1 //===--- SemaLambda.cpp - Semantic Analysis for C++11 Lambdas -------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements semantic analysis for C++ lambda expressions.
10 //
11 //===----------------------------------------------------------------------===//
12 #include "clang/Sema/DeclSpec.h"
13 #include "TypeLocBuilder.h"
14 #include "clang/AST/ASTLambda.h"
15 #include "clang/AST/ExprCXX.h"
16 #include "clang/Basic/TargetInfo.h"
17 #include "clang/Sema/Initialization.h"
18 #include "clang/Sema/Lookup.h"
19 #include "clang/Sema/Scope.h"
20 #include "clang/Sema/ScopeInfo.h"
21 #include "clang/Sema/SemaInternal.h"
22 #include "clang/Sema/SemaLambda.h"
23 #include "llvm/ADT/STLExtras.h"
24 using namespace clang;
25 using namespace sema;
26
27 /// Examines the FunctionScopeInfo stack to determine the nearest
28 /// enclosing lambda (to the current lambda) that is 'capture-ready' for
29 /// the variable referenced in the current lambda (i.e. \p VarToCapture).
30 /// If successful, returns the index into Sema's FunctionScopeInfo stack
31 /// of the capture-ready lambda's LambdaScopeInfo.
32 ///
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'.
39 ///
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'.
46 ///
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
50 /// capture.
51 ///
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'.
56 ///
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.
61
62 static inline Optional<unsigned>
getStackIndexOfNearestEnclosingCaptureReadyLambda(ArrayRef<const clang::sema::FunctionScopeInfo * > FunctionScopes,VarDecl * VarToCapture)63 getStackIndexOfNearestEnclosingCaptureReadyLambda(
64 ArrayRef<const clang::sema::FunctionScopeInfo *> FunctionScopes,
65 VarDecl *VarToCapture) {
66 // Label failure to capture.
67 const Optional<unsigned> NoLambdaIsCaptureReady;
68
69 // Ignore all inner captured regions.
70 unsigned CurScopeIndex = FunctionScopes.size() - 1;
71 while (CurScopeIndex > 0 && isa<clang::sema::CapturedRegionScopeInfo>(
72 FunctionScopes[CurScopeIndex]))
73 --CurScopeIndex;
74 assert(
75 isa<clang::sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex]) &&
76 "The function on the top of sema's function-info stack must be a lambda");
77
78 // If VarToCapture is null, we are attempting to capture 'this'.
79 const bool IsCapturingThis = !VarToCapture;
80 const bool IsCapturingVariable = !IsCapturingThis;
81
82 // Start with the current lambda at the top of the stack (highest index).
83 DeclContext *EnclosingDC =
84 cast<sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex])->CallOperator;
85
86 do {
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
91 // variable.
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
95 // variable.
96 if (IsCapturingVariable &&
97 VarToCapture->getDeclContext()->Equals(EnclosingDC))
98 return NoLambdaIsCaptureReady;
99
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.
104 // For e.g.
105 // const int x = 10;
106 // [=](auto a) { #1
107 // [](auto b) { #2 <-- an intervening lambda that can never capture 'x'
108 // [=](auto c) { #3
109 // f(x, c); <-- can not lead to x's speculative capture by #1 or #2
110 // }; }; };
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;
121 }
122 EnclosingDC = getLambdaAwareParentOfDeclContext(EnclosingDC);
123
124 assert(CurScopeIndex);
125 --CurScopeIndex;
126 } while (!EnclosingDC->isTranslationUnit() &&
127 EnclosingDC->isDependentContext() &&
128 isLambdaCallOperator(EnclosingDC));
129
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;
136 }
137
138 /// Examines the FunctionScopeInfo stack to determine the nearest
139 /// enclosing lambda (to the current lambda) that is 'capture-capable' for
140 /// the variable referenced in the current lambda (i.e. \p VarToCapture).
141 /// If successful, returns the index into Sema's FunctionScopeInfo stack
142 /// of the capture-capable lambda's LambdaScopeInfo.
143 ///
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')
160 ///
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.
164 ///
165 /// \param VarToCapture - the variable to capture. If NULL, capture 'this'.
166 ///
167 ///
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.
172
getStackIndexOfNearestEnclosingCaptureCapableLambda(ArrayRef<const sema::FunctionScopeInfo * > FunctionScopes,VarDecl * VarToCapture,Sema & S)173 Optional<unsigned> clang::getStackIndexOfNearestEnclosingCaptureCapableLambda(
174 ArrayRef<const sema::FunctionScopeInfo *> FunctionScopes,
175 VarDecl *VarToCapture, Sema &S) {
176
177 const Optional<unsigned> NoLambdaIsCaptureCapable;
178
179 const Optional<unsigned> OptionalStackIndex =
180 getStackIndexOfNearestEnclosingCaptureReadyLambda(FunctionScopes,
181 VarToCapture);
182 if (!OptionalStackIndex)
183 return NoLambdaIsCaptureCapable;
184
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");
190
191 const sema::LambdaScopeInfo *const CaptureReadyLambdaLSI =
192 cast<sema::LambdaScopeInfo>(FunctionScopes[IndexOfCaptureReadyLambda]);
193
194 // If VarToCapture is null, we are attempting to capture 'this'
195 const bool IsCapturingThis = !VarToCapture;
196 const bool IsCapturingVariable = !IsCapturingThis;
197
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;
212 } else {
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
215 // 'this'.
216 const bool CanCaptureThis =
217 !S.CheckCXXThisCapture(
218 CaptureReadyLambdaLSI->PotentialThisCaptureLocation,
219 /*Explicit*/ false, /*BuildAndDiagnose*/ false,
220 &IndexOfCaptureReadyLambda);
221 if (!CanCaptureThis)
222 return NoLambdaIsCaptureCapable;
223 }
224 return IndexOfCaptureReadyLambda;
225 }
226
227 static inline TemplateParameterList *
getGenericLambdaTemplateParameterList(LambdaScopeInfo * LSI,Sema & SemaRef)228 getGenericLambdaTemplateParameterList(LambdaScopeInfo *LSI, Sema &SemaRef) {
229 if (!LSI->GLTemplateParameterList && !LSI->TemplateParams.empty()) {
230 LSI->GLTemplateParameterList = TemplateParameterList::Create(
231 SemaRef.Context,
232 /*Template kw loc*/ SourceLocation(),
233 /*L angle loc*/ LSI->ExplicitTemplateParamsRange.getBegin(),
234 LSI->TemplateParams,
235 /*R angle loc*/LSI->ExplicitTemplateParamsRange.getEnd(),
236 nullptr);
237 }
238 return LSI->GLTemplateParameterList;
239 }
240
createLambdaClosureType(SourceRange IntroducerRange,TypeSourceInfo * Info,bool KnownDependent,LambdaCaptureDefault CaptureDefault)241 CXXRecordDecl *Sema::createLambdaClosureType(SourceRange IntroducerRange,
242 TypeSourceInfo *Info,
243 bool KnownDependent,
244 LambdaCaptureDefault CaptureDefault) {
245 DeclContext *DC = CurContext;
246 while (!(DC->isFunctionOrMethod() || DC->isRecord() || DC->isFileContext()))
247 DC = DC->getParent();
248 bool IsGenericLambda = getGenericLambdaTemplateParameterList(getCurLambda(),
249 *this);
250 // Start constructing the lambda class.
251 CXXRecordDecl *Class = CXXRecordDecl::CreateLambda(Context, DC, Info,
252 IntroducerRange.getBegin(),
253 KnownDependent,
254 IsGenericLambda,
255 CaptureDefault);
256 DC->addDecl(Class);
257
258 return Class;
259 }
260
261 /// Determine whether the given context is or is enclosed in an inline
262 /// function.
isInInlineFunction(const DeclContext * DC)263 static bool isInInlineFunction(const DeclContext *DC) {
264 while (!DC->isFileContext()) {
265 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(DC))
266 if (FD->isInlined())
267 return true;
268
269 DC = DC->getLexicalParent();
270 }
271
272 return false;
273 }
274
275 std::tuple<MangleNumberingContext *, Decl *>
getCurrentMangleNumberContext(const DeclContext * DC)276 Sema::getCurrentMangleNumberContext(const DeclContext *DC) {
277 // Compute the context for allocating mangling numbers in the current
278 // expression, if the ABI requires them.
279 Decl *ManglingContextDecl = ExprEvalContexts.back().ManglingContextDecl;
280
281 enum ContextKind {
282 Normal,
283 DefaultArgument,
284 DataMember,
285 StaticDataMember,
286 InlineVariable,
287 VariableTemplate
288 } Kind = Normal;
289
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 (Var->getMostRecentDecl()->isInline())
303 Kind = InlineVariable;
304 else if (Var->getDescribedVarTemplate())
305 Kind = VariableTemplate;
306 else if (auto *VTS = dyn_cast<VarTemplateSpecializationDecl>(Var)) {
307 if (!VTS->isExplicitSpecialization())
308 Kind = VariableTemplate;
309 }
310 } else if (isa<FieldDecl>(ManglingContextDecl)) {
311 Kind = DataMember;
312 }
313 }
314
315 // Itanium ABI [5.1.7]:
316 // In the following contexts [...] the one-definition rule requires closure
317 // types in different translation units to "correspond":
318 bool IsInNonspecializedTemplate =
319 inTemplateInstantiation() || CurContext->isDependentContext();
320 switch (Kind) {
321 case Normal: {
322 // -- the bodies of non-exported nonspecialized template functions
323 // -- the bodies of inline functions
324 if ((IsInNonspecializedTemplate &&
325 !(ManglingContextDecl && isa<ParmVarDecl>(ManglingContextDecl))) ||
326 isInInlineFunction(CurContext)) {
327 while (auto *CD = dyn_cast<CapturedDecl>(DC))
328 DC = CD->getParent();
329 return std::make_tuple(&Context.getManglingNumberContext(DC), nullptr);
330 }
331
332 return std::make_tuple(nullptr, nullptr);
333 }
334
335 case StaticDataMember:
336 // -- the initializers of nonspecialized static members of template classes
337 if (!IsInNonspecializedTemplate)
338 return std::make_tuple(nullptr, ManglingContextDecl);
339 // Fall through to get the current context.
340 LLVM_FALLTHROUGH;
341
342 case DataMember:
343 // -- the in-class initializers of class members
344 case DefaultArgument:
345 // -- default arguments appearing in class definitions
346 case InlineVariable:
347 // -- the initializers of inline variables
348 case VariableTemplate:
349 // -- the initializers of templated variables
350 return std::make_tuple(
351 &Context.getManglingNumberContext(ASTContext::NeedExtraManglingDecl,
352 ManglingContextDecl),
353 ManglingContextDecl);
354 }
355
356 llvm_unreachable("unexpected context");
357 }
358
startLambdaDefinition(CXXRecordDecl * Class,SourceRange IntroducerRange,TypeSourceInfo * MethodTypeInfo,SourceLocation EndLoc,ArrayRef<ParmVarDecl * > Params,ConstexprSpecKind ConstexprKind,Expr * TrailingRequiresClause)359 CXXMethodDecl *Sema::startLambdaDefinition(CXXRecordDecl *Class,
360 SourceRange IntroducerRange,
361 TypeSourceInfo *MethodTypeInfo,
362 SourceLocation EndLoc,
363 ArrayRef<ParmVarDecl *> Params,
364 ConstexprSpecKind ConstexprKind,
365 Expr *TrailingRequiresClause) {
366 QualType MethodType = MethodTypeInfo->getType();
367 TemplateParameterList *TemplateParams =
368 getGenericLambdaTemplateParameterList(getCurLambda(), *this);
369 // If a lambda appears in a dependent context or is a generic lambda (has
370 // template parameters) and has an 'auto' return type, deduce it to a
371 // dependent type.
