1 //===------- SemaTemplateVariadic.cpp - C++ Variadic Templates ------------===/
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 //===----------------------------------------------------------------------===/
8 // This file implements semantic analysis for C++0x variadic templates.
9 //===----------------------------------------------------------------------===/
11 #include "clang/Sema/Sema.h"
12 #include "TypeLocBuilder.h"
13 #include "clang/AST/Expr.h"
14 #include "clang/AST/RecursiveASTVisitor.h"
15 #include "clang/AST/TypeLoc.h"
16 #include "clang/Sema/Lookup.h"
17 #include "clang/Sema/ParsedTemplate.h"
18 #include "clang/Sema/ScopeInfo.h"
19 #include "clang/Sema/SemaInternal.h"
20 #include "clang/Sema/Template.h"
22 using namespace clang;
24 //----------------------------------------------------------------------------
25 // Visitor that collects unexpanded parameter packs
26 //----------------------------------------------------------------------------
29 /// A class that collects unexpanded parameter packs.
30 class CollectUnexpandedParameterPacksVisitor :
31 public RecursiveASTVisitor<CollectUnexpandedParameterPacksVisitor>
33 typedef RecursiveASTVisitor<CollectUnexpandedParameterPacksVisitor>
36 SmallVectorImpl<UnexpandedParameterPack> &Unexpanded;
38 bool InLambda = false;
39 unsigned DepthLimit = (unsigned)-1;
41 void addUnexpanded(NamedDecl *ND, SourceLocation Loc = SourceLocation()) {
42 if (auto *VD = dyn_cast<VarDecl>(ND)) {
43 // For now, the only problematic case is a generic lambda's templated
44 // call operator, so we don't need to look for all the other ways we
45 // could have reached a dependent parameter pack.
46 auto *FD = dyn_cast<FunctionDecl>(VD->getDeclContext());
47 auto *FTD = FD ? FD->getDescribedFunctionTemplate() : nullptr;
48 if (FTD && FTD->getTemplateParameters()->getDepth() >= DepthLimit)
50 } else if (getDepthAndIndex(ND).first >= DepthLimit)
53 Unexpanded.push_back({ND, Loc});
55 void addUnexpanded(const TemplateTypeParmType *T,
56 SourceLocation Loc = SourceLocation()) {
57 if (T->getDepth() < DepthLimit)
58 Unexpanded.push_back({T, Loc});
62 explicit CollectUnexpandedParameterPacksVisitor(
63 SmallVectorImpl<UnexpandedParameterPack> &Unexpanded)
64 : Unexpanded(Unexpanded) {}
66 bool shouldWalkTypesOfTypeLocs() const { return false; }
68 //------------------------------------------------------------------------
69 // Recording occurrences of (unexpanded) parameter packs.
70 //------------------------------------------------------------------------
72 /// Record occurrences of template type parameter packs.
73 bool VisitTemplateTypeParmTypeLoc(TemplateTypeParmTypeLoc TL) {
74 if (TL.getTypePtr()->isParameterPack())
75 addUnexpanded(TL.getTypePtr(), TL.getNameLoc());
79 /// Record occurrences of template type parameter packs
80 /// when we don't have proper source-location information for
83 /// Ideally, this routine would never be used.
84 bool VisitTemplateTypeParmType(TemplateTypeParmType *T) {
85 if (T->isParameterPack())
91 /// Record occurrences of function and non-type template
92 /// parameter packs in an expression.
93 bool VisitDeclRefExpr(DeclRefExpr *E) {
94 if (E->getDecl()->isParameterPack())
95 addUnexpanded(E->getDecl(), E->getLocation());
100 /// Record occurrences of template template parameter packs.
101 bool TraverseTemplateName(TemplateName Template) {
102 if (auto *TTP = dyn_cast_or_null<TemplateTemplateParmDecl>(
103 Template.getAsTemplateDecl())) {
104 if (TTP->isParameterPack())
108 return inherited::TraverseTemplateName(Template);
111 /// Suppress traversal into Objective-C container literal
112 /// elements that are pack expansions.
113 bool TraverseObjCDictionaryLiteral(ObjCDictionaryLiteral *E) {
114 if (!E->containsUnexpandedParameterPack())
117 for (unsigned I = 0, N = E->getNumElements(); I != N; ++I) {
118 ObjCDictionaryElement Element = E->getKeyValueElement(I);
119 if (Element.isPackExpansion())
122 TraverseStmt(Element.Key);
123 TraverseStmt(Element.Value);
127 //------------------------------------------------------------------------
128 // Pruning the search for unexpanded parameter packs.
129 //------------------------------------------------------------------------
131 /// Suppress traversal into statements and expressions that
132 /// do not contain unexpanded parameter packs.
133 bool TraverseStmt(Stmt *S) {
134 Expr *E = dyn_cast_or_null<Expr>(S);
135 if ((E && E->containsUnexpandedParameterPack()) || InLambda)
136 return inherited::TraverseStmt(S);
141 /// Suppress traversal into types that do not contain
142 /// unexpanded parameter packs.
143 bool TraverseType(QualType T) {
144 if ((!T.isNull() && T->containsUnexpandedParameterPack()) || InLambda)
145 return inherited::TraverseType(T);
150 /// Suppress traversal into types with location information
151 /// that do not contain unexpanded parameter packs.
152 bool TraverseTypeLoc(TypeLoc TL) {
153 if ((!TL.getType().isNull() &&
154 TL.getType()->containsUnexpandedParameterPack()) ||
156 return inherited::TraverseTypeLoc(TL);
161 /// Suppress traversal of parameter packs.
162 bool TraverseDecl(Decl *D) {
163 // A function parameter pack is a pack expansion, so cannot contain
164 // an unexpanded parameter pack. Likewise for a template parameter
165 // pack that contains any references to other packs.
