clang  6.0.0svn
ExprClassification.cpp
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1 //===--- ExprClassification.cpp - Expression AST Node Implementation ------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements Expr::classify.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "clang/AST/Expr.h"
15 #include "clang/AST/ASTContext.h"
16 #include "clang/AST/DeclCXX.h"
17 #include "clang/AST/DeclObjC.h"
18 #include "clang/AST/DeclTemplate.h"
19 #include "clang/AST/ExprCXX.h"
20 #include "clang/AST/ExprObjC.h"
21 #include "llvm/Support/ErrorHandling.h"
22 using namespace clang;
23 
25 
26 static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E);
27 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D);
29 static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E);
32  const Expr *trueExpr,
33  const Expr *falseExpr);
34 static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,
36 
37 Cl Expr::ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const {
38  assert(!TR->isReferenceType() && "Expressions can't have reference type.");
39 
40  Cl::Kinds kind = ClassifyInternal(Ctx, this);
41  // C99 6.3.2.1: An lvalue is an expression with an object type or an
42  // incomplete type other than void.
43  if (!Ctx.getLangOpts().CPlusPlus) {
44  // Thus, no functions.
45  if (TR->isFunctionType() || TR == Ctx.OverloadTy)
46  kind = Cl::CL_Function;
47  // No void either, but qualified void is OK because it is "other than void".
48  // Void "lvalues" are classified as addressable void values, which are void
49  // expressions whose address can be taken.
50  else if (TR->isVoidType() && !TR.hasQualifiers())
52  }
53 
54  // Enable this assertion for testing.
55  switch (kind) {
56  case Cl::CL_LValue: assert(getValueKind() == VK_LValue); break;
57  case Cl::CL_XValue: assert(getValueKind() == VK_XValue); break;
58  case Cl::CL_Function:
59  case Cl::CL_Void:
67  case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break;
68  }
69 
71  if (Loc)
72  modifiable = IsModifiable(Ctx, this, kind, *Loc);
73  return Classification(kind, modifiable);
74 }
75 
76 /// Classify an expression which creates a temporary, based on its type.
78  if (T->isRecordType())
79  return Cl::CL_ClassTemporary;
80  if (T->isArrayType())
81  return Cl::CL_ArrayTemporary;
82 
83  // No special classification: these don't behave differently from normal
84  // prvalues.
85  return Cl::CL_PRValue;
86 }
87 
89  const Expr *E,
91  switch (Kind) {
92  case VK_RValue:
93  return Lang.CPlusPlus ? ClassifyTemporary(E->getType()) : Cl::CL_PRValue;
94  case VK_LValue:
95  return Cl::CL_LValue;
96  case VK_XValue:
97  return Cl::CL_XValue;
98  }
99  llvm_unreachable("Invalid value category of implicit cast.");
100 }
101 
102 static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) {
103  // This function takes the first stab at classifying expressions.
104  const LangOptions &Lang = Ctx.getLangOpts();
105 
106  switch (E->getStmtClass()) {
107  case Stmt::NoStmtClass:
108 #define ABSTRACT_STMT(Kind)
109 #define STMT(Kind, Base) case Expr::Kind##Class:
110 #define EXPR(Kind, Base)
111 #include "clang/AST/StmtNodes.inc"
112  llvm_unreachable("cannot classify a statement");
113 
114  // First come the expressions that are always lvalues, unconditionally.
115  case Expr::ObjCIsaExprClass:
116  // C++ [expr.prim.general]p1: A string literal is an lvalue.
117  case Expr::StringLiteralClass:
118  // @encode is equivalent to its string
119  case Expr::ObjCEncodeExprClass:
120  // __func__ and friends are too.
121  case Expr::PredefinedExprClass:
122  // Property references are lvalues
123  case Expr::ObjCSubscriptRefExprClass:
124  case Expr::ObjCPropertyRefExprClass:
125  // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of...
126  case Expr::CXXTypeidExprClass:
127  // Unresolved lookups and uncorrected typos get classified as lvalues.
128  // FIXME: Is this wise? Should they get their own kind?
