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"
23 using namespace clang;
25 using Cl = Expr::Classification;
27 static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E);
28 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D);
29 static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T);
30 static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E);
31 static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E);
32 static Cl::Kinds ClassifyConditional(ASTContext &Ctx,
34 const Expr *falseExpr);
35 static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,
36 Cl::Kinds Kind, SourceLocation &Loc);
38 Cl Expr::ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const {
39 assert(!TR->isReferenceType() && "Expressions can't have reference type.");
41 Cl::Kinds kind = ClassifyInternal(Ctx, this);
42 // C99 6.3.2.1: An lvalue is an expression with an object type or an
43 // incomplete type other than void.
44 if (!Ctx.getLangOpts().CPlusPlus) {
45 // Thus, no functions.
46 if (TR->isFunctionType() || TR == Ctx.OverloadTy)
47 kind = Cl::CL_Function;
48 // No void either, but qualified void is OK because it is "other than void".
49 // Void "lvalues" are classified as addressable void values, which are void
50 // expressions whose address can be taken.
51 else if (TR->isVoidType() && !TR.hasQualifiers())
52 kind = (kind == Cl::CL_LValue ? Cl::CL_AddressableVoid : Cl::CL_Void);
55 // Enable this assertion for testing.
57 case Cl::CL_LValue: assert(getValueKind() == VK_LValue); break;
58 case Cl::CL_XValue: assert(getValueKind() == VK_XValue); break;
61 case Cl::CL_AddressableVoid:
62 case Cl::CL_DuplicateVectorComponents:
63 case Cl::CL_MemberFunction:
64 case Cl::CL_SubObjCPropertySetting:
65 case Cl::CL_ClassTemporary:
66 case Cl::CL_ArrayTemporary:
67 case Cl::CL_ObjCMessageRValue:
68 case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break;
71 Cl::ModifiableType modifiable = Cl::CM_Untested;
73 modifiable = IsModifiable(Ctx, this, kind, *Loc);
74 return Classification(kind, modifiable);
77 /// Classify an expression which creates a temporary, based on its type.
78 static Cl::Kinds ClassifyTemporary(QualType T) {
79 if (T->isRecordType())
80 return Cl::CL_ClassTemporary;
82 return Cl::CL_ArrayTemporary;
84 // No special classification: these don't behave differently from normal
86 return Cl::CL_PRValue;
89 static Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang,
94 return Lang.CPlusPlus ? ClassifyTemporary(E->getType()) : Cl::CL_PRValue;
100 llvm_unreachable("Invalid value category of implicit cast.");
103 static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) {
104 // This function takes the first stab at classifying expressions.
105 const LangOptions &Lang = Ctx.getLangOpts();
107 switch (E->getStmtClass()) {
108 case Stmt::NoStmtClass:
109 #define ABSTRACT_STMT(Kind)
110 #define STMT(Kind, Base) case Expr::Kind##Class:
111 #define EXPR(Kind, Base)
112 #include "clang/AST/StmtNodes.inc"
113 llvm_unreachable("cannot classify a statement");
115 // First come the expressions that are always lvalues, unconditionally.
116 case Expr::ObjCIsaExprClass:
117 // C++ [expr.prim.general]p1: A string literal is an lvalue.
118 case Expr::StringLiteralClass:
119 // @encode is equivalent to its string
120 case Expr::ObjCEncodeExprClass:
121 // __func__ and friends are too.
122 case Expr::PredefinedExprClass:
123 // Property references are lvalues
124 case Expr::ObjCSubscriptRefExprClass:
125 case Expr::ObjCPropertyRefExprClass:
126 // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of...
127 case Expr::CXXTypeidExprClass:
128 // Unresolved lookups and uncorrected typos get classified as lvalues.
129 // FIXME: Is this wise? Should they get their own kind?
130 case Expr::UnresolvedLookupExprClass:
131 case Expr::UnresolvedMemberExprClass:
132 case Expr::TypoExprClass:
133 case Expr::DependentCoawaitExprClass:
134 case Expr::CXXDependentScopeMemberExprClass:
135 case Expr::DependentScopeDeclRefExprClass:
136 // ObjC instance variables are lvalues
137 // FIXME: ObjC++0x might have different rules
138 case Expr::ObjCIvarRefExprClass:
139 case Expr::FunctionParmPackExprClass:
140 case Expr::MSPropertyRefExprClass:
141 case Expr::MSPropertySubscriptExprClass:
142 case Expr::OMPArraySectionExprClass:
143 return Cl::CL_LValue;
145 // C99 6.5.2.5p5 says that compound literals are lvalues.
