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::DependentCoawaitExprClass:
133 case Expr::CXXDependentScopeMemberExprClass:
134 case Expr::DependentScopeDeclRefExprClass:
135 // ObjC instance variables are lvalues
136 // FIXME: ObjC++0x might have different rules
137 case Expr::ObjCIvarRefExprClass:
138 case Expr::FunctionParmPackExprClass:
139 case Expr::MSPropertyRefExprClass:
140 case Expr::MSPropertySubscriptExprClass:
141 case Expr::OMPArraySectionExprClass:
142 return Cl::CL_LValue;
144 // C99 6.5.2.5p5 says that compound literals are lvalues.
145 // In C++, they're prvalue temporaries, except for file-scope arrays.
146 case Expr::CompoundLiteralExprClass:
147 return !E->isLValue() ? ClassifyTemporary(E->getType()) : Cl::CL_LValue;
149 // Expressions that are prvalues.
150 case Expr::CXXBoolLiteralExprClass:
151 case Expr::CXXPseudoDestructorExprClass:
152 case Expr::UnaryExprOrTypeTraitExprClass:
153 case Expr::CXXNewExprClass:
154 case Expr::CXXThisExprClass:
155 case Expr::CXXNullPtrLiteralExprClass:
156 case Expr::ImaginaryLiteralClass:
157 case Expr::GNUNullExprClass:
158 case Expr::OffsetOfExprClass:
159 case Expr::CXXThrowExprClass:
160 case Expr::ShuffleVectorExprClass:
161 case Expr::ConvertVectorExprClass:
162 case Expr::IntegerLiteralClass:
163 case Expr::CharacterLiteralClass:
164 case Expr::AddrLabelExprClass:
165 case Expr::CXXDeleteExprClass:
166 case Expr::ImplicitValueInitExprClass:
167 case Expr::BlockExprClass:
168 case Expr::FloatingLiteralClass:
169 case Expr::CXXNoexceptExprClass:
170 case Expr::CXXScalarValueInitExprClass:
171 case Expr::TypeTraitExprClass:
172 case Expr::ArrayTypeTraitExprClass:
173 case Expr::ExpressionTraitExprClass:
174 case Expr::ObjCSelectorExprClass:
175 case Expr::ObjCProtocolExprClass:
176 case Expr::ObjCStringLiteralClass:
177 case Expr::ObjCBoxedExprClass:
178 case Expr::ObjCArrayLiteralClass:
179 case Expr::ObjCDictionaryLiteralClass:
180 case Expr::ObjCBoolLiteralExprClass:
181 case Expr::ObjCAvailabilityCheckExprClass:
182 case Expr::ParenListExprClass:
183 case Expr::SizeOfPackExprClass:
184 case Expr::SubstNonTypeTemplateParmPackExprClass:
185 case Expr::AsTypeExprClass:
186 case Expr::ObjCIndirectCopyRestoreExprClass:
187 case Expr::AtomicExprClass:
188 case Expr::CXXFoldExprClass:
189 case Expr::ArrayInitLoopExprClass:
190 case Expr::ArrayInitIndexExprClass:
191 case Expr::NoInitExprClass:
192 case Expr::DesignatedInitUpdateExprClass:
193 return Cl::CL_PRValue;
195 // Next come the complicated cases.
196 case Expr::SubstNonTypeTemplateParmExprClass:
197 return ClassifyInternal(Ctx,
198 cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement());
200 // C, C++98 [expr.sub]p1: The result is an lvalue of type "T".
201 // C++11 (DR1213): in the case of an array operand, the result is an lvalue
202 // if that operand is an lvalue and an xvalue otherwise.
203 // Subscripting vector types is more like member access.
204 case Expr::ArraySubscriptExprClass:
205 if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType())
206 return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase());
207 if (Lang.CPlusPlus11) {
208 // Step over the array-to-pointer decay if present, but not over the
209 // temporary materialization.
210 auto *Base = cast<ArraySubscriptExpr>(E)->getBase()->IgnoreImpCasts();
211 if (Base->getType()->isArrayType())
212 return ClassifyInternal(Ctx, Base);
214 return Cl::CL_LValue;
216 // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a
217 // function or variable and a prvalue otherwise.
218 case Expr::DeclRefExprClass:
219 if (E->getType() == Ctx.UnknownAnyTy)
220 return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl())
221 ? Cl::CL_PRValue : Cl::CL_LValue;
222 return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl());
224 // Member access is complex.
