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 case Expr::MSPropertySubscriptExprClass:
140 case Expr::OMPArraySectionExprClass:
141 return Cl::CL_LValue;
143 // C99 6.5.2.5p5 says that compound literals are lvalues.
144 // In C++, they're prvalue temporaries.
145 case Expr::CompoundLiteralExprClass:
146 return Ctx.getLangOpts().CPlusPlus ? ClassifyTemporary(E->getType())
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::NoInitExprClass:
190 case Expr::DesignatedInitUpdateExprClass:
191 case Expr::CoyieldExprClass:
192 return Cl::CL_PRValue;
194 // Next come the complicated cases.
195 case Expr::SubstNonTypeTemplateParmExprClass:
196 return ClassifyInternal(Ctx,
197 cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement());
199 // C++ [expr.sub]p1: The result is an lvalue of type "T".
200 // However, subscripting vector types is more like member access.
201 case Expr::ArraySubscriptExprClass:
202 if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType())
203 return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase());
204 return Cl::CL_LValue;
206 // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a
207 // function or variable and a prvalue otherwise.
208 case Expr::DeclRefExprClass:
209 if (E->getType() == Ctx.UnknownAnyTy)
210 return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl())
211 ? Cl::CL_PRValue : Cl::CL_LValue;
212 return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl());
214 // Member access is complex.
215 case Expr::MemberExprClass:
216 return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E));
218 case Expr::UnaryOperatorClass:
219 switch (cast<UnaryOperator>(E)->getOpcode()) {
220 // C++ [expr.unary.op]p1: The unary * operator performs indirection:
221 // [...] the result is an lvalue referring to the object or function
222 // to which the expression points.
224 return Cl::CL_LValue;
226 // GNU extensions, simply look through them.
228 return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr());
230 // Treat _Real and _Imag basically as if they were member
231 // expressions: l-value only if the operand is a true l-value.
234 const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens();
235 Cl::Kinds K = ClassifyInternal(Ctx, Op);
236 if (K != Cl::CL_LValue) return K;
238 if (isa<ObjCPropertyRefExpr>(Op))
239 return Cl::CL_SubObjCPropertySetting;
240 return Cl::CL_LValue;
243 // C++ [expr.pre.incr]p1: The result is the updated operand; it is an
248 return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue;
251 return Cl::CL_PRValue;
254 case Expr::OpaqueValueExprClass:
255 return ClassifyExprValueKind(Lang, E, E->getValueKind());
257 // Pseudo-object expressions can produce l-values with reference magic.
258 case Expr::PseudoObjectExprClass:
259 return ClassifyExprValueKind(Lang, E,
260 cast<PseudoObjectExpr>(E)->getValueKind());
262 // Implicit casts are lvalues if they're lvalue casts. Other than that, we
263 // only specifically record class temporaries.
264 case Expr::ImplicitCastExprClass:
265 return ClassifyExprValueKind(Lang, E, E->getValueKind());
267 // C++ [expr.prim.general]p4: The presence of parentheses does not affect
268 // whether the expression is an lvalue.
269 case Expr::ParenExprClass:
270 return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr());
272 // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator,
273 // or a void expression if its result expression is, respectively, an
274 // lvalue, a function designator, or a void expression.
275 case Expr::GenericSelectionExprClass:
276 if (cast<GenericSelectionExpr>(E)->isResultDependent())
277 return Cl::CL_PRValue;
278 return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr());
280 case Expr::BinaryOperatorClass:
281 case Expr::CompoundAssignOperatorClass:
282 // C doesn't have any binary expressions that are lvalues.
284 return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E));
285 return Cl::CL_PRValue;
287 case Expr::CallExprClass:
288 case Expr::CXXOperatorCallExprClass:
289 case Expr::CXXMemberCallExprClass:
290 case Expr::UserDefinedLiteralClass:
291 case Expr::CUDAKernelCallExprClass:
292 return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType(Ctx));
294 // __builtin_choose_expr is equivalent to the chosen expression.
295 case Expr::ChooseExprClass:
296 return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr());
298 // Extended vector element access is an lvalue unless there are duplicates
299 // in the shuffle expression.
300 case Expr::ExtVectorElementExprClass:
301 if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements())
302 return Cl::CL_DuplicateVectorComponents;
303 if (cast<ExtVectorElementExpr>(E)->isArrow())
304 return Cl::CL_LValue;
305 return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase());
307 // Simply look at the actual default argument.
308 case Expr::CXXDefaultArgExprClass:
309 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr());
311 // Same idea for default initializers.
