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 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::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 case Expr::MSPropertyRefExprClass:
139 return Cl::CL_LValue;
141 // C99 6.5.2.5p5 says that compound literals are lvalues.
142 // In C++, they're prvalue temporaries.
143 case Expr::CompoundLiteralExprClass:
144 return Ctx.getLangOpts().CPlusPlus ? ClassifyTemporary(E->getType())
147 // Expressions that are prvalues.
148 case Expr::CXXBoolLiteralExprClass:
149 case Expr::CXXPseudoDestructorExprClass:
150 case Expr::UnaryExprOrTypeTraitExprClass:
151 case Expr::CXXNewExprClass:
152 case Expr::CXXThisExprClass:
153 case Expr::CXXNullPtrLiteralExprClass:
154 case Expr::ImaginaryLiteralClass:
155 case Expr::GNUNullExprClass:
156 case Expr::OffsetOfExprClass:
157 case Expr::CXXThrowExprClass:
158 case Expr::ShuffleVectorExprClass:
159 case Expr::ConvertVectorExprClass:
160 case Expr::IntegerLiteralClass:
161 case Expr::CharacterLiteralClass:
162 case Expr::AddrLabelExprClass:
163 case Expr::CXXDeleteExprClass:
164 case Expr::ImplicitValueInitExprClass:
165 case Expr::BlockExprClass:
166 case Expr::FloatingLiteralClass:
167 case Expr::CXXNoexceptExprClass:
168 case Expr::CXXScalarValueInitExprClass:
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 case Expr::CXXFoldExprClass:
186 case Expr::NoInitExprClass:
187 case Expr::DesignatedInitUpdateExprClass:
188 return Cl::CL_PRValue;
190 // Next come the complicated cases.
191 case Expr::SubstNonTypeTemplateParmExprClass:
192 return ClassifyInternal(Ctx,
193 cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement());
195 // C++ [expr.sub]p1: The result is an lvalue of type "T".
196 // However, subscripting vector types is more like member access.
197 case Expr::ArraySubscriptExprClass:
198 if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType())
199 return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase());
200 return Cl::CL_LValue;
202 // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a
203 // function or variable and a prvalue otherwise.
204 case Expr::DeclRefExprClass:
205 if (E->getType() == Ctx.UnknownAnyTy)
206 return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl())
207 ? Cl::CL_PRValue : Cl::CL_LValue;
208 return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl());
210 // Member access is complex.
211 case Expr::MemberExprClass:
212 return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E));
214 case Expr::UnaryOperatorClass:
215 switch (cast<UnaryOperator>(E)->getOpcode()) {
216 // C++ [expr.unary.op]p1: The unary * operator performs indirection:
217 // [...] the result is an lvalue referring to the object or function
218 // to which the expression points.
220 return Cl::CL_LValue;
222 // GNU extensions, simply look through them.
224 return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr());
226 // Treat _Real and _Imag basically as if they were member
227 // expressions: l-value only if the operand is a true l-value.
230 const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens();
231 Cl::Kinds K = ClassifyInternal(Ctx, Op);
232 if (K != Cl::CL_LValue) return K;
234 if (isa<ObjCPropertyRefExpr>(Op))
235 return Cl::CL_SubObjCPropertySetting;
236 return Cl::CL_LValue;
239 // C++ [expr.pre.incr]p1: The result is the updated operand; it is an
244 return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue;
247 return Cl::CL_PRValue;
250 case Expr::OpaqueValueExprClass:
251 return ClassifyExprValueKind(Lang, E, E->getValueKind());
253 // Pseudo-object expressions can produce l-values with reference magic.
254 case Expr::PseudoObjectExprClass:
255 return ClassifyExprValueKind(Lang, E,
256 cast<PseudoObjectExpr>(E)->getValueKind());
258 // Implicit casts are lvalues if they're lvalue casts. Other than that, we
259 // only specifically record class temporaries.
260 case Expr::ImplicitCastExprClass:
261 return ClassifyExprValueKind(Lang, E, E->getValueKind());
263 // C++ [expr.prim.general]p4: The presence of parentheses does not affect
264 // whether the expression is an lvalue.
265 case Expr::ParenExprClass:
266 return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr());
268 // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator,
269 // or a void expression if its result expression is, respectively, an
270 // lvalue, a function designator, or a void expression.
271 case Expr::GenericSelectionExprClass:
272 if (cast<GenericSelectionExpr>(E)->isResultDependent())
273 return Cl::CL_PRValue;
274 return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr());
276 case Expr::BinaryOperatorClass:
277 case Expr::CompoundAssignOperatorClass:
278 // C doesn't have any binary expressions that are lvalues.