225 case Expr::MemberExprClass:
226 return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E));
228 case Expr::UnaryOperatorClass:
229 switch (cast<UnaryOperator>(E)->getOpcode()) {
230 // C++ [expr.unary.op]p1: The unary * operator performs indirection:
231 // [...] the result is an lvalue referring to the object or function
232 // to which the expression points.
234 return Cl::CL_LValue;
236 // GNU extensions, simply look through them.
238 return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr());
240 // Treat _Real and _Imag basically as if they were member
241 // expressions: l-value only if the operand is a true l-value.
244 const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens();
245 Cl::Kinds K = ClassifyInternal(Ctx, Op);
246 if (K != Cl::CL_LValue) return K;
248 if (isa<ObjCPropertyRefExpr>(Op))
249 return Cl::CL_SubObjCPropertySetting;
250 return Cl::CL_LValue;
253 // C++ [expr.pre.incr]p1: The result is the updated operand; it is an
258 return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue;
261 return Cl::CL_PRValue;
264 case Expr::OpaqueValueExprClass:
265 return ClassifyExprValueKind(Lang, E, E->getValueKind());
267 // Pseudo-object expressions can produce l-values with reference magic.
268 case Expr::PseudoObjectExprClass:
269 return ClassifyExprValueKind(Lang, E,
270 cast<PseudoObjectExpr>(E)->getValueKind());
272 // Implicit casts are lvalues if they're lvalue casts. Other than that, we
273 // only specifically record class temporaries.
274 case Expr::ImplicitCastExprClass:
275 return ClassifyExprValueKind(Lang, E, E->getValueKind());
277 // C++ [expr.prim.general]p4: The presence of parentheses does not affect
278 // whether the expression is an lvalue.
279 case Expr::ParenExprClass:
280 return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr());
282 // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator,
283 // or a void expression if its result expression is, respectively, an
284 // lvalue, a function designator, or a void expression.
285 case Expr::GenericSelectionExprClass:
286 if (cast<GenericSelectionExpr>(E)->isResultDependent())
287 return Cl::CL_PRValue;
288 return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr());
290 case Expr::BinaryOperatorClass:
291 case Expr::CompoundAssignOperatorClass:
292 // C doesn't have any binary expressions that are lvalues.
294 return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E));
295 return Cl::CL_PRValue;
297 case Expr::CallExprClass:
298 case Expr::CXXOperatorCallExprClass:
299 case Expr::CXXMemberCallExprClass:
300 case Expr::UserDefinedLiteralClass:
301 case Expr::CUDAKernelCallExprClass:
302 return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType(Ctx));
304 // __builtin_choose_expr is equivalent to the chosen expression.
305 case Expr::ChooseExprClass:
306 return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr());
308 // Extended vector element access is an lvalue unless there are duplicates
309 // in the shuffle expression.
310 case Expr::ExtVectorElementExprClass:
311 if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements())
312 return Cl::CL_DuplicateVectorComponents;
313 if (cast<ExtVectorElementExpr>(E)->isArrow())
314 return Cl::CL_LValue;
315 return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase());
317 // Simply look at the actual default argument.
318 case Expr::CXXDefaultArgExprClass:
319 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr());
321 // Same idea for default initializers.
322 case Expr::CXXDefaultInitExprClass:
323 return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr());
325 // Same idea for temporary binding.
326 case Expr::CXXBindTemporaryExprClass:
327 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr());
329 // And the cleanups guard.
330 case Expr::ExprWithCleanupsClass:
331 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr());
333 // Casts depend completely on the target type. All casts work the same.
334 case Expr::CStyleCastExprClass:
335 case Expr::CXXFunctionalCastExprClass:
336 case Expr::CXXStaticCastExprClass:
337 case Expr::CXXDynamicCastExprClass:
338 case Expr::CXXReinterpretCastExprClass:
339 case Expr::CXXConstCastExprClass:
340 case Expr::ObjCBridgedCastExprClass:
341 // Only in C++ can casts be interesting at all.
342 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
343 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten());
345 case Expr::CXXUnresolvedConstructExprClass:
346 return ClassifyUnnamed(Ctx,
347 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten());
349 case Expr::BinaryConditionalOperatorClass: {
350 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
351 const BinaryConditionalOperator *co = cast<BinaryConditionalOperator>(E);
352 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
355 case Expr::ConditionalOperatorClass: {
356 // Once again, only C++ is interesting.
