xref: /freebsd/contrib/llvm-project/clang/lib/Sema/SemaLambda.cpp (revision 5b56413d04e608379c9a306373554a8e4d321bc0)
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 "clang/Sema/Template.h"
24 #include "llvm/ADT/STLExtras.h"
25 #include <optional>
26 using namespace clang;
27 using namespace sema;
28 
29 /// Examines the FunctionScopeInfo stack to determine the nearest
30 /// enclosing lambda (to the current lambda) that is 'capture-ready' for
31 /// the variable referenced in the current lambda (i.e. \p VarToCapture).
32 /// If successful, returns the index into Sema's FunctionScopeInfo stack
33 /// of the capture-ready lambda's LambdaScopeInfo.
34 ///
35 /// Climbs down the stack of lambdas (deepest nested lambda - i.e. current
36 /// lambda - is on top) to determine the index of the nearest enclosing/outer
37 /// lambda that is ready to capture the \p VarToCapture being referenced in
38 /// the current lambda.
39 /// As we climb down the stack, we want the index of the first such lambda -
40 /// that is the lambda with the highest index that is 'capture-ready'.
41 ///
42 /// A lambda 'L' is capture-ready for 'V' (var or this) if:
43 ///  - its enclosing context is non-dependent
44 ///  - and if the chain of lambdas between L and the lambda in which
45 ///    V is potentially used (i.e. the lambda at the top of the scope info
46 ///    stack), can all capture or have already captured V.
47 /// If \p VarToCapture is 'null' then we are trying to capture 'this'.
48 ///
49 /// Note that a lambda that is deemed 'capture-ready' still needs to be checked
50 /// for whether it is 'capture-capable' (see
51 /// getStackIndexOfNearestEnclosingCaptureCapableLambda), before it can truly
52 /// capture.
53 ///
54 /// \param FunctionScopes - Sema's stack of nested FunctionScopeInfo's (which a
55 ///  LambdaScopeInfo inherits from).  The current/deepest/innermost lambda
56 ///  is at the top of the stack and has the highest index.
57 /// \param VarToCapture - the variable to capture.  If NULL, capture 'this'.
58 ///
59 /// \returns An std::optional<unsigned> Index that if evaluates to 'true'
60 /// contains the index (into Sema's FunctionScopeInfo stack) of the innermost
61 /// lambda which is capture-ready.  If the return value evaluates to 'false'
62 /// then no lambda is capture-ready for \p VarToCapture.
63 
64 static inline std::optional<unsigned>
65 getStackIndexOfNearestEnclosingCaptureReadyLambda(
66     ArrayRef<const clang::sema::FunctionScopeInfo *> FunctionScopes,
67     ValueDecl *VarToCapture) {
68   // Label failure to capture.
69   const std::optional<unsigned> NoLambdaIsCaptureReady;
70 
71   // Ignore all inner captured regions.
72   unsigned CurScopeIndex = FunctionScopes.size() - 1;
73   while (CurScopeIndex > 0 && isa<clang::sema::CapturedRegionScopeInfo>(
74                                   FunctionScopes[CurScopeIndex]))
75     --CurScopeIndex;
76   assert(
77       isa<clang::sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex]) &&
78       "The function on the top of sema's function-info stack must be a lambda");
79 
80   // If VarToCapture is null, we are attempting to capture 'this'.
81   const bool IsCapturingThis = !VarToCapture;
82   const bool IsCapturingVariable = !IsCapturingThis;
83 
84   // Start with the current lambda at the top of the stack (highest index).
85   DeclContext *EnclosingDC =
86       cast<sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex])->CallOperator;
87 
88   do {
89     const clang::sema::LambdaScopeInfo *LSI =
90         cast<sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex]);
91     // IF we have climbed down to an intervening enclosing lambda that contains
92     // the variable declaration - it obviously can/must not capture the
93     // variable.
94     // Since its enclosing DC is dependent, all the lambdas between it and the
95     // innermost nested lambda are dependent (otherwise we wouldn't have
96     // arrived here) - so we don't yet have a lambda that can capture the
97     // variable.
98     if (IsCapturingVariable &&
99         VarToCapture->getDeclContext()->Equals(EnclosingDC))
100       return NoLambdaIsCaptureReady;
101 
102     // For an enclosing lambda to be capture ready for an entity, all
103     // intervening lambda's have to be able to capture that entity. If even
104     // one of the intervening lambda's is not capable of capturing the entity
105     // then no enclosing lambda can ever capture that entity.
106     // For e.g.
107     // const int x = 10;
108     // [=](auto a) {    #1
109     //   [](auto b) {   #2 <-- an intervening lambda that can never capture 'x'
110     //    [=](auto c) { #3
111     //       f(x, c);  <-- can not lead to x's speculative capture by #1 or #2
112     //    }; }; };
113     // If they do not have a default implicit capture, check to see
114     // if the entity has already been explicitly captured.
115     // If even a single dependent enclosing lambda lacks the capability
116     // to ever capture this variable, there is no further enclosing
117     // non-dependent lambda that can capture this variable.
118     if (LSI->ImpCaptureStyle == sema::LambdaScopeInfo::ImpCap_None) {
119       if (IsCapturingVariable && !LSI->isCaptured(VarToCapture))
120         return NoLambdaIsCaptureReady;
121       if (IsCapturingThis && !LSI->isCXXThisCaptured())
122         return NoLambdaIsCaptureReady;
123     }
124     EnclosingDC = getLambdaAwareParentOfDeclContext(EnclosingDC);
125 
126     assert(CurScopeIndex);
127     --CurScopeIndex;
128   } while (!EnclosingDC->isTranslationUnit() &&
129            EnclosingDC->isDependentContext() &&
130            isLambdaCallOperator(EnclosingDC));
131 
132   assert(CurScopeIndex < (FunctionScopes.size() - 1));
133   // If the enclosingDC is not dependent, then the immediately nested lambda
134   // (one index above) is capture-ready.
135   if (!EnclosingDC->isDependentContext())
136     return CurScopeIndex + 1;
137   return NoLambdaIsCaptureReady;
138 }
139 
140 /// Examines the FunctionScopeInfo stack to determine the nearest
141 /// enclosing lambda (to the current lambda) that is 'capture-capable' for
142 /// the variable referenced in the current lambda (i.e. \p VarToCapture).
143 /// If successful, returns the index into Sema's FunctionScopeInfo stack
144 /// of the capture-capable lambda's LambdaScopeInfo.
145 ///
146 /// Given the current stack of lambdas being processed by Sema and
147 /// the variable of interest, to identify the nearest enclosing lambda (to the
148 /// current lambda at the top of the stack) that can truly capture
149 /// a variable, it has to have the following two properties:
150 ///  a) 'capture-ready' - be the innermost lambda that is 'capture-ready':
151 ///     - climb down the stack (i.e. starting from the innermost and examining
152 ///       each outer lambda step by step) checking if each enclosing
153 ///       lambda can either implicitly or explicitly capture the variable.
154 ///       Record the first such lambda that is enclosed in a non-dependent
155 ///       context. If no such lambda currently exists return failure.
156 ///  b) 'capture-capable' - make sure the 'capture-ready' lambda can truly
157 ///  capture the variable by checking all its enclosing lambdas:
158 ///     - check if all outer lambdas enclosing the 'capture-ready' lambda
159 ///       identified above in 'a' can also capture the variable (this is done
160 ///       via tryCaptureVariable for variables and CheckCXXThisCapture for
161 ///       'this' by passing in the index of the Lambda identified in step 'a')
162 ///
163 /// \param FunctionScopes - Sema's stack of nested FunctionScopeInfo's (which a
164 /// LambdaScopeInfo inherits from).  The current/deepest/innermost lambda
165 /// is at the top of the stack.
166 ///
167 /// \param VarToCapture - the variable to capture.  If NULL, capture 'this'.
168 ///
169 ///
170 /// \returns An std::optional<unsigned> Index that if evaluates to 'true'
171 /// contains the index (into Sema's FunctionScopeInfo stack) of the innermost
172 /// lambda which is capture-capable.  If the return value evaluates to 'false'
173 /// then no lambda is capture-capable for \p VarToCapture.
174 
175 std::optional<unsigned>
176 clang::getStackIndexOfNearestEnclosingCaptureCapableLambda(
177     ArrayRef<const sema::FunctionScopeInfo *> FunctionScopes,
178     ValueDecl *VarToCapture, Sema &S) {
179 
180   const std::optional<unsigned> NoLambdaIsCaptureCapable;
181 
182   const std::optional<unsigned> OptionalStackIndex =
183       getStackIndexOfNearestEnclosingCaptureReadyLambda(FunctionScopes,
184                                                         VarToCapture);
185   if (!OptionalStackIndex)
186     return NoLambdaIsCaptureCapable;
187 
188   const unsigned IndexOfCaptureReadyLambda = *OptionalStackIndex;
189   assert(((IndexOfCaptureReadyLambda != (FunctionScopes.size() - 1)) ||
190           S.getCurGenericLambda()) &&
191          "The capture ready lambda for a potential capture can only be the "
192          "current lambda if it is a generic lambda");
193 
194   const sema::LambdaScopeInfo *const CaptureReadyLambdaLSI =
195       cast<sema::LambdaScopeInfo>(FunctionScopes[IndexOfCaptureReadyLambda]);
196 
197   // If VarToCapture is null, we are attempting to capture 'this'
198   const bool IsCapturingThis = !VarToCapture;
199   const bool IsCapturingVariable = !IsCapturingThis;
200 
201   if (IsCapturingVariable) {
202     // Check if the capture-ready lambda can truly capture the variable, by
203     // checking whether all enclosing lambdas of the capture-ready lambda allow
204     // the capture - i.e. make sure it is capture-capable.
205     QualType CaptureType, DeclRefType;
206     const bool CanCaptureVariable =
207         !S.tryCaptureVariable(VarToCapture,
208                               /*ExprVarIsUsedInLoc*/ SourceLocation(),
209                               clang::Sema::TryCapture_Implicit,
210                               /*EllipsisLoc*/ SourceLocation(),
211                               /*BuildAndDiagnose*/ false, CaptureType,
212                               DeclRefType, &IndexOfCaptureReadyLambda);
213     if (!CanCaptureVariable)
214       return NoLambdaIsCaptureCapable;
215   } else {
216     // Check if the capture-ready lambda can truly capture 'this' by checking
217     // whether all enclosing lambdas of the capture-ready lambda can capture
218     // 'this'.
219     const bool CanCaptureThis =
220         !S.CheckCXXThisCapture(
221              CaptureReadyLambdaLSI->PotentialThisCaptureLocation,
222              /*Explicit*/ false, /*BuildAndDiagnose*/ false,
223              &IndexOfCaptureReadyLambda);
224     if (!CanCaptureThis)
225       return NoLambdaIsCaptureCapable;
226   }
227   return IndexOfCaptureReadyLambda;
228 }
229 
230 static inline TemplateParameterList *
231 getGenericLambdaTemplateParameterList(LambdaScopeInfo *LSI, Sema &SemaRef) {
232   if (!LSI->GLTemplateParameterList && !LSI->TemplateParams.empty()) {
233     LSI->GLTemplateParameterList = TemplateParameterList::Create(
234         SemaRef.Context,
235         /*Template kw loc*/ SourceLocation(),
236         /*L angle loc*/ LSI->ExplicitTemplateParamsRange.getBegin(),
237         LSI->TemplateParams,
238         /*R angle loc*/LSI->ExplicitTemplateParamsRange.getEnd(),
239         LSI->RequiresClause.get());
240   }
241   return LSI->GLTemplateParameterList;
242 }
243 
244 CXXRecordDecl *
245 Sema::createLambdaClosureType(SourceRange IntroducerRange, TypeSourceInfo *Info,
246                               unsigned LambdaDependencyKind,
247                               LambdaCaptureDefault CaptureDefault) {
248   DeclContext *DC = CurContext;
249   while (!(DC->isFunctionOrMethod() || DC->isRecord() || DC->isFileContext()))
250     DC = DC->getParent();
251 
252   bool IsGenericLambda =
253       Info && getGenericLambdaTemplateParameterList(getCurLambda(), *this);
254   // Start constructing the lambda class.
255   CXXRecordDecl *Class = CXXRecordDecl::CreateLambda(
256       Context, DC, Info, IntroducerRange.getBegin(), LambdaDependencyKind,
257       IsGenericLambda, CaptureDefault);
258   DC->addDecl(Class);
259 
260   return Class;
261 }
262 
263 /// Determine whether the given context is or is enclosed in an inline
264 /// function.
265 static bool isInInlineFunction(const DeclContext *DC) {
266   while (!DC->isFileContext()) {
267     if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(DC))
268       if (FD->isInlined())
269         return true;
270 
271     DC = DC->getLexicalParent();
272   }
273 
274   return false;
275 }
276 
277 std::tuple<MangleNumberingContext *, Decl *>
278 Sema::getCurrentMangleNumberContext(const DeclContext *DC) {
279   // Compute the context for allocating mangling numbers in the current
280   // expression, if the ABI requires them.
281   Decl *ManglingContextDecl = ExprEvalContexts.back().ManglingContextDecl;
282 
283   enum ContextKind {
284     Normal,
285     DefaultArgument,
286     DataMember,
287     InlineVariable,
288     TemplatedVariable,
289     Concept
290   } Kind = Normal;
291 
292   bool IsInNonspecializedTemplate =
293       inTemplateInstantiation() || CurContext->isDependentContext();
294 
295   // Default arguments of member function parameters that appear in a class
296   // definition, as well as the initializers of data members, receive special
297   // treatment. Identify them.
