xref: /openbsd/gnu/llvm/clang/lib/Sema/SemaLambda.cpp (revision 12c85518)
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 #include <optional>
25 using namespace clang;
26 using namespace sema;
27 
28 /// Examines the FunctionScopeInfo stack to determine the nearest
29 /// enclosing lambda (to the current lambda) that is 'capture-ready' for
30 /// the variable referenced in the current lambda (i.e. \p VarToCapture).
31 /// If successful, returns the index into Sema's FunctionScopeInfo stack
32 /// of the capture-ready lambda's LambdaScopeInfo.
33 ///
34 /// Climbs down the stack of lambdas (deepest nested lambda - i.e. current
35 /// lambda - is on top) to determine the index of the nearest enclosing/outer
36 /// lambda that is ready to capture the \p VarToCapture being referenced in
37 /// the current lambda.
38 /// As we climb down the stack, we want the index of the first such lambda -
39 /// that is the lambda with the highest index that is 'capture-ready'.
40 ///
41 /// A lambda 'L' is capture-ready for 'V' (var or this) if:
42 ///  - its enclosing context is non-dependent
43 ///  - and if the chain of lambdas between L and the lambda in which
44 ///    V is potentially used (i.e. the lambda at the top of the scope info
45 ///    stack), can all capture or have already captured V.
46 /// If \p VarToCapture is 'null' then we are trying to capture 'this'.
47 ///
48 /// Note that a lambda that is deemed 'capture-ready' still needs to be checked
49 /// for whether it is 'capture-capable' (see
50 /// getStackIndexOfNearestEnclosingCaptureCapableLambda), before it can truly
51 /// capture.
52 ///
53 /// \param FunctionScopes - Sema's stack of nested FunctionScopeInfo's (which a
54 ///  LambdaScopeInfo inherits from).  The current/deepest/innermost lambda
55 ///  is at the top of the stack and has the highest index.
56 /// \param VarToCapture - the variable to capture.  If NULL, capture 'this'.
57 ///
58 /// \returns An std::optional<unsigned> Index that if evaluates to 'true'
59 /// contains the index (into Sema's FunctionScopeInfo stack) of the innermost
60 /// lambda which is capture-ready.  If the return value evaluates to 'false'
61 /// then no lambda is capture-ready for \p VarToCapture.
62 
63 static inline std::optional<unsigned>
getStackIndexOfNearestEnclosingCaptureReadyLambda(ArrayRef<const clang::sema::FunctionScopeInfo * > FunctionScopes,ValueDecl * VarToCapture)64 getStackIndexOfNearestEnclosingCaptureReadyLambda(
65     ArrayRef<const clang::sema::FunctionScopeInfo *> FunctionScopes,
66     ValueDecl *VarToCapture) {
67   // Label failure to capture.
68   const std::optional<unsigned> NoLambdaIsCaptureReady;
69 
70   // Ignore all inner captured regions.
71   unsigned CurScopeIndex = FunctionScopes.size() - 1;
72   while (CurScopeIndex > 0 && isa<clang::sema::CapturedRegionScopeInfo>(
73                                   FunctionScopes[CurScopeIndex]))
74     --CurScopeIndex;
75   assert(
76       isa<clang::sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex]) &&
77       "The function on the top of sema's function-info stack must be a lambda");
78 
79   // If VarToCapture is null, we are attempting to capture 'this'.
80   const bool IsCapturingThis = !VarToCapture;
81   const bool IsCapturingVariable = !IsCapturingThis;
82 
83   // Start with the current lambda at the top of the stack (highest index).
84   DeclContext *EnclosingDC =
85       cast<sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex])->CallOperator;
86 
87   do {
88     const clang::sema::LambdaScopeInfo *LSI =
89         cast<sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex]);
90     // IF we have climbed down to an intervening enclosing lambda that contains
91     // the variable declaration - it obviously can/must not capture the
92     // variable.
93     // Since its enclosing DC is dependent, all the lambdas between it and the
94     // innermost nested lambda are dependent (otherwise we wouldn't have
95     // arrived here) - so we don't yet have a lambda that can capture the
96     // variable.
97     if (IsCapturingVariable &&
98         VarToCapture->getDeclContext()->Equals(EnclosingDC))
99       return NoLambdaIsCaptureReady;
100 
101     // For an enclosing lambda to be capture ready for an entity, all
102     // intervening lambda's have to be able to capture that entity. If even
103     // one of the intervening lambda's is not capable of capturing the entity
104     // then no enclosing lambda can ever capture that entity.
105     // For e.g.
106     // const int x = 10;
107     // [=](auto a) {    #1
108     //   [](auto b) {   #2 <-- an intervening lambda that can never capture 'x'
109     //    [=](auto c) { #3
110     //       f(x, c);  <-- can not lead to x's speculative capture by #1 or #2
111     //    }; }; };
112     // If they do not have a default implicit capture, check to see
113     // if the entity has already been explicitly captured.
114     // If even a single dependent enclosing lambda lacks the capability
115     // to ever capture this variable, there is no further enclosing
116     // non-dependent lambda that can capture this variable.
117     if (LSI->ImpCaptureStyle == sema::LambdaScopeInfo::ImpCap_None) {
118       if (IsCapturingVariable && !LSI->isCaptured(VarToCapture))
119         return NoLambdaIsCaptureReady;
120       if (IsCapturingThis && !LSI->isCXXThisCaptured())
121         return NoLambdaIsCaptureReady;
122     }
123     EnclosingDC = getLambdaAwareParentOfDeclContext(EnclosingDC);
124 
125     assert(CurScopeIndex);
126     --CurScopeIndex;
127   } while (!EnclosingDC->isTranslationUnit() &&
128            EnclosingDC->isDependentContext() &&
129            isLambdaCallOperator(EnclosingDC));
130 
131   assert(CurScopeIndex < (FunctionScopes.size() - 1));
132   // If the enclosingDC is not dependent, then the immediately nested lambda
133   // (one index above) is capture-ready.
134   if (!EnclosingDC->isDependentContext())
135     return CurScopeIndex + 1;
136   return NoLambdaIsCaptureReady;
137 }
138 
139 /// Examines the FunctionScopeInfo stack to determine the nearest
140 /// enclosing lambda (to the current lambda) that is 'capture-capable' for
141 /// the variable referenced in the current lambda (i.e. \p VarToCapture).
142 /// If successful, returns the index into Sema's FunctionScopeInfo stack
143 /// of the capture-capable lambda's LambdaScopeInfo.
144 ///
145 /// Given the current stack of lambdas being processed by Sema and
146 /// the variable of interest, to identify the nearest enclosing lambda (to the
147 /// current lambda at the top of the stack) that can truly capture
148 /// a variable, it has to have the following two properties:
149 ///  a) 'capture-ready' - be the innermost lambda that is 'capture-ready':
150 ///     - climb down the stack (i.e. starting from the innermost and examining
151 ///       each outer lambda step by step) checking if each enclosing
152 ///       lambda can either implicitly or explicitly capture the variable.
153 ///       Record the first such lambda that is enclosed in a non-dependent
154 ///       context. If no such lambda currently exists return failure.
155 ///  b) 'capture-capable' - make sure the 'capture-ready' lambda can truly
156 ///  capture the variable by checking all its enclosing lambdas:
157 ///     - check if all outer lambdas enclosing the 'capture-ready' lambda
158 ///       identified above in 'a' can also capture the variable (this is done
159 ///       via tryCaptureVariable for variables and CheckCXXThisCapture for
160 ///       'this' by passing in the index of the Lambda identified in step 'a')
161 ///
162 /// \param FunctionScopes - Sema's stack of nested FunctionScopeInfo's (which a
163 /// LambdaScopeInfo inherits from).  The current/deepest/innermost lambda
164 /// is at the top of the stack.
165 ///
166 /// \param VarToCapture - the variable to capture.  If NULL, capture 'this'.
167 ///
168 ///
169 /// \returns An std::optional<unsigned> Index that if evaluates to 'true'
170 /// contains the index (into Sema's FunctionScopeInfo stack) of the innermost
171 /// lambda which is capture-capable.  If the return value evaluates to 'false'
172 /// then no lambda is capture-capable for \p VarToCapture.
173 
174 std::optional<unsigned>
getStackIndexOfNearestEnclosingCaptureCapableLambda(ArrayRef<const sema::FunctionScopeInfo * > FunctionScopes,ValueDecl * VarToCapture,Sema & S)175 clang::getStackIndexOfNearestEnclosingCaptureCapableLambda(
176     ArrayRef<const sema::FunctionScopeInfo *> FunctionScopes,
177     ValueDecl *VarToCapture, Sema &S) {
178 
179   const std::optional<unsigned> NoLambdaIsCaptureCapable;
180 
181   const std::optional<unsigned> OptionalStackIndex =
182       getStackIndexOfNearestEnclosingCaptureReadyLambda(FunctionScopes,
183                                                         VarToCapture);
184   if (!OptionalStackIndex)
185     return NoLambdaIsCaptureCapable;
186 
187   const unsigned IndexOfCaptureReadyLambda = *OptionalStackIndex;
188   assert(((IndexOfCaptureReadyLambda != (FunctionScopes.size() - 1)) ||
189           S.getCurGenericLambda()) &&
190          "The capture ready lambda for a potential capture can only be the "
191          "current lambda if it is a generic lambda");
192 
193   const sema::LambdaScopeInfo *const CaptureReadyLambdaLSI =
194       cast<sema::LambdaScopeInfo>(FunctionScopes[IndexOfCaptureReadyLambda]);
195 
196   // If VarToCapture is null, we are attempting to capture 'this'
197   const bool IsCapturingThis = !VarToCapture;
198   const bool IsCapturingVariable = !IsCapturingThis;
199 
200   if (IsCapturingVariable) {
201     // Check if the capture-ready lambda can truly capture the variable, by
202     // checking whether all enclosing lambdas of the capture-ready lambda allow
203     // the capture - i.e. make sure it is capture-capable.
204     QualType CaptureType, DeclRefType;
205     const bool CanCaptureVariable =
206         !S.tryCaptureVariable(VarToCapture,
207                               /*ExprVarIsUsedInLoc*/ SourceLocation(),
208                               clang::Sema::TryCapture_Implicit,
209                               /*EllipsisLoc*/ SourceLocation(),
210                               /*BuildAndDiagnose*/ false, CaptureType,
211                               DeclRefType, &IndexOfCaptureReadyLambda);
212     if (!CanCaptureVariable)
213       return NoLambdaIsCaptureCapable;
214   } else {
215     // Check if the capture-ready lambda can truly capture 'this' by checking
216     // whether all enclosing lambdas of the capture-ready lambda can capture
217     // 'this'.
218     const bool CanCaptureThis =
219         !S.CheckCXXThisCapture(
220              CaptureReadyLambdaLSI->PotentialThisCaptureLocation,
221              /*Explicit*/ false, /*BuildAndDiagnose*/ false,
222              &IndexOfCaptureReadyLambda);
223     if (!CanCaptureThis)
224       return NoLambdaIsCaptureCapable;
225   }
226   return IndexOfCaptureReadyLambda;
227 }
228 
229 static inline TemplateParameterList *
getGenericLambdaTemplateParameterList(LambdaScopeInfo * LSI,Sema & SemaRef)230 getGenericLambdaTemplateParameterList(LambdaScopeInfo *LSI, Sema &SemaRef) {
231   if (!LSI->GLTemplateParameterList && !LSI->TemplateParams.empty()) {
232     LSI->GLTemplateParameterList = TemplateParameterList::Create(
233         SemaRef.Context,
234         /*Template kw loc*/ SourceLocation(),
235         /*L angle loc*/ LSI->ExplicitTemplateParamsRange.getBegin(),
236         LSI->TemplateParams,
237         /*R angle loc*/LSI->ExplicitTemplateParamsRange.getEnd(),
238         LSI->RequiresClause.get());
239   }
240   return LSI->GLTemplateParameterList;
241 }
242 
243 CXXRecordDecl *
createLambdaClosureType(SourceRange IntroducerRange,TypeSourceInfo * Info,unsigned LambdaDependencyKind,LambdaCaptureDefault CaptureDefault)244 Sema::createLambdaClosureType(SourceRange IntroducerRange, TypeSourceInfo *Info,
245                               unsigned LambdaDependencyKind,
246                               LambdaCaptureDefault CaptureDefault) {
247   DeclContext *DC = CurContext;
248   while (!(DC->isFunctionOrMethod() || DC->isRecord() || DC->isFileContext()))
249     DC = DC->getParent();
250   bool IsGenericLambda = getGenericLambdaTemplateParameterList(getCurLambda(),
251                                                                *this);
252   // Start constructing the lambda class.
253   CXXRecordDecl *Class = CXXRecordDecl::CreateLambda(
254       Context, DC, Info, IntroducerRange.getBegin(), LambdaDependencyKind,
255       IsGenericLambda, 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     Concept
289   } Kind = Normal;
290 
291   // Default arguments of member function parameters that appear in a class
292   // definition, as well as the initializers of data members, receive special
293   // treatment. Identify them.
