1 //===--- SemaLambda.cpp - Semantic Analysis for C++11 Lambdas -------------===//
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 semantic analysis for C++ lambda expressions.
11 //===----------------------------------------------------------------------===//
12 #include "clang/Sema/DeclSpec.h"
13 #include "TypeLocBuilder.h"
14 #include "clang/AST/ASTLambda.h"
15 #include "clang/AST/ExprCXX.h"
16 #include "clang/Basic/TargetInfo.h"
17 #include "clang/Sema/Initialization.h"
18 #include "clang/Sema/Lookup.h"
19 #include "clang/Sema/Scope.h"
20 #include "clang/Sema/ScopeInfo.h"
21 #include "clang/Sema/SemaInternal.h"
22 #include "clang/Sema/SemaLambda.h"
23 #include "llvm/ADT/STLExtras.h"
24 using namespace clang;
27 /// 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;
69 // Ignore all inner captured regions.
70 unsigned CurScopeIndex = FunctionScopes.size() - 1;
71 while (CurScopeIndex > 0 && isa<clang::sema::CapturedRegionScopeInfo>(
72 FunctionScopes[CurScopeIndex]))
75 isa<clang::sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex]) &&
76 "The function on the top of sema's function-info stack must be a lambda");
78 // If VarToCapture is null, we are attempting to capture 'this'.
79 const bool IsCapturingThis = !VarToCapture;
80 const bool IsCapturingVariable = !IsCapturingThis;
82 // Start with the current lambda at the top of the stack (highest index).
83 DeclContext *EnclosingDC =
84 cast<sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex])->CallOperator;
87 const clang::sema::LambdaScopeInfo *LSI =
88 cast<sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex]);
89 // IF we have climbed down to an intervening enclosing lambda that contains
90 // the variable declaration - it obviously can/must not capture the
92 // Since its enclosing DC is dependent, all the lambdas between it and the
93 // innermost nested lambda are dependent (otherwise we wouldn't have
94 // arrived here) - so we don't yet have a lambda that can capture the
96 if (IsCapturingVariable &&
97 VarToCapture->getDeclContext()->Equals(EnclosingDC))
98 return NoLambdaIsCaptureReady;
100 // For an enclosing lambda to be capture ready for an entity, all
101 // intervening lambda's have to be able to capture that entity. If even
102 // one of the intervening lambda's is not capable of capturing the entity
103 // then no enclosing lambda can ever capture that entity.
107 // [](auto b) { #2 <-- an intervening lambda that can never capture 'x'
109 // f(x, c); <-- can not lead to x's speculative capture by #1 or #2
111 // If they do not have a default implicit capture, check to see
112 // if the entity has already been explicitly captured.
113 // If even a single dependent enclosing lambda lacks the capability
114 // to ever capture this variable, there is no further enclosing
115 // non-dependent lambda that can capture this variable.
116 if (LSI->ImpCaptureStyle == sema::LambdaScopeInfo::ImpCap_None) {
117 if (IsCapturingVariable && !LSI->isCaptured(VarToCapture))
118 return NoLambdaIsCaptureReady;
119 if (IsCapturingThis && !LSI->isCXXThisCaptured())
120 return NoLambdaIsCaptureReady;
122 EnclosingDC = getLambdaAwareParentOfDeclContext(EnclosingDC);
124 assert(CurScopeIndex);
126 } while (!EnclosingDC->isTranslationUnit() &&
127 EnclosingDC->isDependentContext() &&
128 isLambdaCallOperator(EnclosingDC));
130 assert(CurScopeIndex < (FunctionScopes.size() - 1));
131 // If the enclosingDC is not dependent, then the immediately nested lambda
132 // (one index above) is capture-ready.
133 if (!EnclosingDC->isDependentContext())
134 return CurScopeIndex + 1;
135 return NoLambdaIsCaptureReady;
138 /// Examines the FunctionScopeInfo stack to determine the nearest
139 /// enclosing lambda (to the current lambda) that is 'capture-capable' for
140 /// the variable referenced in the current lambda (i.e. \p VarToCapture).
141 /// If successful, returns the index into Sema's FunctionScopeInfo stack
142 /// of the capture-capable lambda's LambdaScopeInfo.
144 /// Given the current stack of lambdas being processed by Sema and
145 /// the variable of interest, to identify the nearest enclosing lambda (to the
146 /// current lambda at the top of the stack) that can truly capture
147 /// a variable, it has to have the following two properties:
148 /// a) 'capture-ready' - be the innermost lambda that is 'capture-ready':
149 /// - climb down the stack (i.e. starting from the innermost and examining
150 /// each outer lambda step by step) checking if each enclosing
151 /// lambda can either implicitly or explicitly capture the variable.
152 /// Record the first such lambda that is enclosed in a non-dependent
153 /// context. If no such lambda currently exists return failure.
154 /// b) 'capture-capable' - make sure the 'capture-ready' lambda can truly
155 /// capture the variable by checking all its enclosing lambdas:
156 /// - check if all outer lambdas enclosing the 'capture-ready' lambda
157 /// identified above in 'a' can also capture the variable (this is done
158 /// via tryCaptureVariable for variables and CheckCXXThisCapture for
159 /// 'this' by passing in the index of the Lambda identified in step 'a')
161 /// \param FunctionScopes - Sema's stack of nested FunctionScopeInfo's (which a
162 /// LambdaScopeInfo inherits from). The current/deepest/innermost lambda
163 /// is at the top of the stack.
165 /// \param VarToCapture - the variable to capture. If NULL, capture 'this'.
168 /// \returns An Optional<unsigned> Index that if evaluates to 'true' contains
169 /// the index (into Sema's FunctionScopeInfo stack) of the innermost lambda
170 /// which is capture-capable. If the return value evaluates to 'false' then
171 /// no lambda is capture-capable for \p VarToCapture.
173 Optional<unsigned> clang::getStackIndexOfNearestEnclosingCaptureCapableLambda(
174 ArrayRef<const sema::FunctionScopeInfo *> FunctionScopes,
175 VarDecl *VarToCapture, Sema &S) {
177 const Optional<unsigned> NoLambdaIsCaptureCapable;
179 const Optional<unsigned> OptionalStackIndex =
180 getStackIndexOfNearestEnclosingCaptureReadyLambda(FunctionScopes,
182 if (!OptionalStackIndex)
183 return NoLambdaIsCaptureCapable;
185 const unsigned IndexOfCaptureReadyLambda = OptionalStackIndex.getValue();
186 assert(((IndexOfCaptureReadyLambda != (FunctionScopes.size() - 1)) ||
187 S.getCurGenericLambda()) &&
188 "The capture ready lambda for a potential capture can only be the "
189 "current lambda if it is a generic lambda");
191 const sema::LambdaScopeInfo *const CaptureReadyLambdaLSI =
192 cast<sema::LambdaScopeInfo>(FunctionScopes[IndexOfCaptureReadyLambda]);
194 // If VarToCapture is null, we are attempting to capture 'this'
195 const bool IsCapturingThis = !VarToCapture;
196 const bool IsCapturingVariable = !IsCapturingThis;
198 if (IsCapturingVariable) {
199 // Check if the capture-ready lambda can truly capture the variable, by
200 // checking whether all enclosing lambdas of the capture-ready lambda allow
201 // the capture - i.e. make sure it is capture-capable.
202 QualType CaptureType, DeclRefType;
203 const bool CanCaptureVariable =
204 !S.tryCaptureVariable(VarToCapture,
205 /*ExprVarIsUsedInLoc*/ SourceLocation(),
206 clang::Sema::TryCapture_Implicit,
207 /*EllipsisLoc*/ SourceLocation(),
208 /*BuildAndDiagnose*/ false, CaptureType,
209 DeclRefType, &IndexOfCaptureReadyLambda);
210 if (!CanCaptureVariable)
211 return NoLambdaIsCaptureCapable;
213 // Check if the capture-ready lambda can truly capture 'this' by checking
214 // whether all enclosing lambdas of the capture-ready lambda can capture
216 const bool CanCaptureThis =
217 !S.CheckCXXThisCapture(
218 CaptureReadyLambdaLSI->PotentialThisCaptureLocation,
219 /*Explicit*/ false, /*BuildAndDiagnose*/ false,
220 &IndexOfCaptureReadyLambda);
222 return NoLambdaIsCaptureCapable;
224 return IndexOfCaptureReadyLambda;
227 static inline TemplateParameterList *
228 getGenericLambdaTemplateParameterList(LambdaScopeInfo *LSI, Sema &SemaRef) {
229 if (!LSI->GLTemplateParameterList && !LSI->TemplateParams.empty()) {
230 LSI->GLTemplateParameterList = TemplateParameterList::Create(
232 /*Template kw loc*/ SourceLocation(),
233 /*L angle loc*/ LSI->ExplicitTemplateParamsRange.getBegin(),
235 /*R angle loc*/LSI->ExplicitTemplateParamsRange.getEnd(),
238 return LSI->GLTemplateParameterList;
241 CXXRecordDecl *Sema::createLambdaClosureType(SourceRange IntroducerRange,
242 TypeSourceInfo *Info,
244 LambdaCaptureDefault CaptureDefault) {
245 DeclContext *DC = CurContext;
246 while (!(DC->isFunctionOrMethod() || DC->isRecord() || DC->isFileContext()))
247 DC = DC->getParent();
248 bool IsGenericLambda = getGenericLambdaTemplateParameterList(getCurLambda(),
250 // Start constructing the lambda class.
251 CXXRecordDecl *Class = CXXRecordDecl::CreateLambda(Context, DC, Info,
252 IntroducerRange.getBegin(),
261 /// Determine whether the given context is or is enclosed in an inline
263 static bool isInInlineFunction(const DeclContext *DC) {
264 while (!DC->isFileContext()) {
265 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(DC))
269 DC = DC->getLexicalParent();
275 MangleNumberingContext *
276 Sema::getCurrentMangleNumberContext(const DeclContext *DC,
277 Decl *&ManglingContextDecl) {
278 // Compute the context for allocating mangling numbers in the current
279 // expression, if the ABI requires them.