298   if (ManglingContextDecl) {
299     if (ParmVarDecl *Param = dyn_cast<ParmVarDecl>(ManglingContextDecl)) {
300       if (const DeclContext *LexicalDC
301           = Param->getDeclContext()->getLexicalParent())
302         if (LexicalDC->isRecord())
303           Kind = DefaultArgument;
304     } else if (VarDecl *Var = dyn_cast<VarDecl>(ManglingContextDecl)) {
305       if (Var->getMostRecentDecl()->isInline())
306         Kind = InlineVariable;
307       else if (Var->getDeclContext()->isRecord() && IsInNonspecializedTemplate)
308         Kind = TemplatedVariable;
309       else if (Var->getDescribedVarTemplate())
310         Kind = TemplatedVariable;
311       else if (auto *VTS = dyn_cast<VarTemplateSpecializationDecl>(Var)) {
312         if (!VTS->isExplicitSpecialization())
313           Kind = TemplatedVariable;
314       }
315     } else if (isa<FieldDecl>(ManglingContextDecl)) {
316       Kind = DataMember;
317     } else if (isa<ImplicitConceptSpecializationDecl>(ManglingContextDecl)) {
318       Kind = Concept;
319     }
320   }
321 
322   // Itanium ABI [5.1.7]:
323   //   In the following contexts [...] the one-definition rule requires closure
324   //   types in different translation units to "correspond":
325   switch (Kind) {
326   case Normal: {
327     //  -- the bodies of inline or templated functions
328     if ((IsInNonspecializedTemplate &&
329          !(ManglingContextDecl && isa<ParmVarDecl>(ManglingContextDecl))) ||
330         isInInlineFunction(CurContext)) {
331       while (auto *CD = dyn_cast<CapturedDecl>(DC))
332         DC = CD->getParent();
333       return std::make_tuple(&Context.getManglingNumberContext(DC), nullptr);
334     }
335 
336     return std::make_tuple(nullptr, nullptr);
337   }
338 
339   case Concept:
340     // Concept definitions aren't code generated and thus aren't mangled,
341     // however the ManglingContextDecl is important for the purposes of
342     // re-forming the template argument list of the lambda for constraint
343     // evaluation.
344   case DataMember:
345     //  -- default member initializers
346   case DefaultArgument:
347     //  -- default arguments appearing in class definitions
348   case InlineVariable:
349   case TemplatedVariable:
350     //  -- the initializers of inline or templated variables
351     return std::make_tuple(
352         &Context.getManglingNumberContext(ASTContext::NeedExtraManglingDecl,
353                                           ManglingContextDecl),
354         ManglingContextDecl);
355   }
356 
357   llvm_unreachable("unexpected context");
358 }
359 
360 static QualType
361 buildTypeForLambdaCallOperator(Sema &S, clang::CXXRecordDecl *Class,
362                                TemplateParameterList *TemplateParams,
363                                TypeSourceInfo *MethodTypeInfo) {
364   assert(MethodTypeInfo && "expected a non null type");
365 
366   QualType MethodType = MethodTypeInfo->getType();
367   // If a lambda appears in a dependent context or is a generic lambda (has
368   // template parameters) and has an 'auto' return type, deduce it to a
369   // dependent type.
370   if (Class->isDependentContext() || TemplateParams) {
371     const FunctionProtoType *FPT = MethodType->castAs<FunctionProtoType>();
372     QualType Result = FPT->getReturnType();
373     if (Result->isUndeducedType()) {
374       Result = S.SubstAutoTypeDependent(Result);
375       MethodType = S.Context.getFunctionType(Result, FPT->getParamTypes(),
376                                              FPT->getExtProtoInfo());
377     }
378   }
379   return MethodType;
380 }
381 
382 // [C++2b] [expr.prim.lambda.closure] p4
383 //  Given a lambda with a lambda-capture, the type of the explicit object
384 //  parameter, if any, of the lambda's function call operator (possibly
385 //  instantiated from a function call operator template) shall be either:
386 //  - the closure type,
387 //  - class type derived from the closure type, or
388 //  - a reference to a possibly cv-qualified such type.
389 void Sema::DiagnoseInvalidExplicitObjectParameterInLambda(
390     CXXMethodDecl *Method) {
391   if (!isLambdaCallWithExplicitObjectParameter(Method))
392     return;
393   CXXRecordDecl *RD = Method->getParent();
394   if (Method->getType()->isDependentType())
395     return;
396   if (RD->isCapturelessLambda())
397     return;
398   QualType ExplicitObjectParameterType = Method->getParamDecl(0)
399                                              ->getType()
400                                              .getNonReferenceType()
401                                              .getUnqualifiedType()
402                                              .getDesugaredType(getASTContext());
403   QualType LambdaType = getASTContext().getRecordType(RD);
404   if (LambdaType == ExplicitObjectParameterType)
405     return;
406   if (IsDerivedFrom(RD->getLocation(), ExplicitObjectParameterType, LambdaType))
407     return;
408   Diag(Method->getParamDecl(0)->getLocation(),
409        diag::err_invalid_explicit_object_type_in_lambda)
410       << ExplicitObjectParameterType;
411 }
412 
413 void Sema::handleLambdaNumbering(
414     CXXRecordDecl *Class, CXXMethodDecl *Method,
415     std::optional<CXXRecordDecl::LambdaNumbering> NumberingOverride) {
416   if (NumberingOverride) {
417     Class->setLambdaNumbering(*NumberingOverride);
418     return;
419   }
420 
421   ContextRAII ManglingContext(*this, Class->getDeclContext());
422 
423   auto getMangleNumberingContext =
424       [this](CXXRecordDecl *Class,
425              Decl *ManglingContextDecl) -> MangleNumberingContext * {
426     // Get mangle numbering context if there's any extra decl context.
427     if (ManglingContextDecl)
428       return &Context.getManglingNumberContext(
429           ASTContext::NeedExtraManglingDecl, ManglingContextDecl);
430     // Otherwise, from that lambda's decl context.
431     auto DC = Class->getDeclContext();
432     while (auto *CD = dyn_cast<CapturedDecl>(DC))
433       DC = CD->getParent();
434     return &Context.getManglingNumberContext(DC);
435   };
436 
437   CXXRecordDecl::LambdaNumbering Numbering;
438   MangleNumberingContext *MCtx;
439   std::tie(MCtx, Numbering.ContextDecl) =
440       getCurrentMangleNumberContext(Class->getDeclContext());
441   if (!MCtx && (getLangOpts().CUDA || getLangOpts().SYCLIsDevice ||
442                 getLangOpts().SYCLIsHost)) {
443     // Force lambda numbering in CUDA/HIP as we need to name lambdas following
444     // ODR. Both device- and host-compilation need to have a consistent naming
445     // on kernel functions. As lambdas are potential part of these `__global__`
446     // function names, they needs numbering following ODR.
447     // Also force for SYCL, since we need this for the
448     // __builtin_sycl_unique_stable_name implementation, which depends on lambda
449     // mangling.
450     MCtx = getMangleNumberingContext(Class, Numbering.ContextDecl);
451     assert(MCtx && "Retrieving mangle numbering context failed!");
452     Numbering.HasKnownInternalLinkage = true;
453   }
454   if (MCtx) {
455     Numbering.IndexInContext = MCtx->getNextLambdaIndex();
456     Numbering.ManglingNumber = MCtx->getManglingNumber(Method);
457     Numbering.DeviceManglingNumber = MCtx->getDeviceManglingNumber(Method);
458     Class->setLambdaNumbering(Numbering);
459 
460     if (auto *Source =
461             dyn_cast_or_null<ExternalSemaSource>(Context.getExternalSource()))
462       Source->AssignedLambdaNumbering(Class);
463   }
464 }
465 
466 static void buildLambdaScopeReturnType(Sema &S, LambdaScopeInfo *LSI,
467                                        CXXMethodDecl *CallOperator,
468                                        bool ExplicitResultType) {
469   if (ExplicitResultType) {
470     LSI->HasImplicitReturnType = false;
471     LSI->ReturnType = CallOperator->getReturnType();
472     if (!LSI->ReturnType->isDependentType() && !LSI->ReturnType->isVoidType())
473       S.RequireCompleteType(CallOperator->getBeginLoc(), LSI->ReturnType,
474                             diag::err_lambda_incomplete_result);
475   } else {
476     LSI->HasImplicitReturnType = true;
477   }
478 }
479 
480 void Sema::buildLambdaScope(LambdaScopeInfo *LSI, CXXMethodDecl *CallOperator,
481                             SourceRange IntroducerRange,
482                             LambdaCaptureDefault CaptureDefault,
483                             SourceLocation CaptureDefaultLoc,
484                             bool ExplicitParams, bool Mutable) {
485   LSI->CallOperator = CallOperator;
486   CXXRecordDecl *LambdaClass = CallOperator->getParent();
487   LSI->Lambda = LambdaClass;
488   if (CaptureDefault == LCD_ByCopy)
489     LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByval;
490   else if (CaptureDefault == LCD_ByRef)
491     LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByref;
492   LSI->CaptureDefaultLoc = CaptureDefaultLoc;
493   LSI->IntroducerRange = IntroducerRange;
494   LSI->ExplicitParams = ExplicitParams;
495   LSI->Mutable = Mutable;
496 }
497 
498 void Sema::finishLambdaExplicitCaptures(LambdaScopeInfo *LSI) {
499   LSI->finishedExplicitCaptures();
500 }
501 
502 void Sema::ActOnLambdaExplicitTemplateParameterList(
503     LambdaIntroducer &Intro, SourceLocation LAngleLoc,
504     ArrayRef<NamedDecl *> TParams, SourceLocation RAngleLoc,
505     ExprResult RequiresClause) {
506   LambdaScopeInfo *LSI = getCurLambda();
507   assert(LSI && "Expected a lambda scope");
508   assert(LSI->NumExplicitTemplateParams == 0 &&
509          "Already acted on explicit template parameters");
510   assert(LSI->TemplateParams.empty() &&
511          "Explicit template parameters should come "
512          "before invented (auto) ones");
513   assert(!TParams.empty() &&
514          "No template parameters to act on");
515   LSI->TemplateParams.append(TParams.begin(), TParams.end());
516   LSI->NumExplicitTemplateParams = TParams.size();
517   LSI->ExplicitTemplateParamsRange = {LAngleLoc, RAngleLoc};
518   LSI->RequiresClause = RequiresClause;
519 }
520 
521 /// If this expression is an enumerator-like expression of some type
522 /// T, return the type T; otherwise, return null.
523 ///
524 /// Pointer comparisons on the result here should always work because
525 /// it's derived from either the parent of an EnumConstantDecl
526 /// (i.e. the definition) or the declaration returned by
527 /// EnumType::getDecl() (i.e. the definition).
528 static EnumDecl *findEnumForBlockReturn(Expr *E) {
529   // An expression is an enumerator-like expression of type T if,
530   // ignoring parens and parens-like expressions:
531   E = E->IgnoreParens();
532 
533   //  - it is an enumerator whose enum type is T or
534   if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
535     if (EnumConstantDecl *D
536           = dyn_cast<EnumConstantDecl>(DRE->getDecl())) {
537       return cast<EnumDecl>(D->getDeclContext());
538     }
539     return nullptr;
540   }
541 
542   //  - it is a comma expression whose RHS is an enumerator-like
543   //    expression of type T or
544   if (BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
545     if (BO->getOpcode() == BO_Comma)
546       return findEnumForBlockReturn(BO->getRHS());
547     return nullptr;
548   }
549 
550   //  - it is a statement-expression whose value expression is an
551   //    enumerator-like expression of type T or
552   if (StmtExpr *SE = dyn_cast<StmtExpr>(E)) {
553     if (Expr *last = dyn_cast_or_null<Expr>(SE->getSubStmt()->body_back()))
554       return findEnumForBlockReturn(last);
555     return nullptr;
556   }
557 
558   //   - it is a ternary conditional operator (not the GNU ?:
559   //     extension) whose second and third operands are
560   //     enumerator-like expressions of type T or
561   if (ConditionalOperator *CO = dyn_cast<ConditionalOperator>(E)) {
562     if (EnumDecl *ED = findEnumForBlockReturn(CO->getTrueExpr()))
563       if (ED == findEnumForBlockReturn(CO->getFalseExpr()))
564         return ED;
565     return nullptr;
566   }
567 
568   // (implicitly:)
569   //   - it is an implicit integral conversion applied to an
570   //     enumerator-like expression of type T or
571   if (ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(E)) {
572     // We can sometimes see integral conversions in valid
573     // enumerator-like expressions.
574     if (ICE->getCastKind() == CK_IntegralCast)
575       return findEnumForBlockReturn(ICE->getSubExpr());
576 
577     // Otherwise, just rely on the type.
578   }
579 
580   //   - it is an expression of that formal enum type.
581   if (const EnumType *ET = E->getType()->getAs<EnumType>()) {
582     return ET->getDecl();
583   }
584 
585   // Otherwise, nope.
586   return nullptr;
587 }
588 
589 /// Attempt to find a type T for which the returned expression of the
590 /// given statement is an enumerator-like expression of that type.
591 static EnumDecl *findEnumForBlockReturn(ReturnStmt *ret) {
592   if (Expr *retValue = ret->getRetValue())
593     return findEnumForBlockReturn(retValue);
594   return nullptr;
595 }
596 
597 /// Attempt to find a common type T for which all of the returned
598 /// expressions in a block are enumerator-like expressions of that
599 /// type.
600 static EnumDecl *findCommonEnumForBlockReturns(ArrayRef<ReturnStmt*> returns) {
601   ArrayRef<ReturnStmt*>::iterator i = returns.begin(), e = returns.end();
602 
603   // Try to find one for the first return.
604   EnumDecl *ED = findEnumForBlockReturn(*i);
605   if (!ED) return nullptr;
606 
607   // Check that the rest of the returns have the same enum.
608   for (++i; i != e; ++i) {
609     if (findEnumForBlockReturn(*i) != ED)
610       return nullptr;
611   }
612 
613   // Never infer an anonymous enum type.
614   if (!ED->hasNameForLinkage()) return nullptr;
615 
616   return ED;
617 }
618 
619 /// Adjust the given return statements so that they formally return
620 /// the given type.  It should require, at most, an IntegralCast.