372 if (Class->isDependentContext() || TemplateParams) {
373 const FunctionProtoType *FPT = MethodType->castAs<FunctionProtoType>();
374 QualType Result = FPT->getReturnType();
375 if (Result->isUndeducedType()) {
376 Result = SubstAutoType(Result, Context.DependentTy);
377 MethodType = Context.getFunctionType(Result, FPT->getParamTypes(),
378 FPT->getExtProtoInfo());
379 }
380 }
381
382 // C++11 [expr.prim.lambda]p5:
383 // The closure type for a lambda-expression has a public inline function
384 // call operator (13.5.4) whose parameters and return type are described by
385 // the lambda-expression's parameter-declaration-clause and
386 // trailing-return-type respectively.
387 DeclarationName MethodName
388 = Context.DeclarationNames.getCXXOperatorName(OO_Call);
389 DeclarationNameLoc MethodNameLoc;
390 MethodNameLoc.CXXOperatorName.BeginOpNameLoc
391 = IntroducerRange.getBegin().getRawEncoding();
392 MethodNameLoc.CXXOperatorName.EndOpNameLoc
393 = IntroducerRange.getEnd().getRawEncoding();
394 CXXMethodDecl *Method = CXXMethodDecl::Create(
395 Context, Class, EndLoc,
396 DeclarationNameInfo(MethodName, IntroducerRange.getBegin(),
397 MethodNameLoc),
398 MethodType, MethodTypeInfo, SC_None,
399 /*isInline=*/true, ConstexprKind, EndLoc, TrailingRequiresClause);
400 Method->setAccess(AS_public);
401 if (!TemplateParams)
402 Class->addDecl(Method);
403
404 // Temporarily set the lexical declaration context to the current
405 // context, so that the Scope stack matches the lexical nesting.
406 Method->setLexicalDeclContext(CurContext);
407 // Create a function template if we have a template parameter list
408 FunctionTemplateDecl *const TemplateMethod = TemplateParams ?
409 FunctionTemplateDecl::Create(Context, Class,
410 Method->getLocation(), MethodName,
411 TemplateParams,
412 Method) : nullptr;
413 if (TemplateMethod) {
414 TemplateMethod->setAccess(AS_public);
415 Method->setDescribedFunctionTemplate(TemplateMethod);
416 Class->addDecl(TemplateMethod);
417 TemplateMethod->setLexicalDeclContext(CurContext);
418 }
419
420 // Add parameters.
421 if (!Params.empty()) {
422 Method->setParams(Params);
423 CheckParmsForFunctionDef(Params,
424 /*CheckParameterNames=*/false);
425
426 for (auto P : Method->parameters())
427 P->setOwningFunction(Method);
428 }
429
430 return Method;
431 }
432
handleLambdaNumbering(CXXRecordDecl * Class,CXXMethodDecl * Method,Optional<std::tuple<unsigned,bool,Decl * >> Mangling)433 void Sema::handleLambdaNumbering(
434 CXXRecordDecl *Class, CXXMethodDecl *Method,
435 Optional<std::tuple<unsigned, bool, Decl *>> Mangling) {
436 if (Mangling) {
437 unsigned ManglingNumber;
438 bool HasKnownInternalLinkage;
439 Decl *ManglingContextDecl;
440 std::tie(ManglingNumber, HasKnownInternalLinkage, ManglingContextDecl) =
441 Mangling.getValue();
442 Class->setLambdaMangling(ManglingNumber, ManglingContextDecl,
443 HasKnownInternalLinkage);
444 return;
445 }
446
447 auto getMangleNumberingContext =
448 [this](CXXRecordDecl *Class,
449 Decl *ManglingContextDecl) -> MangleNumberingContext * {
450 // Get mangle numbering context if there's any extra decl context.
451 if (ManglingContextDecl)
452 return &Context.getManglingNumberContext(
453 ASTContext::NeedExtraManglingDecl, ManglingContextDecl);
454 // Otherwise, from that lambda's decl context.
455 auto DC = Class->getDeclContext();
456 while (auto *CD = dyn_cast<CapturedDecl>(DC))
457 DC = CD->getParent();
458 return &Context.getManglingNumberContext(DC);
459 };
460
461 MangleNumberingContext *MCtx;
462 Decl *ManglingContextDecl;
463 std::tie(MCtx, ManglingContextDecl) =
464 getCurrentMangleNumberContext(Class->getDeclContext());
465 bool HasKnownInternalLinkage = false;
466 if (!MCtx && getLangOpts().CUDA) {
467 // Force lambda numbering in CUDA/HIP as we need to name lambdas following
468 // ODR. Both device- and host-compilation need to have a consistent naming
469 // on kernel functions. As lambdas are potential part of these `__global__`
470 // function names, they needs numbering following ODR.
471 MCtx = getMangleNumberingContext(Class, ManglingContextDecl);
472 assert(MCtx && "Retrieving mangle numbering context failed!");
473 HasKnownInternalLinkage = true;
474 }
475 if (MCtx) {
476 unsigned ManglingNumber = MCtx->getManglingNumber(Method);
477 Class->setLambdaMangling(ManglingNumber, ManglingContextDecl,
478 HasKnownInternalLinkage);
479 }
480 }
481
buildLambdaScope(LambdaScopeInfo * LSI,CXXMethodDecl * CallOperator,SourceRange IntroducerRange,LambdaCaptureDefault CaptureDefault,SourceLocation CaptureDefaultLoc,bool ExplicitParams,bool ExplicitResultType,bool Mutable)482 void Sema::buildLambdaScope(LambdaScopeInfo *LSI,
483 CXXMethodDecl *CallOperator,
484 SourceRange IntroducerRange,
485 LambdaCaptureDefault CaptureDefault,
486 SourceLocation CaptureDefaultLoc,
487 bool ExplicitParams,
488 bool ExplicitResultType,
489 bool Mutable) {
490 LSI->CallOperator = CallOperator;
491 CXXRecordDecl *LambdaClass = CallOperator->getParent();
492 LSI->Lambda = LambdaClass;
493 if (CaptureDefault == LCD_ByCopy)
494 LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByval;
495 else if (CaptureDefault == LCD_ByRef)
496 LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByref;
497 LSI->CaptureDefaultLoc = CaptureDefaultLoc;
498 LSI->IntroducerRange = IntroducerRange;
499 LSI->ExplicitParams = ExplicitParams;
500 LSI->Mutable = Mutable;
501
502 if (ExplicitResultType) {
503 LSI->ReturnType = CallOperator->getReturnType();
504
505 if (!LSI->ReturnType->isDependentType() &&
506 !LSI->ReturnType->isVoidType()) {
507 if (RequireCompleteType(CallOperator->getBeginLoc(), LSI->ReturnType,
508 diag::err_lambda_incomplete_result)) {
509 // Do nothing.
510 }
511 }
512 } else {
513 LSI->HasImplicitReturnType = true;
514 }
515 }
516
finishLambdaExplicitCaptures(LambdaScopeInfo * LSI)517 void Sema::finishLambdaExplicitCaptures(LambdaScopeInfo *LSI) {
518 LSI->finishedExplicitCaptures();
519 }
520
ActOnLambdaExplicitTemplateParameterList(SourceLocation LAngleLoc,ArrayRef<NamedDecl * > TParams,SourceLocation RAngleLoc)521 void Sema::ActOnLambdaExplicitTemplateParameterList(SourceLocation LAngleLoc,
522 ArrayRef<NamedDecl *> TParams,
523 SourceLocation RAngleLoc) {
524 LambdaScopeInfo *LSI = getCurLambda();
525 assert(LSI && "Expected a lambda scope");
526 assert(LSI->NumExplicitTemplateParams == 0 &&
527 "Already acted on explicit template parameters");
528 assert(LSI->TemplateParams.empty() &&
529 "Explicit template parameters should come "
530 "before invented (auto) ones");
531 assert(!TParams.empty() &&
532 "No template parameters to act on");
533 LSI->TemplateParams.append(TParams.begin(), TParams.end());
534 LSI->NumExplicitTemplateParams = TParams.size();
535 LSI->ExplicitTemplateParamsRange = {LAngleLoc, RAngleLoc};
536 }
537
addLambdaParameters(ArrayRef<LambdaIntroducer::LambdaCapture> Captures,CXXMethodDecl * CallOperator,Scope * CurScope)538 void Sema::addLambdaParameters(
539 ArrayRef<LambdaIntroducer::LambdaCapture> Captures,
540 CXXMethodDecl *CallOperator, Scope *CurScope) {
541 // Introduce our parameters into the function scope
542 for (unsigned p = 0, NumParams = CallOperator->getNumParams();
543 p < NumParams; ++p) {
544 ParmVarDecl *Param = CallOperator->getParamDecl(p);
545
546 // If this has an identifier, add it to the scope stack.
547 if (CurScope && Param->getIdentifier()) {
548 bool Error = false;
549 // Resolution of CWG 2211 in C++17 renders shadowing ill-formed, but we
550 // retroactively apply it.
551 for (const auto &Capture : Captures) {
552 if (Capture.Id == Param->getIdentifier()) {
553 Error = true;
554 Diag(Param->getLocation(), diag::err_parameter_shadow_capture);
555 Diag(Capture.Loc, diag::note_var_explicitly_captured_here)
556 << Capture.Id << true;
557 }
558 }
559 if (!Error)
560 CheckShadow(CurScope, Param);
561
562 PushOnScopeChains(Param, CurScope);
563 }
564 }
565 }
566
567 /// If this expression is an enumerator-like expression of some type
568 /// T, return the type T; otherwise, return null.
