransformQualifiedType(TypeLocBuilder &TLB,
                                               QualifiedTypeLoc T) {
  QualType Result = getDerived().TransformType(TLB, T.getUnqualifiedLoc());
  if (Result.isNull())
    return QualType();

  Result = getDerived().RebuildQualifiedType(Result, T);

  if (Result.isNull())
    return QualType();

  // RebuildQualifiedType might have updated the type, but not in a way
  // that invalidates the TypeLoc. (There's no location information for
  // qualifiers.)
  TLB.TypeWasModifiedSafely(Result);

  return Result;
}

template <typename Derived>
QualType TreeTransform<Derived>::RebuildQualifiedType(QualType T,
                                                      QualifiedTypeLoc TL) {

  SourceLocation Loc = TL.getBeginLoc();
  Qualifiers Quals = TL.getType().getLocalQualifiers();

  if (((T.getAddressSpace() != LangAS::Default &&
        Quals.getAddressSpace() != LangAS::Default)) &&
      T.getAddressSpace() != Quals.getAddressSpace()) {
    SemaRef.Diag(Loc, diag::err_address_space_mismatch_templ_inst)
        << TL.getType() << T;
    return QualType();
  }

  // C++ [dcl.fct]p7:
  //   [When] adding cv-qualifications on top of the function type [...] the
  //   cv-qualifiers are ignored.
  if (T->isFunctionType()) {
    T = SemaRef.getASTContext().getAddrSpaceQualType(T,
                                                     Quals.getAddressSpace());
    return T;
  }

  // C++ [dcl.ref]p1:
  //   when the cv-qualifiers are introduced through the use of a typedef-name
  //   or decltype-specifier [...] the cv-qualifiers are ignored.
  // Note that [dcl.ref]p1 lists all cases in which cv-qualifiers can be
  // applied to a reference type.
  if (T->isReferenceType()) {
    // The only qualifier that applies to a reference type is restrict.
    if (!Quals.hasRestrict())
      return T;
    Quals = Qualifiers::fromCVRMask(Qualifiers::Restrict);
  }

  // Suppress Objective-C lifetime qualifiers if they don't make sense for the
  // resulting type.
  if (Quals.hasObjCLifetime()) {
    if (!T->isObjCLifetimeType() && !T->isDependentType())
      Quals.removeObjCLifetime();
    else if (T.getObjCLifetime()) {
      // Objective-C ARC:
      //   A lifetime qualifier applied to a substituted template parameter
      //   overrides the lifetime qualifier from the template argument.
      const AutoType *AutoTy;
      if (const SubstTemplateTypeParmType *SubstTypeParam
                                = dyn_cast<SubstTemplateTypeParmType>(T)) {
        QualType Replacement = SubstTypeParam->getReplacementType();
        Qualifiers Qs = Replacement.getQualifiers();
        Qs.removeObjCLifetime();
        Replacement = SemaRef.Context.getQualifiedType(
            Replacement.getUnqualifiedType(), Qs);
        T = SemaRef.Context.getSubstTemplateTypeParmType(
            SubstTypeParam->getReplacedParameter(), Replacement);
      } else if ((AutoTy = dyn_cast<AutoType>(T)) && AutoTy->isDeduced()) {
        // 'auto' types behave the same way as template parameters.
        QualType Deduced = AutoTy->getDeducedType();
        Qualifiers Qs = Deduced.getQualifiers();
        Qs.removeObjCLifetime();
        Deduced =
            SemaRef.Context.getQualifiedType(Deduced.getUnqualifiedType(), Qs);
        T = SemaRef.Context.getAutoType(Deduced, AutoTy->getKeyword(),
                                        AutoTy->isDependentType());
      } else {
        // Otherwise, complain about the addition of a qualifier to an
        // already-qualified type.
        // FIXME: Why is this check not in Sema::BuildQualifiedType?
        SemaRef.Diag(Loc, diag::err_attr_objc_ownership_redundant) << T;
        Quals.removeObjCLifetime();
      }
    }
  }

  return SemaRef.BuildQualifiedType(T, Loc, Quals);
}

template<typename Derived>
TypeLoc
TreeTransform<Derived>::TransformTypeInObjectScope(TypeLoc TL,
                                                   QualType ObjectType,
                                                   NamedDecl *UnqualLookup,
                                                   CXXScopeSpec &SS) {
  if (getDerived().AlreadyTransformed(TL.getType()))
    return TL;

  TypeSourceInfo *TSI =
      TransformTSIInObjectScope(TL, ObjectType, UnqualLookup, SS);
  if (TSI)
    return TSI->getTypeLoc();
  return TypeLoc();
}

template<typename Derived>
TypeSourceInfo *
TreeTransform<Derived>::TransformTypeInObjectScope(TypeSourceInfo *TSInfo,
                                                   QualType ObjectType,
                                                   NamedDecl *UnqualLookup,
                                                   CXXScopeSpec &SS) {
  if (getDerived().AlreadyTransformed(TSInfo->getType()))
    return TSInfo;

  return TransformTSIInObjectScope(TSInfo->getTypeLoc(), ObjectType,
                                   UnqualLookup, SS);
}

template <typename Derived>
TypeSourceInfo *TreeTransform<Derived>::TransformTSIInObjectScope(
    TypeLoc TL, QualType ObjectType, NamedDecl *UnqualLookup,
    CXXScopeSpec &SS) {
  QualType T = TL.getType();
  assert(!getDerived().AlreadyTransformed(T));

  TypeLocBuilder TLB;
  QualType Result;

  if (isa<TemplateSpecializationType>(T)) {
    TemplateSpecializationTypeLoc SpecTL =
        TL.castAs<TemplateSpecializationTypeLoc>();

    TemplateName Template = getDerived().TransformTemplateName(
        SS, SpecTL.getTypePtr()->getTemplateName(), SpecTL.getTemplateNameLoc(),
        ObjectType, UnqualLookup, /*AllowInjectedClassName*/true);
    if (Template.isNull())
      return nullptr;

