1 //===--- SemaLambda.cpp - Semantic Analysis for C++11 Lambdas -------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements semantic analysis for C++ lambda expressions.
12 //===----------------------------------------------------------------------===//
13 #include "clang/Sema/DeclSpec.h"
14 #include "TypeLocBuilder.h"
15 #include "clang/AST/ASTLambda.h"
16 #include "clang/AST/ExprCXX.h"
17 #include "clang/Basic/TargetInfo.h"
18 #include "clang/Sema/Initialization.h"
19 #include "clang/Sema/Lookup.h"
20 #include "clang/Sema/Scope.h"
21 #include "clang/Sema/ScopeInfo.h"
22 #include "clang/Sema/SemaInternal.h"
23 #include "clang/Sema/SemaLambda.h"
24 using namespace clang;
27 /// \brief Examines the FunctionScopeInfo stack to determine the nearest
28 /// enclosing lambda (to the current lambda) that is 'capture-ready' for
29 /// the variable referenced in the current lambda (i.e. \p VarToCapture).
30 /// If successful, returns the index into Sema's FunctionScopeInfo stack
31 /// of the capture-ready lambda's LambdaScopeInfo.
33 /// Climbs down the stack of lambdas (deepest nested lambda - i.e. current
34 /// lambda - is on top) to determine the index of the nearest enclosing/outer
35 /// lambda that is ready to capture the \p VarToCapture being referenced in
36 /// the current lambda.
37 /// As we climb down the stack, we want the index of the first such lambda -
38 /// that is the lambda with the highest index that is 'capture-ready'.
40 /// A lambda 'L' is capture-ready for 'V' (var or this) if:
41 /// - its enclosing context is non-dependent
42 /// - and if the chain of lambdas between L and the lambda in which
43 /// V is potentially used (i.e. the lambda at the top of the scope info
44 /// stack), can all capture or have already captured V.
45 /// If \p VarToCapture is 'null' then we are trying to capture 'this'.
47 /// Note that a lambda that is deemed 'capture-ready' still needs to be checked
48 /// for whether it is 'capture-capable' (see
49 /// getStackIndexOfNearestEnclosingCaptureCapableLambda), before it can truly
52 /// \param FunctionScopes - Sema's stack of nested FunctionScopeInfo's (which a
53 /// LambdaScopeInfo inherits from). The current/deepest/innermost lambda
54 /// is at the top of the stack and has the highest index.
55 /// \param VarToCapture - the variable to capture. If NULL, capture 'this'.
57 /// \returns An Optional<unsigned> Index that if evaluates to 'true' contains
58 /// the index (into Sema's FunctionScopeInfo stack) of the innermost lambda
59 /// which is capture-ready. If the return value evaluates to 'false' then
60 /// no lambda is capture-ready for \p VarToCapture.
62 static inline Optional<unsigned>
63 getStackIndexOfNearestEnclosingCaptureReadyLambda(
64 ArrayRef<const clang::sema::FunctionScopeInfo *> FunctionScopes,
65 VarDecl *VarToCapture) {
66 // Label failure to capture.
67 const Optional<unsigned> NoLambdaIsCaptureReady;
70 isa<clang::sema::LambdaScopeInfo>(
71 FunctionScopes[FunctionScopes.size() - 1]) &&
72 "The function on the top of sema's function-info stack must be a lambda");
74 // If VarToCapture is null, we are attempting to capture 'this'.
75 const bool IsCapturingThis = !VarToCapture;
76 const bool IsCapturingVariable = !IsCapturingThis;
78 // Start with the current lambda at the top of the stack (highest index).
79 unsigned CurScopeIndex = FunctionScopes.size() - 1;
80 DeclContext *EnclosingDC =
81 cast<sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex])->CallOperator;
84 const clang::sema::LambdaScopeInfo *LSI =
85 cast<sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex]);
86 // IF we have climbed down to an intervening enclosing lambda that contains
87 // the variable declaration - it obviously can/must not capture the
89 // Since its enclosing DC is dependent, all the lambdas between it and the
90 // innermost nested lambda are dependent (otherwise we wouldn't have
91 // arrived here) - so we don't yet have a lambda that can capture the
93 if (IsCapturingVariable &&
94 VarToCapture->getDeclContext()->Equals(EnclosingDC))
95 return NoLambdaIsCaptureReady;
97 // For an enclosing lambda to be capture ready for an entity, all
98 // intervening lambda's have to be able to capture that entity. If even
99 // one of the intervening lambda's is not capable of capturing the entity
100 // then no enclosing lambda can ever capture that entity.
104 // [](auto b) { #2 <-- an intervening lambda that can never capture 'x'
106 // f(x, c); <-- can not lead to x's speculative capture by #1 or #2
108 // If they do not have a default implicit capture, check to see
109 // if the entity has already been explicitly captured.
110 // If even a single dependent enclosing lambda lacks the capability
111 // to ever capture this variable, there is no further enclosing
112 // non-dependent lambda that can capture this variable.
113 if (LSI->ImpCaptureStyle == sema::LambdaScopeInfo::ImpCap_None) {
114 if (IsCapturingVariable && !LSI->isCaptured(VarToCapture))
115 return NoLambdaIsCaptureReady;
116 if (IsCapturingThis && !LSI->isCXXThisCaptured())
117 return NoLambdaIsCaptureReady;
119 EnclosingDC = getLambdaAwareParentOfDeclContext(EnclosingDC);
121 assert(CurScopeIndex);
123 } while (!EnclosingDC->isTranslationUnit() &&
124 EnclosingDC->isDependentContext() &&
125 isLambdaCallOperator(EnclosingDC));
127 assert(CurScopeIndex < (FunctionScopes.size() - 1));
128 // If the enclosingDC is not dependent, then the immediately nested lambda
129 // (one index above) is capture-ready.
130 if (!EnclosingDC->isDependentContext())
131 return CurScopeIndex + 1;
132 return NoLambdaIsCaptureReady;
135 /// \brief Examines the FunctionScopeInfo stack to determine the nearest
136 /// enclosing lambda (to the current lambda) that is 'capture-capable' for
137 /// the variable referenced in the current lambda (i.e. \p VarToCapture).
138 /// If successful, returns the index into Sema's FunctionScopeInfo stack
139 /// of the capture-capable lambda's LambdaScopeInfo.
141 /// Given the current stack of lambdas being processed by Sema and
142 /// the variable of interest, to identify the nearest enclosing lambda (to the
143 /// current lambda at the top of the stack) that can truly capture
144 /// a variable, it has to have the following two properties:
145 /// a) 'capture-ready' - be the innermost lambda that is 'capture-ready':
146 /// - climb down the stack (i.e. starting from the innermost and examining
147 /// each outer lambda step by step) checking if each enclosing
148 /// lambda can either implicitly or explicitly capture the variable.
149 /// Record the first such lambda that is enclosed in a non-dependent
150 /// context. If no such lambda currently exists return failure.
151 /// b) 'capture-capable' - make sure the 'capture-ready' lambda can truly
152 /// capture the variable by checking all its enclosing lambdas:
153 /// - check if all outer lambdas enclosing the 'capture-ready' lambda
154 /// identified above in 'a' can also capture the variable (this is done
155 /// via tryCaptureVariable for variables and CheckCXXThisCapture for
156 /// 'this' by passing in the index of the Lambda identified in step 'a')
158 /// \param FunctionScopes - Sema's stack of nested FunctionScopeInfo's (which a
159 /// LambdaScopeInfo inherits from). The current/deepest/innermost lambda
160 /// is at the top of the stack.
162 /// \param VarToCapture - the variable to capture. If NULL, capture 'this'.
165 /// \returns An Optional<unsigned> Index that if evaluates to 'true' contains
166 /// the index (into Sema's FunctionScopeInfo stack) of the innermost lambda
167 /// which is capture-capable. If the return value evaluates to 'false' then
168 /// no lambda is capture-capable for \p VarToCapture.
