rustc recommends specialization for type parameters inside an extern block

[MaikKlein]

extern {
    fn sqrt<T>(f: T) -> T;
}

fn main(){}

playground

help: consider using specialization instead of type parameters

[MaikKlein]

I just realized that rustc doesn't refer to the feature specialization but to 'manual' specialization.

rustc --explain E0044

---

You can't use type parameters on foreign items. Example of erroneous code:

extern { fn some_func<T>(x: T); }

To fix this, replace the type parameter with the specializations that you
need:

extern { fn some_func_i32(x: i32); }
extern { fn some_func_i64(x: i64); } 

[oli-obk]

Diagnostics triage: just needs changing the wording to something that gives a clearer message.