569 ///
570 /// Pointer comparisons on the result here should always work because
571 /// it's derived from either the parent of an EnumConstantDecl
572 /// (i.e. the definition) or the declaration returned by
573 /// EnumType::getDecl() (i.e. the definition).
findEnumForBlockReturn(Expr * E)574 static EnumDecl *findEnumForBlockReturn(Expr *E) {
575 // An expression is an enumerator-like expression of type T if,
576 // ignoring parens and parens-like expressions:
577 E = E->IgnoreParens();
578
579 // - it is an enumerator whose enum type is T or
580 if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
581 if (EnumConstantDecl *D
582 = dyn_cast<EnumConstantDecl>(DRE->getDecl())) {
583 return cast<EnumDecl>(D->getDeclContext());
584 }
585 return nullptr;
586 }
587
588 // - it is a comma expression whose RHS is an enumerator-like
589 // expression of type T or
590 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
591 if (BO->getOpcode() == BO_Comma)
592 return findEnumForBlockReturn(BO->getRHS());
593 return nullptr;
594 }
595
596 // - it is a statement-expression whose value expression is an
597 // enumerator-like expression of type T or
598 if (StmtExpr *SE = dyn_cast<StmtExpr>(E)) {
599 if (Expr *last = dyn_cast_or_null<Expr>(SE->getSubStmt()->body_back()))
600 return findEnumForBlockReturn(last);
601 return nullptr;
602 }
603
604 // - it is a ternary conditional operator (not the GNU ?:
605 // extension) whose second and third operands are
606 // enumerator-like expressions of type T or
607 if (ConditionalOperator *CO = dyn_cast<ConditionalOperator>(E)) {
608 if (EnumDecl *ED = findEnumForBlockReturn(CO->getTrueExpr()))
609 if (ED == findEnumForBlockReturn(CO->getFalseExpr()))
610 return ED;
611 return nullptr;
612 }
613
614 // (implicitly:)
615 // - it is an implicit integral conversion applied to an
616 // enumerator-like expression of type T or
617 if (ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(E)) {
618 // We can sometimes see integral conversions in valid
619 // enumerator-like expressions.
620 if (ICE->getCastKind() == CK_IntegralCast)
621 return findEnumForBlockReturn(ICE->getSubExpr());
622
623 // Otherwise, just rely on the type.
624 }
625
626 // - it is an expression of that formal enum type.
627 if (const EnumType *ET = E->getType()->getAs<EnumType>()) {
628 return ET->getDecl();
629 }
630
631 // Otherwise, nope.
632 return nullptr;
633 }
634
635 /// Attempt to find a type T for which the returned expression of the
636 /// given statement is an enumerator-like expression of that type.
findEnumForBlockReturn(ReturnStmt * ret)637 static EnumDecl *findEnumForBlockReturn(ReturnStmt *ret) {
638 if (Expr *retValue = ret->getRetValue())
639 return findEnumForBlockReturn(retValue);
640 return nullptr;
641 }
642
643 /// Attempt to find a common type T for which all of the returned
644 /// expressions in a block are enumerator-like expressions of that
645 /// type.
findCommonEnumForBlockReturns(ArrayRef<ReturnStmt * > returns)646 static EnumDecl *findCommonEnumForBlockReturns(ArrayRef<ReturnStmt*> returns) {
647 ArrayRef<ReturnStmt*>::iterator i = returns.begin(), e = returns.end();
648
649 // Try to find one for the first return.
650 EnumDecl *ED = findEnumForBlockReturn(*i);
651 if (!ED) return nullptr;
652
653 // Check that the rest of the returns have the same enum.
654 for (++i; i != e; ++i) {
655 if (findEnumForBlockReturn(*i) != ED)
656 return nullptr;
657 }
658
659 // Never infer an anonymous enum type.
660 if (!ED->hasNameForLinkage()) return nullptr;
661
662 return ED;
663 }
664
665 /// Adjust the given return statements so that they formally return
666 /// the given type. It should require, at most, an IntegralCast.
adjustBlockReturnsToEnum(Sema & S,ArrayRef<ReturnStmt * > returns,QualType returnType)667 static void adjustBlockReturnsToEnum(Sema &S, ArrayRef<ReturnStmt*> returns,
668 QualType returnType) {
669 for (ArrayRef<ReturnStmt*>::iterator
670 i = returns.begin(), e = returns.end(); i != e; ++i) {
671 ReturnStmt *ret = *i;
672 Expr *retValue = ret->getRetValue();
673 if (S.Context.hasSameType(retValue->getType(), returnType))
674 continue;
675
676 // Right now we only support integral fixup casts.
677 assert(returnType->isIntegralOrUnscopedEnumerationType());
678 assert(retValue->getType()->isIntegralOrUnscopedEnumerationType());
679
680 ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(retValue);
681
682 Expr *E = (cleanups ? cleanups->getSubExpr() : retValue);
683 E = ImplicitCastExpr::Create(S.Context, returnType, CK_IntegralCast,
684 E, /*base path*/ nullptr, VK_RValue);
685 if (cleanups) {
686 cleanups->setSubExpr(E);
687 } else {
688 ret->setRetValue(E);
689 }
690 }
691 }
692
deduceClosureReturnType(CapturingScopeInfo & CSI)693 void Sema::deduceClosureReturnType(CapturingScopeInfo &CSI) {
694 assert(CSI.HasImplicitReturnType);
695 // If it was ever a placeholder, it had to been deduced to DependentTy.
696 assert(CSI.ReturnType.isNull() || !CSI.ReturnType->isUndeducedType());
697 assert((!isa<LambdaScopeInfo>(CSI) || !getLangOpts().CPlusPlus14) &&
698 "lambda expressions use auto deduction in C++14 onwards");
699
700 // C++ core issue 975:
701 // If a lambda-expression does not include a trailing-return-type,
702 // it is as if the trailing-return-type denotes the following type:
703 // - if there are no return statements in the compound-statement,
704 // or all return statements return either an expression of type
705 // void or no expression or braced-init-list, the type void;
706 // - otherwise, if all return statements return an expression
707 // and the types of the returned expressions after
708 // lvalue-to-rvalue conversion (4.1 [conv.lval]),
709 // array-to-pointer conversion (4.2 [conv.array]), and
710 // function-to-pointer conversion (4.3 [conv.func]) are the
711 // same, that common type;
712 // - otherwise, the program is ill-formed.
713 //
714 // C++ core issue 1048 additionally removes top-level cv-qualifiers
715 // from the types of returned expressions to match the C++14 auto
716 // deduction rules.
717 //
718 // In addition, in blocks in non-C++ modes, if all of the return
719 // statements are enumerator-like expressions of some type T, where
720 // T has a name for linkage, then we infer the return type of the
721 // block to be that type.
722
723 // First case: no return statements, implicit void return type.
724 ASTContext &Ctx = getASTContext();
725 if (CSI.Returns.empty()) {
726 // It's possible there were simply no /valid/ return statements.
727 // In this case, the first one we found may have at least given us a type.
728 if (CSI.ReturnType.isNull())
729 CSI.ReturnType = Ctx.VoidTy;
730 return;
731 }
732
733 // Second case: at least one return statement has dependent type.
734 // Delay type checking until instantiation.
735 assert(!CSI.ReturnType.isNull() && "We should have a tentative return type.");
736 if (CSI.ReturnType->isDependentType())
737 return;
738
739 // Try to apply the enum-fuzz rule.
740 if (!getLangOpts().CPlusPlus) {
741 assert(isa<BlockScopeInfo>(CSI));
742 const EnumDecl *ED = findCommonEnumForBlockReturns(CSI.Returns);
743 if (ED) {
744 CSI.ReturnType = Context.getTypeDeclType(ED);
745 adjustBlockReturnsToEnum(*this, CSI.Returns, CSI.ReturnType);
746 return;
747 }
748 }
749
750 // Third case: only one return statement. Don't bother doing extra work!
751 if (CSI.Returns.size() == 1)
752 return;
753
754 // General case: many return statements.
755 // Check that they all have compatible return types.
756
757 // We require the return types to strictly match here.
758 // Note that we've already done the required promotions as part of
759 // processing the return statement.
760 for (const ReturnStmt *RS : CSI.Returns) {
761 const Expr *RetE = RS->getRetValue();
762
763 QualType ReturnType =
764 (RetE ? RetE->getType() : Context.VoidTy).getUnqualifiedType();
765 if (Context.getCanonicalFunctionResultType(ReturnType) ==
766 Context.getCanonicalFunctionResultType(CSI.ReturnType)) {
767 // Use the return type with the strictest possible nullability annotation.
768 auto RetTyNullability = ReturnType->getNullability(Ctx);
769 auto BlockNullability = CSI.ReturnType->getNullability(Ctx);
770 if (BlockNullability &&
771 (!RetTyNullability ||
772 hasWeakerNullability(*RetTyNullability, *BlockNullability)))
773 CSI.ReturnType = ReturnType;
774 continue;
775 }
776
777 // FIXME: This is a poor diagnostic for ReturnStmts without expressions.
778 // TODO: It's possible that the *first* return is the divergent one.
779 Diag(RS->getBeginLoc(),
780 diag::err_typecheck_missing_return_type_incompatible)
781 << ReturnType << CSI.ReturnType << isa<LambdaScopeInfo>(CSI);
782 // Continue iterating so that we keep emitting diagnostics.
783 }
784 }
785
buildLambdaInitCaptureInitialization(SourceLocation Loc,bool ByRef,SourceLocation EllipsisLoc,Optional<unsigned> NumExpansions,IdentifierInfo * Id,bool IsDirectInit,Expr * & Init)786 QualType Sema::buildLambdaInitCaptureInitialization(
787 SourceLocation Loc, bool ByRef, SourceLocation EllipsisLoc,
788 Optional<unsigned> NumExpansions, IdentifierInfo *Id, bool IsDirectInit,
789 Expr *&Init) {
790 // Create an 'auto' or 'auto&' TypeSourceInfo that we can use to
791 // deduce against.
792 QualType DeductType = Context.getAutoDeductType();
793 TypeLocBuilder TLB;
794 AutoTypeLoc TL = TLB.push<AutoTypeLoc>(DeductType);
795 TL.setNameLoc(Loc);
796 if (ByRef) {
797 DeductType = BuildReferenceType(DeductType, true, Loc, Id);
798 assert(!DeductType.isNull() && "can't build reference to auto");
799 TLB.push<ReferenceTypeLoc>(DeductType).setSigilLoc(Loc);
800 }
801 if (EllipsisLoc.isValid()) {
802 if (Init->containsUnexpandedParameterPack()) {
803 Diag(EllipsisLoc, getLangOpts().CPlusPlus2a
804 ? diag::warn_cxx17_compat_init_capture_pack
805 : diag::ext_init_capture_pack);
806 DeductType = Context.getPackExpansionType(DeductType, NumExpansions);
807 TLB.push<PackExpansionTypeLoc>(DeductType).setEllipsisLoc(EllipsisLoc);
808 } else {
809 // Just ignore the ellipsis for now and form a non-pack variable. We'll
810 // diagnose this later when we try to capture it.
811 }
812 }
813 TypeSourceInfo *TSI = TLB.getTypeSourceInfo(Context, DeductType);
814
815 // Deduce the type of the init capture.
816 QualType DeducedType = deduceVarTypeFromInitializer(
817 /*VarDecl*/nullptr, DeclarationName(Id), DeductType, TSI,
818 SourceRange(Loc, Loc), IsDirectInit, Init);
819 if (DeducedType.isNull())
820 return QualType();
821
822 // Are we a non-list direct initialization?
823 ParenListExpr *CXXDirectInit = dyn_cast<ParenListExpr>(Init);
824
825 // Perform initialization analysis and ensure any implicit conversions
826 // (such as lvalue-to-rvalue) are enforced.