294   if (ManglingContextDecl) {
295     if (ParmVarDecl *Param = dyn_cast<ParmVarDecl>(ManglingContextDecl)) {
296       if (const DeclContext *LexicalDC
297           = Param->getDeclContext()->getLexicalParent())
298         if (LexicalDC->isRecord())
299           Kind = DefaultArgument;
300     } else if (VarDecl *Var = dyn_cast<VarDecl>(ManglingContextDecl)) {
301       if (Var->getDeclContext()->isRecord())
302         Kind = StaticDataMember;
303       else if (Var->getMostRecentDecl()->isInline())
304         Kind = InlineVariable;
305       else if (Var->getDescribedVarTemplate())
306         Kind = VariableTemplate;
307       else if (auto *VTS = dyn_cast<VarTemplateSpecializationDecl>(Var)) {
308         if (!VTS->isExplicitSpecialization())
309           Kind = VariableTemplate;
310       }
311     } else if (isa<FieldDecl>(ManglingContextDecl)) {
312       Kind = DataMember;
313     } else if (isa<ImplicitConceptSpecializationDecl>(ManglingContextDecl)) {
314       Kind = Concept;
315     }
316   }
317 
318   // Itanium ABI [5.1.7]:
319   //   In the following contexts [...] the one-definition rule requires closure
320   //   types in different translation units to "correspond":
321   bool IsInNonspecializedTemplate =
322       inTemplateInstantiation() || CurContext->isDependentContext();
323   switch (Kind) {
324   case Normal: {
325     //  -- the bodies of non-exported nonspecialized template functions
326     //  -- the bodies of inline functions
327     if ((IsInNonspecializedTemplate &&
328          !(ManglingContextDecl && isa<ParmVarDecl>(ManglingContextDecl))) ||
329         isInInlineFunction(CurContext)) {
330       while (auto *CD = dyn_cast<CapturedDecl>(DC))
331         DC = CD->getParent();
332       return std::make_tuple(&Context.getManglingNumberContext(DC), nullptr);
333     }
334 
335     return std::make_tuple(nullptr, nullptr);
336   }
337 
338   case Concept:
339     // Concept definitions aren't code generated and thus aren't mangled,
340     // however the ManglingContextDecl is important for the purposes of
341     // re-forming the template argument list of the lambda for constraint
342     // evaluation.
343   case StaticDataMember:
344     //  -- the initializers of nonspecialized static members of template classes
345     if (!IsInNonspecializedTemplate)
346       return std::make_tuple(nullptr, ManglingContextDecl);
347     // Fall through to get the current context.
348     [[fallthrough]];
349 
350   case DataMember:
351     //  -- the in-class initializers of class members
352   case DefaultArgument:
353     //  -- default arguments appearing in class definitions
354   case InlineVariable:
355     //  -- the initializers of inline variables
356   case VariableTemplate:
357     //  -- the initializers of templated variables
358     return std::make_tuple(
359         &Context.getManglingNumberContext(ASTContext::NeedExtraManglingDecl,
360                                           ManglingContextDecl),
361         ManglingContextDecl);
362   }
363 
364   llvm_unreachable("unexpected context");
365 }
366 
startLambdaDefinition(CXXRecordDecl * Class,SourceRange IntroducerRange,TypeSourceInfo * MethodTypeInfo,SourceLocation EndLoc,ArrayRef<ParmVarDecl * > Params,ConstexprSpecKind ConstexprKind,StorageClass SC,Expr * TrailingRequiresClause)367 CXXMethodDecl *Sema::startLambdaDefinition(
368     CXXRecordDecl *Class, SourceRange IntroducerRange,
369     TypeSourceInfo *MethodTypeInfo, SourceLocation EndLoc,
370     ArrayRef<ParmVarDecl *> Params, ConstexprSpecKind ConstexprKind,
371     StorageClass SC, Expr *TrailingRequiresClause) {
372   QualType MethodType = MethodTypeInfo->getType();
373   TemplateParameterList *TemplateParams =
374       getGenericLambdaTemplateParameterList(getCurLambda(), *this);
375   // If a lambda appears in a dependent context or is a generic lambda (has
376   // template parameters) and has an 'auto' return type, deduce it to a
377   // dependent type.
378   if (Class->isDependentContext() || TemplateParams) {
379     const FunctionProtoType *FPT = MethodType->castAs<FunctionProtoType>();
380     QualType Result = FPT->getReturnType();
381     if (Result->isUndeducedType()) {
382       Result = SubstAutoTypeDependent(Result);
383       MethodType = Context.getFunctionType(Result, FPT->getParamTypes(),
384                                            FPT->getExtProtoInfo());
385     }
386   }
387 
388   // C++11 [expr.prim.lambda]p5:
389   //   The closure type for a lambda-expression has a public inline function
390   //   call operator (13.5.4) whose parameters and return type are described by
391   //   the lambda-expression's parameter-declaration-clause and
392   //   trailing-return-type respectively.
393   DeclarationName MethodName
394     = Context.DeclarationNames.getCXXOperatorName(OO_Call);
395   DeclarationNameLoc MethodNameLoc =
396       DeclarationNameLoc::makeCXXOperatorNameLoc(IntroducerRange);
397   CXXMethodDecl *Method = CXXMethodDecl::Create(
398       Context, Class, EndLoc,
399       DeclarationNameInfo(MethodName, IntroducerRange.getBegin(),
400                           MethodNameLoc),
401       MethodType, MethodTypeInfo, SC, getCurFPFeatures().isFPConstrained(),
402       /*isInline=*/true, ConstexprKind, EndLoc, TrailingRequiresClause);
403   Method->setAccess(AS_public);
404   if (!TemplateParams)
405     Class->addDecl(Method);
406 
407   // Temporarily set the lexical declaration context to the current
408   // context, so that the Scope stack matches the lexical nesting.
409   Method->setLexicalDeclContext(CurContext);
410   // Create a function template if we have a template parameter list
411   FunctionTemplateDecl *const TemplateMethod = TemplateParams ?
412             FunctionTemplateDecl::Create(Context, Class,
413                                          Method->getLocation(), MethodName,
414                                          TemplateParams,
415                                          Method) : nullptr;
416   if (TemplateMethod) {
417     TemplateMethod->setAccess(AS_public);
418     Method->setDescribedFunctionTemplate(TemplateMethod);
419     Class->addDecl(TemplateMethod);
420     TemplateMethod->setLexicalDeclContext(CurContext);
421   }
422 
423   // Add parameters.
424   if (!Params.empty()) {
425     Method->setParams(Params);
426     CheckParmsForFunctionDef(Params,
427                              /*CheckParameterNames=*/false);
428 
429     for (auto *P : Method->parameters())
430       P->setOwningFunction(Method);
431   }
432 
433   return Method;
434 }
435 
handleLambdaNumbering(CXXRecordDecl * Class,CXXMethodDecl * Method,std::optional<std::tuple<bool,unsigned,unsigned,Decl * >> Mangling)436 void Sema::handleLambdaNumbering(
437     CXXRecordDecl *Class, CXXMethodDecl *Method,
438     std::optional<std::tuple<bool, unsigned, unsigned, Decl *>> Mangling) {
439   if (Mangling) {
440     bool HasKnownInternalLinkage;
441     unsigned ManglingNumber, DeviceManglingNumber;
442     Decl *ManglingContextDecl;
443     std::tie(HasKnownInternalLinkage, ManglingNumber, DeviceManglingNumber,
444              ManglingContextDecl) = *Mangling;
445     Class->setLambdaMangling(ManglingNumber, ManglingContextDecl,
446                              HasKnownInternalLinkage);
447     Class->setDeviceLambdaManglingNumber(DeviceManglingNumber);
448     return;
449   }
450 
451   auto getMangleNumberingContext =
452       [this](CXXRecordDecl *Class,
453              Decl *ManglingContextDecl) -> MangleNumberingContext * {
454     // Get mangle numbering context if there's any extra decl context.
455     if (ManglingContextDecl)
456       return &Context.getManglingNumberContext(
457           ASTContext::NeedExtraManglingDecl, ManglingContextDecl);
458     // Otherwise, from that lambda's decl context.
459     auto DC = Class->getDeclContext();
460     while (auto *CD = dyn_cast<CapturedDecl>(DC))
461       DC = CD->getParent();
462     return &Context.getManglingNumberContext(DC);
463   };
464 
465   MangleNumberingContext *MCtx;
466   Decl *ManglingContextDecl;
467   std::tie(MCtx, ManglingContextDecl) =
468       getCurrentMangleNumberContext(Class->getDeclContext());
469   bool HasKnownInternalLinkage = false;
470   if (!MCtx && (getLangOpts().CUDA || getLangOpts().SYCLIsDevice ||
471                 getLangOpts().SYCLIsHost)) {
472     // Force lambda numbering in CUDA/HIP as we need to name lambdas following
473     // ODR. Both device- and host-compilation need to have a consistent naming
474     // on kernel functions. As lambdas are potential part of these `__global__`
475     // function names, they needs numbering following ODR.
476     // Also force for SYCL, since we need this for the
477     // __builtin_sycl_unique_stable_name implementation, which depends on lambda
478     // mangling.
479     MCtx = getMangleNumberingContext(Class, ManglingContextDecl);
480     assert(MCtx && "Retrieving mangle numbering context failed!");
481     HasKnownInternalLinkage = true;
482   }
483   if (MCtx) {
484     unsigned ManglingNumber = MCtx->getManglingNumber(Method);
485     Class->setLambdaMangling(ManglingNumber, ManglingContextDecl,
486                              HasKnownInternalLinkage);
487     Class->setDeviceLambdaManglingNumber(MCtx->getDeviceManglingNumber(Method));
488   }
489 }
490 
buildLambdaScope(LambdaScopeInfo * LSI,CXXMethodDecl * CallOperator,SourceRange IntroducerRange,LambdaCaptureDefault CaptureDefault,SourceLocation CaptureDefaultLoc,bool ExplicitParams,bool ExplicitResultType,bool Mutable)491 void Sema::buildLambdaScope(LambdaScopeInfo *LSI,
492                                         CXXMethodDecl *CallOperator,
493                                         SourceRange IntroducerRange,
494                                         LambdaCaptureDefault CaptureDefault,
495                                         SourceLocation CaptureDefaultLoc,
496                                         bool ExplicitParams,
497                                         bool ExplicitResultType,
498                                         bool Mutable) {
499   LSI->CallOperator = CallOperator;
500   CXXRecordDecl *LambdaClass = CallOperator->getParent();
501   LSI->Lambda = LambdaClass;
502   if (CaptureDefault == LCD_ByCopy)
503     LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByval;
504   else if (CaptureDefault == LCD_ByRef)
505     LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByref;
506   LSI->CaptureDefaultLoc = CaptureDefaultLoc;
507   LSI->IntroducerRange = IntroducerRange;
508   LSI->ExplicitParams = ExplicitParams;
509   LSI->Mutable = Mutable;
510 
511   if (ExplicitResultType) {
512     LSI->ReturnType = CallOperator->getReturnType();
513 
514     if (!LSI->ReturnType->isDependentType() &&
515         !LSI->ReturnType->isVoidType()) {
516       if (RequireCompleteType(CallOperator->getBeginLoc(), LSI->ReturnType,
517                               diag::err_lambda_incomplete_result)) {
518         // Do nothing.
519       }
520     }
521   } else {
522     LSI->HasImplicitReturnType = true;
523   }
524 }
525 
finishLambdaExplicitCaptures(LambdaScopeInfo * LSI)526 void Sema::finishLambdaExplicitCaptures(LambdaScopeInfo *LSI) {
527   LSI->finishedExplicitCaptures();
528 }
529 
ActOnLambdaExplicitTemplateParameterList(SourceLocation LAngleLoc,ArrayRef<NamedDecl * > TParams,SourceLocation RAngleLoc,ExprResult RequiresClause)530 void Sema::ActOnLambdaExplicitTemplateParameterList(SourceLocation LAngleLoc,
531                                                     ArrayRef<NamedDecl *> TParams,
532                                                     SourceLocation RAngleLoc,
533                                                     ExprResult RequiresClause) {
534   LambdaScopeInfo *LSI = getCurLambda();
535   assert(LSI && "Expected a lambda scope");
536   assert(LSI->NumExplicitTemplateParams == 0 &&
537          "Already acted on explicit template parameters");
538   assert(LSI->TemplateParams.empty() &&
539          "Explicit template parameters should come "
540          "before invented (auto) ones");
541   assert(!TParams.empty() &&
542          "No template parameters to act on");
543   LSI->TemplateParams.append(TParams.begin(), TParams.end());
544   LSI->NumExplicitTemplateParams = TParams.size();
545   LSI->ExplicitTemplateParamsRange = {LAngleLoc, RAngleLoc};
546   LSI->RequiresClause = RequiresClause;
547 }
548 
addLambdaParameters(ArrayRef<LambdaIntroducer::LambdaCapture> Captures,CXXMethodDecl * CallOperator,Scope * CurScope)549 void Sema::addLambdaParameters(
550     ArrayRef<LambdaIntroducer::LambdaCapture> Captures,
551     CXXMethodDecl *CallOperator, Scope *CurScope) {
552   // Introduce our parameters into the function scope
553   for (unsigned p = 0, NumParams = CallOperator->getNumParams();
554        p < NumParams; ++p) {
555     ParmVarDecl *Param = CallOperator->getParamDecl(p);
556 
557     // If this has an identifier, add it to the scope stack.