129  case Expr::UnresolvedLookupExprClass:
130  case Expr::UnresolvedMemberExprClass:
131  case Expr::TypoExprClass:
132  case Expr::DependentCoawaitExprClass:
133  case Expr::CXXDependentScopeMemberExprClass:
134  case Expr::DependentScopeDeclRefExprClass:
135  // ObjC instance variables are lvalues
136  // FIXME: ObjC++0x might have different rules
137  case Expr::ObjCIvarRefExprClass:
138  case Expr::FunctionParmPackExprClass:
139  case Expr::MSPropertyRefExprClass:
140  case Expr::MSPropertySubscriptExprClass:
141  case Expr::OMPArraySectionExprClass:
142  return Cl::CL_LValue;
143 
144  // C99 6.5.2.5p5 says that compound literals are lvalues.
145  // In C++, they're prvalue temporaries, except for file-scope arrays.
146  case Expr::CompoundLiteralExprClass:
147  return !E->isLValue() ? ClassifyTemporary(E->getType()) : Cl::CL_LValue;
148 
149  // Expressions that are prvalues.
150  case Expr::CXXBoolLiteralExprClass:
151  case Expr::CXXPseudoDestructorExprClass:
152  case Expr::UnaryExprOrTypeTraitExprClass:
153  case Expr::CXXNewExprClass:
154  case Expr::CXXThisExprClass:
155  case Expr::CXXNullPtrLiteralExprClass:
156  case Expr::ImaginaryLiteralClass:
157  case Expr::GNUNullExprClass:
158  case Expr::OffsetOfExprClass:
159  case Expr::CXXThrowExprClass:
160  case Expr::ShuffleVectorExprClass:
161  case Expr::ConvertVectorExprClass:
162  case Expr::IntegerLiteralClass:
163  case Expr::CharacterLiteralClass:
164  case Expr::AddrLabelExprClass:
165  case Expr::CXXDeleteExprClass:
166  case Expr::ImplicitValueInitExprClass:
167  case Expr::BlockExprClass:
168  case Expr::FloatingLiteralClass:
169  case Expr::CXXNoexceptExprClass:
170  case Expr::CXXScalarValueInitExprClass:
171  case Expr::TypeTraitExprClass:
172  case Expr::ArrayTypeTraitExprClass:
173  case Expr::ExpressionTraitExprClass:
174  case Expr::ObjCSelectorExprClass:
175  case Expr::ObjCProtocolExprClass:
176  case Expr::ObjCStringLiteralClass:
177  case Expr::ObjCBoxedExprClass:
178  case Expr::ObjCArrayLiteralClass:
179  case Expr::ObjCDictionaryLiteralClass:
180  case Expr::ObjCBoolLiteralExprClass:
181  case Expr::ObjCAvailabilityCheckExprClass:
182  case Expr::ParenListExprClass:
183  case Expr::SizeOfPackExprClass:
184  case Expr::SubstNonTypeTemplateParmPackExprClass:
185  case Expr::AsTypeExprClass:
186  case Expr::ObjCIndirectCopyRestoreExprClass:
187  case Expr::AtomicExprClass:
188  case Expr::CXXFoldExprClass:
189  case Expr::ArrayInitLoopExprClass:
190  case Expr::ArrayInitIndexExprClass:
191  case Expr::NoInitExprClass:
192  case Expr::DesignatedInitUpdateExprClass:
193  return Cl::CL_PRValue;
194 
195  // Next come the complicated cases.
196  case Expr::SubstNonTypeTemplateParmExprClass:
197  return ClassifyInternal(Ctx,
198  cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement());
199 
200  // C, C++98 [expr.sub]p1: The result is an lvalue of type "T".
201  // C++11 (DR1213): in the case of an array operand, the result is an lvalue
202  // if that operand is an lvalue and an xvalue otherwise.
203  // Subscripting vector types is more like member access.
204  case Expr::ArraySubscriptExprClass:
205  if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType())
206  return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase());
207  if (Lang.CPlusPlus11) {
208  // Step over the array-to-pointer decay if present, but not over the
209  // temporary materialization.
210  auto *Base = cast<ArraySubscriptExpr>(E)->getBase()->IgnoreImpCasts();
211  if (Base->getType()->isArrayType())
212  return ClassifyInternal(Ctx, Base);
213  }
214  return Cl::CL_LValue;
215 
216  // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a
217  // function or variable and a prvalue otherwise.
