[clang] [clang] WIP: Implement CTAD for type alias template. (PR #77890)
Haojian Wu via cfe-commits
cfe-commits at lists.llvm.org
Mon Jan 22 02:50:45 PST 2024
https://github.com/hokein updated https://github.com/llvm/llvm-project/pull/77890
>From 0f7ac82eaf79a483159351a44782c4b375f8e31b Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein.wu at gmail.com>
Date: Wed, 26 Jul 2023 09:40:12 +0200
Subject: [PATCH 1/6] [clang] WIP: Implement CTAD for type alias template.
This is a preliminary, WIP and messy implementation.
While it is still missing many pieces (see FIXMEs), it works for happy
cases.
---
clang/include/clang/Sema/Sema.h | 16 +-
clang/lib/Sema/SemaInit.cpp | 513 +++++++++++++++++-
clang/lib/Sema/SemaTemplateDeduction.cpp | 9 +
clang/lib/Sema/SemaTemplateInstantiate.cpp | 26 +-
.../lib/Sema/SemaTemplateInstantiateDecl.cpp | 17 +-
...xx1z-class-template-argument-deduction.cpp | 6 +-
clang/test/SemaCXX/cxx20-ctad-type-alias.cpp | 32 ++
7 files changed, 603 insertions(+), 16 deletions(-)
create mode 100644 clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index d0f62afdf7bb16..8fbfe3f420ec48 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -9280,6 +9280,14 @@ class Sema final {
const TemplateArgumentList &TemplateArgs,
sema::TemplateDeductionInfo &Info);
+ TemplateDeductionResult
+ DeduceTemplateArguments(TemplateParameterList *TemplateParams,
+ ArrayRef<TemplateArgument> Ps,
+ ArrayRef<TemplateArgument> As,
+ sema::TemplateDeductionInfo &Info,
+ SmallVectorImpl<DeducedTemplateArgument> &Deduced,
+ bool NumberOfArgumentsMustMatch);
+
TemplateDeductionResult SubstituteExplicitTemplateArguments(
FunctionTemplateDecl *FunctionTemplate,
TemplateArgumentListInfo &ExplicitTemplateArgs,
@@ -10432,9 +10440,11 @@ class Sema final {
SourceLocation PointOfInstantiation, FunctionDecl *Decl,
ArrayRef<TemplateArgument> TemplateArgs,
ConstraintSatisfaction &Satisfaction);
- FunctionDecl *InstantiateFunctionDeclaration(FunctionTemplateDecl *FTD,
- const TemplateArgumentList *Args,
- SourceLocation Loc);
+ FunctionDecl *InstantiateFunctionDeclaration(
+ FunctionTemplateDecl *FTD, const TemplateArgumentList *Args,
+ SourceLocation Loc,
+ CodeSynthesisContext::SynthesisKind CSC =
+ CodeSynthesisContext::ExplicitTemplateArgumentSubstitution);
void InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
FunctionDecl *Function,
bool Recursive = false,
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 91e4cb7b68a24a..177ff9cf1570b2 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -10,13 +10,17 @@
//
//===----------------------------------------------------------------------===//
+#include "TreeTransform.h"
+#include "TypeLocBuilder.h"
#include "clang/AST/ASTContext.h"
+#include "clang/AST/DeclAccessPair.h"
+#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
-#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ExprObjC.h"
#include "clang/AST/ExprOpenMP.h"
#include "clang/AST/IgnoreExpr.h"
+#include "clang/AST/Type.h"
#include "clang/AST/TypeLoc.h"
#include "clang/Basic/CharInfo.h"
#include "clang/Basic/SourceManager.h"
@@ -28,6 +32,7 @@
#include "clang/Sema/Lookup.h"
#include "clang/Sema/Ownership.h"
#include "clang/Sema/SemaInternal.h"
+#include "clang/Sema/Template.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/PointerIntPair.h"
@@ -10603,6 +10608,381 @@ static bool isOrIsDerivedFromSpecializationOf(CXXRecordDecl *RD,
return !(NotSpecialization(RD) && RD->forallBases(NotSpecialization));
}
+
+/// FIXME: this is a copy-paste from SemaTemplate.cpp
+/// Tree transform to "extract" a transformed type from a class template's
+/// constructor to a deduction guide.
+class ExtractTypeForDeductionGuide
+ : public TreeTransform<ExtractTypeForDeductionGuide> {
+ llvm::SmallVectorImpl<TypedefNameDecl *> &MaterializedTypedefs;
+
+public:
+ typedef TreeTransform<ExtractTypeForDeductionGuide> Base;
+ ExtractTypeForDeductionGuide(
+ Sema &SemaRef,
+ llvm::SmallVectorImpl<TypedefNameDecl *> &MaterializedTypedefs)
+ : Base(SemaRef), MaterializedTypedefs(MaterializedTypedefs) {}
+
+ TypeSourceInfo *transform(TypeSourceInfo *TSI) { return TransformType(TSI); }
+
+ QualType TransformTypedefType(TypeLocBuilder &TLB, TypedefTypeLoc TL) {
+ ASTContext &Context = SemaRef.getASTContext();
+ TypedefNameDecl *OrigDecl = TL.getTypedefNameDecl();
+ TypedefNameDecl *Decl = OrigDecl;
+ // Transform the underlying type of the typedef and clone the Decl only if
+ // the typedef has a dependent context.
+ if (OrigDecl->getDeclContext()->isDependentContext()) {
+ TypeLocBuilder InnerTLB;
+ QualType Transformed =
+ TransformType(InnerTLB, OrigDecl->getTypeSourceInfo()->getTypeLoc());
+ TypeSourceInfo *TSI = InnerTLB.getTypeSourceInfo(Context, Transformed);
+ if (isa<TypeAliasDecl>(OrigDecl))
+ Decl = TypeAliasDecl::Create(
+ Context, Context.getTranslationUnitDecl(), OrigDecl->getBeginLoc(),
+ OrigDecl->getLocation(), OrigDecl->getIdentifier(), TSI);
+ else {
+ assert(isa<TypedefDecl>(OrigDecl) && "Not a Type alias or typedef");
+ Decl = TypedefDecl::Create(
+ Context, Context.getTranslationUnitDecl(), OrigDecl->getBeginLoc(),
+ OrigDecl->getLocation(), OrigDecl->getIdentifier(), TSI);
+ }
+ MaterializedTypedefs.push_back(Decl);
+ }
+
+ QualType TDTy = Context.getTypedefType(Decl);
+ TypedefTypeLoc TypedefTL = TLB.push<TypedefTypeLoc>(TDTy);
+ TypedefTL.setNameLoc(TL.getNameLoc());
+
+ return TDTy;
+ }
+};
+
+// Transform to form a corresponding deduction guide for type alias template decl.
