1 //===--- SemaLambda.cpp - Semantic Analysis for C++11 Lambdas -------------===//
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 semantic analysis for C++ lambda expressions.
12 //===----------------------------------------------------------------------===//
13 #include "clang/Sema/DeclSpec.h"
14 #include "TypeLocBuilder.h"
15 #include "clang/AST/ASTLambda.h"
16 #include "clang/AST/ExprCXX.h"
17 #include "clang/Basic/TargetInfo.h"
18 #include "clang/Sema/Initialization.h"
19 #include "clang/Sema/Lookup.h"
20 #include "clang/Sema/Scope.h"
21 #include "clang/Sema/ScopeInfo.h"
22 #include "clang/Sema/SemaInternal.h"
23 #include "clang/Sema/SemaLambda.h"
24 using namespace clang;
27 /// \brief Examines the FunctionScopeInfo stack to determine the nearest
28 /// enclosing lambda (to the current lambda) that is 'capture-ready' for
29 /// the variable referenced in the current lambda (i.e. \p VarToCapture).
30 /// If successful, returns the index into Sema's FunctionScopeInfo stack
31 /// of the capture-ready lambda's LambdaScopeInfo.
33 /// Climbs down the stack of lambdas (deepest nested lambda - i.e. current
34 /// lambda - is on top) to determine the index of the nearest enclosing/outer
35 /// lambda that is ready to capture the \p VarToCapture being referenced in
36 /// the current lambda.
37 /// As we climb down the stack, we want the index of the first such lambda -
38 /// that is the lambda with the highest index that is 'capture-ready'.
40 /// A lambda 'L' is capture-ready for 'V' (var or this) if:
41 /// - its enclosing context is non-dependent
42 /// - and if the chain of lambdas between L and the lambda in which
43 /// V is potentially used (i.e. the lambda at the top of the scope info
44 /// stack), can all capture or have already captured V.
45 /// If \p VarToCapture is 'null' then we are trying to capture 'this'.
47 /// Note that a lambda that is deemed 'capture-ready' still needs to be checked
48 /// for whether it is 'capture-capable' (see
49 /// getStackIndexOfNearestEnclosingCaptureCapableLambda), before it can truly
52 /// \param FunctionScopes - Sema's stack of nested FunctionScopeInfo's (which a
53 /// LambdaScopeInfo inherits from). The current/deepest/innermost lambda
54 /// is at the top of the stack and has the highest index.
55 /// \param VarToCapture - the variable to capture. If NULL, capture 'this'.
57 /// \returns An Optional<unsigned> Index that if evaluates to 'true' contains
58 /// the index (into Sema's FunctionScopeInfo stack) of the innermost lambda
59 /// which is capture-ready. If the return value evaluates to 'false' then
60 /// no lambda is capture-ready for \p VarToCapture.
62 static inline Optional<unsigned>
63 getStackIndexOfNearestEnclosingCaptureReadyLambda(
64 ArrayRef<const clang::sema::FunctionScopeInfo *> FunctionScopes,
65 VarDecl *VarToCapture) {
66 // Label failure to capture.
67 const Optional<unsigned> NoLambdaIsCaptureReady;
70 isa<clang::sema::LambdaScopeInfo>(
71 FunctionScopes[FunctionScopes.size() - 1]) &&
72 "The function on the top of sema's function-info stack must be a lambda");
74 // If VarToCapture is null, we are attempting to capture 'this'.
75 const bool IsCapturingThis = !VarToCapture;
76 const bool IsCapturingVariable = !IsCapturingThis;
78 // Start with the current lambda at the top of the stack (highest index).
79 unsigned CurScopeIndex = FunctionScopes.size() - 1;
80 DeclContext *EnclosingDC =
81 cast<sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex])->CallOperator;
84 const clang::sema::LambdaScopeInfo *LSI =
85 cast<sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex]);
86 // IF we have climbed down to an intervening enclosing lambda that contains
87 // the variable declaration - it obviously can/must not capture the
89 // Since its enclosing DC is dependent, all the lambdas between it and the
90 // innermost nested lambda are dependent (otherwise we wouldn't have
91 // arrived here) - so we don't yet have a lambda that can capture the
93 if (IsCapturingVariable &&
94 VarToCapture->getDeclContext()->Equals(EnclosingDC))
95 return NoLambdaIsCaptureReady;
97 // For an enclosing lambda to be capture ready for an entity, all
98 // intervening lambda's have to be able to capture that entity. If even
99 // one of the intervening lambda's is not capable of capturing the entity
100 // then no enclosing lambda can ever capture that entity.
104 // [](auto b) { #2 <-- an intervening lambda that can never capture 'x'
106 // f(x, c); <-- can not lead to x's speculative capture by #1 or #2
108 // If they do not have a default implicit capture, check to see
109 // if the entity has already been explicitly captured.
110 // If even a single dependent enclosing lambda lacks the capability
111 // to ever capture this variable, there is no further enclosing
112 // non-dependent lambda that can capture this variable.
113 if (LSI->ImpCaptureStyle == sema::LambdaScopeInfo::ImpCap_None) {
114 if (IsCapturingVariable && !LSI->isCaptured(VarToCapture))
115 return NoLambdaIsCaptureReady;
116 if (IsCapturingThis && !LSI->isCXXThisCaptured())
117 return NoLambdaIsCaptureReady;
119 EnclosingDC = getLambdaAwareParentOfDeclContext(EnclosingDC);
121 assert(CurScopeIndex);
123 } while (!EnclosingDC->isTranslationUnit() &&
124 EnclosingDC->isDependentContext() &&
125 isLambdaCallOperator(EnclosingDC));
127 assert(CurScopeIndex < (FunctionScopes.size() - 1));
128 // If the enclosingDC is not dependent, then the immediately nested lambda
129 // (one index above) is capture-ready.
130 if (!EnclosingDC->isDependentContext())
131 return CurScopeIndex + 1;
132 return NoLambdaIsCaptureReady;
135 /// \brief Examines the FunctionScopeInfo stack to determine the nearest
136 /// enclosing lambda (to the current lambda) that is 'capture-capable' for
137 /// the variable referenced in the current lambda (i.e. \p VarToCapture).
138 /// If successful, returns the index into Sema's FunctionScopeInfo stack
139 /// of the capture-capable lambda's LambdaScopeInfo.
141 /// Given the current stack of lambdas being processed by Sema and
142 /// the variable of interest, to identify the nearest enclosing lambda (to the
143 /// current lambda at the top of the stack) that can truly capture
144 /// a variable, it has to have the following two properties:
145 /// a) 'capture-ready' - be the innermost lambda that is 'capture-ready':
146 /// - climb down the stack (i.e. starting from the innermost and examining
147 /// each outer lambda step by step) checking if each enclosing
148 /// lambda can either implicitly or explicitly capture the variable.
149 /// Record the first such lambda that is enclosed in a non-dependent
150 /// context. If no such lambda currently exists return failure.
151 /// b) 'capture-capable' - make sure the 'capture-ready' lambda can truly
152 /// capture the variable by checking all its enclosing lambdas:
153 /// - check if all outer lambdas enclosing the 'capture-ready' lambda
154 /// identified above in 'a' can also capture the variable (this is done
155 /// via tryCaptureVariable for variables and CheckCXXThisCapture for
156 /// 'this' by passing in the index of the Lambda identified in step 'a')
158 /// \param FunctionScopes - Sema's stack of nested FunctionScopeInfo's (which a
159 /// LambdaScopeInfo inherits from). The current/deepest/innermost lambda
160 /// is at the top of the stack.
162 /// \param VarToCapture - the variable to capture. If NULL, capture 'this'.
165 /// \returns An Optional<unsigned> Index that if evaluates to 'true' contains
166 /// the index (into Sema's FunctionScopeInfo stack) of the innermost lambda
167 /// which is capture-capable. If the return value evaluates to 'false' then
168 /// no lambda is capture-capable for \p VarToCapture.
170 Optional<unsigned> clang::getStackIndexOfNearestEnclosingCaptureCapableLambda(
171 ArrayRef<const sema::FunctionScopeInfo *> FunctionScopes,
172 VarDecl *VarToCapture, Sema &S) {
174 const Optional<unsigned> NoLambdaIsCaptureCapable;
176 const Optional<unsigned> OptionalStackIndex =
177 getStackIndexOfNearestEnclosingCaptureReadyLambda(FunctionScopes,
179 if (!OptionalStackIndex)
180 return NoLambdaIsCaptureCapable;
182 const unsigned IndexOfCaptureReadyLambda = OptionalStackIndex.getValue();
183 assert(((IndexOfCaptureReadyLambda != (FunctionScopes.size() - 1)) ||
184 S.getCurGenericLambda()) &&
185 "The capture ready lambda for a potential capture can only be the "
186 "current lambda if it is a generic lambda");
188 const sema::LambdaScopeInfo *const CaptureReadyLambdaLSI =
189 cast<sema::LambdaScopeInfo>(FunctionScopes[IndexOfCaptureReadyLambda]);
191 // If VarToCapture is null, we are attempting to capture 'this'
192 const bool IsCapturingThis = !VarToCapture;
193 const bool IsCapturingVariable = !IsCapturingThis;
195 if (IsCapturingVariable) {
196 // Check if the capture-ready lambda can truly capture the variable, by
197 // checking whether all enclosing lambdas of the capture-ready lambda allow
198 // the capture - i.e. make sure it is capture-capable.