280 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 (Var->getMostRecentDecl()->isInline())
304 Kind = InlineVariable;
305 else if (Var->getDescribedVarTemplate())
306 Kind = VariableTemplate;
307 else if (auto *VTS = dyn_cast<VarTemplateSpecializationDecl>(Var)) {
308 if (!VTS->isExplicitSpecialization())
309 Kind = VariableTemplate;
311 } else if (isa<FieldDecl>(ManglingContextDecl)) {
316 // Itanium ABI [5.1.7]:
317 // In the following contexts [...] the one-definition rule requires closure
318 // types in different translation units to "correspond":
319 bool IsInNonspecializedTemplate =
320 inTemplateInstantiation() || CurContext->isDependentContext();
323 // -- the bodies of non-exported nonspecialized template functions
324 // -- the bodies of inline functions
325 if ((IsInNonspecializedTemplate &&
326 !(ManglingContextDecl && isa<ParmVarDecl>(ManglingContextDecl))) ||
327 isInInlineFunction(CurContext)) {
328 ManglingContextDecl = nullptr;
329 while (auto *CD = dyn_cast<CapturedDecl>(DC))
330 DC = CD->getParent();
331 return &Context.getManglingNumberContext(DC);
334 ManglingContextDecl = nullptr;
338 case StaticDataMember:
339 // -- the initializers of nonspecialized static members of template classes
340 if (!IsInNonspecializedTemplate) {
341 ManglingContextDecl = nullptr;
344 // Fall through to get the current context.
348 // -- the in-class initializers of class members
349 case DefaultArgument:
350 // -- default arguments appearing in class definitions
352 // -- the initializers of inline variables
353 case VariableTemplate:
354 // -- the initializers of templated variables
355 return &ExprEvalContexts.back().getMangleNumberingContext(Context);
358 llvm_unreachable("unexpected context");
361 MangleNumberingContext &
362 Sema::ExpressionEvaluationContextRecord::getMangleNumberingContext(
364 assert(ManglingContextDecl && "Need to have a context declaration");
365 if (!MangleNumbering)
366 MangleNumbering = Ctx.createMangleNumberingContext();
367 return *MangleNumbering;
370 CXXMethodDecl *Sema::startLambdaDefinition(
371 CXXRecordDecl *Class, SourceRange IntroducerRange,
372 TypeSourceInfo *MethodTypeInfo, SourceLocation EndLoc,
373 ArrayRef<ParmVarDecl *> Params, ConstexprSpecKind ConstexprKind,
374 Optional<std::pair<unsigned, Decl *>> Mangling) {
375 QualType MethodType = MethodTypeInfo->getType();
376 TemplateParameterList *TemplateParams =
377 getGenericLambdaTemplateParameterList(getCurLambda(), *this);
378 // If a lambda appears in a dependent context or is a generic lambda (has
379 // template parameters) and has an 'auto' return type, deduce it to a
381 if (Class->isDependentContext() || TemplateParams) {
382 const FunctionProtoType *FPT = MethodType->castAs<FunctionProtoType>();
383 QualType Result = FPT->getReturnType();
384 if (Result->isUndeducedType()) {
385 Result = SubstAutoType(Result, Context.DependentTy);
386 MethodType = Context.getFunctionType(Result, FPT->getParamTypes(),
387 FPT->getExtProtoInfo());
391 // C++11 [expr.prim.lambda]p5:
392 // The closure type for a lambda-expression has a public inline function
393 // call operator (13.5.4) whose parameters and return type are described by
394 // the lambda-expression's parameter-declaration-clause and
395 // trailing-return-type respectively.
396 DeclarationName MethodName
397 = Context.DeclarationNames.getCXXOperatorName(OO_Call);
398 DeclarationNameLoc MethodNameLoc;
399 MethodNameLoc.CXXOperatorName.BeginOpNameLoc
400 = IntroducerRange.getBegin().getRawEncoding();
401 MethodNameLoc.CXXOperatorName.EndOpNameLoc
402 = IntroducerRange.getEnd().getRawEncoding();
403 CXXMethodDecl *Method = CXXMethodDecl::Create(
404 Context, Class, EndLoc,
405 DeclarationNameInfo(MethodName, IntroducerRange.getBegin(),
407 MethodType, MethodTypeInfo, SC_None,
408 /*isInline=*/true, ConstexprKind, EndLoc);
409 Method->setAccess(AS_public);
411 // Temporarily set the lexical declaration context to the current
412 // context, so that the Scope stack matches the lexical nesting.
413 Method->setLexicalDeclContext(CurContext);
414 // Create a function template if we have a template parameter list
415 FunctionTemplateDecl *const TemplateMethod = TemplateParams ?
416 FunctionTemplateDecl::Create(Context, Class,
417 Method->getLocation(), MethodName,
420 if (TemplateMethod) {
421 TemplateMethod->setLexicalDeclContext(CurContext);
422 TemplateMethod->setAccess(AS_public);
423 Method->setDescribedFunctionTemplate(TemplateMethod);
427 if (!Params.empty()) {
428 Method->setParams(Params);
429 CheckParmsForFunctionDef(Params,
430 /*CheckParameterNames=*/false);
432 for (auto P : Method->parameters())
433 P->setOwningFunction(Method);
437 Class->setLambdaMangling(Mangling->first, Mangling->second);
439 Decl *ManglingContextDecl;
440 if (MangleNumberingContext *MCtx =
441 getCurrentMangleNumberContext(Class->getDeclContext(),
442 ManglingContextDecl)) {
443 unsigned ManglingNumber = MCtx->getManglingNumber(Method);
444 Class->setLambdaMangling(ManglingNumber, ManglingContextDecl);
451 void Sema::buildLambdaScope(LambdaScopeInfo *LSI,
452 CXXMethodDecl *CallOperator,
453 SourceRange IntroducerRange,
454 LambdaCaptureDefault CaptureDefault,
455 SourceLocation CaptureDefaultLoc,
457 bool ExplicitResultType,
459 LSI->CallOperator = CallOperator;
460 CXXRecordDecl *LambdaClass = CallOperator->getParent();
461 LSI->Lambda = LambdaClass;
462 if (CaptureDefault == LCD_ByCopy)
463 LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByval;
464 else if (CaptureDefault == LCD_ByRef)
465 LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByref;
466 LSI->CaptureDefaultLoc = CaptureDefaultLoc;
467 LSI->IntroducerRange = IntroducerRange;
468 LSI->ExplicitParams = ExplicitParams;
469 LSI->Mutable = Mutable;
471 if (ExplicitResultType) {
472 LSI->ReturnType = CallOperator->getReturnType();
474 if (!LSI->ReturnType->isDependentType() &&
475 !LSI->ReturnType->isVoidType()) {
476 if (RequireCompleteType(CallOperator->getBeginLoc(), LSI->ReturnType,
477 diag::err_lambda_incomplete_result)) {
482 LSI->HasImplicitReturnType = true;
486 void Sema::finishLambdaExplicitCaptures(LambdaScopeInfo *LSI) {
487 LSI->finishedExplicitCaptures();
490 void Sema::ActOnLambdaExplicitTemplateParameterList(SourceLocation LAngleLoc,
491 ArrayRef<NamedDecl *> TParams,
492 SourceLocation RAngleLoc) {
493 LambdaScopeInfo *LSI = getCurLambda();
494 assert(LSI && "Expected a lambda scope");
495 assert(LSI->NumExplicitTemplateParams == 0 &&
496 "Already acted on explicit template parameters");
497 assert(LSI->TemplateParams.empty() &&
498 "Explicit template parameters should come "
499 "before invented (auto) ones");
500 assert(!TParams.empty() &&
501 "No template parameters to act on");
502 LSI->TemplateParams.append(TParams.begin(), TParams.end());
503 LSI->NumExplicitTemplateParams = TParams.size();
504 LSI->ExplicitTemplateParamsRange = {LAngleLoc, RAngleLoc};
507 void Sema::addLambdaParameters(
508 ArrayRef<LambdaIntroducer::LambdaCapture> Captures,
509 CXXMethodDecl *CallOperator, Scope *CurScope) {
510 // Introduce our parameters into the function scope
511 for (unsigned p = 0, NumParams = CallOperator->getNumParams();
512 p < NumParams; ++p) {
513 ParmVarDecl *Param = CallOperator->getParamDecl(p);
515 // If this has an identifier, add it to the scope stack.
516 if (CurScope && Param->getIdentifier()) {
518 // Resolution of CWG 2211 in C++17 renders shadowing ill-formed, but we
519 // retroactively apply it.
520 for (const auto &Capture : Captures) {
521 if (Capture.Id == Param->getIdentifier()) {
523 Diag(Param->getLocation(), diag::err_parameter_shadow_capture);
524 Diag(Capture.Loc, diag::note_var_explicitly_captured_here)
525 << Capture.Id << true;
529 CheckShadow(CurScope, Param);
531 PushOnScopeChains(Param, CurScope);
536 /// If this expression is an enumerator-like expression of some type
537 /// T, return the type T; otherwise, return null.
539 /// Pointer comparisons on the result here should always work because
540 /// it's derived from either the parent of an EnumConstantDecl
541 /// (i.e. the definition) or the declaration returned by
542 /// EnumType::getDecl() (i.e. the definition).
