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	Val: 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>(Val: FunctionScopes[CurScopeIndex])->CallOperator;
87
88	do {
89	const clang::sema::LambdaScopeInfo *LSI =
90	cast<sema::LambdaScopeInfo>(Val: 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(DC: EnclosingDC);
125
126	assert(CurScopeIndex);
127	--CurScopeIndex;
128	} while (!EnclosingDC->isTranslationUnit() &&
129	EnclosingDC->isDependentContext() &&
130	isLambdaCallOperator(DC: 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>(Val: 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(Var: VarToCapture,
208	/*ExprVarIsUsedInLoc*/ Loc: SourceLocation(),
209	Kind: clang::Sema::TryCapture_Implicit,
210	/*EllipsisLoc*/ SourceLocation(),
211	/*BuildAndDiagnose*/ false, CaptureType,
212	DeclRefType, FunctionScopeIndexToStopAt: &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	Loc: CaptureReadyLambdaLSI->PotentialThisCaptureLocation,
222	/*Explicit*/ false, /*BuildAndDiagnose*/ false,
223	FunctionScopeIndexToStopAt: &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	C: SemaRef.Context,
235	/*Template kw loc*/ TemplateLoc: SourceLocation(),
236	/*L angle loc*/ LAngleLoc: LSI->ExplicitTemplateParamsRange.getBegin(),
237	Params: LSI->TemplateParams,
238	/*R angle loc*/RAngleLoc: LSI->ExplicitTemplateParamsRange.getEnd(),
239	RequiresClause: 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(LSI: getCurLambda(), SemaRef&: *this);
254	// Start constructing the lambda class.
255	CXXRecordDecl *Class = CXXRecordDecl::CreateLambda(
256	C: Context, DC, Info, Loc: IntroducerRange.getBegin(), DependencyKind: LambdaDependencyKind,
257	IsGeneric: 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>(Val: 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>(Val: 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>(Val: 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>(Val: Var)) {
312	if (!VTS->isExplicitSpecialization())
313	Kind = TemplatedVariable;
314	}
315	} else if (isa<FieldDecl>(Val: ManglingContextDecl)) {
316	Kind = DataMember;
317	} else if (isa<ImplicitConceptSpecializationDecl>(Val: 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>(Val: ManglingContextDecl))) ||
330	isInInlineFunction(DC: CurContext)) {
331	while (auto *CD = dyn_cast<CapturedDecl>(Val: DC))
332	DC = CD->getParent();
333	return std::make_tuple(args: &Context.getManglingNumberContext(DC), args: nullptr);
334	}
335
336	return std::make_tuple(args: nullptr, args: 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	args: &Context.getManglingNumberContext(ASTContext::NeedExtraManglingDecl,
353	D: ManglingContextDecl),
354	args&: 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(TypeWithAuto: Result);
375	MethodType = S.Context.getFunctionType(ResultTy: Result, Args: FPT->getParamTypes(),
376	EPI: 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, D: 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(args&: MCtx, args&: Numbering.ContextDecl) =
440	getCurrentMangleNumberContext(DC: 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(CallOperator: Method);
457	Numbering.DeviceManglingNumber = MCtx->getDeviceManglingNumber(Method);
458	Class->setLambdaNumbering(Numbering);
459
460	if (auto *Source =
461	dyn_cast_or_null<ExternalSemaSource>(Val: Context.getExternalSource()))
462	Source->AssignedLambdaNumbering(Lambda: 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(in_start: TParams.begin(), in_end: 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>(Val: E)) {
535	if (EnumConstantDecl *D
536	= dyn_cast<EnumConstantDecl>(Val: 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>(Val: E)) {
545	if (BO->getOpcode() == BO_Comma)
546	return findEnumForBlockReturn(E: 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>(Val: E)) {
553	if (Expr *last = dyn_cast_or_null<Expr>(Val: SE->getSubStmt()->body_back()))
554	return findEnumForBlockReturn(E: 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>(Val: E)) {
562	if (EnumDecl *ED = findEnumForBlockReturn(E: CO->getTrueExpr()))
563	if (ED == findEnumForBlockReturn(E: 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>(Val: 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(E: 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(ret: *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(ret: *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(T1: retValue->getType(), T2: 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>(Val: retValue);
635
636	Expr *E = (cleanups ? cleanups->getSubExpr() : retValue);
637	E = ImplicitCastExpr::Create(Context: S.Context, T: returnType, Kind: CK_IntegralCast, Operand: E,
638	/*base path*/ BasePath: nullptr, Cat: VK_PRValue,
639	FPO: 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(returns: 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(ResultType: ReturnType) ==
721	Context.getCanonicalFunctionResultType(ResultType: 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>(T: DeductType);
750	TL.setNameLoc(Loc);
751	if (ByRef) {
752	DeductType = BuildReferenceType(T: DeductType, LValueRef: true, Loc, Entity: Id);
753	assert(!DeductType.isNull() && "can't build reference to auto");
754	TLB.push<ReferenceTypeLoc>(T: 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(Pattern: DeductType, NumExpansions,
762	/*ExpectPackInType=*/false);
763	TLB.push<PackExpansionTypeLoc>(T: 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, T: DeductType);
770
771	// Deduce the type of the init capture.
