1 //===--- ExprClassification.cpp - Expression AST Node Implementation ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements Expr::classify.
12 //===----------------------------------------------------------------------===//
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;
24 typedef Expr::Classification Cl;
26 static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E);
27 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D);
28 static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T);
29 static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E);
30 static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E);
31 static Cl::Kinds ClassifyConditional(ASTContext &Ctx,
33 const Expr *falseExpr);
34 static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,
35 Cl::Kinds Kind, SourceLocation &Loc);
37 Cl Expr::ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const {
38 assert(!TR->isReferenceType() && "Expressions can't have reference type.");
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())
51 kind = (kind == Cl::CL_LValue ? Cl::CL_AddressableVoid : Cl::CL_Void);
54 // Enable this assertion for testing.
56 case Cl::CL_LValue: assert(getValueKind() == VK_LValue); break;
57 case Cl::CL_XValue: assert(getValueKind() == VK_XValue); break;
60 case Cl::CL_AddressableVoid:
61 case Cl::CL_DuplicateVectorComponents:
62 case Cl::CL_MemberFunction:
63 case Cl::CL_SubObjCPropertySetting:
64 case Cl::CL_ClassTemporary:
65 case Cl::CL_ArrayTemporary:
66 case Cl::CL_ObjCMessageRValue:
67 case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break;
70 Cl::ModifiableType modifiable = Cl::CM_Untested;
72 modifiable = IsModifiable(Ctx, this, kind, *Loc);
73 return Classification(kind, modifiable);
76 /// Classify an expression which creates a temporary, based on its type.
77 static Cl::Kinds ClassifyTemporary(QualType T) {
78 if (T->isRecordType())
79 return Cl::CL_ClassTemporary;
81 return Cl::CL_ArrayTemporary;
83 // No special classification: these don't behave differently from normal
85 return Cl::CL_PRValue;
88 static Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang,
93 return Lang.CPlusPlus ? ClassifyTemporary(E->getType()) : Cl::CL_PRValue;
99 llvm_unreachable("Invalid value category of implicit cast.");
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();
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");
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 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::CXXDependentScopeMemberExprClass:
132 case Expr::DependentScopeDeclRefExprClass:
133 // ObjC instance variables are lvalues
134 // FIXME: ObjC++0x might have different rules
135 case Expr::ObjCIvarRefExprClass:
136 case Expr::FunctionParmPackExprClass:
137 case Expr::MSPropertyRefExprClass:
138 return Cl::CL_LValue;
140 // C99 6.5.2.5p5 says that compound literals are lvalues.
141 // In C++, they're prvalue temporaries.
142 case Expr::CompoundLiteralExprClass:
143 return Ctx.getLangOpts().CPlusPlus ? ClassifyTemporary(E->getType())
146 // Expressions that are prvalues.
147 case Expr::CXXBoolLiteralExprClass:
148 case Expr::CXXPseudoDestructorExprClass:
149 case Expr::UnaryExprOrTypeTraitExprClass:
150 case Expr::CXXNewExprClass:
151 case Expr::CXXThisExprClass:
152 case Expr::CXXNullPtrLiteralExprClass:
153 case Expr::ImaginaryLiteralClass:
154 case Expr::GNUNullExprClass:
155 case Expr::OffsetOfExprClass:
156 case Expr::CXXThrowExprClass:
157 case Expr::ShuffleVectorExprClass:
158 case Expr::IntegerLiteralClass:
159 case Expr::CharacterLiteralClass:
160 case Expr::AddrLabelExprClass:
161 case Expr::CXXDeleteExprClass:
162 case Expr::ImplicitValueInitExprClass:
163 case Expr::BlockExprClass:
164 case Expr::FloatingLiteralClass:
165 case Expr::CXXNoexceptExprClass:
166 case Expr::CXXScalarValueInitExprClass:
167 case Expr::UnaryTypeTraitExprClass:
168 case Expr::BinaryTypeTraitExprClass:
169 case Expr::TypeTraitExprClass:
170 case Expr::ArrayTypeTraitExprClass:
171 case Expr::ExpressionTraitExprClass:
172 case Expr::ObjCSelectorExprClass:
173 case Expr::ObjCProtocolExprClass:
174 case Expr::ObjCStringLiteralClass:
175 case Expr::ObjCBoxedExprClass:
176 case Expr::ObjCArrayLiteralClass:
177 case Expr::ObjCDictionaryLiteralClass:
178 case Expr::ObjCBoolLiteralExprClass:
179 case Expr::ParenListExprClass:
180 case Expr::SizeOfPackExprClass:
181 case Expr::SubstNonTypeTemplateParmPackExprClass:
182 case Expr::AsTypeExprClass:
183 case Expr::ObjCIndirectCopyRestoreExprClass:
184 case Expr::AtomicExprClass:
185 return Cl::CL_PRValue;
187 // Next come the complicated cases.
