[Bug c++/111602] [11/12/13/14 Regression] "Error: symbol is already defined" for variable template dependent on default argument lambda of class dependent on local type used in sfinae and non-sfinae contexts

[ed at catmur dot uk via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111602

--- Comment #2 from Ed Catmur <ed at catmur dot uk> ---
(In reply to Andrew Pinski from comment #1)
> The local type of f() is not needed.

Thanks! I was confused since the local type is required in this similar
example:

template<class> struct P
{
    static constexpr bool value = true;
};
template<class T> constexpr bool P<T>::value;
template<bool> struct E {};
struct F
{
    template<class T, class = E<P<T>::value>>
    F(T) {}
};
template<class> struct C
{
    C(F = []{}) {}
};
auto f()
{
    struct T {} t;
    return t;
}
template<class T>
decltype(T()) g()
{
    return T();
}
int main()
{
    g<C<decltype(f)>>();
}