Issue 1:
Found an ICE playing with the experimental associated types:

#![feature(associated_types)]

impl<'a> IntoBuffer for &'a [u8] {
type T = &'a [u8];

fn into_buffer(self) -> &'a [u8] {
self
}
}

pub trait IntoBuffer {
type T;

fn into_buffer(self) -> <Self as IntoBuffer>::T;
}

fn main() {}

Errors with:

error: internal compiler error: unexpected panic
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
task 'rustc' panicked at 'No def'n found for DefId { krate: 0, node: 33 } in tcx.impl_or_trait_items', /Users/rustbuild/src/rust-buildbot/slave/nightly-mac/build/src/librustc/middle/ty.rs:4323

stack backtrace:
1: 0x113062ba2 - rt::backtrace::imp::write::h7579c368c127979b6it
2: 0x113065d3d - failure::on_fail::h8be83c0fdfea739bdBt
3: 0x1132d8f65 - unwind::begin_unwind_inner::h4bdb4ca88294d49812c
4: 0x1132d8baf - unwind::begin_unwind_fmt::hae17deb499932f75c0c
5: 0x110158c84 - middle::ty::impl_or_trait_item::h4faeda649e6a6f19H64
6: 0x1105141d9 - middle::typeck::collect::ImplCtxt<'a, 'tcx>.AstConv<'tcx>::associated_type_binding::h9055dfc46b8c27bakJG
7: 0x110527559 - middle::typeck::astconv::create_substs_for_ast_path::h5023519427691145276
8: 0x110436fcc - middle::typeck::collect::convert::h0d3126dddfce9a9eF3G
9: 0x11042cf73 - middle::typeck::collect::collect_item_types::h2e912e08bc7db61fCYF
10: 0x1106c0f96 - util::common::time::h15512248264236370325
11: 0x1106c02ee - middle::typeck::check_crate::h7708c70a36786f0djVL
12: 0x10fcb1d93 - driver::driver::phase_3_run_analysis_passes::h5c1577ba8747ac80bfS
13: 0x10fca62bc - driver::driver::compile_input::h6cd958c13fa99356VVR
14: 0x10fd24ab5 - driver::run_compiler::h3464f6d73ed1e2efpUT
15: 0x10fd2328e - driver::run::closure.59750
16: 0x10fb3ab9b - task::TaskBuilder<S>::try_future::closure.39054
17: 0x10fb3aa93 - task::TaskBuilder<S>::spawn_internal::closure.39025
18: 0x10fafe7bd - task::NativeSpawner.Spawner::spawn::closure.2477
19: 0x11333b82c - rust_try_inner
20: 0x11333b816 - rust_try
21: 0x1132d6707 - unwind::try::h52975ec5962bbd4bmRc
22: 0x1132d659c - task::Task::run::h585d701e145fcc2392b
23: 0x10fafe5e3 - task::NativeSpawner.Spawner::spawn::closure.2401
24: 0x1132d7dd7 - thread::thread_start::hfcf722effb78e787foc
25: 0x7fff88b882fc - _pthread_body
26: 0x7fff88b88279 - _pthread_body

However, if you swap the order of the trait and impl it works.

Issue 2:
Not sure how to properly describe the bug, but this causes an ICE:

#![feature(associated_types)]

struct SimulationInfo;

impl SimulationInfo {
fn add_state<T: HasState>(&mut self, op: || -> <T as HasState>::State)
-> Option<&mut <T as HasState>::State> {
None
}
}

trait HasState {
type State;
}

Whereas this compiles:

#![feature(associated_types)]

struct SimulationInfo;

trait HasState {
type State;
}

impl SimulationInfo {
fn add_state<T: HasState>(&mut self, op: || -> <T as HasState>::State)
-> Option<&mut <T as HasState>::State> {
None
}
}

Failure:

error: internal compiler error: unexpected panic
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
task 'rustc' panicked at 'No def'n found for DefId { krate: 0, node: 33 } in tcx.impl_or_trait_items', /Users/rustbuild/src/rust-buildbot/slave/nightly-mac/build/src/librustc/middle/ty.rs:4066

stack backtrace:
1: 0x10d45a619 - rt::backtrace::imp::write::h03fee16d4a0b6b41moq
2: 0x10d45d85c - failure::on_fail::h3e0f6b3c6c4bbcc3VEq
3: 0x10d6bcf05 - unwind::begin_unwind_inner::h6c7f4532e72658d7SJd
4: 0x10d6bcb9f - unwind::begin_unwind_fmt::h9863b25c438d6314kHd
5: 0x10a408d50 - middle::ty::impl_or_trait_item::h8676078de6338b03J2J
6: 0x10a7fe51e - middle::typeck::collect::convert_methods::ty_of_method::h1b65fc29f839dd39kEi
7: 0x10a7a4b84 - middle::typeck::collect::convert::hf5d19782a9342fbfL7i
8: 0x10a79c993 - middle::typeck::collect::collect_item_types::h2af040048993f98298h
9: 0x10a1bb556 - util::common::time::h11920059333862041717
10: 0x10a965478 - middle::typeck::check_crate::h50fcc5c8b39993f4LVn
11: 0x10a9cdbcf - driver::driver::phase_3_run_analysis_passes::h1425a4ca465c7b097DA
12: 0x10a9c82b8 - driver::driver::compile_input::h60bc42ef7fabbfd4SkA
13: 0x10aa45ca8 - driver::run_compiler::h4031243f49082a9fw7D
14: 0x10aa43ece - driver::run::closure.145349
15: 0x10a1d381b - task::TaskBuilder<S>::try_future::closure.103709
16: 0x10a1d3713 - task::TaskBuilder<S>::spawn_internal::closure.103680
17: 0x10a15398d - task::NativeSpawner.Spawner::spawn::closure.8526
18: 0x10d72320c - rust_try_inner
19: 0x10d7231f6 - rust_try
20: 0x10d6ba677 - unwind::try::hab84862d0081b274cyd
21: 0x10d6ba50c - task::Task::run::h39093ecd59554b49ZJc
22: 0x10a1537b3 - task::NativeSpawner.Spawner::spawn::closure.8463
23: 0x10d6bbd37 - thread::thread_start::h589be8c0a398d299e5c
24: 0x7fff9260c2fc - _pthread_body
25: 0x7fff9260c279 - _pthread_body