199 QualType CaptureType, DeclRefType;
200 const bool CanCaptureVariable =
201 !S.tryCaptureVariable(VarToCapture,
202 /*ExprVarIsUsedInLoc*/ SourceLocation(),
203 clang::Sema::TryCapture_Implicit,
204 /*EllipsisLoc*/ SourceLocation(),
205 /*BuildAndDiagnose*/ false, CaptureType,
206 DeclRefType, &IndexOfCaptureReadyLambda);
207 if (!CanCaptureVariable)
208 return NoLambdaIsCaptureCapable;
210 // Check if the capture-ready lambda can truly capture 'this' by checking
211 // whether all enclosing lambdas of the capture-ready lambda can capture
213 const bool CanCaptureThis =
214 !S.CheckCXXThisCapture(
215 CaptureReadyLambdaLSI->PotentialThisCaptureLocation,
216 /*Explicit*/ false, /*BuildAndDiagnose*/ false,
217 &IndexOfCaptureReadyLambda);
219 return NoLambdaIsCaptureCapable;
221 return IndexOfCaptureReadyLambda;
224 static inline TemplateParameterList *
225 getGenericLambdaTemplateParameterList(LambdaScopeInfo *LSI, Sema &SemaRef) {
226 if (LSI->GLTemplateParameterList)
227 return LSI->GLTemplateParameterList;
229 if (!LSI->AutoTemplateParams.empty()) {
230 SourceRange IntroRange = LSI->IntroducerRange;
231 SourceLocation LAngleLoc = IntroRange.getBegin();
232 SourceLocation RAngleLoc = IntroRange.getEnd();
233 LSI->GLTemplateParameterList = TemplateParameterList::Create(
235 /*Template kw loc*/ SourceLocation(), LAngleLoc,
236 llvm::makeArrayRef((NamedDecl *const *)LSI->AutoTemplateParams.data(),
237 LSI->AutoTemplateParams.size()),
240 return LSI->GLTemplateParameterList;
243 CXXRecordDecl *Sema::createLambdaClosureType(SourceRange IntroducerRange,
244 TypeSourceInfo *Info,
246 LambdaCaptureDefault CaptureDefault) {
247 DeclContext *DC = CurContext;
248 while (!(DC->isFunctionOrMethod() || DC->isRecord() || DC->isFileContext()))
249 DC = DC->getParent();
250 bool IsGenericLambda = getGenericLambdaTemplateParameterList(getCurLambda(),
252 // Start constructing the lambda class.
253 CXXRecordDecl *Class = CXXRecordDecl::CreateLambda(Context, DC, Info,
254 IntroducerRange.getBegin(),
263 /// \brief Determine whether the given context is or is enclosed in an inline
265 static bool isInInlineFunction(const DeclContext *DC) {
266 while (!DC->isFileContext()) {
267 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(DC))
271 DC = DC->getLexicalParent();
277 MangleNumberingContext *
278 Sema::getCurrentMangleNumberContext(const DeclContext *DC,
279 Decl *&ManglingContextDecl) {
280 // Compute the context for allocating mangling numbers in the current
281 // expression, if the ABI requires them.
282 ManglingContextDecl = ExprEvalContexts.back().ManglingContextDecl;
291 // Default arguments of member function parameters that appear in a class
292 // definition, as well as the initializers of data members, receive special
293 // treatment. Identify them.
294 if (ManglingContextDecl) {
295 if (ParmVarDecl *Param = dyn_cast<ParmVarDecl>(ManglingContextDecl)) {
296 if (const DeclContext *LexicalDC
297 = Param->getDeclContext()->getLexicalParent())
298 if (LexicalDC->isRecord())
299 Kind = DefaultArgument;
300 } else if (VarDecl *Var = dyn_cast<VarDecl>(ManglingContextDecl)) {
301 if (Var->getDeclContext()->isRecord())
302 Kind = StaticDataMember;
303 } else if (isa<FieldDecl>(ManglingContextDecl)) {
308 // Itanium ABI [5.1.7]:
309 // In the following contexts [...] the one-definition rule requires closure
310 // types in different translation units to "correspond":
311 bool IsInNonspecializedTemplate =
312 !ActiveTemplateInstantiations.empty() || CurContext->isDependentContext();
315 // -- the bodies of non-exported nonspecialized template functions
316 // -- the bodies of inline functions
317 if ((IsInNonspecializedTemplate &&
318 !(ManglingContextDecl && isa<ParmVarDecl>(ManglingContextDecl))) ||
319 isInInlineFunction(CurContext)) {
320 ManglingContextDecl = nullptr;
321 return &Context.getManglingNumberContext(DC);
324 ManglingContextDecl = nullptr;
327 case StaticDataMember:
328 // -- the initializers of nonspecialized static members of template classes
329 if (!IsInNonspecializedTemplate) {
330 ManglingContextDecl = nullptr;
333 // Fall through to get the current context.
336 // -- the in-class initializers of class members
337 case DefaultArgument:
338 // -- default arguments appearing in class definitions
339 return &ExprEvalContexts.back().getMangleNumberingContext(Context);
342 llvm_unreachable("unexpected context");
345 MangleNumberingContext &
346 Sema::ExpressionEvaluationContextRecord::getMangleNumberingContext(
348 assert(ManglingContextDecl && "Need to have a context declaration");
349 if (!MangleNumbering)
350 MangleNumbering = Ctx.createMangleNumberingContext();
351 return *MangleNumbering;
354 CXXMethodDecl *Sema::startLambdaDefinition(CXXRecordDecl *Class,
355 SourceRange IntroducerRange,
356 TypeSourceInfo *MethodTypeInfo,
357 SourceLocation EndLoc,
358 ArrayRef<ParmVarDecl *> Params) {
359 QualType MethodType = MethodTypeInfo->getType();
360 TemplateParameterList *TemplateParams =
361 getGenericLambdaTemplateParameterList(getCurLambda(), *this);
362 // If a lambda appears in a dependent context or is a generic lambda (has
363 // template parameters) and has an 'auto' return type, deduce it to a
365 if (Class->isDependentContext() || TemplateParams) {
366 const FunctionProtoType *FPT = MethodType->castAs<FunctionProtoType>();
367 QualType Result = FPT->getReturnType();
368 if (Result->isUndeducedType()) {
369 Result = SubstAutoType(Result, Context.DependentTy);
370 MethodType = Context.getFunctionType(Result, FPT->getParamTypes(),
371 FPT->getExtProtoInfo());
375 // C++11 [expr.prim.lambda]p5:
376 // The closure type for a lambda-expression has a public inline function
377 // call operator (13.5.4) whose parameters and return type are described by
378 // the lambda-expression's parameter-declaration-clause and
379 // trailing-return-type respectively.
380 DeclarationName MethodName
381 = Context.DeclarationNames.getCXXOperatorName(OO_Call);
382 DeclarationNameLoc MethodNameLoc;
383 MethodNameLoc.CXXOperatorName.BeginOpNameLoc
384 = IntroducerRange.getBegin().getRawEncoding();
385 MethodNameLoc.CXXOperatorName.EndOpNameLoc
386 = IntroducerRange.getEnd().getRawEncoding();
387 CXXMethodDecl *Method
388 = CXXMethodDecl::Create(Context, Class, EndLoc,
389 DeclarationNameInfo(MethodName,
390 IntroducerRange.getBegin(),
392 MethodType, MethodTypeInfo,
395 /*isConstExpr=*/false,
397 Method->setAccess(AS_public);
399 // Temporarily set the lexical declaration context to the current
400 // context, so that the Scope stack matches the lexical nesting.