543 static EnumDecl *findEnumForBlockReturn(Expr *E) {
544 // An expression is an enumerator-like expression of type T if,
545 // ignoring parens and parens-like expressions:
546 E = E->IgnoreParens();
548 // - it is an enumerator whose enum type is T or
549 if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
550 if (EnumConstantDecl *D
551 = dyn_cast<EnumConstantDecl>(DRE->getDecl())) {
552 return cast<EnumDecl>(D->getDeclContext());
557 // - it is a comma expression whose RHS is an enumerator-like
558 // expression of type T or
559 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
560 if (BO->getOpcode() == BO_Comma)
561 return findEnumForBlockReturn(BO->getRHS());
565 // - it is a statement-expression whose value expression is an
566 // enumerator-like expression of type T or
567 if (StmtExpr *SE = dyn_cast<StmtExpr>(E)) {
568 if (Expr *last = dyn_cast_or_null<Expr>(SE->getSubStmt()->body_back()))
569 return findEnumForBlockReturn(last);
573 // - it is a ternary conditional operator (not the GNU ?:
574 // extension) whose second and third operands are
575 // enumerator-like expressions of type T or
576 if (ConditionalOperator *CO = dyn_cast<ConditionalOperator>(E)) {
577 if (EnumDecl *ED = findEnumForBlockReturn(CO->getTrueExpr()))
578 if (ED == findEnumForBlockReturn(CO->getFalseExpr()))
584 // - it is an implicit integral conversion applied to an
585 // enumerator-like expression of type T or
586 if (ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(E)) {
587 // We can sometimes see integral conversions in valid
588 // enumerator-like expressions.
589 if (ICE->getCastKind() == CK_IntegralCast)
590 return findEnumForBlockReturn(ICE->getSubExpr());
592 // Otherwise, just rely on the type.
595 // - it is an expression of that formal enum type.
596 if (const EnumType *ET = E->getType()->getAs<EnumType>()) {
597 return ET->getDecl();
604 /// Attempt to find a type T for which the returned expression of the
605 /// given statement is an enumerator-like expression of that type.
606 static EnumDecl *findEnumForBlockReturn(ReturnStmt *ret) {
607 if (Expr *retValue = ret->getRetValue())
608 return findEnumForBlockReturn(retValue);
612 /// Attempt to find a common type T for which all of the returned
613 /// expressions in a block are enumerator-like expressions of that
615 static EnumDecl *findCommonEnumForBlockReturns(ArrayRef<ReturnStmt*> returns) {
616 ArrayRef<ReturnStmt*>::iterator i = returns.begin(), e = returns.end();
618 // Try to find one for the first return.
619 EnumDecl *ED = findEnumForBlockReturn(*i);
620 if (!ED) return nullptr;
622 // Check that the rest of the returns have the same enum.
623 for (++i; i != e; ++i) {
624 if (findEnumForBlockReturn(*i) != ED)
628 // Never infer an anonymous enum type.
629 if (!ED->hasNameForLinkage()) return nullptr;
634 /// Adjust the given return statements so that they formally return
635 /// the given type. It should require, at most, an IntegralCast.
636 static void adjustBlockReturnsToEnum(Sema &S, ArrayRef<ReturnStmt*> returns,
637 QualType returnType) {
638 for (ArrayRef<ReturnStmt*>::iterator
639 i = returns.begin(), e = returns.end(); i != e; ++i) {
640 ReturnStmt *ret = *i;
641 Expr *retValue = ret->getRetValue();
642 if (S.Context.hasSameType(retValue->getType(), returnType))
645 // Right now we only support integral fixup casts.
646 assert(returnType->isIntegralOrUnscopedEnumerationType());
647 assert(retValue->getType()->isIntegralOrUnscopedEnumerationType());
649 ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(retValue);
651 Expr *E = (cleanups ? cleanups->getSubExpr() : retValue);
652 E = ImplicitCastExpr::Create(S.Context, returnType, CK_IntegralCast,
653 E, /*base path*/ nullptr, VK_RValue);
655 cleanups->setSubExpr(E);
662 void Sema::deduceClosureReturnType(CapturingScopeInfo &CSI) {
663 assert(CSI.HasImplicitReturnType);
664 // If it was ever a placeholder, it had to been deduced to DependentTy.
665 assert(CSI.ReturnType.isNull() || !CSI.ReturnType->isUndeducedType());
666 assert((!isa<LambdaScopeInfo>(CSI) || !getLangOpts().CPlusPlus14) &&
667 "lambda expressions use auto deduction in C++14 onwards");
669 // C++ core issue 975:
670 // If a lambda-expression does not include a trailing-return-type,
671 // it is as if the trailing-return-type denotes the following type:
672 // - if there are no return statements in the compound-statement,
673 // or all return statements return either an expression of type
674 // void or no expression or braced-init-list, the type void;
675 // - otherwise, if all return statements return an expression
676 // and the types of the returned expressions after
677 // lvalue-to-rvalue conversion (4.1 [conv.lval]),
678 // array-to-pointer conversion (4.2 [conv.array]), and
679 // function-to-pointer conversion (4.3 [conv.func]) are the
680 // same, that common type;
681 // - otherwise, the program is ill-formed.
683 // C++ core issue 1048 additionally removes top-level cv-qualifiers
684 // from the types of returned expressions to match the C++14 auto
687 // In addition, in blocks in non-C++ modes, if all of the return
688 // statements are enumerator-like expressions of some type T, where
689 // T has a name for linkage, then we infer the return type of the
690 // block to be that type.
692 // First case: no return statements, implicit void return type.
693 ASTContext &Ctx = getASTContext();
694 if (CSI.Returns.empty()) {
695 // It's possible there were simply no /valid/ return statements.
696 // In this case, the first one we found may have at least given us a type.
697 if (CSI.ReturnType.isNull())
698 CSI.ReturnType = Ctx.VoidTy;
702 // Second case: at least one return statement has dependent type.
703 // Delay type checking until instantiation.
704 assert(!CSI.ReturnType.isNull() && "We should have a tentative return type.");
705 if (CSI.ReturnType->isDependentType())
708 // Try to apply the enum-fuzz rule.
709 if (!getLangOpts().CPlusPlus) {
710 assert(isa<BlockScopeInfo>(CSI));
711 const EnumDecl *ED = findCommonEnumForBlockReturns(CSI.Returns);
713 CSI.ReturnType = Context.getTypeDeclType(ED);
714 adjustBlockReturnsToEnum(*this, CSI.Returns, CSI.ReturnType);
719 // Third case: only one return statement. Don't bother doing extra work!
720 if (CSI.Returns.size() == 1)
723 // General case: many return statements.
724 // Check that they all have compatible return types.
726 // We require the return types to strictly match here.
727 // Note that we've already done the required promotions as part of
728 // processing the return statement.
729 for (const ReturnStmt *RS : CSI.Returns) {
730 const Expr *RetE = RS->getRetValue();
732 QualType ReturnType =
733 (RetE ? RetE->getType() : Context.VoidTy).getUnqualifiedType();
734 if (Context.getCanonicalFunctionResultType(ReturnType) ==
735 Context.getCanonicalFunctionResultType(CSI.ReturnType)) {
736 // Use the return type with the strictest possible nullability annotation.
737 auto RetTyNullability = ReturnType->getNullability(Ctx);
738 auto BlockNullability = CSI.ReturnType->getNullability(Ctx);
739 if (BlockNullability &&
740 (!RetTyNullability ||
741 hasWeakerNullability(*RetTyNullability, *BlockNullability)))
742 CSI.ReturnType = ReturnType;
746 // FIXME: This is a poor diagnostic for ReturnStmts without expressions.
747 // TODO: It's possible that the *first* return is the divergent one.
748 Diag(RS->getBeginLoc(),
749 diag::err_typecheck_missing_return_type_incompatible)
750 << ReturnType << CSI.ReturnType << isa<LambdaScopeInfo>(CSI);
751 // Continue iterating so that we keep emitting diagnostics.
755 QualType Sema::buildLambdaInitCaptureInitialization(
756 SourceLocation Loc, bool ByRef, SourceLocation EllipsisLoc,
757 Optional<unsigned> NumExpansions, IdentifierInfo *Id, bool IsDirectInit,
759 // Create an 'auto' or 'auto&' TypeSourceInfo that we can use to
761 QualType DeductType = Context.getAutoDeductType();
763 TLB.pushTypeSpec(DeductType).setNameLoc(Loc);
765 DeductType = BuildReferenceType(DeductType, true, Loc, Id);
766 assert(!DeductType.isNull() && "can't build reference to auto");
767 TLB.push<ReferenceTypeLoc>(DeductType).setSigilLoc(Loc);
769 if (EllipsisLoc.isValid()) {
770 if (Init->containsUnexpandedParameterPack()) {
771 Diag(EllipsisLoc, getLangOpts().CPlusPlus2a
772 ? diag::warn_cxx17_compat_init_capture_pack
773 : diag::ext_init_capture_pack);
774 DeductType = Context.getPackExpansionType(DeductType, NumExpansions);
775 TLB.push<PackExpansionTypeLoc>(DeductType).setEllipsisLoc(EllipsisLoc);
777 // Just ignore the ellipsis for now and form a non-pack variable. We'll
778 // diagnose this later when we try to capture it.
781 TypeSourceInfo *TSI = TLB.getTypeSourceInfo(Context, DeductType);
783 // Deduce the type of the init capture.
784 QualType DeducedType = deduceVarTypeFromInitializer(
785 /*VarDecl*/nullptr, DeclarationName(Id), DeductType, TSI,
786 SourceRange(Loc, Loc), IsDirectInit, Init);
787 if (DeducedType.isNull())
790 // Are we a non-list direct initialization?
791 ParenListExpr *CXXDirectInit = dyn_cast<ParenListExpr>(Init);
793 // Perform initialization analysis and ensure any implicit conversions
794 // (such as lvalue-to-rvalue) are enforced.
