https://github.com/hokein updated
https://github.com/llvm/llvm-project/pull/125478
>From 4af8e1985c4882e1083cd522eb955f69066bd15e Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein...@gmail.com>
Date: Mon, 3 Feb 2025 11:55:17 +0100
Subject: [PATCH 1/3] [clang] CTAD alias: Respecte explicit deduction guides
defined after the first use of the alias template.
---
clang/lib/Sema/SemaTemplateDeductionGuide.cpp | 33 ++++++++++++++-----
clang/test/SemaCXX/cxx20-ctad-type-alias.cpp | 13 ++++++--
2 files changed, 36 insertions(+), 10 deletions(-)
diff --git a/clang/lib/Sema/SemaTemplateDeductionGuide.cpp
b/clang/lib/Sema/SemaTemplateDeductionGuide.cpp
index 0d079677eecc568..f5884f964d6fbd5 100644
--- a/clang/lib/Sema/SemaTemplateDeductionGuide.cpp
+++ b/clang/lib/Sema/SemaTemplateDeductionGuide.cpp
@@ -740,6 +740,24 @@ bool hasDeclaredDeductionGuides(DeclarationName Name,
DeclContext *DC) {
return false;
}
+// Returns all source deduction guides associated with the declared
+// deduction guides that have the specified deduction guide name.
+llvm::DenseSet<const NamedDecl *> getSourceDeductionGuides(DeclarationName
Name,
+ DeclContext *DC) {
+ assert(Name.getNameKind() ==
+ DeclarationName::NameKind::CXXDeductionGuideName &&
+ "name must be a deduction guide name");
+ llvm::DenseSet<const NamedDecl *> Result;
+ for (auto *D : DC->lookup(Name)) {
+ if (const auto *FTD = dyn_cast<FunctionTemplateDecl>(D))
+ D = FTD->getTemplatedDecl();
+
+ if (const auto *GD = dyn_cast<CXXDeductionGuideDecl>(D))
+ Result.insert(GD->getSourceDeductionGuide());
+ }
+ return Result;
+}
+
// Build the associated constraints for the alias deduction guides.
// C++ [over.match.class.deduct]p3.3:
// The associated constraints ([temp.constr.decl]) are the conjunction of the
@@ -1191,13 +1209,10 @@ void DeclareImplicitDeductionGuidesForTypeAlias(
if (AliasTemplate->isInvalidDecl())
return;
auto &Context = SemaRef.Context;
- // FIXME: if there is an explicit deduction guide after the first use of the
- // type alias usage, we will not cover this explicit deduction guide. fix
this
- // case.
- if (hasDeclaredDeductionGuides(
- Context.DeclarationNames.getCXXDeductionGuideName(AliasTemplate),
- AliasTemplate->getDeclContext()))
- return;
+ auto SourceDeductionGuides = getSourceDeductionGuides(
+ Context.DeclarationNames.getCXXDeductionGuideName(AliasTemplate),
+ AliasTemplate->getDeclContext());
+
auto [Template, AliasRhsTemplateArgs] =
getRHSTemplateDeclAndArgs(SemaRef, AliasTemplate);
if (!Template)
@@ -1210,6 +1225,8 @@ void DeclareImplicitDeductionGuidesForTypeAlias(
for (auto *G : Guides) {
if (auto *DG = dyn_cast<CXXDeductionGuideDecl>(G)) {
+ if (SourceDeductionGuides.contains(DG))
+ continue;
// The deduction guide is a non-template function decl, we just clone it.
auto *FunctionType =
SemaRef.Context.getTrivialTypeSourceInfo(DG->getType());
@@ -1252,7 +1269,7 @@ void DeclareImplicitDeductionGuidesForTypeAlias(
continue;
}
FunctionTemplateDecl *F = dyn_cast<FunctionTemplateDecl>(G);
- if (!F)
+ if (!F || SourceDeductionGuides.contains(F->getTemplatedDecl()))
continue;
// The **aggregate** deduction guides are handled in a different code path
// (DeclareAggregateDeductionGuideFromInitList), which involves the tricky
diff --git a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
index 2d43e46b9e3d76b..6a004769a6d4d61 100644
--- a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
+++ b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
@@ -237,8 +237,17 @@ static_assert(__is_same(decltype(s.t), int));
// explicit deduction guide.
