Issue 1:
Here's the backtrace. Let me know if the code I was compiling would be helpful, I tagged the rev locally.

rustc 1.1.0-nightly (7bd71637c 2015-05-06) (built 2015-05-06)

$ RUST_BACKTRACE=1 cargo test
Compiling dumbmath v0.1.6 (file:///home/nicholasbishop/dumbmath)
error: internal compiler error: Impl DefId { krate: 2, node: 26942 } was matchable against Obligation(predicate=Binder(TraitPredicate(<f32 as core::ops::Div<_>>)),depth=1) but now is not
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
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:230

stack backtrace:
1: 0x7fbee3ae6f89 - sys::backtrace::write::h89d94970ae1bc478fhs
2: 0x7fbee3aeef09 - panicking::on_panic::h314cddb0409059cbkXw
3: 0x7fbee3aaf0f2 - rt::unwind::begin_unwind_inner::hd6748515f1d9c0b2uCw
4: 0x7fbee0e85fbd - rt::unwind::begin_unwind::h9184602946677297306
5: 0x7fbee0e8667b - diagnostic::Handler::bug::h6d48c8060c15a3b4a2B
6: 0x7fbee1c36304 - middle::traits::select::SelectionContext<'cx, 'tcx>::rematch_impl::h10b0cc0f4e83f0c3EuT
7: 0x7fbee1c35c2f - middle::infer::InferCtxt<'a, 'tcx>::commit_if_ok::h17325861492725920879
8: 0x7fbee1c1c8a5 - middle::traits::select::SelectionContext<'cx, 'tcx>::confirm_candidate::hca3234a85605343cUMS
9: 0x7fbee1afacc5 - middle::traits::select::SelectionContext<'cx, 'tcx>::select::hec5ba022f7c648beiPQ
10: 0x7fbee1c09d35 - middle::traits::project::project_type::h74992cfacc671364CwP
11: 0x7fbee1c0896b - middle::traits::project::opt_normalize_projection_type::ha8866d0a50189fbcepP
12: 0x7fbee1c0599f - middle::traits::project::project_and_unify_type::h1300a4d0fa05187d87O
13: 0x7fbee1c03970 - middle::infer::InferCtxt<'a, 'tcx>::commit_if_ok::h107823834106425565
14: 0x7fbee1bfb888 - middle::traits::fulfill::FulfillmentContext<'tcx>::select::hec0877a5f2e11ad0HHO
15: 0x7fbee1bfb29b - middle::traits::fulfill::FulfillmentContext<'tcx>::select_where_possible::h301bc31d4e510c07VGO
16: 0x7fbee323d048 - check::vtable::select_fcx_obligations_where_possible::h72b84a124c3a5b40I6b
17: 0x7fbee325914a - check::FnCtxt<'a, 'tcx>::resolve_type_vars_if_possible::h74b2cbbcdf641686cPo
18: 0x7fbee32b674e - check::op::check_binop::hba99f04615a48d79oYm
19: 0x7fbee32ec9cd - check::check_expr_with_unifier::h12689752184703274217
20: 0x7fbee3312c4b - check::check_decl_local::h28a2e7870f672b04j7r
21: 0x7fbee32c23f1 - check::check_block_with_expected::h212bdec46f615ac8pds
22: 0x7fbee32a7f36 - check::check_fn::h225bdd7ece966e55lSn
23: 0x7fbee32bde27 - check::check_bare_fn::h8fed7360af87b5cbUHn
24: 0x7fbee32c980c - check::check_method_body::h225a8a268d0d1168Ujo
25: 0x7fbee32bbd85 - check::CheckItemBodiesVisitor<'a, 'tcx>.Visitor<'tcx>::visit_item::hb0162b7f82578cf4XEn
26: 0x7fbee32bc1bf - check::CheckItemBodiesVisitor<'a, 'tcx>.Visitor<'tcx>::visit_item::hb0162b7f82578cf4XEn
27: 0x7fbee3376c4a - check_crate::closure.38730
28: 0x7fbee336ff80 - check_crate::hed85a8a5c9342eb05CC
29: 0x7fbee4035c28 - driver::phase_3_run_analysis_passes::he0b331c645c77cdbtGa
30: 0x7fbee401705c - driver::compile_input::h763ead6090436e8fQba
31: 0x7fbee40cfeb1 - run_compiler::h711c4a29f8d270a365b
32: 0x7fbee40cd702 - boxed::F.FnBox<A>::call_box::h12199818508070417299
33: 0x7fbee40cccc9 - rt::unwind::try::try_fn::h5660428370877252098
34: 0x7fbee3b62898 - rust_try_inner
35: 0x7fbee3b62885 - rust_try
36: 0x7fbee40ccf64 - boxed::F.FnBox<A>::call_box::h5514408293737026672
37: 0x7fbee3aedca1 - sys::thread::Thread::new::thread_start::hfd3ca3d51ffcfe41QIv
38: 0x7fbeddb82529 - start_thread
39: 0x7fbee374022c - __clone
40: 0x0 - <unknown>