    Result = getDerived().TransformTemplateSpecializationType(TLB, SpecTL,
                                                              Template);
  } else if (isa<DependentTemplateSpecializationType>(T)) {
    DependentTemplateSpecializationTypeLoc SpecTL =
        TL.castAs<DependentTemplateSpecializationTypeLoc>();

    TemplateName Template
      = getDerived().RebuildTemplateName(SS,
                                         SpecTL.getTemplateKeywordLoc(),
                                         *SpecTL.getTypePtr()->getIdentifier(),
                                         SpecTL.getTemplateNameLoc(),
                                         ObjectType, UnqualLookup,
                                         /*AllowInjectedClassName*/true);
    if (Template.isNull())
      return nullptr;

    Result = getDerived().TransformDependentTemplateSpecializationType(TLB,
                                                                       SpecTL,
                                                                       Template,
                                                                       SS);
  } else {
    // Nothing special needs to be done for these.
    Result = getDerived().TransformType(TLB, TL);
  }

  if (Result.isNull())
    return nullptr;

  return TLB.getTypeSourceInfo(SemaRef.Context, Result);
}

template <class TyLoc> static inline
QualType TransformTypeSpecType(TypeLocBuilder &TLB, TyLoc T) {
  TyLoc NewT = TLB.push<TyLoc>(T.getType());
  NewT.setNameLoc(T.getNameLoc());
  return T.getType();
}

template<typename Derived>
QualType TreeTransform<Derived>::TransformBuiltinType(TypeLocBuilder &TLB,
                                                      BuiltinTypeLoc T) {
  BuiltinTypeLoc NewT = TLB.push<BuiltinTypeLoc>(T.getType());
  NewT.setBuiltinLoc(T.getBuiltinLoc());
  if (T.needsExtraLocalData())
    NewT.getWrittenBuiltinSpecs() = T.getWrittenBuiltinSpecs();
  return T.getType();
}

template<typename Derived>
QualType TreeTransform<Derived>::TransformComplexType(TypeLocBuilder &TLB,
                                                      ComplexTypeLoc T) {
  // FIXME: recurse?
  return TransformTypeSpecType(TLB, T);
}

template <typename Derived>
QualType TreeTransform<Derived>::TransformAdjustedType(TypeLocBuilder &TLB,
                                                       AdjustedTypeLoc TL) {
  // Adjustments applied during transformation are handled elsewhere.
  return getDerived().TransformType(TLB, TL.getOriginalLoc());
}

template<typename Derived>
QualType TreeTransform<Derived>::TransformDecayedType(TypeLocBuilder &TLB,
                                                      DecayedTypeLoc TL) {
  QualType OriginalType = getDerived().TransformType(TLB, TL.getOriginalLoc());
  if (OriginalType.isNull())
    return QualType();

  QualType Result = TL.getType();
  if (getDerived().AlwaysRebuild() ||
      OriginalType != TL.getOriginalLoc().getType())
    Result = SemaRef.Context.getDecayedType(OriginalType);
  TLB.push<DecayedTypeLoc>(Result);
  // Nothing to set for DecayedTypeLoc.
  return Result;
}

/// Helper to deduce addr space of a pointee type in OpenCL mode.
/// If the type is updated it will be overwritten in PointeeType param.
static void deduceOpenCLPointeeAddrSpace(Sema &SemaRef, QualType &PointeeType) {
  if (PointeeType.getAddressSpace() == LangAS::Default)
    PointeeType = SemaRef.Context.getAddrSpaceQualType(PointeeType,
                                                       LangAS::opencl_generic);
}

template<typename Derived>
QualType TreeTransform<Derived>::TransformPointerType(TypeLocBuilder &TLB,
                                                      PointerTypeLoc TL) {
  QualType PointeeType
    = getDerived().TransformType(TLB, TL.getPointeeLoc());
  if (PointeeType.isNull())
    return QualType();

  if (SemaRef.getLangOpts().OpenCL)
    deduceOpenCLPointeeAddrSpace(SemaRef, PointeeType);

  QualType Result = TL.getType();
  if (PointeeType->getAs<ObjCObjectType>()) {
    // A dependent pointer type 'T *' has is being transformed such
    // that an Objective-C class type is being replaced for 'T'. The
    // resulting pointer type is an ObjCObjectPointerType, not a
    // PointerType.
    Result = SemaRef.Context.getObjCObjectPointerType(PointeeType);

    ObjCObjectPointerTypeLoc NewT = TLB.push<ObjCObjectPointerTypeLoc>(Result);
    NewT.setStarLoc(TL.getStarLoc());
    return Result;
  }

  if (getDerived().AlwaysRebuild() ||
      PointeeType != TL.getPointeeLoc().getType()) {
    Result = getDerived().RebuildPointerType(PointeeType, TL.getSigilLoc());
    if (Result.isNull())
      return QualType();
  }

  // Objective-C ARC can add lifetime qualifiers to the type that we're
  // pointing to.
  TLB.TypeWasModifiedSafely(Result->getPointeeType());

  PointerTypeLoc NewT = TLB.push<PointerTypeLoc>(Result);
  NewT.setSigilLoc(TL.getSigilLoc());
  return Result;
}

template<typename Derived>
QualType
TreeTransform<Derived>::TransformBlockPointerType(TypeLocBuilder &TLB,
                                                  BlockPointerTypeLoc TL) {
  QualType PointeeType
    = getDerived().TransformType(TLB, TL.getPointeeLoc());
  if (PointeeType.isNull())
    return QualType();

  if (SemaRef.getLangOpts().OpenCL)
    deduceOpenCLPointeeAddrSpace(SemaRef, PointeeType);

  QualType Result = TL.getType();
  if (getDerived().AlwaysRebuild() ||
      PointeeType != TL.getPointeeLoc().getType()) {
    Result = getDerived().RebuildBlockPointerType(PointeeType,
                                                  TL.getSigilLoc());
    if (Result.isNull())
      return QualType();
  }