280 return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E));
281 return Cl::CL_PRValue;
283 case Expr::CallExprClass:
284 case Expr::CXXOperatorCallExprClass:
285 case Expr::CXXMemberCallExprClass:
286 case Expr::UserDefinedLiteralClass:
287 case Expr::CUDAKernelCallExprClass:
288 return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType(Ctx));
290 // __builtin_choose_expr is equivalent to the chosen expression.
291 case Expr::ChooseExprClass:
292 return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr());
294 // Extended vector element access is an lvalue unless there are duplicates
295 // in the shuffle expression.
296 case Expr::ExtVectorElementExprClass:
297 if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements())
298 return Cl::CL_DuplicateVectorComponents;
299 if (cast<ExtVectorElementExpr>(E)->isArrow())
300 return Cl::CL_LValue;
301 return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase());
303 // Simply look at the actual default argument.
304 case Expr::CXXDefaultArgExprClass:
305 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr());
307 // Same idea for default initializers.
308 case Expr::CXXDefaultInitExprClass:
309 return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr());
311 // Same idea for temporary binding.
312 case Expr::CXXBindTemporaryExprClass:
313 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr());
315 // And the cleanups guard.
316 case Expr::ExprWithCleanupsClass:
317 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr());
319 // Casts depend completely on the target type. All casts work the same.
320 case Expr::CStyleCastExprClass:
321 case Expr::CXXFunctionalCastExprClass:
322 case Expr::CXXStaticCastExprClass:
323 case Expr::CXXDynamicCastExprClass:
324 case Expr::CXXReinterpretCastExprClass:
325 case Expr::CXXConstCastExprClass:
326 case Expr::ObjCBridgedCastExprClass:
327 // Only in C++ can casts be interesting at all.
328 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
329 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten());
331 case Expr::CXXUnresolvedConstructExprClass:
332 return ClassifyUnnamed(Ctx,
333 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten());
335 case Expr::BinaryConditionalOperatorClass: {
336 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
337 const BinaryConditionalOperator *co = cast<BinaryConditionalOperator>(E);
338 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
341 case Expr::ConditionalOperatorClass: {
342 // Once again, only C++ is interesting.
343 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
344 const ConditionalOperator *co = cast<ConditionalOperator>(E);
345 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
348 // ObjC message sends are effectively function calls, if the target function
350 case Expr::ObjCMessageExprClass:
351 if (const ObjCMethodDecl *Method =
352 cast<ObjCMessageExpr>(E)->getMethodDecl()) {
353 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getReturnType());
354 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind;
356 return Cl::CL_PRValue;
358 // Some C++ expressions are always class temporaries.
359 case Expr::CXXConstructExprClass:
360 case Expr::CXXTemporaryObjectExprClass:
361 case Expr::LambdaExprClass:
362 case Expr::CXXStdInitializerListExprClass:
363 return Cl::CL_ClassTemporary;
365 case Expr::VAArgExprClass:
366 return ClassifyUnnamed(Ctx, E->getType());
368 case Expr::DesignatedInitExprClass:
369 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit());
371 case Expr::StmtExprClass: {
372 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt();
373 if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back()))
374 return ClassifyUnnamed(Ctx, LastExpr->getType());
375 return Cl::CL_PRValue;
378 case Expr::CXXUuidofExprClass:
379 return Cl::CL_LValue;
381 case Expr::PackExpansionExprClass:
382 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern());
384 case Expr::MaterializeTemporaryExprClass:
385 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference()
389 case Expr::InitListExprClass:
390 // An init list can be an lvalue if it is bound to a reference and
391 // contains only one element. In that case, we look at that element
392 // for an exact classification. Init list creation takes care of the
393 // value kind for us, so we only need to fine-tune.
395 return ClassifyExprValueKind(Lang, E, E->getValueKind());
396 assert(cast<InitListExpr>(E)->getNumInits() == 1 &&
397 "Only 1-element init lists can be glvalues.");
398 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0));
401 llvm_unreachable("unhandled expression kind in classification");
404 /// ClassifyDecl - Return the classification of an expression referencing the
405 /// given declaration.
406 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) {
407 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a
408 // function, variable, or data member and a prvalue otherwise.
409 // In C, functions are not lvalues.
410 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an
411 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to
412 // special-case this.
414 if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance())
415 return Cl::CL_MemberFunction;
418 if (const NonTypeTemplateParmDecl *NTTParm =
419 dyn_cast<NonTypeTemplateParmDecl>(D))
420 islvalue = NTTParm->getType()->isReferenceType();
422 islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) ||
423 isa<IndirectFieldDecl>(D) ||
424 (Ctx.getLangOpts().CPlusPlus &&
425 (isa<FunctionDecl>(D) || isa<MSPropertyDecl>(D) ||
426 isa<FunctionTemplateDecl>(D)));
428 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue;
431 /// ClassifyUnnamed - Return the classification of an expression yielding an
432 /// unnamed value of the given type. This applies in particular to function
434 static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) {
435 // In C, function calls are always rvalues.