166 if (D && D->isParameterPack())
169 return inherited::TraverseDecl(D);
172 /// Suppress traversal of pack-expanded attributes.
173 bool TraverseAttr(Attr *A) {
174 if (A->isPackExpansion())
177 return inherited::TraverseAttr(A);
180 /// Suppress traversal of pack expansion expressions and types.
182 bool TraversePackExpansionType(PackExpansionType *T) { return true; }
183 bool TraversePackExpansionTypeLoc(PackExpansionTypeLoc TL) { return true; }
184 bool TraversePackExpansionExpr(PackExpansionExpr *E) { return true; }
185 bool TraverseCXXFoldExpr(CXXFoldExpr *E) { return true; }
189 /// Suppress traversal of using-declaration pack expansion.
190 bool TraverseUnresolvedUsingValueDecl(UnresolvedUsingValueDecl *D) {
191 if (D->isPackExpansion())
194 return inherited::TraverseUnresolvedUsingValueDecl(D);
197 /// Suppress traversal of using-declaration pack expansion.
198 bool TraverseUnresolvedUsingTypenameDecl(UnresolvedUsingTypenameDecl *D) {
199 if (D->isPackExpansion())
202 return inherited::TraverseUnresolvedUsingTypenameDecl(D);
205 /// Suppress traversal of template argument pack expansions.
206 bool TraverseTemplateArgument(const TemplateArgument &Arg) {
207 if (Arg.isPackExpansion())
210 return inherited::TraverseTemplateArgument(Arg);
213 /// Suppress traversal of template argument pack expansions.
214 bool TraverseTemplateArgumentLoc(const TemplateArgumentLoc &ArgLoc) {
215 if (ArgLoc.getArgument().isPackExpansion())
218 return inherited::TraverseTemplateArgumentLoc(ArgLoc);
221 /// Suppress traversal of base specifier pack expansions.
222 bool TraverseCXXBaseSpecifier(const CXXBaseSpecifier &Base) {
223 if (Base.isPackExpansion())
226 return inherited::TraverseCXXBaseSpecifier(Base);
229 /// Suppress traversal of mem-initializer pack expansions.
230 bool TraverseConstructorInitializer(CXXCtorInitializer *Init) {
231 if (Init->isPackExpansion())
234 return inherited::TraverseConstructorInitializer(Init);
237 /// Note whether we're traversing a lambda containing an unexpanded
238 /// parameter pack. In this case, the unexpanded pack can occur anywhere,
239 /// including all the places where we normally wouldn't look. Within a
240 /// lambda, we don't propagate the 'contains unexpanded parameter pack' bit
241 /// outside an expression.
242 bool TraverseLambdaExpr(LambdaExpr *Lambda) {
243 // The ContainsUnexpandedParameterPack bit on a lambda is always correct,
244 // even if it's contained within another lambda.
245 if (!Lambda->containsUnexpandedParameterPack())
248 bool WasInLambda = InLambda;
249 unsigned OldDepthLimit = DepthLimit;
252 if (auto *TPL = Lambda->getTemplateParameterList())
253 DepthLimit = TPL->getDepth();
255 inherited::TraverseLambdaExpr(Lambda);
257 InLambda = WasInLambda;
258 DepthLimit = OldDepthLimit;
262 /// Suppress traversal within pack expansions in lambda captures.
263 bool TraverseLambdaCapture(LambdaExpr *Lambda, const LambdaCapture *C,
265 if (C->isPackExpansion())
268 return inherited::TraverseLambdaCapture(Lambda, C, Init);
273 /// Determine whether it's possible for an unexpanded parameter pack to
274 /// be valid in this location. This only happens when we're in a declaration
275 /// that is nested within an expression that could be expanded, such as a
276 /// lambda-expression within a function call.
278 /// This is conservatively correct, but may claim that some unexpanded packs are
279 /// permitted when they are not.
280 bool Sema::isUnexpandedParameterPackPermitted() {
281 for (auto *SI : FunctionScopes)
282 if (isa<sema::LambdaScopeInfo>(SI))
287 /// Diagnose all of the unexpanded parameter packs in the given
290 Sema::DiagnoseUnexpandedParameterPacks(SourceLocation Loc,
291 UnexpandedParameterPackContext UPPC,
292 ArrayRef<UnexpandedParameterPack> Unexpanded) {
293 if (Unexpanded.empty())
296 // If we are within a lambda expression and referencing a pack that is not
297 // declared within the lambda itself, that lambda contains an unexpanded
298 // parameter pack, and we are done.
299 // FIXME: Store 'Unexpanded' on the lambda so we don't need to recompute it
301 SmallVector<UnexpandedParameterPack, 4> LambdaParamPackReferences;
302 if (auto *LSI = getEnclosingLambda()) {
303 for (auto &Pack : Unexpanded) {
304 auto DeclaresThisPack = [&](NamedDecl *LocalPack) {
305 if (auto *TTPT = Pack.first.dyn_cast<const TemplateTypeParmType *>()) {
306 auto *TTPD = dyn_cast<TemplateTypeParmDecl>(LocalPack);
307 return TTPD && TTPD->getTypeForDecl() == TTPT;
309 return declaresSameEntity(Pack.first.get<NamedDecl *>(), LocalPack);
311 if (std::find_if(LSI->LocalPacks.begin(), LSI->LocalPacks.end(),
312 DeclaresThisPack) != LSI->LocalPacks.end())
313 LambdaParamPackReferences.push_back(Pack);
316 if (LambdaParamPackReferences.empty()) {
317 // Construct in lambda only references packs declared outside the lambda.
318 // That's OK for now, but the lambda itself is considered to contain an
319 // unexpanded pack in this case, which will require expansion outside the
322 // We do not permit pack expansion that would duplicate a statement
323 // expression, not even within a lambda.
324 // FIXME: We could probably support this for statement expressions that
325 // do not contain labels.