827 InitializedEntity Entity =
828 InitializedEntity::InitializeLambdaCapture(Id, DeducedType, Loc);
829 InitializationKind Kind =
830 IsDirectInit
831 ? (CXXDirectInit ? InitializationKind::CreateDirect(
832 Loc, Init->getBeginLoc(), Init->getEndLoc())
833 : InitializationKind::CreateDirectList(Loc))
834 : InitializationKind::CreateCopy(Loc, Init->getBeginLoc());
835
836 MultiExprArg Args = Init;
837 if (CXXDirectInit)
838 Args =
839 MultiExprArg(CXXDirectInit->getExprs(), CXXDirectInit->getNumExprs());
840 QualType DclT;
841 InitializationSequence InitSeq(*this, Entity, Kind, Args);
842 ExprResult Result = InitSeq.Perform(*this, Entity, Kind, Args, &DclT);
843
844 if (Result.isInvalid())
845 return QualType();
846
847 Init = Result.getAs<Expr>();
848 return DeducedType;
849 }
850
createLambdaInitCaptureVarDecl(SourceLocation Loc,QualType InitCaptureType,SourceLocation EllipsisLoc,IdentifierInfo * Id,unsigned InitStyle,Expr * Init)851 VarDecl *Sema::createLambdaInitCaptureVarDecl(SourceLocation Loc,
852 QualType InitCaptureType,
853 SourceLocation EllipsisLoc,
854 IdentifierInfo *Id,
855 unsigned InitStyle, Expr *Init) {
856 // FIXME: Retain the TypeSourceInfo from buildLambdaInitCaptureInitialization
857 // rather than reconstructing it here.
858 TypeSourceInfo *TSI = Context.getTrivialTypeSourceInfo(InitCaptureType, Loc);
859 if (auto PETL = TSI->getTypeLoc().getAs<PackExpansionTypeLoc>())
860 PETL.setEllipsisLoc(EllipsisLoc);
861
862 // Create a dummy variable representing the init-capture. This is not actually
863 // used as a variable, and only exists as a way to name and refer to the
864 // init-capture.
865 // FIXME: Pass in separate source locations for '&' and identifier.
866 VarDecl *NewVD = VarDecl::Create(Context, CurContext, Loc,
867 Loc, Id, InitCaptureType, TSI, SC_Auto);
868 NewVD->setInitCapture(true);
869 NewVD->setReferenced(true);
870 // FIXME: Pass in a VarDecl::InitializationStyle.
871 NewVD->setInitStyle(static_cast<VarDecl::InitializationStyle>(InitStyle));
872 NewVD->markUsed(Context);
873 NewVD->setInit(Init);
874 if (NewVD->isParameterPack())
875 getCurLambda()->LocalPacks.push_back(NewVD);
876 return NewVD;
877 }
878
addInitCapture(LambdaScopeInfo * LSI,VarDecl * Var)879 void Sema::addInitCapture(LambdaScopeInfo *LSI, VarDecl *Var) {
880 assert(Var->isInitCapture() && "init capture flag should be set");
881 LSI->addCapture(Var, /*isBlock*/false, Var->getType()->isReferenceType(),
882 /*isNested*/false, Var->getLocation(), SourceLocation(),
883 Var->getType(), /*Invalid*/false);
884 }
885
ActOnStartOfLambdaDefinition(LambdaIntroducer & Intro,Declarator & ParamInfo,Scope * CurScope)886 void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
887 Declarator &ParamInfo,
888 Scope *CurScope) {
889 LambdaScopeInfo *const LSI = getCurLambda();
890 assert(LSI && "LambdaScopeInfo should be on stack!");
891
892 // Determine if we're within a context where we know that the lambda will
893 // be dependent, because there are template parameters in scope.
894 bool KnownDependent;
895 if (LSI->NumExplicitTemplateParams > 0) {
896 auto *TemplateParamScope = CurScope->getTemplateParamParent();
897 assert(TemplateParamScope &&
898 "Lambda with explicit template param list should establish a "
899 "template param scope");
900 assert(TemplateParamScope->getParent());
901 KnownDependent = TemplateParamScope->getParent()
902 ->getTemplateParamParent() != nullptr;
903 } else {
904 KnownDependent = CurScope->getTemplateParamParent() != nullptr;
905 }
906
907 // Determine the signature of the call operator.
908 TypeSourceInfo *MethodTyInfo;
909 bool ExplicitParams = true;
910 bool ExplicitResultType = true;
911 bool ContainsUnexpandedParameterPack = false;
912 SourceLocation EndLoc;
913 SmallVector<ParmVarDecl *, 8> Params;
914 if (ParamInfo.getNumTypeObjects() == 0) {
915 // C++11 [expr.prim.lambda]p4:
916 // If a lambda-expression does not include a lambda-declarator, it is as
917 // if the lambda-declarator were ().
918 FunctionProtoType::ExtProtoInfo EPI(Context.getDefaultCallingConvention(
919 /*IsVariadic=*/false, /*IsCXXMethod=*/true));
920 EPI.HasTrailingReturn = true;
921 EPI.TypeQuals.addConst();
922 LangAS AS = getDefaultCXXMethodAddrSpace();
923 if (AS != LangAS::Default)
924 EPI.TypeQuals.addAddressSpace(AS);
925
926 // C++1y [expr.prim.lambda]:
927 // The lambda return type is 'auto', which is replaced by the
928 // trailing-return type if provided and/or deduced from 'return'
929 // statements
930 // We don't do this before C++1y, because we don't support deduced return
931 // types there.
932 QualType DefaultTypeForNoTrailingReturn =
933 getLangOpts().CPlusPlus14 ? Context.getAutoDeductType()
934 : Context.DependentTy;
935 QualType MethodTy =
936 Context.getFunctionType(DefaultTypeForNoTrailingReturn, None, EPI);
937 MethodTyInfo = Context.getTrivialTypeSourceInfo(MethodTy);
938 ExplicitParams = false;
939 ExplicitResultType = false;
940 EndLoc = Intro.Range.getEnd();
941 } else {
942 assert(ParamInfo.isFunctionDeclarator() &&
943 "lambda-declarator is a function");
944 DeclaratorChunk::FunctionTypeInfo &FTI = ParamInfo.getFunctionTypeInfo();
945
946 // C++11 [expr.prim.lambda]p5:
947 // This function call operator is declared const (9.3.1) if and only if
948 // the lambda-expression's parameter-declaration-clause is not followed
949 // by mutable. It is neither virtual nor declared volatile. [...]
950 if (!FTI.hasMutableQualifier()) {
951 FTI.getOrCreateMethodQualifiers().SetTypeQual(DeclSpec::TQ_const,
952 SourceLocation());
953 }
954
955 MethodTyInfo = GetTypeForDeclarator(ParamInfo, CurScope);
956 assert(MethodTyInfo && "no type from lambda-declarator");
957 EndLoc = ParamInfo.getSourceRange().getEnd();
958
959 ExplicitResultType = FTI.hasTrailingReturnType();
960
961 if (FTIHasNonVoidParameters(FTI)) {
962 Params.reserve(FTI.NumParams);
963 for (unsigned i = 0, e = FTI.NumParams; i != e; ++i)
964 Params.push_back(cast<ParmVarDecl>(FTI.Params[i].Param));
965 }
966
967 // Check for unexpanded parameter packs in the method type.
968 if (MethodTyInfo->getType()->containsUnexpandedParameterPack())
969 DiagnoseUnexpandedParameterPack(Intro.Range.getBegin(), MethodTyInfo,
970 UPPC_DeclarationType);
971 }
972
973 CXXRecordDecl *Class = createLambdaClosureType(Intro.Range, MethodTyInfo,
974 KnownDependent, Intro.Default);
975 CXXMethodDecl *Method =
976 startLambdaDefinition(Class, Intro.Range, MethodTyInfo, EndLoc, Params,
977 ParamInfo.getDeclSpec().getConstexprSpecifier(),
978 ParamInfo.getTrailingRequiresClause());
979 if (ExplicitParams)
980 CheckCXXDefaultArguments(Method);
981
982 // This represents the function body for the lambda function, check if we
983 // have to apply optnone due to a pragma.
984 AddRangeBasedOptnone(Method);
985
986 // code_seg attribute on lambda apply to the method.
987 if (Attr *A = getImplicitCodeSegOrSectionAttrForFunction(Method, /*IsDefinition=*/true))
988 Method->addAttr(A);
989
990 // Attributes on the lambda apply to the method.
991 ProcessDeclAttributes(CurScope, Method, ParamInfo);
992
993 // CUDA lambdas get implicit attributes based on the scope in which they're
994 // declared.
995 if (getLangOpts().CUDA)
996 CUDASetLambdaAttrs(Method);
997
998 // Number the lambda for linkage purposes if necessary.
999 handleLambdaNumbering(Class, Method);
1000
1001 // Introduce the function call operator as the current declaration context.
1002 PushDeclContext(CurScope, Method);
1003
1004 // Build the lambda scope.
1005 buildLambdaScope(LSI, Method, Intro.Range, Intro.Default, Intro.DefaultLoc,
1006 ExplicitParams, ExplicitResultType, !Method->isConst());
1007
1008 // C++11 [expr.prim.lambda]p9:
1009 // A lambda-expression whose smallest enclosing scope is a block scope is a
1010 // local lambda expression; any other lambda expression shall not have a
1011 // capture-default or simple-capture in its lambda-introducer.
1012 //
1013 // For simple-captures, this is covered by the check below that any named
1014 // entity is a variable that can be captured.
1015 //
1016 // For DR1632, we also allow a capture-default in any context where we can
1017 // odr-use 'this' (in particular, in a default initializer for a non-static
1018 // data member).
1019 if (Intro.Default != LCD_None && !Class->getParent()->isFunctionOrMethod() &&
1020 (getCurrentThisType().isNull() ||
1021 CheckCXXThisCapture(SourceLocation(), /*Explicit*/true,
1022 /*BuildAndDiagnose*/false)))
1023 Diag(Intro.DefaultLoc, diag::err_capture_default_non_local);
1024
1025 // Distinct capture names, for diagnostics.
1026 llvm::SmallSet<IdentifierInfo*, 8> CaptureNames;
1027
1028 // Handle explicit captures.
1029 SourceLocation PrevCaptureLoc
1030 = Intro.Default == LCD_None? Intro.Range.getBegin() : Intro.DefaultLoc;
1031 for (auto C = Intro.Captures.begin(), E = Intro.Captures.end(); C != E;
1032 PrevCaptureLoc = C->Loc, ++C) {
1033 if (C->Kind == LCK_This || C->Kind == LCK_StarThis) {
1034 if (C->Kind == LCK_StarThis)
1035 Diag(C->Loc, !getLangOpts().CPlusPlus17
1036 ? diag::ext_star_this_lambda_capture_cxx17
1037 : diag::warn_cxx14_compat_star_this_lambda_capture);
1038
1039 // C++11 [expr.prim.lambda]p8:
1040 // An identifier or this shall not appear more than once in a
1041 // lambda-capture.
