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;
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 /// \brief 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)
230 return LSI->GLTemplateParameterList;
232 if (!LSI->AutoTemplateParams.empty()) {
233 SourceRange IntroRange = LSI->IntroducerRange;
234 SourceLocation LAngleLoc = IntroRange.getBegin();
235 SourceLocation RAngleLoc = IntroRange.getEnd();
236 LSI->GLTemplateParameterList = TemplateParameterList::Create(
238 /*Template kw loc*/ SourceLocation(), LAngleLoc,
239 llvm::makeArrayRef((NamedDecl *const *)LSI->AutoTemplateParams.data(),
240 LSI->AutoTemplateParams.size()),
243 return LSI->GLTemplateParameterList;
246 CXXRecordDecl *Sema::createLambdaClosureType(SourceRange IntroducerRange,
247 TypeSourceInfo *Info,
249 LambdaCaptureDefault CaptureDefault) {
250 DeclContext *DC = CurContext;
251 while (!(DC->isFunctionOrMethod() || DC->isRecord() || DC->isFileContext()))
252 DC = DC->getParent();
253 bool IsGenericLambda = getGenericLambdaTemplateParameterList(getCurLambda(),
255 // Start constructing the lambda class.
256 CXXRecordDecl *Class = CXXRecordDecl::CreateLambda(Context, DC, Info,
257 IntroducerRange.getBegin(),
266 /// \brief Determine whether the given context is or is enclosed in an inline
268 static bool isInInlineFunction(const DeclContext *DC) {
269 while (!DC->isFileContext()) {
270 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(DC))
274 DC = DC->getLexicalParent();
280 MangleNumberingContext *
281 Sema::getCurrentMangleNumberContext(const DeclContext *DC,
282 Decl *&ManglingContextDecl) {
283 // Compute the context for allocating mangling numbers in the current
284 // expression, if the ABI requires them.
285 ManglingContextDecl = ExprEvalContexts.back().ManglingContextDecl;
294 // Default arguments of member function parameters that appear in a class
295 // definition, as well as the initializers of data members, receive special
296 // treatment. Identify them.
297 if (ManglingContextDecl) {
298 if (ParmVarDecl *Param = dyn_cast<ParmVarDecl>(ManglingContextDecl)) {
299 if (const DeclContext *LexicalDC
300 = Param->getDeclContext()->getLexicalParent())
301 if (LexicalDC->isRecord())
302 Kind = DefaultArgument;
303 } else if (VarDecl *Var = dyn_cast<VarDecl>(ManglingContextDecl)) {
304 if (Var->getDeclContext()->isRecord())
305 Kind = StaticDataMember;
306 } else if (isa<FieldDecl>(ManglingContextDecl)) {
311 // Itanium ABI [5.1.7]:
312 // In the following contexts [...] the one-definition rule requires closure
313 // types in different translation units to "correspond":
314 bool IsInNonspecializedTemplate =
315 inTemplateInstantiation() || CurContext->isDependentContext();
318 // -- the bodies of non-exported nonspecialized template functions
319 // -- the bodies of inline functions
320 if ((IsInNonspecializedTemplate &&
321 !(ManglingContextDecl && isa<ParmVarDecl>(ManglingContextDecl))) ||
322 isInInlineFunction(CurContext)) {
323 ManglingContextDecl = nullptr;
324 while (auto *CD = dyn_cast<CapturedDecl>(DC))
325 DC = CD->getParent();
326 return &Context.getManglingNumberContext(DC);
329 ManglingContextDecl = nullptr;
333 case StaticDataMember:
334 // -- the initializers of nonspecialized static members of template classes
335 if (!IsInNonspecializedTemplate) {
336 ManglingContextDecl = nullptr;
339 // Fall through to get the current context.
343 // -- the in-class initializers of class members
344 case DefaultArgument:
345 // -- default arguments appearing in class definitions
346 return &ExprEvalContexts.back().getMangleNumberingContext(Context);
349 llvm_unreachable("unexpected context");
352 MangleNumberingContext &
353 Sema::ExpressionEvaluationContextRecord::getMangleNumberingContext(
355 assert(ManglingContextDecl && "Need to have a context declaration");
356 if (!MangleNumbering)
357 MangleNumbering = Ctx.createMangleNumberingContext();
358 return *MangleNumbering;
361 CXXMethodDecl *Sema::startLambdaDefinition(CXXRecordDecl *Class,
362 SourceRange IntroducerRange,
363 TypeSourceInfo *MethodTypeInfo,
364 SourceLocation EndLoc,
365 ArrayRef<ParmVarDecl *> Params,
366 const bool IsConstexprSpecified) {
367 QualType MethodType = MethodTypeInfo->getType();
368 TemplateParameterList *TemplateParams =
369 getGenericLambdaTemplateParameterList(getCurLambda(), *this);
370 // If a lambda appears in a dependent context or is a generic lambda (has
371 // template parameters) and has an 'auto' return type, deduce it to a
373 if (Class->isDependentContext() || TemplateParams) {
374 const FunctionProtoType *FPT = MethodType->castAs<FunctionProtoType>();
375 QualType Result = FPT->getReturnType();
376 if (Result->isUndeducedType()) {
377 Result = SubstAutoType(Result, Context.DependentTy);
378 MethodType = Context.getFunctionType(Result, FPT->getParamTypes(),
379 FPT->getExtProtoInfo());
383 // C++11 [expr.prim.lambda]p5:
384 // The closure type for a lambda-expression has a public inline function
385 // call operator (13.5.4) whose parameters and return type are described by
386 // the lambda-expression's parameter-declaration-clause and
387 // trailing-return-type respectively.
388 DeclarationName MethodName
389 = Context.DeclarationNames.getCXXOperatorName(OO_Call);
390 DeclarationNameLoc MethodNameLoc;
391 MethodNameLoc.CXXOperatorName.BeginOpNameLoc
392 = IntroducerRange.getBegin().getRawEncoding();
393 MethodNameLoc.CXXOperatorName.EndOpNameLoc
394 = IntroducerRange.getEnd().getRawEncoding();
395 CXXMethodDecl *Method
396 = CXXMethodDecl::Create(Context, Class, EndLoc,
397 DeclarationNameInfo(MethodName,
398 IntroducerRange.getBegin(),
400 MethodType, MethodTypeInfo,
403 IsConstexprSpecified,
405 Method->setAccess(AS_public);
407 // Temporarily set the lexical declaration context to the current
408 // context, so that the Scope stack matches the lexical nesting.