621 static void adjustBlockReturnsToEnum(Sema &S, ArrayRef<ReturnStmt*> returns,
622                                      QualType returnType) {
623   for (ArrayRef<ReturnStmt*>::iterator
624          i = returns.begin(), e = returns.end(); i != e; ++i) {
625     ReturnStmt *ret = *i;
626     Expr *retValue = ret->getRetValue();
627     if (S.Context.hasSameType(retValue->getType(), returnType))
628       continue;
629 
630     // Right now we only support integral fixup casts.
631     assert(returnType->isIntegralOrUnscopedEnumerationType());
632     assert(retValue->getType()->isIntegralOrUnscopedEnumerationType());
633 
634     ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(retValue);
635 
636     Expr *E = (cleanups ? cleanups->getSubExpr() : retValue);
637     E = ImplicitCastExpr::Create(S.Context, returnType, CK_IntegralCast, E,
638                                  /*base path*/ nullptr, VK_PRValue,
639                                  FPOptionsOverride());
640     if (cleanups) {
641       cleanups->setSubExpr(E);
642     } else {
643       ret->setRetValue(E);
644     }
645   }
646 }
647 
648 void Sema::deduceClosureReturnType(CapturingScopeInfo &CSI) {
649   assert(CSI.HasImplicitReturnType);
650   // If it was ever a placeholder, it had to been deduced to DependentTy.
651   assert(CSI.ReturnType.isNull() || !CSI.ReturnType->isUndeducedType());
652   assert((!isa<LambdaScopeInfo>(CSI) || !getLangOpts().CPlusPlus14) &&
653          "lambda expressions use auto deduction in C++14 onwards");
654 
655   // C++ core issue 975:
656   //   If a lambda-expression does not include a trailing-return-type,
657   //   it is as if the trailing-return-type denotes the following type:
658   //     - if there are no return statements in the compound-statement,
659   //       or all return statements return either an expression of type
660   //       void or no expression or braced-init-list, the type void;
661   //     - otherwise, if all return statements return an expression
662   //       and the types of the returned expressions after
663   //       lvalue-to-rvalue conversion (4.1 [conv.lval]),
664   //       array-to-pointer conversion (4.2 [conv.array]), and
665   //       function-to-pointer conversion (4.3 [conv.func]) are the
666   //       same, that common type;
667   //     - otherwise, the program is ill-formed.
668   //
669   // C++ core issue 1048 additionally removes top-level cv-qualifiers
670   // from the types of returned expressions to match the C++14 auto
671   // deduction rules.
672   //
673   // In addition, in blocks in non-C++ modes, if all of the return
674   // statements are enumerator-like expressions of some type T, where
675   // T has a name for linkage, then we infer the return type of the
676   // block to be that type.
677 
678   // First case: no return statements, implicit void return type.
679   ASTContext &Ctx = getASTContext();
680   if (CSI.Returns.empty()) {
681     // It's possible there were simply no /valid/ return statements.
682     // In this case, the first one we found may have at least given us a type.
683     if (CSI.ReturnType.isNull())
684       CSI.ReturnType = Ctx.VoidTy;
685     return;
686   }
687 
688   // Second case: at least one return statement has dependent type.
689   // Delay type checking until instantiation.
690   assert(!CSI.ReturnType.isNull() && "We should have a tentative return type.");
691   if (CSI.ReturnType->isDependentType())
692     return;
693 
694   // Try to apply the enum-fuzz rule.
695   if (!getLangOpts().CPlusPlus) {
696     assert(isa<BlockScopeInfo>(CSI));
697     const EnumDecl *ED = findCommonEnumForBlockReturns(CSI.Returns);
698     if (ED) {
699       CSI.ReturnType = Context.getTypeDeclType(ED);
700       adjustBlockReturnsToEnum(*this, CSI.Returns, CSI.ReturnType);
701       return;
702     }
703   }
704 
705   // Third case: only one return statement. Don't bother doing extra work!
706   if (CSI.Returns.size() == 1)
707     return;
708 
709   // General case: many return statements.
710   // Check that they all have compatible return types.
711 
712   // We require the return types to strictly match here.
713   // Note that we've already done the required promotions as part of
714   // processing the return statement.
715   for (const ReturnStmt *RS : CSI.Returns) {
716     const Expr *RetE = RS->getRetValue();
717 
718     QualType ReturnType =
719         (RetE ? RetE->getType() : Context.VoidTy).getUnqualifiedType();
720     if (Context.getCanonicalFunctionResultType(ReturnType) ==
721           Context.getCanonicalFunctionResultType(CSI.ReturnType)) {
722       // Use the return type with the strictest possible nullability annotation.
723       auto RetTyNullability = ReturnType->getNullability();
724       auto BlockNullability = CSI.ReturnType->getNullability();
725       if (BlockNullability &&
726           (!RetTyNullability ||
727            hasWeakerNullability(*RetTyNullability, *BlockNullability)))
728         CSI.ReturnType = ReturnType;
729       continue;
730     }
731 
732     // FIXME: This is a poor diagnostic for ReturnStmts without expressions.
733     // TODO: It's possible that the *first* return is the divergent one.
734     Diag(RS->getBeginLoc(),
735          diag::err_typecheck_missing_return_type_incompatible)
736         << ReturnType << CSI.ReturnType << isa<LambdaScopeInfo>(CSI);
737     // Continue iterating so that we keep emitting diagnostics.
738   }
739 }
740 
741 QualType Sema::buildLambdaInitCaptureInitialization(
742     SourceLocation Loc, bool ByRef, SourceLocation EllipsisLoc,
743     std::optional<unsigned> NumExpansions, IdentifierInfo *Id,
744     bool IsDirectInit, Expr *&Init) {
745   // Create an 'auto' or 'auto&' TypeSourceInfo that we can use to
746   // deduce against.
747   QualType DeductType = Context.getAutoDeductType();
748   TypeLocBuilder TLB;
749   AutoTypeLoc TL = TLB.push<AutoTypeLoc>(DeductType);
750   TL.setNameLoc(Loc);
751   if (ByRef) {
752     DeductType = BuildReferenceType(DeductType, true, Loc, Id);
753     assert(!DeductType.isNull() && "can't build reference to auto");
754     TLB.push<ReferenceTypeLoc>(DeductType).setSigilLoc(Loc);
755   }
756   if (EllipsisLoc.isValid()) {
757     if (Init->containsUnexpandedParameterPack()) {
758       Diag(EllipsisLoc, getLangOpts().CPlusPlus20
759                             ? diag::warn_cxx17_compat_init_capture_pack
760                             : diag::ext_init_capture_pack);
761       DeductType = Context.getPackExpansionType(DeductType, NumExpansions,
762                                                 /*ExpectPackInType=*/false);
763       TLB.push<PackExpansionTypeLoc>(DeductType).setEllipsisLoc(EllipsisLoc);
764     } else {
765       // Just ignore the ellipsis for now and form a non-pack variable. We'll
766       // diagnose this later when we try to capture it.
767     }
768   }
769   TypeSourceInfo *TSI = TLB.getTypeSourceInfo(Context, DeductType);
770 
771   // Deduce the type of the init capture.
772   QualType DeducedType = deduceVarTypeFromInitializer(
773       /*VarDecl*/nullptr, DeclarationName(Id), DeductType, TSI,
774       SourceRange(Loc, Loc), IsDirectInit, Init);
775   if (DeducedType.isNull())
776     return QualType();
777 
778   // Are we a non-list direct initialization?
779   ParenListExpr *CXXDirectInit = dyn_cast<ParenListExpr>(Init);
780 
781   // Perform initialization analysis and ensure any implicit conversions
782   // (such as lvalue-to-rvalue) are enforced.
783   InitializedEntity Entity =
784       InitializedEntity::InitializeLambdaCapture(Id, DeducedType, Loc);
785   InitializationKind Kind =
786       IsDirectInit
787           ? (CXXDirectInit ? InitializationKind::CreateDirect(
788                                  Loc, Init->getBeginLoc(), Init->getEndLoc())
789                            : InitializationKind::CreateDirectList(Loc))
790           : InitializationKind::CreateCopy(Loc, Init->getBeginLoc());
791 
792   MultiExprArg Args = Init;
793   if (CXXDirectInit)
794     Args =
795         MultiExprArg(CXXDirectInit->getExprs(), CXXDirectInit->getNumExprs());
796   QualType DclT;
797   InitializationSequence InitSeq(*this, Entity, Kind, Args);
798   ExprResult Result = InitSeq.Perform(*this, Entity, Kind, Args, &DclT);
799 
800   if (Result.isInvalid())
801     return QualType();
802 
803   Init = Result.getAs<Expr>();
804   return DeducedType;
805 }
806 
807 VarDecl *Sema::createLambdaInitCaptureVarDecl(
808     SourceLocation Loc, QualType InitCaptureType, SourceLocation EllipsisLoc,
809     IdentifierInfo *Id, unsigned InitStyle, Expr *Init, DeclContext *DeclCtx) {
810   // FIXME: Retain the TypeSourceInfo from buildLambdaInitCaptureInitialization
811   // rather than reconstructing it here.
812   TypeSourceInfo *TSI = Context.getTrivialTypeSourceInfo(InitCaptureType, Loc);
813   if (auto PETL = TSI->getTypeLoc().getAs<PackExpansionTypeLoc>())
814     PETL.setEllipsisLoc(EllipsisLoc);
815 
816   // Create a dummy variable representing the init-capture. This is not actually
817   // used as a variable, and only exists as a way to name and refer to the
818   // init-capture.
819   // FIXME: Pass in separate source locations for '&' and identifier.
820   VarDecl *NewVD = VarDecl::Create(Context, DeclCtx, Loc, Loc, Id,
821                                    InitCaptureType, TSI, SC_Auto);
822   NewVD->setInitCapture(true);
823   NewVD->setReferenced(true);
824   // FIXME: Pass in a VarDecl::InitializationStyle.
825   NewVD->setInitStyle(static_cast<VarDecl::InitializationStyle>(InitStyle));
826   NewVD->markUsed(Context);
827   NewVD->setInit(Init);
828   if (NewVD->isParameterPack())
829     getCurLambda()->LocalPacks.push_back(NewVD);
830   return NewVD;
831 }
832 
833 void Sema::addInitCapture(LambdaScopeInfo *LSI, VarDecl *Var, bool ByRef) {
834   assert(Var->isInitCapture() && "init capture flag should be set");
835   LSI->addCapture(Var, /*isBlock=*/false, ByRef,
836                   /*isNested=*/false, Var->getLocation(), SourceLocation(),
837                   Var->getType(), /*Invalid=*/false);
838 }
839 
840 // Unlike getCurLambda, getCurrentLambdaScopeUnsafe doesn't
841 // check that the current lambda is in a consistent or fully constructed state.
842 static LambdaScopeInfo *getCurrentLambdaScopeUnsafe(Sema &S) {
843   assert(!S.FunctionScopes.empty());
844   return cast<LambdaScopeInfo>(S.FunctionScopes[S.FunctionScopes.size() - 1]);
845 }
846 
847 static TypeSourceInfo *
848 getDummyLambdaType(Sema &S, SourceLocation Loc = SourceLocation()) {
849   // C++11 [expr.prim.lambda]p4:
850   //   If a lambda-expression does not include a lambda-declarator, it is as
851   //   if the lambda-declarator were ().
852   FunctionProtoType::ExtProtoInfo EPI(S.Context.getDefaultCallingConvention(
853       /*IsVariadic=*/false, /*IsCXXMethod=*/true));
854   EPI.HasTrailingReturn = true;
855   EPI.TypeQuals.addConst();
856   LangAS AS = S.getDefaultCXXMethodAddrSpace();
857   if (AS != LangAS::Default)
858     EPI.TypeQuals.addAddressSpace(AS);
859 
860   // C++1y [expr.prim.lambda]:
861   //   The lambda return type is 'auto', which is replaced by the
862   //   trailing-return type if provided and/or deduced from 'return'
863   //   statements
864   // We don't do this before C++1y, because we don't support deduced return
865   // types there.
866   QualType DefaultTypeForNoTrailingReturn = S.getLangOpts().CPlusPlus14
867                                                 ? S.Context.getAutoDeductType()
868                                                 : S.Context.DependentTy;
869   QualType MethodTy = S.Context.getFunctionType(DefaultTypeForNoTrailingReturn,
870                                                 std::nullopt, EPI);
871   return S.Context.getTrivialTypeSourceInfo(MethodTy, Loc);
872 }
873 
874 static TypeSourceInfo *getLambdaType(Sema &S, LambdaIntroducer &Intro,
875                                      Declarator &ParamInfo, Scope *CurScope,
876                                      SourceLocation Loc,
877                                      bool &ExplicitResultType) {
878 
879   ExplicitResultType = false;
880 
881   assert(
882       (ParamInfo.getDeclSpec().getStorageClassSpec() ==
883            DeclSpec::SCS_unspecified ||
884        ParamInfo.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_static) &&
885       "Unexpected storage specifier");
886   bool IsLambdaStatic =
887       ParamInfo.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_static;
888 
889   TypeSourceInfo *MethodTyInfo;
890 
891   if (ParamInfo.getNumTypeObjects() == 0) {
892     MethodTyInfo = getDummyLambdaType(S, Loc);
893   } else {
894     // Check explicit parameters
895     S.CheckExplicitObjectLambda(ParamInfo);
896 
897     DeclaratorChunk::FunctionTypeInfo &FTI = ParamInfo.getFunctionTypeInfo();
898 
899     bool HasExplicitObjectParameter =
900         ParamInfo.isExplicitObjectMemberFunction();
901 
902     ExplicitResultType = FTI.hasTrailingReturnType();
903     if (!FTI.hasMutableQualifier() && !IsLambdaStatic &&
904         !HasExplicitObjectParameter)
905       FTI.getOrCreateMethodQualifiers().SetTypeQual(DeclSpec::TQ_const, Loc);
906 
907     if (ExplicitResultType && S.getLangOpts().HLSL) {
908       QualType RetTy = FTI.getTrailingReturnType().get();
909       if (!RetTy.isNull()) {
910         // HLSL does not support specifying an address space on a lambda return
911         // type.