326 // FIXME: This is insufficient to detect this problem; consider
327 // f( ({ bad: 0; }) + pack ... );
328 bool EnclosingStmtExpr = false;
329 for (unsigned N = FunctionScopes.size(); N; --N) {
330 sema::FunctionScopeInfo *Func = FunctionScopes[N-1];
332 Func->CompoundScopes.begin(), Func->CompoundScopes.end(),
333 [](sema::CompoundScopeInfo &CSI) { return CSI.IsStmtExpr; })) {
334 EnclosingStmtExpr = true;
337 // Coumpound-statements outside the lambda are OK for now; we'll check
338 // for those when we finish handling the lambda.
343 if (!EnclosingStmtExpr) {
344 LSI->ContainsUnexpandedParameterPack = true;
348 Unexpanded = LambdaParamPackReferences;
352 SmallVector<SourceLocation, 4> Locations;
353 SmallVector<IdentifierInfo *, 4> Names;
354 llvm::SmallPtrSet<IdentifierInfo *, 4> NamesKnown;
356 for (unsigned I = 0, N = Unexpanded.size(); I != N; ++I) {
357 IdentifierInfo *Name = nullptr;
358 if (const TemplateTypeParmType *TTP
359 = Unexpanded[I].first.dyn_cast<const TemplateTypeParmType *>())
360 Name = TTP->getIdentifier();
362 Name = Unexpanded[I].first.get<NamedDecl *>()->getIdentifier();
364 if (Name && NamesKnown.insert(Name).second)
365 Names.push_back(Name);
367 if (Unexpanded[I].second.isValid())
368 Locations.push_back(Unexpanded[I].second);
371 DiagnosticBuilder DB = Diag(Loc, diag::err_unexpanded_parameter_pack)
372 << (int)UPPC << (int)Names.size();
373 for (size_t I = 0, E = std::min(Names.size(), (size_t)2); I != E; ++I)
376 for (unsigned I = 0, N = Locations.size(); I != N; ++I)
377 DB << SourceRange(Locations[I]);
381 bool Sema::DiagnoseUnexpandedParameterPack(SourceLocation Loc,
383 UnexpandedParameterPackContext UPPC) {
384 // C++0x [temp.variadic]p5:
385 // An appearance of a name of a parameter pack that is not expanded is
387 if (!T->getType()->containsUnexpandedParameterPack())
390 SmallVector<UnexpandedParameterPack, 2> Unexpanded;
391 CollectUnexpandedParameterPacksVisitor(Unexpanded).TraverseTypeLoc(
393 assert(!Unexpanded.empty() && "Unable to find unexpanded parameter packs");
394 return DiagnoseUnexpandedParameterPacks(Loc, UPPC, Unexpanded);
397 bool Sema::DiagnoseUnexpandedParameterPack(Expr *E,
398 UnexpandedParameterPackContext UPPC) {
399 // C++0x [temp.variadic]p5:
400 // An appearance of a name of a parameter pack that is not expanded is
402 if (!E->containsUnexpandedParameterPack())
405 SmallVector<UnexpandedParameterPack, 2> Unexpanded;
406 CollectUnexpandedParameterPacksVisitor(Unexpanded).TraverseStmt(E);
407 assert(!Unexpanded.empty() && "Unable to find unexpanded parameter packs");
408 return DiagnoseUnexpandedParameterPacks(E->getBeginLoc(), UPPC, Unexpanded);
411 bool Sema::DiagnoseUnexpandedParameterPack(const CXXScopeSpec &SS,
412 UnexpandedParameterPackContext UPPC) {
413 // C++0x [temp.variadic]p5:
414 // An appearance of a name of a parameter pack that is not expanded is
416 if (!SS.getScopeRep() ||
417 !SS.getScopeRep()->containsUnexpandedParameterPack())
420 SmallVector<UnexpandedParameterPack, 2> Unexpanded;
421 CollectUnexpandedParameterPacksVisitor(Unexpanded)
422 .TraverseNestedNameSpecifier(SS.getScopeRep());
423 assert(!Unexpanded.empty() && "Unable to find unexpanded parameter packs");
424 return DiagnoseUnexpandedParameterPacks(SS.getRange().getBegin(),
428 bool Sema::DiagnoseUnexpandedParameterPack(const DeclarationNameInfo &NameInfo,
429 UnexpandedParameterPackContext UPPC) {
430 // C++0x [temp.variadic]p5:
431 // An appearance of a name of a parameter pack that is not expanded is
433 switch (NameInfo.getName().getNameKind()) {
434 case DeclarationName::Identifier:
435 case DeclarationName::ObjCZeroArgSelector:
436 case DeclarationName::ObjCOneArgSelector:
437 case DeclarationName::ObjCMultiArgSelector:
438 case DeclarationName::CXXOperatorName:
439 case DeclarationName::CXXLiteralOperatorName:
440 case DeclarationName::CXXUsingDirective:
441 case DeclarationName::CXXDeductionGuideName:
444 case DeclarationName::CXXConstructorName:
445 case DeclarationName::CXXDestructorName:
446 case DeclarationName::CXXConversionFunctionName:
447 // FIXME: We shouldn't need this null check!