409 Method->setLexicalDeclContext(CurContext);
410 // Create a function template if we have a template parameter list
411 FunctionTemplateDecl *const TemplateMethod = TemplateParams ?
412 FunctionTemplateDecl::Create(Context, Class,
413 Method->getLocation(), MethodName,
416 if (TemplateMethod) {
417 TemplateMethod->setLexicalDeclContext(CurContext);
418 TemplateMethod->setAccess(AS_public);
419 Method->setDescribedFunctionTemplate(TemplateMethod);
423 if (!Params.empty()) {
424 Method->setParams(Params);
425 CheckParmsForFunctionDef(Params,
426 /*CheckParameterNames=*/false);
428 for (auto P : Method->parameters())
429 P->setOwningFunction(Method);
432 Decl *ManglingContextDecl;
433 if (MangleNumberingContext *MCtx =
434 getCurrentMangleNumberContext(Class->getDeclContext(),
435 ManglingContextDecl)) {
436 unsigned ManglingNumber = MCtx->getManglingNumber(Method);
437 Class->setLambdaMangling(ManglingNumber, ManglingContextDecl);
443 void Sema::buildLambdaScope(LambdaScopeInfo *LSI,
444 CXXMethodDecl *CallOperator,
445 SourceRange IntroducerRange,
446 LambdaCaptureDefault CaptureDefault,
447 SourceLocation CaptureDefaultLoc,
449 bool ExplicitResultType,
451 LSI->CallOperator = CallOperator;
452 CXXRecordDecl *LambdaClass = CallOperator->getParent();
453 LSI->Lambda = LambdaClass;
454 if (CaptureDefault == LCD_ByCopy)
455 LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByval;
456 else if (CaptureDefault == LCD_ByRef)
457 LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByref;
458 LSI->CaptureDefaultLoc = CaptureDefaultLoc;
459 LSI->IntroducerRange = IntroducerRange;
460 LSI->ExplicitParams = ExplicitParams;
461 LSI->Mutable = Mutable;
463 if (ExplicitResultType) {
464 LSI->ReturnType = CallOperator->getReturnType();
466 if (!LSI->ReturnType->isDependentType() &&
467 !LSI->ReturnType->isVoidType()) {
468 if (RequireCompleteType(CallOperator->getLocStart(), LSI->ReturnType,
469 diag::err_lambda_incomplete_result)) {
474 LSI->HasImplicitReturnType = true;
478 void Sema::finishLambdaExplicitCaptures(LambdaScopeInfo *LSI) {
479 LSI->finishedExplicitCaptures();
482 void Sema::addLambdaParameters(CXXMethodDecl *CallOperator, Scope *CurScope) {
483 // Introduce our parameters into the function scope
484 for (unsigned p = 0, NumParams = CallOperator->getNumParams();
485 p < NumParams; ++p) {
486 ParmVarDecl *Param = CallOperator->getParamDecl(p);
488 // If this has an identifier, add it to the scope stack.
489 if (CurScope && Param->getIdentifier()) {
490 CheckShadow(CurScope, Param);
492 PushOnScopeChains(Param, CurScope);
497 /// If this expression is an enumerator-like expression of some type
498 /// T, return the type T; otherwise, return null.
500 /// Pointer comparisons on the result here should always work because
501 /// it's derived from either the parent of an EnumConstantDecl
502 /// (i.e. the definition) or the declaration returned by
503 /// EnumType::getDecl() (i.e. the definition).
504 static EnumDecl *findEnumForBlockReturn(Expr *E) {
505 // An expression is an enumerator-like expression of type T if,
506 // ignoring parens and parens-like expressions:
507 E = E->IgnoreParens();
509 // - it is an enumerator whose enum type is T or
510 if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
511 if (EnumConstantDecl *D
512 = dyn_cast<EnumConstantDecl>(DRE->getDecl())) {
513 return cast<EnumDecl>(D->getDeclContext());
518 // - it is a comma expression whose RHS is an enumerator-like
519 // expression of type T or
520 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
521 if (BO->getOpcode() == BO_Comma)
522 return findEnumForBlockReturn(BO->getRHS());
526 // - it is a statement-expression whose value expression is an
527 // enumerator-like expression of type T or
528 if (StmtExpr *SE = dyn_cast<StmtExpr>(E)) {
529 if (Expr *last = dyn_cast_or_null<Expr>(SE->getSubStmt()->body_back()))
530 return findEnumForBlockReturn(last);
534 // - it is a ternary conditional operator (not the GNU ?:
535 // extension) whose second and third operands are
536 // enumerator-like expressions of type T or
537 if (ConditionalOperator *CO = dyn_cast<ConditionalOperator>(E)) {
538 if (EnumDecl *ED = findEnumForBlockReturn(CO->getTrueExpr()))
539 if (ED == findEnumForBlockReturn(CO->getFalseExpr()))
545 // - it is an implicit integral conversion applied to an
546 // enumerator-like expression of type T or
547 if (ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(E)) {
548 // We can sometimes see integral conversions in valid
549 // enumerator-like expressions.
550 if (ICE->getCastKind() == CK_IntegralCast)
551 return findEnumForBlockReturn(ICE->getSubExpr());
553 // Otherwise, just rely on the type.
556 // - it is an expression of that formal enum type.
557 if (const EnumType *ET = E->getType()->getAs<EnumType>()) {
558 return ET->getDecl();
565 /// Attempt to find a type T for which the returned expression of the
566 /// given statement is an enumerator-like expression of that type.
567 static EnumDecl *findEnumForBlockReturn(ReturnStmt *ret) {
568 if (Expr *retValue = ret->getRetValue())
569 return findEnumForBlockReturn(retValue);
573 /// Attempt to find a common type T for which all of the returned
574 /// expressions in a block are enumerator-like expressions of that
576 static EnumDecl *findCommonEnumForBlockReturns(ArrayRef<ReturnStmt*> returns) {
577 ArrayRef<ReturnStmt*>::iterator i = returns.begin(), e = returns.end();
579 // Try to find one for the first return.
580 EnumDecl *ED = findEnumForBlockReturn(*i);
581 if (!ED) return nullptr;
583 // Check that the rest of the returns have the same enum.
584 for (++i; i != e; ++i) {
585 if (findEnumForBlockReturn(*i) != ED)
589 // Never infer an anonymous enum type.
590 if (!ED->hasNameForLinkage()) return nullptr;
595 /// Adjust the given return statements so that they formally return
596 /// the given type. It should require, at most, an IntegralCast.
597 static void adjustBlockReturnsToEnum(Sema &S, ArrayRef<ReturnStmt*> returns,
598 QualType returnType) {
599 for (ArrayRef<ReturnStmt*>::iterator
600 i = returns.begin(), e = returns.end(); i != e; ++i) {
601 ReturnStmt *ret = *i;
602 Expr *retValue = ret->getRetValue();
603 if (S.Context.hasSameType(retValue->getType(), returnType))
606 // Right now we only support integral fixup casts.
607 assert(returnType->isIntegralOrUnscopedEnumerationType());
608 assert(retValue->getType()->isIntegralOrUnscopedEnumerationType());
610 ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(retValue);
612 Expr *E = (cleanups ? cleanups->getSubExpr() : retValue);
613 E = ImplicitCastExpr::Create(S.Context, returnType, CK_IntegralCast,
614 E, /*base path*/ nullptr, VK_RValue);
616 cleanups->setSubExpr(E);
623 void Sema::deduceClosureReturnType(CapturingScopeInfo &CSI) {
624 assert(CSI.HasImplicitReturnType);
625 // If it was ever a placeholder, it had to been deduced to DependentTy.
626 assert(CSI.ReturnType.isNull() || !CSI.ReturnType->isUndeducedType());
627 assert((!isa<LambdaScopeInfo>(CSI) || !getLangOpts().CPlusPlus14) &&
628 "lambda expressions use auto deduction in C++14 onwards");
630 // C++ core issue 975:
631 // If a lambda-expression does not include a trailing-return-type,
632 // it is as if the trailing-return-type denotes the following type:
633 // - if there are no return statements in the compound-statement,
634 // or all return statements return either an expression of type
635 // void or no expression or braced-init-list, the type void;
636 // - otherwise, if all return statements return an expression
637 // and the types of the returned expressions after
638 // lvalue-to-rvalue conversion (4.1 [conv.lval]),
639 // array-to-pointer conversion (4.2 [conv.array]), and
640 // function-to-pointer conversion (4.3 [conv.func]) are the
641 // same, that common type;
642 // - otherwise, the program is ill-formed.
644 // C++ core issue 1048 additionally removes top-level cv-qualifiers
645 // from the types of returned expressions to match the C++14 auto
648 // In addition, in blocks in non-C++ modes, if all of the return
649 // statements are enumerator-like expressions of some type T, where
650 // T has a name for linkage, then we infer the return type of the
651 // block to be that type.
653 // First case: no return statements, implicit void return type.
654 ASTContext &Ctx = getASTContext();
655 if (CSI.Returns.empty()) {
656 // It's possible there were simply no /valid/ return statements.