912         LangAS AddressSpace = RetTy.getAddressSpace();
913         if (AddressSpace != LangAS::Default)
914           S.Diag(FTI.getTrailingReturnTypeLoc(),
915                  diag::err_return_value_with_address_space);
916       }
917     }
918 
919     MethodTyInfo = S.GetTypeForDeclarator(ParamInfo);
920     assert(MethodTyInfo && "no type from lambda-declarator");
921 
922     // Check for unexpanded parameter packs in the method type.
923     if (MethodTyInfo->getType()->containsUnexpandedParameterPack())
924       S.DiagnoseUnexpandedParameterPack(Intro.Range.getBegin(), MethodTyInfo,
925                                         S.UPPC_DeclarationType);
926   }
927   return MethodTyInfo;
928 }
929 
930 CXXMethodDecl *Sema::CreateLambdaCallOperator(SourceRange IntroducerRange,
931                                               CXXRecordDecl *Class) {
932 
933   // C++20 [expr.prim.lambda.closure]p3:
934   // The closure type for a lambda-expression has a public inline function
935   // call operator (for a non-generic lambda) or function call operator
936   // template (for a generic lambda) whose parameters and return type are
937   // described by the lambda-expression's parameter-declaration-clause
938   // and trailing-return-type respectively.
939   DeclarationName MethodName =
940       Context.DeclarationNames.getCXXOperatorName(OO_Call);
941   DeclarationNameLoc MethodNameLoc =
942       DeclarationNameLoc::makeCXXOperatorNameLoc(IntroducerRange.getBegin());
943   CXXMethodDecl *Method = CXXMethodDecl::Create(
944       Context, Class, SourceLocation(),
945       DeclarationNameInfo(MethodName, IntroducerRange.getBegin(),
946                           MethodNameLoc),
947       QualType(), /*Tinfo=*/nullptr, SC_None,
948       getCurFPFeatures().isFPConstrained(),
949       /*isInline=*/true, ConstexprSpecKind::Unspecified, SourceLocation(),
950       /*TrailingRequiresClause=*/nullptr);
951   Method->setAccess(AS_public);
952   return Method;
953 }
954 
955 void Sema::AddTemplateParametersToLambdaCallOperator(
956     CXXMethodDecl *CallOperator, CXXRecordDecl *Class,
957     TemplateParameterList *TemplateParams) {
958   assert(TemplateParams && "no template parameters");
959   FunctionTemplateDecl *TemplateMethod = FunctionTemplateDecl::Create(
960       Context, Class, CallOperator->getLocation(), CallOperator->getDeclName(),
961       TemplateParams, CallOperator);
962   TemplateMethod->setAccess(AS_public);
963   CallOperator->setDescribedFunctionTemplate(TemplateMethod);
964 }
965 
966 void Sema::CompleteLambdaCallOperator(
967     CXXMethodDecl *Method, SourceLocation LambdaLoc,
968     SourceLocation CallOperatorLoc, Expr *TrailingRequiresClause,
969     TypeSourceInfo *MethodTyInfo, ConstexprSpecKind ConstexprKind,
970     StorageClass SC, ArrayRef<ParmVarDecl *> Params,
971     bool HasExplicitResultType) {
972 
973   LambdaScopeInfo *LSI = getCurrentLambdaScopeUnsafe(*this);
974 
975   if (TrailingRequiresClause)
976     Method->setTrailingRequiresClause(TrailingRequiresClause);
977 
978   TemplateParameterList *TemplateParams =
979       getGenericLambdaTemplateParameterList(LSI, *this);
980 
981   DeclContext *DC = Method->getLexicalDeclContext();
982   Method->setLexicalDeclContext(LSI->Lambda);
983   if (TemplateParams) {
984     FunctionTemplateDecl *TemplateMethod =
985         Method->getDescribedFunctionTemplate();
986     assert(TemplateMethod &&
987            "AddTemplateParametersToLambdaCallOperator should have been called");
988 
989     LSI->Lambda->addDecl(TemplateMethod);
990     TemplateMethod->setLexicalDeclContext(DC);
991   } else {
992     LSI->Lambda->addDecl(Method);
993   }
994   LSI->Lambda->setLambdaIsGeneric(TemplateParams);
995   LSI->Lambda->setLambdaTypeInfo(MethodTyInfo);
996 
997   Method->setLexicalDeclContext(DC);
998   Method->setLocation(LambdaLoc);
999   Method->setInnerLocStart(CallOperatorLoc);
1000   Method->setTypeSourceInfo(MethodTyInfo);
1001   Method->setType(buildTypeForLambdaCallOperator(*this, LSI->Lambda,
1002                                                  TemplateParams, MethodTyInfo));
1003   Method->setConstexprKind(ConstexprKind);
1004   Method->setStorageClass(SC);
1005   if (!Params.empty()) {
1006     CheckParmsForFunctionDef(Params, /*CheckParameterNames=*/false);
1007     Method->setParams(Params);
1008     for (auto P : Method->parameters()) {
1009       assert(P && "null in a parameter list");
1010       P->setOwningFunction(Method);
1011     }
1012   }
1013 
1014   buildLambdaScopeReturnType(*this, LSI, Method, HasExplicitResultType);
1015 }
1016 
1017 void Sema::ActOnLambdaExpressionAfterIntroducer(LambdaIntroducer &Intro,
1018                                                 Scope *CurrentScope) {
1019 
1020   LambdaScopeInfo *LSI = getCurLambda();
1021   assert(LSI && "LambdaScopeInfo should be on stack!");
1022 
1023   if (Intro.Default == LCD_ByCopy)
1024     LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByval;
1025   else if (Intro.Default == LCD_ByRef)
1026     LSI->ImpCaptureStyle = LambdaScopeInfo::ImpCap_LambdaByref;
1027   LSI->CaptureDefaultLoc = Intro.DefaultLoc;
1028   LSI->IntroducerRange = Intro.Range;
1029   LSI->AfterParameterList = false;
1030 
1031   assert(LSI->NumExplicitTemplateParams == 0);
1032 
1033   // Determine if we're within a context where we know that the lambda will
1034   // be dependent, because there are template parameters in scope.
1035   CXXRecordDecl::LambdaDependencyKind LambdaDependencyKind =
1036       CXXRecordDecl::LDK_Unknown;
1037   if (LSI->NumExplicitTemplateParams > 0) {
1038     Scope *TemplateParamScope = CurScope->getTemplateParamParent();
1039     assert(TemplateParamScope &&
1040            "Lambda with explicit template param list should establish a "
1041            "template param scope");
1042     assert(TemplateParamScope->getParent());
1043     if (TemplateParamScope->getParent()->getTemplateParamParent() != nullptr)
1044       LambdaDependencyKind = CXXRecordDecl::LDK_AlwaysDependent;
1045   } else if (CurScope->getTemplateParamParent() != nullptr) {
1046     LambdaDependencyKind = CXXRecordDecl::LDK_AlwaysDependent;
1047   }
1048 
1049   CXXRecordDecl *Class = createLambdaClosureType(
1050       Intro.Range, /*Info=*/nullptr, LambdaDependencyKind, Intro.Default);
1051   LSI->Lambda = Class;
1052 
1053   CXXMethodDecl *Method = CreateLambdaCallOperator(Intro.Range, Class);
1054   LSI->CallOperator = Method;
1055   Method->setLexicalDeclContext(CurContext);
1056 
1057   PushDeclContext(CurScope, Method);
1058 
1059   bool ContainsUnexpandedParameterPack = false;
1060 
1061   // Distinct capture names, for diagnostics.
1062   llvm::DenseMap<IdentifierInfo *, ValueDecl *> CaptureNames;
1063 
1064   // Handle explicit captures.
1065   SourceLocation PrevCaptureLoc =
1066       Intro.Default == LCD_None ? Intro.Range.getBegin() : Intro.DefaultLoc;
1067   for (auto C = Intro.Captures.begin(), E = Intro.Captures.end(); C != E;
1068        PrevCaptureLoc = C->Loc, ++C) {
1069     if (C->Kind == LCK_This || C->Kind == LCK_StarThis) {
1070       if (C->Kind == LCK_StarThis)
1071         Diag(C->Loc, !getLangOpts().CPlusPlus17
1072                          ? diag::ext_star_this_lambda_capture_cxx17
1073                          : diag::warn_cxx14_compat_star_this_lambda_capture);
1074 
1075       // C++11 [expr.prim.lambda]p8:
1076       //   An identifier or this shall not appear more than once in a
1077       //   lambda-capture.
1078       if (LSI->isCXXThisCaptured()) {
1079         Diag(C->Loc, diag::err_capture_more_than_once)
1080             << "'this'" << SourceRange(LSI->getCXXThisCapture().getLocation())
1081             << FixItHint::CreateRemoval(
1082                    SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1083         continue;
1084       }
1085 
1086       // C++20 [expr.prim.lambda]p8:
1087       //  If a lambda-capture includes a capture-default that is =,
1088       //  each simple-capture of that lambda-capture shall be of the form
1089       //  "&identifier", "this", or "* this". [ Note: The form [&,this] is
1090       //  redundant but accepted for compatibility with ISO C++14. --end note ]
1091       if (Intro.Default == LCD_ByCopy && C->Kind != LCK_StarThis)
1092         Diag(C->Loc, !getLangOpts().CPlusPlus20
1093                          ? diag::ext_equals_this_lambda_capture_cxx20
1094                          : diag::warn_cxx17_compat_equals_this_lambda_capture);
1095 
1096       // C++11 [expr.prim.lambda]p12:
1097       //   If this is captured by a local lambda expression, its nearest
1098       //   enclosing function shall be a non-static member function.
1099       QualType ThisCaptureType = getCurrentThisType();
1100       if (ThisCaptureType.isNull()) {
1101         Diag(C->Loc, diag::err_this_capture) << true;
1102         continue;
1103       }
1104 
1105       CheckCXXThisCapture(C->Loc, /*Explicit=*/true, /*BuildAndDiagnose*/ true,
1106                           /*FunctionScopeIndexToStopAtPtr*/ nullptr,
1107                           C->Kind == LCK_StarThis);
1108       if (!LSI->Captures.empty())
1109         LSI->ExplicitCaptureRanges[LSI->Captures.size() - 1] = C->ExplicitRange;
1110       continue;
1111     }
1112 
1113     assert(C->Id && "missing identifier for capture");
1114 
1115     if (C->Init.isInvalid())
1116       continue;
1117 
1118     ValueDecl *Var = nullptr;
1119     if (C->Init.isUsable()) {
1120       Diag(C->Loc, getLangOpts().CPlusPlus14
1121                        ? diag::warn_cxx11_compat_init_capture
1122                        : diag::ext_init_capture);
1123 
1124       // If the initializer expression is usable, but the InitCaptureType
1125       // is not, then an error has occurred - so ignore the capture for now.
1126       // for e.g., [n{0}] { }; <-- if no <initializer_list> is included.
1127       // FIXME: we should create the init capture variable and mark it invalid
1128       // in this case.
1129       if (C->InitCaptureType.get().isNull())
1130         continue;
1131 
1132       if (C->Init.get()->containsUnexpandedParameterPack() &&
1133           !C->InitCaptureType.get()->getAs<PackExpansionType>())
1134         DiagnoseUnexpandedParameterPack(C->Init.get(), UPPC_Initializer);
1135 
1136       unsigned InitStyle;
1137       switch (C->InitKind) {
1138       case LambdaCaptureInitKind::NoInit:
1139         llvm_unreachable("not an init-capture?");
1140       case LambdaCaptureInitKind::CopyInit:
1141         InitStyle = VarDecl::CInit;
1142         break;
1143       case LambdaCaptureInitKind::DirectInit:
1144         InitStyle = VarDecl::CallInit;
1145         break;
1146       case LambdaCaptureInitKind::ListInit:
1147         InitStyle = VarDecl::ListInit;
1148         break;
1149       }
1150       Var = createLambdaInitCaptureVarDecl(C->Loc, C->InitCaptureType.get(),
1151                                            C->EllipsisLoc, C->Id, InitStyle,
1152                                            C->Init.get(), Method);
1153       assert(Var && "createLambdaInitCaptureVarDecl returned a null VarDecl?");
1154       if (auto *V = dyn_cast<VarDecl>(Var))
1155         CheckShadow(CurrentScope, V);
1156       PushOnScopeChains(Var, CurrentScope, false);
1157     } else {
1158       assert(C->InitKind == LambdaCaptureInitKind::NoInit &&
1159              "init capture has valid but null init?");
1160 
1161       // C++11 [expr.prim.lambda]p8:
1162       //   If a lambda-capture includes a capture-default that is &, the
1163       //   identifiers in the lambda-capture shall not be preceded by &.
1164       //   If a lambda-capture includes a capture-default that is =, [...]
1165       //   each identifier it contains shall be preceded by &.
1166       if (C->Kind == LCK_ByRef && Intro.Default == LCD_ByRef) {
1167         Diag(C->Loc, diag::err_reference_capture_with_reference_default)
1168             << FixItHint::CreateRemoval(
1169                 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1170         continue;
1171       } else if (C->Kind == LCK_ByCopy && Intro.Default == LCD_ByCopy) {
1172         Diag(C->Loc, diag::err_copy_capture_with_copy_default)
1173             << FixItHint::CreateRemoval(
1174                 SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1175         continue;
1176       }
1177 
1178       // C++11 [expr.prim.lambda]p10:
1179       //   The identifiers in a capture-list are looked up using the usual
1180       //   rules for unqualified name lookup (3.4.1)
1181       DeclarationNameInfo Name(C->Id, C->Loc);
1182       LookupResult R(*this, Name, LookupOrdinaryName);
1183       LookupName(R, CurScope);
1184       if (R.isAmbiguous())
1185         continue;
1186       if (R.empty()) {
1187         // FIXME: Disable corrections that would add qualification?