312 case Expr::CXXDefaultInitExprClass:
313 return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr());
315 // Same idea for temporary binding.
316 case Expr::CXXBindTemporaryExprClass:
317 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr());
319 // And the cleanups guard.
320 case Expr::ExprWithCleanupsClass:
321 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr());
323 // Casts depend completely on the target type. All casts work the same.
324 case Expr::CStyleCastExprClass:
325 case Expr::CXXFunctionalCastExprClass:
326 case Expr::CXXStaticCastExprClass:
327 case Expr::CXXDynamicCastExprClass:
328 case Expr::CXXReinterpretCastExprClass:
329 case Expr::CXXConstCastExprClass:
330 case Expr::ObjCBridgedCastExprClass:
331 // Only in C++ can casts be interesting at all.
332 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
333 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten());
335 case Expr::CXXUnresolvedConstructExprClass:
336 return ClassifyUnnamed(Ctx,
337 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten());
339 case Expr::BinaryConditionalOperatorClass: {
340 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
341 const BinaryConditionalOperator *co = cast<BinaryConditionalOperator>(E);
342 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
345 case Expr::ConditionalOperatorClass: {
346 // Once again, only C++ is interesting.
347 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
348 const ConditionalOperator *co = cast<ConditionalOperator>(E);
349 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
352 // ObjC message sends are effectively function calls, if the target function
354 case Expr::ObjCMessageExprClass:
355 if (const ObjCMethodDecl *Method =
356 cast<ObjCMessageExpr>(E)->getMethodDecl()) {
357 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getReturnType());
358 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind;
360 return Cl::CL_PRValue;
362 // Some C++ expressions are always class temporaries.
363 case Expr::CXXConstructExprClass:
364 case Expr::CXXInheritedCtorInitExprClass:
365 case Expr::CXXTemporaryObjectExprClass:
366 case Expr::LambdaExprClass:
367 case Expr::CXXStdInitializerListExprClass:
368 return Cl::CL_ClassTemporary;
370 case Expr::VAArgExprClass:
371 return ClassifyUnnamed(Ctx, E->getType());
373 case Expr::DesignatedInitExprClass:
374 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit());
376 case Expr::StmtExprClass: {
377 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt();
378 if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back()))
379 return ClassifyUnnamed(Ctx, LastExpr->getType());
380 return Cl::CL_PRValue;
383 case Expr::CXXUuidofExprClass:
384 return Cl::CL_LValue;
386 case Expr::PackExpansionExprClass:
387 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern());
389 case Expr::MaterializeTemporaryExprClass:
390 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference()
394 case Expr::InitListExprClass:
395 // An init list can be an lvalue if it is bound to a reference and
396 // contains only one element. In that case, we look at that element
397 // for an exact classification. Init list creation takes care of the
398 // value kind for us, so we only need to fine-tune.
400 return ClassifyExprValueKind(Lang, E, E->getValueKind());
401 assert(cast<InitListExpr>(E)->getNumInits() == 1 &&
402 "Only 1-element init lists can be glvalues.");
403 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0));
405 case Expr::CoawaitExprClass:
406 return ClassifyInternal(Ctx, cast<CoawaitExpr>(E)->getResumeExpr());
409 llvm_unreachable("unhandled expression kind in classification");
412 /// ClassifyDecl - Return the classification of an expression referencing the
413 /// given declaration.
414 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) {
415 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a
416 // function, variable, or data member and a prvalue otherwise.
417 // In C, functions are not lvalues.
418 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an
419 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to
420 // special-case this.
422 if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance())
423 return Cl::CL_MemberFunction;
426 if (const NonTypeTemplateParmDecl *NTTParm =
427 dyn_cast<NonTypeTemplateParmDecl>(D))
428 islvalue = NTTParm->getType()->isReferenceType();
430 islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) ||
431 isa<IndirectFieldDecl>(D) ||
432 (Ctx.getLangOpts().CPlusPlus &&
433 (isa<FunctionDecl>(D) || isa<MSPropertyDecl>(D) ||
434 isa<FunctionTemplateDecl>(D)));
436 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue;
439 /// ClassifyUnnamed - Return the classification of an expression yielding an
440 /// unnamed value of the given type. This applies in particular to function
442 static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) {
443 // In C, function calls are always rvalues.
444 if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue;
446 // C++ [expr.call]p10: A function call is an lvalue if the result type is an
447 // lvalue reference type or an rvalue reference to function type, an xvalue
448 // if the result type is an rvalue reference to object type, and a prvalue
450 if (T->isLValueReferenceType())
451 return Cl::CL_LValue;
452 const RValueReferenceType *RV = T->getAs<RValueReferenceType>();
453 if (!RV) // Could still be a class temporary, though.
