Clang incorrectly identifies a member variable access as a free function template name

[dwblaikie]

https://godbolt.org/z/radhszraP

namespace foo {

template <typename T>
struct bar {};

}

using foo::bar;

template <class T>
struct A {
  struct B {
    int bar;
  };

  bool g(B& v) {
    return v.bar < 42;
  }
};

Clang output:

<source>:17:22: error: expected '>'
    return v.bar < 42;
                     ^
<source>:17:18: note: to match this '<'
    return v.bar < 42;
                 ^
<source>:17:22: error: expected unqualified-id
    return v.bar < 42;
                     ^
2 errors generated.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

[to268]

I'll try to investigate in the issue

[to268]

It's looks like we have a lookup bug and we treat foo::bar as an acceptable template name.
So we are using foo::bar instead of the bar field of the B struct, which is not the intended behavior.

[to268]

Aaron had a quick look at the issue and it can be also due to a parsing issue.
Because if we move struct B outside of struct A, we no longer get a compile time error,
it's the same thing when removing the template declaration from the struct.
Moreover, adding the -fdelayed-template-parsing flag fixes the issue.

CC @erichkeane