188 case Expr::SubstNonTypeTemplateParmExprClass:
189 return ClassifyInternal(Ctx,
190 cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement());
192 // C++ [expr.sub]p1: The result is an lvalue of type "T".
193 // However, subscripting vector types is more like member access.
194 case Expr::ArraySubscriptExprClass:
195 if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType())
196 return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase());
197 return Cl::CL_LValue;
199 // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a
200 // function or variable and a prvalue otherwise.
201 case Expr::DeclRefExprClass:
202 if (E->getType() == Ctx.UnknownAnyTy)
203 return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl())
204 ? Cl::CL_PRValue : Cl::CL_LValue;
205 return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl());
207 // Member access is complex.
208 case Expr::MemberExprClass:
209 return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E));
211 case Expr::UnaryOperatorClass:
212 switch (cast<UnaryOperator>(E)->getOpcode()) {
213 // C++ [expr.unary.op]p1: The unary * operator performs indirection:
214 // [...] the result is an lvalue referring to the object or function
215 // to which the expression points.
217 return Cl::CL_LValue;
219 // GNU extensions, simply look through them.
221 return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr());
223 // Treat _Real and _Imag basically as if they were member
224 // expressions: l-value only if the operand is a true l-value.
227 const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens();
228 Cl::Kinds K = ClassifyInternal(Ctx, Op);
229 if (K != Cl::CL_LValue) return K;
231 if (isa<ObjCPropertyRefExpr>(Op))
232 return Cl::CL_SubObjCPropertySetting;
233 return Cl::CL_LValue;
236 // C++ [expr.pre.incr]p1: The result is the updated operand; it is an
241 return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue;
244 return Cl::CL_PRValue;
247 case Expr::OpaqueValueExprClass:
248 return ClassifyExprValueKind(Lang, E, E->getValueKind());
250 // Pseudo-object expressions can produce l-values with reference magic.
251 case Expr::PseudoObjectExprClass:
252 return ClassifyExprValueKind(Lang, E,
253 cast<PseudoObjectExpr>(E)->getValueKind());
255 // Implicit casts are lvalues if they're lvalue casts. Other than that, we
256 // only specifically record class temporaries.
257 case Expr::ImplicitCastExprClass:
258 return ClassifyExprValueKind(Lang, E, E->getValueKind());
260 // C++ [expr.prim.general]p4: The presence of parentheses does not affect
261 // whether the expression is an lvalue.
262 case Expr::ParenExprClass:
263 return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr());
265 // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator,
266 // or a void expression if its result expression is, respectively, an
267 // lvalue, a function designator, or a void expression.
268 case Expr::GenericSelectionExprClass:
269 if (cast<GenericSelectionExpr>(E)->isResultDependent())
270 return Cl::CL_PRValue;
271 return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr());
273 case Expr::BinaryOperatorClass:
274 case Expr::CompoundAssignOperatorClass:
275 // C doesn't have any binary expressions that are lvalues.
277 return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E));
278 return Cl::CL_PRValue;
280 case Expr::CallExprClass:
281 case Expr::CXXOperatorCallExprClass:
282 case Expr::CXXMemberCallExprClass:
283 case Expr::UserDefinedLiteralClass:
284 case Expr::CUDAKernelCallExprClass:
285 return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType());
287 // __builtin_choose_expr is equivalent to the chosen expression.
288 case Expr::ChooseExprClass:
289 return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr(Ctx));
291 // Extended vector element access is an lvalue unless there are duplicates
292 // in the shuffle expression.
293 case Expr::ExtVectorElementExprClass:
294 return cast<ExtVectorElementExpr>(E)->containsDuplicateElements() ?
295 Cl::CL_DuplicateVectorComponents : Cl::CL_LValue;
297 // Simply look at the actual default argument.