657 // In this case, the first one we found may have at least given us a type.
658 if (CSI.ReturnType.isNull())
659 CSI.ReturnType = Ctx.VoidTy;
663 // Second case: at least one return statement has dependent type.
664 // Delay type checking until instantiation.
665 assert(!CSI.ReturnType.isNull() && "We should have a tentative return type.");
666 if (CSI.ReturnType->isDependentType())
669 // Try to apply the enum-fuzz rule.
670 if (!getLangOpts().CPlusPlus) {
671 assert(isa<BlockScopeInfo>(CSI));
672 const EnumDecl *ED = findCommonEnumForBlockReturns(CSI.Returns);
674 CSI.ReturnType = Context.getTypeDeclType(ED);
675 adjustBlockReturnsToEnum(*this, CSI.Returns, CSI.ReturnType);
680 // Third case: only one return statement. Don't bother doing extra work!
681 SmallVectorImpl<ReturnStmt*>::iterator I = CSI.Returns.begin(),
682 E = CSI.Returns.end();
686 // General case: many return statements.
687 // Check that they all have compatible return types.
689 // We require the return types to strictly match here.
690 // Note that we've already done the required promotions as part of
691 // processing the return statement.
692 for (; I != E; ++I) {
693 const ReturnStmt *RS = *I;
694 const Expr *RetE = RS->getRetValue();
696 QualType ReturnType =
697 (RetE ? RetE->getType() : Context.VoidTy).getUnqualifiedType();
698 if (Context.getCanonicalFunctionResultType(ReturnType) ==
699 Context.getCanonicalFunctionResultType(CSI.ReturnType))
702 // FIXME: This is a poor diagnostic for ReturnStmts without expressions.
703 // TODO: It's possible that the *first* return is the divergent one.
704 Diag(RS->getLocStart(),
705 diag::err_typecheck_missing_return_type_incompatible)
706 << ReturnType << CSI.ReturnType
707 << isa<LambdaScopeInfo>(CSI);
708 // Continue iterating so that we keep emitting diagnostics.
712 QualType Sema::buildLambdaInitCaptureInitialization(SourceLocation Loc,
717 // Create an 'auto' or 'auto&' TypeSourceInfo that we can use to
719 QualType DeductType = Context.getAutoDeductType();
721 TLB.pushTypeSpec(DeductType).setNameLoc(Loc);
723 DeductType = BuildReferenceType(DeductType, true, Loc, Id);
724 assert(!DeductType.isNull() && "can't build reference to auto");
725 TLB.push<ReferenceTypeLoc>(DeductType).setSigilLoc(Loc);
727 TypeSourceInfo *TSI = TLB.getTypeSourceInfo(Context, DeductType);
729 // Deduce the type of the init capture.
730 QualType DeducedType = deduceVarTypeFromInitializer(
731 /*VarDecl*/nullptr, DeclarationName(Id), DeductType, TSI,
732 SourceRange(Loc, Loc), IsDirectInit, Init);
733 if (DeducedType.isNull())
736 // Are we a non-list direct initialization?
737 ParenListExpr *CXXDirectInit = dyn_cast<ParenListExpr>(Init);
739 // Perform initialization analysis and ensure any implicit conversions
740 // (such as lvalue-to-rvalue) are enforced.
741 InitializedEntity Entity =
742 InitializedEntity::InitializeLambdaCapture(Id, DeducedType, Loc);
743 InitializationKind Kind =
745 ? (CXXDirectInit ? InitializationKind::CreateDirect(
746 Loc, Init->getLocStart(), Init->getLocEnd())
747 : InitializationKind::CreateDirectList(Loc))
748 : InitializationKind::CreateCopy(Loc, Init->getLocStart());
750 MultiExprArg Args = Init;
753 MultiExprArg(CXXDirectInit->getExprs(), CXXDirectInit->getNumExprs());
755 InitializationSequence InitSeq(*this, Entity, Kind, Args);
756 ExprResult Result = InitSeq.Perform(*this, Entity, Kind, Args, &DclT);
758 if (Result.isInvalid())
760 Init = Result.getAs<Expr>();
762 // The init-capture initialization is a full-expression that must be
763 // processed as one before we enter the declcontext of the lambda's
765 Result = ActOnFinishFullExpr(Init, Loc, /*DiscardedValue*/ false,
766 /*IsConstexpr*/ false,
767 /*IsLambdaInitCaptureInitializer*/ true);
768 if (Result.isInvalid())
771 Init = Result.getAs<Expr>();
775 VarDecl *Sema::createLambdaInitCaptureVarDecl(SourceLocation Loc,
776 QualType InitCaptureType,
778 unsigned InitStyle, Expr *Init) {
779 TypeSourceInfo *TSI = Context.getTrivialTypeSourceInfo(InitCaptureType,
781 // Create a dummy variable representing the init-capture. This is not actually
782 // used as a variable, and only exists as a way to name and refer to the
784 // FIXME: Pass in separate source locations for '&' and identifier.
785 VarDecl *NewVD = VarDecl::Create(Context, CurContext, Loc,
786 Loc, Id, InitCaptureType, TSI, SC_Auto);
787 NewVD->setInitCapture(true);
788 NewVD->setReferenced(true);
789 // FIXME: Pass in a VarDecl::InitializationStyle.
790 NewVD->setInitStyle(static_cast<VarDecl::InitializationStyle>(InitStyle));
791 NewVD->markUsed(Context);
792 NewVD->setInit(Init);
796 FieldDecl *Sema::buildInitCaptureField(LambdaScopeInfo *LSI, VarDecl *Var) {
797 FieldDecl *Field = FieldDecl::Create(
798 Context, LSI->Lambda, Var->getLocation(), Var->getLocation(),
799 nullptr, Var->getType(), Var->getTypeSourceInfo(), nullptr, false,
801 Field->setImplicit(true);
802 Field->setAccess(AS_private);
803 LSI->Lambda->addDecl(Field);
805 LSI->addCapture(Var, /*isBlock*/false, Var->getType()->isReferenceType(),
806 /*isNested*/false, Var->getLocation(), SourceLocation(),
807 Var->getType(), Var->getInit());
811 void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
812 Declarator &ParamInfo,
814 // Determine if we're within a context where we know that the lambda will
815 // be dependent, because there are template parameters in scope.
816 bool KnownDependent = false;
817 LambdaScopeInfo *const LSI = getCurLambda();
818 assert(LSI && "LambdaScopeInfo should be on stack!");
820 // The lambda-expression's closure type might be dependent even if its
821 // semantic context isn't, if it appears within a default argument of a
822 // function template.
823 if (CurScope->getTemplateParamParent())
824 KnownDependent = true;
826 // Determine the signature of the call operator.
827 TypeSourceInfo *MethodTyInfo;
828 bool ExplicitParams = true;
829 bool ExplicitResultType = true;
830 bool ContainsUnexpandedParameterPack = false;
831 SourceLocation EndLoc;
832 SmallVector<ParmVarDecl *, 8> Params;
833 if (ParamInfo.getNumTypeObjects() == 0) {
834 // C++11 [expr.prim.lambda]p4:
835 // If a lambda-expression does not include a lambda-declarator, it is as
836 // if the lambda-declarator were ().