170 Optional<unsigned> clang::getStackIndexOfNearestEnclosingCaptureCapableLambda(
171 ArrayRef<const sema::FunctionScopeInfo *> FunctionScopes,
172 VarDecl *VarToCapture, Sema &S) {
174 const Optional<unsigned> NoLambdaIsCaptureCapable;
176 const Optional<unsigned> OptionalStackIndex =
177 getStackIndexOfNearestEnclosingCaptureReadyLambda(FunctionScopes,
179 if (!OptionalStackIndex)
180 return NoLambdaIsCaptureCapable;
182 const unsigned IndexOfCaptureReadyLambda = OptionalStackIndex.getValue();
183 assert(((IndexOfCaptureReadyLambda != (FunctionScopes.size() - 1)) ||
184 S.getCurGenericLambda()) &&
185 "The capture ready lambda for a potential capture can only be the "
186 "current lambda if it is a generic lambda");
188 const sema::LambdaScopeInfo *const CaptureReadyLambdaLSI =
189 cast<sema::LambdaScopeInfo>(FunctionScopes[IndexOfCaptureReadyLambda]);
191 // If VarToCapture is null, we are attempting to capture 'this'
192 const bool IsCapturingThis = !VarToCapture;
193 const bool IsCapturingVariable = !IsCapturingThis;
195 if (IsCapturingVariable) {
196 // Check if the capture-ready lambda can truly capture the variable, by
197 // checking whether all enclosing lambdas of the capture-ready lambda allow
198 // the capture - i.e. make sure it is capture-capable.
199 QualType CaptureType, DeclRefType;
200 const bool CanCaptureVariable =
201 !S.tryCaptureVariable(VarToCapture,
202 /*ExprVarIsUsedInLoc*/ SourceLocation(),
203 clang::Sema::TryCapture_Implicit,
204 /*EllipsisLoc*/ SourceLocation(),
205 /*BuildAndDiagnose*/ false, CaptureType,
206 DeclRefType, &IndexOfCaptureReadyLambda);
207 if (!CanCaptureVariable)
208 return NoLambdaIsCaptureCapable;
210 // Check if the capture-ready lambda can truly capture 'this' by checking
211 // whether all enclosing lambdas of the capture-ready lambda can capture
213 const bool CanCaptureThis =
214 !S.CheckCXXThisCapture(
215 CaptureReadyLambdaLSI->PotentialThisCaptureLocation,
216 /*Explicit*/ false, /*BuildAndDiagnose*/ false,
217 &IndexOfCaptureReadyLambda);
219 return NoLambdaIsCaptureCapable;
221 return IndexOfCaptureReadyLambda;
224 static inline TemplateParameterList *
225 getGenericLambdaTemplateParameterList(LambdaScopeInfo *LSI, Sema &SemaRef) {
226 if (LSI->GLTemplateParameterList)
227 return LSI->GLTemplateParameterList;
229 if (LSI->AutoTemplateParams.size()) {
230 SourceRange IntroRange = LSI->IntroducerRange;
231 SourceLocation LAngleLoc = IntroRange.getBegin();
232 SourceLocation RAngleLoc = IntroRange.getEnd();
233 LSI->GLTemplateParameterList = TemplateParameterList::Create(
235 /*Template kw loc*/ SourceLocation(), LAngleLoc,
236 (NamedDecl **)LSI->AutoTemplateParams.data(),
237 LSI->AutoTemplateParams.size(), RAngleLoc);
239 return LSI->GLTemplateParameterList;
242 CXXRecordDecl *Sema::createLambdaClosureType(SourceRange IntroducerRange,
243 TypeSourceInfo *Info,
245 LambdaCaptureDefault CaptureDefault) {
246 DeclContext *DC = CurContext;
247 while (!(DC->isFunctionOrMethod() || DC->isRecord() || DC->isFileContext()))
248 DC = DC->getParent();
249 bool IsGenericLambda = getGenericLambdaTemplateParameterList(getCurLambda(),
251 // Start constructing the lambda class.
252 CXXRecordDecl *Class = CXXRecordDecl::CreateLambda(Context, DC, Info,
253 IntroducerRange.getBegin(),
262 /// \brief Determine whether the given context is or is enclosed in an inline
264 static bool isInInlineFunction(const DeclContext *DC) {
265 while (!DC->isFileContext()) {
266 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(DC))
270 DC = DC->getLexicalParent();
276 MangleNumberingContext *
277 Sema::getCurrentMangleNumberContext(const DeclContext *DC,
278 Decl *&ManglingContextDecl) {
279 // Compute the context for allocating mangling numbers in the current
280 // expression, if the ABI requires them.
281 ManglingContextDecl = ExprEvalContexts.back().ManglingContextDecl;
290 // Default arguments of member function parameters that appear in a class
291 // definition, as well as the initializers of data members, receive special
292 // treatment. Identify them.
293 if (ManglingContextDecl) {
294 if (ParmVarDecl *Param = dyn_cast<ParmVarDecl>(ManglingContextDecl)) {
295 if (const DeclContext *LexicalDC
296 = Param->getDeclContext()->getLexicalParent())
297 if (LexicalDC->isRecord())
298 Kind = DefaultArgument;
299 } else if (VarDecl *Var = dyn_cast<VarDecl>(ManglingContextDecl)) {
300 if (Var->getDeclContext()->isRecord())
301 Kind = StaticDataMember;
302 } else if (isa<FieldDecl>(ManglingContextDecl)) {
307 // Itanium ABI [5.1.7]:
308 // In the following contexts [...] the one-definition rule requires closure
309 // types in different translation units to "correspond":
310 bool IsInNonspecializedTemplate =
311 !ActiveTemplateInstantiations.empty() || CurContext->isDependentContext();
314 // -- the bodies of non-exported nonspecialized template functions
315 // -- the bodies of inline functions
316 if ((IsInNonspecializedTemplate &&
317 !(ManglingContextDecl && isa<ParmVarDecl>(ManglingContextDecl))) ||
318 isInInlineFunction(CurContext)) {
319 ManglingContextDecl = nullptr;
320 return &Context.getManglingNumberContext(DC);
323 ManglingContextDecl = nullptr;
326 case StaticDataMember:
327 // -- the initializers of nonspecialized static members of template classes
328 if (!IsInNonspecializedTemplate) {
329 ManglingContextDecl = nullptr;
332 // Fall through to get the current context.
335 // -- the in-class initializers of class members
336 case DefaultArgument:
337 // -- default arguments appearing in class definitions
338 return &ExprEvalContexts.back().getMangleNumberingContext(Context);
341 llvm_unreachable("unexpected context");
344 MangleNumberingContext &
345 Sema::ExpressionEvaluationContextRecord::getMangleNumberingContext(
347 assert(ManglingContextDecl && "Need to have a context declaration");
348 if (!MangleNumbering)
349 MangleNumbering = Ctx.createMangleNumberingContext();
350 return *MangleNumbering;
353 CXXMethodDecl *Sema::startLambdaDefinition(CXXRecordDecl *Class,
354 SourceRange IntroducerRange,
355 TypeSourceInfo *MethodTypeInfo,
356 SourceLocation EndLoc,
357 ArrayRef<ParmVarDecl *> Params) {
358 QualType MethodType = MethodTypeInfo->getType();
359 TemplateParameterList *TemplateParams =
360 getGenericLambdaTemplateParameterList(getCurLambda(), *this);
361 // If a lambda appears in a dependent context or is a generic lambda (has
362 // template parameters) and has an 'auto' return type, deduce it to a
364 if (Class->isDependentContext() || TemplateParams) {
365 const FunctionProtoType *FPT = MethodType->castAs<FunctionProtoType>();
366 QualType Result = FPT->getReturnType();
367 if (Result->isUndeducedType()) {
368 Result = SubstAutoType(Result, Context.DependentTy);
369 MethodType = Context.getFunctionType(Result, FPT->getParamTypes(),
370 FPT->getExtProtoInfo());
374 // C++11 [expr.prim.lambda]p5:
375 // The closure type for a lambda-expression has a public inline function
376 // call operator (13.5.4) whose parameters and return type are described by
377 // the lambda-expression's parameter-declaration-clause and
378 // trailing-return-type respectively.
379 DeclarationName MethodName
380 = Context.DeclarationNames.getCXXOperatorName(OO_Call);
381 DeclarationNameLoc MethodNameLoc;
382 MethodNameLoc.CXXOperatorName.BeginOpNameLoc
383 = IntroducerRange.getBegin().getRawEncoding();
384 MethodNameLoc.CXXOperatorName.EndOpNameLoc
385 = IntroducerRange.getEnd().getRawEncoding();
386 CXXMethodDecl *Method
387 = CXXMethodDecl::Create(Context, Class, EndLoc,
388 DeclarationNameInfo(MethodName,
389 IntroducerRange.getBegin(),
391 MethodType, MethodTypeInfo,
394 /*isConstExpr=*/false,
396 Method->setAccess(AS_public);
398 // Temporarily set the lexical declaration context to the current
399 // context, so that the Scope stack matches the lexical nesting.