448 if (TypeSourceInfo *TSInfo = NameInfo.getNamedTypeInfo())
449 return DiagnoseUnexpandedParameterPack(NameInfo.getLoc(), TSInfo, UPPC);
451 if (!NameInfo.getName().getCXXNameType()->containsUnexpandedParameterPack())
457 SmallVector<UnexpandedParameterPack, 2> Unexpanded;
458 CollectUnexpandedParameterPacksVisitor(Unexpanded)
459 .TraverseType(NameInfo.getName().getCXXNameType());
460 assert(!Unexpanded.empty() && "Unable to find unexpanded parameter packs");
461 return DiagnoseUnexpandedParameterPacks(NameInfo.getLoc(), UPPC, Unexpanded);
464 bool Sema::DiagnoseUnexpandedParameterPack(SourceLocation Loc,
465 TemplateName Template,
466 UnexpandedParameterPackContext UPPC) {
468 if (Template.isNull() || !Template.containsUnexpandedParameterPack())
471 SmallVector<UnexpandedParameterPack, 2> Unexpanded;
472 CollectUnexpandedParameterPacksVisitor(Unexpanded)
473 .TraverseTemplateName(Template);
474 assert(!Unexpanded.empty() && "Unable to find unexpanded parameter packs");
475 return DiagnoseUnexpandedParameterPacks(Loc, UPPC, Unexpanded);
478 bool Sema::DiagnoseUnexpandedParameterPack(TemplateArgumentLoc Arg,
479 UnexpandedParameterPackContext UPPC) {
480 if (Arg.getArgument().isNull() ||
481 !Arg.getArgument().containsUnexpandedParameterPack())
484 SmallVector<UnexpandedParameterPack, 2> Unexpanded;
485 CollectUnexpandedParameterPacksVisitor(Unexpanded)
486 .TraverseTemplateArgumentLoc(Arg);
487 assert(!Unexpanded.empty() && "Unable to find unexpanded parameter packs");
488 return DiagnoseUnexpandedParameterPacks(Arg.getLocation(), UPPC, Unexpanded);
491 void Sema::collectUnexpandedParameterPacks(TemplateArgument Arg,
492 SmallVectorImpl<UnexpandedParameterPack> &Unexpanded) {
493 CollectUnexpandedParameterPacksVisitor(Unexpanded)
494 .TraverseTemplateArgument(Arg);
497 void Sema::collectUnexpandedParameterPacks(TemplateArgumentLoc Arg,
498 SmallVectorImpl<UnexpandedParameterPack> &Unexpanded) {
499 CollectUnexpandedParameterPacksVisitor(Unexpanded)
500 .TraverseTemplateArgumentLoc(Arg);
503 void Sema::collectUnexpandedParameterPacks(QualType T,
504 SmallVectorImpl<UnexpandedParameterPack> &Unexpanded) {
505 CollectUnexpandedParameterPacksVisitor(Unexpanded).TraverseType(T);
508 void Sema::collectUnexpandedParameterPacks(TypeLoc TL,
509 SmallVectorImpl<UnexpandedParameterPack> &Unexpanded) {
510 CollectUnexpandedParameterPacksVisitor(Unexpanded).TraverseTypeLoc(TL);
513 void Sema::collectUnexpandedParameterPacks(
514 NestedNameSpecifierLoc NNS,
515 SmallVectorImpl<UnexpandedParameterPack> &Unexpanded) {
516 CollectUnexpandedParameterPacksVisitor(Unexpanded)
517 .TraverseNestedNameSpecifierLoc(NNS);
520 void Sema::collectUnexpandedParameterPacks(
521 const DeclarationNameInfo &NameInfo,
522 SmallVectorImpl<UnexpandedParameterPack> &Unexpanded) {
523 CollectUnexpandedParameterPacksVisitor(Unexpanded)
524 .TraverseDeclarationNameInfo(NameInfo);
528 ParsedTemplateArgument
529 Sema::ActOnPackExpansion(const ParsedTemplateArgument &Arg,
530 SourceLocation EllipsisLoc) {
534 switch (Arg.getKind()) {
535 case ParsedTemplateArgument::Type: {
536 TypeResult Result = ActOnPackExpansion(Arg.getAsType(), EllipsisLoc);
537 if (Result.isInvalid())
538 return ParsedTemplateArgument();
540 return ParsedTemplateArgument(Arg.getKind(), Result.get().getAsOpaquePtr(),
544 case ParsedTemplateArgument::NonType: {
545 ExprResult Result = ActOnPackExpansion(Arg.getAsExpr(), EllipsisLoc);
546 if (Result.isInvalid())
547 return ParsedTemplateArgument();
549 return ParsedTemplateArgument(Arg.getKind(), Result.get(),
553 case ParsedTemplateArgument::Template:
554 if (!Arg.getAsTemplate().get().containsUnexpandedParameterPack()) {
555 SourceRange R(Arg.getLocation());
556 if (Arg.getScopeSpec().isValid())
557 R.setBegin(Arg.getScopeSpec().getBeginLoc());
558 Diag(EllipsisLoc, diag::err_pack_expansion_without_parameter_packs)
560 return ParsedTemplateArgument();
563 return Arg.getTemplatePackExpansion(EllipsisLoc);
565 llvm_unreachable("Unhandled template argument kind?");
568 TypeResult Sema::ActOnPackExpansion(ParsedType Type,
569 SourceLocation EllipsisLoc) {
570 TypeSourceInfo *TSInfo;
571 GetTypeFromParser(Type, &TSInfo);
575 TypeSourceInfo *TSResult = CheckPackExpansion(TSInfo, EllipsisLoc, None);
579 return CreateParsedType(TSResult->getType(), TSResult);
583 Sema::CheckPackExpansion(TypeSourceInfo *Pattern, SourceLocation EllipsisLoc,
584 Optional<unsigned> NumExpansions) {
585 // Create the pack expansion type and source-location information.
586 QualType Result = CheckPackExpansion(Pattern->getType(),
587 Pattern->getTypeLoc().getSourceRange(),
588 EllipsisLoc, NumExpansions);
593 TLB.pushFullCopy(Pattern->getTypeLoc());
594 PackExpansionTypeLoc TL = TLB.push<PackExpansionTypeLoc>(Result);
595 TL.setEllipsisLoc(EllipsisLoc);
597 return TLB.getTypeSourceInfo(Context, Result);
600 QualType Sema::CheckPackExpansion(QualType Pattern, SourceRange PatternRange,
601 SourceLocation EllipsisLoc,
602 Optional<unsigned> NumExpansions) {
603 // C++11 [temp.variadic]p5:
604 // The pattern of a pack expansion shall name one or more
605 // parameter packs that are not expanded by a nested pack
608 // A pattern containing a deduced type can't occur "naturally" but arises in
609 // the desugaring of an init-capture pack.
