readability/RedundantCastingCheck.cpp

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//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
 
#include "RedundantCastingCheck.h"
#include "../utils/FixItHintUtils.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/TypeBase.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Lex/Lexer.h"
 
using namespace clang::ast_matchers;
 
namespace clang::tidy::readability {
 
static bool areTypesEqual(QualType S, QualType D) {
  if (S == D)
    return true;
 
  const auto *TS = S->getAs<TypedefType>();
  const auto *TD = D->getAs<TypedefType>();
  if (TS != TD)
    return false;
 
  const QualType PtrS = S->getPointeeType();
  const QualType PtrD = D->getPointeeType();
 
  if (!PtrS.isNull() && !PtrD.isNull())
    return areTypesEqual(PtrS.IgnoreParens(), PtrD.IgnoreParens());
 
  const DeducedType *DT = S->getContainedDeducedType();
  if (DT && DT->isDeduced())
    return D == DT->getDeducedType();
 
  return false;
}
 
static bool areTypesEqual(QualType TypeS, QualType TypeD,
                          bool IgnoreTypeAliases) {
  const QualType CTypeS = TypeS.getCanonicalType();
  const QualType CTypeD = TypeD.getCanonicalType();
  if (CTypeS != CTypeD)
    return false;
 
  return IgnoreTypeAliases || areTypesEqual(TypeS.getLocalUnqualifiedType(),
                                            TypeD.getLocalUnqualifiedType());
}
 
static bool binaryOperatorOperandsTypesEqualToOperatorResultType(
    const Expr *E, bool IgnoreTypeAliases, bool IgnoreImplicitCasts) {
  if (!E)
    return true;
  const Expr *WithoutImplicitAndParen = E->IgnoreParenImpCasts();
  if (!WithoutImplicitAndParen)
    return true;
  if (const auto *B = dyn_cast<BinaryOperator>(WithoutImplicitAndParen)) {
    const QualType Type = WithoutImplicitAndParen->getType();
    if (Type.isNull())
      return true;
 
    const QualType NonReferenceType = Type.getNonReferenceType();
    const QualType LHSType = B->getLHS()->IgnoreImplicit()->getType();
    const QualType RHSType = B->getRHS()->IgnoreImplicit()->getType();
    const bool LHSMatches =
        !LHSType.isNull() && areTypesEqual(LHSType.getNonReferenceType(),
                                           NonReferenceType, IgnoreTypeAliases);
    const bool RHSMatches =
        !RHSType.isNull() && areTypesEqual(RHSType.getNonReferenceType(),
                                           NonReferenceType, IgnoreTypeAliases);
    // Explicit Cast is needed if:
    // IgnoreImplicitCasts = false: neither of operands type matches cast type
    // IgnoreImplicitCasts = true: at least one operand type doesn't match cast
    //                             type
    const bool CastIsNeeded = IgnoreImplicitCasts
                                  ? (!LHSMatches || !RHSMatches)
                                  : (!LHSMatches && !RHSMatches);
    if (CastIsNeeded)
      return false;
  }
  return true;
}
 
static const Decl *getSourceExprDecl(const Expr *SourceExpr) {
  const Expr *CleanSourceExpr = SourceExpr->IgnoreParenImpCasts();
  if (const auto *E = dyn_cast<DeclRefExpr>(CleanSourceExpr))
    return E->getDecl();
 
  if (const auto *E = dyn_cast<CallExpr>(CleanSourceExpr))
    return E->getCalleeDecl();
 
  if (const auto *E = dyn_cast<MemberExpr>(CleanSourceExpr))
    return E->getMemberDecl();
  return nullptr;
}
 
RedundantCastingCheck::RedundantCastingCheck(StringRef Name,
                                             ClangTidyContext *Context)
    : ClangTidyCheck(Name, Context),
      IgnoreMacros(Options.get("IgnoreMacros", true)),
      IgnoreTypeAliases(Options.get("IgnoreTypeAliases", false)),
      IgnoreImplicitCasts(Options.get("IgnoreImplicitCasts", false)) {}
 
void RedundantCastingCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
  Options.store(Opts, "IgnoreMacros", IgnoreMacros);
  Options.store(Opts, "IgnoreTypeAliases", IgnoreTypeAliases);
  Options.store(Opts, "IgnoreImplicitCasts", IgnoreImplicitCasts);
}
 
void RedundantCastingCheck::registerMatchers(MatchFinder *Finder) {
  auto SimpleType = qualType(hasCanonicalType(
      qualType(anyOf(builtinType(), references(builtinType()),
                     references(pointsTo(qualType())), pointsTo(qualType())))));
 
  auto BitfieldMemberExpr = memberExpr(member(fieldDecl(isBitField())));
 
  const ast_matchers::internal::VariadicDynCastAllOfMatcher<
      Stmt, CXXParenListInitExpr>
      cxxParenListInitExpr; // NOLINT(readability-identifier-naming)
 
