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 "llvm/Support/ErrorHandling.h"
15 #include "clang/AST/Expr.h"
16 #include "clang/AST/ExprCXX.h"
17 #include "clang/AST/ExprObjC.h"
18 #include "clang/AST/ASTContext.h"
19 #include "clang/AST/DeclObjC.h"
20 #include "clang/AST/DeclCXX.h"
21 #include "clang/AST/DeclTemplate.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 static Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang,
42 return Lang.CPlusPlus && E->getType()->isRecordType() ?
43 Cl::CL_ClassTemporary : Cl::CL_PRValue;
49 llvm_unreachable("Invalid value category of implicit cast.");
52 Cl Expr::ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const {
53 assert(!TR->isReferenceType() && "Expressions can't have reference type.");
55 Cl::Kinds kind = ClassifyInternal(Ctx, this);
56 // C99 6.3.2.1: An lvalue is an expression with an object type or an
57 // incomplete type other than void.
58 if (!Ctx.getLangOpts().CPlusPlus) {
59 // Thus, no functions.
60 if (TR->isFunctionType() || TR == Ctx.OverloadTy)
61 kind = Cl::CL_Function;
62 // No void either, but qualified void is OK because it is "other than void".
63 // Void "lvalues" are classified as addressable void values, which are void
64 // expressions whose address can be taken.
65 else if (TR->isVoidType() && !TR.hasQualifiers())
66 kind = (kind == Cl::CL_LValue ? Cl::CL_AddressableVoid : Cl::CL_Void);
69 // Enable this assertion for testing.
71 case Cl::CL_LValue: assert(getValueKind() == VK_LValue); break;
72 case Cl::CL_XValue: assert(getValueKind() == VK_XValue); break;
75 case Cl::CL_AddressableVoid:
76 case Cl::CL_DuplicateVectorComponents:
77 case Cl::CL_MemberFunction:
78 case Cl::CL_SubObjCPropertySetting:
79 case Cl::CL_ClassTemporary:
80 case Cl::CL_ArrayTemporary:
81 case Cl::CL_ObjCMessageRValue:
82 case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break;
85 Cl::ModifiableType modifiable = Cl::CM_Untested;
87 modifiable = IsModifiable(Ctx, this, kind, *Loc);
88 return Classification(kind, modifiable);
91 /// Classify an expression which creates a temporary, based on its type.
92 static Cl::Kinds ClassifyTemporary(QualType T) {
93 if (T->isRecordType())
94 return Cl::CL_ClassTemporary;
96 return Cl::CL_ArrayTemporary;
98 // No special classification: these don't behave differently from normal
100 return Cl::CL_PRValue;
103 static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) {
104 // This function takes the first stab at classifying expressions.
105 const LangOptions &Lang = Ctx.getLangOpts();
107 switch (E->getStmtClass()) {
108 case Stmt::NoStmtClass:
109 #define ABSTRACT_STMT(Kind)
110 #define STMT(Kind, Base) case Expr::Kind##Class:
111 #define EXPR(Kind, Base)
112 #include "clang/AST/StmtNodes.inc"
113 llvm_unreachable("cannot classify a statement");
115 // First come the expressions that are always lvalues, unconditionally.
116 case Expr::ObjCIsaExprClass:
117 // C++ [expr.prim.general]p1: A string literal is an lvalue.
118 case Expr::StringLiteralClass:
119 // @encode is equivalent to its string
120 case Expr::ObjCEncodeExprClass:
121 // __func__ and friends are too.
122 case Expr::PredefinedExprClass:
123 // Property references are lvalues
124 case Expr::ObjCSubscriptRefExprClass:
125 case Expr::ObjCPropertyRefExprClass:
126 // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of...
127 case Expr::CXXTypeidExprClass:
128 // Unresolved lookups get classified as lvalues.
129 // FIXME: Is this wise? Should they get their own kind?
130 case Expr::UnresolvedLookupExprClass:
131 case Expr::UnresolvedMemberExprClass:
132 case Expr::CXXDependentScopeMemberExprClass:
133 case Expr::DependentScopeDeclRefExprClass:
134 // ObjC instance variables are lvalues
135 // FIXME: ObjC++0x might have different rules
136 case Expr::ObjCIvarRefExprClass:
137 case Expr::FunctionParmPackExprClass:
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 temporary binding.