+//
+// This class implements the C++ [over.match.class.deduct]p3:
+// ... Let g denote the result of substituting these deductions into f. If
+// substitution succeeds, form a function or function template f' with the
+// following properties and add it to the set of guides of A...
+//
+// FIXME: This is a messy copy of ConvertConstructorToDeductionGuideTransform
+// in SemaTemplate.cpp with some adjustments.
+struct AliasTemplateDeductionGuideTransform {
+ AliasTemplateDeductionGuideTransform(Sema &S, TypeAliasTemplateDecl *Alias)
+ : SemaRef(S), AliasTemplate(Alias) {
+ DC = AliasTemplate->getDeclContext();
+ }
+ Sema &SemaRef;
+ TypeAliasTemplateDecl *AliasTemplate = nullptr;
+
+ DeclContext *DC = nullptr;
+
+ // FIXME: is this really needed?
+ ClassTemplateDecl *NestedPattern = nullptr;
+ // Instantiation arguments for the outermost depth-1 templates
+ // when the template is nested
+ MultiLevelTemplateArgumentList OuterInstantiationArgs;
+
+ // Returns the result of substituting the deduced template arguments into f.
+ NamedDecl *transformUnderlyingFunctionTemplate(
+ CXXDeductionGuideDecl *UnderlyingCDGD,
+ SmallVector<TemplateArgument> DeducedArgs) {
+ SmallVector<TemplateTypeParmDecl *> DeducedTemplateTypeParDecls;
+ // Add all parameters that appear in the deductions.
+ // FIXME: add template parameters of f that were not deduced.
+ for (auto D : DeducedArgs) {
+ // FIXME: fix other template argument kind.
+ if (D.getKind() != TemplateArgument::Type)
+ continue;
+ if (auto *TT =
+ dyn_cast<TemplateTypeParmType>(D.getAsType().getTypePtr())) {
+ if (TemplateTypeParmDecl *DD = TT->getDecl()) {
+ DeducedTemplateTypeParDecls.push_back(DD);
+ }
+ }
+ }
+
+ // C++ [over.match.class.deduct]p3.2:
+ // If f is a function template, f' is a function template whose template
+ // parameter list consists of all the template parameters of A (including
+ // their default template arguments) that appear in the above deductions
+ // or (recursively) in their default template arguments, followed by the
+ // template parameters of f that were not deduced (including their default
+ // template arguments)...
+ LocalInstantiationScope Scope(SemaRef);
+ SmallVector<TemplateArgument, 16> Depth1Args;
+ SmallVector<NamedDecl *, 16> AllParams;
+ SmallVector<TemplateArgument, 16> SubstArgs;
+ int Index = 0;
+ TemplateParameterList *TemplateParams = nullptr;
+
+ for (TemplateTypeParmDecl* Param : DeducedTemplateTypeParDecls) {
+ MultiLevelTemplateArgumentList Args;
+
+ Args.setKind(TemplateSubstitutionKind::Rewrite);
+ Args.addOuterTemplateArguments(Depth1Args);
+ Args.addOuterRetainedLevel();
+ NamedDecl *NewParam = transformTemplateParameter(Param, Args, Index++);
+ if (!NewParam) {
+ llvm::errs() << "Faile to generate new param!\n";
+ return nullptr;
+ }
+ auto NewArgumentForNewParam =
+ SemaRef.Context.getCanonicalTemplateArgument(
+ SemaRef.Context.getInjectedTemplateArg(NewParam));
+ Depth1Args.push_back(NewArgumentForNewParam);
+ AllParams.push_back(NewParam);
+ SubstArgs.push_back(NewArgumentForNewParam);
+ }
+ // FIXME: substitute new template parameters into the requires-clause
+
+ TemplateParams = TemplateParameterList::Create(
+ SemaRef.Context, SourceLocation(), SourceLocation(), AllParams,
+ SourceLocation(), /*requiresClause */nullptr);
+
+ MultiLevelTemplateArgumentList Args;
+ Args.setKind(TemplateSubstitutionKind::Rewrite);
+ Args.addOuterTemplateArguments(SubstArgs);
+ Args.addOuterRetainedLevel();
+
+ FunctionProtoTypeLoc FPTL = UnderlyingCDGD->getTypeSourceInfo()
+ ->getTypeLoc()
+ .getAsAdjusted<FunctionProtoTypeLoc>();
+ assert(FPTL && "no prototype for underlying deduction guides");
+
+ // Transform the type of the function, adjusting the return type and
+ // replacing references to the old parameters with references to the
+ // new ones.
+ TypeLocBuilder TLB;
+ SmallVector<ParmVarDecl*, 8> Params;
+ SmallVector<TypedefNameDecl *, 4> MaterializedTypedefs;
+ QualType NewType = transformFunctionProtoType(
+ TLB, FPTL, Params, Args, UnderlyingCDGD->getReturnType(),
+ MaterializedTypedefs);
+ if (NewType.isNull())
+ return nullptr;
+ TypeSourceInfo *NewTInfo = TLB.getTypeSourceInfo(SemaRef.Context, NewType);
+
+ return buildDeductionGuide(
+ TemplateParams, UnderlyingCDGD->getCorrespondingConstructor(),
+ UnderlyingCDGD->getExplicitSpecifier(), NewTInfo,
+ UnderlyingCDGD->getBeginLoc(), UnderlyingCDGD->getLocation(),
+ UnderlyingCDGD->getEndLoc(), UnderlyingCDGD->isImplicit(),
+ MaterializedTypedefs);
+ }
+
+private:
+ /// Transform a template parameter of underlying deduction guide into
+ /// a deduction guide template parameter, rebuilding any internal references
+ /// to earlier parameters and renumbering as we go.