610 if (!Pattern->containsUnexpandedParameterPack() &&
611 !Pattern->getContainedDeducedType()) {
612 Diag(EllipsisLoc, diag::err_pack_expansion_without_parameter_packs)
617 return Context.getPackExpansionType(Pattern, NumExpansions,
618 /*ExpectPackInType=*/false);
621 ExprResult Sema::ActOnPackExpansion(Expr *Pattern, SourceLocation EllipsisLoc) {
622 return CheckPackExpansion(Pattern, EllipsisLoc, None);
625 ExprResult Sema::CheckPackExpansion(Expr *Pattern, SourceLocation EllipsisLoc,
626 Optional<unsigned> NumExpansions) {
630 // C++0x [temp.variadic]p5:
631 // The pattern of a pack expansion shall name one or more
632 // parameter packs that are not expanded by a nested pack
634 if (!Pattern->containsUnexpandedParameterPack()) {
635 Diag(EllipsisLoc, diag::err_pack_expansion_without_parameter_packs)
636 << Pattern->getSourceRange();
637 CorrectDelayedTyposInExpr(Pattern);
641 // Create the pack expansion expression and source-location information.
643 PackExpansionExpr(Context.DependentTy, Pattern, EllipsisLoc, NumExpansions);
646 bool Sema::CheckParameterPacksForExpansion(
647 SourceLocation EllipsisLoc, SourceRange PatternRange,
648 ArrayRef<UnexpandedParameterPack> Unexpanded,
649 const MultiLevelTemplateArgumentList &TemplateArgs, bool &ShouldExpand,
650 bool &RetainExpansion, Optional<unsigned> &NumExpansions) {
652 RetainExpansion = false;
653 std::pair<IdentifierInfo *, SourceLocation> FirstPack;
654 bool HaveFirstPack = false;
655 Optional<unsigned> NumPartialExpansions;
656 SourceLocation PartiallySubstitutedPackLoc;
658 for (ArrayRef<UnexpandedParameterPack>::iterator i = Unexpanded.begin(),
659 end = Unexpanded.end();
661 // Compute the depth and index for this parameter pack.
662 unsigned Depth = 0, Index = 0;
663 IdentifierInfo *Name;
664 bool IsVarDeclPack = false;
666 if (const TemplateTypeParmType *TTP
667 = i->first.dyn_cast<const TemplateTypeParmType *>()) {
668 Depth = TTP->getDepth();
669 Index = TTP->getIndex();
670 Name = TTP->getIdentifier();
672 NamedDecl *ND = i->first.get<NamedDecl *>();
673 if (isa<VarDecl>(ND))
674 IsVarDeclPack = true;
676 std::tie(Depth, Index) = getDepthAndIndex(ND);
678 Name = ND->getIdentifier();
681 // Determine the size of this argument pack.
682 unsigned NewPackSize;
684 // Figure out whether we're instantiating to an argument pack or not.
685 typedef LocalInstantiationScope::DeclArgumentPack DeclArgumentPack;
687 llvm::PointerUnion<Decl *, DeclArgumentPack *> *Instantiation
688 = CurrentInstantiationScope->findInstantiationOf(
689 i->first.get<NamedDecl *>());
690 if (Instantiation->is<DeclArgumentPack *>()) {
691 // We could expand this function parameter pack.
692 NewPackSize = Instantiation->get<DeclArgumentPack *>()->size();
694 // We can't expand this function parameter pack, so we can't expand
695 // the pack expansion.
696 ShouldExpand = false;
700 // If we don't have a template argument at this depth/index, then we
701 // cannot expand the pack expansion. Make a note of this, but we still
702 // want to check any parameter packs we *do* have arguments for.
703 if (Depth >= TemplateArgs.getNumLevels() ||
704 !TemplateArgs.hasTemplateArgument(Depth, Index)) {
705 ShouldExpand = false;
709 // Determine the size of the argument pack.
710 NewPackSize = TemplateArgs(Depth, Index).pack_size();
713 // C++0x [temp.arg.explicit]p9:
714 // Template argument deduction can extend the sequence of template
715 // arguments corresponding to a template parameter pack, even when the
716 // sequence contains explicitly specified template arguments.
717 if (!IsVarDeclPack && CurrentInstantiationScope) {
718 if (NamedDecl *PartialPack
719 = CurrentInstantiationScope->getPartiallySubstitutedPack()){
720 unsigned PartialDepth, PartialIndex;
721 std::tie(PartialDepth, PartialIndex) = getDepthAndIndex(PartialPack);
722 if (PartialDepth == Depth && PartialIndex == Index) {
723 RetainExpansion = true;
724 // We don't actually know the new pack size yet.
725 NumPartialExpansions = NewPackSize;
726 PartiallySubstitutedPackLoc = i->second;
732 if (!NumExpansions) {
733 // The is the first pack we've seen for which we have an argument.
735 NumExpansions = NewPackSize;
736 FirstPack.first = Name;
737 FirstPack.second = i->second;
738 HaveFirstPack = true;
742 if (NewPackSize != *NumExpansions) {
743 // C++0x [temp.variadic]p5:
744 // All of the parameter packs expanded by a pack expansion shall have
745 // the same number of arguments specified.