400 Method->setLexicalDeclContext(CurContext);
401 // Create a function template if we have a template parameter list
402 FunctionTemplateDecl *const TemplateMethod = TemplateParams ?
403 FunctionTemplateDecl::Create(Context, Class,
404 Method->getLocation(), MethodName,
407 if (TemplateMethod) {
408 TemplateMethod->setLexicalDeclContext(CurContext);
409 TemplateMethod->setAccess(AS_public);
410 Method->setDescribedFunctionTemplate(TemplateMethod);
414 if (!Params.empty()) {
415 Method->setParams(Params);
416 CheckParmsForFunctionDef(const_cast<ParmVarDecl **>(Params.begin()),
417 const_cast<ParmVarDecl **>(Params.end()),
418 /*CheckParameterNames=*/false);
420 for (auto P : Method->params())
421 P->setOwningFunction(Method);
424 Decl *ManglingContextDecl;
425 if (MangleNumberingContext *MCtx =
426 getCurrentMangleNumberContext(Class->getDeclContext(),
427 ManglingContextDecl)) {
428 unsigned ManglingNumber = MCtx->getManglingNumber(Method);
429 Class->setLambdaMangling(ManglingNumber, ManglingContextDecl);
435 void Sema::buildLambdaScope(LambdaScopeInfo *LSI,
436 CXXMethodDecl *CallOperator,
437 SourceRange IntroducerRange,
438 LambdaCaptureDefault CaptureDefault,
439 SourceLocation CaptureDefaultLoc,
441 bool ExplicitResultType,
443 LSI->CallOperator = CallOperator;
444 CXXRecordDecl *LambdaClass = CallOperator->getParent();
445 LSI->Lambda = LambdaClass;
446 if (CaptureDefault == LCD_ByCopy)
447 LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByval;
448 else if (CaptureDefault == LCD_ByRef)
449 LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByref;
450 LSI->CaptureDefaultLoc = CaptureDefaultLoc;
451 LSI->IntroducerRange = IntroducerRange;
452 LSI->ExplicitParams = ExplicitParams;
453 LSI->Mutable = Mutable;
455 if (ExplicitResultType) {
456 LSI->ReturnType = CallOperator->getReturnType();
458 if (!LSI->ReturnType->isDependentType() &&
459 !LSI->ReturnType->isVoidType()) {
460 if (RequireCompleteType(CallOperator->getLocStart(), LSI->ReturnType,
461 diag::err_lambda_incomplete_result)) {
466 LSI->HasImplicitReturnType = true;
470 void Sema::finishLambdaExplicitCaptures(LambdaScopeInfo *LSI) {
471 LSI->finishedExplicitCaptures();
474 void Sema::addLambdaParameters(CXXMethodDecl *CallOperator, Scope *CurScope) {
475 // Introduce our parameters into the function scope
476 for (unsigned p = 0, NumParams = CallOperator->getNumParams();
477 p < NumParams; ++p) {
478 ParmVarDecl *Param = CallOperator->getParamDecl(p);
480 // If this has an identifier, add it to the scope stack.
481 if (CurScope && Param->getIdentifier()) {
482 CheckShadow(CurScope, Param);
484 PushOnScopeChains(Param, CurScope);
489 /// If this expression is an enumerator-like expression of some type
490 /// T, return the type T; otherwise, return null.
492 /// Pointer comparisons on the result here should always work because
493 /// it's derived from either the parent of an EnumConstantDecl
494 /// (i.e. the definition) or the declaration returned by
495 /// EnumType::getDecl() (i.e. the definition).
496 static EnumDecl *findEnumForBlockReturn(Expr *E) {
497 // An expression is an enumerator-like expression of type T if,
498 // ignoring parens and parens-like expressions:
499 E = E->IgnoreParens();
501 // - it is an enumerator whose enum type is T or
502 if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
503 if (EnumConstantDecl *D
504 = dyn_cast<EnumConstantDecl>(DRE->getDecl())) {
505 return cast<EnumDecl>(D->getDeclContext());
510 // - it is a comma expression whose RHS is an enumerator-like
511 // expression of type T or
512 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
513 if (BO->getOpcode() == BO_Comma)
514 return findEnumForBlockReturn(BO->getRHS());
518 // - it is a statement-expression whose value expression is an
519 // enumerator-like expression of type T or
520 if (StmtExpr *SE = dyn_cast<StmtExpr>(E)) {
521 if (Expr *last = dyn_cast_or_null<Expr>(SE->getSubStmt()->body_back()))
522 return findEnumForBlockReturn(last);
526 // - it is a ternary conditional operator (not the GNU ?:
527 // extension) whose second and third operands are
528 // enumerator-like expressions of type T or
529 if (ConditionalOperator *CO = dyn_cast<ConditionalOperator>(E)) {
530 if (EnumDecl *ED = findEnumForBlockReturn(CO->getTrueExpr()))
531 if (ED == findEnumForBlockReturn(CO->getFalseExpr()))
537 // - it is an implicit integral conversion applied to an
538 // enumerator-like expression of type T or
539 if (ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(E)) {
540 // We can sometimes see integral conversions in valid
541 // enumerator-like expressions.
542 if (ICE->getCastKind() == CK_IntegralCast)
543 return findEnumForBlockReturn(ICE->getSubExpr());
545 // Otherwise, just rely on the type.
548 // - it is an expression of that formal enum type.
549 if (const EnumType *ET = E->getType()->getAs<EnumType>()) {
550 return ET->getDecl();
557 /// Attempt to find a type T for which the returned expression of the
558 /// given statement is an enumerator-like expression of that type.
559 static EnumDecl *findEnumForBlockReturn(ReturnStmt *ret) {
560 if (Expr *retValue = ret->getRetValue())
561 return findEnumForBlockReturn(retValue);
565 /// Attempt to find a common type T for which all of the returned
566 /// expressions in a block are enumerator-like expressions of that
568 static EnumDecl *findCommonEnumForBlockReturns(ArrayRef<ReturnStmt*> returns) {
569 ArrayRef<ReturnStmt*>::iterator i = returns.begin(), e = returns.end();
571 // Try to find one for the first return.
572 EnumDecl *ED = findEnumForBlockReturn(*i);
573 if (!ED) return nullptr;
575 // Check that the rest of the returns have the same enum.
576 for (++i; i != e; ++i) {
577 if (findEnumForBlockReturn(*i) != ED)
581 // Never infer an anonymous enum type.
582 if (!ED->hasNameForLinkage()) return nullptr;
587 /// Adjust the given return statements so that they formally return
588 /// the given type. It should require, at most, an IntegralCast.
589 static void adjustBlockReturnsToEnum(Sema &S, ArrayRef<ReturnStmt*> returns,
590 QualType returnType) {
591 for (ArrayRef<ReturnStmt*>::iterator
592 i = returns.begin(), e = returns.end(); i != e; ++i) {
593 ReturnStmt *ret = *i;
594 Expr *retValue = ret->getRetValue();
595 if (S.Context.hasSameType(retValue->getType(), returnType))
598 // Right now we only support integral fixup casts.
599 assert(returnType->isIntegralOrUnscopedEnumerationType());
600 assert(retValue->getType()->isIntegralOrUnscopedEnumerationType());
602 ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(retValue);
604 Expr *E = (cleanups ? cleanups->getSubExpr() : retValue);
605 E = ImplicitCastExpr::Create(S.Context, returnType, CK_IntegralCast,
606 E, /*base path*/ nullptr, VK_RValue);
608 cleanups->setSubExpr(E);
615 void Sema::deduceClosureReturnType(CapturingScopeInfo &CSI) {
616 assert(CSI.HasImplicitReturnType);
617 // If it was ever a placeholder, it had to been deduced to DependentTy.
618 assert(CSI.ReturnType.isNull() || !CSI.ReturnType->isUndeducedType());
620 // C++ core issue 975:
621 // If a lambda-expression does not include a trailing-return-type,
622 // it is as if the trailing-return-type denotes the following type:
623 // - if there are no return statements in the compound-statement,
624 // or all return statements return either an expression of type
625 // void or no expression or braced-init-list, the type void;
626 // - otherwise, if all return statements return an expression
627 // and the types of the returned expressions after
628 // lvalue-to-rvalue conversion (4.1 [conv.lval]),
629 // array-to-pointer conversion (4.2 [conv.array]), and
630 // function-to-pointer conversion (4.3 [conv.func]) are the
631 // same, that common type;
632 // - otherwise, the program is ill-formed.
634 // C++ core issue 1048 additionally removes top-level cv-qualifiers
635 // from the types of returned expressions to match the C++14 auto
638 // In addition, in blocks in non-C++ modes, if all of the return
639 // statements are enumerator-like expressions of some type T, where
640 // T has a name for linkage, then we infer the return type of the
641 // block to be that type.
643 // First case: no return statements, implicit void return type.