+ NamedDecl *transformTemplateParameter(NamedDecl *TemplateParam,
+ MultiLevelTemplateArgumentList &Args,
+ int Index ) {
+ if (auto *TTP = dyn_cast<TemplateTypeParmDecl>(TemplateParam)) {
+ // TemplateTypeParmDecl's index cannot be changed after creation, so
+ // substitute it directly.
+ auto *NewTTP = TemplateTypeParmDecl::Create(
+ SemaRef.Context, DC, TTP->getBeginLoc(), TTP->getLocation(),
+ // FIXME: is the depth/index right?
+ TTP->getDepth(), Index,
+ TTP->getIdentifier(), TTP->wasDeclaredWithTypename(),
+ TTP->isParameterPack(), TTP->hasTypeConstraint(),
+ TTP->isExpandedParameterPack()
+ ? std::optional<unsigned>(TTP->getNumExpansionParameters())
+ : std::nullopt);
+ if (const auto *TC = TTP->getTypeConstraint())
+ SemaRef.SubstTypeConstraint(NewTTP, TC, Args,
+ /*EvaluateConstraint*/ true);
+ if (TTP->hasDefaultArgument()) {
+ TypeSourceInfo *InstantiatedDefaultArg =
+ SemaRef.SubstType(TTP->getDefaultArgumentInfo(), Args,
+ TTP->getDefaultArgumentLoc(), TTP->getDeclName());
+ if (InstantiatedDefaultArg)
+ NewTTP->setDefaultArgument(InstantiatedDefaultArg);
+ }
+ SemaRef.CurrentInstantiationScope->InstantiatedLocal(TemplateParam,
+ NewTTP);
+ return NewTTP;
+ }
+
+ if (auto *TTP = dyn_cast<TemplateTemplateParmDecl>(TemplateParam))
+ return transformTemplateParameterImpl(TTP, Args);
+
+ return transformTemplateParameterImpl(
+ cast<NonTypeTemplateParmDecl>(TemplateParam), Args);
+ }
+ template<typename TemplateParmDecl>
+ TemplateParmDecl *
+ transformTemplateParameterImpl(TemplateParmDecl *OldParam,
+ MultiLevelTemplateArgumentList &Args) {
+ // Ask the template instantiator to do the heavy lifting for us, then adjust
+ // the index of the parameter once it's done.
+ auto *NewParam =
+ cast<TemplateParmDecl>(SemaRef.SubstDecl(OldParam, DC, Args));
+ // assert(NewParam->getDepth() == OldParam->getDepth() - 1 &&
+ // "unexpected template param depth");
+ // FIXME
+ // NewParam->setPosition(NewParam->getPosition() + Depth1IndexAdjustment);
+ return NewParam;
+ }
+
+
+ QualType transformFunctionProtoType(
+ TypeLocBuilder &TLB, FunctionProtoTypeLoc TL,
+ SmallVectorImpl<ParmVarDecl *> &Params,
+ MultiLevelTemplateArgumentList &Args,
+ QualType ReturnType,
+ SmallVectorImpl<TypedefNameDecl *> &MaterializedTypedefs) {
+ SmallVector<QualType, 4> ParamTypes;
+ const FunctionProtoType *T = TL.getTypePtr();
+
+ // -- The types of the function parameters are those of the constructor.
+ for (auto *OldParam : TL.getParams()) {
+ ParmVarDecl *NewParam =
+ transformFunctionTypeParam(OldParam, Args, MaterializedTypedefs);
+ if (NestedPattern && NewParam)
+ NewParam = transformFunctionTypeParam(NewParam, OuterInstantiationArgs,
+ MaterializedTypedefs);
+ if (!NewParam)
+ return QualType();
+ ParamTypes.push_back(NewParam->getType());
+ Params.push_back(NewParam);
+ }
+
+ // The return type of the deduction guide f is InjectedClassNameType, transform
+ // it to a TemplateSpecializationType.
+ if (const auto *ET = ReturnType->getAs<InjectedClassNameType>()) {
+ ReturnType = ET->getInjectedSpecializationType();
+ }
+ auto DeductionGuideName =
+ SemaRef.Context.DeclarationNames.getCXXDeductionGuideName(
+ AliasTemplate);
+ ReturnType = SemaRef.SubstType(ReturnType, Args, SourceLocation(),
+ DeductionGuideName);
+
+ // Resolving a wording defect, we also inherit the variadicness of the
+ // constructor.
+ FunctionProtoType::ExtProtoInfo EPI;
+ EPI.Variadic = T->isVariadic();
+ EPI.HasTrailingReturn = true;
+
+ QualType FunctionTy = SemaRef.BuildFunctionType(
+ ReturnType, ParamTypes, TL.getBeginLoc(), DeductionGuideName, EPI);
+ if (FunctionTy.isNull())
+ return QualType();
+ assert(FunctionTy->getTypeClass() == Type::FunctionProto);
+ // Pushes spaces for the new FunctionProtoTypeLoc.
+ TLB.pushTrivial(SemaRef.Context,
+ TypeLoc(FunctionTy, nullptr).getNextTypeLoc().getType(),
+ SourceLocation());
+ FunctionProtoTypeLoc TargetTL = TLB.push<FunctionProtoTypeLoc>(FunctionTy);
+ TargetTL.setLocalRangeBegin(TL.getLocalRangeBegin());
+ TargetTL.setLParenLoc(TL.getLParenLoc());
+ TargetTL.setRParenLoc(TL.getRParenLoc());
+ TargetTL.setExceptionSpecRange(SourceRange());
+ TargetTL.setLocalRangeEnd(TL.getLocalRangeEnd());
+ for (unsigned I = 0, E = TargetTL.getNumParams(); I != E; ++I)
+ TargetTL.setParam(I, Params[I]);
+ return FunctionTy;
+ }
+
+ ParmVarDecl *transformFunctionTypeParam(
+ ParmVarDecl *OldParam, MultiLevelTemplateArgumentList &Args,
+ llvm::SmallVectorImpl<TypedefNameDecl *> &MaterializedTypedefs) {
+ TypeSourceInfo *OldDI = OldParam->getTypeSourceInfo();
+ TypeSourceInfo *NewDI;
+ if (auto PackTL = OldDI->getTypeLoc().getAs<PackExpansionTypeLoc>()) {
+ // Expand out the one and only element in each inner pack.
+ Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(SemaRef, 0);
+ NewDI =
+ SemaRef.SubstType(PackTL.getPatternLoc(), Args,
+ OldParam->getLocation(), OldParam->getDeclName());
+ if (!NewDI)
+ return nullptr;
+ NewDI =
+ SemaRef.CheckPackExpansion(NewDI, PackTL.getEllipsisLoc(),
+ PackTL.getTypePtr()->getNumExpansions());
+ } else
+ NewDI = SemaRef.SubstType(OldDI, Args, OldParam->getLocation(),
+ OldParam->getDeclName());
+ if (!NewDI)
+ return nullptr;
+
+ // Extract the type. This (for instance) replaces references to typedef
+ // members of the current instantiations with the definitions of those
+ // typedefs, avoiding triggering instantiation of the deduced type during
+ // deduction.
+ NewDI = ExtractTypeForDeductionGuide(SemaRef, MaterializedTypedefs)
+ .transform(NewDI);
+
+ // Resolving a wording defect, we also inherit default arguments from the
+ // constructor.
+ ExprResult NewDefArg;
+ if (OldParam->hasDefaultArg()) {
+ // We don't care what the value is (we won't use it); just create a
+ // placeholder to indicate there is a default argument.
+ QualType ParamTy = NewDI->getType();
+ NewDefArg = new (SemaRef.Context)
+ OpaqueValueExpr(OldParam->getDefaultArg()->getBeginLoc(),
+ ParamTy.getNonLValueExprType(SemaRef.Context),
+ ParamTy->isLValueReferenceType() ? VK_LValue
+ : ParamTy->isRValueReferenceType() ? VK_XValue
+ : VK_PRValue);
+ }
+
+ ParmVarDecl *NewParam = ParmVarDecl::Create(SemaRef.Context, DC,
+ OldParam->getInnerLocStart(),
+ OldParam->getLocation(),
+ OldParam->getIdentifier(),
+ NewDI->getType(),
+ NewDI,
+ OldParam->getStorageClass(),
+ NewDefArg.get());
+ NewParam->setScopeInfo(OldParam->getFunctionScopeDepth(),
+ OldParam->getFunctionScopeIndex());
+ SemaRef.CurrentInstantiationScope->InstantiatedLocal(OldParam, NewParam);
+ return NewParam;
+ }
+
+ FunctionTemplateDecl *buildDeductionGuide(
+ TemplateParameterList *TemplateParams, CXXConstructorDecl *Ctor,
+ ExplicitSpecifier ES, TypeSourceInfo *TInfo, SourceLocation LocStart,
+ SourceLocation Loc, SourceLocation LocEnd, bool IsImplicit,
+ llvm::ArrayRef<TypedefNameDecl *> MaterializedTypedefs = {}) {
+ auto DeductionGuideName =
+ SemaRef.Context.DeclarationNames.getCXXDeductionGuideName(
+ AliasTemplate);
+
+ DeclarationNameInfo Name(DeductionGuideName, Loc);
+ ArrayRef<ParmVarDecl *> Params =
+ TInfo->getTypeLoc().castAs<FunctionProtoTypeLoc>().getParams();
+
+ // Build the implicit deduction guide template.
+ auto *Guide =
+ CXXDeductionGuideDecl::Create(SemaRef.Context, DC, LocStart, ES, Name,
+ TInfo->getType(), TInfo, LocEnd, Ctor);
+ Guide->setImplicit(IsImplicit);
+ Guide->setParams(Params);
+
+ for (auto *Param : Params)
+ Param->setDeclContext(Guide);
+ for (auto *TD : MaterializedTypedefs)
+ TD->setDeclContext(Guide);
+
+ auto *GuideTemplate = FunctionTemplateDecl::Create(
+ SemaRef.Context, DC, Loc, DeductionGuideName, TemplateParams, Guide);
+ GuideTemplate->setImplicit(IsImplicit);
+ Guide->setDescribedFunctionTemplate(GuideTemplate);
+
+ if (isa<CXXRecordDecl>(DC)) {
+ Guide->setAccess(AS_public);
+ GuideTemplate->setAccess(AS_public);
+ }
+
+ DC->addDecl(GuideTemplate);
+ return GuideTemplate;
+ }
+};
+
QualType Sema::DeduceTemplateSpecializationFromInitializer(
TypeSourceInfo *TSInfo, const InitializedEntity &Entity,
const InitializationKind &Kind, MultiExprArg Inits) {
@@ -10617,6 +10997,21 @@ QualType Sema::DeduceTemplateSpecializationFromInitializer(
// We can only perform deduction for class templates.
auto *Template =
dyn_cast_or_null<ClassTemplateDecl>(TemplateName.getAsTemplateDecl());
+
+ TypeAliasTemplateDecl* AliasTemplate = nullptr;
+ if (!Template) {
+ if ((AliasTemplate = dyn_cast_or_null<TypeAliasTemplateDecl>(
+ TemplateName.getAsTemplateDecl()))) {
+ auto UnderlyingType = AliasTemplate->getTemplatedDecl()
+ ->getUnderlyingType()
+ .getDesugaredType(Context);
+ if (const auto *TST =
+ UnderlyingType->getAs<TemplateSpecializationType>()) {
+ Template = dyn_cast_or_null<ClassTemplateDecl>(
+ TST->getTemplateName().getAsTemplateDecl());
+ }
+ }
+ }
if (!Template) {
Diag(Kind.getLocation(),
diag::err_deduced_non_class_template_specialization_type)
@@ -10656,6 +11051,112 @@ QualType Sema::DeduceTemplateSpecializationFromInitializer(
// clear on this, but they're not found by name so access does not apply.
Guides.suppressDiagnostics();
+ SmallVector<DeclAccessPair> GuidesCandidates;
+ if (AliasTemplate) {
+ for (auto* Guide : Guides) {
+ if (!dyn_cast_or_null<FunctionTemplateDecl>(Guide))
+ continue;
+ auto RType = dyn_cast<FunctionTemplateDecl>(Guide)
+ ->getTemplatedDecl()
+ ->getReturnType();
+ // The (trailing) return type of the deduction guide.