Build failed, waiting for other jobs to finish...
error: internal compiler error: Impl DefId { krate: 2, node: 26942 } was matchable against Obligation(predicate=Binder(TraitPredicate(<f32 as core::ops::Div<_>>)),depth=1) but now is not
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
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:230

stack backtrace:
1: 0x7f920f378f89 - sys::backtrace::write::h89d94970ae1bc478fhs
2: 0x7f920f380f09 - panicking::on_panic::h314cddb0409059cbkXw
3: 0x7f920f3410f2 - rt::unwind::begin_unwind_inner::hd6748515f1d9c0b2uCw
4: 0x7f920c717fbd - rt::unwind::begin_unwind::h9184602946677297306
5: 0x7f920c71867b - diagnostic::Handler::bug::h6d48c8060c15a3b4a2B
6: 0x7f920d4c8304 - middle::traits::select::SelectionContext<'cx, 'tcx>::rematch_impl::h10b0cc0f4e83f0c3EuT
7: 0x7f920d4c7c2f - middle::infer::InferCtxt<'a, 'tcx>::commit_if_ok::h17325861492725920879
8: 0x7f920d4ae8a5 - middle::traits::select::SelectionContext<'cx, 'tcx>::confirm_candidate::hca3234a85605343cUMS
9: 0x7f920d38ccc5 - middle::traits::select::SelectionContext<'cx, 'tcx>::select::hec5ba022f7c648beiPQ
10: 0x7f920d49bd35 - middle::traits::project::project_type::h74992cfacc671364CwP
11: 0x7f920d49a96b - middle::traits::project::opt_normalize_projection_type::ha8866d0a50189fbcepP
12: 0x7f920d49799f - middle::traits::project::project_and_unify_type::h1300a4d0fa05187d87O
13: 0x7f920d495970 - middle::infer::InferCtxt<'a, 'tcx>::commit_if_ok::h107823834106425565
14: 0x7f920d48d888 - middle::traits::fulfill::FulfillmentContext<'tcx>::select::hec0877a5f2e11ad0HHO
15: 0x7f920d48d29b - middle::traits::fulfill::FulfillmentContext<'tcx>::select_where_possible::h301bc31d4e510c07VGO
16: 0x7f920eacf048 - check::vtable::select_fcx_obligations_where_possible::h72b84a124c3a5b40I6b
17: 0x7f920eaeb14a - check::FnCtxt<'a, 'tcx>::resolve_type_vars_if_possible::h74b2cbbcdf641686cPo
18: 0x7f920eb4874e - check::op::check_binop::hba99f04615a48d79oYm
19: 0x7f920eb7e9cd - check::check_expr_with_unifier::h12689752184703274217
20: 0x7f920eba4c4b - check::check_decl_local::h28a2e7870f672b04j7r
21: 0x7f920eb543f1 - check::check_block_with_expected::h212bdec46f615ac8pds
22: 0x7f920eb39f36 - check::check_fn::h225bdd7ece966e55lSn
23: 0x7f920eb4fe27 - check::check_bare_fn::h8fed7360af87b5cbUHn
24: 0x7f920eb5b80c - check::check_method_body::h225a8a268d0d1168Ujo
25: 0x7f920eb4dd85 - check::CheckItemBodiesVisitor<'a, 'tcx>.Visitor<'tcx>::visit_item::hb0162b7f82578cf4XEn
26: 0x7f920eb4e1bf - check::CheckItemBodiesVisitor<'a, 'tcx>.Visitor<'tcx>::visit_item::hb0162b7f82578cf4XEn
27: 0x7f920ec08c4a - check_crate::closure.38730
28: 0x7f920ec01f80 - check_crate::hed85a8a5c9342eb05CC
29: 0x7f920f8c7c28 - driver::phase_3_run_analysis_passes::he0b331c645c77cdbtGa
30: 0x7f920f8a905c - driver::compile_input::h763ead6090436e8fQba
31: 0x7f920f961eb1 - run_compiler::h711c4a29f8d270a365b
32: 0x7f920f95f702 - boxed::F.FnBox<A>::call_box::h12199818508070417299
33: 0x7f920f95ecc9 - rt::unwind::try::try_fn::h5660428370877252098
34: 0x7f920f3f4898 - rust_try_inner
35: 0x7f920f3f4885 - rust_try
36: 0x7f920f95ef64 - boxed::F.FnBox<A>::call_box::h5514408293737026672
37: 0x7f920f37fca1 - sys::thread::Thread::new::thread_start::hfd3ca3d51ffcfe41QIv
38: 0x7f9209414529 - start_thread
39: 0x7f920efd222c - __clone
40: 0x0 - <unknown>

