bindings fail to compile with "the name ... is defined multiple times"

C++ header

template <typename> class a {
  typedef int b;
  a &c(long, b);
};
template <> a<char> &a<char>::c(long, b);
template <> a<wchar_t> &a<wchar_t>::c(long, b);

bindgen command

bindgen test-case-2.hpp -- -x c++

Generated bindings

#[repr(C)]
#[derive(Debug, Copy, Clone)]
pub struct a {
    pub _address: u8,
}
pub type a_b = ::std::os::raw::c_int;
pub type b = ::std::os::raw::c_int;
pub type b = ::std::os::raw::c_int;

rustc errors with

error[E0428]: the name `b` is defined multiple times

Expected Results

I would expect that bindgen would error if this c++ header is not usable with bindgen or the bindings would compile and it is usable. Sorry my c++ is pretty poor, so I can't make a more informed statement.

Start by running the shown bindgen command against test-case-2.hpp and inspect the generated Rust aliases. Trace how the two C++ specializations produce duplicate b definitions; done means the bindings compile without duplicate names or bindgen reports a clear unsupported-input error.