  Finder->addMatcher(
      explicitCastExpr(
          unless(hasCastKind(CK_ConstructorConversion)),
          unless(hasCastKind(CK_UserDefinedConversion)),
          unless(cxxFunctionalCastExpr(hasDestinationType(unless(SimpleType)))),
 
          hasDestinationType(qualType().bind("dstType")),
          hasSourceExpression(anyOf(
              expr(unless(initListExpr()), unless(BitfieldMemberExpr),
                   unless(cxxParenListInitExpr()),
                   hasType(qualType().bind("srcType")))
                  .bind("source"),
              initListExpr(unless(hasInit(1, expr())),
                           hasInit(0, expr(unless(BitfieldMemberExpr),
                                           hasType(qualType().bind("srcType")))
                                          .bind("source"))))))
          .bind("cast"),
      this);
}
 
void RedundantCastingCheck::check(const MatchFinder::MatchResult &Result) {
  const auto *SourceExpr = Result.Nodes.getNodeAs<Expr>("source");
  auto TypeD = *Result.Nodes.getNodeAs<QualType>("dstType");
 
  if (SourceExpr->getValueKind() == VK_LValue &&
      TypeD.getCanonicalType()->isRValueReferenceType())
    return;
 
  const auto TypeS =
      Result.Nodes.getNodeAs<QualType>("srcType")->getNonReferenceType();
  TypeD = TypeD.getNonReferenceType();
 
  if (!areTypesEqual(TypeS, TypeD, IgnoreTypeAliases))
    return;
 
  if (!binaryOperatorOperandsTypesEqualToOperatorResultType(
          SourceExpr, IgnoreTypeAliases, IgnoreImplicitCasts))
    return;
 
  const auto *CastExpr = Result.Nodes.getNodeAs<ExplicitCastExpr>("cast");
  if (IgnoreMacros &&
      (CastExpr->getBeginLoc().isMacroID() ||
       CastExpr->getEndLoc().isMacroID() || CastExpr->getExprLoc().isMacroID()))
    return;
 
  {
    auto Diag = diag(CastExpr->getExprLoc(),
                     "redundant explicit casting to the same type %0 as the "
                     "sub-expression, remove this casting");
    Diag << TypeD;
 
    const SourceManager &SM = *Result.SourceManager;
    const SourceLocation SourceExprBegin =
        SM.getExpansionLoc(SourceExpr->getBeginLoc());
    const SourceLocation SourceExprEnd =
        SM.getExpansionLoc(SourceExpr->getEndLoc());
 
    if (SourceExprBegin != CastExpr->getBeginLoc())
      Diag << FixItHint::CreateRemoval(SourceRange(
          CastExpr->getBeginLoc(), SourceExprBegin.getLocWithOffset(-1)));
 
    const SourceLocation NextToken = Lexer::getLocForEndOfToken(
        SourceExprEnd, 0U, SM, Result.Context->getLangOpts());
 
    if (SourceExprEnd != CastExpr->getEndLoc()) {
      Diag << FixItHint::CreateRemoval(
          SourceRange(NextToken, CastExpr->getEndLoc()));
    }
 
    if (utils::fixit::areParensNeededForStatement(*SourceExpr)) {
      Diag << FixItHint::CreateInsertion(SourceExprBegin, "(")
           << FixItHint::CreateInsertion(NextToken, ")");
    }
  }
 
  const auto *SourceExprDecl = getSourceExprDecl(SourceExpr);
  if (!SourceExprDecl)
    return;
 
  if (const auto *D = dyn_cast<CXXConstructorDecl>(SourceExprDecl)) {
    diag(D->getLocation(),
         "source type originates from the invocation of this constructor",
         DiagnosticIDs::Note);
    return;
  }
 
  if (const auto *D = dyn_cast<FunctionDecl>(SourceExprDecl)) {
    diag(D->getLocation(),
         "source type originates from the invocation of this "
         "%select{function|method}0",
         DiagnosticIDs::Note)
        << isa<CXXMethodDecl>(D) << D->getReturnTypeSourceRange();
    return;
  }
 
  if (const auto *D = dyn_cast<FieldDecl>(SourceExprDecl)) {
    diag(D->getLocation(),
         "source type originates from referencing this member",
         DiagnosticIDs::Note)
        << SourceRange(D->getTypeSpecStartLoc(), D->getTypeSpecEndLoc());
    return;
  }
 
  if (const auto *D = dyn_cast<ParmVarDecl>(SourceExprDecl)) {
    diag(D->getLocation(),
         "source type originates from referencing this parameter",
         DiagnosticIDs::Note)
        << SourceRange(D->getTypeSpecStartLoc(), D->getTypeSpecEndLoc());
    return;
  }
 
  if (const auto *D = dyn_cast<VarDecl>(SourceExprDecl)) {
    diag(D->getLocation(),
         "source type originates from referencing this variable",
         DiagnosticIDs::Note)
        << SourceRange(D->getTypeSpecStartLoc(), D->getTypeSpecEndLoc());
    return;
  }
 
  if (const auto *D = dyn_cast<EnumConstantDecl>(SourceExprDecl)) {
    diag(D->getLocation(),
         "source type originates from referencing this enum constant",
         DiagnosticIDs::Note);
    return;
  }
 
  if (const auto *D = dyn_cast<BindingDecl>(SourceExprDecl)) {
    diag(D->getLocation(),
         "source type originates from referencing this bound variable",
         DiagnosticIDs::Note);
    return;
  }
 
  if (const auto *D = dyn_cast<NonTypeTemplateParmDecl>(SourceExprDecl)) {
    diag(D->getLocation(),
         "source type originates from referencing this non-type template "
         "parameter",
         DiagnosticIDs::Note);
    return;
  }
}
 
} // namespace clang::tidy::readability