[clang] [clang] CTAD: Generate deduction guides for alias templates from non-template explicit deduction guides (PR #96686)
Haojian Wu via cfe-commits
cfe-commits at lists.llvm.org
Mon Jul 8 05:22:09 PDT 2024
https://github.com/hokein updated https://github.com/llvm/llvm-project/pull/96686
>From c835f5acbcb9c768c525df835d09fbe301edd197 Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein.wu at gmail.com>
Date: Tue, 25 Jun 2024 10:16:54 +0200
Subject: [PATCH 1/2] [clang] CTAD: Fix deduction guides for alias are not
generated from non-template explicit deduction guides.
---
clang/lib/Sema/SemaTemplate.cpp | 64 +++++++++++++++++---
clang/test/SemaCXX/cxx20-ctad-type-alias.cpp | 41 +++++++++++++
2 files changed, 97 insertions(+), 8 deletions(-)
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 07b3f793b3a29d..5fac68fb10617a 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -2220,8 +2220,12 @@ class ExtractTypeForDeductionGuide
}
};
-// Build a deduction guide with the specified parameter types.
-FunctionTemplateDecl *buildDeductionGuide(
+// Build a deduction guide using the provided information.
+//
+// A deduction guide can be either a template or a non-template function
+// declaration. If \p TemplateParams is null, a non-template function
+// declaration will be created.
+NamedDecl *buildDeductionGuide(
Sema &SemaRef, TemplateDecl *OriginalTemplate,
TemplateParameterList *TemplateParams, CXXConstructorDecl *Ctor,
ExplicitSpecifier ES, TypeSourceInfo *TInfo, SourceLocation LocStart,
@@ -2247,16 +2251,21 @@ FunctionTemplateDecl *buildDeductionGuide(
Param->setDeclContext(Guide);
for (auto *TD : MaterializedTypedefs)
TD->setDeclContext(Guide);
+ if (isa<CXXRecordDecl>(DC))
+ Guide->setAccess(AS_public);
+
+ if (!TemplateParams) {
+ DC->addDecl(Guide);
+ return 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);
+ if (isa<CXXRecordDecl>(DC))
GuideTemplate->setAccess(AS_public);
- }
DC->addDecl(GuideTemplate);
return GuideTemplate;
@@ -2898,7 +2907,8 @@ Expr *buildIsDeducibleConstraint(Sema &SemaRef,
ASTContext &Context = SemaRef.Context;
// Constraint AST nodes must use uninstantiated depth.
if (auto *PrimaryTemplate =
- AliasTemplate->getInstantiatedFromMemberTemplate()) {
+ AliasTemplate->getInstantiatedFromMemberTemplate();
+ PrimaryTemplate && TemplateParams.size() > 0) {
LocalInstantiationScope Scope(SemaRef);
// Adjust the depth for TemplateParams.
@@ -3162,12 +3172,12 @@ BuildDeductionGuideForTypeAlias(Sema &SemaRef,
FPrimeTemplateParams,
AliasTemplate->getTemplateParameters()->getRAngleLoc(),
/*RequiresClause=*/RequiresClause);
- FunctionTemplateDecl *Result = buildDeductionGuide(
+ auto *Result = cast<FunctionTemplateDecl>(buildDeductionGuide(
SemaRef, AliasTemplate, FPrimeTemplateParamList,
GG->getCorrespondingConstructor(), GG->getExplicitSpecifier(),
GG->getTypeSourceInfo(), AliasTemplate->getBeginLoc(),
AliasTemplate->getLocation(), AliasTemplate->getEndLoc(),
- F->isImplicit());
+ F->isImplicit()));
cast<CXXDeductionGuideDecl>(Result->getTemplatedDecl())
->setDeductionCandidateKind(GG->getDeductionCandidateKind());
return Result;
@@ -3198,6 +3208,44 @@ void DeclareImplicitDeductionGuidesForTypeAlias(
Guides.suppressDiagnostics();
for (auto *G : Guides) {
+ if (auto *DG = dyn_cast<CXXDeductionGuideDecl>(G)) {
+ // The deduction guide is a non-template function decl, we just clone it.
+ auto *FunctionType =
+ SemaRef.Context.getTrivialTypeSourceInfo(DG->getType());
+ FunctionProtoTypeLoc FPTL =
+ FunctionType->getTypeLoc().castAs<FunctionProtoTypeLoc>();
+
+ // Clone the parameters.