837 FunctionProtoType::ExtProtoInfo EPI(Context.getDefaultCallingConvention(
838 /*IsVariadic=*/false, /*IsCXXMethod=*/true));
839 EPI.HasTrailingReturn = true;
840 EPI.TypeQuals |= DeclSpec::TQ_const;
841 // C++1y [expr.prim.lambda]:
842 // The lambda return type is 'auto', which is replaced by the
843 // trailing-return type if provided and/or deduced from 'return'
845 // We don't do this before C++1y, because we don't support deduced return
847 QualType DefaultTypeForNoTrailingReturn =
848 getLangOpts().CPlusPlus14 ? Context.getAutoDeductType()
849 : Context.DependentTy;
851 Context.getFunctionType(DefaultTypeForNoTrailingReturn, None, EPI);
852 MethodTyInfo = Context.getTrivialTypeSourceInfo(MethodTy);
853 ExplicitParams = false;
854 ExplicitResultType = false;
855 EndLoc = Intro.Range.getEnd();
857 assert(ParamInfo.isFunctionDeclarator() &&
858 "lambda-declarator is a function");
859 DeclaratorChunk::FunctionTypeInfo &FTI = ParamInfo.getFunctionTypeInfo();
861 // C++11 [expr.prim.lambda]p5:
862 // This function call operator is declared const (9.3.1) if and only if
863 // the lambda-expression's parameter-declaration-clause is not followed
864 // by mutable. It is neither virtual nor declared volatile. [...]
865 if (!FTI.hasMutableQualifier())
866 FTI.TypeQuals |= DeclSpec::TQ_const;
868 MethodTyInfo = GetTypeForDeclarator(ParamInfo, CurScope);
869 assert(MethodTyInfo && "no type from lambda-declarator");
870 EndLoc = ParamInfo.getSourceRange().getEnd();
872 ExplicitResultType = FTI.hasTrailingReturnType();
874 if (FTIHasNonVoidParameters(FTI)) {
875 Params.reserve(FTI.NumParams);
876 for (unsigned i = 0, e = FTI.NumParams; i != e; ++i)
877 Params.push_back(cast<ParmVarDecl>(FTI.Params[i].Param));
880 // Check for unexpanded parameter packs in the method type.
881 if (MethodTyInfo->getType()->containsUnexpandedParameterPack())
882 ContainsUnexpandedParameterPack = true;
885 CXXRecordDecl *Class = createLambdaClosureType(Intro.Range, MethodTyInfo,
886 KnownDependent, Intro.Default);
888 CXXMethodDecl *Method =
889 startLambdaDefinition(Class, Intro.Range, MethodTyInfo, EndLoc, Params,
890 ParamInfo.getDeclSpec().isConstexprSpecified());
892 CheckCXXDefaultArguments(Method);
894 // Attributes on the lambda apply to the method.
895 ProcessDeclAttributes(CurScope, Method, ParamInfo);
897 // CUDA lambdas get implicit attributes based on the scope in which they're
899 if (getLangOpts().CUDA)
900 CUDASetLambdaAttrs(Method);
902 // Introduce the function call operator as the current declaration context.
903 PushDeclContext(CurScope, Method);
905 // Build the lambda scope.
906 buildLambdaScope(LSI, Method, Intro.Range, Intro.Default, Intro.DefaultLoc,
907 ExplicitParams, ExplicitResultType, !Method->isConst());
909 // C++11 [expr.prim.lambda]p9:
910 // A lambda-expression whose smallest enclosing scope is a block scope is a
911 // local lambda expression; any other lambda expression shall not have a
912 // capture-default or simple-capture in its lambda-introducer.
914 // For simple-captures, this is covered by the check below that any named
915 // entity is a variable that can be captured.
917 // For DR1632, we also allow a capture-default in any context where we can
918 // odr-use 'this' (in particular, in a default initializer for a non-static
920 if (Intro.Default != LCD_None && !Class->getParent()->isFunctionOrMethod() &&
921 (getCurrentThisType().isNull() ||
922 CheckCXXThisCapture(SourceLocation(), /*Explicit*/true,
923 /*BuildAndDiagnose*/false)))
924 Diag(Intro.DefaultLoc, diag::err_capture_default_non_local);
926 // Distinct capture names, for diagnostics.
927 llvm::SmallSet<IdentifierInfo*, 8> CaptureNames;
929 // Handle explicit captures.
930 SourceLocation PrevCaptureLoc
931 = Intro.Default == LCD_None? Intro.Range.getBegin() : Intro.DefaultLoc;
932 for (auto C = Intro.Captures.begin(), E = Intro.Captures.end(); C != E;
933 PrevCaptureLoc = C->Loc, ++C) {
934 if (C->Kind == LCK_This || C->Kind == LCK_StarThis) {
935 if (C->Kind == LCK_StarThis)
936 Diag(C->Loc, !getLangOpts().CPlusPlus1z
937 ? diag::ext_star_this_lambda_capture_cxx1z
938 : diag::warn_cxx14_compat_star_this_lambda_capture);
940 // C++11 [expr.prim.lambda]p8:
941 // An identifier or this shall not appear more than once in a
943 if (LSI->isCXXThisCaptured()) {
944 Diag(C->Loc, diag::err_capture_more_than_once)
945 << "'this'" << SourceRange(LSI->getCXXThisCapture().getLocation())
946 << FixItHint::CreateRemoval(
947 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
951 // C++1z [expr.prim.lambda]p8:
952 // If a lambda-capture includes a capture-default that is =, each
953 // simple-capture of that lambda-capture shall be of the form "&
954 // identifier" or "* this". [ Note: The form [&,this] is redundant but
955 // accepted for compatibility with ISO C++14. --end note ]
956 if (Intro.Default == LCD_ByCopy && C->Kind != LCK_StarThis) {
957 Diag(C->Loc, diag::err_this_capture_with_copy_default)
958 << FixItHint::CreateRemoval(
959 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
963 // C++11 [expr.prim.lambda]p12:
964 // If this is captured by a local lambda expression, its nearest
965 // enclosing function shall be a non-static member function.
966 QualType ThisCaptureType = getCurrentThisType();
967 if (ThisCaptureType.isNull()) {
968 Diag(C->Loc, diag::err_this_capture) << true;
972 CheckCXXThisCapture(C->Loc, /*Explicit=*/true, /*BuildAndDiagnose*/ true,
973 /*FunctionScopeIndexToStopAtPtr*/ nullptr,
974 C->Kind == LCK_StarThis);
978 assert(C->Id && "missing identifier for capture");
980 if (C->Init.isInvalid())
983 VarDecl *Var = nullptr;
984 if (C->Init.isUsable()) {
985 Diag(C->Loc, getLangOpts().CPlusPlus14
986 ? diag::warn_cxx11_compat_init_capture
987 : diag::ext_init_capture);
989 if (C->Init.get()->containsUnexpandedParameterPack())
990 ContainsUnexpandedParameterPack = true;
991 // If the initializer expression is usable, but the InitCaptureType
992 // is not, then an error has occurred - so ignore the capture for now.
993 // for e.g., [n{0}] { }; <-- if no <initializer_list> is included.
994 // FIXME: we should create the init capture variable and mark it invalid
996 if (C->InitCaptureType.get().isNull())
1000 switch (C->InitKind) {
1001 case LambdaCaptureInitKind::NoInit:
1002 llvm_unreachable("not an init-capture?");
1003 case LambdaCaptureInitKind::CopyInit:
1004 InitStyle = VarDecl::CInit;
1006 case LambdaCaptureInitKind::DirectInit:
1007 InitStyle = VarDecl::CallInit;
1009 case LambdaCaptureInitKind::ListInit:
1010 InitStyle = VarDecl::ListInit;
1013 Var = createLambdaInitCaptureVarDecl(C->Loc, C->InitCaptureType.get(),
1014 C->Id, InitStyle, C->Init.get());
1015 // C++1y [expr.prim.lambda]p11:
1016 // An init-capture behaves as if it declares and explicitly
1017 // captures a variable [...] whose declarative region is the
1018 // lambda-expression's compound-statement
1020 PushOnScopeChains(Var, CurScope, false);
1022 assert(C->InitKind == LambdaCaptureInitKind::NoInit &&
1023 "init capture has valid but null init?");
1025 // C++11 [expr.prim.lambda]p8:
1026 // If a lambda-capture includes a capture-default that is &, the
1027 // identifiers in the lambda-capture shall not be preceded by &.