1188         CXXScopeSpec ScopeSpec;
1189         DeclFilterCCC<VarDecl> Validator{};
1190         if (DiagnoseEmptyLookup(CurScope, ScopeSpec, R, Validator))
1191           continue;
1192       }
1193 
1194       if (auto *BD = R.getAsSingle<BindingDecl>())
1195         Var = BD;
1196       else
1197         Var = R.getAsSingle<VarDecl>();
1198       if (Var && DiagnoseUseOfDecl(Var, C->Loc))
1199         continue;
1200     }
1201 
1202     // C++11 [expr.prim.lambda]p10:
1203     //   [...] each such lookup shall find a variable with automatic storage
1204     //   duration declared in the reaching scope of the local lambda expression.
1205     // Note that the 'reaching scope' check happens in tryCaptureVariable().
1206     if (!Var) {
1207       Diag(C->Loc, diag::err_capture_does_not_name_variable) << C->Id;
1208       continue;
1209     }
1210 
1211     // C++11 [expr.prim.lambda]p8:
1212     //   An identifier or this shall not appear more than once in a
1213     //   lambda-capture.
1214     if (auto [It, Inserted] = CaptureNames.insert(std::pair{C->Id, Var});
1215         !Inserted) {
1216       if (C->InitKind == LambdaCaptureInitKind::NoInit &&
1217           !Var->isInitCapture()) {
1218         Diag(C->Loc, diag::err_capture_more_than_once)
1219             << C->Id << It->second->getBeginLoc()
1220             << FixItHint::CreateRemoval(
1221                    SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
1222         Var->setInvalidDecl();
1223       } else if (Var && Var->isPlaceholderVar(getLangOpts())) {
1224         DiagPlaceholderVariableDefinition(C->Loc);
1225       } else {
1226         // Previous capture captured something different (one or both was
1227         // an init-capture): no fixit.
1228         Diag(C->Loc, diag::err_capture_more_than_once) << C->Id;
1229         continue;
1230       }
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       PushOnScopeChains(Var, CurScope, false);
1265     } else {
1266       TryCaptureKind Kind = C->Kind == LCK_ByRef ? TryCapture_ExplicitByRef
1267                                                  : TryCapture_ExplicitByVal;
1268       tryCaptureVariable(Var, C->Loc, Kind, EllipsisLoc);
1269     }
1270     if (!LSI->Captures.empty())
1271       LSI->ExplicitCaptureRanges[LSI->Captures.size() - 1] = C->ExplicitRange;
1272   }
1273   finishLambdaExplicitCaptures(LSI);
1274   LSI->ContainsUnexpandedParameterPack |= ContainsUnexpandedParameterPack;
1275   PopDeclContext();
1276 }
1277 
1278 void Sema::ActOnLambdaClosureQualifiers(LambdaIntroducer &Intro,
1279                                         SourceLocation MutableLoc) {
1280 
1281   LambdaScopeInfo *LSI = getCurrentLambdaScopeUnsafe(*this);
1282   LSI->Mutable = MutableLoc.isValid();
1283   ContextRAII Context(*this, LSI->CallOperator, /*NewThisContext*/ false);
1284 
1285   // C++11 [expr.prim.lambda]p9:
1286   //   A lambda-expression whose smallest enclosing scope is a block scope is a
1287   //   local lambda expression; any other lambda expression shall not have a
1288   //   capture-default or simple-capture in its lambda-introducer.
1289   //
1290   // For simple-captures, this is covered by the check below that any named
1291   // entity is a variable that can be captured.
1292   //
1293   // For DR1632, we also allow a capture-default in any context where we can
1294   // odr-use 'this' (in particular, in a default initializer for a non-static
1295   // data member).
1296   if (Intro.Default != LCD_None &&
1297       !LSI->Lambda->getParent()->isFunctionOrMethod() &&
1298       (getCurrentThisType().isNull() ||
1299        CheckCXXThisCapture(SourceLocation(), /*Explicit=*/true,
1300                            /*BuildAndDiagnose=*/false)))
1301     Diag(Intro.DefaultLoc, diag::err_capture_default_non_local);
1302 }
1303 
1304 void Sema::ActOnLambdaClosureParameters(
1305     Scope *LambdaScope, MutableArrayRef<DeclaratorChunk::ParamInfo> Params) {
1306   LambdaScopeInfo *LSI = getCurrentLambdaScopeUnsafe(*this);
1307   PushDeclContext(LambdaScope, LSI->CallOperator);
1308 
1309   for (const DeclaratorChunk::ParamInfo &P : Params) {
1310     auto *Param = cast<ParmVarDecl>(P.Param);
1311     Param->setOwningFunction(LSI->CallOperator);
1312     if (Param->getIdentifier())
1313       PushOnScopeChains(Param, LambdaScope, false);
1314   }
1315 
1316   // After the parameter list, we may parse a noexcept/requires/trailing return
1317   // type which need to know whether the call operator constiture a dependent
1318   // context, so we need to setup the FunctionTemplateDecl of generic lambdas
1319   // now.
1320   TemplateParameterList *TemplateParams =
1321       getGenericLambdaTemplateParameterList(LSI, *this);
1322   if (TemplateParams) {
1323     AddTemplateParametersToLambdaCallOperator(LSI->CallOperator, LSI->Lambda,
1324                                               TemplateParams);
1325     LSI->Lambda->setLambdaIsGeneric(true);
1326   }
1327   LSI->AfterParameterList = true;
1328 }
1329 
1330 void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
1331                                         Declarator &ParamInfo,
1332                                         const DeclSpec &DS) {
1333 
1334   LambdaScopeInfo *LSI = getCurrentLambdaScopeUnsafe(*this);
1335   LSI->CallOperator->setConstexprKind(DS.getConstexprSpecifier());
1336 
1337   SmallVector<ParmVarDecl *, 8> Params;
1338   bool ExplicitResultType;
1339 
1340   SourceLocation TypeLoc, CallOperatorLoc;
1341   if (ParamInfo.getNumTypeObjects() == 0) {
1342     CallOperatorLoc = TypeLoc = Intro.Range.getEnd();
1343   } else {
1344     unsigned Index;
1345     ParamInfo.isFunctionDeclarator(Index);
1346     const auto &Object = ParamInfo.getTypeObject(Index);
1347     TypeLoc =
1348         Object.Loc.isValid() ? Object.Loc : ParamInfo.getSourceRange().getEnd();
1349     CallOperatorLoc = ParamInfo.getSourceRange().getEnd();
1350   }
1351 
1352   CXXRecordDecl *Class = LSI->Lambda;
1353   CXXMethodDecl *Method = LSI->CallOperator;
1354 
1355   TypeSourceInfo *MethodTyInfo = getLambdaType(
1356       *this, Intro, ParamInfo, getCurScope(), TypeLoc, ExplicitResultType);
1357 
1358   LSI->ExplicitParams = ParamInfo.getNumTypeObjects() != 0;
1359 
1360   if (ParamInfo.isFunctionDeclarator() != 0 &&
1361       !FTIHasSingleVoidParameter(ParamInfo.getFunctionTypeInfo())) {
1362     const auto &FTI = ParamInfo.getFunctionTypeInfo();
1363     Params.reserve(Params.size());
1364     for (unsigned I = 0; I < FTI.NumParams; ++I) {
1365       auto *Param = cast<ParmVarDecl>(FTI.Params[I].Param);
1366       Param->setScopeInfo(0, Params.size());
1367       Params.push_back(Param);
1368     }
1369   }
1370 
1371   bool IsLambdaStatic =
1372       ParamInfo.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_static;
1373 
1374   CompleteLambdaCallOperator(
1375       Method, Intro.Range.getBegin(), CallOperatorLoc,
1376       ParamInfo.getTrailingRequiresClause(), MethodTyInfo,
1377       ParamInfo.getDeclSpec().getConstexprSpecifier(),
1378       IsLambdaStatic ? SC_Static : SC_None, Params, ExplicitResultType);
1379 
1380   CheckCXXDefaultArguments(Method);
1381 
1382   // This represents the function body for the lambda function, check if we
1383   // have to apply optnone due to a pragma.
1384   AddRangeBasedOptnone(Method);
1385 
1386   // code_seg attribute on lambda apply to the method.
1387   if (Attr *A = getImplicitCodeSegOrSectionAttrForFunction(
1388           Method, /*IsDefinition=*/true))
1389     Method->addAttr(A);
1390 
1391   // Attributes on the lambda apply to the method.
1392   ProcessDeclAttributes(CurScope, Method, ParamInfo);
1393 
1394   // CUDA lambdas get implicit host and device attributes.
1395   if (getLangOpts().CUDA)
1396     CUDASetLambdaAttrs(Method);
1397 
1398   // OpenMP lambdas might get assumumption attributes.
1399   if (LangOpts.OpenMP)
1400     ActOnFinishedFunctionDefinitionInOpenMPAssumeScope(Method);
1401 
1402   handleLambdaNumbering(Class, Method);
1403 
1404   for (auto &&C : LSI->Captures) {
1405     if (!C.isVariableCapture())
1406       continue;
1407     ValueDecl *Var = C.getVariable();
1408     if (Var && Var->isInitCapture()) {
1409       PushOnScopeChains(Var, CurScope, false);
1410     }
1411   }
1412 
1413   auto CheckRedefinition = [&](ParmVarDecl *Param) {
1414     for (const auto &Capture : Intro.Captures) {
1415       if (Capture.Id == Param->getIdentifier()) {
1416         Diag(Param->getLocation(), diag::err_parameter_shadow_capture);
1417         Diag(Capture.Loc, diag::note_var_explicitly_captured_here)
1418             << Capture.Id << true;
1419         return false;
1420       }
1421     }
1422     return true;
1423   };
1424 
1425   for (ParmVarDecl *P : Params) {
1426     if (!P->getIdentifier())
1427       continue;
1428     if (CheckRedefinition(P))
1429       CheckShadow(CurScope, P);
1430     PushOnScopeChains(P, CurScope);
1431   }
1432 
1433   // C++23 [expr.prim.lambda.capture]p5:
1434   // If an identifier in a capture appears as the declarator-id of a parameter
1435   // of the lambda-declarator's parameter-declaration-clause or as the name of a
1436   // template parameter of the lambda-expression's template-parameter-list, the
1437   // program is ill-formed.
1438   TemplateParameterList *TemplateParams =
1439       getGenericLambdaTemplateParameterList(LSI, *this);
1440   if (TemplateParams) {
1441     for (const auto *TP : TemplateParams->asArray()) {
1442       if (!TP->getIdentifier())
1443         continue;
1444       for (const auto &Capture : Intro.Captures) {
1445         if (Capture.Id == TP->getIdentifier()) {
1446           Diag(Capture.Loc, diag::err_template_param_shadow) << Capture.Id;
1447           NoteTemplateParameterLocation(*TP);
1448         }
1449       }
1450     }
1451   }
1452 
1453   // C++20: dcl.decl.general p4:
1454   // The optional requires-clause ([temp.pre]) in an init-declarator or
1455   // member-declarator shall be present only if the declarator declares a
1456   // templated function ([dcl.fct]).
1457   if (Expr *TRC = Method->getTrailingRequiresClause()) {
1458     // [temp.pre]/8:
1459     // An entity is templated if it is
1460     // - a template,
1461     // - an entity defined ([basic.def]) or created ([class.temporary]) in a
1462     // templated entity,
1463     // - a member of a templated entity,
1464     // - an enumerator for an enumeration that is a templated entity, or
1465     // - the closure type of a lambda-expression ([expr.prim.lambda.closure])
1466     // appearing in the declaration of a templated entity. [Note 6: A local
1467     // class, a local or block variable, or a friend function defined in a
1468     // templated entity is a templated entity.  — end note]
1469     //
1470     // A templated function is a function template or a function that is
1471     // templated. A templated class is a class template or a class that is
1472     // templated. A templated variable is a variable template or a variable
1473     // that is templated.
1474 
1475     // Note: we only have to check if this is defined in a template entity, OR
1476     // if we are a template, since the rest don't apply. The requires clause
1477     // applies to the call operator, which we already know is a member function,
1478     // AND defined.
1479     if (!Method->getDescribedFunctionTemplate() && !Method->isTemplated()) {
1480       Diag(TRC->getBeginLoc(), diag::err_constrained_non_templated_function);
1481     }
1482   }
1483 
1484   // Enter a new evaluation context to insulate the lambda from any
1485   // cleanups from the enclosing full-expression.
1486   PushExpressionEvaluationContext(
1487       LSI->CallOperator->isConsteval()
1488           ? ExpressionEvaluationContext::ImmediateFunctionContext
1489           : ExpressionEvaluationContext::PotentiallyEvaluated);
1490   ExprEvalContexts.back().InImmediateFunctionContext =
1491       LSI->CallOperator->isConsteval();
1492   ExprEvalContexts.back().InImmediateEscalatingFunctionContext =
1493       getLangOpts().CPlusPlus20 && LSI->CallOperator->isImmediateEscalating();
1494 }
1495 
1496 void Sema::ActOnLambdaError(SourceLocation StartLoc, Scope *CurScope,
1497                             bool IsInstantiation) {
1498   LambdaScopeInfo *LSI = cast<LambdaScopeInfo>(FunctionScopes.back());
1499 
1500   // Leave the expression-evaluation context.
1501   DiscardCleanupsInEvaluationContext();
1502   PopExpressionEvaluationContext();
1503 
1504   // Leave the context of the lambda.
1505   if (!IsInstantiation)
1506     PopDeclContext();
1507 
1508   // Finalize the lambda.