Could not compile `dumbmath`.

Issue 2:
I got an internal compiler error when cargo testing my code, and I was unfortunately unable to reproduce on a small sample. The code is here on Github, to reproduce the error, change the literal on one line in test from 42.0 to 42.

$ rustc --version --verbose
rustc 1.0.0-nightly (522d09dfe 2015-02-19) (built 2015-02-21)
binary: rustc
commit-hash: 522d09dfecbeca1595f25ac58c6d0178bbd21d7d
commit-date: 2015-02-19
build-date: 2015-02-21
host: i686-unknown-linux-gnu
release: 1.0.0-nightly
$ RUST_BACKTRACE=1 cargo test --verbose
Compiling spiral v0.0.1 (file:///[...]/spiral)
Running `rustc src/main.rs --crate-name spiral --crate-type bin -g --test -C metadata=1ade813d3d860ac1 -C extra-filename=-1ade813d3d860ac1 --out-dir [...]/spiral/target --emit=dep-info,link -L dependency=[...]/spiral/target -L dependency=[...]/spiral/target/deps`
error: internal compiler error: Impl DefId { krate: 2, node: 74181 } was matchable against Obligation(predicate=Binder(TraitPredicate(core::cmp::PartialEq<_>)),depth=1) but now is not
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
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:189