644 ASTContext &Ctx = getASTContext();
645 if (CSI.Returns.empty()) {
646 // It's possible there were simply no /valid/ return statements.
647 // In this case, the first one we found may have at least given us a type.
648 if (CSI.ReturnType.isNull())
649 CSI.ReturnType = Ctx.VoidTy;
653 // Second case: at least one return statement has dependent type.
654 // Delay type checking until instantiation.
655 assert(!CSI.ReturnType.isNull() && "We should have a tentative return type.");
656 if (CSI.ReturnType->isDependentType())
659 // Try to apply the enum-fuzz rule.
660 if (!getLangOpts().CPlusPlus) {
661 assert(isa<BlockScopeInfo>(CSI));
662 const EnumDecl *ED = findCommonEnumForBlockReturns(CSI.Returns);
664 CSI.ReturnType = Context.getTypeDeclType(ED);
665 adjustBlockReturnsToEnum(*this, CSI.Returns, CSI.ReturnType);
670 // Third case: only one return statement. Don't bother doing extra work!
671 SmallVectorImpl<ReturnStmt*>::iterator I = CSI.Returns.begin(),
672 E = CSI.Returns.end();
676 // General case: many return statements.
677 // Check that they all have compatible return types.
679 // We require the return types to strictly match here.
680 // Note that we've already done the required promotions as part of
681 // processing the return statement.
682 for (; I != E; ++I) {
683 const ReturnStmt *RS = *I;
684 const Expr *RetE = RS->getRetValue();
686 QualType ReturnType =
687 (RetE ? RetE->getType() : Context.VoidTy).getUnqualifiedType();
688 if (Context.hasSameType(ReturnType, CSI.ReturnType))
691 // FIXME: This is a poor diagnostic for ReturnStmts without expressions.
692 // TODO: It's possible that the *first* return is the divergent one.
693 Diag(RS->getLocStart(),
694 diag::err_typecheck_missing_return_type_incompatible)
695 << ReturnType << CSI.ReturnType
696 << isa<LambdaScopeInfo>(CSI);
697 // Continue iterating so that we keep emitting diagnostics.
701 QualType Sema::performLambdaInitCaptureInitialization(SourceLocation Loc,
706 // We do not need to distinguish between direct-list-initialization
707 // and copy-list-initialization here, because we will always deduce
708 // std::initializer_list<T>, and direct- and copy-list-initialization
709 // always behave the same for such a type.
710 // FIXME: We should model whether an '=' was present.
711 const bool IsDirectInit = isa<ParenListExpr>(Init) || isa<InitListExpr>(Init);
713 // Create an 'auto' or 'auto&' TypeSourceInfo that we can use to
715 QualType DeductType = Context.getAutoDeductType();
717 TLB.pushTypeSpec(DeductType).setNameLoc(Loc);
719 DeductType = BuildReferenceType(DeductType, true, Loc, Id);
720 assert(!DeductType.isNull() && "can't build reference to auto");
721 TLB.push<ReferenceTypeLoc>(DeductType).setSigilLoc(Loc);
723 TypeSourceInfo *TSI = TLB.getTypeSourceInfo(Context, DeductType);
725 // Are we a non-list direct initialization?
726 ParenListExpr *CXXDirectInit = dyn_cast<ParenListExpr>(Init);
728 Expr *DeduceInit = Init;
729 // Initializer could be a C++ direct-initializer. Deduction only works if it
730 // contains exactly one expression.
732 if (CXXDirectInit->getNumExprs() == 0) {
733 Diag(CXXDirectInit->getLocStart(), diag::err_init_capture_no_expression)
734 << DeclarationName(Id) << TSI->getType() << Loc;
736 } else if (CXXDirectInit->getNumExprs() > 1) {
737 Diag(CXXDirectInit->getExpr(1)->getLocStart(),
738 diag::err_init_capture_multiple_expressions)
739 << DeclarationName(Id) << TSI->getType() << Loc;
742 DeduceInit = CXXDirectInit->getExpr(0);
743 if (isa<InitListExpr>(DeduceInit))
744 Diag(CXXDirectInit->getLocStart(), diag::err_init_capture_paren_braces)
745 << DeclarationName(Id) << Loc;
749 // Now deduce against the initialization expression and store the deduced
751 QualType DeducedType;
752 if (DeduceAutoType(TSI, DeduceInit, DeducedType) == DAR_Failed) {
753 if (isa<InitListExpr>(Init))
754 Diag(Loc, diag::err_init_capture_deduction_failure_from_init_list)
755 << DeclarationName(Id)
756 << (DeduceInit->getType().isNull() ? TSI->getType()
757 : DeduceInit->getType())
758 << DeduceInit->getSourceRange();
760 Diag(Loc, diag::err_init_capture_deduction_failure)
761 << DeclarationName(Id) << TSI->getType()
762 << (DeduceInit->getType().isNull() ? TSI->getType()
763 : DeduceInit->getType())
764 << DeduceInit->getSourceRange();
766 if (DeducedType.isNull())
769 // Perform initialization analysis and ensure any implicit conversions
770 // (such as lvalue-to-rvalue) are enforced.
771 InitializedEntity Entity =
772 InitializedEntity::InitializeLambdaCapture(Id, DeducedType, Loc);
773 InitializationKind Kind =
775 ? (CXXDirectInit ? InitializationKind::CreateDirect(
776 Loc, Init->getLocStart(), Init->getLocEnd())
777 : InitializationKind::CreateDirectList(Loc))
778 : InitializationKind::CreateCopy(Loc, Init->getLocStart());
780 MultiExprArg Args = Init;
783 MultiExprArg(CXXDirectInit->getExprs(), CXXDirectInit->getNumExprs());
785 InitializationSequence InitSeq(*this, Entity, Kind, Args);
786 ExprResult Result = InitSeq.Perform(*this, Entity, Kind, Args, &DclT);
788 if (Result.isInvalid())
790 Init = Result.getAs<Expr>();
792 // The init-capture initialization is a full-expression that must be
793 // processed as one before we enter the declcontext of the lambda's
795 Result = ActOnFinishFullExpr(Init, Loc, /*DiscardedValue*/ false,
796 /*IsConstexpr*/ false,
797 /*IsLambdaInitCaptureInitalizer*/ true);
798 if (Result.isInvalid())
801 Init = Result.getAs<Expr>();
805 VarDecl *Sema::createLambdaInitCaptureVarDecl(SourceLocation Loc,
806 QualType InitCaptureType, IdentifierInfo *Id, Expr *Init) {
808 TypeSourceInfo *TSI = Context.getTrivialTypeSourceInfo(InitCaptureType,
810 // Create a dummy variable representing the init-capture. This is not actually
811 // used as a variable, and only exists as a way to name and refer to the
813 // FIXME: Pass in separate source locations for '&' and identifier.
814 VarDecl *NewVD = VarDecl::Create(Context, CurContext, Loc,
815 Loc, Id, InitCaptureType, TSI, SC_Auto);
816 NewVD->setInitCapture(true);
817 NewVD->setReferenced(true);
818 NewVD->markUsed(Context);
819 NewVD->setInit(Init);
823 FieldDecl *Sema::buildInitCaptureField(LambdaScopeInfo *LSI, VarDecl *Var) {
824 FieldDecl *Field = FieldDecl::Create(
825 Context, LSI->Lambda, Var->getLocation(), Var->getLocation(),
826 nullptr, Var->getType(), Var->getTypeSourceInfo(), nullptr, false,
828 Field->setImplicit(true);
829 Field->setAccess(AS_private);
830 LSI->Lambda->addDecl(Field);
832 LSI->addCapture(Var, /*isBlock*/false, Var->getType()->isReferenceType(),
833 /*isNested*/false, Var->getLocation(), SourceLocation(),
834 Var->getType(), Var->getInit());
838 void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
839 Declarator &ParamInfo,
841 // Determine if we're within a context where we know that the lambda will
842 // be dependent, because there are template parameters in scope.
843 bool KnownDependent = false;
844 LambdaScopeInfo *const LSI = getCurLambda();
845 assert(LSI && "LambdaScopeInfo should be on stack!");
846 TemplateParameterList *TemplateParams =
847 getGenericLambdaTemplateParameterList(LSI, *this);
849 if (Scope *TmplScope = CurScope->getTemplateParamParent()) {
850 // Since we have our own TemplateParams, so check if an outer scope
851 // has template params, only then are we in a dependent scope.
852 if (TemplateParams) {
853 TmplScope = TmplScope->getParent();
854 TmplScope = TmplScope ? TmplScope->getTemplateParamParent() : nullptr;
856 if (TmplScope && !TmplScope->decl_empty())
857 KnownDependent = true;
859 // Determine the signature of the call operator.