  BlockPointerTypeLoc NewT = TLB.push<BlockPointerTypeLoc>(Result);
  NewT.setSigilLoc(TL.getSigilLoc());
  return Result;
}

/// Transforms a reference type.  Note that somewhat paradoxically we
/// don't care whether the type itself is an l-value type or an r-value
/// type;  we only care if the type was *written* as an l-value type
/// or an r-value type.
template<typename Derived>
QualType
TreeTransform<Derived>::TransformReferenceType(TypeLocBuilder &TLB,
                                               ReferenceTypeLoc TL) {
  const ReferenceType *T = TL.getTypePtr();

  // Note that this works with the pointee-as-written.
  QualType PointeeType = getDerived().TransformType(TLB, TL.getPointeeLoc());
  if (PointeeType.isNull())
    return QualType();

  if (SemaRef.getLangOpts().OpenCL)
    deduceOpenCLPointeeAddrSpace(SemaRef, PointeeType);

  QualType Result = TL.getType();
  if (getDerived().AlwaysRebuild() ||
      PointeeType != T->getPointeeTypeAsWritten()) {
    Result = getDerived().RebuildReferenceType(PointeeType,
                                               T->isSpelledAsLValue(),
                                               TL.getSigilLoc());
    if (Result.isNull())
      return QualType();
  }

  // Objective-C ARC can add lifetime qualifiers to the type that we're
  // referring to.
  TLB.TypeWasModifiedSafely(
      Result->castAs<ReferenceType>()->getPointeeTypeAsWritten());

  // r-value references can be rebuilt as l-value references.
  ReferenceTypeLoc NewTL;
  if (isa<LValueReferenceType>(Result))
    NewTL = TLB.push<LValueReferenceTypeLoc>(Result);
  else
    NewTL = TLB.push<RValueReferenceTypeLoc>(Result);
  NewTL.setSigilLoc(TL.getSigilLoc());

  return Result;
}

template<typename Derived>
QualType
TreeTransform<Derived>::TransformLValueReferenceType(TypeLocBuilder &TLB,
                                                 LValueReferenceTypeLoc TL) {
  return TransformReferenceType(TLB, TL);
}

template<typename Derived>
QualType
TreeTransform<Derived>::TransformRValueReferenceType(TypeLocBuilder &TLB,
                                                 RValueReferenceTypeLoc TL) {
  return TransformReferenceType(TLB, TL);
}

template<typename Derived>
QualType
TreeTransform<Derived>::TransformMemberPointerType(TypeLocBuilder &TLB,
                                                   MemberPointerTypeLoc TL) {
  QualType PointeeType = getDerived().TransformType(TLB, TL.getPointeeLoc());
  if (PointeeType.isNull())
    return QualType();

  TypeSourceInfo* OldClsTInfo = TL.getClassTInfo();
  TypeSourceInfo *NewClsTInfo = nullptr;
  if (OldClsTInfo) {
    NewClsTInfo = getDerived().TransformType(OldClsTInfo);
    if (!NewClsTInfo)
      return QualType();
  }

  const MemberPointerType *T = TL.getTypePtr();
  QualType OldClsType = QualType(T->getClass(), 0);
  QualType NewClsType;
  if (NewClsTInfo)
    NewClsType = NewClsTInfo->getType();
  else {
    NewClsType = getDerived().TransformType(OldClsType);
    if (NewClsType.isNull())
      return QualType();
  }

  QualType Result = TL.getType();
  if (getDerived().AlwaysRebuild() ||
      PointeeType != T->getPointeeType() ||
      NewClsType != OldClsType) {
    Result = getDerived().RebuildMemberPointerType(PointeeType, NewClsType,
                                                   TL.getStarLoc());
    if (Result.isNull())
      return QualType();
  }

  // If we had to adjust the pointee type when building a member pointer, make
  // sure to push TypeLoc info for it.
  const MemberPointerType *MPT = Result->getAs<MemberPointerType>();
  if (MPT && PointeeType != MPT->getPointeeType()) {
    assert(isa<AdjustedType>(MPT->getPointeeType()));
    TLB.push<AdjustedTypeLoc>(MPT->getPointeeType());
  }

  MemberPointerTypeLoc NewTL = TLB.push<MemberPointerTypeLoc>(Result);
  NewTL.setSigilLoc(TL.getSigilLoc());
  NewTL.setClassTInfo(NewClsTInfo);

  return Result;
}

template<typename Derived>
QualType
TreeTransform<Derived>::TransformConstantArrayType(TypeLocBuilder &TLB,
                                                   ConstantArrayTypeLoc TL) {
  const ConstantArrayType *T = TL.getTypePtr();
  QualType ElementType = getDerived().TransformType(TLB, TL.getElementLoc());
  if (ElementType.isNull())
    return QualType();

  // Prefer the expression from the TypeLoc;  the other may have been uniqued.
  Expr *OldSize = TL.getSizeExpr();
  if (!OldSize)
    OldSize = const_cast<Expr*>(T->getSizeExpr());
  Expr *NewSize = nullptr;
  if (OldSize) {
    EnterExpressionEvaluationContext Unevaluated(
        SemaRef, Sema::ExpressionEvaluationContext::ConstantEvaluated);
    NewSize = getDerived().TransformExpr(OldSize).template getAs<Expr>();
    NewSize = SemaRef.ActOnConstantExpression(NewSize).get();
  }

  QualType Result = TL.getType();
  if (getDerived().AlwaysRebuild() ||
      ElementType != T->getElementType() ||
      (T->getSizeExpr() && NewSize != OldSize)) {
    Result = getDerived().RebuildConstantArrayType(ElementType,
                                                   T->getSizeModifier(),
                                                   T->getSize(), NewSize,
                                             T->getIndexTypeCVRQualifiers(),
                                                   TL.getBracketsRange());
    if (Result.isNull())
      return QualType();
  }

