1 //===- ExprClassification.cpp - Expression AST Node Implementation --------===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 // This file implements Expr::classify.
11 //===----------------------------------------------------------------------===//
13 #include "clang/AST/Expr.h"
14 #include "clang/AST/ASTContext.h"
15 #include "clang/AST/DeclCXX.h"
16 #include "clang/AST/DeclObjC.h"
17 #include "clang/AST/DeclTemplate.h"
18 #include "clang/AST/ExprCXX.h"
19 #include "clang/AST/ExprObjC.h"
20 #include "llvm/Support/ErrorHandling.h"
22 using namespace clang;
24 using Cl = Expr::Classification;
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::FixedPointLiteralClass:
164 case Expr::CharacterLiteralClass:
165 case Expr::AddrLabelExprClass:
166 case Expr::CXXDeleteExprClass:
167 case Expr::ImplicitValueInitExprClass:
168 case Expr::BlockExprClass:
169 case Expr::FloatingLiteralClass:
170 case Expr::CXXNoexceptExprClass:
171 case Expr::CXXScalarValueInitExprClass:
172 case Expr::TypeTraitExprClass:
173 case Expr::ArrayTypeTraitExprClass:
174 case Expr::ExpressionTraitExprClass:
175 case Expr::ObjCSelectorExprClass:
176 case Expr::ObjCProtocolExprClass:
177 case Expr::ObjCStringLiteralClass:
178 case Expr::ObjCBoxedExprClass:
179 case Expr::ObjCArrayLiteralClass:
180 case Expr::ObjCDictionaryLiteralClass:
181 case Expr::ObjCBoolLiteralExprClass:
182 case Expr::ObjCAvailabilityCheckExprClass:
183 case Expr::ParenListExprClass:
184 case Expr::SizeOfPackExprClass:
185 case Expr::SubstNonTypeTemplateParmPackExprClass:
186 case Expr::AsTypeExprClass:
187 case Expr::ObjCIndirectCopyRestoreExprClass:
188 case Expr::AtomicExprClass:
189 case Expr::CXXFoldExprClass:
190 case Expr::ArrayInitLoopExprClass:
191 case Expr::ArrayInitIndexExprClass:
192 case Expr::NoInitExprClass:
193 case Expr::DesignatedInitUpdateExprClass:
194 case Expr::SourceLocExprClass:
195 return Cl::CL_PRValue;
197 case Expr::ConstantExprClass:
198 return ClassifyInternal(Ctx, cast<ConstantExpr>(E)->getSubExpr());
200 // Next come the complicated cases.
201 case Expr::SubstNonTypeTemplateParmExprClass:
202 return ClassifyInternal(Ctx,
203 cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement());
205 // C, C++98 [expr.sub]p1: The result is an lvalue of type "T".
206 // C++11 (DR1213): in the case of an array operand, the result is an lvalue
207 // if that operand is an lvalue and an xvalue otherwise.
208 // Subscripting vector types is more like member access.
209 case Expr::ArraySubscriptExprClass:
210 if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType())
211 return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase());
212 if (Lang.CPlusPlus11) {
213 // Step over the array-to-pointer decay if present, but not over the
214 // temporary materialization.
215 auto *Base = cast<ArraySubscriptExpr>(E)->getBase()->IgnoreImpCasts();
216 if (Base->getType()->isArrayType())
217 return ClassifyInternal(Ctx, Base);
219 return Cl::CL_LValue;
221 // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a
222 // function or variable and a prvalue otherwise.
223 case Expr::DeclRefExprClass:
224 if (E->getType() == Ctx.UnknownAnyTy)
225 return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl())
226 ? Cl::CL_PRValue : Cl::CL_LValue;
227 return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl());
229 // Member access is complex.
230 case Expr::MemberExprClass:
231 return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E));
233 case Expr::UnaryOperatorClass:
234 switch (cast<UnaryOperator>(E)->getOpcode()) {
235 // C++ [expr.unary.op]p1: The unary * operator performs indirection:
236 // [...] the result is an lvalue referring to the object or function
237 // to which the expression points.
239 return Cl::CL_LValue;
241 // GNU extensions, simply look through them.
243 return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr());
245 // Treat _Real and _Imag basically as if they were member
246 // expressions: l-value only if the operand is a true l-value.