218  case Expr::DeclRefExprClass:
219  if (E->getType() == Ctx.UnknownAnyTy)
220  return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl())
222  return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl());
223 
224  // Member access is complex.
225  case Expr::MemberExprClass:
226  return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E));
227 
228  case Expr::UnaryOperatorClass:
229  switch (cast<UnaryOperator>(E)->getOpcode()) {
230  // C++ [expr.unary.op]p1: The unary * operator performs indirection:
231  // [...] the result is an lvalue referring to the object or function
232  // to which the expression points.
233  case UO_Deref:
234  return Cl::CL_LValue;
235 
236  // GNU extensions, simply look through them.
237  case UO_Extension:
238  return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr());
239 
240  // Treat _Real and _Imag basically as if they were member
241  // expressions: l-value only if the operand is a true l-value.
242  case UO_Real:
243  case UO_Imag: {
244  const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens();
245  Cl::Kinds K = ClassifyInternal(Ctx, Op);
246  if (K != Cl::CL_LValue) return K;
247 
248  if (isa<ObjCPropertyRefExpr>(Op))
250  return Cl::CL_LValue;
251  }
252 
253  // C++ [expr.pre.incr]p1: The result is the updated operand; it is an
254  // lvalue, [...]
255  // Not so in C.
256  case UO_PreInc:
257  case UO_PreDec:
258  return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue;
259 
260  default:
261  return Cl::CL_PRValue;
262  }
263 
264  case Expr::OpaqueValueExprClass:
265  return ClassifyExprValueKind(Lang, E, E->getValueKind());
266 
267  // Pseudo-object expressions can produce l-values with reference magic.
268  case Expr::PseudoObjectExprClass:
269  return ClassifyExprValueKind(Lang, E,
270  cast<PseudoObjectExpr>(E)->getValueKind());
271 
272  // Implicit casts are lvalues if they're lvalue casts. Other than that, we
273  // only specifically record class temporaries.
274  case Expr::ImplicitCastExprClass:
275  return ClassifyExprValueKind(Lang, E, E->getValueKind());
276 
277  // C++ [expr.prim.general]p4: The presence of parentheses does not affect
278  // whether the expression is an lvalue.
279  case Expr::ParenExprClass:
280  return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr());
281 
282  // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator,
283  // or a void expression if its result expression is, respectively, an
284  // lvalue, a function designator, or a void expression.
285  case Expr::GenericSelectionExprClass:
286  if (cast<GenericSelectionExpr>(E)->isResultDependent())
287  return Cl::CL_PRValue;
288  return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr());
289 
290  case Expr::BinaryOperatorClass:
291  case Expr::CompoundAssignOperatorClass:
292  // C doesn't have any binary expressions that are lvalues.
293  if (Lang.CPlusPlus)
294  return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E));
295  return Cl::CL_PRValue;
296 
297  case Expr::CallExprClass:
298  case Expr::CXXOperatorCallExprClass:
299  case Expr::CXXMemberCallExprClass:
300  case Expr::UserDefinedLiteralClass:
301  case Expr::CUDAKernelCallExprClass:
302  return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType(Ctx));
303 
304  // __builtin_choose_expr is equivalent to the chosen expression.
305  case Expr::ChooseExprClass:
306  return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr());
307 
308  // Extended vector element access is an lvalue unless there are duplicates
309  // in the shuffle expression.
310  case Expr::ExtVectorElementExprClass:
311  if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements())
313  if (cast<ExtVectorElementExpr>(E)->isArrow())
314  return Cl::CL_LValue;
315  return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase());
316 
317  // Simply look at the actual default argument.
318  case Expr::CXXDefaultArgExprClass:
319  return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr());
320 
321  // Same idea for default initializers.
322  case Expr::CXXDefaultInitExprClass:
323  return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr());
324 
325  // Same idea for temporary binding.
326  case Expr::CXXBindTemporaryExprClass:
327  return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr());
328 
329  // And the cleanups guard.
330  case Expr::ExprWithCleanupsClass:
331  return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr());
332 
333  // Casts depend completely on the target type. All casts work the same.