  // We might have either a ConstantArrayType or a VariableArrayType now:
  // a ConstantArrayType is allowed to have an element type which is a
  // VariableArrayType if the type is dependent.  Fortunately, all array
  // types have the same location layout.
  ArrayTypeLoc NewTL = TLB.push<ArrayTypeLoc>(Result);
  NewTL.setLBracketLoc(TL.getLBracketLoc());
  NewTL.setRBracketLoc(TL.getRBracketLoc());
  NewTL.setSizeExpr(NewSize);

  return Result;
}

template<typename Derived>
QualType TreeTransform<Derived>::TransformIncompleteArrayType(
                                              TypeLocBuilder &TLB,
                                              IncompleteArrayTypeLoc TL) {
  const IncompleteArrayType *T = TL.getTypePtr();
  QualType ElementType = getDerived().TransformType(TLB, TL.getElementLoc());
  if (ElementType.isNull())
    return QualType();

  QualType Result = TL.getType();
  if (getDerived().AlwaysRebuild() ||
      ElementType != T->getElementType()) {
    Result = getDerived().RebuildIncompleteArrayType(ElementType,
                                                     T->getSizeModifier(),
                                           T->getIndexTypeCVRQualifiers(),
                                                     TL.getBracketsRange());
    if (Result.isNull())
      return QualType();
  }

  IncompleteArrayTypeLoc NewTL = TLB.push<IncompleteArrayTypeLoc>(Result);
  NewTL.setLBracketLoc(TL.getLBracketLoc());
  NewTL.setRBracketLoc(TL.getRBracketLoc());
  NewTL.setSizeExpr(nullptr);

  return Result;
}

template<typename Derived>
QualType
TreeTransform<Derived>::TransformVariableArrayType(TypeLocBuilder &TLB,
                                                   VariableArrayTypeLoc TL) {
  const VariableArrayType *T = TL.getTypePtr();
  QualType ElementType = getDerived().TransformType(TLB, TL.getElementLoc());
  if (ElementType.isNull())
    return QualType();

  ExprResult SizeResult;
  {
    EnterExpressionEvaluationContext Context(
        SemaRef, Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
    SizeResult = getDerived().TransformExpr(T->getSizeExpr());
  }
  if (SizeResult.isInvalid())
    return QualType();
  SizeResult =
      SemaRef.ActOnFinishFullExpr(SizeResult.get(), /*DiscardedValue*/ false);
  if (SizeResult.isInvalid())
    return QualType();

  Expr *Size = SizeResult.get();

  QualType Result = TL.getType();
  if (getDerived().AlwaysRebuild() ||
      ElementType != T->getElementType() ||
      Size != T->getSizeExpr()) {
    Result = getDerived().RebuildVariableArrayType(ElementType,
                                                   T->getSizeModifier(),
                                                   Size,
                                             T->getIndexTypeCVRQualifiers(),
                                                   TL.getBracketsRange());
    if (Result.isNull())
      return QualType();
  }

  // We might have constant size array now, but fortunately it has the same
  // location layout.
  ArrayTypeLoc NewTL = TLB.push<ArrayTypeLoc>(Result);
  NewTL.setLBracketLoc(TL.getLBracketLoc());
  NewTL.setRBracketLoc(TL.getRBracketLoc());
  NewTL.setSizeExpr(Size);

  return Result;
}

template<typename Derived>
QualType
TreeTransform<Derived>::TransformDependentSizedArrayType(TypeLocBuilder &TLB,
                                             DependentSizedArrayTypeLoc TL) {
  const DependentSizedArrayType *T = TL.getTypePtr();
  QualType ElementType = getDerived().TransformType(TLB, TL.getElementLoc());
  if (ElementType.isNull())
    return QualType();

  // Array bounds are constant expressions.
  EnterExpressionEvaluationContext Unevaluated(
      SemaRef, Sema::ExpressionEvaluationContext::ConstantEvaluated);

  // Prefer the expression from the TypeLoc;  the other may have been uniqued.
  Expr *origSize = TL.getSizeExpr();
  if (!origSize) origSize = T->getSizeExpr();

  ExprResult sizeResult
    = getDerived().TransformExpr(origSize);
  sizeResult = SemaRef.ActOnConstantExpression(sizeResult);
  if (sizeResult.isInvalid())
    return QualType();

  Expr *size = sizeResult.get();

  QualType Result = TL.getType();
  if (getDerived().AlwaysRebuild() ||
      ElementType != T->getElementType() ||
      size != origSize) {
    Result = getDerived().RebuildDependentSizedArrayType(ElementType,
                                                         T->getSizeModifier(),
                                                         size,
                                                T->getIndexTypeCVRQualifiers(),
                                                        TL.getBracketsRange());
    if (Result.isNull())
      return QualType();
  }

  // We might have any sort of array type now, but fortunately they
  // all have the same location layout.
  ArrayTypeLoc NewTL = TLB.push<ArrayTypeLoc>(Result);
  NewTL.setLBracketLoc(TL.getLBracketLoc());
  NewTL.setRBracketLoc(TL.getRBracketLoc());
  NewTL.setSizeExpr(size);

  return Result;
}

template <typename Derived>
QualType TreeTransform<Derived>::TransformDependentVectorType(
    TypeLocBuilder &TLB, DependentVectorTypeLoc TL) {
  const DependentVectorType *T = TL.getTypePtr();
  QualType ElementType = getDerived().TransformType(T->getElementType());
  if (ElementType.isNull())
    return QualType();

  EnterExpressionEvaluationContext Unevaluated(
      SemaRef, Sema::ExpressionEvaluationContext::ConstantEvaluated);

  ExprResult Size = getDerived().TransformExpr(T->getSizeExpr());
  Size = SemaRef.ActOnConstantExpression(Size);
  if (Size.isInvalid())
    return QualType();