+ const TemplateSpecializationType * ReturnTST = nullptr;
+ if (const auto *InjectedCNT = RType->getAs<InjectedClassNameType>()) {
+ // for implicitly-generated deduction guide.
+ ReturnTST = InjectedCNT->getInjectedTST();
+ } else if (const auto *ET = RType->getAs<ElaboratedType>()) {
+ // For explicit deduction guide.
+ ReturnTST = ET->getNamedType()->getAs<TemplateSpecializationType>();
+ }
+ assert(ReturnTST);
+ if (ReturnTST) {
+ SmallVector<DeducedTemplateArgument> DeduceResults;
+ SmallVector<TemplateArgument> DeducedArgs;
+ DeduceResults.resize(ReturnTST->template_arguments().size());
+ sema::TemplateDeductionInfo TDeduceInfo({});
+ // Deduce template arguments of the deduction guide from the RHS of
+ // the alias.
+ //
+ // C++ [over.match.class.deduct]p3: ...For each function or function
+ // template f in the guides of the template named by the
+ // simple-template-id of the defining-type-id, the template arguments
+ // of the return type of f are deduced from the defining-type-id of A
+ // according to the process in [temp.deduct.type] with the exception
+ // that deduction does not fail if not all template arguments are
+ // deduced.
+ //
+ //
+ // template<typename X, typename Y>
+ // f(X, Y) -> f<Y, X>
+ //
+ // template<typename U>
+ // using alias = f<int, U>;
+ //
+ // The RHS of alias is f<int, U>, we deduced the template arguments of
+ // the return type of the deduction guide from it: Y->int, X -> U
+ const auto* AliasRhsTST = AliasTemplate->getTemplatedDecl()
+ ->getUnderlyingType()
+ .getDesugaredType(this->Context)
+ ->getAs<TemplateSpecializationType>();
+ assert(AliasRhsTST);
+
+ if (DeduceTemplateArguments(AliasTemplate->getTemplateParameters(),
+ ReturnTST->template_arguments(),
+ AliasRhsTST->template_arguments(),
+ TDeduceInfo, DeduceResults,
+ /*NumberOfArgumentsMustMatch*/ false)) {
+ // FIXME: not all template arguments are deduced, we should continue
+ // to proceed with all deduced results.
+ } else {
+ // Happy case, all template arguments are deduced.
+ for (auto D : DeduceResults)
+ DeducedArgs.push_back(D);
+
+ auto *DeducedArgList =
+ TemplateArgumentList::CreateCopy(this->Context, DeducedArgs);
+
+ AliasTemplateDeductionGuideTransform Transform(
+ *this, AliasTemplate);
+
+ // Substitute all above deduced template arguments into the
+ // deduction guide f.
+ //
+ // FIXME: is using the InstantiateFunctionDeclaration API a right
+ // implement choice? It has some side effects which creates a
+ // specialization for the deduction guide function template, and
+ // the specialization is added to the the FunctionTemplateDecl, this
+ // is not specified by C++ standard.
+ //
+ // FIXME: Should we cache the result?
+ if (auto *K = InstantiateFunctionDeclaration(
+ dyn_cast<FunctionTemplateDecl>(Guide), DeducedArgList,
+ SourceLocation(),
+ Sema::CodeSynthesisContext::BuildingDeductionGuides)) {
+ InstantiatingTemplate BuildingDeductionGuides(
+ *this, SourceLocation(), AliasTemplate,
+ Sema::InstantiatingTemplate::BuildingDeductionGuidesTag{});
+ auto *D = Transform.transformUnderlyingFunctionTemplate(
+ dyn_cast<CXXDeductionGuideDecl>(K), DeducedArgs);
+ // FIXME: implement the assoicated constraint per C++
+ // [over.match.class.deduct]p3.3:
+ // The associated constraints ([temp.constr.decl]) are the
+ // conjunction of the associated constraints of g and a
+ // constraint that is satisfied if and only if the arguments of
+ // A are deducible (see below) from the return type.
+ // This could be implemented as part of function overload
+ // resolution below.
+ GuidesCandidates.push_back(
+ DeclAccessPair::make(D, AccessSpecifier::AS_public));
+ }
+ }
+ }
+ }
+ }
+ else {
+ for (auto I = Guides.begin(), E = Guides.end(); I != E; ++I) {
+ GuidesCandidates.push_back(I.getPair());
+ }
+ }
// Figure out if this is list-initialization.
InitListExpr *ListInit =
(Inits.size() == 1 && Kind.getKind() != InitializationKind::IK_Direct)
@@ -10813,9 +11314,8 @@ QualType Sema::DeduceTemplateSpecializationFromInitializer(
HasAnyDeductionGuide = true;
}
};
-
- for (auto I = Guides.begin(), E = Guides.end(); I != E; ++I) {
- NamedDecl *D = (*I)->getUnderlyingDecl();
+ for (auto I : GuidesCandidates) {
+ NamedDecl *D = (I)->getUnderlyingDecl();
if (D->isInvalidDecl())
continue;
@@ -10828,7 +11328,7 @@ QualType Sema::DeduceTemplateSpecializationFromInitializer(
if (!GD->isImplicit())
HasAnyDeductionGuide = true;
- addDeductionCandidate(TD, GD, I.getPair(), OnlyListConstructors,
+ addDeductionCandidate(TD, GD, I, OnlyListConstructors,
/*AllowAggregateDeductionCandidate=*/false);
}
@@ -10868,7 +11368,8 @@ QualType Sema::DeduceTemplateSpecializationFromInitializer(
// Try list constructors unless the list is empty and the class has one or
// more default constructors, in which case those constructors win.
