A conflict of name lookup when building with Visual Studio 2015

[straywarrior]

I'm using fmt library with Visual Studio 2015 (Microsoft C/C++ Optimizing Compiler version 19.00.24215.1) and I meet some error like this:
type fmt::ArgVisitor<Impl, Result>::Arg [with Impl=Impl, Result=void] here is inaccessible detected during instantiation of class fmt::internal::ArgFormatterBase<Impl, Char> [with Impl=Impl, Char=Char].
However, the same codes can be compiled with gcc.
I trace the codes and find that in class internal::ArgFormatterBase (at format.h:1949), it uses type Arg without namespace scope qualifier internal::. However, its base class ArgVisitor has a private declaration typedef internal::Arg Arg (at format.h:1567). So the compiler finds the private Arg and thinks it's not accessible.
I read the C++ standard and do not find that whether compiler should continue searching the namespace scope after finding a name that is not accessible.
I will seed a feedback to Visual Studio to find out is it a feature/bug of the compiler but I also want to get your opinions about changing the codes related to internal::Args.

[foonathan]

I could be wrong here, but according to the two phase lookup rules, an unqualified name in a template should not be deferred to instantiation, i.e. not look at the base class. However, MSVC has not implemented two phase lookup yet.

If replacing Arg with internal::Arg - or adding a typedef (again) - fixes the issue, I'll commit the changes.

[straywarrior]

Thanks for your explanation and I'm happy to learn something new. Agree with your solution.

[foonathan]

Please report if it works now.

[straywarrior]

It works. Thanks.

[vitaut]

MSVC has not implemented two phase lookup yet

LOL, really?