  QualType Result = TL.getType();
  if (getDerived().AlwaysRebuild() || ElementType != T->getElementType() ||
      Size.get() != T->getSizeExpr()) {
    Result = getDerived().RebuildDependentVectorType(
        ElementType, Size.get(), T->getAttributeLoc(), T->getVectorKind());
    if (Result.isNull())
      return QualType();
  }

  // Result might be dependent or not.
  if (isa<DependentVectorType>(Result)) {
    DependentVectorTypeLoc NewTL =
        TLB.push<DependentVectorTypeLoc>(Result);
    NewTL.setNameLoc(TL.getNameLoc());
  } else {
    VectorTypeLoc NewTL = TLB.push<VectorTypeLoc>(Result);
    NewTL.setNameLoc(TL.getNameLoc());
  }

  return Result;
}

template<typename Derived>
QualType TreeTransform<Derived>::TransformDependentSizedExtVectorType(
                                      TypeLocBuilder &TLB,
                                      DependentSizedExtVectorTypeLoc TL) {
  const DependentSizedExtVectorType *T = TL.getTypePtr();

  // FIXME: ext vector locs should be nested
  QualType ElementType = getDerived().TransformType(T->getElementType());
  if (ElementType.isNull())
    return QualType();

  // Vector sizes are constant expressions.
  EnterExpressionEvaluationContext Unevaluated(
      SemaRef, Sema::ExpressionEvaluationContext::ConstantEvaluated);

  ExprResult Size = getDerived().TransformExpr(T->getSizeExpr());
  Size = SemaRef.ActOnConstantExpression(Size);
  if (Size.isInvalid())
    return QualType();

  QualType Result = TL.getType();
  if (getDerived().AlwaysRebuild() ||
      ElementType != T->getElementType() ||
      Size.get() != T->getSizeExpr()) {
    Result = getDerived().RebuildDependentSizedExtVectorType(ElementType,
                                                             Size.get(),
                                                         T->getAttributeLoc());
    if (Result.isNull())
      return QualType();
  }

  // Result might be dependent or not.
  if (isa<DependentSizedExtVectorType>(Result)) {
    DependentSizedExtVectorTypeLoc NewTL
      = TLB.push<DependentSizedExtVectorTypeLoc>(Result);
    NewTL.setNameLoc(TL.getNameLoc());
  } else {
    ExtVectorTypeLoc NewTL = TLB.push<ExtVectorTypeLoc>(Result);
    NewTL.setNameLoc(TL.getNameLoc());
  }

  return Result;
}

template <typename Derived>
QualType TreeTransform<Derived>::TransformDependentAddressSpaceType(
    TypeLocBuilder &TLB, DependentAddressSpaceTypeLoc TL) {
  const DependentAddressSpaceType *T = TL.getTypePtr();

  QualType pointeeType = getDerived().TransformType(T->getPointeeType());

  if (pointeeType.isNull())
    return QualType();

  // Address spaces are constant expressions.
  EnterExpressionEvaluationContext Unevaluated(
      SemaRef, Sema::ExpressionEvaluationContext::ConstantEvaluated);

  ExprResult AddrSpace = getDerived().TransformExpr(T->getAddrSpaceExpr());
  AddrSpace = SemaRef.ActOnConstantExpression(AddrSpace);
  if (AddrSpace.isInvalid())
    return QualType();

  QualType Result = TL.getType();
  if (getDerived().AlwaysRebuild() || pointeeType != T->getPointeeType() ||
      AddrSpace.get() != T->getAddrSpaceExpr()) {
    Result = getDerived().RebuildDependentAddressSpaceType(
        pointeeType, AddrSpace.get(), T->getAttributeLoc());
    if (Result.isNull())
      return QualType();
  }

  // Result might be dependent or not.
  if (isa<DependentAddressSpaceType>(Result)) {
    DependentAddressSpaceTypeLoc NewTL =
        TLB.push<DependentAddressSpaceTypeLoc>(Result);

    NewTL.setAttrOperandParensRange(TL.getAttrOperandParensRange());
    NewTL.setAttrExprOperand(TL.getAttrExprOperand());
    NewTL.setAttrNameLoc(TL.getAttrNameLoc());

  } else {
    TypeSourceInfo *DI = getSema().Context.getTrivialTypeSourceInfo(
        Result, getDerived().getBaseLocation());
    TransformType(TLB, DI->getTypeLoc());
  }

  return Result;
}

template <typename Derived>
QualType TreeTransform<Derived>::TransformVectorType(TypeLocBuilder &TLB,
                                                     VectorTypeLoc TL) {
  const VectorType *T = TL.getTypePtr();
  QualType ElementType = getDerived().TransformType(T->getElementType());
  if (ElementType.isNull())
    return QualType();

  QualType Result = TL.getType();
  if (getDerived().AlwaysRebuild() ||
      ElementType != T->getElementType()) {
    Result = getDerived().RebuildVectorType(ElementType, T->getNumElements(),
                                            T->getVectorKind());
    if (Result.isNull())
      return QualType();
  }

  VectorTypeLoc NewTL = TLB.push<VectorTypeLoc>(Result);
  NewTL.setNameLoc(TL.getNameLoc());

  return Result;
}

template<typename Derived>
QualType TreeTransform<Derived>::TransformExtVectorType(TypeLocBuilder &TLB,
                                                        ExtVectorTypeLoc TL) {
  const VectorType *T = TL.getTypePtr();
  QualType ElementType = getDerived().TransformType(T->getElementType());
  if (ElementType.isNull())
    return QualType();

  QualType Result = TL.getType();
  if (getDerived().AlwaysRebuild() ||
      ElementType != T->getElementType()) {
    Result = getDerived().RebuildExtVectorType(ElementType,
                                               T->getNumElements(),
                                               /*FIXME*/ SourceLocation());
    if (Result.isNull())
      return QualType();
  }