558     if (CurScope && Param->getIdentifier()) {
559       bool Error = false;
560       // Resolution of CWG 2211 in C++17 renders shadowing ill-formed, but we
561       // retroactively apply it.
562       for (const auto &Capture : Captures) {
563         if (Capture.Id == Param->getIdentifier()) {
564           Error = true;
565           Diag(Param->getLocation(), diag::err_parameter_shadow_capture);
566           Diag(Capture.Loc, diag::note_var_explicitly_captured_here)
567               << Capture.Id << true;
568         }
569       }
570       if (!Error)
571         CheckShadow(CurScope, Param);
572 
573       PushOnScopeChains(Param, CurScope);
574     }
575   }
576 }
577 
578 /// If this expression is an enumerator-like expression of some type
579 /// T, return the type T; otherwise, return null.
580 ///
581 /// Pointer comparisons on the result here should always work because
582 /// it's derived from either the parent of an EnumConstantDecl
583 /// (i.e. the definition) or the declaration returned by
584 /// EnumType::getDecl() (i.e. the definition).
findEnumForBlockReturn(Expr * E)585 static EnumDecl *findEnumForBlockReturn(Expr *E) {
586   // An expression is an enumerator-like expression of type T if,
587   // ignoring parens and parens-like expressions:
588   E = E->IgnoreParens();
589 
590   //  - it is an enumerator whose enum type is T or
591   if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
592     if (EnumConstantDecl *D
593           = dyn_cast<EnumConstantDecl>(DRE->getDecl())) {
594       return cast<EnumDecl>(D->getDeclContext());
595     }
596     return nullptr;
597   }
598 
599   //  - it is a comma expression whose RHS is an enumerator-like
600   //    expression of type T or
601   if (BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
602     if (BO->getOpcode() == BO_Comma)
603       return findEnumForBlockReturn(BO->getRHS());
604     return nullptr;
605   }
606 
607   //  - it is a statement-expression whose value expression is an
608   //    enumerator-like expression of type T or
609   if (StmtExpr *SE = dyn_cast<StmtExpr>(E)) {
610     if (Expr *last = dyn_cast_or_null<Expr>(SE->getSubStmt()->body_back()))
611       return findEnumForBlockReturn(last);
612     return nullptr;
613   }
614 
615   //   - it is a ternary conditional operator (not the GNU ?:
616   //     extension) whose second and third operands are
617   //     enumerator-like expressions of type T or
618   if (ConditionalOperator *CO = dyn_cast<ConditionalOperator>(E)) {
619     if (EnumDecl *ED = findEnumForBlockReturn(CO->getTrueExpr()))
620       if (ED == findEnumForBlockReturn(CO->getFalseExpr()))
621         return ED;
622     return nullptr;
623   }
624 
625   // (implicitly:)
626   //   - it is an implicit integral conversion applied to an
627   //     enumerator-like expression of type T or
628   if (ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(E)) {
629     // We can sometimes see integral conversions in valid
630     // enumerator-like expressions.
631     if (ICE->getCastKind() == CK_IntegralCast)
632       return findEnumForBlockReturn(ICE->getSubExpr());
633 
634     // Otherwise, just rely on the type.
635   }
636 
637   //   - it is an expression of that formal enum type.
638   if (const EnumType *ET = E->getType()->getAs<EnumType>()) {
639     return ET->getDecl();
640   }
641 
642   // Otherwise, nope.
643   return nullptr;
644 }
645 
646 /// Attempt to find a type T for which the returned expression of the
647 /// given statement is an enumerator-like expression of that type.
findEnumForBlockReturn(ReturnStmt * ret)648 static EnumDecl *findEnumForBlockReturn(ReturnStmt *ret) {
649   if (Expr *retValue = ret->getRetValue())
650     return findEnumForBlockReturn(retValue);
651   return nullptr;
652 }
653 
654 /// Attempt to find a common type T for which all of the returned
655 /// expressions in a block are enumerator-like expressions of that
656 /// type.
findCommonEnumForBlockReturns(ArrayRef<ReturnStmt * > returns)657 static EnumDecl *findCommonEnumForBlockReturns(ArrayRef<ReturnStmt*> returns) {
658   ArrayRef<ReturnStmt*>::iterator i = returns.begin(), e = returns.end();
659 
660   // Try to find one for the first return.
661   EnumDecl *ED = findEnumForBlockReturn(*i);
662   if (!ED) return nullptr;
663 
664   // Check that the rest of the returns have the same enum.
665   for (++i; i != e; ++i) {
666     if (findEnumForBlockReturn(*i) != ED)
667       return nullptr;
668   }
669 
670   // Never infer an anonymous enum type.
671   if (!ED->hasNameForLinkage()) return nullptr;
672 
673   return ED;
674 }
675 
676 /// Adjust the given return statements so that they formally return
677 /// the given type.  It should require, at most, an IntegralCast.
adjustBlockReturnsToEnum(Sema & S,ArrayRef<ReturnStmt * > returns,QualType returnType)678 static void adjustBlockReturnsToEnum(Sema &S, ArrayRef<ReturnStmt*> returns,
679                                      QualType returnType) {
680   for (ArrayRef<ReturnStmt*>::iterator
681          i = returns.begin(), e = returns.end(); i != e; ++i) {
682     ReturnStmt *ret = *i;
683     Expr *retValue = ret->getRetValue();
684     if (S.Context.hasSameType(retValue->getType(), returnType))
685       continue;
686 
687     // Right now we only support integral fixup casts.
688     assert(returnType->isIntegralOrUnscopedEnumerationType());
689     assert(retValue->getType()->isIntegralOrUnscopedEnumerationType());
690 
691     ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(retValue);
692 
693     Expr *E = (cleanups ? cleanups->getSubExpr() : retValue);
694     E = ImplicitCastExpr::Create(S.Context, returnType, CK_IntegralCast, E,
695                                  /*base path*/ nullptr, VK_PRValue,
696                                  FPOptionsOverride());
697     if (cleanups) {
698       cleanups->setSubExpr(E);
699     } else {
700       ret->setRetValue(E);
701     }
702   }
703 }
704 
deduceClosureReturnType(CapturingScopeInfo & CSI)705 void Sema::deduceClosureReturnType(CapturingScopeInfo &CSI) {
706   assert(CSI.HasImplicitReturnType);
707   // If it was ever a placeholder, it had to been deduced to DependentTy.
708   assert(CSI.ReturnType.isNull() || !CSI.ReturnType->isUndeducedType());
709   assert((!isa<LambdaScopeInfo>(CSI) || !getLangOpts().CPlusPlus14) &&
710          "lambda expressions use auto deduction in C++14 onwards");
711 
712   // C++ core issue 975:
713   //   If a lambda-expression does not include a trailing-return-type,
714   //   it is as if the trailing-return-type denotes the following type:
715   //     - if there are no return statements in the compound-statement,
716   //       or all return statements return either an expression of type
717   //       void or no expression or braced-init-list, the type void;
718   //     - otherwise, if all return statements return an expression
719   //       and the types of the returned expressions after
720   //       lvalue-to-rvalue conversion (4.1 [conv.lval]),
721   //       array-to-pointer conversion (4.2 [conv.array]), and
722   //       function-to-pointer conversion (4.3 [conv.func]) are the
723   //       same, that common type;
724   //     - otherwise, the program is ill-formed.
725   //
726   // C++ core issue 1048 additionally removes top-level cv-qualifiers
727   // from the types of returned expressions to match the C++14 auto
728   // deduction rules.
729   //
730   // In addition, in blocks in non-C++ modes, if all of the return
731   // statements are enumerator-like expressions of some type T, where
732   // T has a name for linkage, then we infer the return type of the
733   // block to be that type.
734 
735   // First case: no return statements, implicit void return type.
736   ASTContext &Ctx = getASTContext();
737   if (CSI.Returns.empty()) {
738     // It's possible there were simply no /valid/ return statements.
739     // In this case, the first one we found may have at least given us a type.
740     if (CSI.ReturnType.isNull())
741       CSI.ReturnType = Ctx.VoidTy;
742     return;
743   }
744 
745   // Second case: at least one return statement has dependent type.
746   // Delay type checking until instantiation.
747   assert(!CSI.ReturnType.isNull() && "We should have a tentative return type.");
748   if (CSI.ReturnType->isDependentType())
749     return;
750 
751   // Try to apply the enum-fuzz rule.
752   if (!getLangOpts().CPlusPlus) {
753     assert(isa<BlockScopeInfo>(CSI));
754     const EnumDecl *ED = findCommonEnumForBlockReturns(CSI.Returns);
755     if (ED) {
756       CSI.ReturnType = Context.getTypeDeclType(ED);
757       adjustBlockReturnsToEnum(*this, CSI.Returns, CSI.ReturnType);
758       return;
759     }
760   }
761 
762   // Third case: only one return statement. Don't bother doing extra work!
763   if (CSI.Returns.size() == 1)
764     return;
765 
766   // General case: many return statements.
767   // Check that they all have compatible return types.
768 
769   // We require the return types to strictly match here.
770   // Note that we've already done the required promotions as part of
771   // processing the return statement.
772   for (const ReturnStmt *RS : CSI.Returns) {
773     const Expr *RetE = RS->getRetValue();
774 
775     QualType ReturnType =
776         (RetE ? RetE->getType() : Context.VoidTy).getUnqualifiedType();
777     if (Context.getCanonicalFunctionResultType(ReturnType) ==
778           Context.getCanonicalFunctionResultType(CSI.ReturnType)) {
779       // Use the return type with the strictest possible nullability annotation.
780       auto RetTyNullability = ReturnType->getNullability();
781       auto BlockNullability = CSI.ReturnType->getNullability();
782       if (BlockNullability &&
783           (!RetTyNullability ||
784            hasWeakerNullability(*RetTyNullability, *BlockNullability)))
785         CSI.ReturnType = ReturnType;
786       continue;
787     }
788 
789     // FIXME: This is a poor diagnostic for ReturnStmts without expressions.
790     // TODO: It's possible that the *first* return is the divergent one.
791     Diag(RS->getBeginLoc(),
792          diag::err_typecheck_missing_return_type_incompatible)
793         << ReturnType << CSI.ReturnType << isa<LambdaScopeInfo>(CSI);
794     // Continue iterating so that we keep emitting diagnostics.
795   }
796 }
797 
buildLambdaInitCaptureInitialization(SourceLocation Loc,bool ByRef,SourceLocation EllipsisLoc,std::optional<unsigned> NumExpansions,IdentifierInfo * Id,bool IsDirectInit,Expr * & Init)798 QualType Sema::buildLambdaInitCaptureInitialization(
799     SourceLocation Loc, bool ByRef, SourceLocation EllipsisLoc,
800     std::optional<unsigned> NumExpansions, IdentifierInfo *Id,
801     bool IsDirectInit, Expr *&Init) {
802   // Create an 'auto' or 'auto&' TypeSourceInfo that we can use to
803   // deduce against.
804   QualType DeductType = Context.getAutoDeductType();
805   TypeLocBuilder TLB;
806   AutoTypeLoc TL = TLB.push<AutoTypeLoc>(DeductType);
807   TL.setNameLoc(Loc);
808   if (ByRef) {
809     DeductType = BuildReferenceType(DeductType, true, Loc, Id);
810     assert(!DeductType.isNull() && "can't build reference to auto");
811     TLB.push<ReferenceTypeLoc>(DeductType).setSigilLoc(Loc);
812   }
813   if (EllipsisLoc.isValid()) {
814     if (Init->containsUnexpandedParameterPack()) {
815       Diag(EllipsisLoc, getLangOpts().CPlusPlus20
816                             ? diag::warn_cxx17_compat_init_capture_pack
817                             : diag::ext_init_capture_pack);
818       DeductType = Context.getPackExpansionType(DeductType, NumExpansions,
819                                                 /*ExpectPackInType=*/false);
820       TLB.push<PackExpansionTypeLoc>(DeductType).setEllipsisLoc(EllipsisLoc);
821     } else {
822       // Just ignore the ellipsis for now and form a non-pack variable. We'll
823       // diagnose this later when we try to capture it.
824     }
825   }
826   TypeSourceInfo *TSI = TLB.getTypeSourceInfo(Context, DeductType);
827 
828   // Deduce the type of the init capture.
