Issue 1:
This 3-liner crashes rustc:

struct CrashIt;
impl Iterator for CrashIt { }
fn main() { }

My original code did a lot more than that, but I tried to create the minimal repro case.

$ rustc --version --verbose
rustc 0.13.0-nightly (c6c786671 2015-01-04 00:50:59 +0000)
binary: rustc
commit-hash: c6c786671d692d7b13c2e5c68a53001327b4b125
commit-date: 2015-01-04 00:50:59 +0000
host: x86_64-unknown-linux-gnu
release: 0.13.0-nightly

$ RUST_BACKTRACE=1 rustc src/main.rs
src/main.rs:2:1: 2:30 error: internal compiler error: impl `VtableImpl(impl_def_id=DefId { krate: 0, node: 7 }:CrashIt.Iterator, substs=Substs[types=[[];[];[]], regions=[[];[];[]]], nested=[[];[];[]])` did not contain projection for `Obligation(predicate=<CrashIt as TraitRef(CrashIt, core::iter::Iterator)>::Item,depth=0)`
src/main.rs:2 impl Iterator for CrashIt { }
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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>', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:123

stack backtrace:
1: 0x7fbff73562d0 - sys::backtrace::write::h8532e701ef86014f4it
2: 0x7fbff737bb00 - failure::on_fail::h7532e1f79d134d5dzvz
3: 0x7fbff72e11c0 - rt::unwind::begin_unwind_inner::h97b151606151d62deaz
4: 0x7fbff218ec60 - rt::unwind::begin_unwind::h15809447133099964284
5: 0x7fbff218ebf0 - diagnostic::SpanHandler::span_bug::he8142ababcc30c39DFF
6: 0x7fbff568de70 - middle::traits::project::project_type::h947eece142ef049d52P
7: 0x7fbff568afd0 - middle::traits::project::opt_normalize_projection_type::hb3defb9cc9365d1e8UP
8: 0x7fbff5678ba0 - middle::traits::project::normalize_projection_type::hdc293893275ee559JTP
9: 0x7fbff568c470 - middle::traits::project::AssociatedTypeNormalizer<'a, 'b, 'tcx>.TypeFolder<'tcx>::fold_ty::h801cbd2cdff2eff1kSP
10: 0x7fbff69492e0 - middle::ty_fold::Rc<T>.TypeFoldable<'tcx>::fold_with::h6325524173844043840
11: 0x7fbff6949e90 - middle::ty_fold::VecPerParamSpace<T>.TypeFoldable<'tcx>::fold_with::h13884369302522804796
12: 0x7fbff6965280 - check::FnCtxt<'a, 'tcx>::instantiate_bounds::hed550a9659b70335Oll
13: 0x7fbff697dfc0 - check::wf::CheckTypeWellFormedVisitor<'ccx, 'tcx>::check_impl::closure.29997
14: 0x7fbff697a430 - check::wf::CheckTypeWellFormedVisitor<'ccx, 'tcx>::with_fcx::hb1283961ed8977b7Gfi
15: 0x7fbff6980d70 - check::wf::CheckTypeWellFormedVisitor<'ccx, 'tcx>.Visitor<'v>::visit_item::h001ababd87597e37soi
16: 0x7fbff6b6dfe0 - check_crate::unboxed_closure.40162
17: 0x7fbff6b68c30 - check_crate::h19fb6dea5733566ajsx
18: 0x7fbff78a7640 - driver::phase_3_run_analysis_passes::h46b1604d9f9f5633Tva
19: 0x7fbff7895ae0 - driver::compile_input::h68b8602933aad8d7wba
20: 0x7fbff7960eb0 - thunk::F.Invoke<A, R>::invoke::h18029802347644288836
21: 0x7fbff795fc60 - rt::unwind::try::try_fn::h6518866316425934196
22: 0x7fbff73e2400 - rust_try_inner
23: 0x7fbff73e23f0 - rust_try
24: 0x7fbff795ffb0 - thunk::F.Invoke<A, R>::invoke::h15513809553472565307
25: 0x7fbff7367e40 - sys::thread::thread_start::h5ea7ba97235331d5a9v
26: 0x7fbff19b2c20 - start_thread
27: 0x7fbff6f83899 - clone
28: 0x0 - <unknown>