302 case Expr::CXXBindTemporaryExprClass:
303 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr());
305 // And the cleanups guard.
306 case Expr::ExprWithCleanupsClass:
307 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr());
309 // Casts depend completely on the target type. All casts work the same.
310 case Expr::CStyleCastExprClass:
311 case Expr::CXXFunctionalCastExprClass:
312 case Expr::CXXStaticCastExprClass:
313 case Expr::CXXDynamicCastExprClass:
314 case Expr::CXXReinterpretCastExprClass:
315 case Expr::CXXConstCastExprClass:
316 case Expr::ObjCBridgedCastExprClass:
317 // Only in C++ can casts be interesting at all.
318 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
319 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten());
321 case Expr::CXXUnresolvedConstructExprClass:
322 return ClassifyUnnamed(Ctx,
323 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten());
325 case Expr::BinaryConditionalOperatorClass: {
326 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
327 const BinaryConditionalOperator *co = cast<BinaryConditionalOperator>(E);
328 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
331 case Expr::ConditionalOperatorClass: {
332 // Once again, only C++ is interesting.
333 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
334 const ConditionalOperator *co = cast<ConditionalOperator>(E);
335 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
338 // ObjC message sends are effectively function calls, if the target function
340 case Expr::ObjCMessageExprClass:
341 if (const ObjCMethodDecl *Method =
342 cast<ObjCMessageExpr>(E)->getMethodDecl()) {
343 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getResultType());
344 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind;
346 return Cl::CL_PRValue;
348 // Some C++ expressions are always class temporaries.
349 case Expr::CXXConstructExprClass:
350 case Expr::CXXTemporaryObjectExprClass:
351 case Expr::LambdaExprClass:
352 return Cl::CL_ClassTemporary;
354 case Expr::VAArgExprClass:
355 return ClassifyUnnamed(Ctx, E->getType());
357 case Expr::DesignatedInitExprClass:
358 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit());
360 case Expr::StmtExprClass: {
361 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt();
362 if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back()))
363 return ClassifyUnnamed(Ctx, LastExpr->getType());
364 return Cl::CL_PRValue;
367 case Expr::CXXUuidofExprClass:
368 return Cl::CL_LValue;
370 case Expr::PackExpansionExprClass:
371 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern());
373 case Expr::MaterializeTemporaryExprClass:
374 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference()
378 case Expr::InitListExprClass:
379 // An init list can be an lvalue if it is bound to a reference and
380 // contains only one element. In that case, we look at that element
381 // for an exact classification. Init list creation takes care of the
382 // value kind for us, so we only need to fine-tune.
384 return ClassifyExprValueKind(Lang, E, E->getValueKind());
385 assert(cast<InitListExpr>(E)->getNumInits() == 1 &&
386 "Only 1-element init lists can be glvalues.");
387 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0));
390 llvm_unreachable("unhandled expression kind in classification");
393 /// ClassifyDecl - Return the classification of an expression referencing the
394 /// given declaration.
395 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) {
396 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a
397 // function, variable, or data member and a prvalue otherwise.
398 // In C, functions are not lvalues.
399 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an
400 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to
401 // special-case this.
403 if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance())
404 return Cl::CL_MemberFunction;
407 if (const NonTypeTemplateParmDecl *NTTParm =
408 dyn_cast<NonTypeTemplateParmDecl>(D))
409 islvalue = NTTParm->getType()->isReferenceType();
411 islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) ||
412 isa<IndirectFieldDecl>(D) ||
413 (Ctx.getLangOpts().CPlusPlus &&
414 (isa<FunctionDecl>(D) || isa<FunctionTemplateDecl>(D)));
416 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue;
419 /// ClassifyUnnamed - Return the classification of an expression yielding an
420 /// unnamed value of the given type. This applies in particular to function
422 static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) {
423 // In C, function calls are always rvalues.
424 if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue;
426 // C++ [expr.call]p10: A function call is an lvalue if the result type is an
427 // lvalue reference type or an rvalue reference to function type, an xvalue
428 // if the result type is an rvalue reference to object type, and a prvalue
430 if (T->isLValueReferenceType())
431 return Cl::CL_LValue;
432 const RValueReferenceType *RV = T->getAs<RValueReferenceType>();
433 if (!RV) // Could still be a class temporary, though.
