[all-commits] [llvm/llvm-project] 3cdb30: [Clang][Sema] Use the correct lookup context when ...

[Krystian Stasiowski via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3cdb30ebbc18fa894d3bd67aebcff76ce7c741ac
      https://github.com/llvm/llvm-project/commit/3cdb30ebbc18fa894d3bd67aebcff76ce7c741ac
  Author: Krystian Stasiowski <sdkrystian at gmail.com>
  Date:   2024-09-09 (Mon, 09 Sep 2024)

  Changed paths:
    M clang/include/clang/Sema/Sema.h
    M clang/lib/Sema/SemaExprCXX.cpp
    M clang/lib/Sema/SemaOverload.cpp
    M clang/lib/Sema/TreeTransform.h
    M clang/test/CXX/temp/temp.res/temp.dep/temp.dep.type/p4.cpp

  Log Message:
  -----------
  [Clang][Sema] Use the correct lookup context when building overloaded 'operator->' in the current instantiation (#104458)

Currently, clang erroneously rejects the following:
```
struct A
{
    template<typename T>
    void f();
};

template<typename T>
struct B
{
    void g()
    {
        (*this)->template f<int>(); // error: no member named 'f' in 'B<T>'
    }

    A* operator->();
};
```

This happens because `Sema::ActOnStartCXXMemberReference` does not adjust the `ObjectType` parameter when `ObjectType` is a dependent type (except when the type is a `PointerType` and the class member access is the `->` form). Since the (possibly adjusted) `ObjectType` parameter (`B<T>` in the above example) is passed to `Parser::ParseOptionalCXXScopeSpecifier`, we end up looking up `f` in `B` rather than `A`. 

This patch fixes the issue by identifying cases where the type of the object expression `T` is a dependent, non-pointer type and:
- `T` is the current instantiation and lookup for `operator->` finds a member of the current instantiation, or
- `T` has at least one dependent base case, and `operator->` is not found in the current instantiation

and using `ASTContext::DependentTy` as the type of the object expression when the optional _nested-name-specifier_ is parsed.

Fixes #104268.



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