401 Method->setLexicalDeclContext(CurContext);
402 // Create a function template if we have a template parameter list
403 FunctionTemplateDecl *const TemplateMethod = TemplateParams ?
404 FunctionTemplateDecl::Create(Context, Class,
405 Method->getLocation(), MethodName,
408 if (TemplateMethod) {
409 TemplateMethod->setLexicalDeclContext(CurContext);
410 TemplateMethod->setAccess(AS_public);
411 Method->setDescribedFunctionTemplate(TemplateMethod);
415 if (!Params.empty()) {
416 Method->setParams(Params);
417 CheckParmsForFunctionDef(Params,
418 /*CheckParameterNames=*/false);
420 for (auto P : Method->parameters())
421 P->setOwningFunction(Method);
424 Decl *ManglingContextDecl;
425 if (MangleNumberingContext *MCtx =
426 getCurrentMangleNumberContext(Class->getDeclContext(),
427 ManglingContextDecl)) {
428 unsigned ManglingNumber = MCtx->getManglingNumber(Method);
429 Class->setLambdaMangling(ManglingNumber, ManglingContextDecl);
435 void Sema::buildLambdaScope(LambdaScopeInfo *LSI,
436 CXXMethodDecl *CallOperator,
437 SourceRange IntroducerRange,
438 LambdaCaptureDefault CaptureDefault,
439 SourceLocation CaptureDefaultLoc,
441 bool ExplicitResultType,
443 LSI->CallOperator = CallOperator;
444 CXXRecordDecl *LambdaClass = CallOperator->getParent();
445 LSI->Lambda = LambdaClass;
446 if (CaptureDefault == LCD_ByCopy)
447 LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByval;
448 else if (CaptureDefault == LCD_ByRef)
449 LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByref;
450 LSI->CaptureDefaultLoc = CaptureDefaultLoc;
451 LSI->IntroducerRange = IntroducerRange;
452 LSI->ExplicitParams = ExplicitParams;
453 LSI->Mutable = Mutable;
455 if (ExplicitResultType) {
456 LSI->ReturnType = CallOperator->getReturnType();
458 if (!LSI->ReturnType->isDependentType() &&
459 !LSI->ReturnType->isVoidType()) {
460 if (RequireCompleteType(CallOperator->getLocStart(), LSI->ReturnType,
461 diag::err_lambda_incomplete_result)) {
466 LSI->HasImplicitReturnType = true;
470 void Sema::finishLambdaExplicitCaptures(LambdaScopeInfo *LSI) {
471 LSI->finishedExplicitCaptures();
474 void Sema::addLambdaParameters(CXXMethodDecl *CallOperator, Scope *CurScope) {
475 // Introduce our parameters into the function scope
476 for (unsigned p = 0, NumParams = CallOperator->getNumParams();
477 p < NumParams; ++p) {
478 ParmVarDecl *Param = CallOperator->getParamDecl(p);
480 // If this has an identifier, add it to the scope stack.
481 if (CurScope && Param->getIdentifier()) {
482 CheckShadow(CurScope, Param);
484 PushOnScopeChains(Param, CurScope);
489 /// If this expression is an enumerator-like expression of some type
490 /// T, return the type T; otherwise, return null.
492 /// Pointer comparisons on the result here should always work because
493 /// it's derived from either the parent of an EnumConstantDecl
494 /// (i.e. the definition) or the declaration returned by
495 /// EnumType::getDecl() (i.e. the definition).
496 static EnumDecl *findEnumForBlockReturn(Expr *E) {
497 // An expression is an enumerator-like expression of type T if,
498 // ignoring parens and parens-like expressions:
499 E = E->IgnoreParens();
501 // - it is an enumerator whose enum type is T or
502 if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
503 if (EnumConstantDecl *D
504 = dyn_cast<EnumConstantDecl>(DRE->getDecl())) {
505 return cast<EnumDecl>(D->getDeclContext());
510 // - it is a comma expression whose RHS is an enumerator-like
511 // expression of type T or
512 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
513 if (BO->getOpcode() == BO_Comma)
514 return findEnumForBlockReturn(BO->getRHS());
518 // - it is a statement-expression whose value expression is an
519 // enumerator-like expression of type T or
520 if (StmtExpr *SE = dyn_cast<StmtExpr>(E)) {
521 if (Expr *last = dyn_cast_or_null<Expr>(SE->getSubStmt()->body_back()))
522 return findEnumForBlockReturn(last);
526 // - it is a ternary conditional operator (not the GNU ?:
527 // extension) whose second and third operands are
528 // enumerator-like expressions of type T or
529 if (ConditionalOperator *CO = dyn_cast<ConditionalOperator>(E)) {
530 if (EnumDecl *ED = findEnumForBlockReturn(CO->getTrueExpr()))
531 if (ED == findEnumForBlockReturn(CO->getFalseExpr()))
537 // - it is an implicit integral conversion applied to an
538 // enumerator-like expression of type T or
539 if (ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(E)) {
540 // We can sometimes see integral conversions in valid
541 // enumerator-like expressions.
542 if (ICE->getCastKind() == CK_IntegralCast)
543 return findEnumForBlockReturn(ICE->getSubExpr());
545 // Otherwise, just rely on the type.
548 // - it is an expression of that formal enum type.
549 if (const EnumType *ET = E->getType()->getAs<EnumType>()) {
550 return ET->getDecl();
557 /// Attempt to find a type T for which the returned expression of the
558 /// given statement is an enumerator-like expression of that type.
559 static EnumDecl *findEnumForBlockReturn(ReturnStmt *ret) {
560 if (Expr *retValue = ret->getRetValue())
561 return findEnumForBlockReturn(retValue);
565 /// Attempt to find a common type T for which all of the returned
566 /// expressions in a block are enumerator-like expressions of that
568 static EnumDecl *findCommonEnumForBlockReturns(ArrayRef<ReturnStmt*> returns) {
569 ArrayRef<ReturnStmt*>::iterator i = returns.begin(), e = returns.end();
571 // Try to find one for the first return.
572 EnumDecl *ED = findEnumForBlockReturn(*i);
573 if (!ED) return nullptr;
575 // Check that the rest of the returns have the same enum.
576 for (++i; i != e; ++i) {
577 if (findEnumForBlockReturn(*i) != ED)
581 // Never infer an anonymous enum type.
582 if (!ED->hasNameForLinkage()) return nullptr;
587 /// Adjust the given return statements so that they formally return
588 /// the given type. It should require, at most, an IntegralCast.
589 static void adjustBlockReturnsToEnum(Sema &S, ArrayRef<ReturnStmt*> returns,
590 QualType returnType) {
591 for (ArrayRef<ReturnStmt*>::iterator
592 i = returns.begin(), e = returns.end(); i != e; ++i) {
593 ReturnStmt *ret = *i;
594 Expr *retValue = ret->getRetValue();
595 if (S.Context.hasSameType(retValue->getType(), returnType))
598 // Right now we only support integral fixup casts.
599 assert(returnType->isIntegralOrUnscopedEnumerationType());
600 assert(retValue->getType()->isIntegralOrUnscopedEnumerationType());
602 ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(retValue);
604 Expr *E = (cleanups ? cleanups->getSubExpr() : retValue);
605 E = ImplicitCastExpr::Create(S.Context, returnType, CK_IntegralCast,
606 E, /*base path*/ nullptr, VK_RValue);
608 cleanups->setSubExpr(E);
615 void Sema::deduceClosureReturnType(CapturingScopeInfo &CSI) {
616 assert(CSI.HasImplicitReturnType);
617 // If it was ever a placeholder, it had to been deduced to DependentTy.
618 assert(CSI.ReturnType.isNull() || !CSI.ReturnType->isUndeducedType());
619 assert((!isa<LambdaScopeInfo>(CSI) || !getLangOpts().CPlusPlus14) &&
620 "lambda expressions use auto deduction in C++14 onwards");
622 // C++ core issue 975:
623 // If a lambda-expression does not include a trailing-return-type,
624 // it is as if the trailing-return-type denotes the following type:
625 // - if there are no return statements in the compound-statement,
626 // or all return statements return either an expression of type
627 // void or no expression or braced-init-list, the type void;
628 // - otherwise, if all return statements return an expression
629 // and the types of the returned expressions after
630 // lvalue-to-rvalue conversion (4.1 [conv.lval]),
631 // array-to-pointer conversion (4.2 [conv.array]), and
632 // function-to-pointer conversion (4.3 [conv.func]) are the
633 // same, that common type;
634 // - otherwise, the program is ill-formed.
636 // C++ core issue 1048 additionally removes top-level cv-qualifiers
637 // from the types of returned expressions to match the C++14 auto
640 // In addition, in blocks in non-C++ modes, if all of the return
641 // statements are enumerator-like expressions of some type T, where
642 // T has a name for linkage, then we infer the return type of the
643 // block to be that type.
645 // First case: no return statements, implicit void return type.
646 ASTContext &Ctx = getASTContext();
647 if (CSI.Returns.empty()) {
648 // It's possible there were simply no /valid/ return statements.
649 // In this case, the first one we found may have at least given us a type.
650 if (CSI.ReturnType.isNull())
651 CSI.ReturnType = Ctx.VoidTy;
655 // Second case: at least one return statement has dependent type.
656 // Delay type checking until instantiation.
657 assert(!CSI.ReturnType.isNull() && "We should have a tentative return type.");
658 if (CSI.ReturnType->isDependentType())
661 // Try to apply the enum-fuzz rule.
662 if (!getLangOpts().CPlusPlus) {
663 assert(isa<BlockScopeInfo>(CSI));
664 const EnumDecl *ED = findCommonEnumForBlockReturns(CSI.Returns);
666 CSI.ReturnType = Context.getTypeDeclType(ED);
667 adjustBlockReturnsToEnum(*this, CSI.Returns, CSI.ReturnType);
672 // Third case: only one return statement. Don't bother doing extra work!
673 SmallVectorImpl<ReturnStmt*>::iterator I = CSI.Returns.begin(),
674 E = CSI.Returns.end();
678 // General case: many return statements.
679 // Check that they all have compatible return types.
681 // We require the return types to strictly match here.
682 // Note that we've already done the required promotions as part of
683 // processing the return statement.