747 Diag(EllipsisLoc, diag::err_pack_expansion_length_conflict)
748 << FirstPack.first << Name << *NumExpansions << NewPackSize
749 << SourceRange(FirstPack.second) << SourceRange(i->second);
751 Diag(EllipsisLoc, diag::err_pack_expansion_length_conflict_multilevel)
752 << Name << *NumExpansions << NewPackSize
753 << SourceRange(i->second);
758 // If we're performing a partial expansion but we also have a full expansion,
759 // expand to the number of common arguments. For example, given:
761 // template<typename ...T> struct A {
762 // template<typename ...U> void f(pair<T, U>...);
765 // ... a call to 'A<int, int>().f<int>' should expand the pack once and
766 // retain an expansion.
767 if (NumPartialExpansions) {
768 if (NumExpansions && *NumExpansions < *NumPartialExpansions) {
769 NamedDecl *PartialPack =
770 CurrentInstantiationScope->getPartiallySubstitutedPack();
771 Diag(EllipsisLoc, diag::err_pack_expansion_length_conflict_partial)
772 << PartialPack << *NumPartialExpansions << *NumExpansions
773 << SourceRange(PartiallySubstitutedPackLoc);
777 NumExpansions = NumPartialExpansions;
783 Optional<unsigned> Sema::getNumArgumentsInExpansion(QualType T,
784 const MultiLevelTemplateArgumentList &TemplateArgs) {
785 QualType Pattern = cast<PackExpansionType>(T)->getPattern();
786 SmallVector<UnexpandedParameterPack, 2> Unexpanded;
787 CollectUnexpandedParameterPacksVisitor(Unexpanded).TraverseType(Pattern);
789 Optional<unsigned> Result;
790 for (unsigned I = 0, N = Unexpanded.size(); I != N; ++I) {
791 // Compute the depth and index for this parameter pack.
795 if (const TemplateTypeParmType *TTP
796 = Unexpanded[I].first.dyn_cast<const TemplateTypeParmType *>()) {
797 Depth = TTP->getDepth();
798 Index = TTP->getIndex();
800 NamedDecl *ND = Unexpanded[I].first.get<NamedDecl *>();
801 if (isa<VarDecl>(ND)) {
802 // Function parameter pack or init-capture pack.
803 typedef LocalInstantiationScope::DeclArgumentPack DeclArgumentPack;
805 llvm::PointerUnion<Decl *, DeclArgumentPack *> *Instantiation
806 = CurrentInstantiationScope->findInstantiationOf(
807 Unexpanded[I].first.get<NamedDecl *>());
808 if (Instantiation->is<Decl*>())
809 // The pattern refers to an unexpanded pack. We're not ready to expand
813 unsigned Size = Instantiation->get<DeclArgumentPack *>()->size();
814 assert((!Result || *Result == Size) && "inconsistent pack sizes");
819 std::tie(Depth, Index) = getDepthAndIndex(ND);
821 if (Depth >= TemplateArgs.getNumLevels() ||
822 !TemplateArgs.hasTemplateArgument(Depth, Index))
823 // The pattern refers to an unknown template argument. We're not ready to
824 // expand this pack yet.
827 // Determine the size of the argument pack.
828 unsigned Size = TemplateArgs(Depth, Index).pack_size();
829 assert((!Result || *Result == Size) && "inconsistent pack sizes");
836 bool Sema::containsUnexpandedParameterPacks(Declarator &D) {
837 const DeclSpec &DS = D.getDeclSpec();
838 switch (DS.getTypeSpecType()) {
841 case TST_underlyingType:
843 QualType T = DS.getRepAsType().get();
844 if (!T.isNull() && T->containsUnexpandedParameterPack())
852 if (DS.getRepAsExpr() &&
853 DS.getRepAsExpr()->containsUnexpandedParameterPack())
857 case TST_unspecified:
884 case TST_decltype_auto:
886 #define GENERIC_IMAGE_TYPE(ImgType, Id) case TST_##ImgType##_t:
887 #include "clang/Basic/OpenCLImageTypes.def"
888 case TST_unknown_anytype:
893 for (unsigned I = 0, N = D.getNumTypeObjects(); I != N; ++I) {
894 const DeclaratorChunk &Chunk = D.getTypeObject(I);
895 switch (Chunk.Kind) {
896 case DeclaratorChunk::Pointer:
897 case DeclaratorChunk::Reference:
898 case DeclaratorChunk::Paren:
899 case DeclaratorChunk::Pipe:
900 case DeclaratorChunk::BlockPointer:
901 // These declarator chunks cannot contain any parameter packs.
904 case DeclaratorChunk::Array:
905 if (Chunk.Arr.NumElts &&
906 Chunk.Arr.NumElts->containsUnexpandedParameterPack())
909 case DeclaratorChunk::Function:
910 for (unsigned i = 0, e = Chunk.Fun.NumParams; i != e; ++i) {
911 ParmVarDecl *Param = cast<ParmVarDecl>(Chunk.Fun.Params[i].Param);
912 QualType ParamTy = Param->getType();
913 assert(!ParamTy.isNull() && "Couldn't parse type?");
914 if (ParamTy->containsUnexpandedParameterPack()) return true;
917 if (Chunk.Fun.getExceptionSpecType() == EST_Dynamic) {
918 for (unsigned i = 0; i != Chunk.Fun.getNumExceptions(); ++i) {
919 if (Chunk.Fun.Exceptions[i]
921 ->containsUnexpandedParameterPack())
924 } else if (isComputedNoexcept(Chunk.Fun.getExceptionSpecType()) &&
925 Chunk.Fun.NoexceptExpr->containsUnexpandedParameterPack())
928 if (Chunk.Fun.hasTrailingReturnType()) {
929 QualType T = Chunk.Fun.getTrailingReturnType().get();
930 if (!T.isNull() && T->containsUnexpandedParameterPack())
935 case DeclaratorChunk::MemberPointer:
936 if (Chunk.Mem.Scope().getScopeRep() &&
937 Chunk.Mem.Scope().getScopeRep()->containsUnexpandedParameterPack())
943 if (Expr *TRC = D.getTrailingRequiresClause())
944 if (TRC->containsUnexpandedParameterPack())
952 // Callback to only accept typo corrections that refer to parameter packs.