357 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
358 const ConditionalOperator *co = cast<ConditionalOperator>(E);
359 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
362 // ObjC message sends are effectively function calls, if the target function
364 case Expr::ObjCMessageExprClass:
365 if (const ObjCMethodDecl *Method =
366 cast<ObjCMessageExpr>(E)->getMethodDecl()) {
367 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getReturnType());
368 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind;
370 return Cl::CL_PRValue;
372 // Some C++ expressions are always class temporaries.
373 case Expr::CXXConstructExprClass:
374 case Expr::CXXInheritedCtorInitExprClass:
375 case Expr::CXXTemporaryObjectExprClass:
376 case Expr::LambdaExprClass:
377 case Expr::CXXStdInitializerListExprClass:
378 return Cl::CL_ClassTemporary;
380 case Expr::VAArgExprClass:
381 return ClassifyUnnamed(Ctx, E->getType());
383 case Expr::DesignatedInitExprClass:
384 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit());
386 case Expr::StmtExprClass: {
387 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt();
388 if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back()))
389 return ClassifyUnnamed(Ctx, LastExpr->getType());
390 return Cl::CL_PRValue;
393 case Expr::CXXUuidofExprClass:
394 return Cl::CL_LValue;
396 case Expr::PackExpansionExprClass:
397 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern());
399 case Expr::MaterializeTemporaryExprClass:
400 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference()
404 case Expr::InitListExprClass:
405 // An init list can be an lvalue if it is bound to a reference and
406 // contains only one element. In that case, we look at that element
407 // for an exact classification. Init list creation takes care of the
408 // value kind for us, so we only need to fine-tune.
410 return ClassifyExprValueKind(Lang, E, E->getValueKind());
411 assert(cast<InitListExpr>(E)->getNumInits() == 1 &&
412 "Only 1-element init lists can be glvalues.");
413 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0));
415 case Expr::CoawaitExprClass:
416 case Expr::CoyieldExprClass:
417 return ClassifyInternal(Ctx, cast<CoroutineSuspendExpr>(E)->getResumeExpr());
420 llvm_unreachable("unhandled expression kind in classification");
423 /// ClassifyDecl - Return the classification of an expression referencing the
424 /// given declaration.
425 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) {
426 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a
427 // function, variable, or data member and a prvalue otherwise.
428 // In C, functions are not lvalues.
429 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an
430 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to
431 // special-case this.
433 if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance())
434 return Cl::CL_MemberFunction;
437 if (const NonTypeTemplateParmDecl *NTTParm =
438 dyn_cast<NonTypeTemplateParmDecl>(D))
439 islvalue = NTTParm->getType()->isReferenceType();
441 islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) ||
442 isa<IndirectFieldDecl>(D) ||
443 isa<BindingDecl>(D) ||
444 (Ctx.getLangOpts().CPlusPlus &&
445 (isa<FunctionDecl>(D) || isa<MSPropertyDecl>(D) ||
446 isa<FunctionTemplateDecl>(D)));
448 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue;
451 /// ClassifyUnnamed - Return the classification of an expression yielding an
452 /// unnamed value of the given type. This applies in particular to function
454 static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) {
455 // In C, function calls are always rvalues.
456 if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue;
458 // C++ [expr.call]p10: A function call is an lvalue if the result type is an
459 // lvalue reference type or an rvalue reference to function type, an xvalue
460 // if the result type is an rvalue reference to object type, and a prvalue
462 if (T->isLValueReferenceType())
463 return Cl::CL_LValue;
464 const RValueReferenceType *RV = T->getAs<RValueReferenceType>();
465 if (!RV) // Could still be a class temporary, though.
466 return ClassifyTemporary(T);
468 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue;
471 static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) {
472 if (E->getType() == Ctx.UnknownAnyTy)
473 return (isa<FunctionDecl>(E->getMemberDecl())
474 ? Cl::CL_PRValue : Cl::CL_LValue);
476 // Handle C first, it's easier.
477 if (!Ctx.getLangOpts().CPlusPlus) {
479 // For dot access, the expression is an lvalue if the first part is. For
480 // arrow access, it always is an lvalue.
482 return Cl::CL_LValue;
483 // ObjC property accesses are not lvalues, but get special treatment.