684 for (; I != E; ++I) {
685 const ReturnStmt *RS = *I;
686 const Expr *RetE = RS->getRetValue();
688 QualType ReturnType =
689 (RetE ? RetE->getType() : Context.VoidTy).getUnqualifiedType();
690 if (Context.getCanonicalFunctionResultType(ReturnType) ==
691 Context.getCanonicalFunctionResultType(CSI.ReturnType))
694 // FIXME: This is a poor diagnostic for ReturnStmts without expressions.
695 // TODO: It's possible that the *first* return is the divergent one.
696 Diag(RS->getLocStart(),
697 diag::err_typecheck_missing_return_type_incompatible)
698 << ReturnType << CSI.ReturnType
699 << isa<LambdaScopeInfo>(CSI);
700 // Continue iterating so that we keep emitting diagnostics.
704 QualType Sema::buildLambdaInitCaptureInitialization(SourceLocation Loc,
709 // Create an 'auto' or 'auto&' TypeSourceInfo that we can use to
711 QualType DeductType = Context.getAutoDeductType();
713 TLB.pushTypeSpec(DeductType).setNameLoc(Loc);
715 DeductType = BuildReferenceType(DeductType, true, Loc, Id);
716 assert(!DeductType.isNull() && "can't build reference to auto");
717 TLB.push<ReferenceTypeLoc>(DeductType).setSigilLoc(Loc);
719 TypeSourceInfo *TSI = TLB.getTypeSourceInfo(Context, DeductType);
721 // Deduce the type of the init capture.
722 QualType DeducedType = deduceVarTypeFromInitializer(
723 /*VarDecl*/nullptr, DeclarationName(Id), DeductType, TSI,
724 SourceRange(Loc, Loc), IsDirectInit, Init);
725 if (DeducedType.isNull())
728 // Are we a non-list direct initialization?
729 ParenListExpr *CXXDirectInit = dyn_cast<ParenListExpr>(Init);
731 // Perform initialization analysis and ensure any implicit conversions
732 // (such as lvalue-to-rvalue) are enforced.
733 InitializedEntity Entity =
734 InitializedEntity::InitializeLambdaCapture(Id, DeducedType, Loc);
735 InitializationKind Kind =
737 ? (CXXDirectInit ? InitializationKind::CreateDirect(
738 Loc, Init->getLocStart(), Init->getLocEnd())
739 : InitializationKind::CreateDirectList(Loc))
740 : InitializationKind::CreateCopy(Loc, Init->getLocStart());
742 MultiExprArg Args = Init;
745 MultiExprArg(CXXDirectInit->getExprs(), CXXDirectInit->getNumExprs());
747 InitializationSequence InitSeq(*this, Entity, Kind, Args);
748 ExprResult Result = InitSeq.Perform(*this, Entity, Kind, Args, &DclT);
750 if (Result.isInvalid())
752 Init = Result.getAs<Expr>();
754 // The init-capture initialization is a full-expression that must be
755 // processed as one before we enter the declcontext of the lambda's
757 Result = ActOnFinishFullExpr(Init, Loc, /*DiscardedValue*/ false,
758 /*IsConstexpr*/ false,
759 /*IsLambdaInitCaptureInitalizer*/ true);
760 if (Result.isInvalid())
763 Init = Result.getAs<Expr>();
767 VarDecl *Sema::createLambdaInitCaptureVarDecl(SourceLocation Loc,
768 QualType InitCaptureType,
770 unsigned InitStyle, Expr *Init) {
771 TypeSourceInfo *TSI = Context.getTrivialTypeSourceInfo(InitCaptureType,
773 // Create a dummy variable representing the init-capture. This is not actually
774 // used as a variable, and only exists as a way to name and refer to the
776 // FIXME: Pass in separate source locations for '&' and identifier.
777 VarDecl *NewVD = VarDecl::Create(Context, CurContext, Loc,
778 Loc, Id, InitCaptureType, TSI, SC_Auto);
779 NewVD->setInitCapture(true);
780 NewVD->setReferenced(true);
781 // FIXME: Pass in a VarDecl::InitializationStyle.
782 NewVD->setInitStyle(static_cast<VarDecl::InitializationStyle>(InitStyle));
783 NewVD->markUsed(Context);
784 NewVD->setInit(Init);
788 FieldDecl *Sema::buildInitCaptureField(LambdaScopeInfo *LSI, VarDecl *Var) {
789 FieldDecl *Field = FieldDecl::Create(
790 Context, LSI->Lambda, Var->getLocation(), Var->getLocation(),
791 nullptr, Var->getType(), Var->getTypeSourceInfo(), nullptr, false,
793 Field->setImplicit(true);
794 Field->setAccess(AS_private);
795 LSI->Lambda->addDecl(Field);
797 LSI->addCapture(Var, /*isBlock*/false, Var->getType()->isReferenceType(),
798 /*isNested*/false, Var->getLocation(), SourceLocation(),
799 Var->getType(), Var->getInit());
803 void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
804 Declarator &ParamInfo,
806 // Determine if we're within a context where we know that the lambda will
807 // be dependent, because there are template parameters in scope.
808 bool KnownDependent = false;
809 LambdaScopeInfo *const LSI = getCurLambda();
810 assert(LSI && "LambdaScopeInfo should be on stack!");
812 // The lambda-expression's closure type might be dependent even if its
813 // semantic context isn't, if it appears within a default argument of a
814 // function template.
815 if (CurScope->getTemplateParamParent())
816 KnownDependent = true;
818 // Determine the signature of the call operator.
819 TypeSourceInfo *MethodTyInfo;
820 bool ExplicitParams = true;
821 bool ExplicitResultType = true;
822 bool ContainsUnexpandedParameterPack = false;
823 SourceLocation EndLoc;
824 SmallVector<ParmVarDecl *, 8> Params;
825 if (ParamInfo.getNumTypeObjects() == 0) {
826 // C++11 [expr.prim.lambda]p4:
827 // If a lambda-expression does not include a lambda-declarator, it is as
828 // if the lambda-declarator were ().
829 FunctionProtoType::ExtProtoInfo EPI(Context.getDefaultCallingConvention(
830 /*IsVariadic=*/false, /*IsCXXMethod=*/true));
831 EPI.HasTrailingReturn = true;
832 EPI.TypeQuals |= DeclSpec::TQ_const;
833 // C++1y [expr.prim.lambda]:
834 // The lambda return type is 'auto', which is replaced by the
835 // trailing-return type if provided and/or deduced from 'return'
837 // We don't do this before C++1y, because we don't support deduced return
839 QualType DefaultTypeForNoTrailingReturn =
840 getLangOpts().CPlusPlus14 ? Context.getAutoDeductType()
841 : Context.DependentTy;
843 Context.getFunctionType(DefaultTypeForNoTrailingReturn, None, EPI);
844 MethodTyInfo = Context.getTrivialTypeSourceInfo(MethodTy);
845 ExplicitParams = false;
846 ExplicitResultType = false;
847 EndLoc = Intro.Range.getEnd();
849 assert(ParamInfo.isFunctionDeclarator() &&
850 "lambda-declarator is a function");
851 DeclaratorChunk::FunctionTypeInfo &FTI = ParamInfo.getFunctionTypeInfo();
853 // C++11 [expr.prim.lambda]p5:
854 // This function call operator is declared const (9.3.1) if and only if
855 // the lambda-expression's parameter-declaration-clause is not followed
856 // by mutable. It is neither virtual nor declared volatile. [...]
857 if (!FTI.hasMutableQualifier())
858 FTI.TypeQuals |= DeclSpec::TQ_const;
860 MethodTyInfo = GetTypeForDeclarator(ParamInfo, CurScope);
861 assert(MethodTyInfo && "no type from lambda-declarator");
862 EndLoc = ParamInfo.getSourceRange().getEnd();
864 ExplicitResultType = FTI.hasTrailingReturnType();
866 if (FTIHasNonVoidParameters(FTI)) {
867 Params.reserve(FTI.NumParams);
868 for (unsigned i = 0, e = FTI.NumParams; i != e; ++i)
869 Params.push_back(cast<ParmVarDecl>(FTI.Params[i].Param));
872 // Check for unexpanded parameter packs in the method type.
873 if (MethodTyInfo->getType()->containsUnexpandedParameterPack())
874 ContainsUnexpandedParameterPack = true;
877 CXXRecordDecl *Class = createLambdaClosureType(Intro.Range, MethodTyInfo,
878 KnownDependent, Intro.Default);
880 CXXMethodDecl *Method = startLambdaDefinition(Class, Intro.Range,
881 MethodTyInfo, EndLoc, Params);
883 CheckCXXDefaultArguments(Method);
885 // Attributes on the lambda apply to the method.
886 ProcessDeclAttributes(CurScope, Method, ParamInfo);
888 // Introduce the function call operator as the current declaration context.
889 PushDeclContext(CurScope, Method);
891 // Build the lambda scope.
892 buildLambdaScope(LSI, Method, Intro.Range, Intro.Default, Intro.DefaultLoc,
893 ExplicitParams, ExplicitResultType, !Method->isConst());
895 // C++11 [expr.prim.lambda]p9:
896 // A lambda-expression whose smallest enclosing scope is a block scope is a
897 // local lambda expression; any other lambda expression shall not have a
898 // capture-default or simple-capture in its lambda-introducer.