1042 if (LSI->isCXXThisCaptured()) {
1043 Diag(C->Loc, diag::err_capture_more_than_once)
1044 << "'this'" << SourceRange(LSI->getCXXThisCapture().getLocation())
1045 << FixItHint::CreateRemoval(
1046 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1047 continue;
1048 }
1049
1050 // C++2a [expr.prim.lambda]p8:
1051 // If a lambda-capture includes a capture-default that is =,
1052 // each simple-capture of that lambda-capture shall be of the form
1053 // "&identifier", "this", or "* this". [ Note: The form [&,this] is
1054 // redundant but accepted for compatibility with ISO C++14. --end note ]
1055 if (Intro.Default == LCD_ByCopy && C->Kind != LCK_StarThis)
1056 Diag(C->Loc, !getLangOpts().CPlusPlus2a
1057 ? diag::ext_equals_this_lambda_capture_cxx2a
1058 : diag::warn_cxx17_compat_equals_this_lambda_capture);
1059
1060 // C++11 [expr.prim.lambda]p12:
1061 // If this is captured by a local lambda expression, its nearest
1062 // enclosing function shall be a non-static member function.
1063 QualType ThisCaptureType = getCurrentThisType();
1064 if (ThisCaptureType.isNull()) {
1065 Diag(C->Loc, diag::err_this_capture) << true;
1066 continue;
1067 }
1068
1069 CheckCXXThisCapture(C->Loc, /*Explicit=*/true, /*BuildAndDiagnose*/ true,
1070 /*FunctionScopeIndexToStopAtPtr*/ nullptr,
1071 C->Kind == LCK_StarThis);
1072 if (!LSI->Captures.empty())
1073 LSI->ExplicitCaptureRanges[LSI->Captures.size() - 1] = C->ExplicitRange;
1074 continue;
1075 }
1076
1077 assert(C->Id && "missing identifier for capture");
1078
1079 if (C->Init.isInvalid())
1080 continue;
1081
1082 VarDecl *Var = nullptr;
1083 if (C->Init.isUsable()) {
1084 Diag(C->Loc, getLangOpts().CPlusPlus14
1085 ? diag::warn_cxx11_compat_init_capture
1086 : diag::ext_init_capture);
1087
1088 // If the initializer expression is usable, but the InitCaptureType
1089 // is not, then an error has occurred - so ignore the capture for now.
1090 // for e.g., [n{0}] { }; <-- if no <initializer_list> is included.
1091 // FIXME: we should create the init capture variable and mark it invalid
1092 // in this case.
1093 if (C->InitCaptureType.get().isNull())
1094 continue;
1095
1096 if (C->Init.get()->containsUnexpandedParameterPack() &&
1097 !C->InitCaptureType.get()->getAs<PackExpansionType>())
1098 DiagnoseUnexpandedParameterPack(C->Init.get(), UPPC_Initializer);
1099
1100 unsigned InitStyle;
1101 switch (C->InitKind) {
1102 case LambdaCaptureInitKind::NoInit:
1103 llvm_unreachable("not an init-capture?");
1104 case LambdaCaptureInitKind::CopyInit:
1105 InitStyle = VarDecl::CInit;
1106 break;
1107 case LambdaCaptureInitKind::DirectInit:
1108 InitStyle = VarDecl::CallInit;
1109 break;
1110 case LambdaCaptureInitKind::ListInit:
1111 InitStyle = VarDecl::ListInit;
1112 break;
1113 }
1114 Var = createLambdaInitCaptureVarDecl(C->Loc, C->InitCaptureType.get(),
1115 C->EllipsisLoc, C->Id, InitStyle,
1116 C->Init.get());
1117 // C++1y [expr.prim.lambda]p11:
1118 // An init-capture behaves as if it declares and explicitly
1119 // captures a variable [...] whose declarative region is the
1120 // lambda-expression's compound-statement
1121 if (Var)
1122 PushOnScopeChains(Var, CurScope, false);
1123 } else {
1124 assert(C->InitKind == LambdaCaptureInitKind::NoInit &&
1125 "init capture has valid but null init?");
1126
1127 // C++11 [expr.prim.lambda]p8:
1128 // If a lambda-capture includes a capture-default that is &, the
1129 // identifiers in the lambda-capture shall not be preceded by &.
1130 // If a lambda-capture includes a capture-default that is =, [...]
1131 // each identifier it contains shall be preceded by &.
1132 if (C->Kind == LCK_ByRef && Intro.Default == LCD_ByRef) {
1133 Diag(C->Loc, diag::err_reference_capture_with_reference_default)
1134 << FixItHint::CreateRemoval(
1135 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1136 continue;
1137 } else if (C->Kind == LCK_ByCopy && Intro.Default == LCD_ByCopy) {
1138 Diag(C->Loc, diag::err_copy_capture_with_copy_default)
1139 << FixItHint::CreateRemoval(
1140 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1141 continue;
1142 }
1143
1144 // C++11 [expr.prim.lambda]p10:
1145 // The identifiers in a capture-list are looked up using the usual
1146 // rules for unqualified name lookup (3.4.1)
1147 DeclarationNameInfo Name(C->Id, C->Loc);
1148 LookupResult R(*this, Name, LookupOrdinaryName);
1149 LookupName(R, CurScope);
1150 if (R.isAmbiguous())
1151 continue;
1152 if (R.empty()) {
1153 // FIXME: Disable corrections that would add qualification?
1154 CXXScopeSpec ScopeSpec;
1155 DeclFilterCCC<VarDecl> Validator{};
1156 if (DiagnoseEmptyLookup(CurScope, ScopeSpec, R, Validator))
1157 continue;
1158 }
1159
1160 Var = R.getAsSingle<VarDecl>();
1161 if (Var && DiagnoseUseOfDecl(Var, C->Loc))
1162 continue;
1163 }
1164
1165 // C++11 [expr.prim.lambda]p8:
1166 // An identifier or this shall not appear more than once in a
1167 // lambda-capture.
1168 if (!CaptureNames.insert(C->Id).second) {
1169 if (Var && LSI->isCaptured(Var)) {
1170 Diag(C->Loc, diag::err_capture_more_than_once)
1171 << C->Id << SourceRange(LSI->getCapture(Var).getLocation())
1172 << FixItHint::CreateRemoval(
1173 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1174 } else
1175 // Previous capture captured something different (one or both was
1176 // an init-cpature): no fixit.
1177 Diag(C->Loc, diag::err_capture_more_than_once) << C->Id;
1178 continue;
1179 }
1180
1181 // C++11 [expr.prim.lambda]p10:
1182 // [...] each such lookup shall find a variable with automatic storage
1183 // duration declared in the reaching scope of the local lambda expression.
1184 // Note that the 'reaching scope' check happens in tryCaptureVariable().
1185 if (!Var) {
1186 Diag(C->Loc, diag::err_capture_does_not_name_variable) << C->Id;
1187 continue;
1188 }
1189
1190 // Ignore invalid decls; they'll just confuse the code later.
1191 if (Var->isInvalidDecl())
1192 continue;
1193
1194 if (!Var->hasLocalStorage()) {
1195 Diag(C->Loc, diag::err_capture_non_automatic_variable) << C->Id;
1196 Diag(Var->getLocation(), diag::note_previous_decl) << C->Id;
1197 continue;
1198 }
1199
1200 // C++11 [expr.prim.lambda]p23:
1201 // A capture followed by an ellipsis is a pack expansion (14.5.3).
1202 SourceLocation EllipsisLoc;
1203 if (C->EllipsisLoc.isValid()) {
1204 if (Var->isParameterPack()) {
1205 EllipsisLoc = C->EllipsisLoc;
1206 } else {
1207 Diag(C->EllipsisLoc, diag::err_pack_expansion_without_parameter_packs)
1208 << (C->Init.isUsable() ? C->Init.get()->getSourceRange()
1209 : SourceRange(C->Loc));
1210
1211 // Just ignore the ellipsis.
1212 }
1213 } else if (Var->isParameterPack()) {
1214 ContainsUnexpandedParameterPack = true;
1215 }
1216
1217 if (C->Init.isUsable()) {
1218 addInitCapture(LSI, Var);
1219 } else {
1220 TryCaptureKind Kind = C->Kind == LCK_ByRef ? TryCapture_ExplicitByRef :
1221 TryCapture_ExplicitByVal;
1222 tryCaptureVariable(Var, C->Loc, Kind, EllipsisLoc);
1223 }
1224 if (!LSI->Captures.empty())
1225 LSI->ExplicitCaptureRanges[LSI->Captures.size() - 1] = C->ExplicitRange;
1226 }
1227 finishLambdaExplicitCaptures(LSI);
1228
1229 LSI->ContainsUnexpandedParameterPack |= ContainsUnexpandedParameterPack;
1230
1231 // Add lambda parameters into scope.
1232 addLambdaParameters(Intro.Captures, Method, CurScope);
1233
1234 // Enter a new evaluation context to insulate the lambda from any
1235 // cleanups from the enclosing full-expression.
1236 PushExpressionEvaluationContext(
1237 ExpressionEvaluationContext::PotentiallyEvaluated);
1238 }
1239
ActOnLambdaError(SourceLocation StartLoc,Scope * CurScope,bool IsInstantiation)1240 void Sema::ActOnLambdaError(SourceLocation StartLoc, Scope *CurScope,
1241 bool IsInstantiation) {
1242 LambdaScopeInfo *LSI = cast<LambdaScopeInfo>(FunctionScopes.back());
1243
1244 // Leave the expression-evaluation context.
1245 DiscardCleanupsInEvaluationContext();
1246 PopExpressionEvaluationContext();
1247
1248 // Leave the context of the lambda.
1249 if (!IsInstantiation)
1250 PopDeclContext();
1251
1252 // Finalize the lambda.
1253 CXXRecordDecl *Class = LSI->Lambda;
1254 Class->setInvalidDecl();
1255 SmallVector<Decl*, 4> Fields(Class->fields());
1256 ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
1257 SourceLocation(), ParsedAttributesView());
1258 CheckCompletedCXXClass(nullptr, Class);
1259
1260 PopFunctionScopeInfo();
1261 }
1262
getLambdaConversionFunctionResultType(const FunctionProtoType * CallOpProto)1263 QualType Sema::getLambdaConversionFunctionResultType(
1264 const FunctionProtoType *CallOpProto) {
1265 // The function type inside the pointer type is the same as the call
1266 // operator with some tweaks. The calling convention is the default free
1267 // function convention, and the type qualifications are lost.
1268 const FunctionProtoType::ExtProtoInfo CallOpExtInfo =
1269 CallOpProto->getExtProtoInfo();
1270 FunctionProtoType::ExtProtoInfo InvokerExtInfo = CallOpExtInfo;
1271 CallingConv CC = Context.getDefaultCallingConvention(
1272 CallOpProto->isVariadic(), /*IsCXXMethod=*/false);
1273 InvokerExtInfo.ExtInfo = InvokerExtInfo.ExtInfo.withCallingConv(CC);
1274 InvokerExtInfo.TypeQuals = Qualifiers();
1275 assert(InvokerExtInfo.RefQualifier == RQ_None &&
1276 "Lambda's call operator should not have a reference qualifier");
1277 return Context.getFunctionType(CallOpProto->getReturnType(),
1278 CallOpProto->getParamTypes(), InvokerExtInfo);
1279 }
1280
1281 /// Add a lambda's conversion to function pointer, as described in
1282 /// C++11 [expr.prim.lambda]p6.
addFunctionPointerConversion(Sema & S,SourceRange IntroducerRange,CXXRecordDecl * Class,CXXMethodDecl * CallOperator)1283 static void addFunctionPointerConversion(Sema &S,
1284 SourceRange IntroducerRange,
1285 CXXRecordDecl *Class,
1286 CXXMethodDecl *CallOperator) {
1287 // This conversion is explicitly disabled if the lambda's function has
1288 // pass_object_size attributes on any of its parameters.