1028 // If a lambda-capture includes a capture-default that is =, [...]
1029 // each identifier it contains shall be preceded by &.
1030 if (C->Kind == LCK_ByRef && Intro.Default == LCD_ByRef) {
1031 Diag(C->Loc, diag::err_reference_capture_with_reference_default)
1032 << FixItHint::CreateRemoval(
1033 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1035 } else if (C->Kind == LCK_ByCopy && Intro.Default == LCD_ByCopy) {
1036 Diag(C->Loc, diag::err_copy_capture_with_copy_default)
1037 << FixItHint::CreateRemoval(
1038 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1042 // C++11 [expr.prim.lambda]p10:
1043 // The identifiers in a capture-list are looked up using the usual
1044 // rules for unqualified name lookup (3.4.1)
1045 DeclarationNameInfo Name(C->Id, C->Loc);
1046 LookupResult R(*this, Name, LookupOrdinaryName);
1047 LookupName(R, CurScope);
1048 if (R.isAmbiguous())
1051 // FIXME: Disable corrections that would add qualification?
1052 CXXScopeSpec ScopeSpec;
1053 if (DiagnoseEmptyLookup(CurScope, ScopeSpec, R,
1054 llvm::make_unique<DeclFilterCCC<VarDecl>>()))
1058 Var = R.getAsSingle<VarDecl>();
1059 if (Var && DiagnoseUseOfDecl(Var, C->Loc))
1063 // C++11 [expr.prim.lambda]p8:
1064 // An identifier or this shall not appear more than once in a
1066 if (!CaptureNames.insert(C->Id).second) {
1067 if (Var && LSI->isCaptured(Var)) {
1068 Diag(C->Loc, diag::err_capture_more_than_once)
1069 << C->Id << SourceRange(LSI->getCapture(Var).getLocation())
1070 << FixItHint::CreateRemoval(
1071 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1073 // Previous capture captured something different (one or both was
1074 // an init-cpature): no fixit.
1075 Diag(C->Loc, diag::err_capture_more_than_once) << C->Id;
1079 // C++11 [expr.prim.lambda]p10:
1080 // [...] each such lookup shall find a variable with automatic storage
1081 // duration declared in the reaching scope of the local lambda expression.
1082 // Note that the 'reaching scope' check happens in tryCaptureVariable().
1084 Diag(C->Loc, diag::err_capture_does_not_name_variable) << C->Id;
1088 // Ignore invalid decls; they'll just confuse the code later.
1089 if (Var->isInvalidDecl())
1092 if (!Var->hasLocalStorage()) {
1093 Diag(C->Loc, diag::err_capture_non_automatic_variable) << C->Id;
1094 Diag(Var->getLocation(), diag::note_previous_decl) << C->Id;
1098 // C++11 [expr.prim.lambda]p23:
1099 // A capture followed by an ellipsis is a pack expansion (14.5.3).
1100 SourceLocation EllipsisLoc;
1101 if (C->EllipsisLoc.isValid()) {
1102 if (Var->isParameterPack()) {
1103 EllipsisLoc = C->EllipsisLoc;
1105 Diag(C->EllipsisLoc, diag::err_pack_expansion_without_parameter_packs)
1106 << SourceRange(C->Loc);
1108 // Just ignore the ellipsis.
1110 } else if (Var->isParameterPack()) {
1111 ContainsUnexpandedParameterPack = true;
1114 if (C->Init.isUsable()) {
1115 buildInitCaptureField(LSI, Var);
1117 TryCaptureKind Kind = C->Kind == LCK_ByRef ? TryCapture_ExplicitByRef :
1118 TryCapture_ExplicitByVal;
1119 tryCaptureVariable(Var, C->Loc, Kind, EllipsisLoc);
1122 finishLambdaExplicitCaptures(LSI);
1124 LSI->ContainsUnexpandedParameterPack = ContainsUnexpandedParameterPack;
1126 // Add lambda parameters into scope.
1127 addLambdaParameters(Method, CurScope);
1129 // Enter a new evaluation context to insulate the lambda from any
1130 // cleanups from the enclosing full-expression.
1131 PushExpressionEvaluationContext(
1132 ExpressionEvaluationContext::PotentiallyEvaluated);
1135 void Sema::ActOnLambdaError(SourceLocation StartLoc, Scope *CurScope,
1136 bool IsInstantiation) {
1137 LambdaScopeInfo *LSI = cast<LambdaScopeInfo>(FunctionScopes.back());
1139 // Leave the expression-evaluation context.
1140 DiscardCleanupsInEvaluationContext();
1141 PopExpressionEvaluationContext();
1143 // Leave the context of the lambda.
1144 if (!IsInstantiation)
1147 // Finalize the lambda.
1148 CXXRecordDecl *Class = LSI->Lambda;
1149 Class->setInvalidDecl();
1150 SmallVector<Decl*, 4> Fields(Class->fields());
1151 ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
1152 SourceLocation(), nullptr);
1153 CheckCompletedCXXClass(Class);
1155 PopFunctionScopeInfo();
1158 /// \brief Add a lambda's conversion to function pointer, as described in
1159 /// C++11 [expr.prim.lambda]p6.
1160 static void addFunctionPointerConversion(Sema &S,
1161 SourceRange IntroducerRange,
1162 CXXRecordDecl *Class,
1163 CXXMethodDecl *CallOperator) {
1164 // This conversion is explicitly disabled if the lambda's function has
1165 // pass_object_size attributes on any of its parameters.
1166 auto HasPassObjectSizeAttr = [](const ParmVarDecl *P) {
1167 return P->hasAttr<PassObjectSizeAttr>();
1169 if (llvm::any_of(CallOperator->parameters(), HasPassObjectSizeAttr))
1172 // Add the conversion to function pointer.
1173 const FunctionProtoType *CallOpProto =
1174 CallOperator->getType()->getAs<FunctionProtoType>();
1175 const FunctionProtoType::ExtProtoInfo CallOpExtInfo =
1176 CallOpProto->getExtProtoInfo();
1177 QualType PtrToFunctionTy;
1178 QualType InvokerFunctionTy;
1180 FunctionProtoType::ExtProtoInfo InvokerExtInfo = CallOpExtInfo;
1181 CallingConv CC = S.Context.getDefaultCallingConvention(
1182 CallOpProto->isVariadic(), /*IsCXXMethod=*/false);
1183 InvokerExtInfo.ExtInfo = InvokerExtInfo.ExtInfo.withCallingConv(CC);
1184 InvokerExtInfo.TypeQuals = 0;
1185 assert(InvokerExtInfo.RefQualifier == RQ_None &&
1186 "Lambda's call operator should not have a reference qualifier");
1188 S.Context.getFunctionType(CallOpProto->getReturnType(),
1189 CallOpProto->getParamTypes(), InvokerExtInfo);
1190 PtrToFunctionTy = S.Context.getPointerType(InvokerFunctionTy);
1193 // Create the type of the conversion function.
1194 FunctionProtoType::ExtProtoInfo ConvExtInfo(
1195 S.Context.getDefaultCallingConvention(
1196 /*IsVariadic=*/false, /*IsCXXMethod=*/true));
1197 // The conversion function is always const.