900 // For simple-captures, this is covered by the check below that any named
901 // entity is a variable that can be captured.
903 // For DR1632, we also allow a capture-default in any context where we can
904 // odr-use 'this' (in particular, in a default initializer for a non-static
906 if (Intro.Default != LCD_None && !Class->getParent()->isFunctionOrMethod() &&
907 (getCurrentThisType().isNull() ||
908 CheckCXXThisCapture(SourceLocation(), /*Explicit*/true,
909 /*BuildAndDiagnose*/false)))
910 Diag(Intro.DefaultLoc, diag::err_capture_default_non_local);
912 // Distinct capture names, for diagnostics.
913 llvm::SmallSet<IdentifierInfo*, 8> CaptureNames;
915 // Handle explicit captures.
916 SourceLocation PrevCaptureLoc
917 = Intro.Default == LCD_None? Intro.Range.getBegin() : Intro.DefaultLoc;
918 for (auto C = Intro.Captures.begin(), E = Intro.Captures.end(); C != E;
919 PrevCaptureLoc = C->Loc, ++C) {
920 if (C->Kind == LCK_This || C->Kind == LCK_StarThis) {
921 if (C->Kind == LCK_StarThis)
922 Diag(C->Loc, !getLangOpts().CPlusPlus1z
923 ? diag::ext_star_this_lambda_capture_cxx1z
924 : diag::warn_cxx14_compat_star_this_lambda_capture);
926 // C++11 [expr.prim.lambda]p8:
927 // An identifier or this shall not appear more than once in a
929 if (LSI->isCXXThisCaptured()) {
930 Diag(C->Loc, diag::err_capture_more_than_once)
931 << "'this'" << SourceRange(LSI->getCXXThisCapture().getLocation())
932 << FixItHint::CreateRemoval(
933 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
937 // C++1z [expr.prim.lambda]p8:
938 // If a lambda-capture includes a capture-default that is =, each
939 // simple-capture of that lambda-capture shall be of the form "&
940 // identifier" or "* this". [ Note: The form [&,this] is redundant but
941 // accepted for compatibility with ISO C++14. --end note ]
942 if (Intro.Default == LCD_ByCopy && C->Kind != LCK_StarThis) {
943 Diag(C->Loc, diag::err_this_capture_with_copy_default)
944 << FixItHint::CreateRemoval(
945 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
949 // C++11 [expr.prim.lambda]p12:
950 // If this is captured by a local lambda expression, its nearest
951 // enclosing function shall be a non-static member function.
952 QualType ThisCaptureType = getCurrentThisType();
953 if (ThisCaptureType.isNull()) {
954 Diag(C->Loc, diag::err_this_capture) << true;
958 CheckCXXThisCapture(C->Loc, /*Explicit=*/true, /*BuildAndDiagnose*/ true,
959 /*FunctionScopeIndexToStopAtPtr*/ nullptr,
960 C->Kind == LCK_StarThis);
964 assert(C->Id && "missing identifier for capture");
966 if (C->Init.isInvalid())
969 VarDecl *Var = nullptr;
970 if (C->Init.isUsable()) {
971 Diag(C->Loc, getLangOpts().CPlusPlus14
972 ? diag::warn_cxx11_compat_init_capture
973 : diag::ext_init_capture);
975 if (C->Init.get()->containsUnexpandedParameterPack())
976 ContainsUnexpandedParameterPack = true;
977 // If the initializer expression is usable, but the InitCaptureType
978 // is not, then an error has occurred - so ignore the capture for now.
979 // for e.g., [n{0}] { }; <-- if no <initializer_list> is included.
980 // FIXME: we should create the init capture variable and mark it invalid
982 if (C->InitCaptureType.get().isNull())
986 switch (C->InitKind) {
987 case LambdaCaptureInitKind::NoInit:
988 llvm_unreachable("not an init-capture?");
989 case LambdaCaptureInitKind::CopyInit:
990 InitStyle = VarDecl::CInit;
992 case LambdaCaptureInitKind::DirectInit:
993 InitStyle = VarDecl::CallInit;
995 case LambdaCaptureInitKind::ListInit:
996 InitStyle = VarDecl::ListInit;
999 Var = createLambdaInitCaptureVarDecl(C->Loc, C->InitCaptureType.get(),
1000 C->Id, InitStyle, C->Init.get());
1001 // C++1y [expr.prim.lambda]p11:
1002 // An init-capture behaves as if it declares and explicitly
1003 // captures a variable [...] whose declarative region is the
1004 // lambda-expression's compound-statement
1006 PushOnScopeChains(Var, CurScope, false);
1008 assert(C->InitKind == LambdaCaptureInitKind::NoInit &&
1009 "init capture has valid but null init?");
1011 // C++11 [expr.prim.lambda]p8:
1012 // If a lambda-capture includes a capture-default that is &, the
1013 // identifiers in the lambda-capture shall not be preceded by &.
1014 // If a lambda-capture includes a capture-default that is =, [...]
1015 // each identifier it contains shall be preceded by &.
1016 if (C->Kind == LCK_ByRef && Intro.Default == LCD_ByRef) {
1017 Diag(C->Loc, diag::err_reference_capture_with_reference_default)
1018 << FixItHint::CreateRemoval(
1019 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1021 } else if (C->Kind == LCK_ByCopy && Intro.Default == LCD_ByCopy) {
1022 Diag(C->Loc, diag::err_copy_capture_with_copy_default)
1023 << FixItHint::CreateRemoval(
1024 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1028 // C++11 [expr.prim.lambda]p10:
1029 // The identifiers in a capture-list are looked up using the usual
1030 // rules for unqualified name lookup (3.4.1)
1031 DeclarationNameInfo Name(C->Id, C->Loc);
1032 LookupResult R(*this, Name, LookupOrdinaryName);
1033 LookupName(R, CurScope);
1034 if (R.isAmbiguous())
1037 // FIXME: Disable corrections that would add qualification?
1038 CXXScopeSpec ScopeSpec;
1039 if (DiagnoseEmptyLookup(CurScope, ScopeSpec, R,
1040 llvm::make_unique<DeclFilterCCC<VarDecl>>()))
1044 Var = R.getAsSingle<VarDecl>();
1045 if (Var && DiagnoseUseOfDecl(Var, C->Loc))
1049 // C++11 [expr.prim.lambda]p8:
1050 // An identifier or this shall not appear more than once in a
1052 if (!CaptureNames.insert(C->Id).second) {
1053 if (Var && LSI->isCaptured(Var)) {
1054 Diag(C->Loc, diag::err_capture_more_than_once)
1055 << C->Id << SourceRange(LSI->getCapture(Var).getLocation())
1056 << FixItHint::CreateRemoval(
1057 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1059 // Previous capture captured something different (one or both was
1060 // an init-cpature): no fixit.
1061 Diag(C->Loc, diag::err_capture_more_than_once) << C->Id;
1065 // C++11 [expr.prim.lambda]p10:
1066 // [...] each such lookup shall find a variable with automatic storage
1067 // duration declared in the reaching scope of the local lambda expression.
1068 // Note that the 'reaching scope' check happens in tryCaptureVariable().
1070 Diag(C->Loc, diag::err_capture_does_not_name_variable) << C->Id;
1074 // Ignore invalid decls; they'll just confuse the code later.
1075 if (Var->isInvalidDecl())
1078 if (!Var->hasLocalStorage()) {
1079 Diag(C->Loc, diag::err_capture_non_automatic_variable) << C->Id;
1080 Diag(Var->getLocation(), diag::note_previous_decl) << C->Id;
1084 // C++11 [expr.prim.lambda]p23:
1085 // A capture followed by an ellipsis is a pack expansion (14.5.3).
1086 SourceLocation EllipsisLoc;
1087 if (C->EllipsisLoc.isValid()) {
1088 if (Var->isParameterPack()) {
1089 EllipsisLoc = C->EllipsisLoc;
1091 Diag(C->EllipsisLoc, diag::err_pack_expansion_without_parameter_packs)
1092 << SourceRange(C->Loc);
1094 // Just ignore the ellipsis.
1096 } else if (Var->isParameterPack()) {
1097 ContainsUnexpandedParameterPack = true;
1100 if (C->Init.isUsable()) {
1101 buildInitCaptureField(LSI, Var);
1103 TryCaptureKind Kind = C->Kind == LCK_ByRef ? TryCapture_ExplicitByRef :
1104 TryCapture_ExplicitByVal;
1105 tryCaptureVariable(Var, C->Loc, Kind, EllipsisLoc);
1108 finishLambdaExplicitCaptures(LSI);
1110 LSI->ContainsUnexpandedParameterPack = ContainsUnexpandedParameterPack;
1112 // Add lambda parameters into scope.
1113 addLambdaParameters(Method, CurScope);
1115 // Enter a new evaluation context to insulate the lambda from any
1116 // cleanups from the enclosing full-expression.