434 return ClassifyTemporary(T);
436 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue;
439 static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) {
440 if (E->getType() == Ctx.UnknownAnyTy)
441 return (isa<FunctionDecl>(E->getMemberDecl())
442 ? Cl::CL_PRValue : Cl::CL_LValue);
444 // Handle C first, it's easier.
445 if (!Ctx.getLangOpts().CPlusPlus) {
447 // For dot access, the expression is an lvalue if the first part is. For
448 // arrow access, it always is an lvalue.
450 return Cl::CL_LValue;
451 // ObjC property accesses are not lvalues, but get special treatment.
452 Expr *Base = E->getBase()->IgnoreParens();
453 if (isa<ObjCPropertyRefExpr>(Base))
454 return Cl::CL_SubObjCPropertySetting;
455 return ClassifyInternal(Ctx, Base);
458 NamedDecl *Member = E->getMemberDecl();
459 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2.
460 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then
461 // E1.E2 is an lvalue.
462 if (ValueDecl *Value = dyn_cast<ValueDecl>(Member))
463 if (Value->getType()->isReferenceType())
464 return Cl::CL_LValue;
466 // Otherwise, one of the following rules applies.
467 // -- If E2 is a static member [...] then E1.E2 is an lvalue.
468 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord())
469 return Cl::CL_LValue;
471 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then
472 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue;
473 // otherwise, it is a prvalue.
474 if (isa<FieldDecl>(Member)) {
477 return Cl::CL_LValue;
478 Expr *Base = E->getBase()->IgnoreParenImpCasts();
479 if (isa<ObjCPropertyRefExpr>(Base))
480 return Cl::CL_SubObjCPropertySetting;
481 return ClassifyInternal(Ctx, E->getBase());
484 // -- If E2 is a [...] member function, [...]
485 // -- If it refers to a static member function [...], then E1.E2 is an
487 // -- Otherwise [...] E1.E2 is a prvalue.
488 if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member))
489 return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction;
491 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue.
492 // So is everything else we haven't handled yet.
493 return Cl::CL_PRValue;
496 static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) {
497 assert(Ctx.getLangOpts().CPlusPlus &&
498 "This is only relevant for C++.");
499 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand.
500 // Except we override this for writes to ObjC properties.
501 if (E->isAssignmentOp())
502 return (E->getLHS()->getObjectKind() == OK_ObjCProperty
503 ? Cl::CL_PRValue : Cl::CL_LValue);
505 // C++ [expr.comma]p1: the result is of the same value category as its right
507 if (E->getOpcode() == BO_Comma)
508 return ClassifyInternal(Ctx, E->getRHS());
510 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand
511 // is a pointer to a data member is of the same value category as its first
513 if (E->getOpcode() == BO_PtrMemD)
514 return (E->getType()->isFunctionType() ||
515 E->hasPlaceholderType(BuiltinType::BoundMember))
516 ? Cl::CL_MemberFunction
517 : ClassifyInternal(Ctx, E->getLHS());
519 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its
520 // second operand is a pointer to data member and a prvalue otherwise.
521 if (E->getOpcode() == BO_PtrMemI)
522 return (E->getType()->isFunctionType() ||
523 E->hasPlaceholderType(BuiltinType::BoundMember))
524 ? Cl::CL_MemberFunction
527 // All other binary operations are prvalues.
528 return Cl::CL_PRValue;
531 static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True,
533 assert(Ctx.getLangOpts().CPlusPlus &&
534 "This is only relevant for C++.");
537 // If either the second or the third operand has type (cv) void, [...]
538 // the result [...] is a prvalue.
539 if (True->getType()->isVoidType() || False->getType()->isVoidType())
540 return Cl::CL_PRValue;
542 // Note that at this point, we have already performed all conversions
543 // according to [expr.cond]p3.
544 // C++ [expr.cond]p4: If the second and third operands are glvalues of the
545 // same value category [...], the result is of that [...] value category.
546 // C++ [expr.cond]p5: Otherwise, the result is a prvalue.