829   QualType DeducedType = deduceVarTypeFromInitializer(
830       /*VarDecl*/nullptr, DeclarationName(Id), DeductType, TSI,
831       SourceRange(Loc, Loc), IsDirectInit, Init);
832   if (DeducedType.isNull())
833     return QualType();
834 
835   // Are we a non-list direct initialization?
836   ParenListExpr *CXXDirectInit = dyn_cast<ParenListExpr>(Init);
837 
838   // Perform initialization analysis and ensure any implicit conversions
839   // (such as lvalue-to-rvalue) are enforced.
840   InitializedEntity Entity =
841       InitializedEntity::InitializeLambdaCapture(Id, DeducedType, Loc);
842   InitializationKind Kind =
843       IsDirectInit
844           ? (CXXDirectInit ? InitializationKind::CreateDirect(
845                                  Loc, Init->getBeginLoc(), Init->getEndLoc())
846                            : InitializationKind::CreateDirectList(Loc))
847           : InitializationKind::CreateCopy(Loc, Init->getBeginLoc());
848 
849   MultiExprArg Args = Init;
850   if (CXXDirectInit)
851     Args =
852         MultiExprArg(CXXDirectInit->getExprs(), CXXDirectInit->getNumExprs());
853   QualType DclT;
854   InitializationSequence InitSeq(*this, Entity, Kind, Args);
855   ExprResult Result = InitSeq.Perform(*this, Entity, Kind, Args, &DclT);
856 
857   if (Result.isInvalid())
858     return QualType();
859 
860   Init = Result.getAs<Expr>();
861   return DeducedType;
862 }
863 
createLambdaInitCaptureVarDecl(SourceLocation Loc,QualType InitCaptureType,SourceLocation EllipsisLoc,IdentifierInfo * Id,unsigned InitStyle,Expr * Init)864 VarDecl *Sema::createLambdaInitCaptureVarDecl(SourceLocation Loc,
865                                               QualType InitCaptureType,
866                                               SourceLocation EllipsisLoc,
867                                               IdentifierInfo *Id,
868                                               unsigned InitStyle, Expr *Init) {
869   // FIXME: Retain the TypeSourceInfo from buildLambdaInitCaptureInitialization
870   // rather than reconstructing it here.
871   TypeSourceInfo *TSI = Context.getTrivialTypeSourceInfo(InitCaptureType, Loc);
872   if (auto PETL = TSI->getTypeLoc().getAs<PackExpansionTypeLoc>())
873     PETL.setEllipsisLoc(EllipsisLoc);
874 
875   // Create a dummy variable representing the init-capture. This is not actually
876   // used as a variable, and only exists as a way to name and refer to the
877   // init-capture.
878   // FIXME: Pass in separate source locations for '&' and identifier.
879   VarDecl *NewVD = VarDecl::Create(Context, CurContext, Loc,
880                                    Loc, Id, InitCaptureType, TSI, SC_Auto);
881   NewVD->setInitCapture(true);
882   NewVD->setReferenced(true);
883   // FIXME: Pass in a VarDecl::InitializationStyle.
884   NewVD->setInitStyle(static_cast<VarDecl::InitializationStyle>(InitStyle));
885   NewVD->markUsed(Context);
886   NewVD->setInit(Init);
887   if (NewVD->isParameterPack())
888     getCurLambda()->LocalPacks.push_back(NewVD);
889   return NewVD;
890 }
891 
addInitCapture(LambdaScopeInfo * LSI,VarDecl * Var,bool isReferenceType)892 void Sema::addInitCapture(LambdaScopeInfo *LSI, VarDecl *Var,
893                           bool isReferenceType) {
894   assert(Var->isInitCapture() && "init capture flag should be set");
895   LSI->addCapture(Var, /*isBlock*/ false, isReferenceType,
896                   /*isNested*/ false, Var->getLocation(), SourceLocation(),
897                   Var->getType(), /*Invalid*/ false);
898 }
899 
ActOnStartOfLambdaDefinition(LambdaIntroducer & Intro,Declarator & ParamInfo,Scope * CurScope)900 void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
901                                         Declarator &ParamInfo,
902                                         Scope *CurScope) {
903   LambdaScopeInfo *const LSI = getCurLambda();
904   assert(LSI && "LambdaScopeInfo should be on stack!");
905 
906   // Determine if we're within a context where we know that the lambda will
907   // be dependent, because there are template parameters in scope.
908   CXXRecordDecl::LambdaDependencyKind LambdaDependencyKind =
909       CXXRecordDecl::LDK_Unknown;
910   if (LSI->NumExplicitTemplateParams > 0) {
911     auto *TemplateParamScope = CurScope->getTemplateParamParent();
912     assert(TemplateParamScope &&
913            "Lambda with explicit template param list should establish a "
914            "template param scope");
915     assert(TemplateParamScope->getParent());
916     if (TemplateParamScope->getParent()->getTemplateParamParent() != nullptr)
917       LambdaDependencyKind = CXXRecordDecl::LDK_AlwaysDependent;
918   } else if (CurScope->getTemplateParamParent() != nullptr) {
919     LambdaDependencyKind = CXXRecordDecl::LDK_AlwaysDependent;
920   }
921 
922   // Determine the signature of the call operator.
923   TypeSourceInfo *MethodTyInfo;
924   bool ExplicitParams = true;
925   bool ExplicitResultType = true;
926   bool ContainsUnexpandedParameterPack = false;
927   SourceLocation EndLoc;
928   SmallVector<ParmVarDecl *, 8> Params;
929 
930   assert(
931       (ParamInfo.getDeclSpec().getStorageClassSpec() ==
932            DeclSpec::SCS_unspecified ||
933        ParamInfo.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_static) &&
934       "Unexpected storage specifier");
935   bool IsLambdaStatic =
936       ParamInfo.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_static;
937 
938   if (ParamInfo.getNumTypeObjects() == 0) {
939     // C++11 [expr.prim.lambda]p4:
940     //   If a lambda-expression does not include a lambda-declarator, it is as
941     //   if the lambda-declarator were ().
942     FunctionProtoType::ExtProtoInfo EPI(Context.getDefaultCallingConvention(
943         /*IsVariadic=*/false, /*IsCXXMethod=*/true));
944     EPI.HasTrailingReturn = true;
945     EPI.TypeQuals.addConst();
946     LangAS AS = getDefaultCXXMethodAddrSpace();
947     if (AS != LangAS::Default)
948       EPI.TypeQuals.addAddressSpace(AS);
949 
950     // C++1y [expr.prim.lambda]:
951     //   The lambda return type is 'auto', which is replaced by the
952     //   trailing-return type if provided and/or deduced from 'return'
953     //   statements
954     // We don't do this before C++1y, because we don't support deduced return
955     // types there.
956     QualType DefaultTypeForNoTrailingReturn =
957         getLangOpts().CPlusPlus14 ? Context.getAutoDeductType()
958                                   : Context.DependentTy;
959     QualType MethodTy = Context.getFunctionType(DefaultTypeForNoTrailingReturn,
960                                                 std::nullopt, EPI);
961     MethodTyInfo = Context.getTrivialTypeSourceInfo(MethodTy);
962     ExplicitParams = false;
963     ExplicitResultType = false;
964     EndLoc = Intro.Range.getEnd();
965   } else {
966     assert(ParamInfo.isFunctionDeclarator() &&
967            "lambda-declarator is a function");
968     DeclaratorChunk::FunctionTypeInfo &FTI = ParamInfo.getFunctionTypeInfo();
969 
970     // C++11 [expr.prim.lambda]p5:
971     //   This function call operator is declared const (9.3.1) if and only if
972     //   the lambda-expression's parameter-declaration-clause is not followed
973     //   by mutable. It is neither virtual nor declared volatile. [...]
974     if (!FTI.hasMutableQualifier() && !IsLambdaStatic) {
975       FTI.getOrCreateMethodQualifiers().SetTypeQual(DeclSpec::TQ_const,
976                                                     SourceLocation());
977     }
978 
979     MethodTyInfo = GetTypeForDeclarator(ParamInfo, CurScope);
980     assert(MethodTyInfo && "no type from lambda-declarator");
981     EndLoc = ParamInfo.getSourceRange().getEnd();
982 
983     ExplicitResultType = FTI.hasTrailingReturnType();
984 
985     if (ExplicitResultType && getLangOpts().HLSL) {
986       QualType RetTy = FTI.getTrailingReturnType().get();
987       if (!RetTy.isNull()) {
988         // HLSL does not support specifying an address space on a lambda return
989         // type.
990         LangAS AddressSpace = RetTy.getAddressSpace();
991         if (AddressSpace != LangAS::Default)
992           Diag(FTI.getTrailingReturnTypeLoc(),
993                diag::err_return_value_with_address_space);
994       }
995     }
996 
997     if (FTIHasNonVoidParameters(FTI)) {
998       Params.reserve(FTI.NumParams);
999       for (unsigned i = 0, e = FTI.NumParams; i != e; ++i)
1000         Params.push_back(cast<ParmVarDecl>(FTI.Params[i].Param));
1001     }
1002 
1003     // Check for unexpanded parameter packs in the method type.
1004     if (MethodTyInfo->getType()->containsUnexpandedParameterPack())
1005       DiagnoseUnexpandedParameterPack(Intro.Range.getBegin(), MethodTyInfo,
1006                                       UPPC_DeclarationType);
1007   }
1008 
1009   CXXRecordDecl *Class = createLambdaClosureType(
1010       Intro.Range, MethodTyInfo, LambdaDependencyKind, Intro.Default);
1011   CXXMethodDecl *Method =
1012       startLambdaDefinition(Class, Intro.Range, MethodTyInfo, EndLoc, Params,
1013                             ParamInfo.getDeclSpec().getConstexprSpecifier(),
1014                             IsLambdaStatic ? SC_Static : SC_None,
1015                             ParamInfo.getTrailingRequiresClause());
1016   if (ExplicitParams)
1017     CheckCXXDefaultArguments(Method);
1018 
1019   // This represents the function body for the lambda function, check if we
1020   // have to apply optnone due to a pragma.
1021   AddRangeBasedOptnone(Method);
1022 
1023   // code_seg attribute on lambda apply to the method.
1024   if (Attr *A = getImplicitCodeSegOrSectionAttrForFunction(Method, /*IsDefinition=*/true))
1025     Method->addAttr(A);
1026 
1027   // Attributes on the lambda apply to the method.
1028   ProcessDeclAttributes(CurScope, Method, ParamInfo);
1029 
1030   // CUDA lambdas get implicit host and device attributes.
1031   if (getLangOpts().CUDA)
1032     CUDASetLambdaAttrs(Method);
1033 
1034   // OpenMP lambdas might get assumumption attributes.
1035   if (LangOpts.OpenMP)
1036     ActOnFinishedFunctionDefinitionInOpenMPAssumeScope(Method);
1037 
1038   // Number the lambda for linkage purposes if necessary.
1039   handleLambdaNumbering(Class, Method);
1040 
1041   // Introduce the function call operator as the current declaration context.
1042   PushDeclContext(CurScope, Method);
1043 
1044   // Build the lambda scope.
1045   buildLambdaScope(LSI, Method, Intro.Range, Intro.Default, Intro.DefaultLoc,
1046                    ExplicitParams, ExplicitResultType, !Method->isConst());
1047 
1048   // C++11 [expr.prim.lambda]p9:
1049   //   A lambda-expression whose smallest enclosing scope is a block scope is a
1050   //   local lambda expression; any other lambda expression shall not have a
1051   //   capture-default or simple-capture in its lambda-introducer.
1052   //
1053   // For simple-captures, this is covered by the check below that any named
1054   // entity is a variable that can be captured.
1055   //
1056   // For DR1632, we also allow a capture-default in any context where we can
1057   // odr-use 'this' (in particular, in a default initializer for a non-static
1058   // data member).
1059   if (Intro.Default != LCD_None && !Class->getParent()->isFunctionOrMethod() &&
1060       (getCurrentThisType().isNull() ||
1061        CheckCXXThisCapture(SourceLocation(), /*Explicit*/true,
1062                            /*BuildAndDiagnose*/false)))
1063     Diag(Intro.DefaultLoc, diag::err_capture_default_non_local);
1064 
1065   // Distinct capture names, for diagnostics.
1066   llvm::SmallSet<IdentifierInfo*, 8> CaptureNames;
1067 
1068   // Handle explicit captures.
1069   SourceLocation PrevCaptureLoc
1070     = Intro.Default == LCD_None? Intro.Range.getBegin() : Intro.DefaultLoc;
1071   for (auto C = Intro.Captures.begin(), E = Intro.Captures.end(); C != E;
1072        PrevCaptureLoc = C->Loc, ++C) {
1073     if (C->Kind == LCK_This || C->Kind == LCK_StarThis) {
1074       if (C->Kind == LCK_StarThis)
1075         Diag(C->Loc, !getLangOpts().CPlusPlus17
1076                              ? diag::ext_star_this_lambda_capture_cxx17
1077                              : diag::warn_cxx14_compat_star_this_lambda_capture);
1078 
1079       // C++11 [expr.prim.lambda]p8:
1080       //   An identifier or this shall not appear more than once in a
1081       //   lambda-capture.