146 // In C++, they're prvalue temporaries, except for file-scope arrays.
147 case Expr::CompoundLiteralExprClass:
148 return !E->isLValue() ? ClassifyTemporary(E->getType()) : Cl::CL_LValue;
150 // Expressions that are prvalues.
151 case Expr::CXXBoolLiteralExprClass:
152 case Expr::CXXPseudoDestructorExprClass:
153 case Expr::UnaryExprOrTypeTraitExprClass:
154 case Expr::CXXNewExprClass:
155 case Expr::CXXThisExprClass:
156 case Expr::CXXNullPtrLiteralExprClass:
157 case Expr::ImaginaryLiteralClass:
158 case Expr::GNUNullExprClass:
159 case Expr::OffsetOfExprClass:
160 case Expr::CXXThrowExprClass:
161 case Expr::ShuffleVectorExprClass:
162 case Expr::ConvertVectorExprClass:
163 case Expr::IntegerLiteralClass:
164 case Expr::FixedPointLiteralClass:
165 case Expr::CharacterLiteralClass:
166 case Expr::AddrLabelExprClass:
167 case Expr::CXXDeleteExprClass:
168 case Expr::ImplicitValueInitExprClass:
169 case Expr::BlockExprClass:
170 case Expr::FloatingLiteralClass:
171 case Expr::CXXNoexceptExprClass:
172 case Expr::CXXScalarValueInitExprClass:
173 case Expr::TypeTraitExprClass:
174 case Expr::ArrayTypeTraitExprClass:
175 case Expr::ExpressionTraitExprClass:
176 case Expr::ObjCSelectorExprClass:
177 case Expr::ObjCProtocolExprClass:
178 case Expr::ObjCStringLiteralClass:
179 case Expr::ObjCBoxedExprClass:
180 case Expr::ObjCArrayLiteralClass:
181 case Expr::ObjCDictionaryLiteralClass:
182 case Expr::ObjCBoolLiteralExprClass:
183 case Expr::ObjCAvailabilityCheckExprClass:
184 case Expr::ParenListExprClass:
185 case Expr::SizeOfPackExprClass:
186 case Expr::SubstNonTypeTemplateParmPackExprClass:
187 case Expr::AsTypeExprClass:
188 case Expr::ObjCIndirectCopyRestoreExprClass:
189 case Expr::AtomicExprClass:
190 case Expr::CXXFoldExprClass:
191 case Expr::ArrayInitLoopExprClass:
192 case Expr::ArrayInitIndexExprClass:
193 case Expr::NoInitExprClass:
194 case Expr::DesignatedInitUpdateExprClass:
195 return Cl::CL_PRValue;
197 // Next come the complicated cases.
198 case Expr::SubstNonTypeTemplateParmExprClass:
199 return ClassifyInternal(Ctx,
200 cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement());
202 // C, C++98 [expr.sub]p1: The result is an lvalue of type "T".
203 // C++11 (DR1213): in the case of an array operand, the result is an lvalue
204 // if that operand is an lvalue and an xvalue otherwise.
205 // Subscripting vector types is more like member access.
206 case Expr::ArraySubscriptExprClass:
207 if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType())
208 return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase());
209 if (Lang.CPlusPlus11) {
210 // Step over the array-to-pointer decay if present, but not over the
211 // temporary materialization.
212 auto *Base = cast<ArraySubscriptExpr>(E)->getBase()->IgnoreImpCasts();
213 if (Base->getType()->isArrayType())
214 return ClassifyInternal(Ctx, Base);
216 return Cl::CL_LValue;
218 // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a
219 // function or variable and a prvalue otherwise.
220 case Expr::DeclRefExprClass:
221 if (E->getType() == Ctx.UnknownAnyTy)
222 return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl())
223 ? Cl::CL_PRValue : Cl::CL_LValue;
224 return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl());
226 // Member access is complex.
227 case Expr::MemberExprClass:
228 return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E));
230 case Expr::UnaryOperatorClass:
231 switch (cast<UnaryOperator>(E)->getOpcode()) {
232 // C++ [expr.unary.op]p1: The unary * operator performs indirection:
233 // [...] the result is an lvalue referring to the object or function
234 // to which the expression points.