1198 ConvExtInfo.TypeQuals = Qualifiers::Const;
1200 S.Context.getFunctionType(PtrToFunctionTy, None, ConvExtInfo);
1202 SourceLocation Loc = IntroducerRange.getBegin();
1203 DeclarationName ConversionName
1204 = S.Context.DeclarationNames.getCXXConversionFunctionName(
1205 S.Context.getCanonicalType(PtrToFunctionTy));
1206 DeclarationNameLoc ConvNameLoc;
1207 // Construct a TypeSourceInfo for the conversion function, and wire
1208 // all the parameters appropriately for the FunctionProtoTypeLoc
1209 // so that everything works during transformation/instantiation of
1211 // The main reason for wiring up the parameters of the conversion
1212 // function with that of the call operator is so that constructs
1213 // like the following work:
1214 // auto L = [](auto b) { <-- 1
1215 // return [](auto a) -> decltype(a) { <-- 2
1219 // int (*fp)(int) = L(5);
1220 // Because the trailing return type can contain DeclRefExprs that refer
1221 // to the original call operator's variables, we hijack the call
1222 // operators ParmVarDecls below.
1223 TypeSourceInfo *ConvNamePtrToFunctionTSI =
1224 S.Context.getTrivialTypeSourceInfo(PtrToFunctionTy, Loc);
1225 ConvNameLoc.NamedType.TInfo = ConvNamePtrToFunctionTSI;
1227 // The conversion function is a conversion to a pointer-to-function.
1228 TypeSourceInfo *ConvTSI = S.Context.getTrivialTypeSourceInfo(ConvTy, Loc);
1229 FunctionProtoTypeLoc ConvTL =
1230 ConvTSI->getTypeLoc().getAs<FunctionProtoTypeLoc>();
1231 // Get the result of the conversion function which is a pointer-to-function.
1232 PointerTypeLoc PtrToFunctionTL =
1233 ConvTL.getReturnLoc().getAs<PointerTypeLoc>();
1234 // Do the same for the TypeSourceInfo that is used to name the conversion
1236 PointerTypeLoc ConvNamePtrToFunctionTL =
1237 ConvNamePtrToFunctionTSI->getTypeLoc().getAs<PointerTypeLoc>();
1239 // Get the underlying function types that the conversion function will
1240 // be converting to (should match the type of the call operator).
1241 FunctionProtoTypeLoc CallOpConvTL =
1242 PtrToFunctionTL.getPointeeLoc().getAs<FunctionProtoTypeLoc>();
1243 FunctionProtoTypeLoc CallOpConvNameTL =
1244 ConvNamePtrToFunctionTL.getPointeeLoc().getAs<FunctionProtoTypeLoc>();
1246 // Wire up the FunctionProtoTypeLocs with the call operator's parameters.
1247 // These parameter's are essentially used to transform the name and
1248 // the type of the conversion operator. By using the same parameters
1249 // as the call operator's we don't have to fix any back references that
1250 // the trailing return type of the call operator's uses (such as
1251 // decltype(some_type<decltype(a)>::type{} + decltype(a){}) etc.)
1252 // - we can simply use the return type of the call operator, and
1253 // everything should work.
1254 SmallVector<ParmVarDecl *, 4> InvokerParams;
1255 for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I) {
1256 ParmVarDecl *From = CallOperator->getParamDecl(I);
1258 InvokerParams.push_back(ParmVarDecl::Create(S.Context,
1259 // Temporarily add to the TU. This is set to the invoker below.
1260 S.Context.getTranslationUnitDecl(),
1261 From->getLocStart(),
1262 From->getLocation(),
1263 From->getIdentifier(),
1265 From->getTypeSourceInfo(),
1266 From->getStorageClass(),
1267 /*DefaultArg=*/nullptr));
1268 CallOpConvTL.setParam(I, From);
1269 CallOpConvNameTL.setParam(I, From);
1272 CXXConversionDecl *Conversion
1273 = CXXConversionDecl::Create(S.Context, Class, Loc,
1274 DeclarationNameInfo(ConversionName,
1278 /*isInline=*/true, /*isExplicit=*/false,
1279 /*isConstexpr=*/S.getLangOpts().CPlusPlus1z,
1280 CallOperator->getBody()->getLocEnd());
1281 Conversion->setAccess(AS_public);
1282 Conversion->setImplicit(true);
1284 if (Class->isGenericLambda()) {
1285 // Create a template version of the conversion operator, using the template
1286 // parameter list of the function call operator.
1287 FunctionTemplateDecl *TemplateCallOperator =
1288 CallOperator->getDescribedFunctionTemplate();
1289 FunctionTemplateDecl *ConversionTemplate =
1290 FunctionTemplateDecl::Create(S.Context, Class,
1291 Loc, ConversionName,
1292 TemplateCallOperator->getTemplateParameters(),
1294 ConversionTemplate->setAccess(AS_public);
1295 ConversionTemplate->setImplicit(true);
1296 Conversion->setDescribedFunctionTemplate(ConversionTemplate);
1297 Class->addDecl(ConversionTemplate);
1299 Class->addDecl(Conversion);
1300 // Add a non-static member function that will be the result of
1301 // the conversion with a certain unique ID.
1302 DeclarationName InvokerName = &S.Context.Idents.get(
1303 getLambdaStaticInvokerName());
1304 // FIXME: Instead of passing in the CallOperator->getTypeSourceInfo()
1305 // we should get a prebuilt TrivialTypeSourceInfo from Context
1306 // using FunctionTy & Loc and get its TypeLoc as a FunctionProtoTypeLoc
1307 // then rewire the parameters accordingly, by hoisting up the InvokeParams
1308 // loop below and then use its Params to set Invoke->setParams(...) below.
1309 // This would avoid the 'const' qualifier of the calloperator from
1310 // contaminating the type of the invoker, which is currently adjusted
1311 // in SemaTemplateDeduction.cpp:DeduceTemplateArguments. Fixing the
1312 // trailing return type of the invoker would require a visitor to rebuild
1313 // the trailing return type and adjusting all back DeclRefExpr's to refer
1314 // to the new static invoker parameters - not the call operator's.
1315 CXXMethodDecl *Invoke
1316 = CXXMethodDecl::Create(S.Context, Class, Loc,
1317 DeclarationNameInfo(InvokerName, Loc),
1319 CallOperator->getTypeSourceInfo(),
1320 SC_Static, /*IsInline=*/true,
1321 /*IsConstexpr=*/false,
1322 CallOperator->getBody()->getLocEnd());
1323 for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I)
1324 InvokerParams[I]->setOwningFunction(Invoke);
1325 Invoke->setParams(InvokerParams);
1326 Invoke->setAccess(AS_private);
1327 Invoke->setImplicit(true);
1328 if (Class->isGenericLambda()) {
1329 FunctionTemplateDecl *TemplateCallOperator =
1330 CallOperator->getDescribedFunctionTemplate();
1331 FunctionTemplateDecl *StaticInvokerTemplate = FunctionTemplateDecl::Create(
1332 S.Context, Class, Loc, InvokerName,
1333 TemplateCallOperator->getTemplateParameters(),
1335 StaticInvokerTemplate->setAccess(AS_private);
1336 StaticInvokerTemplate->setImplicit(true);
1337 Invoke->setDescribedFunctionTemplate(StaticInvokerTemplate);
1338 Class->addDecl(StaticInvokerTemplate);
1340 Class->addDecl(Invoke);
1343 /// \brief Add a lambda's conversion to block pointer.
1344 static void addBlockPointerConversion(Sema &S,
1345 SourceRange IntroducerRange,
1346 CXXRecordDecl *Class,
1347 CXXMethodDecl *CallOperator) {
1348 const FunctionProtoType *Proto =
1349 CallOperator->getType()->getAs<FunctionProtoType>();
1351 // The function type inside the block pointer type is the same as the call
1352 // operator with some tweaks. The calling convention is the default free
1353 // function convention, and the type qualifications are lost.