1509   CXXRecordDecl *Class = LSI->Lambda;
1510   Class->setInvalidDecl();
1511   SmallVector<Decl*, 4> Fields(Class->fields());
1512   ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
1513               SourceLocation(), ParsedAttributesView());
1514   CheckCompletedCXXClass(nullptr, Class);
1515 
1516   PopFunctionScopeInfo();
1517 }
1518 
1519 template <typename Func>
1520 static void repeatForLambdaConversionFunctionCallingConvs(
1521     Sema &S, const FunctionProtoType &CallOpProto, Func F) {
1522   CallingConv DefaultFree = S.Context.getDefaultCallingConvention(
1523       CallOpProto.isVariadic(), /*IsCXXMethod=*/false);
1524   CallingConv DefaultMember = S.Context.getDefaultCallingConvention(
1525       CallOpProto.isVariadic(), /*IsCXXMethod=*/true);
1526   CallingConv CallOpCC = CallOpProto.getCallConv();
1527 
1528   /// Implement emitting a version of the operator for many of the calling
1529   /// conventions for MSVC, as described here:
1530   /// https://devblogs.microsoft.com/oldnewthing/20150220-00/?p=44623.
1531   /// Experimentally, we determined that cdecl, stdcall, fastcall, and
1532   /// vectorcall are generated by MSVC when it is supported by the target.
1533   /// Additionally, we are ensuring that the default-free/default-member and
1534   /// call-operator calling convention are generated as well.
1535   /// NOTE: We intentionally generate a 'thiscall' on Win32 implicitly from the
1536   /// 'member default', despite MSVC not doing so. We do this in order to ensure
1537   /// that someone who intentionally places 'thiscall' on the lambda call
1538   /// operator will still get that overload, since we don't have the a way of
1539   /// detecting the attribute by the time we get here.
1540   if (S.getLangOpts().MSVCCompat) {
1541     CallingConv Convs[] = {
1542         CC_C,        CC_X86StdCall, CC_X86FastCall, CC_X86VectorCall,
1543         DefaultFree, DefaultMember, CallOpCC};
1544     llvm::sort(Convs);
1545     llvm::iterator_range<CallingConv *> Range(
1546         std::begin(Convs), std::unique(std::begin(Convs), std::end(Convs)));
1547     const TargetInfo &TI = S.getASTContext().getTargetInfo();
1548 
1549     for (CallingConv C : Range) {
1550       if (TI.checkCallingConvention(C) == TargetInfo::CCCR_OK)
1551         F(C);
1552     }
1553     return;
1554   }
1555 
1556   if (CallOpCC == DefaultMember && DefaultMember != DefaultFree) {
1557     F(DefaultFree);
1558     F(DefaultMember);
1559   } else {
1560     F(CallOpCC);
1561   }
1562 }
1563 
1564 // Returns the 'standard' calling convention to be used for the lambda
1565 // conversion function, that is, the 'free' function calling convention unless
1566 // it is overridden by a non-default calling convention attribute.
1567 static CallingConv
1568 getLambdaConversionFunctionCallConv(Sema &S,
1569                                     const FunctionProtoType *CallOpProto) {
1570   CallingConv DefaultFree = S.Context.getDefaultCallingConvention(
1571       CallOpProto->isVariadic(), /*IsCXXMethod=*/false);
1572   CallingConv DefaultMember = S.Context.getDefaultCallingConvention(
1573       CallOpProto->isVariadic(), /*IsCXXMethod=*/true);
1574   CallingConv CallOpCC = CallOpProto->getCallConv();
1575 
1576   // If the call-operator hasn't been changed, return both the 'free' and
1577   // 'member' function calling convention.
1578   if (CallOpCC == DefaultMember && DefaultMember != DefaultFree)
1579     return DefaultFree;
1580   return CallOpCC;
1581 }
1582 
1583 QualType Sema::getLambdaConversionFunctionResultType(
1584     const FunctionProtoType *CallOpProto, CallingConv CC) {
1585   const FunctionProtoType::ExtProtoInfo CallOpExtInfo =
1586       CallOpProto->getExtProtoInfo();
1587   FunctionProtoType::ExtProtoInfo InvokerExtInfo = CallOpExtInfo;
1588   InvokerExtInfo.ExtInfo = InvokerExtInfo.ExtInfo.withCallingConv(CC);
1589   InvokerExtInfo.TypeQuals = Qualifiers();
1590   assert(InvokerExtInfo.RefQualifier == RQ_None &&
1591          "Lambda's call operator should not have a reference qualifier");
1592   return Context.getFunctionType(CallOpProto->getReturnType(),
1593                                  CallOpProto->getParamTypes(), InvokerExtInfo);
1594 }
1595 
1596 /// Add a lambda's conversion to function pointer, as described in
1597 /// C++11 [expr.prim.lambda]p6.
1598 static void addFunctionPointerConversion(Sema &S, SourceRange IntroducerRange,
1599                                          CXXRecordDecl *Class,
1600                                          CXXMethodDecl *CallOperator,
1601                                          QualType InvokerFunctionTy) {
1602   // This conversion is explicitly disabled if the lambda's function has
1603   // pass_object_size attributes on any of its parameters.
1604   auto HasPassObjectSizeAttr = [](const ParmVarDecl *P) {
1605     return P->hasAttr<PassObjectSizeAttr>();
1606   };
1607   if (llvm::any_of(CallOperator->parameters(), HasPassObjectSizeAttr))
1608     return;
1609 
1610   // Add the conversion to function pointer.
1611   QualType PtrToFunctionTy = S.Context.getPointerType(InvokerFunctionTy);
1612 
1613   // Create the type of the conversion function.
1614   FunctionProtoType::ExtProtoInfo ConvExtInfo(
1615       S.Context.getDefaultCallingConvention(
1616       /*IsVariadic=*/false, /*IsCXXMethod=*/true));
1617   // The conversion function is always const and noexcept.
1618   ConvExtInfo.TypeQuals = Qualifiers();
1619   ConvExtInfo.TypeQuals.addConst();
1620   ConvExtInfo.ExceptionSpec.Type = EST_BasicNoexcept;
1621   QualType ConvTy =
1622       S.Context.getFunctionType(PtrToFunctionTy, std::nullopt, ConvExtInfo);
1623 
1624   SourceLocation Loc = IntroducerRange.getBegin();
1625   DeclarationName ConversionName
1626     = S.Context.DeclarationNames.getCXXConversionFunctionName(
1627         S.Context.getCanonicalType(PtrToFunctionTy));
1628   // Construct a TypeSourceInfo for the conversion function, and wire
1629   // all the parameters appropriately for the FunctionProtoTypeLoc
1630   // so that everything works during transformation/instantiation of
1631   // generic lambdas.
1632   // The main reason for wiring up the parameters of the conversion
1633   // function with that of the call operator is so that constructs
1634   // like the following work:
1635   // auto L = [](auto b) {                <-- 1
1636   //   return [](auto a) -> decltype(a) { <-- 2
1637   //      return a;
1638   //   };
1639   // };
1640   // int (*fp)(int) = L(5);
1641   // Because the trailing return type can contain DeclRefExprs that refer
1642   // to the original call operator's variables, we hijack the call
1643   // operators ParmVarDecls below.
1644   TypeSourceInfo *ConvNamePtrToFunctionTSI =
1645       S.Context.getTrivialTypeSourceInfo(PtrToFunctionTy, Loc);
1646   DeclarationNameLoc ConvNameLoc =
1647       DeclarationNameLoc::makeNamedTypeLoc(ConvNamePtrToFunctionTSI);
1648 
1649   // The conversion function is a conversion to a pointer-to-function.
1650   TypeSourceInfo *ConvTSI = S.Context.getTrivialTypeSourceInfo(ConvTy, Loc);
1651   FunctionProtoTypeLoc ConvTL =
1652       ConvTSI->getTypeLoc().getAs<FunctionProtoTypeLoc>();
1653   // Get the result of the conversion function which is a pointer-to-function.
1654   PointerTypeLoc PtrToFunctionTL =
1655       ConvTL.getReturnLoc().getAs<PointerTypeLoc>();
1656   // Do the same for the TypeSourceInfo that is used to name the conversion
1657   // operator.
1658   PointerTypeLoc ConvNamePtrToFunctionTL =
1659       ConvNamePtrToFunctionTSI->getTypeLoc().getAs<PointerTypeLoc>();
1660 
1661   // Get the underlying function types that the conversion function will
1662   // be converting to (should match the type of the call operator).
1663   FunctionProtoTypeLoc CallOpConvTL =
1664       PtrToFunctionTL.getPointeeLoc().getAs<FunctionProtoTypeLoc>();
1665   FunctionProtoTypeLoc CallOpConvNameTL =
1666     ConvNamePtrToFunctionTL.getPointeeLoc().getAs<FunctionProtoTypeLoc>();
1667 
1668   // Wire up the FunctionProtoTypeLocs with the call operator's parameters.
1669   // These parameter's are essentially used to transform the name and
1670   // the type of the conversion operator.  By using the same parameters
1671   // as the call operator's we don't have to fix any back references that
1672   // the trailing return type of the call operator's uses (such as
1673   // decltype(some_type<decltype(a)>::type{} + decltype(a){}) etc.)
1674   // - we can simply use the return type of the call operator, and
1675   // everything should work.
1676   SmallVector<ParmVarDecl *, 4> InvokerParams;
1677   for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I) {
1678     ParmVarDecl *From = CallOperator->getParamDecl(I);
1679 
1680     InvokerParams.push_back(ParmVarDecl::Create(
1681         S.Context,
1682         // Temporarily add to the TU. This is set to the invoker below.
1683         S.Context.getTranslationUnitDecl(), From->getBeginLoc(),
1684         From->getLocation(), From->getIdentifier(), From->getType(),
1685         From->getTypeSourceInfo(), From->getStorageClass(),
1686         /*DefArg=*/nullptr));
1687     CallOpConvTL.setParam(I, From);
1688     CallOpConvNameTL.setParam(I, From);
1689   }
1690 
1691   CXXConversionDecl *Conversion = CXXConversionDecl::Create(
1692       S.Context, Class, Loc,
1693       DeclarationNameInfo(ConversionName, Loc, ConvNameLoc), ConvTy, ConvTSI,
1694       S.getCurFPFeatures().isFPConstrained(),
1695       /*isInline=*/true, ExplicitSpecifier(),
1696       S.getLangOpts().CPlusPlus17 ? ConstexprSpecKind::Constexpr
1697                                   : ConstexprSpecKind::Unspecified,
1698       CallOperator->getBody()->getEndLoc());
1699   Conversion->setAccess(AS_public);
1700   Conversion->setImplicit(true);
1701 
1702   // A non-generic lambda may still be a templated entity. We need to preserve
1703   // constraints when converting the lambda to a function pointer. See GH63181.
1704   if (Expr *Requires = CallOperator->getTrailingRequiresClause())
1705     Conversion->setTrailingRequiresClause(Requires);
1706 
1707   if (Class->isGenericLambda()) {
1708     // Create a template version of the conversion operator, using the template
1709     // parameter list of the function call operator.
1710     FunctionTemplateDecl *TemplateCallOperator =
1711             CallOperator->getDescribedFunctionTemplate();
1712     FunctionTemplateDecl *ConversionTemplate =
1713                   FunctionTemplateDecl::Create(S.Context, Class,
1714                                       Loc, ConversionName,
1715                                       TemplateCallOperator->getTemplateParameters(),
1716                                       Conversion);
1717     ConversionTemplate->setAccess(AS_public);
1718     ConversionTemplate->setImplicit(true);
1719     Conversion->setDescribedFunctionTemplate(ConversionTemplate);
1720     Class->addDecl(ConversionTemplate);
1721   } else
1722     Class->addDecl(Conversion);
1723 
1724   // If the lambda is not static, we need to add a static member
1725   // function that will be the result of the conversion with a
1726   // certain unique ID.
1727   // When it is static we just return the static call operator instead.
1728   if (CallOperator->isImplicitObjectMemberFunction()) {
1729     DeclarationName InvokerName =
1730         &S.Context.Idents.get(getLambdaStaticInvokerName());
1731     // FIXME: Instead of passing in the CallOperator->getTypeSourceInfo()
1732     // we should get a prebuilt TrivialTypeSourceInfo from Context
1733     // using FunctionTy & Loc and get its TypeLoc as a FunctionProtoTypeLoc
1734     // then rewire the parameters accordingly, by hoisting up the InvokeParams
1735     // loop below and then use its Params to set Invoke->setParams(...) below.
1736     // This would avoid the 'const' qualifier of the calloperator from
1737     // contaminating the type of the invoker, which is currently adjusted
1738     // in SemaTemplateDeduction.cpp:DeduceTemplateArguments.  Fixing the
1739     // trailing return type of the invoker would require a visitor to rebuild
1740     // the trailing return type and adjusting all back DeclRefExpr's to refer
1741     // to the new static invoker parameters - not the call operator's.
1742     CXXMethodDecl *Invoke = CXXMethodDecl::Create(
1743         S.Context, Class, Loc, DeclarationNameInfo(InvokerName, Loc),
1744         InvokerFunctionTy, CallOperator->getTypeSourceInfo(), SC_Static,
1745         S.getCurFPFeatures().isFPConstrained(),
1746         /*isInline=*/true, CallOperator->getConstexprKind(),
1747         CallOperator->getBody()->getEndLoc());
1748     for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I)
1749       InvokerParams[I]->setOwningFunction(Invoke);
1750     Invoke->setParams(InvokerParams);
1751     Invoke->setAccess(AS_private);
1752     Invoke->setImplicit(true);
1753     if (Class->isGenericLambda()) {
1754       FunctionTemplateDecl *TemplateCallOperator =
1755           CallOperator->getDescribedFunctionTemplate();
1756       FunctionTemplateDecl *StaticInvokerTemplate =
1757           FunctionTemplateDecl::Create(
1758               S.Context, Class, Loc, InvokerName,
1759               TemplateCallOperator->getTemplateParameters(), Invoke);
1760       StaticInvokerTemplate->setAccess(AS_private);
1761       StaticInvokerTemplate->setImplicit(true);
1762       Invoke->setDescribedFunctionTemplate(StaticInvokerTemplate);
1763       Class->addDecl(StaticInvokerTemplate);
1764     } else
1765       Class->addDecl(Invoke);
1766   }
1767 }
1768 
1769 /// Add a lambda's conversion to function pointers, as described in
1770 /// C++11 [expr.prim.lambda]p6. Note that in most cases, this should emit only a
1771 /// single pointer conversion. In the event that the default calling convention
1772 /// for free and member functions is different, it will emit both conventions.
