Figure out a better way to track for reporting when a method is being used like a field

[erickt]

Adding this issue now before landing my pull request.

Even though you can't treat a method like a field, we need to add any trait methods we find that match the field name so that we can do some nice error reporting later on in typeck.

[bblum]

Related #2392. Maybe the same issue?

[huonw]

Triage: I see

struct Foo { x: int }

impl Foo {
    fn y(&self) {}
}
trait Z { fn z(&self); }
impl Z for Foo {
    fn z(&self) {}
}

fn main() {
    let a = Foo { x: 1 };
    a.y;
    a.z;
}

6890.rs:13:4: 13:7 error: attempted to take value of method `y` on type `Foo` (try writing an anonymous function)
6890.rs:13     a.y;
               ^~~
6890.rs:14:4: 14:7 error: attempted to take value of method `z` on type `Foo` (try writing an anonymous function)
6890.rs:14     a.z;
               ^~~
error: aborting due to 2 previous errors

which seems pretty good. Closing (there are already tests for this), reopen if you disagree or if I'm misunderstanding.