795 InitializedEntity Entity =
796 InitializedEntity::InitializeLambdaCapture(Id, DeducedType, Loc);
797 InitializationKind Kind =
799 ? (CXXDirectInit ? InitializationKind::CreateDirect(
800 Loc, Init->getBeginLoc(), Init->getEndLoc())
801 : InitializationKind::CreateDirectList(Loc))
802 : InitializationKind::CreateCopy(Loc, Init->getBeginLoc());
804 MultiExprArg Args = Init;
807 MultiExprArg(CXXDirectInit->getExprs(), CXXDirectInit->getNumExprs());
809 InitializationSequence InitSeq(*this, Entity, Kind, Args);
810 ExprResult Result = InitSeq.Perform(*this, Entity, Kind, Args, &DclT);
812 if (Result.isInvalid())
815 Init = Result.getAs<Expr>();
819 VarDecl *Sema::createLambdaInitCaptureVarDecl(SourceLocation Loc,
820 QualType InitCaptureType,
821 SourceLocation EllipsisLoc,
823 unsigned InitStyle, Expr *Init) {
824 // FIXME: Retain the TypeSourceInfo from buildLambdaInitCaptureInitialization
825 // rather than reconstructing it here.
826 TypeSourceInfo *TSI = Context.getTrivialTypeSourceInfo(InitCaptureType, Loc);
827 if (auto PETL = TSI->getTypeLoc().getAs<PackExpansionTypeLoc>())
828 PETL.setEllipsisLoc(EllipsisLoc);
830 // Create a dummy variable representing the init-capture. This is not actually
831 // used as a variable, and only exists as a way to name and refer to the
833 // FIXME: Pass in separate source locations for '&' and identifier.
834 VarDecl *NewVD = VarDecl::Create(Context, CurContext, Loc,
835 Loc, Id, InitCaptureType, TSI, SC_Auto);
836 NewVD->setInitCapture(true);
837 NewVD->setReferenced(true);
838 // FIXME: Pass in a VarDecl::InitializationStyle.
839 NewVD->setInitStyle(static_cast<VarDecl::InitializationStyle>(InitStyle));
840 NewVD->markUsed(Context);
841 NewVD->setInit(Init);
845 void Sema::addInitCapture(LambdaScopeInfo *LSI, VarDecl *Var) {
846 assert(Var->isInitCapture() && "init capture flag should be set");
847 LSI->addCapture(Var, /*isBlock*/false, Var->getType()->isReferenceType(),
848 /*isNested*/false, Var->getLocation(), SourceLocation(),
849 Var->getType(), /*Invalid*/false);
852 void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
853 Declarator &ParamInfo,
855 LambdaScopeInfo *const LSI = getCurLambda();
856 assert(LSI && "LambdaScopeInfo should be on stack!");
858 // Determine if we're within a context where we know that the lambda will
859 // be dependent, because there are template parameters in scope.
861 if (LSI->NumExplicitTemplateParams > 0) {
862 auto *TemplateParamScope = CurScope->getTemplateParamParent();
863 assert(TemplateParamScope &&
864 "Lambda with explicit template param list should establish a "
865 "template param scope");
866 assert(TemplateParamScope->getParent());
867 KnownDependent = TemplateParamScope->getParent()
868 ->getTemplateParamParent() != nullptr;
870 KnownDependent = CurScope->getTemplateParamParent() != nullptr;
873 // Determine the signature of the call operator.
874 TypeSourceInfo *MethodTyInfo;
875 bool ExplicitParams = true;
876 bool ExplicitResultType = true;
877 bool ContainsUnexpandedParameterPack = false;
878 SourceLocation EndLoc;
879 SmallVector<ParmVarDecl *, 8> Params;
880 if (ParamInfo.getNumTypeObjects() == 0) {
881 // C++11 [expr.prim.lambda]p4:
882 // If a lambda-expression does not include a lambda-declarator, it is as
883 // if the lambda-declarator were ().
884 FunctionProtoType::ExtProtoInfo EPI(Context.getDefaultCallingConvention(
885 /*IsVariadic=*/false, /*IsCXXMethod=*/true));
886 EPI.HasTrailingReturn = true;
887 EPI.TypeQuals.addConst();
888 // C++1y [expr.prim.lambda]:
889 // The lambda return type is 'auto', which is replaced by the
890 // trailing-return type if provided and/or deduced from 'return'
892 // We don't do this before C++1y, because we don't support deduced return
894 QualType DefaultTypeForNoTrailingReturn =
895 getLangOpts().CPlusPlus14 ? Context.getAutoDeductType()
896 : Context.DependentTy;
898 Context.getFunctionType(DefaultTypeForNoTrailingReturn, None, EPI);
899 MethodTyInfo = Context.getTrivialTypeSourceInfo(MethodTy);
900 ExplicitParams = false;
901 ExplicitResultType = false;
902 EndLoc = Intro.Range.getEnd();
904 assert(ParamInfo.isFunctionDeclarator() &&
905 "lambda-declarator is a function");
906 DeclaratorChunk::FunctionTypeInfo &FTI = ParamInfo.getFunctionTypeInfo();
908 // C++11 [expr.prim.lambda]p5:
909 // This function call operator is declared const (9.3.1) if and only if
910 // the lambda-expression's parameter-declaration-clause is not followed
911 // by mutable. It is neither virtual nor declared volatile. [...]
912 if (!FTI.hasMutableQualifier()) {
913 FTI.getOrCreateMethodQualifiers().SetTypeQual(DeclSpec::TQ_const,
917 MethodTyInfo = GetTypeForDeclarator(ParamInfo, CurScope);
918 assert(MethodTyInfo && "no type from lambda-declarator");
919 EndLoc = ParamInfo.getSourceRange().getEnd();
921 ExplicitResultType = FTI.hasTrailingReturnType();
923 if (FTIHasNonVoidParameters(FTI)) {
924 Params.reserve(FTI.NumParams);
925 for (unsigned i = 0, e = FTI.NumParams; i != e; ++i)
926 Params.push_back(cast<ParmVarDecl>(FTI.Params[i].Param));
929 // Check for unexpanded parameter packs in the method type.
930 if (MethodTyInfo->getType()->containsUnexpandedParameterPack())
931 ContainsUnexpandedParameterPack = true;
934 CXXRecordDecl *Class = createLambdaClosureType(Intro.Range, MethodTyInfo,
935 KnownDependent, Intro.Default);
937 CXXMethodDecl *Method =
938 startLambdaDefinition(Class, Intro.Range, MethodTyInfo, EndLoc, Params,
939 ParamInfo.getDeclSpec().getConstexprSpecifier());
941 CheckCXXDefaultArguments(Method);
943 // This represents the function body for the lambda function, check if we
944 // have to apply optnone due to a pragma.
945 AddRangeBasedOptnone(Method);
947 // code_seg attribute on lambda apply to the method.
948 if (Attr *A = getImplicitCodeSegOrSectionAttrForFunction(Method, /*IsDefinition=*/true))
951 // Attributes on the lambda apply to the method.
952 ProcessDeclAttributes(CurScope, Method, ParamInfo);
954 // CUDA lambdas get implicit attributes based on the scope in which they're
956 if (getLangOpts().CUDA)
957 CUDASetLambdaAttrs(Method);
959 // Introduce the function call operator as the current declaration context.
960 PushDeclContext(CurScope, Method);
962 // Build the lambda scope.
963 buildLambdaScope(LSI, Method, Intro.Range, Intro.Default, Intro.DefaultLoc,
964 ExplicitParams, ExplicitResultType, !Method->isConst());
966 // C++11 [expr.prim.lambda]p9:
967 // A lambda-expression whose smallest enclosing scope is a block scope is a
968 // local lambda expression; any other lambda expression shall not have a
969 // capture-default or simple-capture in its lambda-introducer.
971 // For simple-captures, this is covered by the check below that any named
972 // entity is a variable that can be captured.
974 // For DR1632, we also allow a capture-default in any context where we can
975 // odr-use 'this' (in particular, in a default initializer for a non-static
977 if (Intro.Default != LCD_None && !Class->getParent()->isFunctionOrMethod() &&
978 (getCurrentThisType().isNull() ||
979 CheckCXXThisCapture(SourceLocation(), /*Explicit*/true,
980 /*BuildAndDiagnose*/false)))
981 Diag(Intro.DefaultLoc, diag::err_capture_default_non_local);
983 // Distinct capture names, for diagnostics.
984 llvm::SmallSet<IdentifierInfo*, 8> CaptureNames;
986 // Handle explicit captures.
987 SourceLocation PrevCaptureLoc
988 = Intro.Default == LCD_None? Intro.Range.getBegin() : Intro.DefaultLoc;
989 for (auto C = Intro.Captures.begin(), E = Intro.Captures.end(); C != E;
990 PrevCaptureLoc = C->Loc, ++C) {
991 if (C->Kind == LCK_This || C->Kind == LCK_StarThis) {
992 if (C->Kind == LCK_StarThis)
993 Diag(C->Loc, !getLangOpts().CPlusPlus17
994 ? diag::ext_star_this_lambda_capture_cxx17
995 : diag::warn_cxx14_compat_star_this_lambda_capture);
997 // C++11 [expr.prim.lambda]p8:
998 // An identifier or this shall not appear more than once in a
1000 if (LSI->isCXXThisCaptured()) {
1001 Diag(C->Loc, diag::err_capture_more_than_once)
1002 << "'this'" << SourceRange(LSI->getCXXThisCapture().getLocation())
1003 << FixItHint::CreateRemoval(
1004 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1008 // C++2a [expr.prim.lambda]p8:
1009 // If a lambda-capture includes a capture-default that is =,
1010 // each simple-capture of that lambda-capture shall be of the form
1011 // "&identifier", "this", or "* this". [ Note: The form [&,this] is
1012 // redundant but accepted for compatibility with ISO C++14. --end note ]
1013 if (Intro.Default == LCD_ByCopy && C->Kind != LCK_StarThis)
1014 Diag(C->Loc, !getLangOpts().CPlusPlus2a
1015 ? diag::ext_equals_this_lambda_capture_cxx2a
1016 : diag::warn_cxx17_compat_equals_this_lambda_capture);
1018 // C++11 [expr.prim.lambda]p12:
1019 // If this is captured by a local lambda expression, its nearest
1020 // enclosing function shall be a non-static member function.