1773 static void addFunctionPointerConversions(Sema &S, SourceRange IntroducerRange,
1774                                           CXXRecordDecl *Class,
1775                                           CXXMethodDecl *CallOperator) {
1776   const FunctionProtoType *CallOpProto =
1777       CallOperator->getType()->castAs<FunctionProtoType>();
1778 
1779   repeatForLambdaConversionFunctionCallingConvs(
1780       S, *CallOpProto, [&](CallingConv CC) {
1781         QualType InvokerFunctionTy =
1782             S.getLambdaConversionFunctionResultType(CallOpProto, CC);
1783         addFunctionPointerConversion(S, IntroducerRange, Class, CallOperator,
1784                                      InvokerFunctionTy);
1785       });
1786 }
1787 
1788 /// Add a lambda's conversion to block pointer.
1789 static void addBlockPointerConversion(Sema &S,
1790                                       SourceRange IntroducerRange,
1791                                       CXXRecordDecl *Class,
1792                                       CXXMethodDecl *CallOperator) {
1793   const FunctionProtoType *CallOpProto =
1794       CallOperator->getType()->castAs<FunctionProtoType>();
1795   QualType FunctionTy = S.getLambdaConversionFunctionResultType(
1796       CallOpProto, getLambdaConversionFunctionCallConv(S, CallOpProto));
1797   QualType BlockPtrTy = S.Context.getBlockPointerType(FunctionTy);
1798 
1799   FunctionProtoType::ExtProtoInfo ConversionEPI(
1800       S.Context.getDefaultCallingConvention(
1801           /*IsVariadic=*/false, /*IsCXXMethod=*/true));
1802   ConversionEPI.TypeQuals = Qualifiers();
1803   ConversionEPI.TypeQuals.addConst();
1804   QualType ConvTy =
1805       S.Context.getFunctionType(BlockPtrTy, std::nullopt, ConversionEPI);
1806 
1807   SourceLocation Loc = IntroducerRange.getBegin();
1808   DeclarationName Name
1809     = S.Context.DeclarationNames.getCXXConversionFunctionName(
1810         S.Context.getCanonicalType(BlockPtrTy));
1811   DeclarationNameLoc NameLoc = DeclarationNameLoc::makeNamedTypeLoc(
1812       S.Context.getTrivialTypeSourceInfo(BlockPtrTy, Loc));
1813   CXXConversionDecl *Conversion = CXXConversionDecl::Create(
1814       S.Context, Class, Loc, DeclarationNameInfo(Name, Loc, NameLoc), ConvTy,
1815       S.Context.getTrivialTypeSourceInfo(ConvTy, Loc),
1816       S.getCurFPFeatures().isFPConstrained(),
1817       /*isInline=*/true, ExplicitSpecifier(), ConstexprSpecKind::Unspecified,
1818       CallOperator->getBody()->getEndLoc());
1819   Conversion->setAccess(AS_public);
1820   Conversion->setImplicit(true);
1821   Class->addDecl(Conversion);
1822 }
1823 
1824 ExprResult Sema::BuildCaptureInit(const Capture &Cap,
1825                                   SourceLocation ImplicitCaptureLoc,
1826                                   bool IsOpenMPMapping) {
1827   // VLA captures don't have a stored initialization expression.
1828   if (Cap.isVLATypeCapture())
1829     return ExprResult();
1830 
1831   // An init-capture is initialized directly from its stored initializer.
1832   if (Cap.isInitCapture())
1833     return cast<VarDecl>(Cap.getVariable())->getInit();
1834 
1835   // For anything else, build an initialization expression. For an implicit
1836   // capture, the capture notionally happens at the capture-default, so use
1837   // that location here.
1838   SourceLocation Loc =
1839       ImplicitCaptureLoc.isValid() ? ImplicitCaptureLoc : Cap.getLocation();
1840 
1841   // C++11 [expr.prim.lambda]p21:
1842   //   When the lambda-expression is evaluated, the entities that
1843   //   are captured by copy are used to direct-initialize each
1844   //   corresponding non-static data member of the resulting closure
1845   //   object. (For array members, the array elements are
1846   //   direct-initialized in increasing subscript order.) These
1847   //   initializations are performed in the (unspecified) order in
1848   //   which the non-static data members are declared.
1849 
1850   // C++ [expr.prim.lambda]p12:
1851   //   An entity captured by a lambda-expression is odr-used (3.2) in
1852   //   the scope containing the lambda-expression.
1853   ExprResult Init;
1854   IdentifierInfo *Name = nullptr;
1855   if (Cap.isThisCapture()) {
1856     QualType ThisTy = getCurrentThisType();
1857     Expr *This = BuildCXXThisExpr(Loc, ThisTy, ImplicitCaptureLoc.isValid());
1858     if (Cap.isCopyCapture())
1859       Init = CreateBuiltinUnaryOp(Loc, UO_Deref, This);
1860     else
1861       Init = This;
1862   } else {
1863     assert(Cap.isVariableCapture() && "unknown kind of capture");
1864     ValueDecl *Var = Cap.getVariable();
1865     Name = Var->getIdentifier();
1866     Init = BuildDeclarationNameExpr(
1867       CXXScopeSpec(), DeclarationNameInfo(Var->getDeclName(), Loc), Var);
1868   }
1869 
1870   // In OpenMP, the capture kind doesn't actually describe how to capture:
1871   // variables are "mapped" onto the device in a process that does not formally
1872   // make a copy, even for a "copy capture".
1873   if (IsOpenMPMapping)
1874     return Init;
1875 
1876   if (Init.isInvalid())
1877     return ExprError();
1878 
1879   Expr *InitExpr = Init.get();
1880   InitializedEntity Entity = InitializedEntity::InitializeLambdaCapture(
1881       Name, Cap.getCaptureType(), Loc);
1882   InitializationKind InitKind =
1883       InitializationKind::CreateDirect(Loc, Loc, Loc);
1884   InitializationSequence InitSeq(*this, Entity, InitKind, InitExpr);
1885   return InitSeq.Perform(*this, Entity, InitKind, InitExpr);
1886 }
1887 
1888 ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body) {
1889   LambdaScopeInfo LSI = *cast<LambdaScopeInfo>(FunctionScopes.back());
1890   ActOnFinishFunctionBody(LSI.CallOperator, Body);
1891   return BuildLambdaExpr(StartLoc, Body->getEndLoc(), &LSI);
1892 }
1893 
1894 static LambdaCaptureDefault
1895 mapImplicitCaptureStyle(CapturingScopeInfo::ImplicitCaptureStyle ICS) {
1896   switch (ICS) {
1897   case CapturingScopeInfo::ImpCap_None:
1898     return LCD_None;
1899   case CapturingScopeInfo::ImpCap_LambdaByval:
1900     return LCD_ByCopy;
1901   case CapturingScopeInfo::ImpCap_CapturedRegion:
1902   case CapturingScopeInfo::ImpCap_LambdaByref:
1903     return LCD_ByRef;
1904   case CapturingScopeInfo::ImpCap_Block:
1905     llvm_unreachable("block capture in lambda");
1906   }
1907   llvm_unreachable("Unknown implicit capture style");
1908 }
1909 
1910 bool Sema::CaptureHasSideEffects(const Capture &From) {
1911   if (From.isInitCapture()) {
1912     Expr *Init = cast<VarDecl>(From.getVariable())->getInit();
1913     if (Init && Init->HasSideEffects(Context))
1914       return true;
1915   }
1916 
1917   if (!From.isCopyCapture())
1918     return false;
1919 
1920   const QualType T = From.isThisCapture()
1921                          ? getCurrentThisType()->getPointeeType()
1922                          : From.getCaptureType();
1923 
1924   if (T.isVolatileQualified())
1925     return true;
1926 
1927   const Type *BaseT = T->getBaseElementTypeUnsafe();
1928   if (const CXXRecordDecl *RD = BaseT->getAsCXXRecordDecl())
1929     return !RD->isCompleteDefinition() || !RD->hasTrivialCopyConstructor() ||
1930            !RD->hasTrivialDestructor();
1931 
1932   return false;
1933 }
1934 
1935 bool Sema::DiagnoseUnusedLambdaCapture(SourceRange CaptureRange,
1936                                        const Capture &From) {
1937   if (CaptureHasSideEffects(From))
1938     return false;
1939 
1940   if (From.isVLATypeCapture())
1941     return false;
1942 
1943   // FIXME: maybe we should warn on these if we can find a sensible diagnostic
1944   // message
1945   if (From.isInitCapture() &&
1946       From.getVariable()->isPlaceholderVar(getLangOpts()))
1947     return false;
1948 
1949   auto diag = Diag(From.getLocation(), diag::warn_unused_lambda_capture);
1950   if (From.isThisCapture())
1951     diag << "'this'";
1952   else
1953     diag << From.getVariable();
1954   diag << From.isNonODRUsed();
1955   diag << FixItHint::CreateRemoval(CaptureRange);
1956   return true;
1957 }
1958 
1959 /// Create a field within the lambda class or captured statement record for the
1960 /// given capture.
1961 FieldDecl *Sema::BuildCaptureField(RecordDecl *RD,
1962                                    const sema::Capture &Capture) {
1963   SourceLocation Loc = Capture.getLocation();
1964   QualType FieldType = Capture.getCaptureType();
1965 
1966   TypeSourceInfo *TSI = nullptr;
1967   if (Capture.isVariableCapture()) {
1968     const auto *Var = dyn_cast_or_null<VarDecl>(Capture.getVariable());
1969     if (Var && Var->isInitCapture())
1970       TSI = Var->getTypeSourceInfo();
1971   }
1972 
1973   // FIXME: Should we really be doing this? A null TypeSourceInfo seems more
1974   // appropriate, at least for an implicit capture.
1975   if (!TSI)
1976     TSI = Context.getTrivialTypeSourceInfo(FieldType, Loc);
1977 
1978   // Build the non-static data member.
1979   FieldDecl *Field =
1980       FieldDecl::Create(Context, RD, /*StartLoc=*/Loc, /*IdLoc=*/Loc,
1981                         /*Id=*/nullptr, FieldType, TSI, /*BW=*/nullptr,
1982                         /*Mutable=*/false, ICIS_NoInit);
1983   // If the variable being captured has an invalid type, mark the class as
1984   // invalid as well.
1985   if (!FieldType->isDependentType()) {
1986     if (RequireCompleteSizedType(Loc, FieldType,
1987                                  diag::err_field_incomplete_or_sizeless)) {
1988       RD->setInvalidDecl();
1989       Field->setInvalidDecl();
1990     } else {
1991       NamedDecl *Def;
1992       FieldType->isIncompleteType(&Def);
1993       if (Def && Def->isInvalidDecl()) {
1994         RD->setInvalidDecl();
1995         Field->setInvalidDecl();
1996       }
1997     }
1998   }
1999   Field->setImplicit(true);
2000   Field->setAccess(AS_private);
2001   RD->addDecl(Field);
2002 
2003   if (Capture.isVLATypeCapture())
2004     Field->setCapturedVLAType(Capture.getCapturedVLAType());
2005 
2006   return Field;
2007 }
2008 
2009 ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
2010                                  LambdaScopeInfo *LSI) {
2011   // Collect information from the lambda scope.
2012   SmallVector<LambdaCapture, 4> Captures;
2013   SmallVector<Expr *, 4> CaptureInits;
2014   SourceLocation CaptureDefaultLoc = LSI->CaptureDefaultLoc;
2015   LambdaCaptureDefault CaptureDefault =
2016       mapImplicitCaptureStyle(LSI->ImpCaptureStyle);
2017   CXXRecordDecl *Class;
2018   CXXMethodDecl *CallOperator;
2019   SourceRange IntroducerRange;
2020   bool ExplicitParams;
2021   bool ExplicitResultType;
2022   CleanupInfo LambdaCleanup;
2023   bool ContainsUnexpandedParameterPack;
2024   bool IsGenericLambda;
2025   {
2026     CallOperator = LSI->CallOperator;
2027     Class = LSI->Lambda;
2028     IntroducerRange = LSI->IntroducerRange;
2029     ExplicitParams = LSI->ExplicitParams;
2030     ExplicitResultType = !LSI->HasImplicitReturnType;
2031     LambdaCleanup = LSI->Cleanup;
2032     ContainsUnexpandedParameterPack = LSI->ContainsUnexpandedParameterPack;
2033     IsGenericLambda = Class->isGenericLambda();
2034 
2035     CallOperator->setLexicalDeclContext(Class);
2036     Decl *TemplateOrNonTemplateCallOperatorDecl =
2037         CallOperator->getDescribedFunctionTemplate()
2038         ? CallOperator->getDescribedFunctionTemplate()
2039         : cast<Decl>(CallOperator);
2040 
2041     // FIXME: Is this really the best choice? Keeping the lexical decl context
2042     // set as CurContext seems more faithful to the source.
2043     TemplateOrNonTemplateCallOperatorDecl->setLexicalDeclContext(Class);
2044 
2045     PopExpressionEvaluationContext();
2046 
2047     // True if the current capture has a used capture or default before it.
2048     bool CurHasPreviousCapture = CaptureDefault != LCD_None;
2049     SourceLocation PrevCaptureLoc = CurHasPreviousCapture ?
2050         CaptureDefaultLoc : IntroducerRange.getBegin();
2051 
2052     for (unsigned I = 0, N = LSI->Captures.size(); I != N; ++I) {
2053       const Capture &From = LSI->Captures[I];
2054 
2055       if (From.isInvalid())
2056         return ExprError();
2057 
2058       assert(!From.isBlockCapture() && "Cannot capture __block variables");
2059       bool IsImplicit = I >= LSI->NumExplicitCaptures;
2060       SourceLocation ImplicitCaptureLoc =
2061           IsImplicit ? CaptureDefaultLoc : SourceLocation();
2062 
2063       // Use source ranges of explicit captures for fixits where available.
