ICE when using generic newtypes cross-crate

[sfackler]

Turns out it's impossible to use generic newtypes across crates:

test.rs:

pub struct Foo<T>(T);

impl<T> Foo<T> {
    pub fn new(t: T) -> Foo<T> {
        Foo(t)
    }
}

test2.rs:

extern mod test;

use test::{Foo};

struct Baz;

fn main() {
    Foo::new(Baz);
}

~ ❯ env RUST_LOG=rustc=1 rustc -L. test2.rs
task <unnamed> failed at 'assertion failed: `(left == right) && (right == left)` (left: `2`, right: `0`)', /build/rust-git/src/rust/src/librustc/middle/trans/callee.rs:385
error: internal compiler error: unexpected failure
note: the compiler hit an unexpected failure path. this is a bug
note: try running with RUST_LOG=rustc=1 to get further details and report the results to github.com/mozilla/rust/issues
task <unnamed> failed at 'explicit failure', /build/rust-git/src/rust/src/librustc/rustc.rs:377

This makes it impossible to use std::rt::io::buffered::BufferedStream.

[huonw]

Related to #7899 (but not identical).

[bluss]

This particular case seems to be fixed by the PR #9560 by pcwalton!

However, there are compiler errors on trying to use the test::Foo constructor directly..

[alexcrichton]

Flagging as needstest.