1082       if (LSI->isCXXThisCaptured()) {
1083         Diag(C->Loc, diag::err_capture_more_than_once)
1084             << "'this'" << SourceRange(LSI->getCXXThisCapture().getLocation())
1085             << FixItHint::CreateRemoval(
1086                    SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1087         continue;
1088       }
1089 
1090       // C++2a [expr.prim.lambda]p8:
1091       //  If a lambda-capture includes a capture-default that is =,
1092       //  each simple-capture of that lambda-capture shall be of the form
1093       //  "&identifier", "this", or "* this". [ Note: The form [&,this] is
1094       //  redundant but accepted for compatibility with ISO C++14. --end note ]
1095       if (Intro.Default == LCD_ByCopy && C->Kind != LCK_StarThis)
1096         Diag(C->Loc, !getLangOpts().CPlusPlus20
1097                          ? diag::ext_equals_this_lambda_capture_cxx20
1098                          : diag::warn_cxx17_compat_equals_this_lambda_capture);
1099 
1100       // C++11 [expr.prim.lambda]p12:
1101       //   If this is captured by a local lambda expression, its nearest
1102       //   enclosing function shall be a non-static member function.
1103       QualType ThisCaptureType = getCurrentThisType();
1104       if (ThisCaptureType.isNull()) {
1105         Diag(C->Loc, diag::err_this_capture) << true;
1106         continue;
1107       }
1108 
1109       CheckCXXThisCapture(C->Loc, /*Explicit=*/true, /*BuildAndDiagnose*/ true,
1110                           /*FunctionScopeIndexToStopAtPtr*/ nullptr,
1111                           C->Kind == LCK_StarThis);
1112       if (!LSI->Captures.empty())
1113         LSI->ExplicitCaptureRanges[LSI->Captures.size() - 1] = C->ExplicitRange;
1114       continue;
1115     }
1116 
1117     assert(C->Id && "missing identifier for capture");
1118 
1119     if (C->Init.isInvalid())
1120       continue;
1121 
1122     ValueDecl *Var = nullptr;
1123     if (C->Init.isUsable()) {
1124       Diag(C->Loc, getLangOpts().CPlusPlus14
1125                        ? diag::warn_cxx11_compat_init_capture
1126                        : diag::ext_init_capture);
1127 
1128       // If the initializer expression is usable, but the InitCaptureType
1129       // is not, then an error has occurred - so ignore the capture for now.
1130       // for e.g., [n{0}] { }; <-- if no <initializer_list> is included.
1131       // FIXME: we should create the init capture variable and mark it invalid
1132       // in this case.
1133       if (C->InitCaptureType.get().isNull())
1134         continue;
1135 
1136       if (C->Init.get()->containsUnexpandedParameterPack() &&
1137           !C->InitCaptureType.get()->getAs<PackExpansionType>())
1138         DiagnoseUnexpandedParameterPack(C->Init.get(), UPPC_Initializer);
1139 
1140       unsigned InitStyle;
1141       switch (C->InitKind) {
1142       case LambdaCaptureInitKind::NoInit:
1143         llvm_unreachable("not an init-capture?");
1144       case LambdaCaptureInitKind::CopyInit:
1145         InitStyle = VarDecl::CInit;
1146         break;
1147       case LambdaCaptureInitKind::DirectInit:
1148         InitStyle = VarDecl::CallInit;
1149         break;
1150       case LambdaCaptureInitKind::ListInit:
1151         InitStyle = VarDecl::ListInit;
1152         break;
1153       }
1154       Var = createLambdaInitCaptureVarDecl(C->Loc, C->InitCaptureType.get(),
1155                                            C->EllipsisLoc, C->Id, InitStyle,
1156                                            C->Init.get());
1157       // C++1y [expr.prim.lambda]p11:
1158       //   An init-capture behaves as if it declares and explicitly
1159       //   captures a variable [...] whose declarative region is the
1160       //   lambda-expression's compound-statement
1161       if (Var)
1162         PushOnScopeChains(Var, CurScope, false);
1163     } else {
1164       assert(C->InitKind == LambdaCaptureInitKind::NoInit &&
1165              "init capture has valid but null init?");
1166 
1167       // C++11 [expr.prim.lambda]p8:
1168       //   If a lambda-capture includes a capture-default that is &, the
1169       //   identifiers in the lambda-capture shall not be preceded by &.
1170       //   If a lambda-capture includes a capture-default that is =, [...]
1171       //   each identifier it contains shall be preceded by &.
1172       if (C->Kind == LCK_ByRef && Intro.Default == LCD_ByRef) {
1173         Diag(C->Loc, diag::err_reference_capture_with_reference_default)
1174             << FixItHint::CreateRemoval(
1175                 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1176         continue;
1177       } else if (C->Kind == LCK_ByCopy && Intro.Default == LCD_ByCopy) {
1178         Diag(C->Loc, diag::err_copy_capture_with_copy_default)
1179             << FixItHint::CreateRemoval(
1180                 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1181         continue;
1182       }
1183 
1184       // C++11 [expr.prim.lambda]p10:
1185       //   The identifiers in a capture-list are looked up using the usual
1186       //   rules for unqualified name lookup (3.4.1)
1187       DeclarationNameInfo Name(C->Id, C->Loc);
1188       LookupResult R(*this, Name, LookupOrdinaryName);
1189       LookupName(R, CurScope);
1190       if (R.isAmbiguous())
1191         continue;
1192       if (R.empty()) {
1193         // FIXME: Disable corrections that would add qualification?
1194         CXXScopeSpec ScopeSpec;
1195         DeclFilterCCC<VarDecl> Validator{};
1196         if (DiagnoseEmptyLookup(CurScope, ScopeSpec, R, Validator))
1197           continue;
1198       }
1199 
1200       if (auto *BD = R.getAsSingle<BindingDecl>())
1201         Var = BD;
1202       else
1203         Var = R.getAsSingle<VarDecl>();
1204       if (Var && DiagnoseUseOfDecl(Var, C->Loc))
1205         continue;
1206     }
1207 
1208     // C++11 [expr.prim.lambda]p8:
1209     //   An identifier or this shall not appear more than once in a
1210     //   lambda-capture.
1211     if (!CaptureNames.insert(C->Id).second) {
1212       if (Var && LSI->isCaptured(Var)) {
1213         Diag(C->Loc, diag::err_capture_more_than_once)
1214             << C->Id << SourceRange(LSI->getCapture(Var).getLocation())
1215             << FixItHint::CreateRemoval(
1216                    SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1217       } else
1218         // Previous capture captured something different (one or both was
1219         // an init-cpature): no fixit.
1220         Diag(C->Loc, diag::err_capture_more_than_once) << C->Id;
1221       continue;
1222     }
1223 
1224     // C++11 [expr.prim.lambda]p10:
1225     //   [...] each such lookup shall find a variable with automatic storage
1226     //   duration declared in the reaching scope of the local lambda expression.
1227     // Note that the 'reaching scope' check happens in tryCaptureVariable().
1228     if (!Var) {
1229       Diag(C->Loc, diag::err_capture_does_not_name_variable) << C->Id;
1230       continue;
1231     }
1232 
1233     // Ignore invalid decls; they'll just confuse the code later.
1234     if (Var->isInvalidDecl())
1235       continue;
1236 
1237     VarDecl *Underlying = Var->getPotentiallyDecomposedVarDecl();
1238 
1239     if (!Underlying->hasLocalStorage()) {
1240       Diag(C->Loc, diag::err_capture_non_automatic_variable) << C->Id;
1241       Diag(Var->getLocation(), diag::note_previous_decl) << C->Id;
1242       continue;
1243     }
1244 
1245     // C++11 [expr.prim.lambda]p23:
1246     //   A capture followed by an ellipsis is a pack expansion (14.5.3).
1247     SourceLocation EllipsisLoc;
1248     if (C->EllipsisLoc.isValid()) {
1249       if (Var->isParameterPack()) {
1250         EllipsisLoc = C->EllipsisLoc;
1251       } else {
1252         Diag(C->EllipsisLoc, diag::err_pack_expansion_without_parameter_packs)
1253             << (C->Init.isUsable() ? C->Init.get()->getSourceRange()
1254                                    : SourceRange(C->Loc));
1255 
1256         // Just ignore the ellipsis.
1257       }
1258     } else if (Var->isParameterPack()) {
1259       ContainsUnexpandedParameterPack = true;
1260     }
1261 
1262     if (C->Init.isUsable()) {
1263       addInitCapture(LSI, cast<VarDecl>(Var), C->Kind == LCK_ByRef);
1264     } else {
1265       TryCaptureKind Kind = C->Kind == LCK_ByRef ? TryCapture_ExplicitByRef :
1266                                                    TryCapture_ExplicitByVal;
1267       tryCaptureVariable(Var, C->Loc, Kind, EllipsisLoc);
1268     }
1269     if (!LSI->Captures.empty())
1270       LSI->ExplicitCaptureRanges[LSI->Captures.size() - 1] = C->ExplicitRange;
1271   }
1272   finishLambdaExplicitCaptures(LSI);
1273 
1274   LSI->ContainsUnexpandedParameterPack |= ContainsUnexpandedParameterPack;
1275 
1276   // Add lambda parameters into scope.
1277   addLambdaParameters(Intro.Captures, Method, CurScope);
1278 
1279   // Enter a new evaluation context to insulate the lambda from any
1280   // cleanups from the enclosing full-expression.
1281   PushExpressionEvaluationContext(
1282       LSI->CallOperator->isConsteval()
1283           ? ExpressionEvaluationContext::ImmediateFunctionContext
1284           : ExpressionEvaluationContext::PotentiallyEvaluated);
1285 }
1286 
ActOnLambdaError(SourceLocation StartLoc,Scope * CurScope,bool IsInstantiation)1287 void Sema::ActOnLambdaError(SourceLocation StartLoc, Scope *CurScope,
1288                             bool IsInstantiation) {
1289   LambdaScopeInfo *LSI = cast<LambdaScopeInfo>(FunctionScopes.back());
1290 
1291   // Leave the expression-evaluation context.
1292   DiscardCleanupsInEvaluationContext();
1293   PopExpressionEvaluationContext();
1294 
1295   // Leave the context of the lambda.
1296   if (!IsInstantiation)
1297     PopDeclContext();
1298 
1299   // Finalize the lambda.
1300   CXXRecordDecl *Class = LSI->Lambda;
1301   Class->setInvalidDecl();
1302   SmallVector<Decl*, 4> Fields(Class->fields());
1303   ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
1304               SourceLocation(), ParsedAttributesView());
1305   CheckCompletedCXXClass(nullptr, Class);
1306 
1307   PopFunctionScopeInfo();
1308 }
1309 
1310 template <typename Func>
repeatForLambdaConversionFunctionCallingConvs(Sema & S,const FunctionProtoType & CallOpProto,Func F)1311 static void repeatForLambdaConversionFunctionCallingConvs(
1312     Sema &S, const FunctionProtoType &CallOpProto, Func F) {
1313   CallingConv DefaultFree = S.Context.getDefaultCallingConvention(
1314       CallOpProto.isVariadic(), /*IsCXXMethod=*/false);
1315   CallingConv DefaultMember = S.Context.getDefaultCallingConvention(
1316       CallOpProto.isVariadic(), /*IsCXXMethod=*/true);
1317   CallingConv CallOpCC = CallOpProto.getCallConv();
1318 
1319   /// Implement emitting a version of the operator for many of the calling
1320   /// conventions for MSVC, as described here:
1321   /// https://devblogs.microsoft.com/oldnewthing/20150220-00/?p=44623.
1322   /// Experimentally, we determined that cdecl, stdcall, fastcall, and
1323   /// vectorcall are generated by MSVC when it is supported by the target.
1324   /// Additionally, we are ensuring that the default-free/default-member and
1325   /// call-operator calling convention are generated as well.
1326   /// NOTE: We intentionally generate a 'thiscall' on Win32 implicitly from the
1327   /// 'member default', despite MSVC not doing so. We do this in order to ensure
1328   /// that someone who intentionally places 'thiscall' on the lambda call
1329   /// operator will still get that overload, since we don't have the a way of
1330   /// detecting the attribute by the time we get here.
