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[clang] CTAD alias: Fix missing template arg packs during the transformation #92535

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Merged
merged 1 commit into from
May 20, 2024
Merged

[clang] CTAD alias: Fix missing template arg packs during the transformation #92535

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8 changes: 0 additions & 8 deletions clang/lib/Sema/TreeTransform.h
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Original file line number Diff line number Diff line change
Expand Up @@ -4818,14 +4818,6 @@ bool TreeTransform<Derived>::TransformTemplateArguments(
TemplateArgumentLoc In = *First;

if (In.getArgument().getKind() == TemplateArgument::Pack) {
// When building the deduction guides, we rewrite the argument packs
// instead of unpacking.
if (getSema().CodeSynthesisContexts.back().Kind ==
Sema::CodeSynthesisContext::BuildingDeductionGuides) {
if (getDerived().TransformTemplateArgument(In, Out, Uneval))
return true;
continue;
}
// Unpack argument packs, which we translate them into separate
// arguments.
// FIXME: We could do much better if we could guarantee that the
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20 changes: 20 additions & 0 deletions clang/test/AST/ast-dump-ctad-alias.cpp
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Expand Up @@ -48,3 +48,23 @@ Out2<double>::AInner t(1.0);
// CHECK-NEXT: | |-TemplateArgument type 'double'
// CHECK-NEXT: | | `-BuiltinType {{.*}} 'double'
// CHECK-NEXT: | `-ParmVarDecl {{.*}} 'double'

template <typename... T1>
struct Foo {
Foo(T1...);
};

template <typename...T2>
using AFoo = Foo<T2...>;
AFoo a(1, 2);
// CHECK: |-CXXDeductionGuideDecl {{.*}} implicit <deduction guide for AFoo> 'auto (type-parameter-0-0...) -> Foo<type-parameter-0-0...>'
// CHECK-NEXT: | | `-ParmVarDecl {{.*}} 'type-parameter-0-0...' pack
// CHECK-NEXT: | `-CXXDeductionGuideDecl {{.*}} implicit used <deduction guide for AFoo> 'auto (int, int) -> Foo<int, int>' implicit_instantiation

template <typename T>
using BFoo = Foo<T, T>;
BFoo b2(1.0, 2.0);
// CHECK: |-CXXDeductionGuideDecl {{.*}} implicit <deduction guide for BFoo> 'auto (type-parameter-0-0, type-parameter-0-0) -> Foo<type-parameter-0-0, type-parameter-0-0>'
// CHECK-NEXT: | | |-ParmVarDecl {{.*}} 'type-parameter-0-0'
// CHECK-NEXT: | | `-ParmVarDecl {{.*}} 'type-parameter-0-0'
// CHECK-NEXT: | `-CXXDeductionGuideDecl {{.*}} implicit used <deduction guide for BFoo> 'auto (double, double) -> Foo<double, double>' implicit_instantiation
5 changes: 5 additions & 0 deletions clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
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Expand Up @@ -173,6 +173,11 @@ template <typename... Ts>
using AFoo = Foo<Ts...>;

auto b = AFoo{};
AFoo a(1, 2);

template <typename T>
using BFoo = Foo<T, T>;
BFoo b2(1.0, 2.0);
} // namespace test13

namespace test14 {
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