Issue 2:
STR

Didn't have time to write a shorter snippet

#![crate_type = "lib"]
#![feature(associated_types, lang_items, unboxed_closures)]
#![no_std]

use Option::{None, Some};

trait Iterator {
type Item;

fn next(&mut self) -> Option<Self::Item>;
}

trait DoubleEndedIterator: Iterator {
fn next_back(&mut self) -> Option< <Self as Iterator>::Item>;
}

struct Rev<I>(I);

impl<I> Iterator for Rev<I> where I: DoubleEndedIterator {
// forgot this!
//type Item = <I as Iterator>::Item;

fn next(&mut self) -> Option< <I as Iterator>::Item> {
self.0.next_back()
}
}

#[lang = "copy"] trait Copy {}
#[lang = "sized"] trait Sized {}

enum Option<T> {
None,
Some(T),
}

#[lang = "fn_mut"]
trait FnMut<Args, Result> {
extern "rust-call" fn call_mut(&mut self, Args) -> Result;
}

Output

iter.rs:23:5: 25:6 error: internal compiler error: impl `VtableImpl(impl_def_id=DefId { krate: 0, node: 38 }:Rev<I>.Iterator, substs=Substs[types=[[_];[];[]], regions=[[];[];[]]], nested=[[Obligation(predicate=Binder(TraitPredicate(TraitRef(I, Sized))),depth=1), Obligation(predicate=Binder(TraitPredicate(TraitRef(I, DoubleEndedIterator))),depth=1)];[];[]])` did not contain projection for `Obligation(predicate=<Rev<I> as TraitRef(Rev<I>, Iterator)>::Item,depth=0)`
iter.rs:23 fn next(&mut self) -> Option< <I as Iterator>::Item> {
iter.rs:24 self.0.next_back()
iter.rs:25 }
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>', /root/rust/src/libsyntax/diagnostic.rs:123

stack backtrace:
1: 0x7fddb1e70120 - sys::backtrace::write::h3fe61c98bf398fe8P8s
2: 0x7fddb1e8fef0 - failure::on_fail::h55da319a91ee267cEpz
3: 0x7fddb1e05b40 - rt::unwind::begin_unwind_inner::h2a51826b093fcd9eJ3y
4: 0x7fddad24b3d0 - rt::unwind::begin_unwind::h3298842058425057001
5: 0x7fddad24b360 - diagnostic::SpanHandler::span_bug::heeaf2edd6daa003fNQF
6: 0x7fddb022acb0 - middle::traits::project::project_type::hcf50d7eec736df9c35P
7: 0x7fddb0222800 - middle::traits::fulfill::process_predicate::h3703aabc133e79cayGP
8: 0x7fddb0221ab0 - middle::traits::fulfill::FulfillmentContext<$u{27}tcx$GT$::select::h827e4d042486e566SzP
9: 0x7fddb00ee7c0 - middle::traits::fulfill::FulfillmentContext<$u{27}tcx$GT$::select_all_or_error::heebbe09eddbd26dfDwP
10: 0x7fddb1510cd0 - check::compare_impl_method::h359a8a44e8f8def4Zfk
11: 0x7fddb14ff0b0 - check::check_item::hfedb86714512d4d8XRj
12: 0x7fddb169d450 - check_crate::unboxed_closure.39783
13: 0x7fddb16981f0 - check_crate::h7446c5344d10b3c1cGx
14: 0x7fddb23a98d0 - driver::phase_3_run_analysis_passes::hb59d2d67157ec124gva
15: 0x7fddb2397fb0 - driver::compile_input::hff9e8d16e3108315vba
16: 0x7fddb24e4900 - thunk::F.Invoke<A,$u{20}R$GT$::invoke::h10803646332669730367
17: 0x7fddb24e36c0 - rt::unwind::try::try_fn::h3820096971255462672
18: 0x7fddb1ef4eb0 - rust_try_inner
19: 0x7fddb1ef4ea0 - rust_try
20: 0x7fddb24e3a10 - thunk::F.Invoke<A,$u{20}R$GT$::invoke::h15250775183210022334
21: 0x7fddb1e7f8d0 - sys::thread::thread_start::h7b82ef93cab3e580K1v
22: 0x7fddaca690c0 - start_thread
23: 0x7fddb1aab2d9 - __clone
24: 0x0 - <unknown>

Version

84f5ad8

cc @nikomatsakis