1021 QualType ThisCaptureType = getCurrentThisType();
1022 if (ThisCaptureType.isNull()) {
1023 Diag(C->Loc, diag::err_this_capture) << true;
1027 CheckCXXThisCapture(C->Loc, /*Explicit=*/true, /*BuildAndDiagnose*/ true,
1028 /*FunctionScopeIndexToStopAtPtr*/ nullptr,
1029 C->Kind == LCK_StarThis);
1030 if (!LSI->Captures.empty())
1031 LSI->ExplicitCaptureRanges[LSI->Captures.size() - 1] = C->ExplicitRange;
1035 assert(C->Id && "missing identifier for capture");
1037 if (C->Init.isInvalid())
1040 VarDecl *Var = nullptr;
1041 if (C->Init.isUsable()) {
1042 Diag(C->Loc, getLangOpts().CPlusPlus14
1043 ? diag::warn_cxx11_compat_init_capture
1044 : diag::ext_init_capture);
1046 // If the initializer expression is usable, but the InitCaptureType
1047 // is not, then an error has occurred - so ignore the capture for now.
1048 // for e.g., [n{0}] { }; <-- if no <initializer_list> is included.
1049 // FIXME: we should create the init capture variable and mark it invalid
1051 if (C->InitCaptureType.get().isNull())
1054 if (C->Init.get()->containsUnexpandedParameterPack() &&
1055 !C->InitCaptureType.get()->getAs<PackExpansionType>())
1056 ContainsUnexpandedParameterPack = true;
1059 switch (C->InitKind) {
1060 case LambdaCaptureInitKind::NoInit:
1061 llvm_unreachable("not an init-capture?");
1062 case LambdaCaptureInitKind::CopyInit:
1063 InitStyle = VarDecl::CInit;
1065 case LambdaCaptureInitKind::DirectInit:
1066 InitStyle = VarDecl::CallInit;
1068 case LambdaCaptureInitKind::ListInit:
1069 InitStyle = VarDecl::ListInit;
1072 Var = createLambdaInitCaptureVarDecl(C->Loc, C->InitCaptureType.get(),
1073 C->EllipsisLoc, C->Id, InitStyle,
1075 // C++1y [expr.prim.lambda]p11:
1076 // An init-capture behaves as if it declares and explicitly
1077 // captures a variable [...] whose declarative region is the
1078 // lambda-expression's compound-statement
1080 PushOnScopeChains(Var, CurScope, false);
1082 assert(C->InitKind == LambdaCaptureInitKind::NoInit &&
1083 "init capture has valid but null init?");
1085 // C++11 [expr.prim.lambda]p8:
1086 // If a lambda-capture includes a capture-default that is &, the
1087 // identifiers in the lambda-capture shall not be preceded by &.
1088 // If a lambda-capture includes a capture-default that is =, [...]
1089 // each identifier it contains shall be preceded by &.
1090 if (C->Kind == LCK_ByRef && Intro.Default == LCD_ByRef) {
1091 Diag(C->Loc, diag::err_reference_capture_with_reference_default)
1092 << FixItHint::CreateRemoval(
1093 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1095 } else if (C->Kind == LCK_ByCopy && Intro.Default == LCD_ByCopy) {
1096 Diag(C->Loc, diag::err_copy_capture_with_copy_default)
1097 << FixItHint::CreateRemoval(
1098 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1102 // C++11 [expr.prim.lambda]p10:
1103 // The identifiers in a capture-list are looked up using the usual
1104 // rules for unqualified name lookup (3.4.1)
1105 DeclarationNameInfo Name(C->Id, C->Loc);
1106 LookupResult R(*this, Name, LookupOrdinaryName);
1107 LookupName(R, CurScope);
1108 if (R.isAmbiguous())
1111 // FIXME: Disable corrections that would add qualification?
1112 CXXScopeSpec ScopeSpec;
1113 DeclFilterCCC<VarDecl> Validator{};
1114 if (DiagnoseEmptyLookup(CurScope, ScopeSpec, R, Validator))
1118 Var = R.getAsSingle<VarDecl>();
1119 if (Var && DiagnoseUseOfDecl(Var, C->Loc))
1123 // C++11 [expr.prim.lambda]p8:
1124 // An identifier or this shall not appear more than once in a
1126 if (!CaptureNames.insert(C->Id).second) {
1127 if (Var && LSI->isCaptured(Var)) {
1128 Diag(C->Loc, diag::err_capture_more_than_once)
1129 << C->Id << SourceRange(LSI->getCapture(Var).getLocation())
1130 << FixItHint::CreateRemoval(
1131 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1133 // Previous capture captured something different (one or both was
1134 // an init-cpature): no fixit.
1135 Diag(C->Loc, diag::err_capture_more_than_once) << C->Id;
1139 // C++11 [expr.prim.lambda]p10:
1140 // [...] each such lookup shall find a variable with automatic storage
1141 // duration declared in the reaching scope of the local lambda expression.
1142 // Note that the 'reaching scope' check happens in tryCaptureVariable().
1144 Diag(C->Loc, diag::err_capture_does_not_name_variable) << C->Id;
1148 // Ignore invalid decls; they'll just confuse the code later.
1149 if (Var->isInvalidDecl())
1152 if (!Var->hasLocalStorage()) {
1153 Diag(C->Loc, diag::err_capture_non_automatic_variable) << C->Id;
1154 Diag(Var->getLocation(), diag::note_previous_decl) << C->Id;
1158 // C++11 [expr.prim.lambda]p23:
1159 // A capture followed by an ellipsis is a pack expansion (14.5.3).
1160 SourceLocation EllipsisLoc;
1161 if (C->EllipsisLoc.isValid()) {
1162 if (Var->isParameterPack()) {
1163 EllipsisLoc = C->EllipsisLoc;
1165 Diag(C->EllipsisLoc, diag::err_pack_expansion_without_parameter_packs)
1166 << (C->Init.isUsable() ? C->Init.get()->getSourceRange()
1167 : SourceRange(C->Loc));
1169 // Just ignore the ellipsis.
1171 } else if (Var->isParameterPack()) {
1172 ContainsUnexpandedParameterPack = true;
1175 if (C->Init.isUsable()) {
1176 addInitCapture(LSI, Var);
1178 TryCaptureKind Kind = C->Kind == LCK_ByRef ? TryCapture_ExplicitByRef :
1179 TryCapture_ExplicitByVal;
1180 tryCaptureVariable(Var, C->Loc, Kind, EllipsisLoc);
1182 if (!LSI->Captures.empty())
1183 LSI->ExplicitCaptureRanges[LSI->Captures.size() - 1] = C->ExplicitRange;
1185 finishLambdaExplicitCaptures(LSI);
1187 LSI->ContainsUnexpandedParameterPack = ContainsUnexpandedParameterPack;
1189 // Add lambda parameters into scope.
1190 addLambdaParameters(Intro.Captures, Method, CurScope);
1192 // Enter a new evaluation context to insulate the lambda from any
1193 // cleanups from the enclosing full-expression.
1194 PushExpressionEvaluationContext(
1195 ExpressionEvaluationContext::PotentiallyEvaluated);
1198 void Sema::ActOnLambdaError(SourceLocation StartLoc, Scope *CurScope,
1199 bool IsInstantiation) {
1200 LambdaScopeInfo *LSI = cast<LambdaScopeInfo>(FunctionScopes.back());
1202 // Leave the expression-evaluation context.
1203 DiscardCleanupsInEvaluationContext();
1204 PopExpressionEvaluationContext();
1206 // Leave the context of the lambda.
1207 if (!IsInstantiation)
1210 // Finalize the lambda.
1211 CXXRecordDecl *Class = LSI->Lambda;
1212 Class->setInvalidDecl();
1213 SmallVector<Decl*, 4> Fields(Class->fields());
1214 ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
1215 SourceLocation(), ParsedAttributesView());
1216 CheckCompletedCXXClass(Class);
1218 PopFunctionScopeInfo();
1221 QualType Sema::getLambdaConversionFunctionResultType(
1222 const FunctionProtoType *CallOpProto) {
1223 // The function type inside the pointer type is the same as the call
1224 // operator with some tweaks. The calling convention is the default free
1225 // function convention, and the type qualifications are lost.
1226 const FunctionProtoType::ExtProtoInfo CallOpExtInfo =
1227 CallOpProto->getExtProtoInfo();
1228 FunctionProtoType::ExtProtoInfo InvokerExtInfo = CallOpExtInfo;
1229 CallingConv CC = Context.getDefaultCallingConvention(
1230 CallOpProto->isVariadic(), /*IsCXXMethod=*/false);
1231 InvokerExtInfo.ExtInfo = InvokerExtInfo.ExtInfo.withCallingConv(CC);
1232 InvokerExtInfo.TypeQuals = Qualifiers();
1233 assert(InvokerExtInfo.RefQualifier == RQ_None &&
1234 "Lambda's call operator should not have a reference qualifier");
1235 return Context.getFunctionType(CallOpProto->getReturnType(),
1236 CallOpProto->getParamTypes(), InvokerExtInfo);
1239 /// Add a lambda's conversion to function pointer, as described in
1240 /// C++11 [expr.prim.lambda]p6.
1241 static void addFunctionPointerConversion(Sema &S,
1242 SourceRange IntroducerRange,
1243 CXXRecordDecl *Class,
1244 CXXMethodDecl *CallOperator) {
1245 // This conversion is explicitly disabled if the lambda's function has
1246 // pass_object_size attributes on any of its parameters.
1247 auto HasPassObjectSizeAttr = [](const ParmVarDecl *P) {
1248 return P->hasAttr<PassObjectSizeAttr>();
1250 if (llvm::any_of(CallOperator->parameters(), HasPassObjectSizeAttr))
1253 // Add the conversion to function pointer.