1117 PushExpressionEvaluationContext(PotentiallyEvaluated);
1120 void Sema::ActOnLambdaError(SourceLocation StartLoc, Scope *CurScope,
1121 bool IsInstantiation) {
1122 LambdaScopeInfo *LSI = cast<LambdaScopeInfo>(FunctionScopes.back());
1124 // Leave the expression-evaluation context.
1125 DiscardCleanupsInEvaluationContext();
1126 PopExpressionEvaluationContext();
1128 // Leave the context of the lambda.
1129 if (!IsInstantiation)
1132 // Finalize the lambda.
1133 CXXRecordDecl *Class = LSI->Lambda;
1134 Class->setInvalidDecl();
1135 SmallVector<Decl*, 4> Fields(Class->fields());
1136 ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
1137 SourceLocation(), nullptr);
1138 CheckCompletedCXXClass(Class);
1140 PopFunctionScopeInfo();
1143 /// \brief Add a lambda's conversion to function pointer, as described in
1144 /// C++11 [expr.prim.lambda]p6.
1145 static void addFunctionPointerConversion(Sema &S,
1146 SourceRange IntroducerRange,
1147 CXXRecordDecl *Class,
1148 CXXMethodDecl *CallOperator) {
1149 // This conversion is explicitly disabled if the lambda's function has
1150 // pass_object_size attributes on any of its parameters.
1151 if (llvm::any_of(CallOperator->parameters(),
1152 std::mem_fn(&ParmVarDecl::hasAttr<PassObjectSizeAttr>)))
1155 // Add the conversion to function pointer.
1156 const FunctionProtoType *CallOpProto =
1157 CallOperator->getType()->getAs<FunctionProtoType>();
1158 const FunctionProtoType::ExtProtoInfo CallOpExtInfo =
1159 CallOpProto->getExtProtoInfo();
1160 QualType PtrToFunctionTy;
1161 QualType InvokerFunctionTy;
1163 FunctionProtoType::ExtProtoInfo InvokerExtInfo = CallOpExtInfo;
1164 CallingConv CC = S.Context.getDefaultCallingConvention(
1165 CallOpProto->isVariadic(), /*IsCXXMethod=*/false);
1166 InvokerExtInfo.ExtInfo = InvokerExtInfo.ExtInfo.withCallingConv(CC);
1167 InvokerExtInfo.TypeQuals = 0;
1168 assert(InvokerExtInfo.RefQualifier == RQ_None &&
1169 "Lambda's call operator should not have a reference qualifier");
1171 S.Context.getFunctionType(CallOpProto->getReturnType(),
1172 CallOpProto->getParamTypes(), InvokerExtInfo);
1173 PtrToFunctionTy = S.Context.getPointerType(InvokerFunctionTy);
1176 // Create the type of the conversion function.
1177 FunctionProtoType::ExtProtoInfo ConvExtInfo(
1178 S.Context.getDefaultCallingConvention(
1179 /*IsVariadic=*/false, /*IsCXXMethod=*/true));
1180 // The conversion function is always const.
1181 ConvExtInfo.TypeQuals = Qualifiers::Const;
1183 S.Context.getFunctionType(PtrToFunctionTy, None, ConvExtInfo);
1185 SourceLocation Loc = IntroducerRange.getBegin();
1186 DeclarationName ConversionName
1187 = S.Context.DeclarationNames.getCXXConversionFunctionName(
1188 S.Context.getCanonicalType(PtrToFunctionTy));
1189 DeclarationNameLoc ConvNameLoc;
1190 // Construct a TypeSourceInfo for the conversion function, and wire
1191 // all the parameters appropriately for the FunctionProtoTypeLoc
1192 // so that everything works during transformation/instantiation of
1194 // The main reason for wiring up the parameters of the conversion
1195 // function with that of the call operator is so that constructs
1196 // like the following work:
1197 // auto L = [](auto b) { <-- 1
1198 // return [](auto a) -> decltype(a) { <-- 2
1202 // int (*fp)(int) = L(5);
1203 // Because the trailing return type can contain DeclRefExprs that refer
1204 // to the original call operator's variables, we hijack the call
1205 // operators ParmVarDecls below.
1206 TypeSourceInfo *ConvNamePtrToFunctionTSI =
1207 S.Context.getTrivialTypeSourceInfo(PtrToFunctionTy, Loc);
1208 ConvNameLoc.NamedType.TInfo = ConvNamePtrToFunctionTSI;
1210 // The conversion function is a conversion to a pointer-to-function.
1211 TypeSourceInfo *ConvTSI = S.Context.getTrivialTypeSourceInfo(ConvTy, Loc);
1212 FunctionProtoTypeLoc ConvTL =
1213 ConvTSI->getTypeLoc().getAs<FunctionProtoTypeLoc>();
1214 // Get the result of the conversion function which is a pointer-to-function.
1215 PointerTypeLoc PtrToFunctionTL =
1216 ConvTL.getReturnLoc().getAs<PointerTypeLoc>();
1217 // Do the same for the TypeSourceInfo that is used to name the conversion
1219 PointerTypeLoc ConvNamePtrToFunctionTL =
1220 ConvNamePtrToFunctionTSI->getTypeLoc().getAs<PointerTypeLoc>();
1222 // Get the underlying function types that the conversion function will
1223 // be converting to (should match the type of the call operator).
1224 FunctionProtoTypeLoc CallOpConvTL =
1225 PtrToFunctionTL.getPointeeLoc().getAs<FunctionProtoTypeLoc>();
1226 FunctionProtoTypeLoc CallOpConvNameTL =
1227 ConvNamePtrToFunctionTL.getPointeeLoc().getAs<FunctionProtoTypeLoc>();
1229 // Wire up the FunctionProtoTypeLocs with the call operator's parameters.
1230 // These parameter's are essentially used to transform the name and
1231 // the type of the conversion operator. By using the same parameters
1232 // as the call operator's we don't have to fix any back references that
1233 // the trailing return type of the call operator's uses (such as
1234 // decltype(some_type<decltype(a)>::type{} + decltype(a){}) etc.)
1235 // - we can simply use the return type of the call operator, and
1236 // everything should work.
1237 SmallVector<ParmVarDecl *, 4> InvokerParams;
1238 for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I) {
1239 ParmVarDecl *From = CallOperator->getParamDecl(I);
1241 InvokerParams.push_back(ParmVarDecl::Create(S.Context,
1242 // Temporarily add to the TU. This is set to the invoker below.
1243 S.Context.getTranslationUnitDecl(),
1244 From->getLocStart(),
1245 From->getLocation(),
1246 From->getIdentifier(),
1248 From->getTypeSourceInfo(),
1249 From->getStorageClass(),
1250 /*DefaultArg=*/nullptr));
1251 CallOpConvTL.setParam(I, From);
1252 CallOpConvNameTL.setParam(I, From);
1255 CXXConversionDecl *Conversion
1256 = CXXConversionDecl::Create(S.Context, Class, Loc,
1257 DeclarationNameInfo(ConversionName,
1261 /*isInline=*/true, /*isExplicit=*/false,
1262 /*isConstexpr=*/false,
1263 CallOperator->getBody()->getLocEnd());
1264 Conversion->setAccess(AS_public);
1265 Conversion->setImplicit(true);
1267 if (Class->isGenericLambda()) {
1268 // Create a template version of the conversion operator, using the template
1269 // parameter list of the function call operator.
1270 FunctionTemplateDecl *TemplateCallOperator =
1271 CallOperator->getDescribedFunctionTemplate();
1272 FunctionTemplateDecl *ConversionTemplate =
1273 FunctionTemplateDecl::Create(S.Context, Class,
1274 Loc, ConversionName,
1275 TemplateCallOperator->getTemplateParameters(),
1277 ConversionTemplate->setAccess(AS_public);
1278 ConversionTemplate->setImplicit(true);
1279 Conversion->setDescribedFunctionTemplate(ConversionTemplate);
1280 Class->addDecl(ConversionTemplate);
1282 Class->addDecl(Conversion);
1283 // Add a non-static member function that will be the result of
1284 // the conversion with a certain unique ID.
1285 DeclarationName InvokerName = &S.Context.Idents.get(
1286 getLambdaStaticInvokerName());
1287 // FIXME: Instead of passing in the CallOperator->getTypeSourceInfo()
1288 // we should get a prebuilt TrivialTypeSourceInfo from Context
1289 // using FunctionTy & Loc and get its TypeLoc as a FunctionProtoTypeLoc
1290 // then rewire the parameters accordingly, by hoisting up the InvokeParams
1291 // loop below and then use its Params to set Invoke->setParams(...) below.
1292 // This would avoid the 'const' qualifier of the calloperator from
1293 // contaminating the type of the invoker, which is currently adjusted
1294 // in SemaTemplateDeduction.cpp:DeduceTemplateArguments. Fixing the
1295 // trailing return type of the invoker would require a visitor to rebuild
1296 // the trailing return type and adjusting all back DeclRefExpr's to refer
1297 // to the new static invoker parameters - not the call operator's.