+ unsigned ProcessedParamIndex = 0;
+ for (auto *P : DG->parameters()) {
+ auto *TSI = SemaRef.Context.getTrivialTypeSourceInfo(P->getType());
+ ParmVarDecl *NewParam = ParmVarDecl::Create(
+ SemaRef.Context, G->getDeclContext(), P->getBeginLoc(),
+ P->getLocation(), nullptr, TSI->getType(), TSI, SC_None, nullptr);
+ NewParam->setScopeInfo(0, ProcessedParamIndex);
+ FPTL.setParam(ProcessedParamIndex, NewParam);
+ ProcessedParamIndex++;
+ }
+ auto *Transformed = cast<FunctionDecl>(buildDeductionGuide(
+ SemaRef, AliasTemplate, /*TemplateParams=*/nullptr,
+ /*Constructor=*/nullptr, DG->getExplicitSpecifier(), FunctionType,
+ AliasTemplate->getBeginLoc(), AliasTemplate->getLocation(),
+ AliasTemplate->getEndLoc(), DG->isImplicit()));
+
+ // FIXME: Here the synthesized deduction guide is not a templated function.
+ // Per [dcl.decl]p4, the requires-clause shall be present only if the
+ // declarator declares a templated function, a bug in standard?
+ auto *Constraint = buildIsDeducibleConstraint(
+ SemaRef, AliasTemplate, Transformed->getReturnType(), {});
+ if (auto *RC = DG->getTrailingRequiresClause()) {
+ auto Conjunction =
+ SemaRef.BuildBinOp(SemaRef.getCurScope(), SourceLocation{},
+ BinaryOperatorKind::BO_LAnd, RC, Constraint);
+ if (!Conjunction.isInvalid())
+ Constraint = Conjunction.getAs<Expr>();
+ }
+ Transformed->setTrailingRequiresClause(Constraint);
+ }
FunctionTemplateDecl *F = dyn_cast<FunctionTemplateDecl>(G);
if (!F)
continue;
diff --git a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
index a369ce687a728e..2193be03ad9a3e 100644
--- a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
+++ b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
@@ -440,3 +440,44 @@ template<typename...TS>
using AA = A<int, TS...>;
AA a{0};
}
+
+namespace GH94927 {
+template <typename T>
+struct A {
+ A(T);
+};
+A(int) -> A<char>;
+
+template <typename U>
+using B1 = A<U>;
+B1 b1(100); // deduce to A<char>;
+static_assert(__is_same(decltype(b1), A<char>));
+
+template <typename U>
+requires (!__is_same(U, char)) // filter out the explicit deduction guide.
+using B2 = A<U>;
+template <typename V>
+using B3 = B2<V>;
+
+B2 b2(100); // deduced to A<int>;
+static_assert(__is_same(decltype(b2), A<int>));
+B3 b3(100); // decuded to A<int>;
+static_assert(__is_same(decltype(b3), A<int>));
+
+
+// the nested case
+template <typename T1>
+struct Out {
+ template <typename T2>
+ struct A {
+ A(T2);
+ };
+ A(int) -> A<T1>;
+
+ template <typename T3>
+ using B = A<T3>;
+};
+
+Out<float>::B out(100); // deduced to Out<float>::A<float>;
+static_assert(__is_same(decltype(out), Out<float>::A<float>));
+}
>From 240a56717440df2f857b5aa2fc556ffc3ce4adca Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein.wu at gmail.com>
Date: Mon, 8 Jul 2024 14:21:36 +0200
Subject: [PATCH 2/2] Fix a nit
---
clang/lib/Sema/SemaTemplate.cpp | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 5fac68fb10617a..55ecddcfa4074b 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -3216,15 +3216,14 @@ void DeclareImplicitDeductionGuidesForTypeAlias(
FunctionType->getTypeLoc().castAs<FunctionProtoTypeLoc>();
// Clone the parameters.
- unsigned ProcessedParamIndex = 0;
- for (auto *P : DG->parameters()) {
+ for (unsigned I = 0, N = DG->getNumParams(); I != N; ++I) {
+ const auto* P = DG->getParamDecl(I);
auto *TSI = SemaRef.Context.getTrivialTypeSourceInfo(P->getType());
ParmVarDecl *NewParam = ParmVarDecl::Create(
- SemaRef.Context, G->getDeclContext(), P->getBeginLoc(),
+ SemaRef.Context, G->getDeclContext(), DG->getParamDecl(I)->getBeginLoc(),
P->getLocation(), nullptr, TSI->getType(), TSI, SC_None, nullptr);
- NewParam->setScopeInfo(0, ProcessedParamIndex);
- FPTL.setParam(ProcessedParamIndex, NewParam);
- ProcessedParamIndex++;
+ NewParam->setScopeInfo(0, I);
+ FPTL.setParam(I, NewParam);
}
auto *Transformed = cast<FunctionDecl>(buildDeductionGuide(
SemaRef, AliasTemplate, /*TemplateParams=*/nullptr,
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