1254 QualType InvokerFunctionTy = S.getLambdaConversionFunctionResultType(
1255 CallOperator->getType()->castAs<FunctionProtoType>());
1256 QualType PtrToFunctionTy = S.Context.getPointerType(InvokerFunctionTy);
1258 // Create the type of the conversion function.
1259 FunctionProtoType::ExtProtoInfo ConvExtInfo(
1260 S.Context.getDefaultCallingConvention(
1261 /*IsVariadic=*/false, /*IsCXXMethod=*/true));
1262 // The conversion function is always const and noexcept.
1263 ConvExtInfo.TypeQuals = Qualifiers();
1264 ConvExtInfo.TypeQuals.addConst();
1265 ConvExtInfo.ExceptionSpec.Type = EST_BasicNoexcept;
1267 S.Context.getFunctionType(PtrToFunctionTy, None, ConvExtInfo);
1269 SourceLocation Loc = IntroducerRange.getBegin();
1270 DeclarationName ConversionName
1271 = S.Context.DeclarationNames.getCXXConversionFunctionName(
1272 S.Context.getCanonicalType(PtrToFunctionTy));
1273 DeclarationNameLoc ConvNameLoc;
1274 // Construct a TypeSourceInfo for the conversion function, and wire
1275 // all the parameters appropriately for the FunctionProtoTypeLoc
1276 // so that everything works during transformation/instantiation of
1278 // The main reason for wiring up the parameters of the conversion
1279 // function with that of the call operator is so that constructs
1280 // like the following work:
1281 // auto L = [](auto b) { <-- 1
1282 // return [](auto a) -> decltype(a) { <-- 2
1286 // int (*fp)(int) = L(5);
1287 // Because the trailing return type can contain DeclRefExprs that refer
1288 // to the original call operator's variables, we hijack the call
1289 // operators ParmVarDecls below.
1290 TypeSourceInfo *ConvNamePtrToFunctionTSI =
1291 S.Context.getTrivialTypeSourceInfo(PtrToFunctionTy, Loc);
1292 ConvNameLoc.NamedType.TInfo = ConvNamePtrToFunctionTSI;
1294 // The conversion function is a conversion to a pointer-to-function.
1295 TypeSourceInfo *ConvTSI = S.Context.getTrivialTypeSourceInfo(ConvTy, Loc);
1296 FunctionProtoTypeLoc ConvTL =
1297 ConvTSI->getTypeLoc().getAs<FunctionProtoTypeLoc>();
1298 // Get the result of the conversion function which is a pointer-to-function.
1299 PointerTypeLoc PtrToFunctionTL =
1300 ConvTL.getReturnLoc().getAs<PointerTypeLoc>();
1301 // Do the same for the TypeSourceInfo that is used to name the conversion
1303 PointerTypeLoc ConvNamePtrToFunctionTL =
1304 ConvNamePtrToFunctionTSI->getTypeLoc().getAs<PointerTypeLoc>();
1306 // Get the underlying function types that the conversion function will
1307 // be converting to (should match the type of the call operator).
1308 FunctionProtoTypeLoc CallOpConvTL =
1309 PtrToFunctionTL.getPointeeLoc().getAs<FunctionProtoTypeLoc>();
1310 FunctionProtoTypeLoc CallOpConvNameTL =
1311 ConvNamePtrToFunctionTL.getPointeeLoc().getAs<FunctionProtoTypeLoc>();
1313 // Wire up the FunctionProtoTypeLocs with the call operator's parameters.
1314 // These parameter's are essentially used to transform the name and
1315 // the type of the conversion operator. By using the same parameters
1316 // as the call operator's we don't have to fix any back references that
1317 // the trailing return type of the call operator's uses (such as
1318 // decltype(some_type<decltype(a)>::type{} + decltype(a){}) etc.)
1319 // - we can simply use the return type of the call operator, and
1320 // everything should work.
1321 SmallVector<ParmVarDecl *, 4> InvokerParams;
1322 for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I) {
1323 ParmVarDecl *From = CallOperator->getParamDecl(I);
1325 InvokerParams.push_back(ParmVarDecl::Create(
1327 // Temporarily add to the TU. This is set to the invoker below.
1328 S.Context.getTranslationUnitDecl(), From->getBeginLoc(),
1329 From->getLocation(), From->getIdentifier(), From->getType(),
1330 From->getTypeSourceInfo(), From->getStorageClass(),
1331 /*DefArg=*/nullptr));
1332 CallOpConvTL.setParam(I, From);
1333 CallOpConvNameTL.setParam(I, From);
1336 CXXConversionDecl *Conversion = CXXConversionDecl::Create(
1337 S.Context, Class, Loc,
1338 DeclarationNameInfo(ConversionName, Loc, ConvNameLoc), ConvTy, ConvTSI,
1339 /*isInline=*/true, ExplicitSpecifier(),
1340 S.getLangOpts().CPlusPlus17 ? CSK_constexpr : CSK_unspecified,
1341 CallOperator->getBody()->getEndLoc());
1342 Conversion->setAccess(AS_public);
1343 Conversion->setImplicit(true);
1345 if (Class->isGenericLambda()) {
1346 // Create a template version of the conversion operator, using the template
1347 // parameter list of the function call operator.
1348 FunctionTemplateDecl *TemplateCallOperator =
1349 CallOperator->getDescribedFunctionTemplate();
1350 FunctionTemplateDecl *ConversionTemplate =
1351 FunctionTemplateDecl::Create(S.Context, Class,
1352 Loc, ConversionName,
1353 TemplateCallOperator->getTemplateParameters(),
1355 ConversionTemplate->setAccess(AS_public);
1356 ConversionTemplate->setImplicit(true);
1357 Conversion->setDescribedFunctionTemplate(ConversionTemplate);
1358 Class->addDecl(ConversionTemplate);
1360 Class->addDecl(Conversion);
1361 // Add a non-static member function that will be the result of
1362 // the conversion with a certain unique ID.
1363 DeclarationName InvokerName = &S.Context.Idents.get(
1364 getLambdaStaticInvokerName());
1365 // FIXME: Instead of passing in the CallOperator->getTypeSourceInfo()
1366 // we should get a prebuilt TrivialTypeSourceInfo from Context
1367 // using FunctionTy & Loc and get its TypeLoc as a FunctionProtoTypeLoc
1368 // then rewire the parameters accordingly, by hoisting up the InvokeParams
1369 // loop below and then use its Params to set Invoke->setParams(...) below.
1370 // This would avoid the 'const' qualifier of the calloperator from
1371 // contaminating the type of the invoker, which is currently adjusted
1372 // in SemaTemplateDeduction.cpp:DeduceTemplateArguments. Fixing the
1373 // trailing return type of the invoker would require a visitor to rebuild
1374 // the trailing return type and adjusting all back DeclRefExpr's to refer
1375 // to the new static invoker parameters - not the call operator's.
1376 CXXMethodDecl *Invoke = CXXMethodDecl::Create(
1377 S.Context, Class, Loc, DeclarationNameInfo(InvokerName, Loc),
1378 InvokerFunctionTy, CallOperator->getTypeSourceInfo(), SC_Static,
1379 /*isInline=*/true, CSK_unspecified, CallOperator->getBody()->getEndLoc());
1380 for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I)
1381 InvokerParams[I]->setOwningFunction(Invoke);
1382 Invoke->setParams(InvokerParams);
1383 Invoke->setAccess(AS_private);
1384 Invoke->setImplicit(true);
1385 if (Class->isGenericLambda()) {
1386 FunctionTemplateDecl *TemplateCallOperator =
1387 CallOperator->getDescribedFunctionTemplate();
1388 FunctionTemplateDecl *StaticInvokerTemplate = FunctionTemplateDecl::Create(
1389 S.Context, Class, Loc, InvokerName,
1390 TemplateCallOperator->getTemplateParameters(),
1392 StaticInvokerTemplate->setAccess(AS_private);
1393 StaticInvokerTemplate->setImplicit(true);
1394 Invoke->setDescribedFunctionTemplate(StaticInvokerTemplate);
1395 Class->addDecl(StaticInvokerTemplate);
1397 Class->addDecl(Invoke);
1400 /// Add a lambda's conversion to block pointer.
1401 static void addBlockPointerConversion(Sema &S,
1402 SourceRange IntroducerRange,
1403 CXXRecordDecl *Class,
1404 CXXMethodDecl *CallOperator) {
1405 QualType FunctionTy = S.getLambdaConversionFunctionResultType(
1406 CallOperator->getType()->castAs<FunctionProtoType>());
1407 QualType BlockPtrTy = S.Context.getBlockPointerType(FunctionTy);
1409 FunctionProtoType::ExtProtoInfo ConversionEPI(
1410 S.Context.getDefaultCallingConvention(
1411 /*IsVariadic=*/false, /*IsCXXMethod=*/true));
1412 ConversionEPI.TypeQuals = Qualifiers();
1413 ConversionEPI.TypeQuals.addConst();
1414 QualType ConvTy = S.Context.getFunctionType(BlockPtrTy, None, ConversionEPI);
1416 SourceLocation Loc = IntroducerRange.getBegin();
1417 DeclarationName Name
1418 = S.Context.DeclarationNames.getCXXConversionFunctionName(
1419 S.Context.getCanonicalType(BlockPtrTy));
1420 DeclarationNameLoc NameLoc;
1421 NameLoc.NamedType.TInfo = S.Context.getTrivialTypeSourceInfo(BlockPtrTy, Loc);
1422 CXXConversionDecl *Conversion = CXXConversionDecl::Create(
1423 S.Context, Class, Loc, DeclarationNameInfo(Name, Loc, NameLoc), ConvTy,
1424 S.Context.getTrivialTypeSourceInfo(ConvTy, Loc),
1425 /*isInline=*/true, ExplicitSpecifier(), CSK_unspecified,
1426 CallOperator->getBody()->getEndLoc());
1427 Conversion->setAccess(AS_public);
1428 Conversion->setImplicit(true);
1429 Class->addDecl(Conversion);
1432 ExprResult Sema::BuildCaptureInit(const Capture &Cap,
1433 SourceLocation ImplicitCaptureLoc,
1434 bool IsOpenMPMapping) {
1435 // VLA captures don't have a stored initialization expression.
