ICE with associated types defaults

[jorisgio]

Associated types defaults ( #19476 ) cause at least two different ICE with rustc 1.0.0-nightly (b4c965e 2015-03-02) (built 2015-03-03)

Case 1 : building :

trait Foo { type T; }
trait Bar {
    type Foo: Foo;
    type FooT = <<Self as Bar>::Foo as Foo>::T;
}

Case 2 : ICE

trait Foo { type T; }
trait Bar {
    type Foo: Foo;
    type FooT = <<Self>::Foo>::T;
}

backtrace :

  1:     0x7f9849be3baf - sys::backtrace::write::hbe65ff4402631268QyA
   2:     0x7f9849c0c6e2 - panicking::on_panic::h245e35885d5e01ccFDJ
   3:     0x7f9849b4743a - rt::unwind::begin_unwind_inner::he6d56a943f3050638jJ
   4:     0x7f9849b47b24 - rt::unwind::begin_unwind_fmt::h334fac4699ed6f75LiJ
   5:     0x7f9849c0c267 - rust_begin_unwind
   6:     0x7f9849c55cf4 - panicking::panic_fmt::hfac991238dca4c38b9r
   7:     0x7f9848fc8531 - PrivacyVisitor<'a, 'tcx>::check_path::h14d56d7374e51ab607a
   8:     0x7f9848fc957b - PrivacyVisitor<'a, 'tcx>.Visitor<'v>::visit_path::h1a3768654016f45e7vb
   9:     0x7f9848fc981e - visit::walk_ty::h8843244089880601813
  10:     0x7f9848fc93a1 - PrivacyVisitor<'a, 'tcx>.Visitor<'v>::visit_item::h8973ade95546b892xgb
  11:     0x7f9848fd046b - check_crate::hbba214d62d5303eexXb
  12:     0x7f984a26c390 - driver::phase_3_run_analysis_passes::h1b4e3b2c9313b117xFa
  13:     0x7f984a251301 - driver::compile_input::hc62aeb837327f1f4Iba
  14:     0x7f984a31bd2e - run_compiler::h978681e22b0d6976F5b
  15:     0x7f984a3198dc - thunk::F.Invoke<A, R>::invoke::h10120836201339486783
  16:     0x7f984a318630 - rt::unwind::try::try_fn::h11016953016221458849
  17:     0x7f9849c78028 - rust_try_inner
  18:     0x7f9849c78015 - rust_try
  19:     0x7f984a318d1c - thunk::F.Invoke<A, R>::invoke::h13067427317151836004
  20:     0x7f9849bf8235 - sys::thread::thread_start::h106a33ed9d873acaj5E
  21:     0x7f9843931313 - start_thread
  22:     0x7f98497ce24c - clone
  23: 0xffffffffffffffff - <unknown>

Case 3 : ICE

trait Foo { type T; }
trait Bar {
    type Foo: Foo;
    type FooT = Self::Foo::T;
}

backtrace :

stack backtrace:
   1:     0x7f8951506baf - sys::backtrace::write::hbe65ff4402631268QyA
   2:     0x7f895152f6e2 - panicking::on_panic::h245e35885d5e01ccFDJ
   3:     0x7f895146a43a - rt::unwind::begin_unwind_inner::he6d56a943f3050638jJ
   4:     0x7f895146ab24 - rt::unwind::begin_unwind_fmt::h334fac4699ed6f75LiJ
   5:     0x7f894f112ae6 - middle::def::PathResolution::full_def::h4c8aebcfff75b091YPk
   6:     0x7f89508eb3de - PrivacyVisitor<'a, 'tcx>::check_path::h14d56d7374e51ab607a
   7:     0x7f89508ec57b - PrivacyVisitor<'a, 'tcx>.Visitor<'v>::visit_path::h1a3768654016f45e7vb
   8:     0x7f89508ec3a1 - PrivacyVisitor<'a, 'tcx>.Visitor<'v>::visit_item::h8973ade95546b892xgb
   9:     0x7f89508f346b - check_crate::hbba214d62d5303eexXb
  10:     0x7f8951b8f390 - driver::phase_3_run_analysis_passes::h1b4e3b2c9313b117xFa
  11:     0x7f8951b74301 - driver::compile_input::hc62aeb837327f1f4Iba
  12:     0x7f8951c3ed2e - run_compiler::h978681e22b0d6976F5b
  13:     0x7f8951c3c8dc - thunk::F.Invoke<A, R>::invoke::h10120836201339486783
  14:     0x7f8951c3b630 - rt::unwind::try::try_fn::h11016953016221458849
  15:     0x7f895159b028 - rust_try_inner
  16:     0x7f895159b015 - rust_try
  17:     0x7f8951c3bd1c - thunk::F.Invoke<A, R>::invoke::h13067427317151836004
  18:     0x7f895151b235 - sys::thread::thread_start::h106a33ed9d873acaj5E
  19:     0x7f894b254313 - start_thread
  20:     0x7f89510f124c - clone
  21: 0xffffffffffffffff - <unknown>

[eddyb]

Thanks! Both of the ICE cases are caused by changes I've made which assume every type (including those defaults) is instantiated by astconv during typeck.
Because defaults are not implemented, that assumption is wrong - the simplest fix I can see would be to instantiate those defaults even if they're unused.

@nikomatsakis @japaric Are there any immediate plans for implementing those defaults?

[theemathas]

Variant of case 3:

trait What { type T; }
trait Bar {
    type Foo;
    type FooT = Self::Foo::T;
}

The difference is that this code is invalid.

[nikomatsakis]

On Thu, Mar 05, 2015 at 08:07:50AM -0800, Eduard Burtescu wrote:

Thanks! Both of the ICE cases are caused by changes I've made which assume every type (including those defaults) is instantiated by astconv during typeck.
Because defaults are not implemented, that assumption is wrong - the simplest fix I can see would be to instantiate those defaults even if they're unused.

@nikomatsakis @japaric Are there any immediate plans for implementing those defaults?

I've been meaning to implement them for a while now, just keep getting distracted...

[arielb1]

These were fixed when defaults were implemented.