1298 CXXMethodDecl *Invoke
1299 = CXXMethodDecl::Create(S.Context, Class, Loc,
1300 DeclarationNameInfo(InvokerName, Loc),
1302 CallOperator->getTypeSourceInfo(),
1303 SC_Static, /*IsInline=*/true,
1304 /*IsConstexpr=*/false,
1305 CallOperator->getBody()->getLocEnd());
1306 for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I)
1307 InvokerParams[I]->setOwningFunction(Invoke);
1308 Invoke->setParams(InvokerParams);
1309 Invoke->setAccess(AS_private);
1310 Invoke->setImplicit(true);
1311 if (Class->isGenericLambda()) {
1312 FunctionTemplateDecl *TemplateCallOperator =
1313 CallOperator->getDescribedFunctionTemplate();
1314 FunctionTemplateDecl *StaticInvokerTemplate = FunctionTemplateDecl::Create(
1315 S.Context, Class, Loc, InvokerName,
1316 TemplateCallOperator->getTemplateParameters(),
1318 StaticInvokerTemplate->setAccess(AS_private);
1319 StaticInvokerTemplate->setImplicit(true);
1320 Invoke->setDescribedFunctionTemplate(StaticInvokerTemplate);
1321 Class->addDecl(StaticInvokerTemplate);
1323 Class->addDecl(Invoke);
1326 /// \brief Add a lambda's conversion to block pointer.
1327 static void addBlockPointerConversion(Sema &S,
1328 SourceRange IntroducerRange,
1329 CXXRecordDecl *Class,
1330 CXXMethodDecl *CallOperator) {
1331 const FunctionProtoType *Proto =
1332 CallOperator->getType()->getAs<FunctionProtoType>();
1334 // The function type inside the block pointer type is the same as the call
1335 // operator with some tweaks. The calling convention is the default free
1336 // function convention, and the type qualifications are lost.
1337 FunctionProtoType::ExtProtoInfo BlockEPI = Proto->getExtProtoInfo();
1339 BlockEPI.ExtInfo.withCallingConv(S.Context.getDefaultCallingConvention(
1340 Proto->isVariadic(), /*IsCXXMethod=*/false));
1341 BlockEPI.TypeQuals = 0;
1342 QualType FunctionTy = S.Context.getFunctionType(
1343 Proto->getReturnType(), Proto->getParamTypes(), BlockEPI);
1344 QualType BlockPtrTy = S.Context.getBlockPointerType(FunctionTy);
1346 FunctionProtoType::ExtProtoInfo ConversionEPI(
1347 S.Context.getDefaultCallingConvention(
1348 /*IsVariadic=*/false, /*IsCXXMethod=*/true));
1349 ConversionEPI.TypeQuals = Qualifiers::Const;
1350 QualType ConvTy = S.Context.getFunctionType(BlockPtrTy, None, ConversionEPI);
1352 SourceLocation Loc = IntroducerRange.getBegin();
1353 DeclarationName Name
1354 = S.Context.DeclarationNames.getCXXConversionFunctionName(
1355 S.Context.getCanonicalType(BlockPtrTy));
1356 DeclarationNameLoc NameLoc;
1357 NameLoc.NamedType.TInfo = S.Context.getTrivialTypeSourceInfo(BlockPtrTy, Loc);
1358 CXXConversionDecl *Conversion
1359 = CXXConversionDecl::Create(S.Context, Class, Loc,
1360 DeclarationNameInfo(Name, Loc, NameLoc),
1362 S.Context.getTrivialTypeSourceInfo(ConvTy, Loc),
1363 /*isInline=*/true, /*isExplicit=*/false,
1364 /*isConstexpr=*/false,
1365 CallOperator->getBody()->getLocEnd());
1366 Conversion->setAccess(AS_public);
1367 Conversion->setImplicit(true);
1368 Class->addDecl(Conversion);
1371 static ExprResult performLambdaVarCaptureInitialization(
1372 Sema &S, LambdaScopeInfo::Capture &Capture,
1374 SmallVectorImpl<VarDecl *> &ArrayIndexVars,
1375 SmallVectorImpl<unsigned> &ArrayIndexStarts) {
1376 assert(Capture.isVariableCapture() && "not a variable capture");
1378 auto *Var = Capture.getVariable();
1379 SourceLocation Loc = Capture.getLocation();
1381 // C++11 [expr.prim.lambda]p21:
1382 // When the lambda-expression is evaluated, the entities that
1383 // are captured by copy are used to direct-initialize each
1384 // corresponding non-static data member of the resulting closure
1385 // object. (For array members, the array elements are
1386 // direct-initialized in increasing subscript order.) These
1387 // initializations are performed in the (unspecified) order in
1388 // which the non-static data members are declared.
1390 // C++ [expr.prim.lambda]p12:
1391 // An entity captured by a lambda-expression is odr-used (3.2) in
1392 // the scope containing the lambda-expression.
1393 ExprResult RefResult = S.BuildDeclarationNameExpr(
1394 CXXScopeSpec(), DeclarationNameInfo(Var->getDeclName(), Loc), Var);
1395 if (RefResult.isInvalid())
1397 Expr *Ref = RefResult.get();
1399 QualType FieldType = Field->getType();
1401 // When the variable has array type, create index variables for each
1402 // dimension of the array. We use these index variables to subscript
1403 // the source array, and other clients (e.g., CodeGen) will perform
1404 // the necessary iteration with these index variables.
1406 // FIXME: This is dumb. Add a proper AST representation for array
1407 // copy-construction and use it here.
1408 SmallVector<VarDecl *, 4> IndexVariables;
1409 QualType BaseType = FieldType;
1410 QualType SizeType = S.Context.getSizeType();
1411 ArrayIndexStarts.push_back(ArrayIndexVars.size());
1412 while (const ConstantArrayType *Array
1413 = S.Context.getAsConstantArrayType(BaseType)) {
1414 // Create the iteration variable for this array index.
1415 IdentifierInfo *IterationVarName = nullptr;
1418 llvm::raw_svector_ostream OS(Str);
1419 OS << "__i" << IndexVariables.size();
1420 IterationVarName = &S.Context.Idents.get(OS.str());
1422 VarDecl *IterationVar = VarDecl::Create(
1423 S.Context, S.CurContext, Loc, Loc, IterationVarName, SizeType,
1424 S.Context.getTrivialTypeSourceInfo(SizeType, Loc), SC_None);
1425 IterationVar->setImplicit();
1426 IndexVariables.push_back(IterationVar);
1427 ArrayIndexVars.push_back(IterationVar);
1429 // Create a reference to the iteration variable.
1430 ExprResult IterationVarRef =
1431 S.BuildDeclRefExpr(IterationVar, SizeType, VK_LValue, Loc);
1432 assert(!IterationVarRef.isInvalid() &&
1433 "Reference to invented variable cannot fail!");
1434 IterationVarRef = S.DefaultLvalueConversion(IterationVarRef.get());
1435 assert(!IterationVarRef.isInvalid() &&
1436 "Conversion of invented variable cannot fail!");
1438 // Subscript the array with this iteration variable.
1439 ExprResult Subscript =
1440 S.CreateBuiltinArraySubscriptExpr(Ref, Loc, IterationVarRef.get(), Loc);
1441 if (Subscript.isInvalid())
1444 Ref = Subscript.get();
1445 BaseType = Array->getElementType();
1448 // Construct the entity that we will be initializing. For an array, this
1449 // will be first element in the array, which may require several levels
1450 // of array-subscript entities.
1451 SmallVector<InitializedEntity, 4> Entities;
1452 Entities.reserve(1 + IndexVariables.size());
1453 Entities.push_back(InitializedEntity::InitializeLambdaCapture(
1454 Var->getIdentifier(), FieldType, Loc));
1455 for (unsigned I = 0, N = IndexVariables.size(); I != N; ++I)
1457 InitializedEntity::InitializeElement(S.Context, 0, Entities.back()));
1459 InitializationKind InitKind = InitializationKind::CreateDirect(Loc, Loc, Loc);
1460 InitializationSequence Init(S, Entities.back(), InitKind, Ref);
1461 return Init.Perform(S, Entities.back(), InitKind, Ref);
1464 ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
1466 LambdaScopeInfo LSI = *cast<LambdaScopeInfo>(FunctionScopes.back());
1467 ActOnFinishFunctionBody(LSI.CallOperator, Body);
1468 return BuildLambdaExpr(StartLoc, Body->getLocEnd(), &LSI);
1471 static LambdaCaptureDefault
1472 mapImplicitCaptureStyle(CapturingScopeInfo::ImplicitCaptureStyle ICS) {
1474 case CapturingScopeInfo::ImpCap_None:
1476 case CapturingScopeInfo::ImpCap_LambdaByval:
1478 case CapturingScopeInfo::ImpCap_CapturedRegion:
1479 case CapturingScopeInfo::ImpCap_LambdaByref:
1481 case CapturingScopeInfo::ImpCap_Block:
1482 llvm_unreachable("block capture in lambda");
1484 llvm_unreachable("Unknown implicit capture style");
1487 ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
1488 LambdaScopeInfo *LSI) {
1489 // Collect information from the lambda scope.