436 if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue;
438 // C++ [expr.call]p10: A function call is an lvalue if the result type is an
439 // lvalue reference type or an rvalue reference to function type, an xvalue
440 // if the result type is an rvalue reference to object type, and a prvalue
442 if (T->isLValueReferenceType())
443 return Cl::CL_LValue;
444 const RValueReferenceType *RV = T->getAs<RValueReferenceType>();
445 if (!RV) // Could still be a class temporary, though.
446 return ClassifyTemporary(T);
448 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue;
451 static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) {
452 if (E->getType() == Ctx.UnknownAnyTy)
453 return (isa<FunctionDecl>(E->getMemberDecl())
454 ? Cl::CL_PRValue : Cl::CL_LValue);
456 // Handle C first, it's easier.
457 if (!Ctx.getLangOpts().CPlusPlus) {
459 // For dot access, the expression is an lvalue if the first part is. For
460 // arrow access, it always is an lvalue.
462 return Cl::CL_LValue;
463 // ObjC property accesses are not lvalues, but get special treatment.
464 Expr *Base = E->getBase()->IgnoreParens();
465 if (isa<ObjCPropertyRefExpr>(Base))
466 return Cl::CL_SubObjCPropertySetting;
467 return ClassifyInternal(Ctx, Base);
470 NamedDecl *Member = E->getMemberDecl();
471 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2.
472 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then
473 // E1.E2 is an lvalue.
474 if (ValueDecl *Value = dyn_cast<ValueDecl>(Member))
475 if (Value->getType()->isReferenceType())
476 return Cl::CL_LValue;
478 // Otherwise, one of the following rules applies.
479 // -- If E2 is a static member [...] then E1.E2 is an lvalue.
480 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord())
481 return Cl::CL_LValue;
483 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then
484 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue;
485 // otherwise, it is a prvalue.
486 if (isa<FieldDecl>(Member)) {
489 return Cl::CL_LValue;
490 Expr *Base = E->getBase()->IgnoreParenImpCasts();
491 if (isa<ObjCPropertyRefExpr>(Base))
492 return Cl::CL_SubObjCPropertySetting;
493 return ClassifyInternal(Ctx, E->getBase());
496 // -- If E2 is a [...] member function, [...]
497 // -- If it refers to a static member function [...], then E1.E2 is an
499 // -- Otherwise [...] E1.E2 is a prvalue.
500 if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member))
501 return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction;
503 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue.
504 // So is everything else we haven't handled yet.
505 return Cl::CL_PRValue;
508 static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) {
509 assert(Ctx.getLangOpts().CPlusPlus &&
510 "This is only relevant for C++.");
511 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand.
512 // Except we override this for writes to ObjC properties.
513 if (E->isAssignmentOp())
514 return (E->getLHS()->getObjectKind() == OK_ObjCProperty
515 ? Cl::CL_PRValue : Cl::CL_LValue);
517 // C++ [expr.comma]p1: the result is of the same value category as its right
519 if (E->getOpcode() == BO_Comma)
520 return ClassifyInternal(Ctx, E->getRHS());
522 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand
523 // is a pointer to a data member is of the same value category as its first
525 if (E->getOpcode() == BO_PtrMemD)
526 return (E->getType()->isFunctionType() ||
527 E->hasPlaceholderType(BuiltinType::BoundMember))
528 ? Cl::CL_MemberFunction
529 : ClassifyInternal(Ctx, E->getLHS());
531 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its
532 // second operand is a pointer to data member and a prvalue otherwise.
533 if (E->getOpcode() == BO_PtrMemI)
534 return (E->getType()->isFunctionType() ||
535 E->hasPlaceholderType(BuiltinType::BoundMember))
536 ? Cl::CL_MemberFunction
539 // All other binary operations are prvalues.
540 return Cl::CL_PRValue;
543 static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True,
545 assert(Ctx.getLangOpts().CPlusPlus &&
546 "This is only relevant for C++.");
549 // If either the second or the third operand has type (cv) void,
550 // one of the following shall hold:
551 if (True->getType()->isVoidType() || False->getType()->isVoidType()) {
552 // The second or the third operand (but not both) is a (possibly
553 // parenthesized) throw-expression; the result is of the [...] value
554 // category of the other.
555 bool TrueIsThrow = isa<CXXThrowExpr>(True->IgnoreParenImpCasts());
556 bool FalseIsThrow = isa<CXXThrowExpr>(False->IgnoreParenImpCasts());
557 if (const Expr *NonThrow = TrueIsThrow ? (FalseIsThrow ? nullptr : False)
558 : (FalseIsThrow ? True : nullptr))
559 return ClassifyInternal(Ctx, NonThrow);
561 // [Otherwise] the result [...] is a prvalue.