860 TypeSourceInfo *MethodTyInfo;
861 bool ExplicitParams = true;
862 bool ExplicitResultType = true;
863 bool ContainsUnexpandedParameterPack = false;
864 SourceLocation EndLoc;
865 SmallVector<ParmVarDecl *, 8> Params;
866 if (ParamInfo.getNumTypeObjects() == 0) {
867 // C++11 [expr.prim.lambda]p4:
868 // If a lambda-expression does not include a lambda-declarator, it is as
869 // if the lambda-declarator were ().
870 FunctionProtoType::ExtProtoInfo EPI(Context.getDefaultCallingConvention(
871 /*IsVariadic=*/false, /*IsCXXMethod=*/true));
872 EPI.HasTrailingReturn = true;
873 EPI.TypeQuals |= DeclSpec::TQ_const;
874 // C++1y [expr.prim.lambda]:
875 // The lambda return type is 'auto', which is replaced by the
876 // trailing-return type if provided and/or deduced from 'return'
878 // We don't do this before C++1y, because we don't support deduced return
880 QualType DefaultTypeForNoTrailingReturn =
881 getLangOpts().CPlusPlus14 ? Context.getAutoDeductType()
882 : Context.DependentTy;
884 Context.getFunctionType(DefaultTypeForNoTrailingReturn, None, EPI);
885 MethodTyInfo = Context.getTrivialTypeSourceInfo(MethodTy);
886 ExplicitParams = false;
887 ExplicitResultType = false;
888 EndLoc = Intro.Range.getEnd();
890 assert(ParamInfo.isFunctionDeclarator() &&
891 "lambda-declarator is a function");
892 DeclaratorChunk::FunctionTypeInfo &FTI = ParamInfo.getFunctionTypeInfo();
894 // C++11 [expr.prim.lambda]p5:
895 // This function call operator is declared const (9.3.1) if and only if
896 // the lambda-expression's parameter-declaration-clause is not followed
897 // by mutable. It is neither virtual nor declared volatile. [...]
898 if (!FTI.hasMutableQualifier())
899 FTI.TypeQuals |= DeclSpec::TQ_const;
901 MethodTyInfo = GetTypeForDeclarator(ParamInfo, CurScope);
902 assert(MethodTyInfo && "no type from lambda-declarator");
903 EndLoc = ParamInfo.getSourceRange().getEnd();
905 ExplicitResultType = FTI.hasTrailingReturnType();
907 if (FTIHasNonVoidParameters(FTI)) {
908 Params.reserve(FTI.NumParams);
909 for (unsigned i = 0, e = FTI.NumParams; i != e; ++i)
910 Params.push_back(cast<ParmVarDecl>(FTI.Params[i].Param));
913 // Check for unexpanded parameter packs in the method type.
914 if (MethodTyInfo->getType()->containsUnexpandedParameterPack())
915 ContainsUnexpandedParameterPack = true;
918 CXXRecordDecl *Class = createLambdaClosureType(Intro.Range, MethodTyInfo,
919 KnownDependent, Intro.Default);
921 CXXMethodDecl *Method = startLambdaDefinition(Class, Intro.Range,
922 MethodTyInfo, EndLoc, Params);
924 CheckCXXDefaultArguments(Method);
926 // Attributes on the lambda apply to the method.
927 ProcessDeclAttributes(CurScope, Method, ParamInfo);
929 // Introduce the function call operator as the current declaration context.
930 PushDeclContext(CurScope, Method);
932 // Build the lambda scope.
933 buildLambdaScope(LSI, Method, Intro.Range, Intro.Default, Intro.DefaultLoc,
934 ExplicitParams, ExplicitResultType, !Method->isConst());
936 // C++11 [expr.prim.lambda]p9:
937 // A lambda-expression whose smallest enclosing scope is a block scope is a
938 // local lambda expression; any other lambda expression shall not have a
939 // capture-default or simple-capture in its lambda-introducer.
941 // For simple-captures, this is covered by the check below that any named
942 // entity is a variable that can be captured.
944 // For DR1632, we also allow a capture-default in any context where we can
945 // odr-use 'this' (in particular, in a default initializer for a non-static
947 if (Intro.Default != LCD_None && !Class->getParent()->isFunctionOrMethod() &&
948 (getCurrentThisType().isNull() ||
949 CheckCXXThisCapture(SourceLocation(), /*Explicit*/true,
950 /*BuildAndDiagnose*/false)))
951 Diag(Intro.DefaultLoc, diag::err_capture_default_non_local);
953 // Distinct capture names, for diagnostics.
954 llvm::SmallSet<IdentifierInfo*, 8> CaptureNames;
956 // Handle explicit captures.
957 SourceLocation PrevCaptureLoc
958 = Intro.Default == LCD_None? Intro.Range.getBegin() : Intro.DefaultLoc;
959 for (auto C = Intro.Captures.begin(), E = Intro.Captures.end(); C != E;
960 PrevCaptureLoc = C->Loc, ++C) {
961 if (C->Kind == LCK_This) {
962 // C++11 [expr.prim.lambda]p8:
963 // An identifier or this shall not appear more than once in a
965 if (LSI->isCXXThisCaptured()) {
966 Diag(C->Loc, diag::err_capture_more_than_once)
967 << "'this'" << SourceRange(LSI->getCXXThisCapture().getLocation())
968 << FixItHint::CreateRemoval(
969 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
973 // C++11 [expr.prim.lambda]p8:
974 // If a lambda-capture includes a capture-default that is =, the
975 // lambda-capture shall not contain this [...].
976 if (Intro.Default == LCD_ByCopy) {
977 Diag(C->Loc, diag::err_this_capture_with_copy_default)
978 << FixItHint::CreateRemoval(
979 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
983 // C++11 [expr.prim.lambda]p12:
984 // If this is captured by a local lambda expression, its nearest
985 // enclosing function shall be a non-static member function.
986 QualType ThisCaptureType = getCurrentThisType();
987 if (ThisCaptureType.isNull()) {
988 Diag(C->Loc, diag::err_this_capture) << true;
992 CheckCXXThisCapture(C->Loc, /*Explicit=*/true);
996 assert(C->Id && "missing identifier for capture");
998 if (C->Init.isInvalid())
1001 VarDecl *Var = nullptr;
1002 if (C->Init.isUsable()) {
1003 Diag(C->Loc, getLangOpts().CPlusPlus14
1004 ? diag::warn_cxx11_compat_init_capture
1005 : diag::ext_init_capture);
1007 if (C->Init.get()->containsUnexpandedParameterPack())
1008 ContainsUnexpandedParameterPack = true;
1009 // If the initializer expression is usable, but the InitCaptureType
1010 // is not, then an error has occurred - so ignore the capture for now.
1011 // for e.g., [n{0}] { }; <-- if no <initializer_list> is included.
1012 // FIXME: we should create the init capture variable and mark it invalid
1014 if (C->InitCaptureType.get().isNull())
1016 Var = createLambdaInitCaptureVarDecl(C->Loc, C->InitCaptureType.get(),
1017 C->Id, C->Init.get());
1018 // C++1y [expr.prim.lambda]p11:
1019 // An init-capture behaves as if it declares and explicitly
1020 // captures a variable [...] whose declarative region is the
1021 // lambda-expression's compound-statement
1023 PushOnScopeChains(Var, CurScope, false);
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(PotentiallyEvaluated);
1134 void Sema::ActOnLambdaError(SourceLocation StartLoc, Scope *CurScope,
1135 bool IsInstantiation) {
1136 LambdaScopeInfo *LSI = cast<LambdaScopeInfo>(FunctionScopes.back());
1138 // Leave the expression-evaluation context.
1139 DiscardCleanupsInEvaluationContext();
1140 PopExpressionEvaluationContext();
1142 // Leave the context of the lambda.
1143 if (!IsInstantiation)
1146 // Finalize the lambda.
1147 CXXRecordDecl *Class = LSI->Lambda;
1148 Class->setInvalidDecl();
1149 SmallVector<Decl*, 4> Fields(Class->fields());
1150 ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
1151 SourceLocation(), nullptr);
1152 CheckCompletedCXXClass(Class);
1154 PopFunctionScopeInfo();
1157 /// \brief Add a lambda's conversion to function pointer, as described in
1158 /// C++11 [expr.prim.lambda]p6.
1159 static void addFunctionPointerConversion(Sema &S,
1160 SourceRange IntroducerRange,
1161 CXXRecordDecl *Class,
1162 CXXMethodDecl *CallOperator) {
1163 // Add the conversion to function pointer.
