[all-commits] [llvm/llvm-project] 7d1e28: [Clang][Sema] Ignore previous partial specializati...

[Krystian Stasiowski via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 7d1e283bd3b4440aea9ac375ca51e2ee6b0e86f5
      https://github.com/llvm/llvm-project/commit/7d1e283bd3b4440aea9ac375ca51e2ee6b0e86f5
  Author: Krystian Stasiowski <sdkrystian at gmail.com>
  Date:   2024-10-30 (Wed, 30 Oct 2024)

  Changed paths:
    M clang/docs/ReleaseNotes.rst
    M clang/lib/Sema/SemaTemplate.cpp
    M clang/lib/Sema/SemaTemplateInstantiate.cpp
    A clang/test/CXX/temp/temp.decls/temp.spec.partial/temp.spec.partial.member/p2.cpp

  Log Message:
  -----------
  [Clang][Sema] Ignore previous partial specializations of member templates explicitly specialized for an implicitly instantiated class template specialization (#113464)

Consider the following:
```
template<typename T>
struct A {
  template<typename U>
  struct B {
    static constexpr int x = 0; // #1
  };

  template<typename U>
  struct B<U*> {
    static constexpr int x = 1; // #2
  };
};

template<>
template<typename U>
struct A<long>::B {
  static constexpr int x = 2; // #3
};

static_assert(A<short>::B<int>::y == 0); // uses #1
static_assert(A<short>::B<int*>::y == 1); // uses #2

static_assert(A<long>::B<int>::y == 2); // uses #3
static_assert(A<long>::B<int*>::y == 2); // uses #3
```

According to [temp.spec.partial.member] p2:
> If the primary member template is explicitly specialized for a given
(implicit) specialization of the enclosing class template, the partial
specializations of the member template are ignored for this
specialization of the enclosing class template.
If a partial specialization of the member template is explicitly
specialized for a given (implicit) specialization of the enclosing class
template, the primary member template and its other partial
specializations are still considered for this specialization of the
enclosing class template.

The example above fails to compile because we currently don't implement
[temp.spec.partial.member] p2. This patch implements the wording, fixing #51051.



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