484 Expr *Base = E->getBase()->IgnoreParens();
485 if (isa<ObjCPropertyRefExpr>(Base))
486 return Cl::CL_SubObjCPropertySetting;
487 return ClassifyInternal(Ctx, Base);
490 NamedDecl *Member = E->getMemberDecl();
491 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2.
492 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then
493 // E1.E2 is an lvalue.
494 if (ValueDecl *Value = dyn_cast<ValueDecl>(Member))
495 if (Value->getType()->isReferenceType())
496 return Cl::CL_LValue;
498 // Otherwise, one of the following rules applies.
499 // -- If E2 is a static member [...] then E1.E2 is an lvalue.
500 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord())
501 return Cl::CL_LValue;
503 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then
504 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue;
505 // otherwise, it is a prvalue.
506 if (isa<FieldDecl>(Member)) {
509 return Cl::CL_LValue;
510 Expr *Base = E->getBase()->IgnoreParenImpCasts();
511 if (isa<ObjCPropertyRefExpr>(Base))
512 return Cl::CL_SubObjCPropertySetting;
513 return ClassifyInternal(Ctx, E->getBase());
516 // -- If E2 is a [...] member function, [...]
517 // -- If it refers to a static member function [...], then E1.E2 is an
519 // -- Otherwise [...] E1.E2 is a prvalue.
520 if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member))
521 return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction;
523 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue.
524 // So is everything else we haven't handled yet.
525 return Cl::CL_PRValue;
528 static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) {
529 assert(Ctx.getLangOpts().CPlusPlus &&
530 "This is only relevant for C++.");
531 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand.
532 // Except we override this for writes to ObjC properties.
533 if (E->isAssignmentOp())
534 return (E->getLHS()->getObjectKind() == OK_ObjCProperty
535 ? Cl::CL_PRValue : Cl::CL_LValue);
537 // C++ [expr.comma]p1: the result is of the same value category as its right
539 if (E->getOpcode() == BO_Comma)
540 return ClassifyInternal(Ctx, E->getRHS());
542 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand
543 // is a pointer to a data member is of the same value category as its first
545 if (E->getOpcode() == BO_PtrMemD)
546 return (E->getType()->isFunctionType() ||
547 E->hasPlaceholderType(BuiltinType::BoundMember))
548 ? Cl::CL_MemberFunction
549 : ClassifyInternal(Ctx, E->getLHS());
551 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its
552 // second operand is a pointer to data member and a prvalue otherwise.
553 if (E->getOpcode() == BO_PtrMemI)
554 return (E->getType()->isFunctionType() ||
555 E->hasPlaceholderType(BuiltinType::BoundMember))
556 ? Cl::CL_MemberFunction
559 // All other binary operations are prvalues.
560 return Cl::CL_PRValue;
563 static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True,
565 assert(Ctx.getLangOpts().CPlusPlus &&
566 "This is only relevant for C++.");
569 // If either the second or the third operand has type (cv) void,
570 // one of the following shall hold:
571 if (True->getType()->isVoidType() || False->getType()->isVoidType()) {
572 // The second or the third operand (but not both) is a (possibly
573 // parenthesized) throw-expression; the result is of the [...] value
574 // category of the other.
575 bool TrueIsThrow = isa<CXXThrowExpr>(True->IgnoreParenImpCasts());
576 bool FalseIsThrow = isa<CXXThrowExpr>(False->IgnoreParenImpCasts());
577 if (const Expr *NonThrow = TrueIsThrow ? (FalseIsThrow ? nullptr : False)
578 : (FalseIsThrow ? True : nullptr))
579 return ClassifyInternal(Ctx, NonThrow);
581 // [Otherwise] the result [...] is a prvalue.
582 return Cl::CL_PRValue;
585 // Note that at this point, we have already performed all conversions
586 // according to [expr.cond]p3.
587 // C++ [expr.cond]p4: If the second and third operands are glvalues of the
588 // same value category [...], the result is of that [...] value category.
589 // C++ [expr.cond]p5: Otherwise, the result is a prvalue.
590 Cl::Kinds LCl = ClassifyInternal(Ctx, True),
591 RCl = ClassifyInternal(Ctx, False);
592 return LCl == RCl ? LCl : Cl::CL_PRValue;
595 static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,
596 Cl::Kinds Kind, SourceLocation &Loc) {
597 // As a general rule, we only care about lvalues. But there are some rvalues
598 // for which we want to generate special results.