Foo(int) -> Foo<X>;
AFoo s2{i};
-// FIXME: the type should be X because of the above explicit deduction guide.
-static_assert(__is_same(decltype(s2.t), int));
+static_assert(__is_same(decltype(s2.t), X));
+
+
+template<class T>
+using BFoo = AFoo<T>;
+static_assert(__is_same(decltype(BFoo(i).t), X));
+
+
+Foo(double) -> Foo<int>;
+static_assert(__is_same(decltype(AFoo(1.0).t), int));
+static_assert(__is_same(decltype(BFoo(1.0).t), int));
} // namespace test16
namespace test17 {
>From abc88828cba91ae54244b8582e60d87c7980e555 Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein...@gmail.com>
Date: Mon, 3 Feb 2025 14:29:06 +0100
Subject: [PATCH 2/3] Address review comments.
---
clang/lib/Sema/SemaTemplateDeductionGuide.cpp | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/clang/lib/Sema/SemaTemplateDeductionGuide.cpp
b/clang/lib/Sema/SemaTemplateDeductionGuide.cpp
index f5884f964d6fbd5..e5931f4684a57d8 100644
--- a/clang/lib/Sema/SemaTemplateDeductionGuide.cpp
+++ b/clang/lib/Sema/SemaTemplateDeductionGuide.cpp
@@ -752,8 +752,12 @@ llvm::DenseSet<const NamedDecl *>
getSourceDeductionGuides(DeclarationName Name,
if (const auto *FTD = dyn_cast<FunctionTemplateDecl>(D))
D = FTD->getTemplatedDecl();
- if (const auto *GD = dyn_cast<CXXDeductionGuideDecl>(D))
+ if (const auto *GD = dyn_cast<CXXDeductionGuideDecl>(D)) {
+ assert(GD->getSourceDeductionGuide() &&
+ "deduction guide for alias template must have a source deduction "
+ "guide");
Result.insert(GD->getSourceDeductionGuide());
+ }
}
return Result;
}
@@ -1209,14 +1213,14 @@ void DeclareImplicitDeductionGuidesForTypeAlias(
if (AliasTemplate->isInvalidDecl())
return;
auto &Context = SemaRef.Context;
- auto SourceDeductionGuides = getSourceDeductionGuides(
- Context.DeclarationNames.getCXXDeductionGuideName(AliasTemplate),
- AliasTemplate->getDeclContext());
-
auto [Template, AliasRhsTemplateArgs] =
getRHSTemplateDeclAndArgs(SemaRef, AliasTemplate);
if (!Template)
return;
+ auto SourceDeductionGuides = getSourceDeductionGuides(
+ Context.DeclarationNames.getCXXDeductionGuideName(AliasTemplate),
+ AliasTemplate->getDeclContext());
+
DeclarationNameInfo NameInfo(
Context.DeclarationNames.getCXXDeductionGuideName(Template), Loc);
LookupResult Guides(SemaRef, NameInfo, clang::Sema::LookupOrdinaryName);
>From 17505514f55f791f8f509df78bfd42ecc75e3fae Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein...@gmail.com>
Date: Mon, 10 Feb 2025 14:43:08 +0100
Subject: [PATCH 3/3] Add a test case for explicit template deduction guides.
---
clang/test/SemaCXX/cxx20-ctad-type-alias.cpp | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
index 6a004769a6d4d61..37dca2215af6ba3 100644
--- a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
+++ b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
@@ -234,16 +234,19 @@ int i = 0;
AFoo s{i};
static_assert(__is_same(decltype(s.t), int));
-// explicit deduction guide.
-Foo(int) -> Foo<X>;
-AFoo s2{i};
-static_assert(__is_same(decltype(s2.t), X));
-
-
template<class T>
using BFoo = AFoo<T>;
-static_assert(__is_same(decltype(BFoo(i).t), X));
+// template explicit deduction guide.
+template<class T>
+Foo(T) -> Foo<float>;
+static_assert(__is_same(decltype(AFoo(i).t), float));
+static_assert(__is_same(decltype(BFoo(i).t), float));
+
+// explicit deduction guide.
+Foo(int) -> Foo<X>;
+static_assert(__is_same(decltype(AFoo(i).t), X));
+static_assert(__is_same(decltype(BFoo(i).t), X));
Foo(double) -> Foo<int>;
static_assert(__is_same(decltype(AFoo(1.0).t), int));
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