if (!ListInit->getNumInits()) {
- for (NamedDecl *D : Guides) {
+ for (auto D : GuidesCandidates) {
+
auto *FD = dyn_cast<FunctionDecl>(D->getUnderlyingDecl());
if (FD && FD->getMinRequiredArguments() == 0) {
TryListConstructors = false;
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index e9e7ab5bb6698a..5bd065aae45ee9 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -2484,6 +2484,15 @@ DeduceTemplateArguments(Sema &S, TemplateParameterList *TemplateParams,
return Sema::TDK_Success;
}
+Sema::TemplateDeductionResult Sema::DeduceTemplateArguments(
+ TemplateParameterList *TemplateParams, ArrayRef<TemplateArgument> Ps,
+ ArrayRef<TemplateArgument> As, sema::TemplateDeductionInfo &Info,
+ SmallVectorImpl<DeducedTemplateArgument> &Deduced,
+ bool NumberOfArgumentsMustMatch) {
+ return ::DeduceTemplateArguments(*this, TemplateParams, Ps, As, Info, Deduced,
+ NumberOfArgumentsMustMatch);
+}
+
static Sema::TemplateDeductionResult
DeduceTemplateArguments(Sema &S, TemplateParameterList *TemplateParams,
const TemplateArgumentList &ParamList,
diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index e12186d7d82f8d..2c304c3193893a 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -21,6 +21,7 @@
#include "clang/AST/ExprConcepts.h"
#include "clang/AST/PrettyDeclStackTrace.h"
#include "clang/AST/Type.h"
+#include "clang/AST/TypeLoc.h"
#include "clang/AST/TypeVisitor.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/Stack.h"
@@ -521,7 +522,8 @@ Sema::InstantiatingTemplate::InstantiatingTemplate(
TemplateArgs, &DeductionInfo) {
assert(
Kind == CodeSynthesisContext::ExplicitTemplateArgumentSubstitution ||
- Kind == CodeSynthesisContext::DeducedTemplateArgumentSubstitution);
+ Kind == CodeSynthesisContext::DeducedTemplateArgumentSubstitution ||
+ Kind == CodeSynthesisContext::BuildingDeductionGuides);
}
Sema::InstantiatingTemplate::InstantiatingTemplate(
@@ -1418,6 +1420,28 @@ namespace {
return inherited::TransformFunctionProtoType(TLB, TL);
}
+ QualType TransformInjectedClassNameType(TypeLocBuilder &TLB,
+ InjectedClassNameTypeLoc TL) {
+ // Return a TemplateSpecializationType for building deduction guides
+ Decl *D = TransformDecl(TL.getNameLoc(),
+ TL.getTypePtr()->getDecl());
+ if (!D) {
+ if (SemaRef.CodeSynthesisContexts.back().Kind !=
+ Sema::CodeSynthesisContext::BuildingDeductionGuides)
+ return QualType();
+ auto *ICT = TL.getType()->getAs<InjectedClassNameType>();
+ auto TST = SemaRef.Context.getTemplateSpecializationType(
+ ICT->getTemplateName(), TemplateArgs.getOutermost());
+ TLB.pushTrivial(SemaRef.Context, TST, {});
+ return TST;
+ }
+
+ // Default implementation.
+ QualType T = SemaRef.Context.getTypeDeclType(cast<TypeDecl>(D));
+ TLB.pushTypeSpec(T).setNameLoc(TL.getNameLoc());
+ return T;
+ }
+
template<typename Fn>
QualType TransformFunctionProtoType(TypeLocBuilder &TLB,
FunctionProtoTypeLoc TL,
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index fbc8572ea0e0f0..ed57bf23668c5f 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -4857,13 +4857,13 @@ bool TemplateDeclInstantiator::SubstDefaultedFunction(FunctionDecl *New,
FunctionDecl *
Sema::InstantiateFunctionDeclaration(FunctionTemplateDecl *FTD,
const TemplateArgumentList *Args,
- SourceLocation Loc) {
+ SourceLocation Loc, CodeSynthesisContext::SynthesisKind CSC) {
FunctionDecl *FD = FTD->getTemplatedDecl();
sema::TemplateDeductionInfo Info(Loc);
InstantiatingTemplate Inst(
*this, Loc, FTD, Args->asArray(),
- CodeSynthesisContext::ExplicitTemplateArgumentSubstitution, Info);
+ CSC, Info);
if (Inst.isInvalid())
return nullptr;
@@ -6284,7 +6284,18 @@ NamedDecl *Sema::FindInstantiatedDecl(SourceLocation Loc, NamedDecl *D,
QualType T = CheckTemplateIdType(TemplateName(TD), Loc, Args);
if (T.isNull())
return nullptr;
- auto *SubstRecord = T->getAsCXXRecordDecl();
+ CXXRecordDecl *SubstRecord = T->getAsCXXRecordDecl();
+
+ if (!SubstRecord) {
+ // FIXME: we encounter a new type here as we use the
+ // `InstantiateFunctionDeclaration` API to substitute the deduced
+ // template arguments into deduction guide.
+ if (auto TST = T->getAs<TemplateSpecializationType>())
+ // Return a nullptr as a sentinel value, we handle it properly in
+ // the TemplateInstantiator::TransformInjectedClassNameType
+ // override.
+ return nullptr;
+ }
assert(SubstRecord && "class template id not a class type?");
// Check that this template-id names the primary template and not a
// partial or explicit specialization. (In the latter cases, it's
diff --git a/clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp b/clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
index 33ed4295c2e48c..2f067ea53a5029 100644
--- a/clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
+++ b/clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
@@ -101,13 +101,13 @@ namespace dependent {
struct B {
template<typename T> struct X { X(T); };
X(int) -> X<int>;
- template<typename T> using Y = X<T>; // expected-note {{template}}
+ template<typename T> using Y = X<T>;
};
template<typename T> void f() {
typename T::X tx = 0;
- typename T::Y ty = 0; // expected-error {{alias template 'Y' requires template arguments; argument deduction only allowed for class templates}}
+ typename T::Y ty = 0;
}
- template void f<B>(); // expected-note {{in instantiation of}}
+ template void f<B>();
template<typename T> struct C { C(T); };
template<typename T> C(T) -> C<T>;
diff --git a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
new file mode 100644
index 00000000000000..6a78e7aa082954
--- /dev/null
+++ b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -fsyntax-only -Wno-c++11-narrowing -Wno-literal-conversion -std=c++20 -verify %s
+// expected-no-diagnostics
+
+template<typename T>
+struct Foo {
+ T t;
+};
+
+template<typename U>
+using Bar = Foo<U>;
+
+void test1() {
+ Bar s = {1};
+}
+
+template<typename X, typename Y>
+struct XYpair {
+ X x;
+ Y y;
+};
+// A tricky explicit deduction guide that swapping X and Y.