334  case Expr::CStyleCastExprClass:
335  case Expr::CXXFunctionalCastExprClass:
336  case Expr::CXXStaticCastExprClass:
337  case Expr::CXXDynamicCastExprClass:
338  case Expr::CXXReinterpretCastExprClass:
339  case Expr::CXXConstCastExprClass:
340  case Expr::ObjCBridgedCastExprClass:
341  // Only in C++ can casts be interesting at all.
342  if (!Lang.CPlusPlus) return Cl::CL_PRValue;
343  return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten());
344 
345  case Expr::CXXUnresolvedConstructExprClass:
346  return ClassifyUnnamed(Ctx,
347  cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten());
348 
349  case Expr::BinaryConditionalOperatorClass: {
350  if (!Lang.CPlusPlus) return Cl::CL_PRValue;
351  const BinaryConditionalOperator *co = cast<BinaryConditionalOperator>(E);
352  return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
353  }
354 
355  case Expr::ConditionalOperatorClass: {
356  // Once again, only C++ is interesting.
357  if (!Lang.CPlusPlus) return Cl::CL_PRValue;
358  const ConditionalOperator *co = cast<ConditionalOperator>(E);
359  return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
360  }
361 
362  // ObjC message sends are effectively function calls, if the target function
363  // is known.
364  case Expr::ObjCMessageExprClass:
365  if (const ObjCMethodDecl *Method =
366  cast<ObjCMessageExpr>(E)->getMethodDecl()) {
367  Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getReturnType());
368  return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind;
369  }
370  return Cl::CL_PRValue;
371 
372  // Some C++ expressions are always class temporaries.
373  case Expr::CXXConstructExprClass:
374  case Expr::CXXInheritedCtorInitExprClass:
375  case Expr::CXXTemporaryObjectExprClass:
376  case Expr::LambdaExprClass:
377  case Expr::CXXStdInitializerListExprClass:
378  return Cl::CL_ClassTemporary;
379 
380  case Expr::VAArgExprClass:
381  return ClassifyUnnamed(Ctx, E->getType());
382 
383  case Expr::DesignatedInitExprClass:
384  return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit());
385 
386  case Expr::StmtExprClass: {
387  const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt();
388  if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back()))
389  return ClassifyUnnamed(Ctx, LastExpr->getType());
390  return Cl::CL_PRValue;
391  }
392 
393  case Expr::CXXUuidofExprClass:
394  return Cl::CL_LValue;
395 
396  case Expr::PackExpansionExprClass:
397  return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern());
398 
399  case Expr::MaterializeTemporaryExprClass:
400  return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference()
401  ? Cl::CL_LValue
402  : Cl::CL_XValue;
403 
404  case Expr::InitListExprClass:
405  // An init list can be an lvalue if it is bound to a reference and
406  // contains only one element. In that case, we look at that element
407  // for an exact classification. Init list creation takes care of the
408  // value kind for us, so we only need to fine-tune.
409  if (E->isRValue())
410  return ClassifyExprValueKind(Lang, E, E->getValueKind());
411  assert(cast<InitListExpr>(E)->getNumInits() == 1 &&
412  "Only 1-element init lists can be glvalues.");
413  return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0));
414 
415  case Expr::CoawaitExprClass:
416  case Expr::CoyieldExprClass:
417  return ClassifyInternal(Ctx, cast<CoroutineSuspendExpr>(E)->getResumeExpr());
418  }
419 
420  llvm_unreachable("unhandled expression kind in classification");
421 }
422 
423 /// ClassifyDecl - Return the classification of an expression referencing the
424 /// given declaration.
425 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) {
426  // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a
427  // function, variable, or data member and a prvalue otherwise.
428  // In C, functions are not lvalues.
429  // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an
430  // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to
431  // special-case this.
432 
433  if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance())
434  return Cl::CL_MemberFunction;
435 
436  bool islvalue;
437  if (const NonTypeTemplateParmDecl *NTTParm =
438  dyn_cast<NonTypeTemplateParmDecl>(D))
439  islvalue = NTTParm->getType()->isReferenceType();
440  else
441  islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) ||
442  isa<IndirectFieldDecl>(D) ||
443  isa<BindingDecl>(D) ||
444  (Ctx.getLangOpts().CPlusPlus &&
445  (isa<FunctionDecl>(D) || isa<MSPropertyDecl>(D) ||
446  isa<FunctionTemplateDecl>(D)));
447 
448  return islvalue ? Cl::CL_LValue : Cl::CL_PRValue;
449 }
450 
451 /// ClassifyUnnamed - Return the classification of an expression yielding an
452 /// unnamed value of the given type. This applies in particular to function
453 /// calls and casts.