236 return Cl::CL_LValue;
238 // GNU extensions, simply look through them.
240 return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr());
242 // Treat _Real and _Imag basically as if they were member
243 // expressions: l-value only if the operand is a true l-value.
246 const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens();
247 Cl::Kinds K = ClassifyInternal(Ctx, Op);
248 if (K != Cl::CL_LValue) return K;
250 if (isa<ObjCPropertyRefExpr>(Op))
251 return Cl::CL_SubObjCPropertySetting;
252 return Cl::CL_LValue;
255 // C++ [expr.pre.incr]p1: The result is the updated operand; it is an
260 return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue;
263 return Cl::CL_PRValue;
266 case Expr::OpaqueValueExprClass:
267 return ClassifyExprValueKind(Lang, E, E->getValueKind());
269 // Pseudo-object expressions can produce l-values with reference magic.
270 case Expr::PseudoObjectExprClass:
271 return ClassifyExprValueKind(Lang, E,
272 cast<PseudoObjectExpr>(E)->getValueKind());
274 // Implicit casts are lvalues if they're lvalue casts. Other than that, we
275 // only specifically record class temporaries.
276 case Expr::ImplicitCastExprClass:
277 return ClassifyExprValueKind(Lang, E, E->getValueKind());
279 // C++ [expr.prim.general]p4: The presence of parentheses does not affect
280 // whether the expression is an lvalue.
281 case Expr::ParenExprClass:
282 return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr());
284 // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator,
285 // or a void expression if its result expression is, respectively, an
286 // lvalue, a function designator, or a void expression.
287 case Expr::GenericSelectionExprClass:
288 if (cast<GenericSelectionExpr>(E)->isResultDependent())
289 return Cl::CL_PRValue;
290 return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr());
292 case Expr::BinaryOperatorClass:
293 case Expr::CompoundAssignOperatorClass:
294 // C doesn't have any binary expressions that are lvalues.
296 return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E));
297 return Cl::CL_PRValue;
299 case Expr::CallExprClass:
300 case Expr::CXXOperatorCallExprClass:
301 case Expr::CXXMemberCallExprClass:
302 case Expr::UserDefinedLiteralClass:
303 case Expr::CUDAKernelCallExprClass:
304 return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType(Ctx));
306 // __builtin_choose_expr is equivalent to the chosen expression.
307 case Expr::ChooseExprClass:
308 return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr());
310 // Extended vector element access is an lvalue unless there are duplicates
311 // in the shuffle expression.
312 case Expr::ExtVectorElementExprClass:
313 if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements())
314 return Cl::CL_DuplicateVectorComponents;
315 if (cast<ExtVectorElementExpr>(E)->isArrow())
316 return Cl::CL_LValue;
317 return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase());
319 // Simply look at the actual default argument.
320 case Expr::CXXDefaultArgExprClass:
321 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr());
323 // Same idea for default initializers.
324 case Expr::CXXDefaultInitExprClass:
325 return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr());
327 // Same idea for temporary binding.
328 case Expr::CXXBindTemporaryExprClass:
329 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr());
331 // And the cleanups guard.
332 case Expr::ExprWithCleanupsClass:
333 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr());
335 // Casts depend completely on the target type. All casts work the same.
336 case Expr::CStyleCastExprClass:
337 case Expr::CXXFunctionalCastExprClass:
338 case Expr::CXXStaticCastExprClass:
339 case Expr::CXXDynamicCastExprClass:
340 case Expr::CXXReinterpretCastExprClass:
341 case Expr::CXXConstCastExprClass:
342 case Expr::ObjCBridgedCastExprClass:
343 // Only in C++ can casts be interesting at all.
344 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
345 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten());
347 case Expr::CXXUnresolvedConstructExprClass:
348 return ClassifyUnnamed(Ctx,
349 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten());
351 case Expr::BinaryConditionalOperatorClass: {
352 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
353 const auto *co = cast<BinaryConditionalOperator>(E);
354 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
357 case Expr::ConditionalOperatorClass: {
358 // Once again, only C++ is interesting.
359 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
360 const auto *co = cast<ConditionalOperator>(E);
361 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
364 // ObjC message sends are effectively function calls, if the target function
366 case Expr::ObjCMessageExprClass:
367 if (const ObjCMethodDecl *Method =
368 cast<ObjCMessageExpr>(E)->getMethodDecl()) {
369 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getReturnType());
370 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind;
372 return Cl::CL_PRValue;
374 // Some C++ expressions are always class temporaries.
