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Merged
merged 4 commits into from
Apr 17, 2025
Merged

[Clang] Handle default template arguments for alias CTAD guides #134807

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3f09d11
[Clang] Handle default template arguments for alias CTAD guides
zyn0217 Apr 8, 2025
a6c14db
Merge branch 'main' into default-args-ctad
zyn0217 Apr 8, 2025
0587264
Add tests for template/non-template parameters
zyn0217 Apr 15, 2025
7619b33
Address review feedback
zyn0217 Apr 15, 2025
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1 change: 1 addition & 0 deletions clang/docs/ReleaseNotes.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -390,6 +390,7 @@ Bug Fixes to C++ Support
- Clang no longer crashes when trying to unify the types of arrays with
certain differences in qualifiers (this could happen during template argument
deduction or when building a ternary operator). (#GH97005)
- Fixed type alias CTAD issues involving default template arguments. (#GH134471)
- The initialization kind of elements of structured bindings
direct-list-initialized from an array is corrected to direct-initialization.
- Clang no longer crashes when a coroutine is declared ``[[noreturn]]``. (#GH127327)
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20 changes: 20 additions & 0 deletions clang/lib/Sema/SemaTemplateDeductionGuide.cpp
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Expand Up @@ -690,6 +690,26 @@ SmallVector<unsigned> TemplateParamsReferencedInTemplateArgumentList(
SemaRef.MarkUsedTemplateParameters(
DeducedArgs, TemplateParamsList->getDepth(), ReferencedTemplateParams);

auto MarkDefaultArgs = [&](auto *Param) {
if (!Param->hasDefaultArgument())
return;
SemaRef.MarkUsedTemplateParameters(
Param->getDefaultArgument().getArgument(),
TemplateParamsList->getDepth(), ReferencedTemplateParams);
};

for (unsigned Index = 0; Index < TemplateParamsList->size(); ++Index) {
if (!ReferencedTemplateParams[Index])
continue;
auto *Param = TemplateParamsList->getParam(Index);
if (auto *TTPD = dyn_cast<TemplateTypeParmDecl>(Param))
MarkDefaultArgs(TTPD);
else if (auto *NTTPD = dyn_cast<NonTypeTemplateParmDecl>(Param))
MarkDefaultArgs(NTTPD);
else
MarkDefaultArgs(cast<TemplateTemplateParmDecl>(Param));
}

SmallVector<unsigned> Results;
for (unsigned Index = 0; Index < TemplateParamsList->size(); ++Index) {
if (ReferencedTemplateParams[Index])
Expand Down
117 changes: 116 additions & 1 deletion clang/test/SemaTemplate/deduction-guide.cpp
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@@ -1,4 +1,4 @@
// RUN: %clang_cc1 -std=c++2a -verify -ast-dump -ast-dump-decl-types -ast-dump-filter "deduction guide" %s | FileCheck %s --strict-whitespace
// RUN: %clang_cc1 -std=c++2a -verify -ast-dump -ast-dump-decl-types -ast-dump-filter "deduction guide" %s | FileCheck %s --strict-whitespace -dump-input=always

template<auto ...> struct X {};
template<template<typename X, X> typename> struct Y {};
Expand Down Expand Up @@ -771,3 +771,118 @@ D d(24);
// CHECK-NEXT: `-ParmVarDecl {{.+}} 'U'

} // namespace GH132616_DeductionGuide

namespace GH133132 {

template <class _Ty>
struct A {};

template <class T = int, class U = T>
using AA = A<U>;

AA a{};