953 class ParameterPackValidatorCCC final : public CorrectionCandidateCallback {
955 bool ValidateCandidate(const TypoCorrection &candidate) override {
956 NamedDecl *ND = candidate.getCorrectionDecl();
957 return ND && ND->isParameterPack();
960 std::unique_ptr<CorrectionCandidateCallback> clone() override {
961 return std::make_unique<ParameterPackValidatorCCC>(*this);
967 /// Called when an expression computing the size of a parameter pack
971 /// template<typename ...Types> struct count {
972 /// static const unsigned value = sizeof...(Types);
977 /// \param OpLoc The location of the "sizeof" keyword.
978 /// \param Name The name of the parameter pack whose size will be determined.
979 /// \param NameLoc The source location of the name of the parameter pack.
980 /// \param RParenLoc The location of the closing parentheses.
981 ExprResult Sema::ActOnSizeofParameterPackExpr(Scope *S,
982 SourceLocation OpLoc,
983 IdentifierInfo &Name,
984 SourceLocation NameLoc,
985 SourceLocation RParenLoc) {
986 // C++0x [expr.sizeof]p5:
987 // The identifier in a sizeof... expression shall name a parameter pack.
988 LookupResult R(*this, &Name, NameLoc, LookupOrdinaryName);
991 NamedDecl *ParameterPack = nullptr;
992 switch (R.getResultKind()) {
993 case LookupResult::Found:
994 ParameterPack = R.getFoundDecl();
997 case LookupResult::NotFound:
998 case LookupResult::NotFoundInCurrentInstantiation: {
999 ParameterPackValidatorCCC CCC{};
1000 if (TypoCorrection Corrected =
1001 CorrectTypo(R.getLookupNameInfo(), R.getLookupKind(), S, nullptr,
1002 CCC, CTK_ErrorRecovery)) {
1003 diagnoseTypo(Corrected,
1004 PDiag(diag::err_sizeof_pack_no_pack_name_suggest) << &Name,
1005 PDiag(diag::note_parameter_pack_here));
1006 ParameterPack = Corrected.getCorrectionDecl();
1010 case LookupResult::FoundOverloaded:
1011 case LookupResult::FoundUnresolvedValue:
1014 case LookupResult::Ambiguous:
1015 DiagnoseAmbiguousLookup(R);
1019 if (!ParameterPack || !ParameterPack->isParameterPack()) {
1020 Diag(NameLoc, diag::err_sizeof_pack_no_pack_name)
1025 MarkAnyDeclReferenced(OpLoc, ParameterPack, true);
1027 return SizeOfPackExpr::Create(Context, OpLoc, ParameterPack, NameLoc,
1032 Sema::getTemplateArgumentPackExpansionPattern(
1033 TemplateArgumentLoc OrigLoc,
1034 SourceLocation &Ellipsis, Optional<unsigned> &NumExpansions) const {
1035 const TemplateArgument &Argument = OrigLoc.getArgument();
1036 assert(Argument.isPackExpansion());
1037 switch (Argument.getKind()) {
1038 case TemplateArgument::Type: {
1039 // FIXME: We shouldn't ever have to worry about missing
1040 // type-source info!
1041 TypeSourceInfo *ExpansionTSInfo = OrigLoc.getTypeSourceInfo();
1042 if (!ExpansionTSInfo)
1043 ExpansionTSInfo = Context.getTrivialTypeSourceInfo(Argument.getAsType(),
1045 PackExpansionTypeLoc Expansion =
1046 ExpansionTSInfo->getTypeLoc().castAs<PackExpansionTypeLoc>();
1047 Ellipsis = Expansion.getEllipsisLoc();
1049 TypeLoc Pattern = Expansion.getPatternLoc();
1050 NumExpansions = Expansion.getTypePtr()->getNumExpansions();
1052 // We need to copy the TypeLoc because TemplateArgumentLocs store a
1054 // FIXME: Find some way to avoid the copy?
1056 TLB.pushFullCopy(Pattern);
1057 TypeSourceInfo *PatternTSInfo =
1058 TLB.getTypeSourceInfo(Context, Pattern.getType());
1059 return TemplateArgumentLoc(TemplateArgument(Pattern.getType()),
1063 case TemplateArgument::Expression: {
1064 PackExpansionExpr *Expansion
1065 = cast<PackExpansionExpr>(Argument.getAsExpr());
1066 Expr *Pattern = Expansion->getPattern();
1067 Ellipsis = Expansion->getEllipsisLoc();
1068 NumExpansions = Expansion->getNumExpansions();
1069 return TemplateArgumentLoc(Pattern, Pattern);
1072 case TemplateArgument::TemplateExpansion:
1073 Ellipsis = OrigLoc.getTemplateEllipsisLoc();
1074 NumExpansions = Argument.getNumTemplateExpansions();
1075 return TemplateArgumentLoc(Argument.getPackExpansionPattern(),
1076 OrigLoc.getTemplateQualifierLoc(),
1077 OrigLoc.getTemplateNameLoc());
1079 case TemplateArgument::Declaration:
1080 case TemplateArgument::NullPtr:
1081 case TemplateArgument::Template:
1082 case TemplateArgument::Integral:
1083 case TemplateArgument::Pack:
1084 case TemplateArgument::Null:
1085 return TemplateArgumentLoc();
1088 llvm_unreachable("Invalid TemplateArgument Kind!");
1091 Optional<unsigned> Sema::getFullyPackExpandedSize(TemplateArgument Arg) {
1092 assert(Arg.containsUnexpandedParameterPack());
1094 // If this is a substituted pack, grab that pack. If not, we don't know
1096 // FIXME: We could find a size in more cases by looking for a substituted
1097 // pack anywhere within this argument, but that's not necessary in the common
1098 // case for 'sizeof...(A)' handling.