298 case Expr::CXXDefaultArgExprClass:
299 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr());
301 // Same idea for default initializers.
302 case Expr::CXXDefaultInitExprClass:
303 return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr());
305 // Same idea for temporary binding.
306 case Expr::CXXBindTemporaryExprClass:
307 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr());
309 // And the cleanups guard.
310 case Expr::ExprWithCleanupsClass:
311 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr());
313 // Casts depend completely on the target type. All casts work the same.
314 case Expr::CStyleCastExprClass:
315 case Expr::CXXFunctionalCastExprClass:
316 case Expr::CXXStaticCastExprClass:
317 case Expr::CXXDynamicCastExprClass:
318 case Expr::CXXReinterpretCastExprClass:
319 case Expr::CXXConstCastExprClass:
320 case Expr::ObjCBridgedCastExprClass:
321 // Only in C++ can casts be interesting at all.
322 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
323 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten());
325 case Expr::CXXUnresolvedConstructExprClass:
326 return ClassifyUnnamed(Ctx,
327 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten());
329 case Expr::BinaryConditionalOperatorClass: {
330 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
331 const BinaryConditionalOperator *co = cast<BinaryConditionalOperator>(E);
332 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
335 case Expr::ConditionalOperatorClass: {
336 // Once again, only C++ is interesting.
337 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
338 const ConditionalOperator *co = cast<ConditionalOperator>(E);
339 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
342 // ObjC message sends are effectively function calls, if the target function
344 case Expr::ObjCMessageExprClass:
345 if (const ObjCMethodDecl *Method =
346 cast<ObjCMessageExpr>(E)->getMethodDecl()) {
347 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getResultType());
348 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind;
350 return Cl::CL_PRValue;
352 // Some C++ expressions are always class temporaries.
353 case Expr::CXXConstructExprClass:
354 case Expr::CXXTemporaryObjectExprClass:
355 case Expr::LambdaExprClass:
356 return Cl::CL_ClassTemporary;
358 case Expr::VAArgExprClass:
359 return ClassifyUnnamed(Ctx, E->getType());
361 case Expr::DesignatedInitExprClass:
362 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit());
364 case Expr::StmtExprClass: {
365 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt();
366 if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back()))
367 return ClassifyUnnamed(Ctx, LastExpr->getType());
368 return Cl::CL_PRValue;
371 case Expr::CXXUuidofExprClass:
372 return Cl::CL_LValue;
374 case Expr::PackExpansionExprClass:
375 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern());
377 case Expr::MaterializeTemporaryExprClass:
378 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference()
382 case Expr::InitListExprClass:
383 // An init list can be an lvalue if it is bound to a reference and
384 // contains only one element. In that case, we look at that element
385 // for an exact classification. Init list creation takes care of the
386 // value kind for us, so we only need to fine-tune.
388 return ClassifyExprValueKind(Lang, E, E->getValueKind());
389 assert(cast<InitListExpr>(E)->getNumInits() == 1 &&
390 "Only 1-element init lists can be glvalues.");
391 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0));
394 llvm_unreachable("unhandled expression kind in classification");
397 /// ClassifyDecl - Return the classification of an expression referencing the
398 /// given declaration.
399 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) {
400 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a
401 // function, variable, or data member and a prvalue otherwise.
402 // In C, functions are not lvalues.
403 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an
404 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to
405 // special-case this.
407 if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance())
408 return Cl::CL_MemberFunction;
411 if (const NonTypeTemplateParmDecl *NTTParm =
412 dyn_cast<NonTypeTemplateParmDecl>(D))
413 islvalue = NTTParm->getType()->isReferenceType();
415 islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) ||
416 isa<IndirectFieldDecl>(D) ||
417 (Ctx.getLangOpts().CPlusPlus &&
418 (isa<FunctionDecl>(D) || isa<FunctionTemplateDecl>(D)));
420 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue;
423 /// ClassifyUnnamed - Return the classification of an expression yielding an
424 /// unnamed value of the given type. This applies in particular to function
426 static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) {
427 // In C, function calls are always rvalues.
428 if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue;
430 // C++ [expr.call]p10: A function call is an lvalue if the result type is an
431 // lvalue reference type or an rvalue reference to function type, an xvalue
432 // if the result type is an rvalue reference to object type, and a prvalue
434 if (T->isLValueReferenceType())
435 return Cl::CL_LValue;
436 const RValueReferenceType *RV = T->getAs<RValueReferenceType>();
437 if (!RV) // Could still be a class temporary, though.