1436 if (Cap.isVLATypeCapture())
1437 return ExprResult();
1439 // An init-capture is initialized directly from its stored initializer.
1440 if (Cap.isInitCapture())
1441 return Cap.getVariable()->getInit();
1443 // For anything else, build an initialization expression. For an implicit
1444 // capture, the capture notionally happens at the capture-default, so use
1445 // that location here.
1446 SourceLocation Loc =
1447 ImplicitCaptureLoc.isValid() ? ImplicitCaptureLoc : Cap.getLocation();
1449 // C++11 [expr.prim.lambda]p21:
1450 // When the lambda-expression is evaluated, the entities that
1451 // are captured by copy are used to direct-initialize each
1452 // corresponding non-static data member of the resulting closure
1453 // object. (For array members, the array elements are
1454 // direct-initialized in increasing subscript order.) These
1455 // initializations are performed in the (unspecified) order in
1456 // which the non-static data members are declared.
1458 // C++ [expr.prim.lambda]p12:
1459 // An entity captured by a lambda-expression is odr-used (3.2) in
1460 // the scope containing the lambda-expression.
1462 IdentifierInfo *Name = nullptr;
1463 if (Cap.isThisCapture()) {
1464 QualType ThisTy = getCurrentThisType();
1465 Expr *This = BuildCXXThisExpr(Loc, ThisTy, ImplicitCaptureLoc.isValid());
1466 if (Cap.isCopyCapture())
1467 Init = CreateBuiltinUnaryOp(Loc, UO_Deref, This);
1471 assert(Cap.isVariableCapture() && "unknown kind of capture");
1472 VarDecl *Var = Cap.getVariable();
1473 Name = Var->getIdentifier();
1474 Init = BuildDeclarationNameExpr(
1475 CXXScopeSpec(), DeclarationNameInfo(Var->getDeclName(), Loc), Var);
1478 // In OpenMP, the capture kind doesn't actually describe how to capture:
1479 // variables are "mapped" onto the device in a process that does not formally
1480 // make a copy, even for a "copy capture".
1481 if (IsOpenMPMapping)
1484 if (Init.isInvalid())
1487 Expr *InitExpr = Init.get();
1488 InitializedEntity Entity = InitializedEntity::InitializeLambdaCapture(
1489 Name, Cap.getCaptureType(), Loc);
1490 InitializationKind InitKind =
1491 InitializationKind::CreateDirect(Loc, Loc, Loc);
1492 InitializationSequence InitSeq(*this, Entity, InitKind, InitExpr);
1493 return InitSeq.Perform(*this, Entity, InitKind, InitExpr);
1496 ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
1498 LambdaScopeInfo LSI = *cast<LambdaScopeInfo>(FunctionScopes.back());
1499 ActOnFinishFunctionBody(LSI.CallOperator, Body);
1500 return BuildLambdaExpr(StartLoc, Body->getEndLoc(), &LSI);
1503 static LambdaCaptureDefault
1504 mapImplicitCaptureStyle(CapturingScopeInfo::ImplicitCaptureStyle ICS) {
1506 case CapturingScopeInfo::ImpCap_None:
1508 case CapturingScopeInfo::ImpCap_LambdaByval:
1510 case CapturingScopeInfo::ImpCap_CapturedRegion:
1511 case CapturingScopeInfo::ImpCap_LambdaByref:
1513 case CapturingScopeInfo::ImpCap_Block:
1514 llvm_unreachable("block capture in lambda");
1516 llvm_unreachable("Unknown implicit capture style");
1519 bool Sema::CaptureHasSideEffects(const Capture &From) {
1520 if (From.isInitCapture()) {
1521 Expr *Init = From.getVariable()->getInit();
1522 if (Init && Init->HasSideEffects(Context))
1526 if (!From.isCopyCapture())
1529 const QualType T = From.isThisCapture()
1530 ? getCurrentThisType()->getPointeeType()
1531 : From.getCaptureType();
1533 if (T.isVolatileQualified())
1536 const Type *BaseT = T->getBaseElementTypeUnsafe();
1537 if (const CXXRecordDecl *RD = BaseT->getAsCXXRecordDecl())
1538 return !RD->isCompleteDefinition() || !RD->hasTrivialCopyConstructor() ||
1539 !RD->hasTrivialDestructor();
1544 bool Sema::DiagnoseUnusedLambdaCapture(SourceRange CaptureRange,
1545 const Capture &From) {
1546 if (CaptureHasSideEffects(From))
1549 if (From.isVLATypeCapture())
1552 auto diag = Diag(From.getLocation(), diag::warn_unused_lambda_capture);
1553 if (From.isThisCapture())
1556 diag << From.getVariable();
1557 diag << From.isNonODRUsed();
1558 diag << FixItHint::CreateRemoval(CaptureRange);
1562 /// Create a field within the lambda class or captured statement record for the
1564 FieldDecl *Sema::BuildCaptureField(RecordDecl *RD,
1565 const sema::Capture &Capture) {
1566 SourceLocation Loc = Capture.getLocation();
1567 QualType FieldType = Capture.getCaptureType();
1569 TypeSourceInfo *TSI = nullptr;
1570 if (Capture.isVariableCapture()) {
1571 auto *Var = Capture.getVariable();
1572 if (Var->isInitCapture())
1573 TSI = Capture.getVariable()->getTypeSourceInfo();
1576 // FIXME: Should we really be doing this? A null TypeSourceInfo seems more
1577 // appropriate, at least for an implicit capture.
1579 TSI = Context.getTrivialTypeSourceInfo(FieldType, Loc);
1581 // Build the non-static data member.
1583 FieldDecl::Create(Context, RD, Loc, Loc, nullptr, FieldType, TSI, nullptr,
1584 false, ICIS_NoInit);
1585 // If the variable being captured has an invalid type, mark the class as
1587 if (!FieldType->isDependentType()) {
1588 if (RequireCompleteType(Loc, FieldType, diag::err_field_incomplete)) {
1589 RD->setInvalidDecl();
1590 Field->setInvalidDecl();
1593 FieldType->isIncompleteType(&Def);
1594 if (Def && Def->isInvalidDecl()) {
1595 RD->setInvalidDecl();
1596 Field->setInvalidDecl();
1600 Field->setImplicit(true);
1601 Field->setAccess(AS_private);
1604 if (Capture.isVLATypeCapture())
1605 Field->setCapturedVLAType(Capture.getCapturedVLAType());
1610 ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
1611 LambdaScopeInfo *LSI) {
1612 // Collect information from the lambda scope.
1613 SmallVector<LambdaCapture, 4> Captures;
1614 SmallVector<Expr *, 4> CaptureInits;
1615 SourceLocation CaptureDefaultLoc = LSI->CaptureDefaultLoc;
1616 LambdaCaptureDefault CaptureDefault =
1617 mapImplicitCaptureStyle(LSI->ImpCaptureStyle);
1618 CXXRecordDecl *Class;
1619 CXXMethodDecl *CallOperator;
1620 SourceRange IntroducerRange;
1621 bool ExplicitParams;
1622 bool ExplicitResultType;
1623 CleanupInfo LambdaCleanup;
1624 bool ContainsUnexpandedParameterPack;
1625 bool IsGenericLambda;
1627 CallOperator = LSI->CallOperator;
1628 Class = LSI->Lambda;
1629 IntroducerRange = LSI->IntroducerRange;
1630 ExplicitParams = LSI->ExplicitParams;
1631 ExplicitResultType = !LSI->HasImplicitReturnType;
1632 LambdaCleanup = LSI->Cleanup;
1633 ContainsUnexpandedParameterPack = LSI->ContainsUnexpandedParameterPack;
1634 IsGenericLambda = Class->isGenericLambda();
1636 CallOperator->setLexicalDeclContext(Class);
1637 Decl *TemplateOrNonTemplateCallOperatorDecl =
1638 CallOperator->getDescribedFunctionTemplate()
1639 ? CallOperator->getDescribedFunctionTemplate()
1640 : cast<Decl>(CallOperator);
1642 TemplateOrNonTemplateCallOperatorDecl->setLexicalDeclContext(Class);
1643 Class->addDecl(TemplateOrNonTemplateCallOperatorDecl);
1645 PopExpressionEvaluationContext();
1647 // True if the current capture has a used capture or default before it.
1648 bool CurHasPreviousCapture = CaptureDefault != LCD_None;
1649 SourceLocation PrevCaptureLoc = CurHasPreviousCapture ?
1650 CaptureDefaultLoc : IntroducerRange.getBegin();
1652 for (unsigned I = 0, N = LSI->Captures.size(); I != N; ++I) {
1653 const Capture &From = LSI->Captures[I];
1655 if (From.isInvalid())
1658 assert(!From.isBlockCapture() && "Cannot capture __block variables");
1659 bool IsImplicit = I >= LSI->NumExplicitCaptures;
1660 SourceLocation ImplicitCaptureLoc =
1661 IsImplicit ? CaptureDefaultLoc : SourceLocation();
1663 // Use source ranges of explicit captures for fixits where available.
1664 SourceRange CaptureRange = LSI->ExplicitCaptureRanges[I];
1666 // Warn about unused explicit captures.
1667 bool IsCaptureUsed = true;
1668 if (!CurContext->isDependentContext() && !IsImplicit &&
1669 !From.isODRUsed()) {
1670 // Initialized captures that are non-ODR used may not be eliminated.