stack backtrace:
1: 0xb7231280 - sys::backtrace::write::hb58c665617e5cee2KlC
2: 0xb725b8b0 - panicking::on_panic::hd4d4fc652390cdd8tXL
3: 0xb7195ac0 - rt::unwind::begin_unwind_inner::h6797c7a781aac698RBL
4: 0xb5656fd0 - rt::unwind::begin_unwind::h13117811778590822301
5: 0xb5657800 - diagnostic::Handler::bug::h0b9167776bd8dc1aw4E
6: 0xb61b5310 - middle::traits::select::SelectionContext<'cx, 'tcx>::rematch_impl::h7f3f2e654c4ffad9kHU
7: 0xb61b4c30 - middle::infer::InferCtxt<'a, 'tcx>::try::h13523729267676866609
8: 0xb619dd90 - middle::traits::select::SelectionContext<'cx, 'tcx>::confirm_candidate::ha4efb7af28b19263S8T
9: 0xb61784f0 - middle::traits::select::SelectionContext<'cx, 'tcx>::select::h5394e35b0e7c70a6lhS
10: 0xb6174160 - middle::traits::fulfill::FulfillmentContext<'tcx>::select::hbef8233dc9336219B0P
11: 0xb6173ac0 - middle::traits::fulfill::FulfillmentContext<'tcx>::select_where_possible::hbd71b9b88c61613cHZP
12: 0xb6cdddc0 - check::vtable::select_fcx_obligations_where_possible::hffd3ec74dffa624eVRb
13: 0xb6d1a6f0 - check::FnCtxt<'a, 'tcx>::resolve_type_vars_if_possible::he1da80c3c9c1dda2rJo
14: 0xb6cca360 - check::structurally_resolved_type::hb6535b94e7bbe37bNPt
15: 0xb6e00220 - check::check_expr_with_unifier::h9614455191220309796
16: 0xb6dbad90 - check::check_expr_with_unifier::check_binop::hbf8de0ab08b2ba09JMq
17: 0xb6df3370 - check::check_expr_with_unifier::h6092115828992963581
18: 0xb6dd9240 - check::check_expr_with_unifier::h3884107362083173097
19: 0xb6dbad90 - check::check_expr_with_unifier::check_binop::hbf8de0ab08b2ba09JMq
20: 0xb6df3370 - check::check_expr_with_unifier::h6092115828992963581
21: 0xb6df3370 - check::check_expr_with_unifier::h6092115828992963581
22: 0xb6dd9240 - check::check_expr_with_unifier::h3884107362083173097
23: 0xb6dd0200 - check::check_expr_with_unifier::check_then_else::h483da0d6a4f3eab2MEq
24: 0xb6decc20 - check::check_expr_with_unifier::h17365000147061483630
25: 0xb6da6d80 - check::check_block_with_expected::hf29cd5d4f1823991zys
26: 0xb6decc20 - check::check_expr_with_unifier::h17365000147061483630
27: 0xb6ccafe0 - check::_match::check_match::closure.29042
28: 0xb6ccac10 - check::_match::check_match::h77807f1365a779d3V1a
29: 0xb6decc20 - check::check_expr_with_unifier::h17365000147061483630
30: 0xb6da6d80 - check::check_block_with_expected::hf29cd5d4f1823991zys
31: 0xb6df9ad0 - check::check_expr_with_unifier::h14838318111108599859
32: 0xb6da6d80 - check::check_block_with_expected::hf29cd5d4f1823991zys
33: 0xb6d85a80 - check::check_fn::h9733b23b5bb31869JKn
34: 0xb6da3700 - check::check_bare_fn::hc0a904b0aabec0a4Wzn
35: 0xb6d9aa00 - check::check_item::heaa17bb09891b8a9nTn
36: 0xb6da19f0 - visit::walk_item::h334270929839752142
37: 0xb6da19f0 - visit::walk_item::h334270929839752142
38: 0xb6da19f0 - visit::walk_item::h334270929839752142
39: 0xb6e7f750 - check_crate::closure.35867
40: 0xb6e78b60 - check_crate::h74f1efb9c9ad0cecVjC
41: 0xb769c480 - driver::phase_3_run_analysis_passes::ha81485be033381d8gHa
42: 0xb7680c20 - driver::compile_input::h55e2c5089100dcc0Gba
43: 0xb7760430 - run_compiler::h7c1df0ae32ef6a57Zbc
44: 0xb775e810 - thunk::F.Invoke<A, R>::invoke::h4956589150906656218
45: 0xb775d680 - rt::unwind::try::try_fn::h3108213307196454525
46: 0xb72d5b30 - rust_try_inner
47: 0xb72d5b00 - rust_try
48: 0xb775d9b0 - thunk::F.Invoke<A, R>::invoke::h9387302087009601825
49: 0xb72474c0 - sys::thread::thread_start::hb380b1da46a95e5393G
50: 0xb2f29ea0 - start_thread
51: 0xb7049502 - clone
52: 0x0 - <unknown>

Could not compile `spiral`.

Caused by:
Process didn't exit successfully: `rustc src/main.rs --crate-name spiral --crate-type bin -g --test -C metadata=1ade813d3d860ac1 -C extra-filename=-1ade813d3d860ac1 --out-dir [...]/spiral/target --emit=dep-info,link -L dependency=[...]/spiral/target -L dependency=[...]/spiral/target/deps` (status=101)

I am sorry for such a crude report, but I could not come with a better sample, as the origin of the error is a bit unclear to me.