772	QualType DeducedType = deduceVarTypeFromInitializer(
773	/*VarDecl*/VDecl: nullptr, Name: DeclarationName(Id), Type: DeductType, TSI,
774	Range: SourceRange(Loc, Loc), DirectInit: IsDirectInit, Init);
775	if (DeducedType.isNull())
776	return QualType();
777
778	// Are we a non-list direct initialization?
779	ParenListExpr *CXXDirectInit = dyn_cast<ParenListExpr>(Val: 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(VarID: Id, FieldType: DeducedType, Loc);
785	InitializationKind Kind =
786	IsDirectInit
787	? (CXXDirectInit ? InitializationKind::CreateDirect(
788	InitLoc: Loc, LParenLoc: Init->getBeginLoc(), RParenLoc: Init->getEndLoc())
789	: InitializationKind::CreateDirectList(InitLoc: Loc))
790	: InitializationKind::CreateCopy(InitLoc: Loc, EqualLoc: 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(S&: *this, Entity, Kind, Args, ResultType: &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(T: 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(C&: Context, DC: DeclCtx, StartLoc: Loc, IdLoc: Loc, Id,
821	T: InitCaptureType, TInfo: TSI, S: 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, isByref: ByRef,
836	/*isNested=*/false, Loc: Var->getLocation(), EllipsisLoc: SourceLocation(),
837	CaptureType: 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>(Val: 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(space: 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(ResultTy: DefaultTypeForNoTrailingReturn,
870	Args: std::nullopt, EPI);
871	return S.Context.getTrivialTypeSourceInfo(T: 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(D&: 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(T: 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(D&: 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(Loc: Intro.Range.getBegin(), T: MethodTyInfo,
925	UPPC: 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(Op: OO_Call);
941	DeclarationNameLoc MethodNameLoc =
942	DeclarationNameLoc::makeCXXOperatorNameLoc(Range: IntroducerRange.getBegin());
943	CXXMethodDecl *Method = CXXMethodDecl::Create(
944	C&: Context, RD: Class, StartLoc: SourceLocation(),
945	NameInfo: DeclarationNameInfo(MethodName, IntroducerRange.getBegin(),
946	MethodNameLoc),
947	T: QualType(), /*Tinfo=*/TInfo: nullptr, SC: SC_None,
948	UsesFPIntrin: getCurFPFeatures().isFPConstrained(),
949	/*isInline=*/true, ConstexprKind: ConstexprSpecKind::Unspecified, EndLocation: 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	C&: Context, DC: Class, L: CallOperator->getLocation(), Name: CallOperator->getDeclName(),
961	Params: TemplateParams, Decl: 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(S&: *this);
974
975	if (TrailingRequiresClause)
976	Method->setTrailingRequiresClause(TrailingRequiresClause);
977
978	TemplateParameterList *TemplateParams =
979	getGenericLambdaTemplateParameterList(LSI, SemaRef&: *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(S&: *this, Class: LSI->Lambda,
1002	TemplateParams, MethodTypeInfo: MethodTyInfo));
1003	Method->setConstexprKind(ConstexprKind);
1004	Method->setStorageClass(SC);
1005	if (!Params.empty()) {
1006	CheckParmsForFunctionDef(Parameters: 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(S&: *this, LSI, CallOperator: Method, ExplicitResultType: 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	IntroducerRange: Intro.Range, /*Info=*/nullptr, LambdaDependencyKind, CaptureDefault: Intro.Default);
1051	LSI->Lambda = Class;
1052
1053	CXXMethodDecl *Method = CreateLambdaCallOperator(IntroducerRange: 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(Loc: C->Loc, /*Explicit=*/true, /*BuildAndDiagnose*/ true,
1106	/*FunctionScopeIndexToStopAtPtr*/ FunctionScopeIndexToStopAt: nullptr,
1107	ByCopy: 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(E: C->Init.get(), UPPC: 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>(Val: Var))