// CHECK-LABEL: Dumping GH133132::<deduction guide for AA>:
// CHECK-NEXT: FunctionTemplateDecl {{.+}} implicit <deduction guide for AA>
// CHECK-NEXT: |-TemplateTypeParmDecl {{.+}} class depth 0 index 0 T
// CHECK-NEXT: | `-TemplateArgument type 'int'
// CHECK-NEXT: | `-BuiltinType {{.+}} 'int'
// CHECK-NEXT: |-TemplateTypeParmDecl {{.+}} class depth 0 index 1 U
// CHECK-NEXT: | `-TemplateArgument type 'T':'type-parameter-0-0'
// CHECK-NEXT: | `-TemplateTypeParmType {{.+}} 'T' dependent depth 0 index 0
// CHECK-NEXT: | `-TemplateTypeParm {{.+}} 'T'
// CHECK-NEXT: |-TypeTraitExpr {{.+}} 'bool' __is_deducible
// CHECK-NEXT: | |-DeducedTemplateSpecializationType {{.+}} 'GH133132::AA' dependent
// CHECK-NEXT: | | `-name: 'GH133132::AA'
// CHECK-NEXT: | | `-TypeAliasTemplateDecl {{.+}} AA
// CHECK-NEXT: | `-TemplateSpecializationType {{.+}} 'A<U>' dependent
// CHECK-NEXT: | |-name: 'A':'GH133132::A' qualified
// CHECK-NEXT: | | `-ClassTemplateDecl {{.+}} A
// CHECK-NEXT: | `-TemplateArgument type 'U':'type-parameter-0-1'
// CHECK-NEXT: | `-SubstTemplateTypeParmType {{.+}} 'U' sugar dependent class depth 0 index 0 _Ty
// CHECK-NEXT: | |-FunctionTemplate {{.+}} '<deduction guide for A>'
// CHECK-NEXT: | `-TemplateTypeParmType {{.+}} 'U' dependent depth 0 index 1
// CHECK-NEXT: | `-TemplateTypeParm {{.+}} 'U'
// CHECK-NEXT: |-CXXDeductionGuideDecl {{.+}} implicit <deduction guide for AA> 'auto () -> A<U>'
// CHECK-NEXT: `-CXXDeductionGuideDecl {{.+}} implicit used <deduction guide for AA> 'auto () -> A<int>' implicit_instantiation
// CHECK-NEXT: |-TemplateArgument type 'int'
// CHECK-NEXT: | `-BuiltinType {{.+}} 'int'
// CHECK-NEXT: `-TemplateArgument type 'int'
// CHECK-NEXT: `-BuiltinType {{.+}} 'int'

template <template <class> class _X>
struct B {};

template <template <class> class _X = A, template <class> class _Y = _X>
using BB = B<_Y>;

BB b{};

// CHECK-LABEL: Dumping GH133132::<deduction guide for BB>:
// CHECK-NEXT: FunctionTemplateDecl {{.+}} implicit <deduction guide for BB>
// CHECK-NEXT: |-TemplateTemplateParmDecl {{.+}} depth 0 index 0 _X
// CHECK-NEXT: | |-TemplateTypeParmDecl {{.+}} class depth 0 index 0
// CHECK-NEXT: | `-TemplateArgument {{.+}} template 'A':'GH133132::A' qualified
// CHECK-NEXT: | `-ClassTemplateDecl {{.+}} A
// CHECK-NEXT: |-TemplateTemplateParmDecl {{.+}} depth 0 index 1 _Y
// CHECK-NEXT: | |-TemplateTypeParmDecl {{.+}} class depth 0 index 0
// CHECK-NEXT: | `-TemplateArgument {{.+}} template '_X':'template-parameter-0-0' qualified
// CHECK-NEXT: | `-TemplateTemplateParmDecl {{.+}} depth 0 index 0 _X
// CHECK-NEXT: |-TypeTraitExpr {{.+}} 'bool' __is_deducible
// CHECK-NEXT: | |-DeducedTemplateSpecializationType {{.+}} 'GH133132::BB' dependent
// CHECK-NEXT: | | `-name: 'GH133132::BB'
// CHECK-NEXT: | | `-TypeAliasTemplateDecl {{.+}} BB
// CHECK-NEXT: | `-TemplateSpecializationType {{.+}} 'B<_Y>' dependent
// CHECK-NEXT: | |-name: 'B':'GH133132::B' qualified
// CHECK-NEXT: | | `-ClassTemplateDecl {{.+}} B
// CHECK-NEXT: | `-TemplateArgument template '_Y':'template-parameter-0-1' subst index 0
// CHECK-NEXT: | |-parameter: TemplateTemplateParmDecl {{.+}} depth 0 index 0 _X
// CHECK-NEXT: | |-associated FunctionTemplate {{.+}} '<deduction guide for B>'
// CHECK-NEXT: | `-replacement: '_Y':'template-parameter-0-1' qualified
// CHECK-NEXT: | `-TemplateTemplateParmDecl {{.+}} depth 0 index 1 _Y
// CHECK-NEXT: |-CXXDeductionGuideDecl {{.+}} implicit <deduction guide for BB> 'auto () -> B<_Y>'
// CHECK-NEXT: `-CXXDeductionGuideDecl {{.+}} implicit used <deduction guide for BB> 'auto () -> B<GH133132::A>' implicit_instantiation
// CHECK-NEXT: |-TemplateArgument template 'GH133132::A'
// CHECK-NEXT: | `-ClassTemplateDecl {{.+}} A
// CHECK-NEXT: `-TemplateArgument template 'GH133132::A'
// CHECK-NEXT: `-ClassTemplateDecl {{.+}} A

