infer break use-as alias after macro expansion

[edwin0cheng]

#![allow(non_camel_case_types)]

mod m {
    macro_rules! _foo {
        ($x:ident) => { type $x = u64; }
    }
    pub(crate) use _foo as foo;
}

m::foo!(foo);
use foo as bar;

fn f() -> bar { 0 }
fn b() -> foo { 0 }

fn main() {  
    let _a  = f();      // _a : {unknown}
    let _b  = b();     // _b: u64
}

It is because use foo as bar is resolved before expansion of m::foo!(foo), and we didn't rewrite the aliased PerNs of bar. Note that legacy macro invocation (i.e. unquatified identifier like foo!) is not affected, because it is expanded before any item resolutions.