1155	CheckShadow(S: CurrentScope, D: 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, S: 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(S: CurScope, SS&: ScopeSpec, R, CCC&: 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(KV: 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(Loc: 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, Var: cast<VarDecl>(Val: Var), ByRef: 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, Loc: 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(S&: *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(S&: *this);
1307	PushDeclContext(LambdaScope, LSI->CallOperator);
1308
1309	for (const DeclaratorChunk::ParamInfo &P : Params) {
1310	auto *Param = cast<ParmVarDecl>(Val: 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, SemaRef&: *this);
1322	if (TemplateParams) {
1323	AddTemplateParametersToLambdaCallOperator(CallOperator: LSI->CallOperator, Class: 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(S&: *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(idx&: Index);
1346	const auto &Object = ParamInfo.getTypeObject(i: 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	S&: *this, Intro, ParamInfo, CurScope: getCurScope(), Loc: TypeLoc, ExplicitResultType);
1357
1358	LSI->ExplicitParams = ParamInfo.getNumTypeObjects() != 0;
1359
1360	if (ParamInfo.isFunctionDeclarator() != 0 &&
1361	!FTIHasSingleVoidParameter(FTI: ParamInfo.getFunctionTypeInfo())) {
1362	const auto &FTI = ParamInfo.getFunctionTypeInfo();
1363	Params.reserve(N: Params.size());
1364	for (unsigned I = 0; I < FTI.NumParams; ++I) {
1365	auto *Param = cast<ParmVarDecl>(Val: FTI.Params[I].Param);
1366	Param->setScopeInfo(scopeDepth: 0, parameterIndex: Params.size());
1367	Params.push_back(Elt: Param);
1368	}
1369	}
1370
1371	bool IsLambdaStatic =
1372	ParamInfo.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_static;
1373
1374	CompleteLambdaCallOperator(
1375	Method, LambdaLoc: Intro.Range.getBegin(), CallOperatorLoc,
1376	TrailingRequiresClause: ParamInfo.getTrailingRequiresClause(), MethodTyInfo,
1377	ConstexprKind: ParamInfo.getDeclSpec().getConstexprSpecifier(),
1378	SC: IsLambdaStatic ? SC_Static : SC_None, Params, HasExplicitResultType: 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, SemaRef&: *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(Decl: *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>(Val: 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(S: nullptr, RecLoc: Class->getLocation(), TagDecl: Class, Fields, LBrac: SourceLocation(),
1513	RBrac: SourceLocation(), AttrList: ParsedAttributesView());
1514	CheckCompletedCXXClass(S: nullptr, Record: 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	IsVariadic: CallOpProto.isVariadic(), /*IsCXXMethod=*/false);
1524	CallingConv DefaultMember = S.Context.getDefaultCallingConvention(
1525	IsVariadic: 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(C&: Convs);
1545	llvm::iterator_range<CallingConv *> Range(
1546	std::begin(arr&: Convs), std::unique(first: std::begin(arr&: Convs), last: std::end(arr&: 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	IsVariadic: CallOpProto->isVariadic(), /*IsCXXMethod=*/false);
1572	CallingConv DefaultMember = S.Context.getDefaultCallingConvention(
1573	IsVariadic: 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: 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(ResultTy: CallOpProto->getReturnType(),
1593	Args: CallOpProto->getParamTypes(), EPI: 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(T: 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(ResultTy: PtrToFunctionTy, Args: std::nullopt, EPI: ConvExtInfo);
1623
1624	SourceLocation Loc = IntroducerRange.getBegin();
1625	DeclarationName ConversionName
1626	= S.Context.DeclarationNames.getCXXConversionFunctionName(
1627	Ty: S.Context.getCanonicalType(T: 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(T: PtrToFunctionTy, Loc);
1646	DeclarationNameLoc ConvNameLoc =
1647	DeclarationNameLoc::makeNamedTypeLoc(TInfo: ConvNamePtrToFunctionTSI);
1648
1649	// The conversion function is a conversion to a pointer-to-function.