1331   if (S.getLangOpts().MSVCCompat) {
1332     CallingConv Convs[] = {
1333         CC_C,        CC_X86StdCall, CC_X86FastCall, CC_X86VectorCall,
1334         DefaultFree, DefaultMember, CallOpCC};
1335     llvm::sort(Convs);
1336     llvm::iterator_range<CallingConv *> Range(
1337         std::begin(Convs), std::unique(std::begin(Convs), std::end(Convs)));
1338     const TargetInfo &TI = S.getASTContext().getTargetInfo();
1339 
1340     for (CallingConv C : Range) {
1341       if (TI.checkCallingConvention(C) == TargetInfo::CCCR_OK)
1342         F(C);
1343     }
1344     return;
1345   }
1346 
1347   if (CallOpCC == DefaultMember && DefaultMember != DefaultFree) {
1348     F(DefaultFree);
1349     F(DefaultMember);
1350   } else {
1351     F(CallOpCC);
1352   }
1353 }
1354 
1355 // Returns the 'standard' calling convention to be used for the lambda
1356 // conversion function, that is, the 'free' function calling convention unless
1357 // it is overridden by a non-default calling convention attribute.
1358 static CallingConv
getLambdaConversionFunctionCallConv(Sema & S,const FunctionProtoType * CallOpProto)1359 getLambdaConversionFunctionCallConv(Sema &S,
1360                                     const FunctionProtoType *CallOpProto) {
1361   CallingConv DefaultFree = S.Context.getDefaultCallingConvention(
1362       CallOpProto->isVariadic(), /*IsCXXMethod=*/false);
1363   CallingConv DefaultMember = S.Context.getDefaultCallingConvention(
1364       CallOpProto->isVariadic(), /*IsCXXMethod=*/true);
1365   CallingConv CallOpCC = CallOpProto->getCallConv();
1366 
1367   // If the call-operator hasn't been changed, return both the 'free' and
1368   // 'member' function calling convention.
1369   if (CallOpCC == DefaultMember && DefaultMember != DefaultFree)
1370     return DefaultFree;
1371   return CallOpCC;
1372 }
1373 
getLambdaConversionFunctionResultType(const FunctionProtoType * CallOpProto,CallingConv CC)1374 QualType Sema::getLambdaConversionFunctionResultType(
1375     const FunctionProtoType *CallOpProto, CallingConv CC) {
1376   const FunctionProtoType::ExtProtoInfo CallOpExtInfo =
1377       CallOpProto->getExtProtoInfo();
1378   FunctionProtoType::ExtProtoInfo InvokerExtInfo = CallOpExtInfo;
1379   InvokerExtInfo.ExtInfo = InvokerExtInfo.ExtInfo.withCallingConv(CC);
1380   InvokerExtInfo.TypeQuals = Qualifiers();
1381   assert(InvokerExtInfo.RefQualifier == RQ_None &&
1382          "Lambda's call operator should not have a reference qualifier");
1383   return Context.getFunctionType(CallOpProto->getReturnType(),
1384                                  CallOpProto->getParamTypes(), InvokerExtInfo);
1385 }
1386 
1387 /// Add a lambda's conversion to function pointer, as described in
1388 /// C++11 [expr.prim.lambda]p6.
addFunctionPointerConversion(Sema & S,SourceRange IntroducerRange,CXXRecordDecl * Class,CXXMethodDecl * CallOperator,QualType InvokerFunctionTy)1389 static void addFunctionPointerConversion(Sema &S, SourceRange IntroducerRange,
1390                                          CXXRecordDecl *Class,
1391                                          CXXMethodDecl *CallOperator,
1392                                          QualType InvokerFunctionTy) {
1393   // This conversion is explicitly disabled if the lambda's function has
1394   // pass_object_size attributes on any of its parameters.
1395   auto HasPassObjectSizeAttr = [](const ParmVarDecl *P) {
1396     return P->hasAttr<PassObjectSizeAttr>();
1397   };
1398   if (llvm::any_of(CallOperator->parameters(), HasPassObjectSizeAttr))
1399     return;
1400 
1401   // Add the conversion to function pointer.
1402   QualType PtrToFunctionTy = S.Context.getPointerType(InvokerFunctionTy);
1403 
1404   // Create the type of the conversion function.
1405   FunctionProtoType::ExtProtoInfo ConvExtInfo(
1406       S.Context.getDefaultCallingConvention(
1407       /*IsVariadic=*/false, /*IsCXXMethod=*/true));
1408   // The conversion function is always const and noexcept.
1409   ConvExtInfo.TypeQuals = Qualifiers();
1410   ConvExtInfo.TypeQuals.addConst();
1411   ConvExtInfo.ExceptionSpec.Type = EST_BasicNoexcept;
1412   QualType ConvTy =
1413       S.Context.getFunctionType(PtrToFunctionTy, std::nullopt, ConvExtInfo);
1414 
1415   SourceLocation Loc = IntroducerRange.getBegin();
1416   DeclarationName ConversionName
1417     = S.Context.DeclarationNames.getCXXConversionFunctionName(
1418         S.Context.getCanonicalType(PtrToFunctionTy));
1419   // Construct a TypeSourceInfo for the conversion function, and wire
1420   // all the parameters appropriately for the FunctionProtoTypeLoc
1421   // so that everything works during transformation/instantiation of
1422   // generic lambdas.
1423   // The main reason for wiring up the parameters of the conversion
1424   // function with that of the call operator is so that constructs
1425   // like the following work:
1426   // auto L = [](auto b) {                <-- 1
1427   //   return [](auto a) -> decltype(a) { <-- 2
1428   //      return a;
1429   //   };
1430   // };
1431   // int (*fp)(int) = L(5);
1432   // Because the trailing return type can contain DeclRefExprs that refer
1433   // to the original call operator's variables, we hijack the call
1434   // operators ParmVarDecls below.
1435   TypeSourceInfo *ConvNamePtrToFunctionTSI =
1436       S.Context.getTrivialTypeSourceInfo(PtrToFunctionTy, Loc);
1437   DeclarationNameLoc ConvNameLoc =
1438       DeclarationNameLoc::makeNamedTypeLoc(ConvNamePtrToFunctionTSI);
1439 
1440   // The conversion function is a conversion to a pointer-to-function.
1441   TypeSourceInfo *ConvTSI = S.Context.getTrivialTypeSourceInfo(ConvTy, Loc);
1442   FunctionProtoTypeLoc ConvTL =
1443       ConvTSI->getTypeLoc().getAs<FunctionProtoTypeLoc>();
1444   // Get the result of the conversion function which is a pointer-to-function.
1445   PointerTypeLoc PtrToFunctionTL =
1446       ConvTL.getReturnLoc().getAs<PointerTypeLoc>();
1447   // Do the same for the TypeSourceInfo that is used to name the conversion
1448   // operator.
1449   PointerTypeLoc ConvNamePtrToFunctionTL =
1450       ConvNamePtrToFunctionTSI->getTypeLoc().getAs<PointerTypeLoc>();
1451 
1452   // Get the underlying function types that the conversion function will
1453   // be converting to (should match the type of the call operator).
1454   FunctionProtoTypeLoc CallOpConvTL =
1455       PtrToFunctionTL.getPointeeLoc().getAs<FunctionProtoTypeLoc>();
1456   FunctionProtoTypeLoc CallOpConvNameTL =
1457     ConvNamePtrToFunctionTL.getPointeeLoc().getAs<FunctionProtoTypeLoc>();
1458 
1459   // Wire up the FunctionProtoTypeLocs with the call operator's parameters.
1460   // These parameter's are essentially used to transform the name and
1461   // the type of the conversion operator.  By using the same parameters
1462   // as the call operator's we don't have to fix any back references that
1463   // the trailing return type of the call operator's uses (such as
1464   // decltype(some_type<decltype(a)>::type{} + decltype(a){}) etc.)
1465   // - we can simply use the return type of the call operator, and
1466   // everything should work.
1467   SmallVector<ParmVarDecl *, 4> InvokerParams;
1468   for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I) {
1469     ParmVarDecl *From = CallOperator->getParamDecl(I);
1470 
1471     InvokerParams.push_back(ParmVarDecl::Create(
1472         S.Context,
1473         // Temporarily add to the TU. This is set to the invoker below.
1474         S.Context.getTranslationUnitDecl(), From->getBeginLoc(),
1475         From->getLocation(), From->getIdentifier(), From->getType(),
1476         From->getTypeSourceInfo(), From->getStorageClass(),
1477         /*DefArg=*/nullptr));
1478     CallOpConvTL.setParam(I, From);
1479     CallOpConvNameTL.setParam(I, From);
1480   }
1481 
1482   CXXConversionDecl *Conversion = CXXConversionDecl::Create(
1483       S.Context, Class, Loc,
1484       DeclarationNameInfo(ConversionName, Loc, ConvNameLoc), ConvTy, ConvTSI,
1485       S.getCurFPFeatures().isFPConstrained(),
1486       /*isInline=*/true, ExplicitSpecifier(),
1487       S.getLangOpts().CPlusPlus17 ? ConstexprSpecKind::Constexpr
1488                                   : ConstexprSpecKind::Unspecified,
1489       CallOperator->getBody()->getEndLoc());
1490   Conversion->setAccess(AS_public);
1491   Conversion->setImplicit(true);
1492 
1493   if (Class->isGenericLambda()) {
1494     // Create a template version of the conversion operator, using the template
1495     // parameter list of the function call operator.
1496     FunctionTemplateDecl *TemplateCallOperator =
1497             CallOperator->getDescribedFunctionTemplate();
1498     FunctionTemplateDecl *ConversionTemplate =
1499                   FunctionTemplateDecl::Create(S.Context, Class,
1500                                       Loc, ConversionName,
1501                                       TemplateCallOperator->getTemplateParameters(),
1502                                       Conversion);
1503     ConversionTemplate->setAccess(AS_public);
1504     ConversionTemplate->setImplicit(true);
1505     Conversion->setDescribedFunctionTemplate(ConversionTemplate);
1506     Class->addDecl(ConversionTemplate);
1507   } else
1508     Class->addDecl(Conversion);
1509 
1510   // If the lambda is not static, we need to add a static member
1511   // function that will be the result of the conversion with a
1512   // certain unique ID.
1513   // When it is static we just return the static call operator instead.
1514   if (CallOperator->isInstance()) {
1515     DeclarationName InvokerName =
1516         &S.Context.Idents.get(getLambdaStaticInvokerName());
1517     // FIXME: Instead of passing in the CallOperator->getTypeSourceInfo()
1518     // we should get a prebuilt TrivialTypeSourceInfo from Context
1519     // using FunctionTy & Loc and get its TypeLoc as a FunctionProtoTypeLoc
1520     // then rewire the parameters accordingly, by hoisting up the InvokeParams
1521     // loop below and then use its Params to set Invoke->setParams(...) below.
1522     // This would avoid the 'const' qualifier of the calloperator from
1523     // contaminating the type of the invoker, which is currently adjusted
1524     // in SemaTemplateDeduction.cpp:DeduceTemplateArguments.  Fixing the
1525     // trailing return type of the invoker would require a visitor to rebuild
1526     // the trailing return type and adjusting all back DeclRefExpr's to refer
1527     // to the new static invoker parameters - not the call operator's.
1528     CXXMethodDecl *Invoke = CXXMethodDecl::Create(
1529         S.Context, Class, Loc, DeclarationNameInfo(InvokerName, Loc),
1530         InvokerFunctionTy, CallOperator->getTypeSourceInfo(), SC_Static,
1531         S.getCurFPFeatures().isFPConstrained(),
1532         /*isInline=*/true, ConstexprSpecKind::Unspecified,
1533         CallOperator->getBody()->getEndLoc());
1534     for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I)
1535       InvokerParams[I]->setOwningFunction(Invoke);
1536     Invoke->setParams(InvokerParams);
1537     Invoke->setAccess(AS_private);
1538     Invoke->setImplicit(true);
1539     if (Class->isGenericLambda()) {
1540       FunctionTemplateDecl *TemplateCallOperator =
1541           CallOperator->getDescribedFunctionTemplate();
1542       FunctionTemplateDecl *StaticInvokerTemplate =
1543           FunctionTemplateDecl::Create(
1544               S.Context, Class, Loc, InvokerName,
1545               TemplateCallOperator->getTemplateParameters(), Invoke);
1546       StaticInvokerTemplate->setAccess(AS_private);
1547       StaticInvokerTemplate->setImplicit(true);
1548       Invoke->setDescribedFunctionTemplate(StaticInvokerTemplate);
1549       Class->addDecl(StaticInvokerTemplate);
1550     } else
1551       Class->addDecl(Invoke);
1552   }
1553 }
1554 
1555 /// Add a lambda's conversion to function pointers, as described in
1556 /// C++11 [expr.prim.lambda]p6. Note that in most cases, this should emit only a
1557 /// single pointer conversion. In the event that the default calling convention
1558 /// for free and member functions is different, it will emit both conventions.
