Pre-RFC: Explicit overload sets for mixed-arity function calls

chrefr:

I don't think the solution is to not provide powerful features; rather, you should trust your users (and I agree that we should prefer features that are harder to misuse).

Some features have impact on the language even when not used, however. So it's important to avoid those things anyway.

For example, it's currently the case that you can implement inherent methods for arbitrary crate types in a block inside a const generic argument. Almost nobody uses that, because it's extremely rare that it's useful. But it has IDE responsiveness cost, so with prompting from R-A we're trying to find a way to remove some of the flexibility here because the compiler can't just "trust the users" and needs to support everything allowed.