1650	TypeSourceInfo *ConvTSI = S.Context.getTrivialTypeSourceInfo(T: 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(Elt: ParmVarDecl::Create(
1681	C&: S.Context,
1682	// Temporarily add to the TU. This is set to the invoker below.
1683	DC: S.Context.getTranslationUnitDecl(), StartLoc: From->getBeginLoc(),
1684	IdLoc: From->getLocation(), Id: From->getIdentifier(), T: From->getType(),
1685	TInfo: From->getTypeSourceInfo(), S: From->getStorageClass(),
1686	/*DefArg=*/nullptr));
1687	CallOpConvTL.setParam(I, From);
1688	CallOpConvNameTL.setParam(I, From);
1689	}
1690
1691	CXXConversionDecl *Conversion = CXXConversionDecl::Create(
1692	C&: S.Context, RD: Class, StartLoc: Loc,
1693	NameInfo: DeclarationNameInfo(ConversionName, Loc, ConvNameLoc), T: ConvTy, TInfo: ConvTSI,
1694	UsesFPIntrin: S.getCurFPFeatures().isFPConstrained(),
1695	/*isInline=*/true, ES: ExplicitSpecifier(),
1696	ConstexprKind: S.getLangOpts().CPlusPlus17 ? ConstexprSpecKind::Constexpr
1697	: ConstexprSpecKind::Unspecified,
1698	EndLocation: 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(C&: S.Context, DC: Class,
1714	L: Loc, Name: ConversionName,
1715	Params: TemplateCallOperator->getTemplateParameters(),
1716	Decl: 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(Name: 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	C&: S.Context, RD: Class, StartLoc: Loc, NameInfo: DeclarationNameInfo(InvokerName, Loc),
1744	T: InvokerFunctionTy, TInfo: CallOperator->getTypeSourceInfo(), SC: SC_Static,
1745	UsesFPIntrin: S.getCurFPFeatures().isFPConstrained(),
1746	/*isInline=*/true, ConstexprKind: CallOperator->getConstexprKind(),
1747	EndLocation: 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	C&: S.Context, DC: Class, L: Loc, Name: InvokerName,
1759	Params: TemplateCallOperator->getTemplateParameters(), Decl: 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: *CallOpProto, F: [&](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, CC: getLambdaConversionFunctionCallConv(S, CallOpProto));
1797	QualType BlockPtrTy = S.Context.getBlockPointerType(T: 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(ResultTy: BlockPtrTy, Args: std::nullopt, EPI: ConversionEPI);
1806
1807	SourceLocation Loc = IntroducerRange.getBegin();
1808	DeclarationName Name
1809	= S.Context.DeclarationNames.getCXXConversionFunctionName(
1810	Ty: S.Context.getCanonicalType(T: BlockPtrTy));
1811	DeclarationNameLoc NameLoc = DeclarationNameLoc::makeNamedTypeLoc(
1812	TInfo: S.Context.getTrivialTypeSourceInfo(T: BlockPtrTy, Loc));
1813	CXXConversionDecl *Conversion = CXXConversionDecl::Create(
1814	C&: S.Context, RD: Class, StartLoc: Loc, NameInfo: DeclarationNameInfo(Name, Loc, NameLoc), T: ConvTy,
1815	TInfo: S.Context.getTrivialTypeSourceInfo(T: ConvTy, Loc),
1816	UsesFPIntrin: S.getCurFPFeatures().isFPConstrained(),
1817	/*isInline=*/true, ES: ExplicitSpecifier(), ConstexprKind: ConstexprSpecKind::Unspecified,
1818	EndLocation: 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>(Val: 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, Type: ThisTy, IsImplicit: ImplicitCaptureLoc.isValid());
1858	if (Cap.isCopyCapture())
1859	Init = CreateBuiltinUnaryOp(OpLoc: Loc, Opc: UO_Deref, InputExpr: 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	VarID: Name, FieldType: Cap.getCaptureType(), Loc);
1882	InitializationKind InitKind =
1883	InitializationKind::CreateDirect(InitLoc: Loc, LParenLoc: Loc, RParenLoc: Loc);
1884	InitializationSequence InitSeq(*this, Entity, InitKind, InitExpr);
1885	return InitSeq.Perform(S&: *this, Entity, Kind: InitKind, Args: InitExpr);
1886	}
1887
1888	ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body) {
1889	LambdaScopeInfo LSI = *cast<LambdaScopeInfo>(Val: FunctionScopes.back());
1890	ActOnFinishFunctionBody(LSI.CallOperator, Body);
1891	return BuildLambdaExpr(StartLoc, EndLoc: Body->getEndLoc(), LSI: &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>(Val: From.getVariable())->getInit();
1913	if (Init && Init->HasSideEffects(Ctx: 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(RemoveRange: 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>(Val: 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(T: 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: &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(ICS: 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>(Val: 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(Loc: CaptureRange.getEnd()));
2083	} else {
2084	// Otherwise, remove the comma since the last used capture.
