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[Clang] Fix a pack expansion bug in template argument deduction #141547

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Merged
merged 1 commit into from
May 27, 2025
Merged

[Clang] Fix a pack expansion bug in template argument deduction #141547

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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 @@ -795,6 +795,7 @@ Bug Fixes to C++ Support
- Fix instantiation of default-initialized variable template specialization. (#GH140632) (#GH140622)
- Clang modules now allow a module and its user to differ on TrivialAutoVarInit*
- Fixed an access checking bug when initializing non-aggregates in default arguments (#GH62444), (#GH83608)
- Fixed a pack substitution bug in deducing class template partial specializations. (#GH53609)

Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
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1 change: 1 addition & 0 deletions clang/lib/Sema/SemaTemplateDeduction.cpp
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Expand Up @@ -2946,6 +2946,7 @@ ConvertDeducedTemplateArgument(Sema &S, NamedDecl *Param,
LocalInstantiationScope Scope(S);
MultiLevelTemplateArgumentList Args(Template, CTAI.SugaredConverted,
/*Final=*/true);
Sema::ArgPackSubstIndexRAII OnlySubstNonPackExpansion(S, std::nullopt);

if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(Param)) {
Sema::InstantiatingTemplate Inst(S, Template->getLocation(), Template,
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17 changes: 17 additions & 0 deletions clang/test/CXX/temp/temp.fct.spec/temp.deduct/p7.cpp
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Expand Up @@ -54,3 +54,20 @@ namespace reversed_operator_substitution_order {
float &s = no_adl::f<int>(true);
}
#endif

namespace GH53609 {

template <class, int>
struct a;

template <class, class...>
struct b;

template <class x, class... y, y... z>
struct b<x, a<y, z>...> {};

template <class... x> struct c: b<x>... {};

c<int> d;

}
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