  ExtVectorTypeLoc NewTL = TLB.push<ExtVectorTypeLoc>(Result);
  NewTL.setNameLoc(TL.getNameLoc());

  return Result;
}

template <typename Derived>
ParmVarDecl *TreeTransform<Derived>::TransformFunctionTypeParam(
    ParmVarDecl *OldParm, int indexAdjustment, Optional<unsigned> NumExpansions,
    bool ExpectParameterPack) {
  TypeSourceInfo *OldDI = OldParm->getTypeSourceInfo();
  TypeSourceInfo *NewDI = nullptr;

  if (NumExpansions && isa<PackExpansionType>(OldDI->getType())) {
    // If we're substituting into a pack expansion type and we know the
    // length we want to expand to, just substitute for the pattern.
    TypeLoc OldTL = OldDI->getTypeLoc();
    PackExpansionTypeLoc OldExpansionTL = OldTL.castAs<PackExpansionTypeLoc>();

    TypeLocBuilder TLB;
    TypeLoc NewTL = OldDI->getTypeLoc();
    TLB.reserve(NewTL.getFullDataSize());

    QualType Result = getDerived().TransformType(TLB,
                                               OldExpansionTL.getPatternLoc());
    if (Result.isNull())
      return nullptr;

    Result = RebuildPackExpansionType(Result,
                                OldExpansionTL.getPatternLoc().getSourceRange(),
                                      OldExpansionTL.getEllipsisLoc(),
                                      NumExpansions);
    if (Result.isNull())
      return nullptr;

    PackExpansionTypeLoc NewExpansionTL
      = TLB.push<PackExpansionTypeLoc>(Result);
    NewExpansionTL.setEllipsisLoc(OldExpansionTL.getEllipsisLoc());
    NewDI = TLB.getTypeSourceInfo(SemaRef.Context, Result);
  } else
    NewDI = getDerived().TransformType(OldDI);
  if (!NewDI)
    return nullptr;

  if (NewDI == OldDI && indexAdjustment == 0)
    return OldParm;

  ParmVarDecl *newParm = ParmVarDecl::Create(SemaRef.Context,
                                             OldParm->getDeclContext(),
                                             OldParm->getInnerLocStart(),
                                             OldParm->getLocation(),
                                             OldParm->getIdentifier(),
                                             NewDI->getType(),
                                             NewDI,
                                             OldParm->getStorageClass(),
                                             /* DefArg */ nullptr);
  newParm->setScopeInfo(OldParm->getFunctionScopeDepth(),
                        OldParm->getFunctionScopeIndex() + indexAdjustment);
  return newParm;
}

template <typename Derived>
bool TreeTransform<Derived>::TransformFunctionTypeParams(
    SourceLocation Loc, ArrayRef<ParmVarDecl *> Params,
    const QualType *ParamTypes,
    const FunctionProtoType::ExtParameterInfo *ParamInfos,
    SmallVectorImpl<QualType> &OutParamTypes,
    SmallVectorImpl<ParmVarDecl *> *PVars,
    Sema::ExtParameterInfoBuilder &PInfos) {
  int indexAdjustment = 0;

  unsigned NumParams = Params.size();
  for (unsigned i = 0; i != NumParams; ++i) {
    if (ParmVarDecl *OldParm = Params[i]) {
      assert(OldParm->getFunctionScopeIndex() == i);

      Optional<unsigned> NumExpansions;
      ParmVarDecl *NewParm = nullptr;
      if (OldParm->isParameterPack()) {
        // We have a function parameter pack that may need to be expanded.
        SmallVector<UnexpandedParameterPack, 2> Unexpanded;

        // Find the parameter packs that could be expanded.
        TypeLoc TL = OldParm->getTypeSourceInfo()->getTypeLoc();
        PackExpansionTypeLoc ExpansionTL = TL.castAs<PackExpansionTypeLoc>();
        TypeLoc Pattern = ExpansionTL.getPatternLoc();
        SemaRef.collectUnexpandedParameterPacks(Pattern, Unexpanded);
        assert(Unexpanded.size() > 0 && "Could not find parameter packs!");

        // Determine whether we should expand the parameter packs.
        bool ShouldExpand = false;
        bool RetainExpansion = false;
        Optional<unsigned> OrigNumExpansions =
            ExpansionTL.getTypePtr()->getNumExpansions();
        NumExpansions = OrigNumExpansions;
        if (getDerived().TryExpandParameterPacks(ExpansionTL.getEllipsisLoc(),
                                                 Pattern.getSourceRange(),
                                                 Unexpanded,
                                                 ShouldExpand,
                                                 RetainExpansion,
                                                 NumExpansions)) {
          return true;
        }

        if (ShouldExpand) {
          // Expand the function parameter pack into multiple, separate
          // parameters.
          getDerived().ExpandingFunctionParameterPack(OldParm);
          for (unsigned I = 0; I != *NumExpansions; ++I) {
            Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(getSema(), I);
            ParmVarDecl *NewParm
              = getDerived().TransformFunctionTypeParam(OldParm,
                                                        indexAdjustment++,
                                                        OrigNumExpansions,
                                                /*ExpectParameterPack=*/false);
            if (!NewParm)
              return true;

            if (ParamInfos)
              PInfos.set(OutParamTypes.size(), ParamInfos[i]);
            OutParamTypes.push_back(NewParm->getType());
            if (PVars)
              PVars->push_back(NewParm);
          }

          // If we're supposed to retain a pack expansion, do so by temporarily
          // forgetting the partially-substituted parameter pack.
          if (RetainExpansion) {
            ForgetPartiallySubstitutedPackRAII Forget(getDerived());
            ParmVarDecl *NewParm
              = getDerived().TransformFunctionTypeParam(OldParm,
                                                        indexAdjustment++,
                                                        OrigNumExpansions,
                                                /*ExpectParameterPack=*/false);
            if (!NewParm)
              return true;

            if (ParamInfos)
              PInfos.set(OutParamTypes.size(), ParamInfos[i]);
            OutParamTypes.push_back(NewParm->getType());
            if (PVars)
              PVars->push_back(NewParm);
          }