template <int N = 42, class U = A<decltype(N)>>
using CC = A<U>;

CC c{};

// CHECK-LABEL: Dumping GH133132::<deduction guide for CC>:
// CHECK-NEXT: FunctionTemplateDecl {{.+}} implicit <deduction guide for CC>
// CHECK-NEXT: |-NonTypeTemplateParmDecl {{.+}} 'int' depth 0 index 0 N
// CHECK-NEXT: | `-TemplateArgument {{.+}} expr '42'
// CHECK-NEXT: | `-IntegerLiteral {{.+}} 'int' 42
// CHECK-NEXT: |-TemplateTypeParmDecl {{.+}} class depth 0 index 1 U
// CHECK-NEXT: | `-TemplateArgument type 'A<decltype(N)>'
// CHECK-NEXT: | `-ElaboratedType {{.+}} 'A<decltype(N)>' sugar dependent
// CHECK-NEXT: | `-TemplateSpecializationType {{.+}} 'A<decltype(N)>' dependent
// CHECK-NEXT: | |-name: 'A':'GH133132::A' qualified
// CHECK-NEXT: | | `-ClassTemplateDecl {{.+}} A
// CHECK-NEXT: | `-TemplateArgument type 'decltype(N)'
// CHECK-NEXT: | `-DecltypeType {{.+}} 'decltype(N)' dependent
// CHECK-NEXT: | `-DeclRefExpr {{.+}} 'int' NonTypeTemplateParm {{.+}} 'N' 'int'
// CHECK-NEXT: |-TypeTraitExpr {{.+}} 'bool' __is_deducible
// CHECK-NEXT: | |-DeducedTemplateSpecializationType {{.+}} 'GH133132::CC' dependent
// CHECK-NEXT: | | `-name: 'GH133132::CC'
// CHECK-NEXT: | | `-TypeAliasTemplateDecl {{.+}} CC
// CHECK-NEXT: | `-TemplateSpecializationType {{.+}} 'A<U>' dependent
// CHECK-NEXT: | |-name: 'A':'GH133132::A' qualified
// CHECK-NEXT: | | `-ClassTemplateDecl {{.+}} A
// CHECK-NEXT: | `-TemplateArgument type 'U':'type-parameter-0-1'
// CHECK-NEXT: | `-SubstTemplateTypeParmType {{.+}} 'U' sugar dependent class depth 0 index 0 _Ty
// CHECK-NEXT: | |-FunctionTemplate {{.+}} '<deduction guide for A>'
// CHECK-NEXT: | `-TemplateTypeParmType {{.+}} 'U' dependent depth 0 index 1
// CHECK-NEXT: | `-TemplateTypeParm {{.+}} 'U'
// CHECK-NEXT: |-CXXDeductionGuideDecl {{.+}} implicit <deduction guide for CC> 'auto () -> A<U>'
// CHECK-NEXT: `-CXXDeductionGuideDecl {{.+}} implicit used <deduction guide for CC> 'auto () -> A<GH133132::A<int>>' implicit_instantiation
// CHECK-NEXT: |-TemplateArgument integral '42'
// CHECK-NEXT: `-TemplateArgument type 'GH133132::A<int>'
// CHECK-NEXT: `-RecordType {{.+}} 'GH133132::A<int>'
// CHECK-NEXT: `-ClassTemplateSpecialization {{.+}} 'A'

}
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