455  // In C, function calls are always rvalues.
456  if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue;
457 
458  // C++ [expr.call]p10: A function call is an lvalue if the result type is an
459  // lvalue reference type or an rvalue reference to function type, an xvalue
460  // if the result type is an rvalue reference to object type, and a prvalue
461  // otherwise.
462  if (T->isLValueReferenceType())
463  return Cl::CL_LValue;
465  if (!RV) // Could still be a class temporary, though.
466  return ClassifyTemporary(T);
467 
469 }
470 
472  if (E->getType() == Ctx.UnknownAnyTy)
473  return (isa<FunctionDecl>(E->getMemberDecl())
475 
476  // Handle C first, it's easier.
477  if (!Ctx.getLangOpts().CPlusPlus) {
478  // C99 6.5.2.3p3
479  // For dot access, the expression is an lvalue if the first part is. For
480  // arrow access, it always is an lvalue.
481  if (E->isArrow())
482  return Cl::CL_LValue;
483  // ObjC property accesses are not lvalues, but get special treatment.
484  Expr *Base = E->getBase()->IgnoreParens();
485  if (isa<ObjCPropertyRefExpr>(Base))
487  return ClassifyInternal(Ctx, Base);
488  }
489 
490  NamedDecl *Member = E->getMemberDecl();
491  // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2.
492  // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then
493  // E1.E2 is an lvalue.
494  if (ValueDecl *Value = dyn_cast<ValueDecl>(Member))
495  if (Value->getType()->isReferenceType())
496  return Cl::CL_LValue;
497 
498  // Otherwise, one of the following rules applies.
499  // -- If E2 is a static member [...] then E1.E2 is an lvalue.
500  if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord())
501  return Cl::CL_LValue;
502 
503  // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then
504  // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue;
505  // otherwise, it is a prvalue.
506  if (isa<FieldDecl>(Member)) {
507  // *E1 is an lvalue
508  if (E->isArrow())
509  return Cl::CL_LValue;
511  if (isa<ObjCPropertyRefExpr>(Base))
513  return ClassifyInternal(Ctx, E->getBase());
514  }
515 
516  // -- If E2 is a [...] member function, [...]
517  // -- If it refers to a static member function [...], then E1.E2 is an
518  // lvalue; [...]
519  // -- Otherwise [...] E1.E2 is a prvalue.
520  if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member))
521  return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction;
522 
523  // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue.
524  // So is everything else we haven't handled yet.
525  return Cl::CL_PRValue;
526 }
527 
529  assert(Ctx.getLangOpts().CPlusPlus &&
530  "This is only relevant for C++.");
531  // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand.
532  // Except we override this for writes to ObjC properties.
533  if (E->isAssignmentOp())
534  return (E->getLHS()->getObjectKind() == OK_ObjCProperty
536 
537  // C++ [expr.comma]p1: the result is of the same value category as its right
538  // operand, [...].
539  if (E->getOpcode() == BO_Comma)
540  return ClassifyInternal(Ctx, E->getRHS());
541 
542  // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand
543  // is a pointer to a data member is of the same value category as its first
544  // operand.
545  if (E->getOpcode() == BO_PtrMemD)
546  return (E->getType()->isFunctionType() ||
547  E->hasPlaceholderType(BuiltinType::BoundMember))
549  : ClassifyInternal(Ctx, E->getLHS());
550 
551  // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its
552  // second operand is a pointer to data member and a prvalue otherwise.
553  if (E->getOpcode() == BO_PtrMemI)
554  return (E->getType()->isFunctionType() ||
555  E->hasPlaceholderType(BuiltinType::BoundMember))
557  : Cl::CL_LValue;
558 
559  // All other binary operations are prvalues.