249 const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens();
250 Cl::Kinds K = ClassifyInternal(Ctx, Op);
251 if (K != Cl::CL_LValue) return K;
253 if (isa<ObjCPropertyRefExpr>(Op))
254 return Cl::CL_SubObjCPropertySetting;
255 return Cl::CL_LValue;
258 // C++ [expr.pre.incr]p1: The result is the updated operand; it is an
263 return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue;
266 return Cl::CL_PRValue;
269 case Expr::OpaqueValueExprClass:
270 return ClassifyExprValueKind(Lang, E, E->getValueKind());
272 // Pseudo-object expressions can produce l-values with reference magic.
273 case Expr::PseudoObjectExprClass:
274 return ClassifyExprValueKind(Lang, E,
275 cast<PseudoObjectExpr>(E)->getValueKind());
277 // Implicit casts are lvalues if they're lvalue casts. Other than that, we
278 // only specifically record class temporaries.
279 case Expr::ImplicitCastExprClass:
280 return ClassifyExprValueKind(Lang, E, E->getValueKind());
282 // C++ [expr.prim.general]p4: The presence of parentheses does not affect
283 // whether the expression is an lvalue.
284 case Expr::ParenExprClass:
285 return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr());
287 // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator,
288 // or a void expression if its result expression is, respectively, an
289 // lvalue, a function designator, or a void expression.
290 case Expr::GenericSelectionExprClass:
291 if (cast<GenericSelectionExpr>(E)->isResultDependent())
292 return Cl::CL_PRValue;
293 return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr());
295 case Expr::BinaryOperatorClass:
296 case Expr::CompoundAssignOperatorClass:
297 // C doesn't have any binary expressions that are lvalues.
299 return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E));
300 return Cl::CL_PRValue;
302 case Expr::CallExprClass:
303 case Expr::CXXOperatorCallExprClass:
304 case Expr::CXXMemberCallExprClass:
305 case Expr::UserDefinedLiteralClass:
306 case Expr::CUDAKernelCallExprClass:
307 return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType(Ctx));
309 // __builtin_choose_expr is equivalent to the chosen expression.
310 case Expr::ChooseExprClass:
311 return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr());
313 // Extended vector element access is an lvalue unless there are duplicates
314 // in the shuffle expression.
315 case Expr::ExtVectorElementExprClass:
316 if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements())
317 return Cl::CL_DuplicateVectorComponents;
318 if (cast<ExtVectorElementExpr>(E)->isArrow())
319 return Cl::CL_LValue;
320 return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase());
322 // Simply look at the actual default argument.
323 case Expr::CXXDefaultArgExprClass:
324 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr());
326 // Same idea for default initializers.
327 case Expr::CXXDefaultInitExprClass:
328 return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr());
330 // Same idea for temporary binding.
331 case Expr::CXXBindTemporaryExprClass:
332 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr());
334 // And the cleanups guard.
335 case Expr::ExprWithCleanupsClass:
336 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr());
338 // Casts depend completely on the target type. All casts work the same.
339 case Expr::CStyleCastExprClass:
340 case Expr::CXXFunctionalCastExprClass:
341 case Expr::CXXStaticCastExprClass:
342 case Expr::CXXDynamicCastExprClass:
343 case Expr::CXXReinterpretCastExprClass:
344 case Expr::CXXConstCastExprClass:
345 case Expr::ObjCBridgedCastExprClass:
346 case Expr::BuiltinBitCastExprClass:
347 // Only in C++ can casts be interesting at all.
348 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
349 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten());
351 case Expr::CXXUnresolvedConstructExprClass:
352 return ClassifyUnnamed(Ctx,
353 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten());
355 case Expr::BinaryConditionalOperatorClass: {
356 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
357 const auto *co = cast<BinaryConditionalOperator>(E);
358 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
361 case Expr::ConditionalOperatorClass: {
362 // Once again, only C++ is interesting.
363 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
364 const auto *co = cast<ConditionalOperator>(E);
365 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
368 // ObjC message sends are effectively function calls, if the target function
370 case Expr::ObjCMessageExprClass:
371 if (const ObjCMethodDecl *Method =
372 cast<ObjCMessageExpr>(E)->getMethodDecl()) {
373 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getReturnType());
374 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind;
376 return Cl::CL_PRValue;
378 // Some C++ expressions are always class temporaries.