addFunctionPointerConversions(Sema & S,SourceRange IntroducerRange,CXXRecordDecl * Class,CXXMethodDecl * CallOperator)1559 static void addFunctionPointerConversions(Sema &S, SourceRange IntroducerRange,
1560                                           CXXRecordDecl *Class,
1561                                           CXXMethodDecl *CallOperator) {
1562   const FunctionProtoType *CallOpProto =
1563       CallOperator->getType()->castAs<FunctionProtoType>();
1564 
1565   repeatForLambdaConversionFunctionCallingConvs(
1566       S, *CallOpProto, [&](CallingConv CC) {
1567         QualType InvokerFunctionTy =
1568             S.getLambdaConversionFunctionResultType(CallOpProto, CC);
1569         addFunctionPointerConversion(S, IntroducerRange, Class, CallOperator,
1570                                      InvokerFunctionTy);
1571       });
1572 }
1573 
1574 /// Add a lambda's conversion to block pointer.
addBlockPointerConversion(Sema & S,SourceRange IntroducerRange,CXXRecordDecl * Class,CXXMethodDecl * CallOperator)1575 static void addBlockPointerConversion(Sema &S,
1576                                       SourceRange IntroducerRange,
1577                                       CXXRecordDecl *Class,
1578                                       CXXMethodDecl *CallOperator) {
1579   const FunctionProtoType *CallOpProto =
1580       CallOperator->getType()->castAs<FunctionProtoType>();
1581   QualType FunctionTy = S.getLambdaConversionFunctionResultType(
1582       CallOpProto, getLambdaConversionFunctionCallConv(S, CallOpProto));
1583   QualType BlockPtrTy = S.Context.getBlockPointerType(FunctionTy);
1584 
1585   FunctionProtoType::ExtProtoInfo ConversionEPI(
1586       S.Context.getDefaultCallingConvention(
1587           /*IsVariadic=*/false, /*IsCXXMethod=*/true));
1588   ConversionEPI.TypeQuals = Qualifiers();
1589   ConversionEPI.TypeQuals.addConst();
1590   QualType ConvTy =
1591       S.Context.getFunctionType(BlockPtrTy, std::nullopt, ConversionEPI);
1592 
1593   SourceLocation Loc = IntroducerRange.getBegin();
1594   DeclarationName Name
1595     = S.Context.DeclarationNames.getCXXConversionFunctionName(
1596         S.Context.getCanonicalType(BlockPtrTy));
1597   DeclarationNameLoc NameLoc = DeclarationNameLoc::makeNamedTypeLoc(
1598       S.Context.getTrivialTypeSourceInfo(BlockPtrTy, Loc));
1599   CXXConversionDecl *Conversion = CXXConversionDecl::Create(
1600       S.Context, Class, Loc, DeclarationNameInfo(Name, Loc, NameLoc), ConvTy,
1601       S.Context.getTrivialTypeSourceInfo(ConvTy, Loc),
1602       S.getCurFPFeatures().isFPConstrained(),
1603       /*isInline=*/true, ExplicitSpecifier(), ConstexprSpecKind::Unspecified,
1604       CallOperator->getBody()->getEndLoc());
1605   Conversion->setAccess(AS_public);
1606   Conversion->setImplicit(true);
1607   Class->addDecl(Conversion);
1608 }
1609 
BuildCaptureInit(const Capture & Cap,SourceLocation ImplicitCaptureLoc,bool IsOpenMPMapping)1610 ExprResult Sema::BuildCaptureInit(const Capture &Cap,
1611                                   SourceLocation ImplicitCaptureLoc,
1612                                   bool IsOpenMPMapping) {
1613   // VLA captures don't have a stored initialization expression.
1614   if (Cap.isVLATypeCapture())
1615     return ExprResult();
1616 
1617   // An init-capture is initialized directly from its stored initializer.
1618   if (Cap.isInitCapture())
1619     return cast<VarDecl>(Cap.getVariable())->getInit();
1620 
1621   // For anything else, build an initialization expression. For an implicit
1622   // capture, the capture notionally happens at the capture-default, so use
1623   // that location here.
1624   SourceLocation Loc =
1625       ImplicitCaptureLoc.isValid() ? ImplicitCaptureLoc : Cap.getLocation();
1626 
1627   // C++11 [expr.prim.lambda]p21:
1628   //   When the lambda-expression is evaluated, the entities that
1629   //   are captured by copy are used to direct-initialize each
1630   //   corresponding non-static data member of the resulting closure
1631   //   object. (For array members, the array elements are
1632   //   direct-initialized in increasing subscript order.) These
1633   //   initializations are performed in the (unspecified) order in
1634   //   which the non-static data members are declared.
1635 
1636   // C++ [expr.prim.lambda]p12:
1637   //   An entity captured by a lambda-expression is odr-used (3.2) in
1638   //   the scope containing the lambda-expression.
1639   ExprResult Init;
1640   IdentifierInfo *Name = nullptr;
1641   if (Cap.isThisCapture()) {
1642     QualType ThisTy = getCurrentThisType();
1643     Expr *This = BuildCXXThisExpr(Loc, ThisTy, ImplicitCaptureLoc.isValid());
1644     if (Cap.isCopyCapture())
1645       Init = CreateBuiltinUnaryOp(Loc, UO_Deref, This);
1646     else
1647       Init = This;
1648   } else {
1649     assert(Cap.isVariableCapture() && "unknown kind of capture");
1650     ValueDecl *Var = Cap.getVariable();
1651     Name = Var->getIdentifier();
1652     Init = BuildDeclarationNameExpr(
1653       CXXScopeSpec(), DeclarationNameInfo(Var->getDeclName(), Loc), Var);
1654   }
1655 
1656   // In OpenMP, the capture kind doesn't actually describe how to capture:
1657   // variables are "mapped" onto the device in a process that does not formally
1658   // make a copy, even for a "copy capture".
1659   if (IsOpenMPMapping)
1660     return Init;
1661 
1662   if (Init.isInvalid())
1663     return ExprError();
1664 
1665   Expr *InitExpr = Init.get();
1666   InitializedEntity Entity = InitializedEntity::InitializeLambdaCapture(
1667       Name, Cap.getCaptureType(), Loc);
1668   InitializationKind InitKind =
1669       InitializationKind::CreateDirect(Loc, Loc, Loc);
1670   InitializationSequence InitSeq(*this, Entity, InitKind, InitExpr);
1671   return InitSeq.Perform(*this, Entity, InitKind, InitExpr);
1672 }
1673 
ActOnLambdaExpr(SourceLocation StartLoc,Stmt * Body,Scope * CurScope)1674 ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
1675                                  Scope *CurScope) {
1676   LambdaScopeInfo LSI = *cast<LambdaScopeInfo>(FunctionScopes.back());
1677   ActOnFinishFunctionBody(LSI.CallOperator, Body);
1678   return BuildLambdaExpr(StartLoc, Body->getEndLoc(), &LSI);
1679 }
1680 
1681 static LambdaCaptureDefault
mapImplicitCaptureStyle(CapturingScopeInfo::ImplicitCaptureStyle ICS)1682 mapImplicitCaptureStyle(CapturingScopeInfo::ImplicitCaptureStyle ICS) {
1683   switch (ICS) {
1684   case CapturingScopeInfo::ImpCap_None:
1685     return LCD_None;
1686   case CapturingScopeInfo::ImpCap_LambdaByval:
1687     return LCD_ByCopy;
1688   case CapturingScopeInfo::ImpCap_CapturedRegion:
1689   case CapturingScopeInfo::ImpCap_LambdaByref:
1690     return LCD_ByRef;
1691   case CapturingScopeInfo::ImpCap_Block:
1692     llvm_unreachable("block capture in lambda");
1693   }
1694   llvm_unreachable("Unknown implicit capture style");
1695 }
1696 
CaptureHasSideEffects(const Capture & From)1697 bool Sema::CaptureHasSideEffects(const Capture &From) {
1698   if (From.isInitCapture()) {
1699     Expr *Init = cast<VarDecl>(From.getVariable())->getInit();
1700     if (Init && Init->HasSideEffects(Context))
1701       return true;
1702   }
1703 
1704   if (!From.isCopyCapture())
1705     return false;
1706 
1707   const QualType T = From.isThisCapture()
1708                          ? getCurrentThisType()->getPointeeType()
1709                          : From.getCaptureType();
1710 
1711   if (T.isVolatileQualified())
1712     return true;
1713 
1714   const Type *BaseT = T->getBaseElementTypeUnsafe();
1715   if (const CXXRecordDecl *RD = BaseT->getAsCXXRecordDecl())
1716     return !RD->isCompleteDefinition() || !RD->hasTrivialCopyConstructor() ||
1717            !RD->hasTrivialDestructor();
1718 
1719   return false;
1720 }
1721 
DiagnoseUnusedLambdaCapture(SourceRange CaptureRange,const Capture & From)1722 bool Sema::DiagnoseUnusedLambdaCapture(SourceRange CaptureRange,
1723                                        const Capture &From) {
1724   if (CaptureHasSideEffects(From))
1725     return false;
1726 
1727   if (From.isVLATypeCapture())
1728     return false;
1729 
1730   auto diag = Diag(From.getLocation(), diag::warn_unused_lambda_capture);
1731   if (From.isThisCapture())
1732     diag << "'this'";
1733   else
1734     diag << From.getVariable();
1735   diag << From.isNonODRUsed();
1736   diag << FixItHint::CreateRemoval(CaptureRange);
1737   return true;
1738 }
1739 
1740 /// Create a field within the lambda class or captured statement record for the
1741 /// given capture.
BuildCaptureField(RecordDecl * RD,const sema::Capture & Capture)1742 FieldDecl *Sema::BuildCaptureField(RecordDecl *RD,
1743                                    const sema::Capture &Capture) {
1744   SourceLocation Loc = Capture.getLocation();
1745   QualType FieldType = Capture.getCaptureType();
1746 
1747   TypeSourceInfo *TSI = nullptr;
1748   if (Capture.isVariableCapture()) {
1749     const auto *Var = dyn_cast_or_null<VarDecl>(Capture.getVariable());
1750     if (Var && Var->isInitCapture())
1751       TSI = Var->getTypeSourceInfo();
1752   }
1753 
1754   // FIXME: Should we really be doing this? A null TypeSourceInfo seems more
1755   // appropriate, at least for an implicit capture.
1756   if (!TSI)
1757     TSI = Context.getTrivialTypeSourceInfo(FieldType, Loc);
1758 
1759   // Build the non-static data member.
1760   FieldDecl *Field =
1761       FieldDecl::Create(Context, RD, /*StartLoc=*/Loc, /*IdLoc=*/Loc,
1762                         /*Id=*/nullptr, FieldType, TSI, /*BW=*/nullptr,
1763                         /*Mutable=*/false, ICIS_NoInit);
1764   // If the variable being captured has an invalid type, mark the class as
1765   // invalid as well.
1766   if (!FieldType->isDependentType()) {
1767     if (RequireCompleteSizedType(Loc, FieldType,
1768                                  diag::err_field_incomplete_or_sizeless)) {
1769       RD->setInvalidDecl();
1770       Field->setInvalidDecl();
1771     } else {
1772       NamedDecl *Def;
1773       FieldType->isIncompleteType(&Def);
1774       if (Def && Def->isInvalidDecl()) {
1775         RD->setInvalidDecl();
1776         Field->setInvalidDecl();
1777       }
1778     }
1779   }
1780   Field->setImplicit(true);
1781   Field->setAccess(AS_private);
1782   RD->addDecl(Field);
1783 
1784   if (Capture.isVLATypeCapture())
1785     Field->setCapturedVLAType(Capture.getCapturedVLAType());
1786 
1787   return Field;
1788 }
1789 
BuildLambdaExpr(SourceLocation StartLoc,SourceLocation EndLoc,LambdaScopeInfo * LSI)1790 ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
1791                                  LambdaScopeInfo *LSI) {
1792   // Collect information from the lambda scope.
1793   SmallVector<LambdaCapture, 4> Captures;
1794   SmallVector<Expr *, 4> CaptureInits;
1795   SourceLocation CaptureDefaultLoc = LSI->CaptureDefaultLoc;
1796   LambdaCaptureDefault CaptureDefault =
1797       mapImplicitCaptureStyle(LSI->ImpCaptureStyle);
1798   CXXRecordDecl *Class;
1799   CXXMethodDecl *CallOperator;
1800   SourceRange IntroducerRange;
1801   bool ExplicitParams;
1802   bool ExplicitResultType;
1803   CleanupInfo LambdaCleanup;
1804   bool ContainsUnexpandedParameterPack;
1805   bool IsGenericLambda;
1806   {
1807     CallOperator = LSI->CallOperator;
1808     Class = LSI->Lambda;
1809     IntroducerRange = LSI->IntroducerRange;
1810     ExplicitParams = LSI->ExplicitParams;
1811     ExplicitResultType = !LSI->HasImplicitReturnType;
1812     LambdaCleanup = LSI->Cleanup;
1813     ContainsUnexpandedParameterPack = LSI->ContainsUnexpandedParameterPack;
1814     IsGenericLambda = Class->isGenericLambda();
1815 
1816     CallOperator->setLexicalDeclContext(Class);
1817     Decl *TemplateOrNonTemplateCallOperatorDecl =
1818         CallOperator->getDescribedFunctionTemplate()
1819         ? CallOperator->getDescribedFunctionTemplate()
1820         : cast<Decl>(CallOperator);
1821 
1822     // FIXME: Is this really the best choice? Keeping the lexical decl context
1823     // set as CurContext seems more faithful to the source.