1289 auto HasPassObjectSizeAttr = [](const ParmVarDecl *P) {
1290 return P->hasAttr<PassObjectSizeAttr>();
1291 };
1292 if (llvm::any_of(CallOperator->parameters(), HasPassObjectSizeAttr))
1293 return;
1294
1295 // Add the conversion to function pointer.
1296 QualType InvokerFunctionTy = S.getLambdaConversionFunctionResultType(
1297 CallOperator->getType()->castAs<FunctionProtoType>());
1298 QualType PtrToFunctionTy = S.Context.getPointerType(InvokerFunctionTy);
1299
1300 // Create the type of the conversion function.
1301 FunctionProtoType::ExtProtoInfo ConvExtInfo(
1302 S.Context.getDefaultCallingConvention(
1303 /*IsVariadic=*/false, /*IsCXXMethod=*/true));
1304 // The conversion function is always const and noexcept.
1305 ConvExtInfo.TypeQuals = Qualifiers();
1306 ConvExtInfo.TypeQuals.addConst();
1307 ConvExtInfo.ExceptionSpec.Type = EST_BasicNoexcept;
1308 QualType ConvTy =
1309 S.Context.getFunctionType(PtrToFunctionTy, None, ConvExtInfo);
1310
1311 SourceLocation Loc = IntroducerRange.getBegin();
1312 DeclarationName ConversionName
1313 = S.Context.DeclarationNames.getCXXConversionFunctionName(
1314 S.Context.getCanonicalType(PtrToFunctionTy));
1315 DeclarationNameLoc ConvNameLoc;
1316 // Construct a TypeSourceInfo for the conversion function, and wire
1317 // all the parameters appropriately for the FunctionProtoTypeLoc
1318 // so that everything works during transformation/instantiation of
1319 // generic lambdas.
1320 // The main reason for wiring up the parameters of the conversion
1321 // function with that of the call operator is so that constructs
1322 // like the following work:
1323 // auto L = [](auto b) { <-- 1
1324 // return [](auto a) -> decltype(a) { <-- 2
1325 // return a;
1326 // };
1327 // };
1328 // int (*fp)(int) = L(5);
1329 // Because the trailing return type can contain DeclRefExprs that refer
1330 // to the original call operator's variables, we hijack the call
1331 // operators ParmVarDecls below.
1332 TypeSourceInfo *ConvNamePtrToFunctionTSI =
1333 S.Context.getTrivialTypeSourceInfo(PtrToFunctionTy, Loc);
1334 ConvNameLoc.NamedType.TInfo = ConvNamePtrToFunctionTSI;
1335
1336 // The conversion function is a conversion to a pointer-to-function.
1337 TypeSourceInfo *ConvTSI = S.Context.getTrivialTypeSourceInfo(ConvTy, Loc);
1338 FunctionProtoTypeLoc ConvTL =
1339 ConvTSI->getTypeLoc().getAs<FunctionProtoTypeLoc>();
1340 // Get the result of the conversion function which is a pointer-to-function.
1341 PointerTypeLoc PtrToFunctionTL =
1342 ConvTL.getReturnLoc().getAs<PointerTypeLoc>();
1343 // Do the same for the TypeSourceInfo that is used to name the conversion
1344 // operator.
1345 PointerTypeLoc ConvNamePtrToFunctionTL =
1346 ConvNamePtrToFunctionTSI->getTypeLoc().getAs<PointerTypeLoc>();
1347
1348 // Get the underlying function types that the conversion function will
1349 // be converting to (should match the type of the call operator).
1350 FunctionProtoTypeLoc CallOpConvTL =
1351 PtrToFunctionTL.getPointeeLoc().getAs<FunctionProtoTypeLoc>();
1352 FunctionProtoTypeLoc CallOpConvNameTL =
1353 ConvNamePtrToFunctionTL.getPointeeLoc().getAs<FunctionProtoTypeLoc>();
1354
1355 // Wire up the FunctionProtoTypeLocs with the call operator's parameters.
1356 // These parameter's are essentially used to transform the name and
1357 // the type of the conversion operator. By using the same parameters
1358 // as the call operator's we don't have to fix any back references that
1359 // the trailing return type of the call operator's uses (such as
1360 // decltype(some_type<decltype(a)>::type{} + decltype(a){}) etc.)
1361 // - we can simply use the return type of the call operator, and
1362 // everything should work.
1363 SmallVector<ParmVarDecl *, 4> InvokerParams;
1364 for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I) {
1365 ParmVarDecl *From = CallOperator->getParamDecl(I);
1366
1367 InvokerParams.push_back(ParmVarDecl::Create(
1368 S.Context,
1369 // Temporarily add to the TU. This is set to the invoker below.
1370 S.Context.getTranslationUnitDecl(), From->getBeginLoc(),
1371 From->getLocation(), From->getIdentifier(), From->getType(),
1372 From->getTypeSourceInfo(), From->getStorageClass(),
1373 /*DefArg=*/nullptr));
1374 CallOpConvTL.setParam(I, From);
1375 CallOpConvNameTL.setParam(I, From);
1376 }
1377
1378 CXXConversionDecl *Conversion = CXXConversionDecl::Create(
1379 S.Context, Class, Loc,
1380 DeclarationNameInfo(ConversionName, Loc, ConvNameLoc), ConvTy, ConvTSI,
1381 /*isInline=*/true, ExplicitSpecifier(),
1382 S.getLangOpts().CPlusPlus17 ? CSK_constexpr : CSK_unspecified,
1383 CallOperator->getBody()->getEndLoc());
1384 Conversion->setAccess(AS_public);
1385 Conversion->setImplicit(true);
1386
1387 if (Class->isGenericLambda()) {
1388 // Create a template version of the conversion operator, using the template
1389 // parameter list of the function call operator.
1390 FunctionTemplateDecl *TemplateCallOperator =
1391 CallOperator->getDescribedFunctionTemplate();
1392 FunctionTemplateDecl *ConversionTemplate =
1393 FunctionTemplateDecl::Create(S.Context, Class,
1394 Loc, ConversionName,
1395 TemplateCallOperator->getTemplateParameters(),
1396 Conversion);
1397 ConversionTemplate->setAccess(AS_public);
1398 ConversionTemplate->setImplicit(true);
1399 Conversion->setDescribedFunctionTemplate(ConversionTemplate);
1400 Class->addDecl(ConversionTemplate);
1401 } else
1402 Class->addDecl(Conversion);
1403 // Add a non-static member function that will be the result of
1404 // the conversion with a certain unique ID.
1405 DeclarationName InvokerName = &S.Context.Idents.get(
1406 getLambdaStaticInvokerName());
1407 // FIXME: Instead of passing in the CallOperator->getTypeSourceInfo()
1408 // we should get a prebuilt TrivialTypeSourceInfo from Context
1409 // using FunctionTy & Loc and get its TypeLoc as a FunctionProtoTypeLoc
1410 // then rewire the parameters accordingly, by hoisting up the InvokeParams
1411 // loop below and then use its Params to set Invoke->setParams(...) below.
1412 // This would avoid the 'const' qualifier of the calloperator from
1413 // contaminating the type of the invoker, which is currently adjusted
1414 // in SemaTemplateDeduction.cpp:DeduceTemplateArguments. Fixing the
1415 // trailing return type of the invoker would require a visitor to rebuild
1416 // the trailing return type and adjusting all back DeclRefExpr's to refer
1417 // to the new static invoker parameters - not the call operator's.
1418 CXXMethodDecl *Invoke = CXXMethodDecl::Create(
1419 S.Context, Class, Loc, DeclarationNameInfo(InvokerName, Loc),
1420 InvokerFunctionTy, CallOperator->getTypeSourceInfo(), SC_Static,
1421 /*isInline=*/true, CSK_unspecified, CallOperator->getBody()->getEndLoc());
1422 for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I)
1423 InvokerParams[I]->setOwningFunction(Invoke);
1424 Invoke->setParams(InvokerParams);
1425 Invoke->setAccess(AS_private);
1426 Invoke->setImplicit(true);
1427 if (Class->isGenericLambda()) {
1428 FunctionTemplateDecl *TemplateCallOperator =
1429 CallOperator->getDescribedFunctionTemplate();
1430 FunctionTemplateDecl *StaticInvokerTemplate = FunctionTemplateDecl::Create(
1431 S.Context, Class, Loc, InvokerName,
1432 TemplateCallOperator->getTemplateParameters(),
1433 Invoke);
1434 StaticInvokerTemplate->setAccess(AS_private);
1435 StaticInvokerTemplate->setImplicit(true);
1436 Invoke->setDescribedFunctionTemplate(StaticInvokerTemplate);
1437 Class->addDecl(StaticInvokerTemplate);
1438 } else
1439 Class->addDecl(Invoke);
1440 }
1441
1442 /// Add a lambda's conversion to block pointer.
addBlockPointerConversion(Sema & S,SourceRange IntroducerRange,CXXRecordDecl * Class,CXXMethodDecl * CallOperator)1443 static void addBlockPointerConversion(Sema &S,
1444 SourceRange IntroducerRange,
1445 CXXRecordDecl *Class,
1446 CXXMethodDecl *CallOperator) {
1447 QualType FunctionTy = S.getLambdaConversionFunctionResultType(
1448 CallOperator->getType()->castAs<FunctionProtoType>());
1449 QualType BlockPtrTy = S.Context.getBlockPointerType(FunctionTy);
1450
1451 FunctionProtoType::ExtProtoInfo ConversionEPI(
1452 S.Context.getDefaultCallingConvention(
1453 /*IsVariadic=*/false, /*IsCXXMethod=*/true));
1454 ConversionEPI.TypeQuals = Qualifiers();
1455 ConversionEPI.TypeQuals.addConst();
1456 QualType ConvTy = S.Context.getFunctionType(BlockPtrTy, None, ConversionEPI);
1457
1458 SourceLocation Loc = IntroducerRange.getBegin();
1459 DeclarationName Name
1460 = S.Context.DeclarationNames.getCXXConversionFunctionName(
1461 S.Context.getCanonicalType(BlockPtrTy));
1462 DeclarationNameLoc NameLoc;
1463 NameLoc.NamedType.TInfo = S.Context.getTrivialTypeSourceInfo(BlockPtrTy, Loc);
1464 CXXConversionDecl *Conversion = CXXConversionDecl::Create(
1465 S.Context, Class, Loc, DeclarationNameInfo(Name, Loc, NameLoc), ConvTy,
1466 S.Context.getTrivialTypeSourceInfo(ConvTy, Loc),
1467 /*isInline=*/true, ExplicitSpecifier(), CSK_unspecified,
1468 CallOperator->getBody()->getEndLoc());
1469 Conversion->setAccess(AS_public);
1470 Conversion->setImplicit(true);
1471 Class->addDecl(Conversion);
1472 }
1473
BuildCaptureInit(const Capture & Cap,SourceLocation ImplicitCaptureLoc,bool IsOpenMPMapping)1474 ExprResult Sema::BuildCaptureInit(const Capture &Cap,
1475 SourceLocation ImplicitCaptureLoc,
1476 bool IsOpenMPMapping) {
1477 // VLA captures don't have a stored initialization expression.