379 case Expr::CXXConstructExprClass:
380 case Expr::CXXInheritedCtorInitExprClass:
381 case Expr::CXXTemporaryObjectExprClass:
382 case Expr::LambdaExprClass:
383 case Expr::CXXStdInitializerListExprClass:
384 return Cl::CL_ClassTemporary;
386 case Expr::VAArgExprClass:
387 return ClassifyUnnamed(Ctx, E->getType());
389 case Expr::DesignatedInitExprClass:
390 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit());
392 case Expr::StmtExprClass: {
393 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt();
394 if (const auto *LastExpr = dyn_cast_or_null<Expr>(S->body_back()))
395 return ClassifyUnnamed(Ctx, LastExpr->getType());
396 return Cl::CL_PRValue;
399 case Expr::CXXUuidofExprClass:
400 return Cl::CL_LValue;
402 case Expr::PackExpansionExprClass:
403 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern());
405 case Expr::MaterializeTemporaryExprClass:
406 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference()
410 case Expr::InitListExprClass:
411 // An init list can be an lvalue if it is bound to a reference and
412 // contains only one element. In that case, we look at that element
413 // for an exact classification. Init list creation takes care of the
414 // value kind for us, so we only need to fine-tune.
416 return ClassifyExprValueKind(Lang, E, E->getValueKind());
417 assert(cast<InitListExpr>(E)->getNumInits() == 1 &&
418 "Only 1-element init lists can be glvalues.");
419 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0));
421 case Expr::CoawaitExprClass:
422 case Expr::CoyieldExprClass:
423 return ClassifyInternal(Ctx, cast<CoroutineSuspendExpr>(E)->getResumeExpr());
426 llvm_unreachable("unhandled expression kind in classification");
429 /// ClassifyDecl - Return the classification of an expression referencing the
430 /// given declaration.
431 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) {
432 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a
433 // function, variable, or data member and a prvalue otherwise.
434 // In C, functions are not lvalues.
435 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an
436 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to
437 // special-case this.
439 if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance())
440 return Cl::CL_MemberFunction;
443 if (const auto *NTTParm = dyn_cast<NonTypeTemplateParmDecl>(D))
444 islvalue = NTTParm->getType()->isReferenceType();
446 islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) ||
447 isa<IndirectFieldDecl>(D) ||
448 isa<BindingDecl>(D) ||
449 (Ctx.getLangOpts().CPlusPlus &&
450 (isa<FunctionDecl>(D) || isa<MSPropertyDecl>(D) ||
451 isa<FunctionTemplateDecl>(D)));
453 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue;
456 /// ClassifyUnnamed - Return the classification of an expression yielding an
457 /// unnamed value of the given type. This applies in particular to function
459 static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) {
460 // In C, function calls are always rvalues.
461 if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue;
463 // C++ [expr.call]p10: A function call is an lvalue if the result type is an
464 // lvalue reference type or an rvalue reference to function type, an xvalue
465 // if the result type is an rvalue reference to object type, and a prvalue
467 if (T->isLValueReferenceType())
468 return Cl::CL_LValue;
469 const auto *RV = T->getAs<RValueReferenceType>();
470 if (!RV) // Could still be a class temporary, though.
471 return ClassifyTemporary(T);
473 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue;
476 static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) {
477 if (E->getType() == Ctx.UnknownAnyTy)
478 return (isa<FunctionDecl>(E->getMemberDecl())
479 ? Cl::CL_PRValue : Cl::CL_LValue);
481 // Handle C first, it's easier.
482 if (!Ctx.getLangOpts().CPlusPlus) {
484 // For dot access, the expression is an lvalue if the first part is. For
485 // arrow access, it always is an lvalue.
487 return Cl::CL_LValue;
488 // ObjC property accesses are not lvalues, but get special treatment.
489 Expr *Base = E->getBase()->IgnoreParens();
490 if (isa<ObjCPropertyRefExpr>(Base))
491 return Cl::CL_SubObjCPropertySetting;
492 return ClassifyInternal(Ctx, Base);
495 NamedDecl *Member = E->getMemberDecl();
496 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2.