547 Cl::Kinds LCl = ClassifyInternal(Ctx, True),
548 RCl = ClassifyInternal(Ctx, False);
549 return LCl == RCl ? LCl : Cl::CL_PRValue;
552 static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,
553 Cl::Kinds Kind, SourceLocation &Loc) {
554 // As a general rule, we only care about lvalues. But there are some rvalues
555 // for which we want to generate special results.
556 if (Kind == Cl::CL_PRValue) {
557 // For the sake of better diagnostics, we want to specifically recognize
558 // use of the GCC cast-as-lvalue extension.
559 if (const ExplicitCastExpr *CE =
560 dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) {
561 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) {
562 Loc = CE->getExprLoc();
563 return Cl::CM_LValueCast;
567 if (Kind != Cl::CL_LValue)
568 return Cl::CM_RValue;
570 // This is the lvalue case.
571 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6)
572 if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType())
573 return Cl::CM_Function;
575 // Assignment to a property in ObjC is an implicit setter access. But a
576 // setter might not exist.
577 if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) {
578 if (Expr->isImplicitProperty() && Expr->getImplicitPropertySetter() == 0)
579 return Cl::CM_NoSetterProperty;
582 CanQualType CT = Ctx.getCanonicalType(E->getType());
583 // Const stuff is obviously not modifiable.
584 if (CT.isConstQualified())
585 return Cl::CM_ConstQualified;
587 // Arrays are not modifiable, only their elements are.
588 if (CT->isArrayType())
589 return Cl::CM_ArrayType;
590 // Incomplete types are not modifiable.
591 if (CT->isIncompleteType())
592 return Cl::CM_IncompleteType;
594 // Records with any const fields (recursively) are not modifiable.
595 if (const RecordType *R = CT->getAs<RecordType>()) {
596 assert((E->getObjectKind() == OK_ObjCProperty ||
597 !Ctx.getLangOpts().CPlusPlus) &&
598 "C++ struct assignment should be resolved by the "
599 "copy assignment operator.");
600 if (R->hasConstFields())
601 return Cl::CM_ConstQualified;
604 return Cl::CM_Modifiable;
607 Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const {
608 Classification VC = Classify(Ctx);
609 switch (VC.getKind()) {
610 case Cl::CL_LValue: return LV_Valid;
611 case Cl::CL_XValue: return LV_InvalidExpression;
612 case Cl::CL_Function: return LV_NotObjectType;
613 case Cl::CL_Void: return LV_InvalidExpression;
614 case Cl::CL_AddressableVoid: return LV_IncompleteVoidType;
615 case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents;
616 case Cl::CL_MemberFunction: return LV_MemberFunction;
617 case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting;
618 case Cl::CL_ClassTemporary: return LV_ClassTemporary;
619 case Cl::CL_ArrayTemporary: return LV_ArrayTemporary;
620 case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression;
621 case Cl::CL_PRValue: return LV_InvalidExpression;
623 llvm_unreachable("Unhandled kind");
626 Expr::isModifiableLvalueResult
627 Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const {
628 SourceLocation dummy;
629 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy);
630 switch (VC.getKind()) {
631 case Cl::CL_LValue: break;
632 case Cl::CL_XValue: return MLV_InvalidExpression;
633 case Cl::CL_Function: return MLV_NotObjectType;
634 case Cl::CL_Void: return MLV_InvalidExpression;
635 case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType;
636 case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents;
637 case Cl::CL_MemberFunction: return MLV_MemberFunction;
638 case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting;
639 case Cl::CL_ClassTemporary: return MLV_ClassTemporary;
640 case Cl::CL_ArrayTemporary: return MLV_ArrayTemporary;
641 case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression;
643 return VC.getModifiable() == Cl::CM_LValueCast ?
644 MLV_LValueCast : MLV_InvalidExpression;
646 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind");
647 switch (VC.getModifiable()) {
648 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability");
649 case Cl::CM_Modifiable: return MLV_Valid;
650 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match");
651 case Cl::CM_Function: return MLV_NotObjectType;
652 case Cl::CM_LValueCast:
653 llvm_unreachable("CM_LValueCast and CL_LValue don't match");
654 case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty;
655 case Cl::CM_ConstQualified: return MLV_ConstQualified;
656 case Cl::CM_ArrayType: return MLV_ArrayType;
657 case Cl::CM_IncompleteType: return MLV_IncompleteType;
659 llvm_unreachable("Unhandled modifiable type");