599 if (Kind == Cl::CL_PRValue) {
600 // For the sake of better diagnostics, we want to specifically recognize
601 // use of the GCC cast-as-lvalue extension.
602 if (const ExplicitCastExpr *CE =
603 dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) {
604 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) {
605 Loc = CE->getExprLoc();
606 return Cl::CM_LValueCast;
610 if (Kind != Cl::CL_LValue)
611 return Cl::CM_RValue;
613 // This is the lvalue case.
614 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6)
615 if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType())
616 return Cl::CM_Function;
618 // Assignment to a property in ObjC is an implicit setter access. But a
619 // setter might not exist.
620 if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) {
621 if (Expr->isImplicitProperty() &&
622 Expr->getImplicitPropertySetter() == nullptr)
623 return Cl::CM_NoSetterProperty;
626 CanQualType CT = Ctx.getCanonicalType(E->getType());
627 // Const stuff is obviously not modifiable.
628 if (CT.isConstQualified())
629 return Cl::CM_ConstQualified;
630 if (Ctx.getLangOpts().OpenCL &&
631 CT.getQualifiers().getAddressSpace() == LangAS::opencl_constant)
632 return Cl::CM_ConstAddrSpace;
634 // Arrays are not modifiable, only their elements are.
635 if (CT->isArrayType())
636 return Cl::CM_ArrayType;
637 // Incomplete types are not modifiable.
638 if (CT->isIncompleteType())
639 return Cl::CM_IncompleteType;
641 // Records with any const fields (recursively) are not modifiable.
642 if (const RecordType *R = CT->getAs<RecordType>())
643 if (R->hasConstFields())
644 return Cl::CM_ConstQualifiedField;
646 return Cl::CM_Modifiable;
649 Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const {
650 Classification VC = Classify(Ctx);
651 switch (VC.getKind()) {
652 case Cl::CL_LValue: return LV_Valid;
653 case Cl::CL_XValue: return LV_InvalidExpression;
654 case Cl::CL_Function: return LV_NotObjectType;
655 case Cl::CL_Void: return LV_InvalidExpression;
656 case Cl::CL_AddressableVoid: return LV_IncompleteVoidType;
657 case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents;
658 case Cl::CL_MemberFunction: return LV_MemberFunction;
659 case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting;
660 case Cl::CL_ClassTemporary: return LV_ClassTemporary;
661 case Cl::CL_ArrayTemporary: return LV_ArrayTemporary;
662 case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression;
663 case Cl::CL_PRValue: return LV_InvalidExpression;
665 llvm_unreachable("Unhandled kind");
668 Expr::isModifiableLvalueResult
669 Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const {
670 SourceLocation dummy;
671 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy);
672 switch (VC.getKind()) {
673 case Cl::CL_LValue: break;
674 case Cl::CL_XValue: return MLV_InvalidExpression;
675 case Cl::CL_Function: return MLV_NotObjectType;
676 case Cl::CL_Void: return MLV_InvalidExpression;
677 case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType;
678 case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents;
679 case Cl::CL_MemberFunction: return MLV_MemberFunction;
680 case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting;
681 case Cl::CL_ClassTemporary: return MLV_ClassTemporary;
682 case Cl::CL_ArrayTemporary: return MLV_ArrayTemporary;
683 case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression;
685 return VC.getModifiable() == Cl::CM_LValueCast ?
686 MLV_LValueCast : MLV_InvalidExpression;
688 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind");
689 switch (VC.getModifiable()) {
690 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability");
691 case Cl::CM_Modifiable: return MLV_Valid;
692 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match");
693 case Cl::CM_Function: return MLV_NotObjectType;
694 case Cl::CM_LValueCast:
695 llvm_unreachable("CM_LValueCast and CL_LValue don't match");
696 case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty;
697 case Cl::CM_ConstQualified: return MLV_ConstQualified;
698 case Cl::CM_ConstQualifiedField: return MLV_ConstQualifiedField;
699 case Cl::CM_ConstAddrSpace: return MLV_ConstAddrSpace;
700 case Cl::CM_ArrayType: return MLV_ArrayType;
701 case Cl::CM_IncompleteType: return MLV_IncompleteType;
703 llvm_unreachable("Unhandled modifiable type");