1490 SmallVector<LambdaCapture, 4> Captures;
1491 SmallVector<Expr *, 4> CaptureInits;
1492 SourceLocation CaptureDefaultLoc = LSI->CaptureDefaultLoc;
1493 LambdaCaptureDefault CaptureDefault =
1494 mapImplicitCaptureStyle(LSI->ImpCaptureStyle);
1495 CXXRecordDecl *Class;
1496 CXXMethodDecl *CallOperator;
1497 SourceRange IntroducerRange;
1498 bool ExplicitParams;
1499 bool ExplicitResultType;
1500 CleanupInfo LambdaCleanup;
1501 bool ContainsUnexpandedParameterPack;
1502 SmallVector<VarDecl *, 4> ArrayIndexVars;
1503 SmallVector<unsigned, 4> ArrayIndexStarts;
1505 CallOperator = LSI->CallOperator;
1506 Class = LSI->Lambda;
1507 IntroducerRange = LSI->IntroducerRange;
1508 ExplicitParams = LSI->ExplicitParams;
1509 ExplicitResultType = !LSI->HasImplicitReturnType;
1510 LambdaCleanup = LSI->Cleanup;
1511 ContainsUnexpandedParameterPack = LSI->ContainsUnexpandedParameterPack;
1513 CallOperator->setLexicalDeclContext(Class);
1514 Decl *TemplateOrNonTemplateCallOperatorDecl =
1515 CallOperator->getDescribedFunctionTemplate()
1516 ? CallOperator->getDescribedFunctionTemplate()
1517 : cast<Decl>(CallOperator);
1519 TemplateOrNonTemplateCallOperatorDecl->setLexicalDeclContext(Class);
1520 Class->addDecl(TemplateOrNonTemplateCallOperatorDecl);
1522 PopExpressionEvaluationContext();
1524 // Translate captures.
1525 auto CurField = Class->field_begin();
1526 for (unsigned I = 0, N = LSI->Captures.size(); I != N; ++I, ++CurField) {
1527 LambdaScopeInfo::Capture From = LSI->Captures[I];
1528 assert(!From.isBlockCapture() && "Cannot capture __block variables");
1529 bool IsImplicit = I >= LSI->NumExplicitCaptures;
1531 // Handle 'this' capture.
1532 if (From.isThisCapture()) {
1534 LambdaCapture(From.getLocation(), IsImplicit,
1535 From.isCopyCapture() ? LCK_StarThis : LCK_This));
1536 CaptureInits.push_back(From.getInitExpr());
1537 ArrayIndexStarts.push_back(ArrayIndexVars.size());
1540 if (From.isVLATypeCapture()) {
1542 LambdaCapture(From.getLocation(), IsImplicit, LCK_VLAType));
1543 CaptureInits.push_back(nullptr);
1544 ArrayIndexStarts.push_back(ArrayIndexVars.size());
1548 VarDecl *Var = From.getVariable();
1549 LambdaCaptureKind Kind = From.isCopyCapture() ? LCK_ByCopy : LCK_ByRef;
1550 Captures.push_back(LambdaCapture(From.getLocation(), IsImplicit, Kind,
1551 Var, From.getEllipsisLoc()));
1552 Expr *Init = From.getInitExpr();
1554 auto InitResult = performLambdaVarCaptureInitialization(
1555 *this, From, *CurField, ArrayIndexVars, ArrayIndexStarts);
1556 if (InitResult.isInvalid())
1558 Init = InitResult.get();
1560 ArrayIndexStarts.push_back(ArrayIndexVars.size());
1562 CaptureInits.push_back(Init);
1565 // C++11 [expr.prim.lambda]p6:
1566 // The closure type for a lambda-expression with no lambda-capture
1567 // has a public non-virtual non-explicit const conversion function
1568 // to pointer to function having the same parameter and return
1569 // types as the closure type's function call operator.
1570 if (Captures.empty() && CaptureDefault == LCD_None)
1571 addFunctionPointerConversion(*this, IntroducerRange, Class,
1575 // The closure type for a lambda-expression has a public non-virtual
1576 // non-explicit const conversion function to a block pointer having the
1577 // same parameter and return types as the closure type's function call
1579 // FIXME: Fix generic lambda to block conversions.
1580 if (getLangOpts().Blocks && getLangOpts().ObjC1 &&
1581 !Class->isGenericLambda())
1582 addBlockPointerConversion(*this, IntroducerRange, Class, CallOperator);
1584 // Finalize the lambda class.
1585 SmallVector<Decl*, 4> Fields(Class->fields());
1586 ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
1587 SourceLocation(), nullptr);
1588 CheckCompletedCXXClass(Class);
1591 Cleanup.mergeFrom(LambdaCleanup);
1593 LambdaExpr *Lambda = LambdaExpr::Create(Context, Class, IntroducerRange,
1594 CaptureDefault, CaptureDefaultLoc,
1596 ExplicitParams, ExplicitResultType,
1597 CaptureInits, ArrayIndexVars,
1598 ArrayIndexStarts, EndLoc,
1599 ContainsUnexpandedParameterPack);
1601 if (!CurContext->isDependentContext()) {
1602 switch (ExprEvalContexts.back().Context) {
1603 // C++11 [expr.prim.lambda]p2:
1604 // A lambda-expression shall not appear in an unevaluated operand
1607 case UnevaluatedAbstract:
1608 // C++1y [expr.const]p2:
1609 // A conditional-expression e is a core constant expression unless the
1610 // evaluation of e, following the rules of the abstract machine, would
1611 // evaluate [...] a lambda-expression.
1613 // This is technically incorrect, there are some constant evaluated contexts
1614 // where this should be allowed. We should probably fix this when DR1607 is
1615 // ratified, it lays out the exact set of conditions where we shouldn't
1616 // allow a lambda-expression.
1617 case ConstantEvaluated:
1618 // We don't actually diagnose this case immediately, because we
1619 // could be within a context where we might find out later that
1620 // the expression is potentially evaluated (e.g., for typeid).
1621 ExprEvalContexts.back().Lambdas.push_back(Lambda);
1624 case DiscardedStatement:
1625 case PotentiallyEvaluated:
1626 case PotentiallyEvaluatedIfUsed:
1631 return MaybeBindToTemporary(Lambda);
1634 ExprResult Sema::BuildBlockForLambdaConversion(SourceLocation CurrentLocation,
1635 SourceLocation ConvLocation,
1636 CXXConversionDecl *Conv,
1638 // Make sure that the lambda call operator is marked used.
1639 CXXRecordDecl *Lambda = Conv->getParent();
1640 CXXMethodDecl *CallOperator
1641 = cast<CXXMethodDecl>(
1643 Context.DeclarationNames.getCXXOperatorName(OO_Call)).front());
1644 CallOperator->setReferenced();
1645 CallOperator->markUsed(Context);
1647 ExprResult Init = PerformCopyInitialization(
1648 InitializedEntity::InitializeBlock(ConvLocation,
1651 CurrentLocation, Src);
1652 if (!Init.isInvalid())
1653 Init = ActOnFinishFullExpr(Init.get());
1655 if (Init.isInvalid())
1658 // Create the new block to be returned.
1659 BlockDecl *Block = BlockDecl::Create(Context, CurContext, ConvLocation);
1661 // Set the type information.
1662 Block->setSignatureAsWritten(CallOperator->getTypeSourceInfo());
1663 Block->setIsVariadic(CallOperator->isVariadic());
1664 Block->setBlockMissingReturnType(false);
1667 SmallVector<ParmVarDecl *, 4> BlockParams;
1668 for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I) {
1669 ParmVarDecl *From = CallOperator->getParamDecl(I);
1670 BlockParams.push_back(ParmVarDecl::Create(Context, Block,
1671 From->getLocStart(),
1672 From->getLocation(),
1673 From->getIdentifier(),
1675 From->getTypeSourceInfo(),
1676 From->getStorageClass(),
1677 /*DefaultArg=*/nullptr));
1679 Block->setParams(BlockParams);
1681 Block->setIsConversionFromLambda(true);
1683 // Add capture. The capture uses a fake variable, which doesn't correspond
1684 // to any actual memory location. However, the initializer copy-initializes
1685 // the lambda object.
1686 TypeSourceInfo *CapVarTSI =
1687 Context.getTrivialTypeSourceInfo(Src->getType());
1688 VarDecl *CapVar = VarDecl::Create(Context, Block, ConvLocation,
1689 ConvLocation, nullptr,
1690 Src->getType(), CapVarTSI,
1692 BlockDecl::Capture Capture(/*Variable=*/CapVar, /*ByRef=*/false,
1693 /*Nested=*/false, /*Copy=*/Init.get());
1694 Block->setCaptures(Context, Capture, /*CapturesCXXThis=*/false);
1696 // Add a fake function body to the block. IR generation is responsible
1697 // for filling in the actual body, which cannot be expressed as an AST.
1698 Block->setBody(new (Context) CompoundStmt(ConvLocation));
1700 // Create the block literal expression.
1701 Expr *BuildBlock = new (Context) BlockExpr(Block, Conv->getConversionType());
1702 ExprCleanupObjects.push_back(Block);
1703 Cleanup.setExprNeedsCleanups(true);