Annoying limitations with `use` of same symbols

[cuviper]

@bruno_medeiros

I can think of going even further, and actually allowing imports of two symbols with same name even if they are not the same element (like Xxx), and only error out if the symbol is actually used. This would make glob imports work a lot better. (D uses this behaviour, and I think it works quite well)

I think this would be covered here:

Pre-RFC: allow conflicting names on import, only complain if used ambiguously

Consider a module that wants to use trait methods from both std::fmt::Write and std::io::Write (via write! or writeln!), and thus needs to import both. For anything other than a trait, it would work to use std::fmt; and use std::io; and then refer to the qualified names fmt::Write and io::Write. However, using the methods of a trait requires importing that trait directly, necessitating a rename: use std::fmt::Write as FmtWrite; use std::io::Write as IoWrite; This applies even if the module w…