1354 FunctionProtoType::ExtProtoInfo BlockEPI = Proto->getExtProtoInfo();
1356 BlockEPI.ExtInfo.withCallingConv(S.Context.getDefaultCallingConvention(
1357 Proto->isVariadic(), /*IsCXXMethod=*/false));
1358 BlockEPI.TypeQuals = 0;
1359 QualType FunctionTy = S.Context.getFunctionType(
1360 Proto->getReturnType(), Proto->getParamTypes(), BlockEPI);
1361 QualType BlockPtrTy = S.Context.getBlockPointerType(FunctionTy);
1363 FunctionProtoType::ExtProtoInfo ConversionEPI(
1364 S.Context.getDefaultCallingConvention(
1365 /*IsVariadic=*/false, /*IsCXXMethod=*/true));
1366 ConversionEPI.TypeQuals = Qualifiers::Const;
1367 QualType ConvTy = S.Context.getFunctionType(BlockPtrTy, None, ConversionEPI);
1369 SourceLocation Loc = IntroducerRange.getBegin();
1370 DeclarationName Name
1371 = S.Context.DeclarationNames.getCXXConversionFunctionName(
1372 S.Context.getCanonicalType(BlockPtrTy));
1373 DeclarationNameLoc NameLoc;
1374 NameLoc.NamedType.TInfo = S.Context.getTrivialTypeSourceInfo(BlockPtrTy, Loc);
1375 CXXConversionDecl *Conversion
1376 = CXXConversionDecl::Create(S.Context, Class, Loc,
1377 DeclarationNameInfo(Name, Loc, NameLoc),
1379 S.Context.getTrivialTypeSourceInfo(ConvTy, Loc),
1380 /*isInline=*/true, /*isExplicit=*/false,
1381 /*isConstexpr=*/false,
1382 CallOperator->getBody()->getLocEnd());
1383 Conversion->setAccess(AS_public);
1384 Conversion->setImplicit(true);
1385 Class->addDecl(Conversion);
1388 static ExprResult performLambdaVarCaptureInitialization(
1389 Sema &S, const LambdaScopeInfo::Capture &Capture, FieldDecl *Field) {
1390 assert(Capture.isVariableCapture() && "not a variable capture");
1392 auto *Var = Capture.getVariable();
1393 SourceLocation Loc = Capture.getLocation();
1395 // C++11 [expr.prim.lambda]p21:
1396 // When the lambda-expression is evaluated, the entities that
1397 // are captured by copy are used to direct-initialize each
1398 // corresponding non-static data member of the resulting closure
1399 // object. (For array members, the array elements are
1400 // direct-initialized in increasing subscript order.) These
1401 // initializations are performed in the (unspecified) order in
1402 // which the non-static data members are declared.
1404 // C++ [expr.prim.lambda]p12:
1405 // An entity captured by a lambda-expression is odr-used (3.2) in
1406 // the scope containing the lambda-expression.
1407 ExprResult RefResult = S.BuildDeclarationNameExpr(
1408 CXXScopeSpec(), DeclarationNameInfo(Var->getDeclName(), Loc), Var);
1409 if (RefResult.isInvalid())
1411 Expr *Ref = RefResult.get();
1413 auto Entity = InitializedEntity::InitializeLambdaCapture(
1414 Var->getIdentifier(), Field->getType(), Loc);
1415 InitializationKind InitKind = InitializationKind::CreateDirect(Loc, Loc, Loc);
1416 InitializationSequence Init(S, Entity, InitKind, Ref);
1417 return Init.Perform(S, Entity, InitKind, Ref);
1420 ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
1422 LambdaScopeInfo LSI = *cast<LambdaScopeInfo>(FunctionScopes.back());
1423 ActOnFinishFunctionBody(LSI.CallOperator, Body);
1424 return BuildLambdaExpr(StartLoc, Body->getLocEnd(), &LSI);
1427 static LambdaCaptureDefault
1428 mapImplicitCaptureStyle(CapturingScopeInfo::ImplicitCaptureStyle ICS) {
1430 case CapturingScopeInfo::ImpCap_None:
1432 case CapturingScopeInfo::ImpCap_LambdaByval:
1434 case CapturingScopeInfo::ImpCap_CapturedRegion:
1435 case CapturingScopeInfo::ImpCap_LambdaByref:
1437 case CapturingScopeInfo::ImpCap_Block:
1438 llvm_unreachable("block capture in lambda");
1440 llvm_unreachable("Unknown implicit capture style");
1443 bool Sema::CaptureHasSideEffects(const LambdaScopeInfo::Capture &From) {
1444 if (!From.isVLATypeCapture()) {
1445 Expr *Init = From.getInitExpr();
1446 if (Init && Init->HasSideEffects(Context))
1450 if (!From.isCopyCapture())
1453 const QualType T = From.isThisCapture()
1454 ? getCurrentThisType()->getPointeeType()
1455 : From.getCaptureType();
1457 if (T.isVolatileQualified())
1460 const Type *BaseT = T->getBaseElementTypeUnsafe();
1461 if (const CXXRecordDecl *RD = BaseT->getAsCXXRecordDecl())
1462 return !RD->isCompleteDefinition() || !RD->hasTrivialCopyConstructor() ||
1463 !RD->hasTrivialDestructor();
1468 void Sema::DiagnoseUnusedLambdaCapture(const LambdaScopeInfo::Capture &From) {
1469 if (CaptureHasSideEffects(From))
1472 auto diag = Diag(From.getLocation(), diag::warn_unused_lambda_capture);
1473 if (From.isThisCapture())
1476 diag << From.getVariable();
1477 diag << From.isNonODRUsed();
1480 ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
1481 LambdaScopeInfo *LSI) {
1482 // Collect information from the lambda scope.
1483 SmallVector<LambdaCapture, 4> Captures;
1484 SmallVector<Expr *, 4> CaptureInits;
1485 SourceLocation CaptureDefaultLoc = LSI->CaptureDefaultLoc;
1486 LambdaCaptureDefault CaptureDefault =
1487 mapImplicitCaptureStyle(LSI->ImpCaptureStyle);
1488 CXXRecordDecl *Class;
1489 CXXMethodDecl *CallOperator;
1490 SourceRange IntroducerRange;
1491 bool ExplicitParams;
1492 bool ExplicitResultType;
1493 CleanupInfo LambdaCleanup;
1494 bool ContainsUnexpandedParameterPack;
1495 bool IsGenericLambda;
1497 CallOperator = LSI->CallOperator;
1498 Class = LSI->Lambda;
1499 IntroducerRange = LSI->IntroducerRange;
1500 ExplicitParams = LSI->ExplicitParams;
1501 ExplicitResultType = !LSI->HasImplicitReturnType;
1502 LambdaCleanup = LSI->Cleanup;
1503 ContainsUnexpandedParameterPack = LSI->ContainsUnexpandedParameterPack;
1504 IsGenericLambda = Class->isGenericLambda();
1506 CallOperator->setLexicalDeclContext(Class);
1507 Decl *TemplateOrNonTemplateCallOperatorDecl =
1508 CallOperator->getDescribedFunctionTemplate()
1509 ? CallOperator->getDescribedFunctionTemplate()
1510 : cast<Decl>(CallOperator);
1512 TemplateOrNonTemplateCallOperatorDecl->setLexicalDeclContext(Class);
1513 Class->addDecl(TemplateOrNonTemplateCallOperatorDecl);
1515 PopExpressionEvaluationContext();
1517 // Translate captures.
1518 auto CurField = Class->field_begin();
1519 for (unsigned I = 0, N = LSI->Captures.size(); I != N; ++I, ++CurField) {
1520 const LambdaScopeInfo::Capture &From = LSI->Captures[I];
1521 assert(!From.isBlockCapture() && "Cannot capture __block variables");
1522 bool IsImplicit = I >= LSI->NumExplicitCaptures;
1524 // Warn about unused explicit captures.
1525 if (!CurContext->isDependentContext() && !IsImplicit && !From.isODRUsed()) {
1526 // Initialized captures that are non-ODR used may not be eliminated.