          // The next parameter should have the same adjustment as the
          // last thing we pushed, but we post-incremented indexAdjustment
          // on every push.  Also, if we push nothing, the adjustment should
          // go down by one.
          indexAdjustment--;

          // We're done with the pack expansion.
          continue;
        }

        // We'll substitute the parameter now without expanding the pack
        // expansion.
        Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(getSema(), -1);
        NewParm = getDerived().TransformFunctionTypeParam(OldParm,
                                                          indexAdjustment,
                                                          NumExpansions,
                                                  /*ExpectParameterPack=*/true);
      } else {
        NewParm = getDerived().TransformFunctionTypeParam(
            OldParm, indexAdjustment, None, /*ExpectParameterPack=*/ false);
      }

      if (!NewParm)
        return true;

      if (ParamInfos)
        PInfos.set(OutParamTypes.size(), ParamInfos[i]);
      OutParamTypes.push_back(NewParm->getType());
      if (PVars)
        PVars->push_back(NewParm);
      continue;
    }

    // Deal with the possibility that we don't have a parameter
    // declaration for this parameter.
    QualType OldType = ParamTypes[i];
    bool IsPackExpansion = false;
    Optional<unsigned> NumExpansions;
    QualType NewType;
    if (const PackExpansionType *Expansion
                                       = dyn_cast<PackExpansionType>(OldType)) {
      // We have a function parameter pack that may need to be expanded.
      QualType Pattern = Expansion->getPattern();
      SmallVector<UnexpandedParameterPack, 2> Unexpanded;
      getSema().collectUnexpandedParameterPacks(Pattern, Unexpanded);

      // Determine whether we should expand the parameter packs.
      bool ShouldExpand = false;
      bool RetainExpansion = false;
      if (getDerived().TryExpandParameterPacks(Loc, SourceRange(),
                                               Unexpanded,
                                               ShouldExpand,
                                               RetainExpansion,
                                               NumExpansions)) {
        return true;
      }

      if (ShouldExpand) {
        // Expand the function parameter pack into multiple, separate
        // parameters.
        for (unsigned I = 0; I != *NumExpansions; ++I) {
          Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(getSema(), I);
          QualType NewType = getDerived().TransformType(Pattern);
          if (NewType.isNull())
            return true;

          if (NewType->containsUnexpandedParameterPack()) {
            NewType =
                getSema().getASTContext().getPackExpansionType(NewType, None);

            if (NewType.isNull())
              return true;
          }

          if (ParamInfos)
            PInfos.set(OutParamTypes.size(), ParamInfos[i]);
          OutParamTypes.push_back(NewType);
          if (PVars)
            PVars->push_back(nullptr);
        }

        // We're done with the pack expansion.
        continue;
      }

      // If we're supposed to retain a pack expansion, do so by temporarily
      // forgetting the partially-substituted parameter pack.
      if (RetainExpansion) {
        ForgetPartiallySubstitutedPackRAII Forget(getDerived());
        QualType NewType = getDerived().TransformType(Pattern);
        if (NewType.isNull())
          return true;

        if (ParamInfos)
          PInfos.set(OutParamTypes.size(), ParamInfos[i]);
        OutParamTypes.push_back(NewType);
        if (PVars)
          PVars->push_back(nullptr);
      }

      // We'll substitute the parameter now without expanding the pack
      // expansion.
      OldType = Expansion->getPattern();
      IsPackExpansion = true;
      Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(getSema(), -1);
      NewType = getDerived().TransformType(OldType);
    } else {
      NewType = getDerived().TransformType(OldType);
    }

    if (NewType.isNull())
      return true;

    if (IsPackExpansion)
      NewType = getSema().Context.getPackExpansionType(NewType,
                                                       NumExpansions);

    if (ParamInfos)
      PInfos.set(OutParamTypes.size(), ParamInfos[i]);
    OutParamTypes.push_back(NewType);
    if (PVars)
      PVars->push_back(nullptr);
  }

#ifndef NDEBUG
  if (PVars) {
    for (unsigned i = 0, e = PVars->size(); i != e; ++i)
      if (ParmVarDecl *parm = (*PVars)[i])
        assert(parm->getFunctionScopeIndex() == i);
  }
#endif

  return false;
}

template<typename Derived>
QualType
TreeTransform<Derived>::TransformFunctionProtoType(TypeLocBuilder &TLB,
                                                   FunctionProtoTypeLoc TL) {
  SmallVector<QualType, 4> ExceptionStorage;
  TreeTransform *This = this; // Work around gcc.gnu.org/PR56135.
  return getDerived().TransformFunctionProtoType(
      TLB, TL, nullptr, Qualifiers(),
      [&](FunctionProtoType::ExceptionSpecInfo &ESI, bool &Changed) {
        return This->TransformExceptionSpec(TL.getBeginLoc(), ESI,
                                            ExceptionStorage, Changed);
      });
}

template<typename Derived> template<typename Fn>
QualType TreeTransform<Derived>::TransformFunctionProtoType(
    TypeLocBuilder &TLB, FunctionProtoTypeLoc TL, CXXRecordDecl *ThisContext,
    Qualifiers ThisTypeQuals, Fn TransformExceptionSpec) {

  // Transform the parameters and return type.
  //
  // We are required to instantiate the params and return type in source order.
  // When the function has a trailing return type, we instantiate the
  // parameters before the return type,  since the return type can then refer
  // to the parameters themselves (via decltype, sizeof, etc.).
  //
  SmallVector<QualType, 4> ParamTypes;
  SmallVector<ParmVarDecl*, 4> ParamDecls;
  Sema::ExtParameterInfoBuilder ExtParamInfos;
  const FunctionProtoType *T = TL.getTypePtr();

  QualType ResultType;

  if (T->hasTrailingReturn()) {
    if (getDerived().TransformFunctionTypeParams(
            TL.getBeginLoc(), TL.getParams(),
            TL.getTypePtr()->param_type_begin(),
            T->getExtParameterInfosOrNull(),
            ParamTypes, &ParamDecls, ExtParamInfos))
      return QualType();