1164 const FunctionProtoType *CallOpProto =
1165 CallOperator->getType()->getAs<FunctionProtoType>();
1166 const FunctionProtoType::ExtProtoInfo CallOpExtInfo =
1167 CallOpProto->getExtProtoInfo();
1168 QualType PtrToFunctionTy;
1169 QualType InvokerFunctionTy;
1171 FunctionProtoType::ExtProtoInfo InvokerExtInfo = CallOpExtInfo;
1172 CallingConv CC = S.Context.getDefaultCallingConvention(
1173 CallOpProto->isVariadic(), /*IsCXXMethod=*/false);
1174 InvokerExtInfo.ExtInfo = InvokerExtInfo.ExtInfo.withCallingConv(CC);
1175 InvokerExtInfo.TypeQuals = 0;
1176 assert(InvokerExtInfo.RefQualifier == RQ_None &&
1177 "Lambda's call operator should not have a reference qualifier");
1179 S.Context.getFunctionType(CallOpProto->getReturnType(),
1180 CallOpProto->getParamTypes(), InvokerExtInfo);
1181 PtrToFunctionTy = S.Context.getPointerType(InvokerFunctionTy);
1184 // Create the type of the conversion function.
1185 FunctionProtoType::ExtProtoInfo ConvExtInfo(
1186 S.Context.getDefaultCallingConvention(
1187 /*IsVariadic=*/false, /*IsCXXMethod=*/true));
1188 // The conversion function is always const.
1189 ConvExtInfo.TypeQuals = Qualifiers::Const;
1191 S.Context.getFunctionType(PtrToFunctionTy, None, ConvExtInfo);
1193 SourceLocation Loc = IntroducerRange.getBegin();
1194 DeclarationName ConversionName
1195 = S.Context.DeclarationNames.getCXXConversionFunctionName(
1196 S.Context.getCanonicalType(PtrToFunctionTy));
1197 DeclarationNameLoc ConvNameLoc;
1198 // Construct a TypeSourceInfo for the conversion function, and wire
1199 // all the parameters appropriately for the FunctionProtoTypeLoc
1200 // so that everything works during transformation/instantiation of
1202 // The main reason for wiring up the parameters of the conversion
1203 // function with that of the call operator is so that constructs
1204 // like the following work:
1205 // auto L = [](auto b) { <-- 1
1206 // return [](auto a) -> decltype(a) { <-- 2
1210 // int (*fp)(int) = L(5);
1211 // Because the trailing return type can contain DeclRefExprs that refer
1212 // to the original call operator's variables, we hijack the call
1213 // operators ParmVarDecls below.
1214 TypeSourceInfo *ConvNamePtrToFunctionTSI =
1215 S.Context.getTrivialTypeSourceInfo(PtrToFunctionTy, Loc);
1216 ConvNameLoc.NamedType.TInfo = ConvNamePtrToFunctionTSI;
1218 // The conversion function is a conversion to a pointer-to-function.
1219 TypeSourceInfo *ConvTSI = S.Context.getTrivialTypeSourceInfo(ConvTy, Loc);
1220 FunctionProtoTypeLoc ConvTL =
1221 ConvTSI->getTypeLoc().getAs<FunctionProtoTypeLoc>();
1222 // Get the result of the conversion function which is a pointer-to-function.
1223 PointerTypeLoc PtrToFunctionTL =
1224 ConvTL.getReturnLoc().getAs<PointerTypeLoc>();
1225 // Do the same for the TypeSourceInfo that is used to name the conversion
1227 PointerTypeLoc ConvNamePtrToFunctionTL =
1228 ConvNamePtrToFunctionTSI->getTypeLoc().getAs<PointerTypeLoc>();
1230 // Get the underlying function types that the conversion function will
1231 // be converting to (should match the type of the call operator).
1232 FunctionProtoTypeLoc CallOpConvTL =
1233 PtrToFunctionTL.getPointeeLoc().getAs<FunctionProtoTypeLoc>();
1234 FunctionProtoTypeLoc CallOpConvNameTL =
1235 ConvNamePtrToFunctionTL.getPointeeLoc().getAs<FunctionProtoTypeLoc>();
1237 // Wire up the FunctionProtoTypeLocs with the call operator's parameters.
1238 // These parameter's are essentially used to transform the name and
1239 // the type of the conversion operator. By using the same parameters
1240 // as the call operator's we don't have to fix any back references that
1241 // the trailing return type of the call operator's uses (such as
1242 // decltype(some_type<decltype(a)>::type{} + decltype(a){}) etc.)
1243 // - we can simply use the return type of the call operator, and
1244 // everything should work.
1245 SmallVector<ParmVarDecl *, 4> InvokerParams;
1246 for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I) {
1247 ParmVarDecl *From = CallOperator->getParamDecl(I);
1249 InvokerParams.push_back(ParmVarDecl::Create(S.Context,
1250 // Temporarily add to the TU. This is set to the invoker below.
1251 S.Context.getTranslationUnitDecl(),
1252 From->getLocStart(),
1253 From->getLocation(),
1254 From->getIdentifier(),
1256 From->getTypeSourceInfo(),
1257 From->getStorageClass(),
1258 /*DefaultArg=*/nullptr));
1259 CallOpConvTL.setParam(I, From);
1260 CallOpConvNameTL.setParam(I, From);
1263 CXXConversionDecl *Conversion
1264 = CXXConversionDecl::Create(S.Context, Class, Loc,
1265 DeclarationNameInfo(ConversionName,
1269 /*isInline=*/true, /*isExplicit=*/false,
1270 /*isConstexpr=*/false,
1271 CallOperator->getBody()->getLocEnd());
1272 Conversion->setAccess(AS_public);
1273 Conversion->setImplicit(true);
1275 if (Class->isGenericLambda()) {
1276 // Create a template version of the conversion operator, using the template
1277 // parameter list of the function call operator.
1278 FunctionTemplateDecl *TemplateCallOperator =
1279 CallOperator->getDescribedFunctionTemplate();
1280 FunctionTemplateDecl *ConversionTemplate =
1281 FunctionTemplateDecl::Create(S.Context, Class,
1282 Loc, ConversionName,
1283 TemplateCallOperator->getTemplateParameters(),
1285 ConversionTemplate->setAccess(AS_public);
1286 ConversionTemplate->setImplicit(true);
1287 Conversion->setDescribedFunctionTemplate(ConversionTemplate);
1288 Class->addDecl(ConversionTemplate);
1290 Class->addDecl(Conversion);
1291 // Add a non-static member function that will be the result of
1292 // the conversion with a certain unique ID.
1293 DeclarationName InvokerName = &S.Context.Idents.get(
1294 getLambdaStaticInvokerName());
1295 // FIXME: Instead of passing in the CallOperator->getTypeSourceInfo()
1296 // we should get a prebuilt TrivialTypeSourceInfo from Context
1297 // using FunctionTy & Loc and get its TypeLoc as a FunctionProtoTypeLoc
1298 // then rewire the parameters accordingly, by hoisting up the InvokeParams
1299 // loop below and then use its Params to set Invoke->setParams(...) below.
1300 // This would avoid the 'const' qualifier of the calloperator from
1301 // contaminating the type of the invoker, which is currently adjusted
1302 // in SemaTemplateDeduction.cpp:DeduceTemplateArguments. Fixing the
1303 // trailing return type of the invoker would require a visitor to rebuild
1304 // the trailing return type and adjusting all back DeclRefExpr's to refer
1305 // to the new static invoker parameters - not the call operator's.
1306 CXXMethodDecl *Invoke
1307 = CXXMethodDecl::Create(S.Context, Class, Loc,
1308 DeclarationNameInfo(InvokerName, Loc),
1310 CallOperator->getTypeSourceInfo(),
1311 SC_Static, /*IsInline=*/true,
1312 /*IsConstexpr=*/false,
1313 CallOperator->getBody()->getLocEnd());
1314 for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I)
1315 InvokerParams[I]->setOwningFunction(Invoke);
1316 Invoke->setParams(InvokerParams);
1317 Invoke->setAccess(AS_private);
1318 Invoke->setImplicit(true);
1319 if (Class->isGenericLambda()) {
1320 FunctionTemplateDecl *TemplateCallOperator =
1321 CallOperator->getDescribedFunctionTemplate();
1322 FunctionTemplateDecl *StaticInvokerTemplate = FunctionTemplateDecl::Create(
1323 S.Context, Class, Loc, InvokerName,
1324 TemplateCallOperator->getTemplateParameters(),
1326 StaticInvokerTemplate->setAccess(AS_private);
1327 StaticInvokerTemplate->setImplicit(true);
1328 Invoke->setDescribedFunctionTemplate(StaticInvokerTemplate);
1329 Class->addDecl(StaticInvokerTemplate);
1331 Class->addDecl(Invoke);
1334 /// \brief Add a lambda's conversion to block pointer.