1671 // FIXME: Where did the IsGenericLambda here come from?
1672 bool NonODRUsedInitCapture =
1673 IsGenericLambda && From.isNonODRUsed() && From.isInitCapture();
1674 if (!NonODRUsedInitCapture) {
1675 bool IsLast = (I + 1) == LSI->NumExplicitCaptures;
1676 SourceRange FixItRange;
1677 if (CaptureRange.isValid()) {
1678 if (!CurHasPreviousCapture && !IsLast) {
1679 // If there are no captures preceding this capture, remove the
1681 FixItRange = SourceRange(CaptureRange.getBegin(),
1682 getLocForEndOfToken(CaptureRange.getEnd()));
1684 // Otherwise, remove the comma since the last used capture.
1685 FixItRange = SourceRange(getLocForEndOfToken(PrevCaptureLoc),
1686 CaptureRange.getEnd());
1690 IsCaptureUsed = !DiagnoseUnusedLambdaCapture(FixItRange, From);
1694 if (CaptureRange.isValid()) {
1695 CurHasPreviousCapture |= IsCaptureUsed;
1696 PrevCaptureLoc = CaptureRange.getEnd();
1699 // Map the capture to our AST representation.
1700 LambdaCapture Capture = [&] {
1701 if (From.isThisCapture()) {
1702 // Capturing 'this' implicitly with a default of '[=]' is deprecated,
1703 // because it results in a reference capture. Don't warn prior to
1704 // C++2a; there's nothing that can be done about it before then.
1705 if (getLangOpts().CPlusPlus2a && IsImplicit &&
1706 CaptureDefault == LCD_ByCopy) {
1707 Diag(From.getLocation(), diag::warn_deprecated_this_capture);
1708 Diag(CaptureDefaultLoc, diag::note_deprecated_this_capture)
1709 << FixItHint::CreateInsertion(
1710 getLocForEndOfToken(CaptureDefaultLoc), ", this");
1712 return LambdaCapture(From.getLocation(), IsImplicit,
1713 From.isCopyCapture() ? LCK_StarThis : LCK_This);
1714 } else if (From.isVLATypeCapture()) {
1715 return LambdaCapture(From.getLocation(), IsImplicit, LCK_VLAType);
1717 assert(From.isVariableCapture() && "unknown kind of capture");
1718 VarDecl *Var = From.getVariable();
1719 LambdaCaptureKind Kind =
1720 From.isCopyCapture() ? LCK_ByCopy : LCK_ByRef;
1721 return LambdaCapture(From.getLocation(), IsImplicit, Kind, Var,
1722 From.getEllipsisLoc());
1726 // Form the initializer for the capture field.
1727 ExprResult Init = BuildCaptureInit(From, ImplicitCaptureLoc);
1729 // FIXME: Skip this capture if the capture is not used, the initializer
1730 // has no side-effects, the type of the capture is trivial, and the
1731 // lambda is not externally visible.
1733 // Add a FieldDecl for the capture and form its initializer.
1734 BuildCaptureField(Class, From);
1735 Captures.push_back(Capture);
1736 CaptureInits.push_back(Init.get());
1739 // C++11 [expr.prim.lambda]p6:
1740 // The closure type for a lambda-expression with no lambda-capture
1741 // has a public non-virtual non-explicit const conversion function
1742 // to pointer to function having the same parameter and return
1743 // types as the closure type's function call operator.
1744 if (Captures.empty() && CaptureDefault == LCD_None)
1745 addFunctionPointerConversion(*this, IntroducerRange, Class,
1749 // The closure type for a lambda-expression has a public non-virtual
1750 // non-explicit const conversion function to a block pointer having the
1751 // same parameter and return types as the closure type's function call
1753 // FIXME: Fix generic lambda to block conversions.
1754 if (getLangOpts().Blocks && getLangOpts().ObjC && !IsGenericLambda)
1755 addBlockPointerConversion(*this, IntroducerRange, Class, CallOperator);
1757 // Finalize the lambda class.
1758 SmallVector<Decl*, 4> Fields(Class->fields());
1759 ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
1760 SourceLocation(), ParsedAttributesView());
1761 CheckCompletedCXXClass(Class);
1764 Cleanup.mergeFrom(LambdaCleanup);
1766 LambdaExpr *Lambda = LambdaExpr::Create(Context, Class, IntroducerRange,
1767 CaptureDefault, CaptureDefaultLoc,
1769 ExplicitParams, ExplicitResultType,
1770 CaptureInits, EndLoc,
1771 ContainsUnexpandedParameterPack);
1772 // If the lambda expression's call operator is not explicitly marked constexpr
1773 // and we are not in a dependent context, analyze the call operator to infer
1774 // its constexpr-ness, suppressing diagnostics while doing so.
1775 if (getLangOpts().CPlusPlus17 && !CallOperator->isInvalidDecl() &&
1776 !CallOperator->isConstexpr() &&
1777 !isa<CoroutineBodyStmt>(CallOperator->getBody()) &&
1778 !Class->getDeclContext()->isDependentContext()) {
1779 TentativeAnalysisScope DiagnosticScopeGuard(*this);
1780 CallOperator->setConstexprKind(
1781 (CheckConstexprFunctionDecl(CallOperator) &&
1782 CheckConstexprFunctionBody(CallOperator, CallOperator->getBody()))
1787 // Emit delayed shadowing warnings now that the full capture list is known.
1788 DiagnoseShadowingLambdaDecls(LSI);
1790 if (!CurContext->isDependentContext()) {
1791 switch (ExprEvalContexts.back().Context) {
1792 // C++11 [expr.prim.lambda]p2:
1793 // A lambda-expression shall not appear in an unevaluated operand
1795 case ExpressionEvaluationContext::Unevaluated:
1796 case ExpressionEvaluationContext::UnevaluatedList:
1797 case ExpressionEvaluationContext::UnevaluatedAbstract:
1798 // C++1y [expr.const]p2:
1799 // A conditional-expression e is a core constant expression unless the
1800 // evaluation of e, following the rules of the abstract machine, would
1801 // evaluate [...] a lambda-expression.
1803 // This is technically incorrect, there are some constant evaluated contexts
1804 // where this should be allowed. We should probably fix this when DR1607 is
1805 // ratified, it lays out the exact set of conditions where we shouldn't
1806 // allow a lambda-expression.
1807 case ExpressionEvaluationContext::ConstantEvaluated:
1808 // We don't actually diagnose this case immediately, because we
1809 // could be within a context where we might find out later that
1810 // the expression is potentially evaluated (e.g., for typeid).
1811 ExprEvalContexts.back().Lambdas.push_back(Lambda);
1814 case ExpressionEvaluationContext::DiscardedStatement:
1815 case ExpressionEvaluationContext::PotentiallyEvaluated:
1816 case ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed:
1821 return MaybeBindToTemporary(Lambda);
1824 ExprResult Sema::BuildBlockForLambdaConversion(SourceLocation CurrentLocation,
1825 SourceLocation ConvLocation,
1826 CXXConversionDecl *Conv,
1828 // Make sure that the lambda call operator is marked used.
1829 CXXRecordDecl *Lambda = Conv->getParent();
1830 CXXMethodDecl *CallOperator
1831 = cast<CXXMethodDecl>(
1833 Context.DeclarationNames.getCXXOperatorName(OO_Call)).front());
1834 CallOperator->setReferenced();
1835 CallOperator->markUsed(Context);
1837 ExprResult Init = PerformCopyInitialization(
1838 InitializedEntity::InitializeLambdaToBlock(ConvLocation, Src->getType(),
1840 CurrentLocation, Src);
1841 if (!Init.isInvalid())
1842 Init = ActOnFinishFullExpr(Init.get(), /*DiscardedValue*/ false);
1844 if (Init.isInvalid())
1847 // Create the new block to be returned.
1848 BlockDecl *Block = BlockDecl::Create(Context, CurContext, ConvLocation);
1850 // Set the type information.
1851 Block->setSignatureAsWritten(CallOperator->getTypeSourceInfo());
1852 Block->setIsVariadic(CallOperator->isVariadic());
1853 Block->setBlockMissingReturnType(false);
1856 SmallVector<ParmVarDecl *, 4> BlockParams;
1857 for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I) {
1858 ParmVarDecl *From = CallOperator->getParamDecl(I);
1859 BlockParams.push_back(ParmVarDecl::Create(
1860 Context, Block, From->getBeginLoc(), From->getLocation(),
1861 From->getIdentifier(), From->getType(), From->getTypeSourceInfo(),
1862 From->getStorageClass(),
1863 /*DefArg=*/nullptr));
1865 Block->setParams(BlockParams);
1867 Block->setIsConversionFromLambda(true);
1869 // Add capture. The capture uses a fake variable, which doesn't correspond
1870 // to any actual memory location. However, the initializer copy-initializes
1871 // the lambda object.
1872 TypeSourceInfo *CapVarTSI =
1873 Context.getTrivialTypeSourceInfo(Src->getType());
1874 VarDecl *CapVar = VarDecl::Create(Context, Block, ConvLocation,
1875 ConvLocation, nullptr,
1876 Src->getType(), CapVarTSI,
1878 BlockDecl::Capture Capture(/*variable=*/CapVar, /*byRef=*/false,
1879 /*nested=*/false, /*copy=*/Init.get());
1880 Block->setCaptures(Context, Capture, /*CapturesCXXThis=*/false);
1882 // Add a fake function body to the block. IR generation is responsible
1883 // for filling in the actual body, which cannot be expressed as an AST.
1884 Block->setBody(new (Context) CompoundStmt(ConvLocation));
1886 // Create the block literal expression.
1887 Expr *BuildBlock = new (Context) BlockExpr(Block, Conv->getConversionType());
1888 ExprCleanupObjects.push_back(Block);
1889 Cleanup.setExprNeedsCleanups(true);