454 return ClassifyTemporary(T);
456 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue;
459 static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) {
460 if (E->getType() == Ctx.UnknownAnyTy)
461 return (isa<FunctionDecl>(E->getMemberDecl())
462 ? Cl::CL_PRValue : Cl::CL_LValue);
464 // Handle C first, it's easier.
465 if (!Ctx.getLangOpts().CPlusPlus) {
467 // For dot access, the expression is an lvalue if the first part is. For
468 // arrow access, it always is an lvalue.
470 return Cl::CL_LValue;
471 // ObjC property accesses are not lvalues, but get special treatment.
472 Expr *Base = E->getBase()->IgnoreParens();
473 if (isa<ObjCPropertyRefExpr>(Base))
474 return Cl::CL_SubObjCPropertySetting;
475 return ClassifyInternal(Ctx, Base);
478 NamedDecl *Member = E->getMemberDecl();
479 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2.
480 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then
481 // E1.E2 is an lvalue.
482 if (ValueDecl *Value = dyn_cast<ValueDecl>(Member))
483 if (Value->getType()->isReferenceType())
484 return Cl::CL_LValue;
486 // Otherwise, one of the following rules applies.
487 // -- If E2 is a static member [...] then E1.E2 is an lvalue.
488 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord())
489 return Cl::CL_LValue;
491 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then
492 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue;
493 // otherwise, it is a prvalue.
494 if (isa<FieldDecl>(Member)) {
497 return Cl::CL_LValue;
498 Expr *Base = E->getBase()->IgnoreParenImpCasts();
499 if (isa<ObjCPropertyRefExpr>(Base))
500 return Cl::CL_SubObjCPropertySetting;
501 return ClassifyInternal(Ctx, E->getBase());
504 // -- If E2 is a [...] member function, [...]
505 // -- If it refers to a static member function [...], then E1.E2 is an
507 // -- Otherwise [...] E1.E2 is a prvalue.
508 if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member))
509 return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction;
511 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue.
512 // So is everything else we haven't handled yet.
513 return Cl::CL_PRValue;
516 static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) {
517 assert(Ctx.getLangOpts().CPlusPlus &&
518 "This is only relevant for C++.");
519 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand.
520 // Except we override this for writes to ObjC properties.
521 if (E->isAssignmentOp())
522 return (E->getLHS()->getObjectKind() == OK_ObjCProperty
523 ? Cl::CL_PRValue : Cl::CL_LValue);
525 // C++ [expr.comma]p1: the result is of the same value category as its right
527 if (E->getOpcode() == BO_Comma)
528 return ClassifyInternal(Ctx, E->getRHS());
530 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand
531 // is a pointer to a data member is of the same value category as its first
533 if (E->getOpcode() == BO_PtrMemD)
534 return (E->getType()->isFunctionType() ||
535 E->hasPlaceholderType(BuiltinType::BoundMember))
536 ? Cl::CL_MemberFunction
537 : ClassifyInternal(Ctx, E->getLHS());
539 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its
540 // second operand is a pointer to data member and a prvalue otherwise.
541 if (E->getOpcode() == BO_PtrMemI)
542 return (E->getType()->isFunctionType() ||
543 E->hasPlaceholderType(BuiltinType::BoundMember))
544 ? Cl::CL_MemberFunction
547 // All other binary operations are prvalues.
548 return Cl::CL_PRValue;
551 static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True,
553 assert(Ctx.getLangOpts().CPlusPlus &&
554 "This is only relevant for C++.");
557 // If either the second or the third operand has type (cv) void,
558 // one of the following shall hold:
559 if (True->getType()->isVoidType() || False->getType()->isVoidType()) {
560 // The second or the third operand (but not both) is a (possibly
561 // parenthesized) throw-expression; the result is of the [...] value
562 // category of the other.
563 bool TrueIsThrow = isa<CXXThrowExpr>(True->IgnoreParenImpCasts());
564 bool FalseIsThrow = isa<CXXThrowExpr>(False->IgnoreParenImpCasts());
565 if (const Expr *NonThrow = TrueIsThrow ? (FalseIsThrow ? nullptr : False)
566 : (FalseIsThrow ? True : nullptr))
567 return ClassifyInternal(Ctx, NonThrow);
569 // [Otherwise] the result [...] is a prvalue.
570 return Cl::CL_PRValue;
573 // Note that at this point, we have already performed all conversions
574 // according to [expr.cond]p3.
575 // C++ [expr.cond]p4: If the second and third operands are glvalues of the
576 // same value category [...], the result is of that [...] value category.