560  return Cl::CL_PRValue;
561 }
562 
563 static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True,
564  const Expr *False) {
565  assert(Ctx.getLangOpts().CPlusPlus &&
566  "This is only relevant for C++.");
567 
568  // C++ [expr.cond]p2
569  // If either the second or the third operand has type (cv) void,
570  // one of the following shall hold:
571  if (True->getType()->isVoidType() || False->getType()->isVoidType()) {
572  // The second or the third operand (but not both) is a (possibly
573  // parenthesized) throw-expression; the result is of the [...] value
574  // category of the other.
575  bool TrueIsThrow = isa<CXXThrowExpr>(True->IgnoreParenImpCasts());
576  bool FalseIsThrow = isa<CXXThrowExpr>(False->IgnoreParenImpCasts());
577  if (const Expr *NonThrow = TrueIsThrow ? (FalseIsThrow ? nullptr : False)
578  : (FalseIsThrow ? True : nullptr))
579  return ClassifyInternal(Ctx, NonThrow);
580 
581  // [Otherwise] the result [...] is a prvalue.
582  return Cl::CL_PRValue;
583  }
584 
585  // Note that at this point, we have already performed all conversions
586  // according to [expr.cond]p3.
587  // C++ [expr.cond]p4: If the second and third operands are glvalues of the
588  // same value category [...], the result is of that [...] value category.
589  // C++ [expr.cond]p5: Otherwise, the result is a prvalue.
590  Cl::Kinds LCl = ClassifyInternal(Ctx, True),
591  RCl = ClassifyInternal(Ctx, False);
592  return LCl == RCl ? LCl : Cl::CL_PRValue;
593 }
594 
596  Cl::Kinds Kind, SourceLocation &Loc) {
597  // As a general rule, we only care about lvalues. But there are some rvalues
598  // for which we want to generate special results.
599  if (Kind == Cl::CL_PRValue) {
600  // For the sake of better diagnostics, we want to specifically recognize
601  // use of the GCC cast-as-lvalue extension.
602  if (const ExplicitCastExpr *CE =
603  dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) {
604  if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) {
605  Loc = CE->getExprLoc();
606  return Cl::CM_LValueCast;
607  }
608  }
609  }
610  if (Kind != Cl::CL_LValue)
611  return Cl::CM_RValue;
612 
613  // This is the lvalue case.
614  // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6)
615  if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType())
616  return Cl::CM_Function;
617 
618  // Assignment to a property in ObjC is an implicit setter access. But a
619  // setter might not exist.
620  if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) {
621  if (Expr->isImplicitProperty() &&
622  Expr->getImplicitPropertySetter() == nullptr)
624  }
625 
626  CanQualType CT = Ctx.getCanonicalType(E->getType());
627  // Const stuff is obviously not modifiable.
628  if (CT.isConstQualified())
629  return Cl::CM_ConstQualified;
630  if (Ctx.getLangOpts().OpenCL &&
632  return Cl::CM_ConstAddrSpace;
633 
634  // Arrays are not modifiable, only their elements are.
635  if (CT->isArrayType())
636  return Cl::CM_ArrayType;
637  // Incomplete types are not modifiable.
638  if (CT->isIncompleteType())
639  return Cl::CM_IncompleteType;
640 
641  // Records with any const fields (recursively) are not modifiable.
642  if (const RecordType *R = CT->getAs<RecordType>())
643  if (R->hasConstFields())
645 
646  return Cl::CM_Modifiable;
647 }
648 
650  Classification VC = Classify(Ctx);
651  switch (VC.getKind()) {
652  case Cl::CL_LValue: return LV_Valid;
653  case Cl::CL_XValue: return LV_InvalidExpression;
654  case Cl::CL_Function: return LV_NotObjectType;
655  case Cl::CL_Void: return LV_InvalidExpression;
664  }
665  llvm_unreachable("Unhandled kind");
666 }
667 
670  SourceLocation dummy;
671  Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy);
672  switch (VC.getKind()) {
673  case Cl::CL_LValue: break;
675  case Cl::CL_Function: return MLV_NotObjectType;
676  case Cl::CL_Void: return MLV_InvalidExpression;
684  case Cl::CL_PRValue:
685  return VC.getModifiable() == Cl::CM_LValueCast ?