1335 static void addBlockPointerConversion(Sema &S,
1336 SourceRange IntroducerRange,
1337 CXXRecordDecl *Class,
1338 CXXMethodDecl *CallOperator) {
1339 const FunctionProtoType *Proto =
1340 CallOperator->getType()->getAs<FunctionProtoType>();
1342 // The function type inside the block pointer type is the same as the call
1343 // operator with some tweaks. The calling convention is the default free
1344 // function convention, and the type qualifications are lost.
1345 FunctionProtoType::ExtProtoInfo BlockEPI = Proto->getExtProtoInfo();
1347 BlockEPI.ExtInfo.withCallingConv(S.Context.getDefaultCallingConvention(
1348 Proto->isVariadic(), /*IsCXXMethod=*/false));
1349 BlockEPI.TypeQuals = 0;
1350 QualType FunctionTy = S.Context.getFunctionType(
1351 Proto->getReturnType(), Proto->getParamTypes(), BlockEPI);
1352 QualType BlockPtrTy = S.Context.getBlockPointerType(FunctionTy);
1354 FunctionProtoType::ExtProtoInfo ConversionEPI(
1355 S.Context.getDefaultCallingConvention(
1356 /*IsVariadic=*/false, /*IsCXXMethod=*/true));
1357 ConversionEPI.TypeQuals = Qualifiers::Const;
1358 QualType ConvTy = S.Context.getFunctionType(BlockPtrTy, None, ConversionEPI);
1360 SourceLocation Loc = IntroducerRange.getBegin();
1361 DeclarationName Name
1362 = S.Context.DeclarationNames.getCXXConversionFunctionName(
1363 S.Context.getCanonicalType(BlockPtrTy));
1364 DeclarationNameLoc NameLoc;
1365 NameLoc.NamedType.TInfo = S.Context.getTrivialTypeSourceInfo(BlockPtrTy, Loc);
1366 CXXConversionDecl *Conversion
1367 = CXXConversionDecl::Create(S.Context, Class, Loc,
1368 DeclarationNameInfo(Name, Loc, NameLoc),
1370 S.Context.getTrivialTypeSourceInfo(ConvTy, Loc),
1371 /*isInline=*/true, /*isExplicit=*/false,
1372 /*isConstexpr=*/false,
1373 CallOperator->getBody()->getLocEnd());
1374 Conversion->setAccess(AS_public);
1375 Conversion->setImplicit(true);
1376 Class->addDecl(Conversion);
1379 static ExprResult performLambdaVarCaptureInitialization(
1380 Sema &S, LambdaScopeInfo::Capture &Capture,
1382 SmallVectorImpl<VarDecl *> &ArrayIndexVars,
1383 SmallVectorImpl<unsigned> &ArrayIndexStarts) {
1384 assert(Capture.isVariableCapture() && "not a variable capture");
1386 auto *Var = Capture.getVariable();
1387 SourceLocation Loc = Capture.getLocation();
1389 // C++11 [expr.prim.lambda]p21:
1390 // When the lambda-expression is evaluated, the entities that
1391 // are captured by copy are used to direct-initialize each
1392 // corresponding non-static data member of the resulting closure
1393 // object. (For array members, the array elements are
1394 // direct-initialized in increasing subscript order.) These
1395 // initializations are performed in the (unspecified) order in
1396 // which the non-static data members are declared.
1398 // C++ [expr.prim.lambda]p12:
1399 // An entity captured by a lambda-expression is odr-used (3.2) in
1400 // the scope containing the lambda-expression.
1401 ExprResult RefResult = S.BuildDeclarationNameExpr(
1402 CXXScopeSpec(), DeclarationNameInfo(Var->getDeclName(), Loc), Var);
1403 if (RefResult.isInvalid())
1405 Expr *Ref = RefResult.get();
1407 QualType FieldType = Field->getType();
1409 // When the variable has array type, create index variables for each
1410 // dimension of the array. We use these index variables to subscript
1411 // the source array, and other clients (e.g., CodeGen) will perform
1412 // the necessary iteration with these index variables.
1414 // FIXME: This is dumb. Add a proper AST representation for array
1415 // copy-construction and use it here.
1416 SmallVector<VarDecl *, 4> IndexVariables;
1417 QualType BaseType = FieldType;
1418 QualType SizeType = S.Context.getSizeType();
1419 ArrayIndexStarts.push_back(ArrayIndexVars.size());
1420 while (const ConstantArrayType *Array
1421 = S.Context.getAsConstantArrayType(BaseType)) {
1422 // Create the iteration variable for this array index.
1423 IdentifierInfo *IterationVarName = nullptr;
1426 llvm::raw_svector_ostream OS(Str);
1427 OS << "__i" << IndexVariables.size();
1428 IterationVarName = &S.Context.Idents.get(OS.str());
1430 VarDecl *IterationVar = VarDecl::Create(
1431 S.Context, S.CurContext, Loc, Loc, IterationVarName, SizeType,
1432 S.Context.getTrivialTypeSourceInfo(SizeType, Loc), SC_None);
1433 IterationVar->setImplicit();
1434 IndexVariables.push_back(IterationVar);
1435 ArrayIndexVars.push_back(IterationVar);
1437 // Create a reference to the iteration variable.
1438 ExprResult IterationVarRef =
1439 S.BuildDeclRefExpr(IterationVar, SizeType, VK_LValue, Loc);
1440 assert(!IterationVarRef.isInvalid() &&
1441 "Reference to invented variable cannot fail!");
1442 IterationVarRef = S.DefaultLvalueConversion(IterationVarRef.get());
1443 assert(!IterationVarRef.isInvalid() &&
1444 "Conversion of invented variable cannot fail!");
1446 // Subscript the array with this iteration variable.
1447 ExprResult Subscript =
1448 S.CreateBuiltinArraySubscriptExpr(Ref, Loc, IterationVarRef.get(), Loc);
1449 if (Subscript.isInvalid())
1452 Ref = Subscript.get();
1453 BaseType = Array->getElementType();
1456 // Construct the entity that we will be initializing. For an array, this
1457 // will be first element in the array, which may require several levels
1458 // of array-subscript entities.
1459 SmallVector<InitializedEntity, 4> Entities;
1460 Entities.reserve(1 + IndexVariables.size());
1461 Entities.push_back(InitializedEntity::InitializeLambdaCapture(
1462 Var->getIdentifier(), FieldType, Loc));
1463 for (unsigned I = 0, N = IndexVariables.size(); I != N; ++I)
1465 InitializedEntity::InitializeElement(S.Context, 0, Entities.back()));
1467 InitializationKind InitKind = InitializationKind::CreateDirect(Loc, Loc, Loc);
1468 InitializationSequence Init(S, Entities.back(), InitKind, Ref);
1469 return Init.Perform(S, Entities.back(), InitKind, Ref);
1472 ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
1474 LambdaScopeInfo LSI = *cast<LambdaScopeInfo>(FunctionScopes.back());
1475 ActOnFinishFunctionBody(LSI.CallOperator, Body);
1476 return BuildLambdaExpr(StartLoc, Body->getLocEnd(), &LSI);
1479 static LambdaCaptureDefault
1480 mapImplicitCaptureStyle(CapturingScopeInfo::ImplicitCaptureStyle ICS) {
1482 case CapturingScopeInfo::ImpCap_None:
1484 case CapturingScopeInfo::ImpCap_LambdaByval:
1486 case CapturingScopeInfo::ImpCap_CapturedRegion:
1487 case CapturingScopeInfo::ImpCap_LambdaByref:
1489 case CapturingScopeInfo::ImpCap_Block:
1490 llvm_unreachable("block capture in lambda");
1492 llvm_unreachable("Unknown implicit capture style");
1495 ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
1496 LambdaScopeInfo *LSI) {
1497 // Collect information from the lambda scope.