1478 if (Cap.isVLATypeCapture())
1479 return ExprResult();
1480
1481 // An init-capture is initialized directly from its stored initializer.
1482 if (Cap.isInitCapture())
1483 return Cap.getVariable()->getInit();
1484
1485 // For anything else, build an initialization expression. For an implicit
1486 // capture, the capture notionally happens at the capture-default, so use
1487 // that location here.
1488 SourceLocation Loc =
1489 ImplicitCaptureLoc.isValid() ? ImplicitCaptureLoc : Cap.getLocation();
1490
1491 // C++11 [expr.prim.lambda]p21:
1492 // When the lambda-expression is evaluated, the entities that
1493 // are captured by copy are used to direct-initialize each
1494 // corresponding non-static data member of the resulting closure
1495 // object. (For array members, the array elements are
1496 // direct-initialized in increasing subscript order.) These
1497 // initializations are performed in the (unspecified) order in
1498 // which the non-static data members are declared.
1499
1500 // C++ [expr.prim.lambda]p12:
1501 // An entity captured by a lambda-expression is odr-used (3.2) in
1502 // the scope containing the lambda-expression.
1503 ExprResult Init;
1504 IdentifierInfo *Name = nullptr;
1505 if (Cap.isThisCapture()) {
1506 QualType ThisTy = getCurrentThisType();
1507 Expr *This = BuildCXXThisExpr(Loc, ThisTy, ImplicitCaptureLoc.isValid());
1508 if (Cap.isCopyCapture())
1509 Init = CreateBuiltinUnaryOp(Loc, UO_Deref, This);
1510 else
1511 Init = This;
1512 } else {
1513 assert(Cap.isVariableCapture() && "unknown kind of capture");
1514 VarDecl *Var = Cap.getVariable();
1515 Name = Var->getIdentifier();
1516 Init = BuildDeclarationNameExpr(
1517 CXXScopeSpec(), DeclarationNameInfo(Var->getDeclName(), Loc), Var);
1518 }
1519
1520 // In OpenMP, the capture kind doesn't actually describe how to capture:
1521 // variables are "mapped" onto the device in a process that does not formally
1522 // make a copy, even for a "copy capture".
1523 if (IsOpenMPMapping)
1524 return Init;
1525
1526 if (Init.isInvalid())
1527 return ExprError();
1528
1529 Expr *InitExpr = Init.get();
1530 InitializedEntity Entity = InitializedEntity::InitializeLambdaCapture(
1531 Name, Cap.getCaptureType(), Loc);
1532 InitializationKind InitKind =
1533 InitializationKind::CreateDirect(Loc, Loc, Loc);
1534 InitializationSequence InitSeq(*this, Entity, InitKind, InitExpr);
1535 return InitSeq.Perform(*this, Entity, InitKind, InitExpr);
1536 }
1537
ActOnLambdaExpr(SourceLocation StartLoc,Stmt * Body,Scope * CurScope)1538 ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
1539 Scope *CurScope) {
1540 LambdaScopeInfo LSI = *cast<LambdaScopeInfo>(FunctionScopes.back());
1541 ActOnFinishFunctionBody(LSI.CallOperator, Body);
1542 return BuildLambdaExpr(StartLoc, Body->getEndLoc(), &LSI);
1543 }
1544
1545 static LambdaCaptureDefault
mapImplicitCaptureStyle(CapturingScopeInfo::ImplicitCaptureStyle ICS)1546 mapImplicitCaptureStyle(CapturingScopeInfo::ImplicitCaptureStyle ICS) {
1547 switch (ICS) {
1548 case CapturingScopeInfo::ImpCap_None:
1549 return LCD_None;
1550 case CapturingScopeInfo::ImpCap_LambdaByval:
1551 return LCD_ByCopy;
1552 case CapturingScopeInfo::ImpCap_CapturedRegion:
1553 case CapturingScopeInfo::ImpCap_LambdaByref:
1554 return LCD_ByRef;
1555 case CapturingScopeInfo::ImpCap_Block:
1556 llvm_unreachable("block capture in lambda");
1557 }
1558 llvm_unreachable("Unknown implicit capture style");
1559 }
1560
CaptureHasSideEffects(const Capture & From)1561 bool Sema::CaptureHasSideEffects(const Capture &From) {
1562 if (From.isInitCapture()) {
1563 Expr *Init = From.getVariable()->getInit();
1564 if (Init && Init->HasSideEffects(Context))
1565 return true;
1566 }
1567
1568 if (!From.isCopyCapture())
1569 return false;
1570
1571 const QualType T = From.isThisCapture()
1572 ? getCurrentThisType()->getPointeeType()
1573 : From.getCaptureType();
1574
1575 if (T.isVolatileQualified())
1576 return true;
1577
1578 const Type *BaseT = T->getBaseElementTypeUnsafe();
1579 if (const CXXRecordDecl *RD = BaseT->getAsCXXRecordDecl())
1580 return !RD->isCompleteDefinition() || !RD->hasTrivialCopyConstructor() ||
1581 !RD->hasTrivialDestructor();
1582
1583 return false;
1584 }
1585
DiagnoseUnusedLambdaCapture(SourceRange CaptureRange,const Capture & From)1586 bool Sema::DiagnoseUnusedLambdaCapture(SourceRange CaptureRange,
1587 const Capture &From) {
1588 if (CaptureHasSideEffects(From))
1589 return false;
1590
1591 if (From.isVLATypeCapture())
1592 return false;
1593
1594 auto diag = Diag(From.getLocation(), diag::warn_unused_lambda_capture);
1595 if (From.isThisCapture())
1596 diag << "'this'";
1597 else
1598 diag << From.getVariable();
1599 diag << From.isNonODRUsed();
1600 diag << FixItHint::CreateRemoval(CaptureRange);
1601 return true;
1602 }
1603
1604 /// Create a field within the lambda class or captured statement record for the
1605 /// given capture.
BuildCaptureField(RecordDecl * RD,const sema::Capture & Capture)1606 FieldDecl *Sema::BuildCaptureField(RecordDecl *RD,
1607 const sema::Capture &Capture) {
1608 SourceLocation Loc = Capture.getLocation();
1609 QualType FieldType = Capture.getCaptureType();
1610
1611 TypeSourceInfo *TSI = nullptr;
1612 if (Capture.isVariableCapture()) {
1613 auto *Var = Capture.getVariable();
1614 if (Var->isInitCapture())
1615 TSI = Capture.getVariable()->getTypeSourceInfo();
1616 }
1617
1618 // FIXME: Should we really be doing this? A null TypeSourceInfo seems more
1619 // appropriate, at least for an implicit capture.
1620 if (!TSI)
1621 TSI = Context.getTrivialTypeSourceInfo(FieldType, Loc);
1622
1623 // Build the non-static data member.
1624 FieldDecl *Field =
1625 FieldDecl::Create(Context, RD, Loc, Loc, nullptr, FieldType, TSI, nullptr,
1626 false, ICIS_NoInit);
1627 // If the variable being captured has an invalid type, mark the class as
1628 // invalid as well.
1629 if (!FieldType->isDependentType()) {
1630 if (RequireCompleteType(Loc, FieldType, diag::err_field_incomplete)) {
1631 RD->setInvalidDecl();
1632 Field->setInvalidDecl();
1633 } else {
1634 NamedDecl *Def;
1635 FieldType->isIncompleteType(&Def);
1636 if (Def && Def->isInvalidDecl()) {
1637 RD->setInvalidDecl();
1638 Field->setInvalidDecl();
1639 }
1640 }
1641 }
1642 Field->setImplicit(true);
1643 Field->setAccess(AS_private);
1644 RD->addDecl(Field);
1645
1646 if (Capture.isVLATypeCapture())
1647 Field->setCapturedVLAType(Capture.getCapturedVLAType());
1648
1649 return Field;
1650 }
1651
BuildLambdaExpr(SourceLocation StartLoc,SourceLocation EndLoc,LambdaScopeInfo * LSI)1652 ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
1653 LambdaScopeInfo *LSI) {
1654 // Collect information from the lambda scope.
1655 SmallVector<LambdaCapture, 4> Captures;
1656 SmallVector<Expr *, 4> CaptureInits;
1657 SourceLocation CaptureDefaultLoc = LSI->CaptureDefaultLoc;
1658 LambdaCaptureDefault CaptureDefault =
1659 mapImplicitCaptureStyle(LSI->ImpCaptureStyle);
1660 CXXRecordDecl *Class;
1661 CXXMethodDecl *CallOperator;
1662 SourceRange IntroducerRange;
1663 bool ExplicitParams;
1664 bool ExplicitResultType;
1665 CleanupInfo LambdaCleanup;
1666 bool ContainsUnexpandedParameterPack;
1667 bool IsGenericLambda;
1668 {
1669 CallOperator = LSI->CallOperator;
1670 Class = LSI->Lambda;
1671 IntroducerRange = LSI->IntroducerRange;
1672 ExplicitParams = LSI->ExplicitParams;
1673 ExplicitResultType = !LSI->HasImplicitReturnType;
1674 LambdaCleanup = LSI->Cleanup;
1675 ContainsUnexpandedParameterPack = LSI->ContainsUnexpandedParameterPack;
1676 IsGenericLambda = Class->isGenericLambda();
1677
1678 CallOperator->setLexicalDeclContext(Class);
1679 Decl *TemplateOrNonTemplateCallOperatorDecl =
1680 CallOperator->getDescribedFunctionTemplate()
1681 ? CallOperator->getDescribedFunctionTemplate()
1682 : cast<Decl>(CallOperator);
1683
1684 // FIXME: Is this really the best choice? Keeping the lexical decl context
1685 // set as CurContext seems more faithful to the source.
1686 TemplateOrNonTemplateCallOperatorDecl->setLexicalDeclContext(Class);
1687
1688 PopExpressionEvaluationContext();
1689
1690 // True if the current capture has a used capture or default before it.
1691 bool CurHasPreviousCapture = CaptureDefault != LCD_None;
1692 SourceLocation PrevCaptureLoc = CurHasPreviousCapture ?
1693 CaptureDefaultLoc : IntroducerRange.getBegin();
1694
1695 for (unsigned I = 0, N = LSI->Captures.size(); I != N; ++I) {
1696 const Capture &From = LSI->Captures[I];
1697
1698 if (From.isInvalid())
1699 return ExprError();
1700
1701 assert(!From.isBlockCapture() && "Cannot capture __block variables");
1702 bool IsImplicit = I >= LSI->NumExplicitCaptures;
1703 SourceLocation ImplicitCaptureLoc =
1704 IsImplicit ? CaptureDefaultLoc : SourceLocation();
1705
1706 // Use source ranges of explicit captures for fixits where available.
