This changes the current behaviour for two cases (that I know of)
```rust
mod foo {
extern crate bar;
}
// `bar::` changes to `foo::bar::`
```
```rust
extern crate bar as quux;
// `bar::` changes to `quux::`
```
For example:
```rust
mod foo {
extern crate core;
}
fn assert_clone<T>() where T : Clone { }
fn main() {
assert_clone::<foo::core::atomic::AtomicBool>();
// error: the trait `core::clone::Clone` is not implemented for the type `core::atomic::AtomicBool` [E0277]
// changes to
// error: the trait `foo::core::clone::Clone` is not implemented for the type `foo::core::atomic::AtomicBool` [E0277]
}
```
Notably the following test case broke:
```rust
#[bench]
fn bar(x: isize) { }
//~^ ERROR mismatched types
//~| expected `fn(&mut test::Bencher)`
// changed to
//~| expected `fn(&mut __test::test::Bencher)`
```
If a crate is linked multiple times the path with the least segments is stored.
Partially addresses #1920. (this doesn't solve the issue raised about re-exports)
r? @nikomatsakis
0dc2910c9c