375 case Expr::CXXConstructExprClass:
376 case Expr::CXXInheritedCtorInitExprClass:
377 case Expr::CXXTemporaryObjectExprClass:
378 case Expr::LambdaExprClass:
379 case Expr::CXXStdInitializerListExprClass:
380 return Cl::CL_ClassTemporary;
382 case Expr::VAArgExprClass:
383 return ClassifyUnnamed(Ctx, E->getType());
385 case Expr::DesignatedInitExprClass:
386 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit());
388 case Expr::StmtExprClass: {
389 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt();
390 if (const auto *LastExpr = dyn_cast_or_null<Expr>(S->body_back()))
391 return ClassifyUnnamed(Ctx, LastExpr->getType());
392 return Cl::CL_PRValue;
395 case Expr::CXXUuidofExprClass:
396 return Cl::CL_LValue;
398 case Expr::PackExpansionExprClass:
399 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern());
401 case Expr::MaterializeTemporaryExprClass:
402 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference()
406 case Expr::InitListExprClass:
407 // An init list can be an lvalue if it is bound to a reference and
408 // contains only one element. In that case, we look at that element
409 // for an exact classification. Init list creation takes care of the
410 // value kind for us, so we only need to fine-tune.
412 return ClassifyExprValueKind(Lang, E, E->getValueKind());
413 assert(cast<InitListExpr>(E)->getNumInits() == 1 &&
414 "Only 1-element init lists can be glvalues.");
415 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0));
417 case Expr::CoawaitExprClass:
418 case Expr::CoyieldExprClass:
419 return ClassifyInternal(Ctx, cast<CoroutineSuspendExpr>(E)->getResumeExpr());
422 llvm_unreachable("unhandled expression kind in classification");
425 /// ClassifyDecl - Return the classification of an expression referencing the
426 /// given declaration.
427 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) {
428 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a
429 // function, variable, or data member and a prvalue otherwise.
430 // In C, functions are not lvalues.
431 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an
432 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to
433 // special-case this.
435 if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance())
436 return Cl::CL_MemberFunction;
439 if (const auto *NTTParm = dyn_cast<NonTypeTemplateParmDecl>(D))
440 islvalue = NTTParm->getType()->isReferenceType();
442 islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) ||
443 isa<IndirectFieldDecl>(D) ||
444 isa<BindingDecl>(D) ||
445 (Ctx.getLangOpts().CPlusPlus &&
446 (isa<FunctionDecl>(D) || isa<MSPropertyDecl>(D) ||
447 isa<FunctionTemplateDecl>(D)));
449 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue;
452 /// ClassifyUnnamed - Return the classification of an expression yielding an
453 /// unnamed value of the given type. This applies in particular to function
455 static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) {
456 // In C, function calls are always rvalues.
457 if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue;
459 // C++ [expr.call]p10: A function call is an lvalue if the result type is an
460 // lvalue reference type or an rvalue reference to function type, an xvalue
461 // if the result type is an rvalue reference to object type, and a prvalue
463 if (T->isLValueReferenceType())
464 return Cl::CL_LValue;
465 const auto *RV = T->getAs<RValueReferenceType>();
466 if (!RV) // Could still be a class temporary, though.
467 return ClassifyTemporary(T);
469 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue;
472 static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) {
473 if (E->getType() == Ctx.UnknownAnyTy)
474 return (isa<FunctionDecl>(E->getMemberDecl())
475 ? Cl::CL_PRValue : Cl::CL_LValue);
477 // Handle C first, it's easier.
478 if (!Ctx.getLangOpts().CPlusPlus) {
480 // For dot access, the expression is an lvalue if the first part is. For
481 // arrow access, it always is an lvalue.
483 return Cl::CL_LValue;
484 // ObjC property accesses are not lvalues, but get special treatment.
485 Expr *Base = E->getBase()->IgnoreParens();
486 if (isa<ObjCPropertyRefExpr>(Base))
487 return Cl::CL_SubObjCPropertySetting;
488 return ClassifyInternal(Ctx, Base);
491 NamedDecl *Member = E->getMemberDecl();
492 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2.
493 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then
494 // E1.E2 is an lvalue.
