ICE 'type' was a a subtype of 'type' but now it is not

[Marwes]

Got an ICE when trying to return a Box<_> which contains associated types

pub trait Parser {
    type Input;
    fn parse(&mut self, input: <Self as Parser>::Input);
}
impl Parser for () {
    type Input = ();
    fn parse(&mut self, input: ()) {

    }
}
pub fn many() -> Box<Parser<Input=<() as Parser>::Input> + 'static> {
    panic!()
}

fn main() {
    many()
        .parse(());
}

Error and backtrace:

`error.rs:18:10: 18:19 error: internal compiler error: &mut Parser + 'static was
a subtype of &mut Parser + 'static but now is not?
error.rs:18         .parse(());
                     ^~~~~~~~~
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: http://doc.rust-lang.org/complement-bugreport.html
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'Box<Any>', C:\bot\slave\nightly-dist-rustc-win-64\build\src\libsyntax\diagnostic.rs:123

stack backtrace:
   1:         0x69bec997 - sys::backtrace::write::h62d87c63e18a3ea5JRt
   2:         0x69c00672 - rt::unwind::register::haa3a38fa07bfa9beVGz
   3:         0x69b834a7 - rt::unwind::begin_unwind_inner::hbebf9f8c0125ffc9tEz
   4:         0x6f898116 - diagnostic::SpanHandler::span_bug::hebc2106d060dd9d6xSF
   5:         0x6f8980cb - diagnostic::SpanHandler::span_bug::hebc2106d060dd9d6xSF
   6:           0x5e1d0a - session::Session::span_bug::h08799ba60bf74646cQq
   7:         0x6d50bbe4 - check::method::probe::Pick<'tcx>.Repr<'tcx>::repr::h1c3027b8aeb1b724Qjh
   8:         0x6d587cd1 - check::LvaluePreference...std..cmp..Eq::assert_receiver_is_total_eq::h22fc9549f98e035eaom
   9:         0x6d5a6750 - check::LvaluePreference...std..cmp..Eq::assert_receiver_is_total_eq::h22fc9549f98e035eaom
  10:         0x6d566063 - check::GatherLocalsVisitor<'a, 'tcx>.Visitor<'v>::visit_item::h6a396874613b07b20dk
  11:         0x6d553fdd - check::FnCtxt<'a, 'tcx>.RegionScope::anon_regions::hdbf64e315fb3c7658mm
  12:         0x6d56319e - check::CheckItemTypesVisitor<'a, 'tcx>.Visitor<'v>::visit_ty::h8db07a75f4d7ec1c31j
  13:         0x6d55ae70 - check::CheckItemTypesVisitor<'a, 'tcx>.Visitor<'v>::visit_item::h6010e6ec5a0a2b14G1j
  14:         0x6d625870 - check_crate::hd6caa8c10c4dd23523x
  15:         0x6d620844 - check_crate::hd6caa8c10c4dd23523x
  16:         0x70b1e6bf - driver::phase_3_run_analysis_passes::hca97b7f3e7dde725gwa
  17:         0x70b02abd - driver::compile_input::hf5b2f58693da03b5xba
  18:         0x70bd1eec - run::ha65e56249318cc0dV3b
  19:         0x70bd04cc - run::ha65e56249318cc0dV3b
  20:         0x70bcf16a - run::ha65e56249318cc0dV3b
  21:         0x69c2881c - rust_try
  22:         0x69c287f9 - rust_try
  23:         0x70bcf854 - run::ha65e56249318cc0dV3b
  24:         0x69bf14a7 - sys::tcp::TcpListener::bind::hc4a8da4adad0f541bsw
  25:     0x7fff4c8816ad - BaseThreadInitThunk

rustc 1.0.0-nightly (44a287e6e 2015-01-08 17:03:40 -0800)
binary: rustc
commit-hash: 44a287e6eb22ec3c2a687fc156813577464017f7
commit-date: 2015-01-08 17:03:40 -0800
host: x86_64-pc-windows-gnu
release: 1.0.0-nightly

[Aatch]

Looks like it might be an associated items issue? @nikomatsakis?

[nikomatsakis]

Indeed, it works fine if I remove the associated type:

pub trait Parser {
    type Input;
    fn parse(&mut self, input: <Self as Parser>::Input);
}
impl Parser for () {
    type Input = ();
    fn parse(&mut self, input: ()) {

    }
}
pub fn many() -> Box<Parser<Input=()> + 'static> {
    panic!()
}

fn main() {
    many()
        .parse(());
}

Presumably we're failing to normalize somewhere.

[nikomatsakis]

This works for me now.

[goffrie]

Looks like the fixing commit had a typo in the bug number - this ought to be closed now, right?

[Aatch]

I can't figure out which PR fixed this. But I'm going to assume that it's fixed.