438 return ClassifyTemporary(T);
440 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue;
443 static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) {
444 if (E->getType() == Ctx.UnknownAnyTy)
445 return (isa<FunctionDecl>(E->getMemberDecl())
446 ? Cl::CL_PRValue : Cl::CL_LValue);
448 // Handle C first, it's easier.
449 if (!Ctx.getLangOpts().CPlusPlus) {
451 // For dot access, the expression is an lvalue if the first part is. For
452 // arrow access, it always is an lvalue.
454 return Cl::CL_LValue;
455 // ObjC property accesses are not lvalues, but get special treatment.
456 Expr *Base = E->getBase()->IgnoreParens();
457 if (isa<ObjCPropertyRefExpr>(Base))
458 return Cl::CL_SubObjCPropertySetting;
459 return ClassifyInternal(Ctx, Base);
462 NamedDecl *Member = E->getMemberDecl();
463 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2.
464 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then
465 // E1.E2 is an lvalue.
466 if (ValueDecl *Value = dyn_cast<ValueDecl>(Member))
467 if (Value->getType()->isReferenceType())
468 return Cl::CL_LValue;
470 // Otherwise, one of the following rules applies.
471 // -- If E2 is a static member [...] then E1.E2 is an lvalue.
472 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord())
473 return Cl::CL_LValue;
475 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then
476 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue;
477 // otherwise, it is a prvalue.
478 if (isa<FieldDecl>(Member)) {
481 return Cl::CL_LValue;
482 Expr *Base = E->getBase()->IgnoreParenImpCasts();
483 if (isa<ObjCPropertyRefExpr>(Base))
484 return Cl::CL_SubObjCPropertySetting;
485 return ClassifyInternal(Ctx, E->getBase());
488 // -- If E2 is a [...] member function, [...]
489 // -- If it refers to a static member function [...], then E1.E2 is an
491 // -- Otherwise [...] E1.E2 is a prvalue.
492 if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member))
493 return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction;
495 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue.
496 // So is everything else we haven't handled yet.
497 return Cl::CL_PRValue;
500 static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) {
501 assert(Ctx.getLangOpts().CPlusPlus &&
502 "This is only relevant for C++.");
503 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand.
504 // Except we override this for writes to ObjC properties.
505 if (E->isAssignmentOp())
506 return (E->getLHS()->getObjectKind() == OK_ObjCProperty
507 ? Cl::CL_PRValue : Cl::CL_LValue);
509 // C++ [expr.comma]p1: the result is of the same value category as its right
511 if (E->getOpcode() == BO_Comma)
512 return ClassifyInternal(Ctx, E->getRHS());
514 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand
515 // is a pointer to a data member is of the same value category as its first
517 if (E->getOpcode() == BO_PtrMemD)
518 return (E->getType()->isFunctionType() ||
519 E->hasPlaceholderType(BuiltinType::BoundMember))
520 ? Cl::CL_MemberFunction
521 : ClassifyInternal(Ctx, E->getLHS());
523 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its
524 // second operand is a pointer to data member and a prvalue otherwise.
525 if (E->getOpcode() == BO_PtrMemI)
526 return (E->getType()->isFunctionType() ||
527 E->hasPlaceholderType(BuiltinType::BoundMember))
528 ? Cl::CL_MemberFunction
531 // All other binary operations are prvalues.
532 return Cl::CL_PRValue;
535 static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True,
537 assert(Ctx.getLangOpts().CPlusPlus &&
538 "This is only relevant for C++.");
541 // If either the second or the third operand has type (cv) void, [...]
542 // the result [...] is a prvalue.
543 if (True->getType()->isVoidType() || False->getType()->isVoidType())
544 return Cl::CL_PRValue;
546 // Note that at this point, we have already performed all conversions
547 // according to [expr.cond]p3.
548 // C++ [expr.cond]p4: If the second and third operands are glvalues of the
549 // same value category [...], the result is of that [...] value category.
550 // C++ [expr.cond]p5: Otherwise, the result is a prvalue.