497 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then
498 // E1.E2 is an lvalue.
499 if (const auto *Value = dyn_cast<ValueDecl>(Member))
500 if (Value->getType()->isReferenceType())
501 return Cl::CL_LValue;
503 // Otherwise, one of the following rules applies.
504 // -- If E2 is a static member [...] then E1.E2 is an lvalue.
505 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord())
506 return Cl::CL_LValue;
508 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then
509 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue;
510 // otherwise, it is a prvalue.
511 if (isa<FieldDecl>(Member)) {
514 return Cl::CL_LValue;
515 Expr *Base = E->getBase()->IgnoreParenImpCasts();
516 if (isa<ObjCPropertyRefExpr>(Base))
517 return Cl::CL_SubObjCPropertySetting;
518 return ClassifyInternal(Ctx, E->getBase());
521 // -- If E2 is a [...] member function, [...]
522 // -- If it refers to a static member function [...], then E1.E2 is an
524 // -- Otherwise [...] E1.E2 is a prvalue.
525 if (const auto *Method = dyn_cast<CXXMethodDecl>(Member))
526 return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction;
528 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue.
529 // So is everything else we haven't handled yet.
530 return Cl::CL_PRValue;
533 static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) {
534 assert(Ctx.getLangOpts().CPlusPlus &&
535 "This is only relevant for C++.");
536 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand.
537 // Except we override this for writes to ObjC properties.
538 if (E->isAssignmentOp())
539 return (E->getLHS()->getObjectKind() == OK_ObjCProperty
540 ? Cl::CL_PRValue : Cl::CL_LValue);
542 // C++ [expr.comma]p1: the result is of the same value category as its right
544 if (E->getOpcode() == BO_Comma)
545 return ClassifyInternal(Ctx, E->getRHS());
547 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand
548 // is a pointer to a data member is of the same value category as its first
550 if (E->getOpcode() == BO_PtrMemD)
551 return (E->getType()->isFunctionType() ||
552 E->hasPlaceholderType(BuiltinType::BoundMember))
553 ? Cl::CL_MemberFunction
554 : ClassifyInternal(Ctx, E->getLHS());
556 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its
557 // second operand is a pointer to data member and a prvalue otherwise.
558 if (E->getOpcode() == BO_PtrMemI)
559 return (E->getType()->isFunctionType() ||
560 E->hasPlaceholderType(BuiltinType::BoundMember))
561 ? Cl::CL_MemberFunction
564 // All other binary operations are prvalues.
565 return Cl::CL_PRValue;
568 static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True,
570 assert(Ctx.getLangOpts().CPlusPlus &&
571 "This is only relevant for C++.");
574 // If either the second or the third operand has type (cv) void,
575 // one of the following shall hold:
576 if (True->getType()->isVoidType() || False->getType()->isVoidType()) {
577 // The second or the third operand (but not both) is a (possibly
578 // parenthesized) throw-expression; the result is of the [...] value
579 // category of the other.
580 bool TrueIsThrow = isa<CXXThrowExpr>(True->IgnoreParenImpCasts());
581 bool FalseIsThrow = isa<CXXThrowExpr>(False->IgnoreParenImpCasts());
582 if (const Expr *NonThrow = TrueIsThrow ? (FalseIsThrow ? nullptr : False)
583 : (FalseIsThrow ? True : nullptr))
584 return ClassifyInternal(Ctx, NonThrow);
586 // [Otherwise] the result [...] is a prvalue.
587 return Cl::CL_PRValue;
590 // Note that at this point, we have already performed all conversions
591 // according to [expr.cond]p3.
592 // C++ [expr.cond]p4: If the second and third operands are glvalues of the
593 // same value category [...], the result is of that [...] value category.
594 // C++ [expr.cond]p5: Otherwise, the result is a prvalue.
595 Cl::Kinds LCl = ClassifyInternal(Ctx, True),
596 RCl = ClassifyInternal(Ctx, False);
597 return LCl == RCl ? LCl : Cl::CL_PRValue;
600 static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,
601 Cl::Kinds Kind, SourceLocation &Loc) {
602 // As a general rule, we only care about lvalues. But there are some rvalues
603 // for which we want to generate special results.