2064       SourceRange CaptureRange = LSI->ExplicitCaptureRanges[I];
2065 
2066       // Warn about unused explicit captures.
2067       bool IsCaptureUsed = true;
2068       if (!CurContext->isDependentContext() && !IsImplicit &&
2069           !From.isODRUsed()) {
2070         // Initialized captures that are non-ODR used may not be eliminated.
2071         // FIXME: Where did the IsGenericLambda here come from?
2072         bool NonODRUsedInitCapture =
2073             IsGenericLambda && From.isNonODRUsed() && From.isInitCapture();
2074         if (!NonODRUsedInitCapture) {
2075           bool IsLast = (I + 1) == LSI->NumExplicitCaptures;
2076           SourceRange FixItRange;
2077           if (CaptureRange.isValid()) {
2078             if (!CurHasPreviousCapture && !IsLast) {
2079               // If there are no captures preceding this capture, remove the
2080               // following comma.
2081               FixItRange = SourceRange(CaptureRange.getBegin(),
2082                                        getLocForEndOfToken(CaptureRange.getEnd()));
2083             } else {
2084               // Otherwise, remove the comma since the last used capture.
2085               FixItRange = SourceRange(getLocForEndOfToken(PrevCaptureLoc),
2086                                        CaptureRange.getEnd());
2087             }
2088           }
2089 
2090           IsCaptureUsed = !DiagnoseUnusedLambdaCapture(FixItRange, From);
2091         }
2092       }
2093 
2094       if (CaptureRange.isValid()) {
2095         CurHasPreviousCapture |= IsCaptureUsed;
2096         PrevCaptureLoc = CaptureRange.getEnd();
2097       }
2098 
2099       // Map the capture to our AST representation.
2100       LambdaCapture Capture = [&] {
2101         if (From.isThisCapture()) {
2102           // Capturing 'this' implicitly with a default of '[=]' is deprecated,
2103           // because it results in a reference capture. Don't warn prior to
2104           // C++2a; there's nothing that can be done about it before then.
2105           if (getLangOpts().CPlusPlus20 && IsImplicit &&
2106               CaptureDefault == LCD_ByCopy) {
2107             Diag(From.getLocation(), diag::warn_deprecated_this_capture);
2108             Diag(CaptureDefaultLoc, diag::note_deprecated_this_capture)
2109                 << FixItHint::CreateInsertion(
2110                        getLocForEndOfToken(CaptureDefaultLoc), ", this");
2111           }
2112           return LambdaCapture(From.getLocation(), IsImplicit,
2113                                From.isCopyCapture() ? LCK_StarThis : LCK_This);
2114         } else if (From.isVLATypeCapture()) {
2115           return LambdaCapture(From.getLocation(), IsImplicit, LCK_VLAType);
2116         } else {
2117           assert(From.isVariableCapture() && "unknown kind of capture");
2118           ValueDecl *Var = From.getVariable();
2119           LambdaCaptureKind Kind =
2120               From.isCopyCapture() ? LCK_ByCopy : LCK_ByRef;
2121           return LambdaCapture(From.getLocation(), IsImplicit, Kind, Var,
2122                                From.getEllipsisLoc());
2123         }
2124       }();
2125 
2126       // Form the initializer for the capture field.
2127       ExprResult Init = BuildCaptureInit(From, ImplicitCaptureLoc);
2128 
2129       // FIXME: Skip this capture if the capture is not used, the initializer
2130       // has no side-effects, the type of the capture is trivial, and the
2131       // lambda is not externally visible.
2132 
2133       // Add a FieldDecl for the capture and form its initializer.
2134       BuildCaptureField(Class, From);
2135       Captures.push_back(Capture);
2136       CaptureInits.push_back(Init.get());
2137 
2138       if (LangOpts.CUDA)
2139         CUDACheckLambdaCapture(CallOperator, From);
2140     }
2141 
2142     Class->setCaptures(Context, Captures);
2143 
2144     // C++11 [expr.prim.lambda]p6:
2145     //   The closure type for a lambda-expression with no lambda-capture
2146     //   has a public non-virtual non-explicit const conversion function
2147     //   to pointer to function having the same parameter and return
2148     //   types as the closure type's function call operator.
2149     if (Captures.empty() && CaptureDefault == LCD_None)
2150       addFunctionPointerConversions(*this, IntroducerRange, Class,
2151                                     CallOperator);
2152 
2153     // Objective-C++:
2154     //   The closure type for a lambda-expression has a public non-virtual
2155     //   non-explicit const conversion function to a block pointer having the
2156     //   same parameter and return types as the closure type's function call
2157     //   operator.
2158     // FIXME: Fix generic lambda to block conversions.
2159     if (getLangOpts().Blocks && getLangOpts().ObjC && !IsGenericLambda)
2160       addBlockPointerConversion(*this, IntroducerRange, Class, CallOperator);
2161 
2162     // Finalize the lambda class.
2163     SmallVector<Decl*, 4> Fields(Class->fields());
2164     ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
2165                 SourceLocation(), ParsedAttributesView());
2166     CheckCompletedCXXClass(nullptr, Class);
2167   }
2168 
2169   Cleanup.mergeFrom(LambdaCleanup);
2170 
2171   LambdaExpr *Lambda = LambdaExpr::Create(Context, Class, IntroducerRange,
2172                                           CaptureDefault, CaptureDefaultLoc,
2173                                           ExplicitParams, ExplicitResultType,
2174                                           CaptureInits, EndLoc,
2175                                           ContainsUnexpandedParameterPack);
2176   // If the lambda expression's call operator is not explicitly marked constexpr
2177   // and we are not in a dependent context, analyze the call operator to infer
2178   // its constexpr-ness, suppressing diagnostics while doing so.
2179   if (getLangOpts().CPlusPlus17 && !CallOperator->isInvalidDecl() &&
2180       !CallOperator->isConstexpr() &&
2181       !isa<CoroutineBodyStmt>(CallOperator->getBody()) &&
2182       !Class->getDeclContext()->isDependentContext()) {
2183     CallOperator->setConstexprKind(
2184         CheckConstexprFunctionDefinition(CallOperator,
2185                                          CheckConstexprKind::CheckValid)
2186             ? ConstexprSpecKind::Constexpr
2187             : ConstexprSpecKind::Unspecified);
2188   }
2189 
2190   // Emit delayed shadowing warnings now that the full capture list is known.
2191   DiagnoseShadowingLambdaDecls(LSI);
2192 
2193   if (!CurContext->isDependentContext()) {
2194     switch (ExprEvalContexts.back().Context) {
2195     // C++11 [expr.prim.lambda]p2:
2196     //   A lambda-expression shall not appear in an unevaluated operand
2197     //   (Clause 5).
2198     case ExpressionEvaluationContext::Unevaluated:
2199     case ExpressionEvaluationContext::UnevaluatedList:
2200     case ExpressionEvaluationContext::UnevaluatedAbstract:
2201     // C++1y [expr.const]p2:
2202     //   A conditional-expression e is a core constant expression unless the
2203     //   evaluation of e, following the rules of the abstract machine, would
2204     //   evaluate [...] a lambda-expression.
2205     //
2206     // This is technically incorrect, there are some constant evaluated contexts
2207     // where this should be allowed.  We should probably fix this when DR1607 is
2208     // ratified, it lays out the exact set of conditions where we shouldn't
2209     // allow a lambda-expression.
2210     case ExpressionEvaluationContext::ConstantEvaluated:
2211     case ExpressionEvaluationContext::ImmediateFunctionContext:
2212       // We don't actually diagnose this case immediately, because we
2213       // could be within a context where we might find out later that
2214       // the expression is potentially evaluated (e.g., for typeid).
2215       ExprEvalContexts.back().Lambdas.push_back(Lambda);
2216       break;
2217 
2218     case ExpressionEvaluationContext::DiscardedStatement:
2219     case ExpressionEvaluationContext::PotentiallyEvaluated:
2220     case ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed:
2221       break;
2222     }
2223   }
2224 
2225   return MaybeBindToTemporary(Lambda);
2226 }
2227 
2228 ExprResult Sema::BuildBlockForLambdaConversion(SourceLocation CurrentLocation,
2229                                                SourceLocation ConvLocation,
2230                                                CXXConversionDecl *Conv,
2231                                                Expr *Src) {
2232   // Make sure that the lambda call operator is marked used.
2233   CXXRecordDecl *Lambda = Conv->getParent();
2234   CXXMethodDecl *CallOperator
2235     = cast<CXXMethodDecl>(
2236         Lambda->lookup(
2237           Context.DeclarationNames.getCXXOperatorName(OO_Call)).front());
2238   CallOperator->setReferenced();
2239   CallOperator->markUsed(Context);
2240 
2241   ExprResult Init = PerformCopyInitialization(
2242       InitializedEntity::InitializeLambdaToBlock(ConvLocation, Src->getType()),
2243       CurrentLocation, Src);
2244   if (!Init.isInvalid())
2245     Init = ActOnFinishFullExpr(Init.get(), /*DiscardedValue*/ false);
2246 
2247   if (Init.isInvalid())
2248     return ExprError();
2249 
2250   // Create the new block to be returned.
2251   BlockDecl *Block = BlockDecl::Create(Context, CurContext, ConvLocation);
2252 
2253   // Set the type information.
2254   Block->setSignatureAsWritten(CallOperator->getTypeSourceInfo());
2255   Block->setIsVariadic(CallOperator->isVariadic());
2256   Block->setBlockMissingReturnType(false);
2257 
2258   // Add parameters.
2259   SmallVector<ParmVarDecl *, 4> BlockParams;
2260   for (unsigned I = 0, N = CallOperator->getNumParams(); I != N; ++I) {
2261     ParmVarDecl *From = CallOperator->getParamDecl(I);
2262     BlockParams.push_back(ParmVarDecl::Create(
2263         Context, Block, From->getBeginLoc(), From->getLocation(),
2264         From->getIdentifier(), From->getType(), From->getTypeSourceInfo(),
2265         From->getStorageClass(),
2266         /*DefArg=*/nullptr));
2267   }
2268   Block->setParams(BlockParams);
2269 
2270   Block->setIsConversionFromLambda(true);
2271 
2272   // Add capture. The capture uses a fake variable, which doesn't correspond
2273   // to any actual memory location. However, the initializer copy-initializes
2274   // the lambda object.
2275   TypeSourceInfo *CapVarTSI =
2276       Context.getTrivialTypeSourceInfo(Src->getType());
2277   VarDecl *CapVar = VarDecl::Create(Context, Block, ConvLocation,
2278                                     ConvLocation, nullptr,
2279                                     Src->getType(), CapVarTSI,
2280                                     SC_None);
2281   BlockDecl::Capture Capture(/*variable=*/CapVar, /*byRef=*/false,
2282                              /*nested=*/false, /*copy=*/Init.get());
2283   Block->setCaptures(Context, Capture, /*CapturesCXXThis=*/false);
2284 
2285   // Add a fake function body to the block. IR generation is responsible
2286   // for filling in the actual body, which cannot be expressed as an AST.
2287   Block->setBody(new (Context) CompoundStmt(ConvLocation));
2288 
2289   // Create the block literal expression.
2290   Expr *BuildBlock = new (Context) BlockExpr(Block, Conv->getConversionType());
2291   ExprCleanupObjects.push_back(Block);
2292   Cleanup.setExprNeedsCleanups(true);
2293 
2294   return BuildBlock;
2295 }
2296 
2297 static FunctionDecl *getPatternFunctionDecl(FunctionDecl *FD) {
2298   if (FD->getTemplatedKind() == FunctionDecl::TK_MemberSpecialization) {
2299     while (FD->getInstantiatedFromMemberFunction())
2300       FD = FD->getInstantiatedFromMemberFunction();
2301     return FD;
2302   }
2303 
2304   if (FD->getTemplatedKind() == FunctionDecl::TK_DependentNonTemplate)
2305     return FD->getInstantiatedFromDecl();
2306 
2307   FunctionTemplateDecl *FTD = FD->getPrimaryTemplate();
2308   if (!FTD)
2309     return nullptr;
2310 
2311   while (FTD->getInstantiatedFromMemberTemplate())
2312     FTD = FTD->getInstantiatedFromMemberTemplate();
2313 
2314   return FTD->getTemplatedDecl();
2315 }
2316 
2317 Sema::LambdaScopeForCallOperatorInstantiationRAII::
2318     LambdaScopeForCallOperatorInstantiationRAII(
2319         Sema &SemaRef, FunctionDecl *FD, MultiLevelTemplateArgumentList MLTAL,
2320         LocalInstantiationScope &Scope, bool ShouldAddDeclsFromParentScope)
2321     : FunctionScopeRAII(SemaRef) {
2322   if (!isLambdaCallOperator(FD)) {
2323     FunctionScopeRAII::disable();
2324     return;
2325   }
2326 
2327   SemaRef.RebuildLambdaScopeInfo(cast<CXXMethodDecl>(FD));
2328 
2329   FunctionDecl *Pattern = getPatternFunctionDecl(FD);
2330   if (Pattern) {
2331     SemaRef.addInstantiatedCapturesToScope(FD, Pattern, Scope, MLTAL);
2332 
2333     FunctionDecl *ParentFD = FD;
2334     while (ShouldAddDeclsFromParentScope) {
2335 
2336       ParentFD =
2337           dyn_cast<FunctionDecl>(getLambdaAwareParentOfDeclContext(ParentFD));
2338       Pattern =
2339           dyn_cast<FunctionDecl>(getLambdaAwareParentOfDeclContext(Pattern));
2340 
2341       if (!FD || !Pattern)
2342         break;
2343 
2344       SemaRef.addInstantiatedParametersToScope(ParentFD, Pattern, Scope, MLTAL);
2345       SemaRef.addInstantiatedLocalVarsToScope(ParentFD, Pattern, Scope);
2346     }
2347   }
2348 }
2349