562 return Cl::CL_PRValue;
565 // Note that at this point, we have already performed all conversions
566 // according to [expr.cond]p3.
567 // C++ [expr.cond]p4: If the second and third operands are glvalues of the
568 // same value category [...], the result is of that [...] value category.
569 // C++ [expr.cond]p5: Otherwise, the result is a prvalue.
570 Cl::Kinds LCl = ClassifyInternal(Ctx, True),
571 RCl = ClassifyInternal(Ctx, False);
572 return LCl == RCl ? LCl : Cl::CL_PRValue;
575 static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,
576 Cl::Kinds Kind, SourceLocation &Loc) {
577 // As a general rule, we only care about lvalues. But there are some rvalues
578 // for which we want to generate special results.
579 if (Kind == Cl::CL_PRValue) {
580 // For the sake of better diagnostics, we want to specifically recognize
581 // use of the GCC cast-as-lvalue extension.
582 if (const ExplicitCastExpr *CE =
583 dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) {
584 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) {
585 Loc = CE->getExprLoc();
586 return Cl::CM_LValueCast;
590 if (Kind != Cl::CL_LValue)
591 return Cl::CM_RValue;
593 // This is the lvalue case.
594 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6)
595 if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType())
596 return Cl::CM_Function;
598 // Assignment to a property in ObjC is an implicit setter access. But a
599 // setter might not exist.
600 if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) {
601 if (Expr->isImplicitProperty() &&
602 Expr->getImplicitPropertySetter() == nullptr)
603 return Cl::CM_NoSetterProperty;
606 CanQualType CT = Ctx.getCanonicalType(E->getType());
607 // Const stuff is obviously not modifiable.
608 if (CT.isConstQualified())
609 return Cl::CM_ConstQualified;
610 if (CT.getQualifiers().getAddressSpace() == LangAS::opencl_constant)
611 return Cl::CM_ConstAddrSpace;
613 // Arrays are not modifiable, only their elements are.
614 if (CT->isArrayType())
615 return Cl::CM_ArrayType;
616 // Incomplete types are not modifiable.
617 if (CT->isIncompleteType())
618 return Cl::CM_IncompleteType;
620 // Records with any const fields (recursively) are not modifiable.
621 if (const RecordType *R = CT->getAs<RecordType>())
622 if (R->hasConstFields())
623 return Cl::CM_ConstQualified;
625 return Cl::CM_Modifiable;
628 Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const {
629 Classification VC = Classify(Ctx);
630 switch (VC.getKind()) {
631 case Cl::CL_LValue: return LV_Valid;
632 case Cl::CL_XValue: return LV_InvalidExpression;
633 case Cl::CL_Function: return LV_NotObjectType;
634 case Cl::CL_Void: return LV_InvalidExpression;
635 case Cl::CL_AddressableVoid: return LV_IncompleteVoidType;
636 case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents;
637 case Cl::CL_MemberFunction: return LV_MemberFunction;
638 case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting;
639 case Cl::CL_ClassTemporary: return LV_ClassTemporary;
640 case Cl::CL_ArrayTemporary: return LV_ArrayTemporary;
641 case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression;
642 case Cl::CL_PRValue: return LV_InvalidExpression;
644 llvm_unreachable("Unhandled kind");
647 Expr::isModifiableLvalueResult
648 Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const {
649 SourceLocation dummy;
650 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy);
651 switch (VC.getKind()) {
652 case Cl::CL_LValue: break;
653 case Cl::CL_XValue: return MLV_InvalidExpression;
654 case Cl::CL_Function: return MLV_NotObjectType;
655 case Cl::CL_Void: return MLV_InvalidExpression;
656 case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType;
657 case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents;
658 case Cl::CL_MemberFunction: return MLV_MemberFunction;
659 case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting;
660 case Cl::CL_ClassTemporary: return MLV_ClassTemporary;
661 case Cl::CL_ArrayTemporary: return MLV_ArrayTemporary;
662 case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression;
664 return VC.getModifiable() == Cl::CM_LValueCast ?
665 MLV_LValueCast : MLV_InvalidExpression;
667 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind");
668 switch (VC.getModifiable()) {
669 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability");
670 case Cl::CM_Modifiable: return MLV_Valid;
671 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match");
672 case Cl::CM_Function: return MLV_NotObjectType;
673 case Cl::CM_LValueCast:
674 llvm_unreachable("CM_LValueCast and CL_LValue don't match");
675 case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty;
676 case Cl::CM_ConstQualified: return MLV_ConstQualified;
677 case Cl::CM_ConstAddrSpace: return MLV_ConstAddrSpace;
678 case Cl::CM_ArrayType: return MLV_ArrayType;
679 case Cl::CM_IncompleteType: return MLV_IncompleteType;
681 llvm_unreachable("Unhandled modifiable type");