1527 bool NonODRUsedInitCapture =
1528 IsGenericLambda && From.isNonODRUsed() && From.getInitExpr();
1529 if (!NonODRUsedInitCapture)
1530 DiagnoseUnusedLambdaCapture(From);
1533 // Handle 'this' capture.
1534 if (From.isThisCapture()) {
1536 LambdaCapture(From.getLocation(), IsImplicit,
1537 From.isCopyCapture() ? LCK_StarThis : LCK_This));
1538 CaptureInits.push_back(From.getInitExpr());
1541 if (From.isVLATypeCapture()) {
1543 LambdaCapture(From.getLocation(), IsImplicit, LCK_VLAType));
1544 CaptureInits.push_back(nullptr);
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();
1555 performLambdaVarCaptureInitialization(*this, From, *CurField);
1556 if (InitResult.isInvalid())
1558 Init = InitResult.get();
1560 CaptureInits.push_back(Init);
1563 // C++11 [expr.prim.lambda]p6:
1564 // The closure type for a lambda-expression with no lambda-capture
1565 // has a public non-virtual non-explicit const conversion function
1566 // to pointer to function having the same parameter and return
1567 // types as the closure type's function call operator.
1568 if (Captures.empty() && CaptureDefault == LCD_None)
1569 addFunctionPointerConversion(*this, IntroducerRange, Class,
1573 // The closure type for a lambda-expression has a public non-virtual
1574 // non-explicit const conversion function to a block pointer having the
1575 // same parameter and return types as the closure type's function call
1577 // FIXME: Fix generic lambda to block conversions.
1578 if (getLangOpts().Blocks && getLangOpts().ObjC1 && !IsGenericLambda)
1579 addBlockPointerConversion(*this, IntroducerRange, Class, CallOperator);
1581 // Finalize the lambda class.
1582 SmallVector<Decl*, 4> Fields(Class->fields());
1583 ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
1584 SourceLocation(), nullptr);
1585 CheckCompletedCXXClass(Class);
1588 Cleanup.mergeFrom(LambdaCleanup);
1590 LambdaExpr *Lambda = LambdaExpr::Create(Context, Class, IntroducerRange,
1591 CaptureDefault, CaptureDefaultLoc,
1593 ExplicitParams, ExplicitResultType,
1594 CaptureInits, EndLoc,
1595 ContainsUnexpandedParameterPack);
1596 // If the lambda expression's call operator is not explicitly marked constexpr
1597 // and we are not in a dependent context, analyze the call operator to infer
1598 // its constexpr-ness, supressing diagnostics while doing so.
1599 if (getLangOpts().CPlusPlus1z && !CallOperator->isInvalidDecl() &&
1600 !CallOperator->isConstexpr() &&
1601 !isa<CoroutineBodyStmt>(CallOperator->getBody()) &&
1602 !Class->getDeclContext()->isDependentContext()) {
1603 TentativeAnalysisScope DiagnosticScopeGuard(*this);
1604 CallOperator->setConstexpr(
1605 CheckConstexprFunctionDecl(CallOperator) &&
1606 CheckConstexprFunctionBody(CallOperator, CallOperator->getBody()));
1609 // Emit delayed shadowing warnings now that the full capture list is known.
1610 DiagnoseShadowingLambdaDecls(LSI);
1612 if (!CurContext->isDependentContext()) {
1613 switch (ExprEvalContexts.back().Context) {
1614 // C++11 [expr.prim.lambda]p2:
1615 // A lambda-expression shall not appear in an unevaluated operand
1617 case ExpressionEvaluationContext::Unevaluated:
1618 case ExpressionEvaluationContext::UnevaluatedList:
1619 case ExpressionEvaluationContext::UnevaluatedAbstract:
1620 // C++1y [expr.const]p2:
1621 // A conditional-expression e is a core constant expression unless the
1622 // evaluation of e, following the rules of the abstract machine, would
1623 // evaluate [...] a lambda-expression.
1625 // This is technically incorrect, there are some constant evaluated contexts
1626 // where this should be allowed. We should probably fix this when DR1607 is
1627 // ratified, it lays out the exact set of conditions where we shouldn't
1628 // allow a lambda-expression.
1629 case ExpressionEvaluationContext::ConstantEvaluated:
1630 // We don't actually diagnose this case immediately, because we
1631 // could be within a context where we might find out later that
1632 // the expression is potentially evaluated (e.g., for typeid).
1633 ExprEvalContexts.back().Lambdas.push_back(Lambda);
1636 case ExpressionEvaluationContext::DiscardedStatement:
1637 case ExpressionEvaluationContext::PotentiallyEvaluated:
1638 case ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed:
1643 return MaybeBindToTemporary(Lambda);
1646 ExprResult Sema::BuildBlockForLambdaConversion(SourceLocation CurrentLocation,
1647 SourceLocation ConvLocation,
1648 CXXConversionDecl *Conv,
1650 // Make sure that the lambda call operator is marked used.
1651 CXXRecordDecl *Lambda = Conv->getParent();
1652 CXXMethodDecl *CallOperator
1653 = cast<CXXMethodDecl>(
1655 Context.DeclarationNames.getCXXOperatorName(OO_Call)).front());
1656 CallOperator->setReferenced();
1657 CallOperator->markUsed(Context);
1659 ExprResult Init = PerformCopyInitialization(
1660 InitializedEntity::InitializeLambdaToBlock(ConvLocation, Src->getType(),
1662 CurrentLocation, Src);
1663 if (!Init.isInvalid())
1664 Init = ActOnFinishFullExpr(Init.get());
1666 if (Init.isInvalid())
1669 // Create the new block to be returned.
1670 BlockDecl *Block = BlockDecl::Create(Context, CurContext, ConvLocation);
1672 // Set the type information.
1673 Block->setSignatureAsWritten(CallOperator->getTypeSourceInfo());
1674 Block->setIsVariadic(CallOperator->isVariadic());
1675 Block->setBlockMissingReturnType(false);
1678 SmallVector<ParmVarDecl *, 4> BlockParams;
1679 for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I) {
1680 ParmVarDecl *From = CallOperator->getParamDecl(I);
1681 BlockParams.push_back(ParmVarDecl::Create(Context, Block,
1682 From->getLocStart(),
1683 From->getLocation(),
1684 From->getIdentifier(),
1686 From->getTypeSourceInfo(),
1687 From->getStorageClass(),
1688 /*DefaultArg=*/nullptr));
1690 Block->setParams(BlockParams);
1692 Block->setIsConversionFromLambda(true);
1694 // Add capture. The capture uses a fake variable, which doesn't correspond
1695 // to any actual memory location. However, the initializer copy-initializes
1696 // the lambda object.
1697 TypeSourceInfo *CapVarTSI =
1698 Context.getTrivialTypeSourceInfo(Src->getType());
1699 VarDecl *CapVar = VarDecl::Create(Context, Block, ConvLocation,
1700 ConvLocation, nullptr,
1701 Src->getType(), CapVarTSI,
1703 BlockDecl::Capture Capture(/*Variable=*/CapVar, /*ByRef=*/false,
1704 /*Nested=*/false, /*Copy=*/Init.get());
1705 Block->setCaptures(Context, Capture, /*CapturesCXXThis=*/false);
1707 // Add a fake function body to the block. IR generation is responsible
1708 // for filling in the actual body, which cannot be expressed as an AST.
1709 Block->setBody(new (Context) CompoundStmt(ConvLocation));
1711 // Create the block literal expression.
1712 Expr *BuildBlock = new (Context) BlockExpr(Block, Conv->getConversionType());
1713 ExprCleanupObjects.push_back(Block);
1714 Cleanup.setExprNeedsCleanups(true);