    {
      // C++11 [expr.prim.general]p3:
      //   If a declaration declares a member function or member function
      //   template of a class X, the expression this is a prvalue of type
      //   "pointer to cv-qualifier-seq X" between the optional cv-qualifer-seq
      //   and the end of the function-definition, member-declarator, or
      //   declarator.
      Sema::CXXThisScopeRAII ThisScope(SemaRef, ThisContext, ThisTypeQuals);

      ResultType = getDerived().TransformType(TLB, TL.getReturnLoc());
      if (ResultType.isNull())
        return QualType();
    }
  }
  else {
    ResultType = getDerived().TransformType(TLB, TL.getReturnLoc());
    if (ResultType.isNull())
      return QualType();

    if (getDerived().TransformFunctionTypeParams(
            TL.getBeginLoc(), TL.getParams(),
            TL.getTypePtr()->param_type_begin(),
            T->getExtParameterInfosOrNull(),
            ParamTypes, &ParamDecls, ExtParamInfos))
      return QualType();
  }

  FunctionProtoType::ExtProtoInfo EPI = T->getExtProtoInfo();

  bool EPIChanged = false;
  if (TransformExceptionSpec(EPI.ExceptionSpec, EPIChanged))
    return QualType();

  // Handle extended parameter information.
  if (auto NewExtParamInfos =
        ExtParamInfos.getPointerOrNull(ParamTypes.size())) {
    if (!EPI.ExtParameterInfos ||
        llvm::makeArrayRef(EPI.ExtParameterInfos, TL.getNumParams())
          != llvm::makeArrayRef(NewExtParamInfos, ParamTypes.size())) {
      EPIChanged = true;
    }
    EPI.ExtParameterInfos = NewExtParamInfos;
  } else if (EPI.ExtParameterInfos) {
    EPIChanged = true;
    EPI.ExtParameterInfos = nullptr;
  }

  QualType Result = TL.getType();
  if (getDerived().AlwaysRebuild() || ResultType != T->getReturnType() ||
      T->getParamTypes() != llvm::makeArrayRef(ParamTypes) || EPIChanged) {
    Result = getDerived().RebuildFunctionProtoType(ResultType, ParamTypes, EPI);
    if (Result.isNull())
      return QualType();
  }

  FunctionProtoTypeLoc NewTL = TLB.push<FunctionProtoTypeLoc>(Result);
  NewTL.setLocalRangeBegin(TL.getLocalRangeBegin());
  NewTL.setLParenLoc(TL.getLParenLoc());
  NewTL.setRParenLoc(TL.getRParenLoc());
  NewTL.setExceptionSpecRange(TL.getExceptionSpecRange());
  NewTL.setLocalRangeEnd(TL.getLocalRangeEnd());
  for (unsigned i = 0, e = NewTL.getNumParams(); i != e; ++i)
    NewTL.setParam(i, ParamDecls[i]);

  return Result;
}

template<typename Derived>
bool TreeTransform<Derived>::TransformExceptionSpec(
    SourceLocation Loc, FunctionProtoType::ExceptionSpecInfo &ESI,
    SmallVectorImpl<QualType> &Exceptions, bool &Changed) {
  assert(ESI.Type != EST_Uninstantiated && ESI.Type != EST_Unevaluated);

  // Instantiate a dynamic noexcept expression, if any.
  if (isComputedNoexcept(ESI.Type)) {
    EnterExpressionEvaluationContext Unevaluated(
        getSema(), Sema::ExpressionEvaluationContext::ConstantEvaluated);
    ExprResult NoexceptExpr = getDerived().TransformExpr(ESI.NoexceptExpr);
    if (NoexceptExpr.isInvalid())
      return true;

    ExceptionSpecificationType EST = ESI.Type;
    NoexceptExpr =
        getSema().ActOnNoexceptSpec(Loc, NoexceptExpr.get(), EST);
    if (NoexceptExpr.isInvalid())
      return true;

    if (ESI.NoexceptExpr != NoexceptExpr.get() || EST != ESI.Type)
      Changed = true;
    ESI.NoexceptExpr = NoexceptExpr.get();
    ESI.Type = EST;
  }

  if (ESI.Type != EST_Dynamic)
    return false;

  // Instantiate a dynamic exception specification's type.
  for (QualType T : ESI.Exceptions) {
    if (const PackExpansionType *PackExpansion =
            T->getAs<PackExpansionType>()) {
      Changed = true;

      // We have a pack expansion. Instantiate it.
      SmallVector<UnexpandedParameterPack, 2> Unexpanded;
      SemaRef.collectUnexpandedParameterPacks(PackExpansion->getPattern(),
                                              Unexpanded);
      assert(!Unexpanded.empty() && "Pack expansion without parameter packs?");

      // Determine whether the set of unexpanded parameter packs can and
      // should
      // be expanded.
      bool Expand = false;
      bool RetainExpansion = false;
      Optional<unsigned> NumExpansions = PackExpansion->getNumExpansions();
      // FIXME: Track the location of the ellipsis (and track source location
      // information for the types in the exception specification in general).
      if (getDerived().TryExpandParameterPacks(
              Loc, SourceRange(), Unexpanded, Expand,
              RetainExpansion, NumExpansions))
        return true;

      if (!Expand) {
        // We can't expand this pack expansion into separate arguments yet;
        // just substitute into the pattern and create a new pack expansion
        // type.
        Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(getSema(), -1);
        QualType U = getDerived().TransformType(PackExpansion->getPattern());
        if (U.isNull())
          return true;

        U = SemaRef.Context.getPackExpansionType(U, NumExpansions);
        Exceptions.push_back(U);
        continue;
      }

      // Substitute into the pack expansion pattern for each slice of the
      // pack.
      for (unsigned ArgIdx = 0; ArgIdx != *NumExpansions; ++ArgIdx) {
        Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(getSema(), ArgIdx);

        QualType U = getDerived().TransformType(PackExpansion->getPattern());
        if