604 if (Kind == Cl::CL_PRValue) {
605 // For the sake of better diagnostics, we want to specifically recognize
606 // use of the GCC cast-as-lvalue extension.
607 if (const auto *CE = dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) {
608 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) {
609 Loc = CE->getExprLoc();
610 return Cl::CM_LValueCast;
614 if (Kind != Cl::CL_LValue)
615 return Cl::CM_RValue;
617 // This is the lvalue case.
618 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6)
619 if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType())
620 return Cl::CM_Function;
622 // Assignment to a property in ObjC is an implicit setter access. But a
623 // setter might not exist.
624 if (const auto *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) {
625 if (Expr->isImplicitProperty() &&
626 Expr->getImplicitPropertySetter() == nullptr)
627 return Cl::CM_NoSetterProperty;
630 CanQualType CT = Ctx.getCanonicalType(E->getType());
631 // Const stuff is obviously not modifiable.
632 if (CT.isConstQualified())
633 return Cl::CM_ConstQualified;
634 if (Ctx.getLangOpts().OpenCL &&
635 CT.getQualifiers().getAddressSpace() == LangAS::opencl_constant)
636 return Cl::CM_ConstAddrSpace;
638 // Arrays are not modifiable, only their elements are.
639 if (CT->isArrayType())
640 return Cl::CM_ArrayType;
641 // Incomplete types are not modifiable.
642 if (CT->isIncompleteType())
643 return Cl::CM_IncompleteType;
645 // Records with any const fields (recursively) are not modifiable.
646 if (const RecordType *R = CT->getAs<RecordType>())
647 if (R->hasConstFields())
648 return Cl::CM_ConstQualifiedField;
650 return Cl::CM_Modifiable;
653 Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const {
654 Classification VC = Classify(Ctx);
655 switch (VC.getKind()) {
656 case Cl::CL_LValue: return LV_Valid;
657 case Cl::CL_XValue: return LV_InvalidExpression;
658 case Cl::CL_Function: return LV_NotObjectType;
659 case Cl::CL_Void: return LV_InvalidExpression;
660 case Cl::CL_AddressableVoid: return LV_IncompleteVoidType;
661 case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents;
662 case Cl::CL_MemberFunction: return LV_MemberFunction;
663 case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting;
664 case Cl::CL_ClassTemporary: return LV_ClassTemporary;
665 case Cl::CL_ArrayTemporary: return LV_ArrayTemporary;
666 case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression;
667 case Cl::CL_PRValue: return LV_InvalidExpression;
669 llvm_unreachable("Unhandled kind");
672 Expr::isModifiableLvalueResult
673 Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const {
674 SourceLocation dummy;
675 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy);
676 switch (VC.getKind()) {
677 case Cl::CL_LValue: break;
678 case Cl::CL_XValue: return MLV_InvalidExpression;
679 case Cl::CL_Function: return MLV_NotObjectType;
680 case Cl::CL_Void: return MLV_InvalidExpression;
681 case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType;
682 case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents;
683 case Cl::CL_MemberFunction: return MLV_MemberFunction;
684 case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting;
685 case Cl::CL_ClassTemporary: return MLV_ClassTemporary;
686 case Cl::CL_ArrayTemporary: return MLV_ArrayTemporary;
687 case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression;
689 return VC.getModifiable() == Cl::CM_LValueCast ?
690 MLV_LValueCast : MLV_InvalidExpression;
692 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind");
693 switch (VC.getModifiable()) {
694 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability");
695 case Cl::CM_Modifiable: return MLV_Valid;
696 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match");
697 case Cl::CM_Function: return MLV_NotObjectType;
698 case Cl::CM_LValueCast:
699 llvm_unreachable("CM_LValueCast and CL_LValue don't match");
700 case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty;
701 case Cl::CM_ConstQualified: return MLV_ConstQualified;
702 case Cl::CM_ConstQualifiedField: return MLV_ConstQualifiedField;
703 case Cl::CM_ConstAddrSpace: return MLV_ConstAddrSpace;
704 case Cl::CM_ArrayType: return MLV_ArrayType;
705 case Cl::CM_IncompleteType: return MLV_IncompleteType;
707 llvm_unreachable("Unhandled modifiable type");