+template<typename X, typename Y>
+XYpair(X, Y) -> XYpair<Y, X>;
+template<typename U, typename V>
+using AliasXYpair = XYpair<U, V>;
+
+void test2() {
+ AliasXYpair xy = {1.1, 2}; // XYpair<int, double>
+
+ static_assert(__is_same(decltype(xy.x), int));
+ static_assert(__is_same(decltype(xy.y), double));
+}
>From 7dc6dbdbac880b4560f9d28adc7979d4262d3118 Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein.wu at gmail.com>
Date: Fri, 19 Jan 2024 14:46:24 +0100
Subject: [PATCH 2/6] Fix an assert hit with default arguments.
---
clang/lib/Sema/SemaInit.cpp | 14 +++++++++-----
clang/test/SemaCXX/cxx20-ctad-type-alias.cpp | 11 +++++++++++
2 files changed, 20 insertions(+), 5 deletions(-)
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 177ff9cf1570b2..23f4d7b5acf85a 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -10922,11 +10922,15 @@ struct AliasTemplateDeductionGuideTransform {
// placeholder to indicate there is a default argument.
QualType ParamTy = NewDI->getType();
NewDefArg = new (SemaRef.Context)
- OpaqueValueExpr(OldParam->getDefaultArg()->getBeginLoc(),
- ParamTy.getNonLValueExprType(SemaRef.Context),
- ParamTy->isLValueReferenceType() ? VK_LValue
- : ParamTy->isRValueReferenceType() ? VK_XValue
- : VK_PRValue);
+ // FIXME: using getDefaultArg will crash hitting "Default argument is
+ // not yet instantiated!" erro, fixed in constructor transformer as
+ // well.
+ OpaqueValueExpr(
+ OldParam->getDefaultArgRange().getBegin(),
+ ParamTy.getNonLValueExprType(SemaRef.Context),
+ ParamTy->isLValueReferenceType() ? VK_LValue
+ : ParamTy->isRValueReferenceType() ? VK_XValue
+ : VK_PRValue);
}
ParmVarDecl *NewParam = ParmVarDecl::Create(SemaRef.Context, DC,
diff --git a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
index 6a78e7aa082954..4202e60e714b37 100644
--- a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
+++ b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
@@ -30,3 +30,14 @@ void test2() {
static_assert(__is_same(decltype(xy.x), int));
static_assert(__is_same(decltype(xy.y), double));
}
+
+namespace test3 {
+template<typename T, class>
+struct container {
+ // test with default arguments.
+ container(T a , T b = T());
+};
+
+template<class T> using vector = container<T, int>;
+vector v(0, 0);
+} // namespace test3
\ No newline at end of file
>From df112cc322364d1ab735ae0b73a02f1ab22d27cd Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein.wu at gmail.com>
Date: Fri, 19 Jan 2024 16:46:11 +0100
Subject: [PATCH 3/6] Add a failing testcase where the template arguments of
the return type f fail to be deduced from the rhs of the type alias.
This is a FIXME for implementing "If deduction fails for another reason, proceed with an empty set of deduced template arguments."
---
clang/test/SemaCXX/cxx20-ctad-type-alias.cpp | 24 +++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
diff --git a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
index 4202e60e714b37..103620f037b3b6 100644
--- a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
+++ b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
@@ -40,4 +40,26 @@ struct container {
template<class T> using vector = container<T, int>;
vector v(0, 0);
-} // namespace test3
\ No newline at end of file
+} // namespace test3
+
+
+namespace test4 {
+template<class T>
+struct X
+{
+ T t;
+ X(T) {}
+};
+
+template <class T>
+X(T) -> X<double>;
+
+template <class T>
+using AX = X<T>;
+
+void test1() {
+ AX s = {1};
+ // FIXME: should select X<double> deduction guide
+ // static_assert(__is_same(decltype(s.t), double));
+}
+}
\ No newline at end of file
>From e306d498c22afab090e4611fafd049a1e3b84e99 Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein.wu at gmail.com>
Date: Sat, 20 Jan 2024 21:22:49 +0100
Subject: [PATCH 4/6] Handle cases where the RHS of type alias is not a
template specialization type.
---
clang/lib/Sema/SemaInit.cpp | 27 +++++++++++++-------
clang/test/SemaCXX/cxx20-ctad-type-alias.cpp | 10 +++++++-
2 files changed, 27 insertions(+), 10 deletions(-)
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 23f4d7b5acf85a..ee4cfe35e9fd1a 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -34,6 +34,7 @@
#include "clang/Sema/SemaInternal.h"
#include "clang/Sema/Template.h"
#include "llvm/ADT/APInt.h"
+#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/SmallString.h"
@@ -11003,16 +11004,29 @@ QualType Sema::DeduceTemplateSpecializationFromInitializer(
dyn_cast_or_null<ClassTemplateDecl>(TemplateName.getAsTemplateDecl());
TypeAliasTemplateDecl* AliasTemplate = nullptr;
+ llvm::ArrayRef<TemplateArgument> AliasRhsTemplateArgs;
if (!Template) {
- if ((AliasTemplate = dyn_cast_or_null<TypeAliasTemplateDecl>(
- TemplateName.getAsTemplateDecl()))) {
+ if (AliasTemplate = dyn_cast_or_null<TypeAliasTemplateDecl>(
+ TemplateName.getAsTemplateDecl()); AliasTemplate) {
+ llvm::errs() << "alias template decl\n";
auto UnderlyingType = AliasTemplate->getTemplatedDecl()
->getUnderlyingType()
.getDesugaredType(Context);
if (const auto *TST =
UnderlyingType->getAs<TemplateSpecializationType>()) {
+ // normal cases: using AliasFoo = Foo<T, U>;
Template = dyn_cast_or_null<ClassTemplateDecl>(
TST->getTemplateName().getAsTemplateDecl());
+ AliasRhsTemplateArgs = TST->template_arguments();
+ } else if (const auto *RT = UnderlyingType->getAs<RecordType>()) {
+ // cases where template arguments in the RHS of the alias are not
+ // dependent. e.g.