495 if (const auto *Value = dyn_cast<ValueDecl>(Member))
496 if (Value->getType()->isReferenceType())
497 return Cl::CL_LValue;
499 // Otherwise, one of the following rules applies.
500 // -- If E2 is a static member [...] then E1.E2 is an lvalue.
501 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord())
502 return Cl::CL_LValue;
504 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then
505 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue;
506 // otherwise, it is a prvalue.
507 if (isa<FieldDecl>(Member)) {
510 return Cl::CL_LValue;
511 Expr *Base = E->getBase()->IgnoreParenImpCasts();
512 if (isa<ObjCPropertyRefExpr>(Base))
513 return Cl::CL_SubObjCPropertySetting;
514 return ClassifyInternal(Ctx, E->getBase());
517 // -- If E2 is a [...] member function, [...]
518 // -- If it refers to a static member function [...], then E1.E2 is an
520 // -- Otherwise [...] E1.E2 is a prvalue.
521 if (const auto *Method = dyn_cast<CXXMethodDecl>(Member))
522 return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction;
524 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue.
525 // So is everything else we haven't handled yet.
526 return Cl::CL_PRValue;
529 static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) {
530 assert(Ctx.getLangOpts().CPlusPlus &&
531 "This is only relevant for C++.");
532 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand.
533 // Except we override this for writes to ObjC properties.
534 if (E->isAssignmentOp())
535 return (E->getLHS()->getObjectKind() == OK_ObjCProperty
536 ? Cl::CL_PRValue : Cl::CL_LValue);
538 // C++ [expr.comma]p1: the result is of the same value category as its right
540 if (E->getOpcode() == BO_Comma)
541 return ClassifyInternal(Ctx, E->getRHS());
543 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand
544 // is a pointer to a data member is of the same value category as its first
546 if (E->getOpcode() == BO_PtrMemD)
547 return (E->getType()->isFunctionType() ||
548 E->hasPlaceholderType(BuiltinType::BoundMember))
549 ? Cl::CL_MemberFunction
550 : ClassifyInternal(Ctx, E->getLHS());
552 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its
553 // second operand is a pointer to data member and a prvalue otherwise.
554 if (E->getOpcode() == BO_PtrMemI)
555 return (E->getType()->isFunctionType() ||
556 E->hasPlaceholderType(BuiltinType::BoundMember))
557 ? Cl::CL_MemberFunction
560 // All other binary operations are prvalues.
561 return Cl::CL_PRValue;
564 static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True,
566 assert(Ctx.getLangOpts().CPlusPlus &&
567 "This is only relevant for C++.");
570 // If either the second or the third operand has type (cv) void,
571 // one of the following shall hold:
572 if (True->getType()->isVoidType() || False->getType()->isVoidType()) {
573 // The second or the third operand (but not both) is a (possibly
574 // parenthesized) throw-expression; the result is of the [...] value
575 // category of the other.
576 bool TrueIsThrow = isa<CXXThrowExpr>(True->IgnoreParenImpCasts());
577 bool FalseIsThrow = isa<CXXThrowExpr>(False->IgnoreParenImpCasts());
578 if (const Expr *NonThrow = TrueIsThrow ? (FalseIsThrow ? nullptr : False)
579 : (FalseIsThrow ? True : nullptr))
580 return ClassifyInternal(Ctx, NonThrow);
582 // [Otherwise] the result [...] is a prvalue.
583 return Cl::CL_PRValue;
586 // Note that at this point, we have already performed all conversions
587 // according to [expr.cond]p3.
588 // C++ [expr.cond]p4: If the second and third operands are glvalues of the
589 // same value category [...], the result is of that [...] value category.
590 // C++ [expr.cond]p5: Otherwise, the result is a prvalue.
591 Cl::Kinds LCl = ClassifyInternal(Ctx, True),
592 RCl = ClassifyInternal(Ctx, False);
593 return LCl == RCl ? LCl : Cl::CL_PRValue;
596 static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,
597 Cl::Kinds Kind, SourceLocation &Loc) {
598 // As a general rule, we only care about lvalues. But there are some rvalues
599 // for which we want to generate special results.
600 if (Kind == Cl::CL_PRValue) {
601 // For the sake of better diagnostics, we want to specifically recognize
602 // use of the GCC cast-as-lvalue extension.
603 if (const auto *CE = 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 auto *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");