1498 SmallVector<LambdaCapture, 4> Captures;
1499 SmallVector<Expr *, 4> CaptureInits;
1500 SourceLocation CaptureDefaultLoc = LSI->CaptureDefaultLoc;
1501 LambdaCaptureDefault CaptureDefault =
1502 mapImplicitCaptureStyle(LSI->ImpCaptureStyle);
1503 CXXRecordDecl *Class;
1504 CXXMethodDecl *CallOperator;
1505 SourceRange IntroducerRange;
1506 bool ExplicitParams;
1507 bool ExplicitResultType;
1508 bool LambdaExprNeedsCleanups;
1509 bool ContainsUnexpandedParameterPack;
1510 SmallVector<VarDecl *, 4> ArrayIndexVars;
1511 SmallVector<unsigned, 4> ArrayIndexStarts;
1513 CallOperator = LSI->CallOperator;
1514 Class = LSI->Lambda;
1515 IntroducerRange = LSI->IntroducerRange;
1516 ExplicitParams = LSI->ExplicitParams;
1517 ExplicitResultType = !LSI->HasImplicitReturnType;
1518 LambdaExprNeedsCleanups = LSI->ExprNeedsCleanups;
1519 ContainsUnexpandedParameterPack = LSI->ContainsUnexpandedParameterPack;
1521 CallOperator->setLexicalDeclContext(Class);
1522 Decl *TemplateOrNonTemplateCallOperatorDecl =
1523 CallOperator->getDescribedFunctionTemplate()
1524 ? CallOperator->getDescribedFunctionTemplate()
1525 : cast<Decl>(CallOperator);
1527 TemplateOrNonTemplateCallOperatorDecl->setLexicalDeclContext(Class);
1528 Class->addDecl(TemplateOrNonTemplateCallOperatorDecl);
1530 PopExpressionEvaluationContext();
1532 // Translate captures.
1533 auto CurField = Class->field_begin();
1534 for (unsigned I = 0, N = LSI->Captures.size(); I != N; ++I, ++CurField) {
1535 LambdaScopeInfo::Capture From = LSI->Captures[I];
1536 assert(!From.isBlockCapture() && "Cannot capture __block variables");
1537 bool IsImplicit = I >= LSI->NumExplicitCaptures;
1539 // Handle 'this' capture.
1540 if (From.isThisCapture()) {
1542 LambdaCapture(From.getLocation(), IsImplicit, LCK_This));
1543 CaptureInits.push_back(new (Context) CXXThisExpr(From.getLocation(),
1544 getCurrentThisType(),
1545 /*isImplicit=*/true));
1546 ArrayIndexStarts.push_back(ArrayIndexVars.size());
1549 if (From.isVLATypeCapture()) {
1551 LambdaCapture(From.getLocation(), IsImplicit, LCK_VLAType));
1552 CaptureInits.push_back(nullptr);
1553 ArrayIndexStarts.push_back(ArrayIndexVars.size());
1557 VarDecl *Var = From.getVariable();
1558 LambdaCaptureKind Kind = From.isCopyCapture() ? LCK_ByCopy : LCK_ByRef;
1559 Captures.push_back(LambdaCapture(From.getLocation(), IsImplicit, Kind,
1560 Var, From.getEllipsisLoc()));
1561 Expr *Init = From.getInitExpr();
1563 auto InitResult = performLambdaVarCaptureInitialization(
1564 *this, From, *CurField, ArrayIndexVars, ArrayIndexStarts);
1565 if (InitResult.isInvalid())
1567 Init = InitResult.get();
1569 ArrayIndexStarts.push_back(ArrayIndexVars.size());
1571 CaptureInits.push_back(Init);
1574 // C++11 [expr.prim.lambda]p6:
1575 // The closure type for a lambda-expression with no lambda-capture
1576 // has a public non-virtual non-explicit const conversion function
1577 // to pointer to function having the same parameter and return
1578 // types as the closure type's function call operator.
1579 if (Captures.empty() && CaptureDefault == LCD_None)
1580 addFunctionPointerConversion(*this, IntroducerRange, Class,
1584 // The closure type for a lambda-expression has a public non-virtual
1585 // non-explicit const conversion function to a block pointer having the
1586 // same parameter and return types as the closure type's function call
1588 // FIXME: Fix generic lambda to block conversions.
1589 if (getLangOpts().Blocks && getLangOpts().ObjC1 &&
1590 !Class->isGenericLambda())
1591 addBlockPointerConversion(*this, IntroducerRange, Class, CallOperator);
1593 // Finalize the lambda class.
1594 SmallVector<Decl*, 4> Fields(Class->fields());
1595 ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
1596 SourceLocation(), nullptr);
1597 CheckCompletedCXXClass(Class);
1600 if (LambdaExprNeedsCleanups)
1601 ExprNeedsCleanups = true;
1603 LambdaExpr *Lambda = LambdaExpr::Create(Context, Class, IntroducerRange,
1604 CaptureDefault, CaptureDefaultLoc,
1606 ExplicitParams, ExplicitResultType,
1607 CaptureInits, ArrayIndexVars,
1608 ArrayIndexStarts, EndLoc,
1609 ContainsUnexpandedParameterPack);
1611 if (!CurContext->isDependentContext()) {
1612 switch (ExprEvalContexts.back().Context) {
1613 // C++11 [expr.prim.lambda]p2:
1614 // A lambda-expression shall not appear in an unevaluated operand
1617 case UnevaluatedAbstract:
1618 // C++1y [expr.const]p2:
1619 // A conditional-expression e is a core constant expression unless the
1620 // evaluation of e, following the rules of the abstract machine, would
1621 // evaluate [...] a lambda-expression.
1623 // This is technically incorrect, there are some constant evaluated contexts
1624 // where this should be allowed. We should probably fix this when DR1607 is
1625 // ratified, it lays out the exact set of conditions where we shouldn't
1626 // allow a lambda-expression.
1627 case ConstantEvaluated:
1628 // We don't actually diagnose this case immediately, because we
1629 // could be within a context where we might find out later that
1630 // the expression is potentially evaluated (e.g., for typeid).
1631 ExprEvalContexts.back().Lambdas.push_back(Lambda);
1634 case PotentiallyEvaluated:
1635 case PotentiallyEvaluatedIfUsed:
1640 return MaybeBindToTemporary(Lambda);
1643 ExprResult Sema::BuildBlockForLambdaConversion(SourceLocation CurrentLocation,
1644 SourceLocation ConvLocation,
1645 CXXConversionDecl *Conv,
1647 // Make sure that the lambda call operator is marked used.
1648 CXXRecordDecl *Lambda = Conv->getParent();
1649 CXXMethodDecl *CallOperator
1650 = cast<CXXMethodDecl>(
1652 Context.DeclarationNames.getCXXOperatorName(OO_Call)).front());
1653 CallOperator->setReferenced();
1654 CallOperator->markUsed(Context);
1656 ExprResult Init = PerformCopyInitialization(
1657 InitializedEntity::InitializeBlock(ConvLocation,
1660 CurrentLocation, Src);
1661 if (!Init.isInvalid())
1662 Init = ActOnFinishFullExpr(Init.get());
1664 if (Init.isInvalid())
1667 // Create the new block to be returned.
1668 BlockDecl *Block = BlockDecl::Create(Context, CurContext, ConvLocation);
1670 // Set the type information.
1671 Block->setSignatureAsWritten(CallOperator->getTypeSourceInfo());
1672 Block->setIsVariadic(CallOperator->isVariadic());
1673 Block->setBlockMissingReturnType(false);
1676 SmallVector<ParmVarDecl *, 4> BlockParams;
1677 for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I) {
1678 ParmVarDecl *From = CallOperator->getParamDecl(I);
1679 BlockParams.push_back(ParmVarDecl::Create(Context, Block,
1680 From->getLocStart(),
1681 From->getLocation(),
1682 From->getIdentifier(),
1684 From->getTypeSourceInfo(),
1685 From->getStorageClass(),
1686 /*DefaultArg=*/nullptr));
1688 Block->setParams(BlockParams);
1690 Block->setIsConversionFromLambda(true);
1692 // Add capture. The capture uses a fake variable, which doesn't correspond
1693 // to any actual memory location. However, the initializer copy-initializes
1694 // the lambda object.
1695 TypeSourceInfo *CapVarTSI =
1696 Context.getTrivialTypeSourceInfo(Src->getType());
1697 VarDecl *CapVar = VarDecl::Create(Context, Block, ConvLocation,
1698 ConvLocation, nullptr,
1699 Src->getType(), CapVarTSI,
1701 BlockDecl::Capture Capture(/*Variable=*/CapVar, /*ByRef=*/false,
1702 /*Nested=*/false, /*Copy=*/Init.get());
1703 Block->setCaptures(Context, &Capture, &Capture + 1,
1704 /*CapturesCXXThis=*/false);
1706 // Add a fake function body to the block. IR generation is responsible
1707 // for filling in the actual body, which cannot be expressed as an AST.
1708 Block->setBody(new (Context) CompoundStmt(ConvLocation));
1710 // Create the block literal expression.
1711 Expr *BuildBlock = new (Context) BlockExpr(Block, Conv->getConversionType());
1712 ExprCleanupObjects.push_back(Block);
1713 ExprNeedsCleanups = true;