551 Cl::Kinds LCl = ClassifyInternal(Ctx, True),
552 RCl = ClassifyInternal(Ctx, False);
553 return LCl == RCl ? LCl : Cl::CL_PRValue;
556 static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,
557 Cl::Kinds Kind, SourceLocation &Loc) {
558 // As a general rule, we only care about lvalues. But there are some rvalues
559 // for which we want to generate special results.
560 if (Kind == Cl::CL_PRValue) {
561 // For the sake of better diagnostics, we want to specifically recognize
562 // use of the GCC cast-as-lvalue extension.
563 if (const ExplicitCastExpr *CE =
564 dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) {
565 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) {
566 Loc = CE->getExprLoc();
567 return Cl::CM_LValueCast;
571 if (Kind != Cl::CL_LValue)
572 return Cl::CM_RValue;
574 // This is the lvalue case.
575 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6)
576 if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType())
577 return Cl::CM_Function;
579 // Assignment to a property in ObjC is an implicit setter access. But a
580 // setter might not exist.
581 if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) {
582 if (Expr->isImplicitProperty() && Expr->getImplicitPropertySetter() == 0)
583 return Cl::CM_NoSetterProperty;
586 CanQualType CT = Ctx.getCanonicalType(E->getType());
587 // Const stuff is obviously not modifiable.
588 if (CT.isConstQualified())
589 return Cl::CM_ConstQualified;
591 // Arrays are not modifiable, only their elements are.
592 if (CT->isArrayType())
593 return Cl::CM_ArrayType;
594 // Incomplete types are not modifiable.
595 if (CT->isIncompleteType())
596 return Cl::CM_IncompleteType;
598 // Records with any const fields (recursively) are not modifiable.
599 if (const RecordType *R = CT->getAs<RecordType>()) {
600 assert((E->getObjectKind() == OK_ObjCProperty ||
601 !Ctx.getLangOpts().CPlusPlus) &&
602 "C++ struct assignment should be resolved by the "
603 "copy assignment operator.");
604 if (R->hasConstFields())
605 return Cl::CM_ConstQualified;
608 return Cl::CM_Modifiable;
611 Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const {
612 Classification VC = Classify(Ctx);
613 switch (VC.getKind()) {
614 case Cl::CL_LValue: return LV_Valid;
615 case Cl::CL_XValue: return LV_InvalidExpression;
616 case Cl::CL_Function: return LV_NotObjectType;
617 case Cl::CL_Void: return LV_InvalidExpression;
618 case Cl::CL_AddressableVoid: return LV_IncompleteVoidType;
619 case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents;
620 case Cl::CL_MemberFunction: return LV_MemberFunction;
621 case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting;
622 case Cl::CL_ClassTemporary: return LV_ClassTemporary;
623 case Cl::CL_ArrayTemporary: return LV_ArrayTemporary;
624 case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression;
625 case Cl::CL_PRValue: return LV_InvalidExpression;
627 llvm_unreachable("Unhandled kind");
630 Expr::isModifiableLvalueResult
631 Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const {
632 SourceLocation dummy;
633 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy);
634 switch (VC.getKind()) {
635 case Cl::CL_LValue: break;
636 case Cl::CL_XValue: return MLV_InvalidExpression;
637 case Cl::CL_Function: return MLV_NotObjectType;
638 case Cl::CL_Void: return MLV_InvalidExpression;
639 case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType;
640 case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents;
641 case Cl::CL_MemberFunction: return MLV_MemberFunction;
642 case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting;
643 case Cl::CL_ClassTemporary: return MLV_ClassTemporary;
644 case Cl::CL_ArrayTemporary: return MLV_ArrayTemporary;
645 case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression;
647 return VC.getModifiable() == Cl::CM_LValueCast ?
648 MLV_LValueCast : MLV_InvalidExpression;
650 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind");
651 switch (VC.getModifiable()) {
652 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability");
653 case Cl::CM_Modifiable: return MLV_Valid;
654 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match");
655 case Cl::CM_Function: return MLV_NotObjectType;
656 case Cl::CM_LValueCast:
657 llvm_unreachable("CM_LValueCast and CL_LValue don't match");
658 case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty;
659 case Cl::CM_ConstQualified: return MLV_ConstQualified;
660 case Cl::CM_ArrayType: return MLV_ArrayType;
661 case Cl::CM_IncompleteType: return MLV_IncompleteType;
663 llvm_unreachable("Unhandled modifiable type");