687  }
688  assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind");
689  switch (VC.getModifiable()) {
690  case Cl::CM_Untested: llvm_unreachable("Did not test modifiability");
691  case Cl::CM_Modifiable: return MLV_Valid;
692  case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match");
693  case Cl::CM_Function: return MLV_NotObjectType;
694  case Cl::CM_LValueCast:
695  llvm_unreachable("CM_LValueCast and CL_LValue don't match");
700  case Cl::CM_ArrayType: return MLV_ArrayType;
702  }
703  llvm_unreachable("Unhandled modifiable type");
704 }
ObjCPropertyRefExpr - A dot-syntax expression to access an ObjC property.
Definition: ExprObjC.h:577
Defines the clang::ASTContext interface.
Stmt * body_back()
Definition: Stmt.h:628
A (possibly-)qualified type.
Definition: Type.h:653
bool isArrayType() const
Definition: Type.h:5993
ValueDecl * getMemberDecl() const
Retrieve the member declaration to which this expression refers.
Definition: Expr.h:2483
bool isConstQualified() const
bool hasPlaceholderType() const
Returns whether this expression has a placeholder type.
Definition: Expr.h:472
bool isRecordType() const
Definition: Type.h:6017
Expr * getBase() const
Definition: Expr.h:2477
Decl - This represents one declaration (or definition), e.g.
Definition: DeclBase.h:86
Defines the C++ template declaration subclasses.
Opcode getOpcode() const
Definition: Expr.h:3026
Classification Classify(ASTContext &Ctx) const
Classify - Classify this expression according to the C++11 expression taxonomy.
Definition: Expr.h:377
isModifiableLvalueResult
Definition: Expr.h:269
static Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang, const Expr *E, ExprValueKind Kind)
const T * getAs() const
Member-template getAs<specific type>&#39;.
Definition: Type.h:6307
ObjCMethodDecl - Represents an instance or class method declaration.
Definition: DeclObjC.h:139
static bool isAssignmentOp(Opcode Opc)
Definition: Expr.h:3108
Defines the clang::Expr interface and subclasses for C++ expressions.
Qualifiers getQualifiers() const
Retrieve all qualifiers.
Expr * getFalseExpr() const
Definition: Expr.h:3312
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:149
LValueClassification ClassifyLValue(ASTContext &Ctx) const
Reasons why an expression might not be an l-value.
static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, Cl::Kinds Kind, SourceLocation &Loc)
bool isReferenceType() const
Definition: Type.h:5956
Classification ClassifyModifiable(ASTContext &Ctx, SourceLocation &Loc) const
ClassifyModifiable - Classify this expression according to the C++11 expression taxonomy, and see if it is valid on the left side of an assignment.
Definition: Expr.h:389
Keeps track of the various options that can be enabled, which controls the dialect of C or C++ that i...
Definition: LangOptions.h:48
Expr::Classification Cl
An r-value expression (a pr-value in the C++11 taxonomy) produces a temporary value.
Definition: Specifiers.h:107
An rvalue reference type, per C++11 [dcl.ref].
Definition: Type.h:2486
An x-value expression is a reference to an object with independent storage but which can be "moved"...
Definition: Specifiers.h:116
ExprValueKind getValueKind() const
getValueKind - The value kind that this expression produces.
Definition: Expr.h:405
A builtin binary operation expression such as "x + y" or "x <= y".
Definition: Expr.h:2985
LangAS getAddressSpace() const
Definition: Type.h:367
bool isArrow() const
Definition: Expr.h:2582
ConditionalOperator - The ?: ternary operator.
Definition: Expr.h:3269
CompoundStmt - This represents a group of statements like { stmt stmt }.
Definition: Stmt.h:595
The return type of classify().
Definition: Expr.h:302
bool hasQualifiers() const
Determine whether this type has any qualifiers.
Definition: Type.h:5795
Kinds
The various classification results. Most of these mean prvalue.
Definition: Expr.h:305
An Objective-C property is a logical field of an Objective-C object which is read and written via Obj...
Definition: Specifiers.h:133
ValueDecl - Represent the declaration of a variable (in which case it is an lvalue) a function (in wh...
Definition: Decl.h:628
Expr - This represents one expression.