2085	FixItRange = SourceRange(getLocForEndOfToken(Loc: PrevCaptureLoc),
2086	CaptureRange.getEnd());
2087	}
2088	}
2089
2090	IsCaptureUsed = !DiagnoseUnusedLambdaCapture(CaptureRange: 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(Cap: 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(Elt: Capture);
2136	CaptureInits.push_back(Elt: Init.get());
2137
2138	if (LangOpts.CUDA)
2139	CUDACheckLambdaCapture(D: CallOperator, Capture: 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(S&: *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(S&: *this, IntroducerRange, Class, CallOperator);
2161
2162	// Finalize the lambda class.
2163	SmallVector<Decl*, 4> Fields(Class->fields());
2164	ActOnFields(S: nullptr, RecLoc: Class->getLocation(), TagDecl: Class, Fields, LBrac: SourceLocation(),
2165	RBrac: SourceLocation(), AttrList: ParsedAttributesView());
2166	CheckCompletedCXXClass(S: nullptr, Record: Class);
2167	}
2168
2169	Cleanup.mergeFrom(Rhs: LambdaCleanup);
2170
2171	LambdaExpr *Lambda = LambdaExpr::Create(C: Context, Class, IntroducerRange,
2172	CaptureDefault, CaptureDefaultLoc,
2173	ExplicitParams, ExplicitResultType,
2174	CaptureInits, ClosingBrace: 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>(Val: 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(Elt: 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(Op: OO_Call)).front());
2238	CallOperator->setReferenced();
2239	CallOperator->markUsed(Context);
2240
2241	ExprResult Init = PerformCopyInitialization(
2242	Entity: InitializedEntity::InitializeLambdaToBlock(BlockVarLoc: ConvLocation, Type: Src->getType()),
2243	EqualLoc: CurrentLocation, Init: Src);
2244	if (!Init.isInvalid())
2245	Init = ActOnFinishFullExpr(Expr: 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(C&: Context, DC: CurContext, L: 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(Elt: ParmVarDecl::Create(
2263	C&: Context, DC: Block, StartLoc: From->getBeginLoc(), IdLoc: From->getLocation(),
2264	Id: From->getIdentifier(), T: From->getType(), TInfo: From->getTypeSourceInfo(),
2265	S: 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(T: 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, Captures: 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(Elt: 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(CallOperator: cast<CXXMethodDecl>(Val: FD));
2328
2329	FunctionDecl *Pattern = getPatternFunctionDecl(FD);
2330	if (Pattern) {
2331	SemaRef.addInstantiatedCapturesToScope(Function: FD, PatternDecl: Pattern, Scope, TemplateArgs: MLTAL);
2332
2333	FunctionDecl *ParentFD = FD;
2334	while (ShouldAddDeclsFromParentScope) {
2335
2336	ParentFD =
2337	dyn_cast<FunctionDecl>(Val: getLambdaAwareParentOfDeclContext(ParentFD));
2338	Pattern =
2339	dyn_cast<FunctionDecl>(Val: getLambdaAwareParentOfDeclContext(Pattern));
2340
2341	if (!FD || !Pattern)
2342	break;
2343
2344	SemaRef.addInstantiatedParametersToScope(Function: ParentFD, PatternDecl: Pattern, Scope, TemplateArgs: MLTAL);
2345	SemaRef.addInstantiatedLocalVarsToScope(Function: ParentFD, PatternDecl: Pattern, Scope);
2346	}
2347	}
2348	}
2349