1824     TemplateOrNonTemplateCallOperatorDecl->setLexicalDeclContext(Class);
1825 
1826     PopExpressionEvaluationContext();
1827 
1828     // True if the current capture has a used capture or default before it.
1829     bool CurHasPreviousCapture = CaptureDefault != LCD_None;
1830     SourceLocation PrevCaptureLoc = CurHasPreviousCapture ?
1831         CaptureDefaultLoc : IntroducerRange.getBegin();
1832 
1833     for (unsigned I = 0, N = LSI->Captures.size(); I != N; ++I) {
1834       const Capture &From = LSI->Captures[I];
1835 
1836       if (From.isInvalid())
1837         return ExprError();
1838 
1839       assert(!From.isBlockCapture() && "Cannot capture __block variables");
1840       bool IsImplicit = I >= LSI->NumExplicitCaptures;
1841       SourceLocation ImplicitCaptureLoc =
1842           IsImplicit ? CaptureDefaultLoc : SourceLocation();
1843 
1844       // Use source ranges of explicit captures for fixits where available.
1845       SourceRange CaptureRange = LSI->ExplicitCaptureRanges[I];
1846 
1847       // Warn about unused explicit captures.
1848       bool IsCaptureUsed = true;
1849       if (!CurContext->isDependentContext() && !IsImplicit &&
1850           !From.isODRUsed()) {
1851         // Initialized captures that are non-ODR used may not be eliminated.
1852         // FIXME: Where did the IsGenericLambda here come from?
1853         bool NonODRUsedInitCapture =
1854             IsGenericLambda && From.isNonODRUsed() && From.isInitCapture();
1855         if (!NonODRUsedInitCapture) {
1856           bool IsLast = (I + 1) == LSI->NumExplicitCaptures;
1857           SourceRange FixItRange;
1858           if (CaptureRange.isValid()) {
1859             if (!CurHasPreviousCapture && !IsLast) {
1860               // If there are no captures preceding this capture, remove the
1861               // following comma.
1862               FixItRange = SourceRange(CaptureRange.getBegin(),
1863                                        getLocForEndOfToken(CaptureRange.getEnd()));
1864             } else {
1865               // Otherwise, remove the comma since the last used capture.
1866               FixItRange = SourceRange(getLocForEndOfToken(PrevCaptureLoc),
1867                                        CaptureRange.getEnd());
1868             }
1869           }
1870 
1871           IsCaptureUsed = !DiagnoseUnusedLambdaCapture(FixItRange, From);
1872         }
1873       }
1874 
1875       if (CaptureRange.isValid()) {
1876         CurHasPreviousCapture |= IsCaptureUsed;
1877         PrevCaptureLoc = CaptureRange.getEnd();
1878       }
1879 
1880       // Map the capture to our AST representation.
1881       LambdaCapture Capture = [&] {
1882         if (From.isThisCapture()) {
1883           // Capturing 'this' implicitly with a default of '[=]' is deprecated,
1884           // because it results in a reference capture. Don't warn prior to
1885           // C++2a; there's nothing that can be done about it before then.
1886           if (getLangOpts().CPlusPlus20 && IsImplicit &&
1887               CaptureDefault == LCD_ByCopy) {
1888             Diag(From.getLocation(), diag::warn_deprecated_this_capture);
1889             Diag(CaptureDefaultLoc, diag::note_deprecated_this_capture)
1890                 << FixItHint::CreateInsertion(
1891                        getLocForEndOfToken(CaptureDefaultLoc), ", this");
1892           }
1893           return LambdaCapture(From.getLocation(), IsImplicit,
1894                                From.isCopyCapture() ? LCK_StarThis : LCK_This);
1895         } else if (From.isVLATypeCapture()) {
1896           return LambdaCapture(From.getLocation(), IsImplicit, LCK_VLAType);
1897         } else {
1898           assert(From.isVariableCapture() && "unknown kind of capture");
1899           ValueDecl *Var = From.getVariable();
1900           LambdaCaptureKind Kind =
1901               From.isCopyCapture() ? LCK_ByCopy : LCK_ByRef;
1902           return LambdaCapture(From.getLocation(), IsImplicit, Kind, Var,
1903                                From.getEllipsisLoc());
1904         }
1905       }();
1906 
1907       // Form the initializer for the capture field.
1908       ExprResult Init = BuildCaptureInit(From, ImplicitCaptureLoc);
1909 
1910       // FIXME: Skip this capture if the capture is not used, the initializer
1911       // has no side-effects, the type of the capture is trivial, and the
1912       // lambda is not externally visible.
1913 
1914       // Add a FieldDecl for the capture and form its initializer.
1915       BuildCaptureField(Class, From);
1916       Captures.push_back(Capture);
1917       CaptureInits.push_back(Init.get());
1918 
1919       if (LangOpts.CUDA)
1920         CUDACheckLambdaCapture(CallOperator, From);
1921     }
1922 
1923     Class->setCaptures(Context, Captures);
1924 
1925     // C++11 [expr.prim.lambda]p6:
1926     //   The closure type for a lambda-expression with no lambda-capture
1927     //   has a public non-virtual non-explicit const conversion function
1928     //   to pointer to function having the same parameter and return
1929     //   types as the closure type's function call operator.
1930     if (Captures.empty() && CaptureDefault == LCD_None)
1931       addFunctionPointerConversions(*this, IntroducerRange, Class,
1932                                     CallOperator);
1933 
1934     // Objective-C++:
1935     //   The closure type for a lambda-expression has a public non-virtual
1936     //   non-explicit const conversion function to a block pointer having the
1937     //   same parameter and return types as the closure type's function call
1938     //   operator.
1939     // FIXME: Fix generic lambda to block conversions.
1940     if (getLangOpts().Blocks && getLangOpts().ObjC && !IsGenericLambda)
1941       addBlockPointerConversion(*this, IntroducerRange, Class, CallOperator);
1942 
1943     // Finalize the lambda class.
1944     SmallVector<Decl*, 4> Fields(Class->fields());
1945     ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
1946                 SourceLocation(), ParsedAttributesView());
1947     CheckCompletedCXXClass(nullptr, Class);
1948   }
1949 
1950   Cleanup.mergeFrom(LambdaCleanup);
1951 
1952   LambdaExpr *Lambda = LambdaExpr::Create(Context, Class, IntroducerRange,
1953                                           CaptureDefault, CaptureDefaultLoc,
1954                                           ExplicitParams, ExplicitResultType,
1955                                           CaptureInits, EndLoc,
1956                                           ContainsUnexpandedParameterPack);
1957   // If the lambda expression's call operator is not explicitly marked constexpr
1958   // and we are not in a dependent context, analyze the call operator to infer
1959   // its constexpr-ness, suppressing diagnostics while doing so.
1960   if (getLangOpts().CPlusPlus17 && !CallOperator->isInvalidDecl() &&
1961       !CallOperator->isConstexpr() &&
1962       !isa<CoroutineBodyStmt>(CallOperator->getBody()) &&
1963       !Class->getDeclContext()->isDependentContext()) {
1964     CallOperator->setConstexprKind(
1965         CheckConstexprFunctionDefinition(CallOperator,
1966                                          CheckConstexprKind::CheckValid)
1967             ? ConstexprSpecKind::Constexpr
1968             : ConstexprSpecKind::Unspecified);
1969   }
1970 
1971   // Emit delayed shadowing warnings now that the full capture list is known.
1972   DiagnoseShadowingLambdaDecls(LSI);
1973 
1974   if (!CurContext->isDependentContext()) {
1975     switch (ExprEvalContexts.back().Context) {
1976     // C++11 [expr.prim.lambda]p2:
1977     //   A lambda-expression shall not appear in an unevaluated operand
1978     //   (Clause 5).
1979     case ExpressionEvaluationContext::Unevaluated:
1980     case ExpressionEvaluationContext::UnevaluatedList:
1981     case ExpressionEvaluationContext::UnevaluatedAbstract:
1982     // C++1y [expr.const]p2:
1983     //   A conditional-expression e is a core constant expression unless the
1984     //   evaluation of e, following the rules of the abstract machine, would
1985     //   evaluate [...] a lambda-expression.
1986     //
1987     // This is technically incorrect, there are some constant evaluated contexts
1988     // where this should be allowed.  We should probably fix this when DR1607 is
1989     // ratified, it lays out the exact set of conditions where we shouldn't
1990     // allow a lambda-expression.
1991     case ExpressionEvaluationContext::ConstantEvaluated:
1992     case ExpressionEvaluationContext::ImmediateFunctionContext:
1993       // We don't actually diagnose this case immediately, because we
1994       // could be within a context where we might find out later that
1995       // the expression is potentially evaluated (e.g., for typeid).
1996       ExprEvalContexts.back().Lambdas.push_back(Lambda);
1997       break;
1998 
1999     case ExpressionEvaluationContext::DiscardedStatement:
2000     case ExpressionEvaluationContext::PotentiallyEvaluated:
2001     case ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed:
2002       break;
2003     }
2004   }
2005 
2006   return MaybeBindToTemporary(Lambda);
2007 }
2008 
BuildBlockForLambdaConversion(SourceLocation CurrentLocation,SourceLocation ConvLocation,CXXConversionDecl * Conv,Expr * Src)2009 ExprResult Sema::BuildBlockForLambdaConversion(SourceLocation CurrentLocation,
2010                                                SourceLocation ConvLocation,
2011                                                CXXConversionDecl *Conv,
2012                                                Expr *Src) {
2013   // Make sure that the lambda call operator is marked used.
2014   CXXRecordDecl *Lambda = Conv->getParent();
2015   CXXMethodDecl *CallOperator
2016     = cast<CXXMethodDecl>(
2017         Lambda->lookup(
2018           Context.DeclarationNames.getCXXOperatorName(OO_Call)).front());
2019   CallOperator->setReferenced();
2020   CallOperator->markUsed(Context);
2021 
2022   ExprResult Init = PerformCopyInitialization(
2023       InitializedEntity::InitializeLambdaToBlock(ConvLocation, Src->getType()),
2024       CurrentLocation, Src);
2025   if (!Init.isInvalid())
2026     Init = ActOnFinishFullExpr(Init.get(), /*DiscardedValue*/ false);
2027 
2028   if (Init.isInvalid())
2029     return ExprError();
2030 
2031   // Create the new block to be returned.
2032   BlockDecl *Block = BlockDecl::Create(Context, CurContext, ConvLocation);
2033 
2034   // Set the type information.
2035   Block->setSignatureAsWritten(CallOperator->getTypeSourceInfo());
2036   Block->setIsVariadic(CallOperator->isVariadic());
2037   Block->setBlockMissingReturnType(false);
2038 
2039   // Add parameters.
2040   SmallVector<ParmVarDecl *, 4> BlockParams;
2041   for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I) {
2042     ParmVarDecl *From = CallOperator->getParamDecl(I);
2043     BlockParams.push_back(ParmVarDecl::Create(
2044         Context, Block, From->getBeginLoc(), From->getLocation(),
2045         From->getIdentifier(), From->getType(), From->getTypeSourceInfo(),
2046         From->getStorageClass(),
2047         /*DefArg=*/nullptr));
2048   }
2049   Block->setParams(BlockParams);
2050 
2051   Block->setIsConversionFromLambda(true);
2052 
2053   // Add capture. The capture uses a fake variable, which doesn't correspond
2054   // to any actual memory location. However, the initializer copy-initializes
2055   // the lambda object.
2056   TypeSourceInfo *CapVarTSI =
2057       Context.getTrivialTypeSourceInfo(Src->getType());
2058   VarDecl *CapVar = VarDecl::Create(Context, Block, ConvLocation,
2059                                     ConvLocation, nullptr,
2060                                     Src->getType(), CapVarTSI,
2061                                     SC_None);
2062   BlockDecl::Capture Capture(/*variable=*/CapVar, /*byRef=*/false,
2063                              /*nested=*/false, /*copy=*/Init.get());
2064   Block->setCaptures(Context, Capture, /*CapturesCXXThis=*/false);
2065 
2066   // Add a fake function body to the block. IR generation is responsible
2067   // for filling in the actual body, which cannot be expressed as an AST.
2068   Block->setBody(new (Context) CompoundStmt(ConvLocation));
2069 
2070   // Create the block literal expression.
2071   Expr *BuildBlock = new (Context) BlockExpr(Block, Conv->getConversionType());
2072   ExprCleanupObjects.push_back(Block);
2073   Cleanup.setExprNeedsCleanups(true);
2074 
2075   return BuildBlock;
2076 }
2077