[Clang][Sema] Fix explicit specializations of member function templates with a deduced return type (#86817)
Clang erroneously rejects the following:
```
template<typename T>
struct A
{
template<typename U>
auto f();
};
template<>
template<typename U>
auto A<int>::f(); // error: conflicting types for 'f'
```
This happens because the explicit specialization of `f` has its return
type replaced with a dependent `AutoType` in `ActOnFunctionDeclarator`,
but no such replacement occurs for the implicitly instantiated function
template `A<int>::f`. Since the return types don't match, the explicit
specialization is diagnosed as an invalid redeclaration.
This patch moves the replacement of the return type to
`CheckFunctionDeclaration` so it also happens during instantiation.
`setObjectOfFriendDecl` will have been called by then, so the `isFriend
&& CurContext->isDependentContext()` condition is made redundant &
removed (as it already happens in `DeclContext::isDependentContext`).
`Sema::IsOverload` only checks the _declared_ return type (which isn't
changed by the adjustment), so adjusting the return type afterwards
should be safe.
GitOrigin-RevId: eb08c0f1659d12524f58a01bf174177b8acedf2e
1 file changed