577 // C++ [expr.cond]p5: Otherwise, the result is a prvalue.
578 Cl::Kinds LCl = ClassifyInternal(Ctx, True),
579 RCl = ClassifyInternal(Ctx, False);
580 return LCl == RCl ? LCl : Cl::CL_PRValue;
583 static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,
584 Cl::Kinds Kind, SourceLocation &Loc) {
585 // As a general rule, we only care about lvalues. But there are some rvalues
586 // for which we want to generate special results.
587 if (Kind == Cl::CL_PRValue) {
588 // For the sake of better diagnostics, we want to specifically recognize
589 // use of the GCC cast-as-lvalue extension.
590 if (const ExplicitCastExpr *CE =
591 dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) {
592 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) {
593 Loc = CE->getExprLoc();
594 return Cl::CM_LValueCast;
598 if (Kind != Cl::CL_LValue)
599 return Cl::CM_RValue;
601 // This is the lvalue case.
602 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6)
603 if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType())
604 return Cl::CM_Function;
606 // Assignment to a property in ObjC is an implicit setter access. But a
607 // setter might not exist.
608 if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) {
609 if (Expr->isImplicitProperty() &&
610 Expr->getImplicitPropertySetter() == nullptr)
611 return Cl::CM_NoSetterProperty;
614 CanQualType CT = Ctx.getCanonicalType(E->getType());
615 // Const stuff is obviously not modifiable.
616 if (CT.isConstQualified())
617 return Cl::CM_ConstQualified;
618 if (CT.getQualifiers().getAddressSpace() == LangAS::opencl_constant)
619 return Cl::CM_ConstAddrSpace;
621 // Arrays are not modifiable, only their elements are.
622 if (CT->isArrayType())
623 return Cl::CM_ArrayType;
624 // Incomplete types are not modifiable.
625 if (CT->isIncompleteType())
626 return Cl::CM_IncompleteType;
628 // Records with any const fields (recursively) are not modifiable.
629 if (const RecordType *R = CT->getAs<RecordType>())
630 if (R->hasConstFields())
631 return Cl::CM_ConstQualified;
633 return Cl::CM_Modifiable;
636 Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const {
637 Classification VC = Classify(Ctx);
638 switch (VC.getKind()) {
639 case Cl::CL_LValue: return LV_Valid;
640 case Cl::CL_XValue: return LV_InvalidExpression;
641 case Cl::CL_Function: return LV_NotObjectType;
642 case Cl::CL_Void: return LV_InvalidExpression;
643 case Cl::CL_AddressableVoid: return LV_IncompleteVoidType;
644 case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents;
645 case Cl::CL_MemberFunction: return LV_MemberFunction;
646 case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting;
647 case Cl::CL_ClassTemporary: return LV_ClassTemporary;
648 case Cl::CL_ArrayTemporary: return LV_ArrayTemporary;
649 case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression;
650 case Cl::CL_PRValue: return LV_InvalidExpression;
652 llvm_unreachable("Unhandled kind");
655 Expr::isModifiableLvalueResult
656 Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const {
657 SourceLocation dummy;
658 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy);
659 switch (VC.getKind()) {
660 case Cl::CL_LValue: break;
661 case Cl::CL_XValue: return MLV_InvalidExpression;
662 case Cl::CL_Function: return MLV_NotObjectType;
663 case Cl::CL_Void: return MLV_InvalidExpression;
664 case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType;
665 case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents;
666 case Cl::CL_MemberFunction: return MLV_MemberFunction;
667 case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting;
668 case Cl::CL_ClassTemporary: return MLV_ClassTemporary;
669 case Cl::CL_ArrayTemporary: return MLV_ArrayTemporary;
670 case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression;
672 return VC.getModifiable() == Cl::CM_LValueCast ?
673 MLV_LValueCast : MLV_InvalidExpression;
675 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind");
676 switch (VC.getModifiable()) {
677 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability");
678 case Cl::CM_Modifiable: return MLV_Valid;
679 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match");
680 case Cl::CM_Function: return MLV_NotObjectType;
681 case Cl::CM_LValueCast:
682 llvm_unreachable("CM_LValueCast and CL_LValue don't match");
683 case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty;
684 case Cl::CM_ConstQualified: return MLV_ConstQualified;
685 case Cl::CM_ConstAddrSpace: return MLV_ConstAddrSpace;
686 case Cl::CM_ArrayType: return MLV_ArrayType;
687 case Cl::CM_IncompleteType: return MLV_IncompleteType;
689 llvm_unreachable("Unhandled modifiable type");