1099 TemplateArgument Pack;
1100 switch (Arg.getKind()) {
1101 case TemplateArgument::Type:
1102 if (auto *Subst = Arg.getAsType()->getAs<SubstTemplateTypeParmPackType>())
1103 Pack = Subst->getArgumentPack();
1108 case TemplateArgument::Expression:
1110 dyn_cast<SubstNonTypeTemplateParmPackExpr>(Arg.getAsExpr()))
1111 Pack = Subst->getArgumentPack();
1112 else if (auto *Subst = dyn_cast<FunctionParmPackExpr>(Arg.getAsExpr())) {
1113 for (VarDecl *PD : *Subst)
1114 if (PD->isParameterPack())
1116 return Subst->getNumExpansions();
1121 case TemplateArgument::Template:
1122 if (SubstTemplateTemplateParmPackStorage *Subst =
1123 Arg.getAsTemplate().getAsSubstTemplateTemplateParmPack())
1124 Pack = Subst->getArgumentPack();
1129 case TemplateArgument::Declaration:
1130 case TemplateArgument::NullPtr:
1131 case TemplateArgument::TemplateExpansion:
1132 case TemplateArgument::Integral:
1133 case TemplateArgument::Pack:
1134 case TemplateArgument::Null:
1138 // Check that no argument in the pack is itself a pack expansion.
1139 for (TemplateArgument Elem : Pack.pack_elements()) {
1140 // There's no point recursing in this case; we would have already
1141 // expanded this pack expansion into the enclosing pack if we could.
1142 if (Elem.isPackExpansion())
1145 return Pack.pack_size();
1148 static void CheckFoldOperand(Sema &S, Expr *E) {
1152 E = E->IgnoreImpCasts();
1153 auto *OCE = dyn_cast<CXXOperatorCallExpr>(E);
1154 if ((OCE && OCE->isInfixBinaryOp()) || isa<BinaryOperator>(E) ||
1155 isa<AbstractConditionalOperator>(E)) {
1156 S.Diag(E->getExprLoc(), diag::err_fold_expression_bad_operand)
1157 << E->getSourceRange()
1158 << FixItHint::CreateInsertion(E->getBeginLoc(), "(")
1159 << FixItHint::CreateInsertion(E->getEndLoc(), ")");
1163 ExprResult Sema::ActOnCXXFoldExpr(SourceLocation LParenLoc, Expr *LHS,
1164 tok::TokenKind Operator,
1165 SourceLocation EllipsisLoc, Expr *RHS,
1166 SourceLocation RParenLoc) {
1167 // LHS and RHS must be cast-expressions. We allow an arbitrary expression
1168 // in the parser and reduce down to just cast-expressions here.
1169 CheckFoldOperand(*this, LHS);
1170 CheckFoldOperand(*this, RHS);
1172 auto DiscardOperands = [&] {
1173 CorrectDelayedTyposInExpr(LHS);
1174 CorrectDelayedTyposInExpr(RHS);
1177 // [expr.prim.fold]p3:
1178 // In a binary fold, op1 and op2 shall be the same fold-operator, and
1179 // either e1 shall contain an unexpanded parameter pack or e2 shall contain
1180 // an unexpanded parameter pack, but not both.
1182 LHS->containsUnexpandedParameterPack() ==
1183 RHS->containsUnexpandedParameterPack()) {
1185 return Diag(EllipsisLoc,
1186 LHS->containsUnexpandedParameterPack()
1187 ? diag::err_fold_expression_packs_both_sides
1188 : diag::err_pack_expansion_without_parameter_packs)
1189 << LHS->getSourceRange() << RHS->getSourceRange();
1192 // [expr.prim.fold]p2:
1193 // In a unary fold, the cast-expression shall contain an unexpanded
1196 Expr *Pack = LHS ? LHS : RHS;
1197 assert(Pack && "fold expression with neither LHS nor RHS");
1199 if (!Pack->containsUnexpandedParameterPack())
1200 return Diag(EllipsisLoc, diag::err_pack_expansion_without_parameter_packs)
1201 << Pack->getSourceRange();
1204 BinaryOperatorKind Opc = ConvertTokenKindToBinaryOpcode(Operator);
1205 return BuildCXXFoldExpr(LParenLoc, LHS, Opc, EllipsisLoc, RHS, RParenLoc,
1209 ExprResult Sema::BuildCXXFoldExpr(SourceLocation LParenLoc, Expr *LHS,
1210 BinaryOperatorKind Operator,
1211 SourceLocation EllipsisLoc, Expr *RHS,
1212 SourceLocation RParenLoc,
1213 Optional<unsigned> NumExpansions) {
1214 return new (Context) CXXFoldExpr(Context.DependentTy, LParenLoc, LHS,
1215 Operator, EllipsisLoc, RHS, RParenLoc,
1219 ExprResult Sema::BuildEmptyCXXFoldExpr(SourceLocation EllipsisLoc,
1220 BinaryOperatorKind Operator) {
1221 // [temp.variadic]p9:
1222 // If N is zero for a unary fold-expression, the value of the expression is
1226 // if the operator is not listed [above], the instantiation is ill-formed.
1228 // Note that we need to use something like int() here, not merely 0, to
1229 // prevent the result from being a null pointer constant.
1230 QualType ScalarType;
1233 return ActOnCXXBoolLiteral(EllipsisLoc, tok::kw_false);
1235 return ActOnCXXBoolLiteral(EllipsisLoc, tok::kw_true);
1237 ScalarType = Context.VoidTy;
1241 return Diag(EllipsisLoc, diag::err_fold_expression_empty)
1242 << BinaryOperator::getOpcodeStr(Operator);
1245 return new (Context) CXXScalarValueInitExpr(
1246 ScalarType, Context.getTrivialTypeSourceInfo(ScalarType, EllipsisLoc),