+ // using AliasFoo = Foo<bool>;
+ if (const auto *CTSD = llvm::dyn_cast<ClassTemplateSpecializationDecl>(
+ RT->getAsCXXRecordDecl())) {
+ Template = CTSD->getSpecializedTemplate();
+ AliasRhsTemplateArgs = CTSD->getTemplateArgs().asArray();
+ }
}
}
}
@@ -11098,15 +11112,10 @@ QualType Sema::DeduceTemplateSpecializationFromInitializer(
//
// The RHS of alias is f<int, U>, we deduced the template arguments of
// the return type of the deduction guide from it: Y->int, X -> U
- const auto* AliasRhsTST = AliasTemplate->getTemplatedDecl()
- ->getUnderlyingType()
- .getDesugaredType(this->Context)
- ->getAs<TemplateSpecializationType>();
- assert(AliasRhsTST);
-
if (DeduceTemplateArguments(AliasTemplate->getTemplateParameters(),
ReturnTST->template_arguments(),
- AliasRhsTST->template_arguments(),
+ //AliasRhsTST->template_arguments(),
+ AliasRhsTemplateArgs,
TDeduceInfo, DeduceResults,
/*NumberOfArgumentsMustMatch*/ false)) {
// FIXME: not all template arguments are deduced, we should continue
diff --git a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
index 103620f037b3b6..72531f3399877d 100644
--- a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
+++ b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
@@ -62,4 +62,12 @@ void test1() {
// FIXME: should select X<double> deduction guide
// static_assert(__is_same(decltype(s.t), double));
}
-}
\ No newline at end of file
+}
+
+namespace test5 {
+template<int B>
+struct Foo {};
+template<int... C>
+using AF = Foo<1>;
+auto a = AF {};
+}
>From 8a0bb177a8b42b84242049ceea62ab143000e50a Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein.wu at gmail.com>
Date: Sat, 20 Jan 2024 23:27:10 +0100
Subject: [PATCH 5/6] Fix an assertion crash when substitute deduced tempalte
arguments into the deduction guide f.
We tried to build a ConstantExpr on a ConstantExpr, which triggers the
assertion in the ConstantExpr::Create method.
---
clang/lib/Sema/SemaOverload.cpp | 1 +
clang/test/SemaCXX/cxx20-ctad-type-alias.cpp | 11 +++++++++++
2 files changed, 12 insertions(+)
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 030878899b8122..c461b9cb3574bb 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -40,6 +40,7 @@
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/Casting.h"
+#include "llvm/Support/Signals.h"
#include <algorithm>
#include <cstddef>
#include <cstdlib>
diff --git a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
index 72531f3399877d..f00d414888a51f 100644
--- a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
+++ b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
@@ -71,3 +71,14 @@ template<int... C>
using AF = Foo<1>;
auto a = AF {};
}
+
+namespace test6 {
+template<typename T, bool B = false>
+struct Foo {
+ Foo(T);
+};
+// non-type template argument.
+template<typename T>
+using AF = Foo<T, 1>;
+AF b{0};//
+}
>From a4b028d69e9b668a38cae62c6162038a53b339b2 Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein.wu at gmail.com>
Date: Mon, 22 Jan 2024 10:50:29 +0100
Subject: [PATCH 6/6] Add a unsupported testcase.
The implementations doesn't support the using-alias-chain usage at the moment.
Tweak the implementation not crashing, and add a testcase for this
---
clang/lib/Sema/SemaInit.cpp | 20 ++++++++++++++------
clang/test/SemaCXX/cxx20-ctad-type-alias.cpp | 14 +++++++++++++-
2 files changed, 27 insertions(+), 7 deletions(-)
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index ee4cfe35e9fd1a..a54b792c49c455 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -11008,17 +11008,25 @@ QualType Sema::DeduceTemplateSpecializationFromInitializer(
if (!Template) {
if (AliasTemplate = dyn_cast_or_null<TypeAliasTemplateDecl>(
TemplateName.getAsTemplateDecl()); AliasTemplate) {
- llvm::errs() << "alias template decl\n";
- auto UnderlyingType = AliasTemplate->getTemplatedDecl()
+ // Unrap the sugar ElaboratedType.
+ auto RhsType = AliasTemplate->getTemplatedDecl()
->getUnderlyingType()
- .getDesugaredType(Context);
+ .getSingleStepDesugaredType(Context);
if (const auto *TST =
- UnderlyingType->getAs<TemplateSpecializationType>()) {
- // normal cases: using AliasFoo = Foo<T, U>;
+ RhsType->getAs<TemplateSpecializationType>()) {
+ // The template decl in the TST can be a TypeALiasTemplateDecl if
+ // the right hand side of the alias is a type alias as well. E.g.
+ //
+ // template<typename T>
+ // using AliasFoo1 = Foo<T>; // Foo<T> is a class template specialization
+ //
+ // template<typename T>
+ // using AliasFoo2 = AliasFoo1<T>; // AliasFoo1<T> is a type alias
+ // FIXME: handle this case, we need to recursively perform deductions.
Template = dyn_cast_or_null<ClassTemplateDecl>(
TST->getTemplateName().getAsTemplateDecl());
AliasRhsTemplateArgs = TST->template_arguments();
- } else if (const auto *RT = UnderlyingType->getAs<RecordType>()) {
+ } else if (const auto *RT = RhsType->getAs<RecordType>()) {
// cases where template arguments in the RHS of the alias are not
// dependent. e.g.
// using AliasFoo = Foo<bool>;
diff --git a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
index f00d414888a51f..24cadcb75150a4 100644
--- a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
+++ b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
@@ -1,5 +1,4 @@
// RUN: %clang_cc1 -fsyntax-only -Wno-c++11-narrowing -Wno-literal-conversion -std=c++20 -verify %s
-// expected-no-diagnostics
template<typename T>
struct Foo {
@@ -82,3 +81,16 @@ template<typename T>
using AF = Foo<T, 1>;
AF b{0};//
}
+
+namespace test7 {
+
+template<typename T>
+struct Foo { Foo(T); };
+
+template<typename U>
+using AF1 = Foo<U>;
+template<typename K>
+using AF2 = AF1<K>; // expected-note {{template is declared here}}
+// FIXME: support this case.
+AF2 b = 1; // expected-error {{alias template 'AF2' requires template arguments; argument deduction only allowed for class templates}}
+}
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