1707 SourceRange CaptureRange = LSI->ExplicitCaptureRanges[I];
1708
1709 // Warn about unused explicit captures.
1710 bool IsCaptureUsed = true;
1711 if (!CurContext->isDependentContext() && !IsImplicit &&
1712 !From.isODRUsed()) {
1713 // Initialized captures that are non-ODR used may not be eliminated.
1714 // FIXME: Where did the IsGenericLambda here come from?
1715 bool NonODRUsedInitCapture =
1716 IsGenericLambda && From.isNonODRUsed() && From.isInitCapture();
1717 if (!NonODRUsedInitCapture) {
1718 bool IsLast = (I + 1) == LSI->NumExplicitCaptures;
1719 SourceRange FixItRange;
1720 if (CaptureRange.isValid()) {
1721 if (!CurHasPreviousCapture && !IsLast) {
1722 // If there are no captures preceding this capture, remove the
1723 // following comma.
1724 FixItRange = SourceRange(CaptureRange.getBegin(),
1725 getLocForEndOfToken(CaptureRange.getEnd()));
1726 } else {
1727 // Otherwise, remove the comma since the last used capture.
1728 FixItRange = SourceRange(getLocForEndOfToken(PrevCaptureLoc),
1729 CaptureRange.getEnd());
1730 }
1731 }
1732
1733 IsCaptureUsed = !DiagnoseUnusedLambdaCapture(FixItRange, From);
1734 }
1735 }
1736
1737 if (CaptureRange.isValid()) {
1738 CurHasPreviousCapture |= IsCaptureUsed;
1739 PrevCaptureLoc = CaptureRange.getEnd();
1740 }
1741
1742 // Map the capture to our AST representation.
1743 LambdaCapture Capture = [&] {
1744 if (From.isThisCapture()) {
1745 // Capturing 'this' implicitly with a default of '[=]' is deprecated,
1746 // because it results in a reference capture. Don't warn prior to
1747 // C++2a; there's nothing that can be done about it before then.
1748 if (getLangOpts().CPlusPlus2a && IsImplicit &&
1749 CaptureDefault == LCD_ByCopy) {
1750 Diag(From.getLocation(), diag::warn_deprecated_this_capture);
1751 Diag(CaptureDefaultLoc, diag::note_deprecated_this_capture)
1752 << FixItHint::CreateInsertion(
1753 getLocForEndOfToken(CaptureDefaultLoc), ", this");
1754 }
1755 return LambdaCapture(From.getLocation(), IsImplicit,
1756 From.isCopyCapture() ? LCK_StarThis : LCK_This);
1757 } else if (From.isVLATypeCapture()) {
1758 return LambdaCapture(From.getLocation(), IsImplicit, LCK_VLAType);
1759 } else {
1760 assert(From.isVariableCapture() && "unknown kind of capture");
1761 VarDecl *Var = From.getVariable();
1762 LambdaCaptureKind Kind =
1763 From.isCopyCapture() ? LCK_ByCopy : LCK_ByRef;
1764 return LambdaCapture(From.getLocation(), IsImplicit, Kind, Var,
1765 From.getEllipsisLoc());
1766 }
1767 }();
1768
1769 // Form the initializer for the capture field.
1770 ExprResult Init = BuildCaptureInit(From, ImplicitCaptureLoc);
1771
1772 // FIXME: Skip this capture if the capture is not used, the initializer
1773 // has no side-effects, the type of the capture is trivial, and the
1774 // lambda is not externally visible.
1775
1776 // Add a FieldDecl for the capture and form its initializer.
1777 BuildCaptureField(Class, From);
1778 Captures.push_back(Capture);
1779 CaptureInits.push_back(Init.get());
1780 }
1781
1782 // C++11 [expr.prim.lambda]p6:
1783 // The closure type for a lambda-expression with no lambda-capture
1784 // has a public non-virtual non-explicit const conversion function
1785 // to pointer to function having the same parameter and return
1786 // types as the closure type's function call operator.
1787 if (Captures.empty() && CaptureDefault == LCD_None)
1788 addFunctionPointerConversion(*this, IntroducerRange, Class,
1789 CallOperator);
1790
1791 // Objective-C++:
1792 // The closure type for a lambda-expression has a public non-virtual
1793 // non-explicit const conversion function to a block pointer having the
1794 // same parameter and return types as the closure type's function call
1795 // operator.
1796 // FIXME: Fix generic lambda to block conversions.
1797 if (getLangOpts().Blocks && getLangOpts().ObjC && !IsGenericLambda)
1798 addBlockPointerConversion(*this, IntroducerRange, Class, CallOperator);
1799
1800 // Finalize the lambda class.
1801 SmallVector<Decl*, 4> Fields(Class->fields());
1802 ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
1803 SourceLocation(), ParsedAttributesView());
1804 CheckCompletedCXXClass(nullptr, Class);
1805 }
1806
1807 Cleanup.mergeFrom(LambdaCleanup);
1808
1809 LambdaExpr *Lambda = LambdaExpr::Create(Context, Class, IntroducerRange,
1810 CaptureDefault, CaptureDefaultLoc,
1811 Captures,
1812 ExplicitParams, ExplicitResultType,
1813 CaptureInits, EndLoc,
1814 ContainsUnexpandedParameterPack);
1815 // If the lambda expression's call operator is not explicitly marked constexpr
1816 // and we are not in a dependent context, analyze the call operator to infer
1817 // its constexpr-ness, suppressing diagnostics while doing so.
1818 if (getLangOpts().CPlusPlus17 && !CallOperator->isInvalidDecl() &&
1819 !CallOperator->isConstexpr() &&
1820 !isa<CoroutineBodyStmt>(CallOperator->getBody()) &&
1821 !Class->getDeclContext()->isDependentContext()) {
1822 CallOperator->setConstexprKind(
1823 CheckConstexprFunctionDefinition(CallOperator,
1824 CheckConstexprKind::CheckValid)
1825 ? CSK_constexpr
1826 : CSK_unspecified);
1827 }
1828
1829 // Emit delayed shadowing warnings now that the full capture list is known.
1830 DiagnoseShadowingLambdaDecls(LSI);
1831
1832 if (!CurContext->isDependentContext()) {
1833 switch (ExprEvalContexts.back().Context) {
1834 // C++11 [expr.prim.lambda]p2:
1835 // A lambda-expression shall not appear in an unevaluated operand
1836 // (Clause 5).
1837 case ExpressionEvaluationContext::Unevaluated:
1838 case ExpressionEvaluationContext::UnevaluatedList:
1839 case ExpressionEvaluationContext::UnevaluatedAbstract:
1840 // C++1y [expr.const]p2:
1841 // A conditional-expression e is a core constant expression unless the
1842 // evaluation of e, following the rules of the abstract machine, would
1843 // evaluate [...] a lambda-expression.
1844 //
1845 // This is technically incorrect, there are some constant evaluated contexts
1846 // where this should be allowed. We should probably fix this when DR1607 is
1847 // ratified, it lays out the exact set of conditions where we shouldn't
1848 // allow a lambda-expression.
1849 case ExpressionEvaluationContext::ConstantEvaluated:
1850 // We don't actually diagnose this case immediately, because we
1851 // could be within a context where we might find out later that
1852 // the expression is potentially evaluated (e.g., for typeid).
1853 ExprEvalContexts.back().Lambdas.push_back(Lambda);
1854 break;
1855
1856 case ExpressionEvaluationContext::DiscardedStatement:
1857 case ExpressionEvaluationContext::PotentiallyEvaluated:
1858 case ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed:
1859 break;
1860 }
1861 }
1862
1863 return MaybeBindToTemporary(Lambda);
1864 }
1865
BuildBlockForLambdaConversion(SourceLocation CurrentLocation,SourceLocation ConvLocation,CXXConversionDecl * Conv,Expr * Src)1866 ExprResult Sema::BuildBlockForLambdaConversion(SourceLocation CurrentLocation,
1867 SourceLocation ConvLocation,
1868 CXXConversionDecl *Conv,
1869 Expr *Src) {
1870 // Make sure that the lambda call operator is marked used.
1871 CXXRecordDecl *Lambda = Conv->getParent();
1872 CXXMethodDecl *CallOperator
1873 = cast<CXXMethodDecl>(
1874 Lambda->lookup(
1875 Context.DeclarationNames.getCXXOperatorName(OO_Call)).front());
1876 CallOperator->setReferenced();
1877 CallOperator->markUsed(Context);
1878
1879 ExprResult Init = PerformCopyInitialization(
1880 InitializedEntity::InitializeLambdaToBlock(ConvLocation, Src->getType(),
1881 /*NRVO=*/false),
1882 CurrentLocation, Src);
1883 if (!Init.isInvalid())
1884 Init = ActOnFinishFullExpr(Init.get(), /*DiscardedValue*/ false);
1885
1886 if (Init.isInvalid())
1887 return ExprError();
1888
1889 // Create the new block to be returned.
1890 BlockDecl *Block = BlockDecl::Create(Context, CurContext, ConvLocation);
1891
1892 // Set the type information.
1893 Block->setSignatureAsWritten(CallOperator->getTypeSourceInfo());
1894 Block->setIsVariadic(CallOperator->isVariadic());
1895 Block->setBlockMissingReturnType(false);
1896
1897 // Add parameters.
1898 SmallVector<ParmVarDecl *, 4> BlockParams;
1899 for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I) {
1900 ParmVarDecl *From = CallOperator->getParamDecl(I);
1901 BlockParams.push_back(ParmVarDecl::Create(
1902 Context, Block, From->getBeginLoc(), From->getLocation(),
1903 From->getIdentifier(), From->getType(), From->getTypeSourceInfo(),
1904 From->getStorageClass(),
1905 /*DefArg=*/nullptr));
1906 }
1907 Block->setParams(BlockParams);
1908
1909 Block->setIsConversionFromLambda(true);
1910
1911 // Add capture. The capture uses a fake variable, which doesn't correspond
1912 // to any actual memory location. However, the initializer copy-initializes
1913 // the lambda object.
1914 TypeSourceInfo *CapVarTSI =
1915 Context.getTrivialTypeSourceInfo(Src->getType());
1916 VarDecl *CapVar = VarDecl::Create(Context, Block, ConvLocation,
1917 ConvLocation, nullptr,
1918 Src->getType(), CapVarTSI,
1919 SC_None);
1920 BlockDecl::Capture Capture(/*variable=*/CapVar, /*byRef=*/false,
1921 /*nested=*/false, /*copy=*/Init.get());
1922 Block->setCaptures(Context, Capture, /*CapturesCXXThis=*/false);
1923
1924 // Add a fake function body to the block. IR generation is responsible
1925 // for filling in the actual body, which cannot be expressed as an AST.
1926 Block->setBody(new (Context) CompoundStmt(ConvLocation));
1927
1928 // Create the block literal expression.
1929 Expr *BuildBlock = new (Context) BlockExpr(Block, Conv->getConversionType());
1930 ExprCleanupObjects.push_back(Block);
1931 Cleanup.setExprNeedsCleanups(true);
1932
1933 return BuildBlock;
1934 }
1935