Definition: Expr.h:106
QualType getPointeeType() const
Definition: Type.h:2442
ExprValueKind
The categorization of expression values, currently following the C++11 scheme.
Definition: Specifiers.h:104
const FunctionProtoType * T
DeclContext * getDeclContext()
Definition: DeclBase.h:425
NonTypeTemplateParmDecl - Declares a non-type template parameter, e.g., "Size" in.
QualType getType() const
Definition: Expr.h:128
ModifiableType
The results of modification testing.
Definition: Expr.h:320
Expr * getTrueExpr() const
getTrueExpr - Return the subexpression which will be evaluated if the condition evaluates to true; th...
Definition: Expr.h:3394
ExprObjectKind getObjectKind() const
getObjectKind - The object kind that this expression produces.
Definition: Expr.h:412
static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T)
ClassifyUnnamed - Return the classification of an expression yielding an unnamed value of the given t...
static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E)
CanQualType OverloadTy
Definition: ASTContext.h:1013
Kind
Encodes a location in the source.
Represents a static or instance method of a struct/union/class.
Definition: DeclCXX.h:1964
bool isLValue() const
isLValue - True if this expression is an "l-value" according to the rules of the current language...
Definition: Expr.h:249
isModifiableLvalueResult isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc=nullptr) const
isModifiableLvalue - C99 6.3.2.1: an lvalue that does not have array type, does not have an incomplet...
static Cl::Kinds ClassifyTemporary(QualType T)
Classify an expression which creates a temporary, based on its type.
CanProxy< U > getAs() const
Retrieve a canonical type pointer with a different static type, upcasting or downcasting as needed...
Expr * getLHS() const
Definition: Expr.h:3029
static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E)
Expr * getFalseExpr() const
getFalseExpr - Return the subexpression which will be evaluated if the condnition evaluates to false;...
Definition: Expr.h:3401
Dataflow Directional Tag Classes.
ModifiableType getModifiable() const
Definition: Expr.h:348
bool isRecord() const
Definition: DeclBase.h:1405
BinaryOperator::Opcode getOpcode(const SymExpr *SE)
static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D)
ClassifyDecl - Return the classification of an expression referencing the given declaration.
StmtClass getStmtClass() const
Definition: Stmt.h:378
Kinds getKind() const
Definition: Expr.h:347
ExplicitCastExpr - An explicit cast written in the source code.
Definition: Expr.h:2888
static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *trueExpr, const Expr *falseExpr)
Expr * IgnoreParenImpCasts() LLVM_READONLY
IgnoreParenImpCasts - Ignore parentheses and implicit casts.
Definition: Expr.cpp:2550
A helper class that allows the use of isa/cast/dyncast to detect TagType objects of structs/unions/cl...
Definition: Type.h:3978
CanQualType UnknownAnyTy
Definition: ASTContext.h:1013
bool isFunctionType() const
Definition: Type.h:5940
LValueClassification
Definition: Expr.h:254
CanQualType getCanonicalType(QualType T) const
Return the canonical (structural) type corresponding to the specified potentially non-canonical type ...
Definition: ASTContext.h:2174
bool isLValueReferenceType() const
Definition: Type.h:5960
Defines the C++ Decl subclasses, other than those for templates (found in DeclTemplate.h) and friends (in DeclFriend.h).
MemberExpr - [C99 6.5.2.3] Structure and Union Members.
Definition: Expr.h:2387
Expr * getTrueExpr() const
Definition: Expr.h:3307
bool isVoidType() const
Definition: Type.h:6171
BinaryConditionalOperator - The GNU extension to the conditional operator which allows the middle ope...
Definition: Expr.h:3342
bool isRValue() const
Definition: Expr.h:250
unsigned kind
All of the diagnostics that can be emitted by the frontend.
Definition: DiagnosticIDs.h:61
static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E)
Expr * getRHS() const
Definition: Expr.h:3031
An l-value expression is a reference to an object with independent storage.
Definition: Specifiers.h:111
NamedDecl - This represents a decl with a name.
Definition: Decl.h:245
const LangOptions & getLangOpts() const
Definition: ASTContext.h:688
Expr * IgnoreParens() LLVM_READONLY
IgnoreParens - Ignore parentheses.
Definition: Expr.cpp:2432