[all-commits] [llvm/llvm-project] c5f461: [Clang][Parse] Diagnose member template declaratio...

[Krystian Stasiowski via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c5f461918cece4362fb70c7b16de4e95c1af8e5f
      https://github.com/llvm/llvm-project/commit/c5f461918cece4362fb70c7b16de4e95c1af8e5f
  Author: Krystian Stasiowski <sdkrystian at gmail.com>
  Date:   2024-02-01 (Thu, 01 Feb 2024)

  Changed paths:
    M clang/docs/ReleaseNotes.rst
    M clang/include/clang/Parse/Parser.h
    M clang/lib/Parse/ParseDecl.cpp
    M clang/lib/Parse/ParseDeclCXX.cpp
    M clang/lib/Parse/ParseTemplate.cpp
    M clang/lib/Parse/Parser.cpp
    M clang/test/CXX/temp/p3.cpp
    M clang/test/OpenMP/declare_simd_messages.cpp

  Log Message:
  -----------
  [Clang][Parse] Diagnose member template declarations with multiple declarators (#78243)

According to [temp.pre] p5:
> In a template-declaration, explicit specialization, or explicit instantiation the init-declarator-list in the declaration shall contain at most one declarator. 

A member-declaration that is a template-declaration or explicit-specialization contains a declaration, even though it declares a member. This means it _will_ contain an init-declarator-list (not a member-declarator-list), so [temp.pre] p5 applies.

This diagnoses declarations such as:
```
struct A
{
    template<typename T>
    static const int x = 0, f(); // error: a template declaration can only declare a single entity

    template<typename T>
    static const int g(), y = 0; // error: a template declaration can only declare a single entity
};
```
The diagnostic messages are the same as those of the equivalent namespace scope declarations.

Note: since we currently do not diagnose declarations with multiple abbreviated function template declarators at namespace scope e.g., `void f(auto), g(auto);`, so this patch does not add diagnostics for the equivalent member declarations.

This patch also refactors `ParseSingleDeclarationAfterTemplate` (now named `ParseDeclarationAfterTemplate`) to call `ParseDeclGroup` and return the resultant `DeclGroup`.