Issue 1:
[ruben@MacBook-Pro src]$ rustc --version=verbose
rustc 0.13.0-nightly (40fb87d40 2014-11-10 23:01:57 +0000)
binary: rustc
commit-hash: 40fb87d40f681f5356af42175fc7b85da387f037
commit-date: 2014-11-10 23:01:57 +0000
host: x86_64-apple-darwin
release: 0.13.0-nightly

trait Adder<Number> {
fn sum(&self, summands: &[Number]) -> Number;
}

struct Calculator {
foo: int,
}

impl Adder<int> for Calculator {

fn sum(&self, summands: &[int]) -> int {
println!("sum int");
let mut result = 0i;
for num in summands.iter() {
result += *num;
}
result
}
}

impl Adder<f32> for Calculator {

fn sum(&self, summands: &[f32]) -> f32 {
println!("sum f32");
let mut result = 0f32;
for num in summands.iter() {
result += *num;
}
result
}
}

fn main() {
let calc = Calculator { foo: 4711 };
println!("1 + 1 = {}", calc.sum([1,1].as_slice()));

// raises the compiler error
println!("1.0 + 2.3 = {}", calc.sum([1.0,2.3].as_slice()));
// compiles and runs properly
//println!("1.0 + 2.3 = {}", calc.sum([1.0f32,2.3f32].as_slice()));
}

error: internal compiler error: Impl DefId { krate: 0, node: 26 }:Calculator.Adder<int> was matchable against Obligation(trait_ref=<_ : Adder<_>>,depth=0) but now is not
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 'Box<Any>', /Users/rustbuild/src/rust-buildbot/slave/nightly-mac/build/src/libsyntax/diagnostic.rs:175

stack backtrace:
1: 0x11011e01f - rt::backtrace::imp::write::h37f6e30fade15cb76mt
2: 0x1101211a7 - failure::on_fail::h4075de659ea4adb9VDt
3: 0x1103a4415 - unwind::begin_unwind_inner::h9e12d6856ac2af42j1c
4: 0x10e086757 - unwind::begin_unwind::h887212781071489879
5: 0x10e086f93 - diagnostic::Handler::bug::he58e2d0573e8d5d4L5F
6: 0x10d105271 - middle::traits::select::SelectionContext<'cx, 'tcx>::rematch_impl::h35320cfc53204d2fFbZ
7: 0x10d0f3607 - middle::traits::select::SelectionContext<'cx, 'tcx>::confirm_candidate::hb7278faaf8bd08bdDRY
8: 0x10d0ea1b7 - middle::traits::select::SelectionContext<'cx, 'tcx>::select::h20d24e63da941032znX
9: 0x10d0e8e86 - middle::traits::fulfill::FulfillmentContext::select::h4f9eb03bbb3d4aa6gUW
10: 0x10d0e8656 - middle::traits::fulfill::FulfillmentContext::select_where_possible::h212cad5c41e6ff5evTW
11: 0x10d0014d2 - middle::traits::fulfill::FulfillmentContext::select_all_or_error::ha09a57d720916db7iRW
12: 0x10d26dc78 - middle::typeck::check::vtable::select_all_fcx_obligations_or_error::h4291cb6f90f0ee15K7N
13: 0x10d2c5ccb - middle::typeck::check::check_bare_fn::hec13c0cf792a848da8V
14: 0x10d2c1e1d - middle::typeck::check::check_item::h7dd222d42ec19845jsW
15: 0x10d2c5b10 - middle::typeck::check::check_item_types::hdbb49e408a7799c1k7V
16: 0x10cdd1156 - util::common::time::h3942551398258420223
17: 0x10d5d1eee - middle::typeck::check_crate::hcb0ab152bef1200chup
18: 0x10d639d9f - driver::driver::phase_3_run_analysis_passes::hc02fc7265031485eIdC
19: 0x10d634bd8 - driver::driver::compile_input::h2ba3685ec9df4f6btUB
20: 0x10d6b23ed - driver::run_compiler::h6e93cd8bbb72fd50KKF
21: 0x10d6b092e - driver::run::closure.146334
22: 0x10cde940b - task::TaskBuilder<S>::try_future::closure.104770
23: 0x10cde9303 - task::TaskBuilder<S>::spawn_internal::closure.104741
24: 0x10cda27bd - task::NativeSpawner.Spawner::spawn::closure.2551
25: 0x110402a0c - rust_try_inner
26: 0x1104029f6 - rust_try
27: 0x1103a1be7 - unwind::try::h009a35089a5882701Pc
28: 0x1103a1a7c - task::Task::run::h4878cb7b665069bf61b
29: 0x10cda25e3 - task::NativeSpawner.Spawner::spawn::closure.2475
30: 0x1103a32a7 - thread::thread_start::h8e83ad43ae75daab3mc
31: 0x7fff914642fc - _pthread_body
32: 0x7fff91464279 - _pthread_body

Issue 2:
The simplified code below results in an ICE using the following rust version

rustc 1.0.0-beta (9854143 2015-04-02) (built 2015-04-02)

binary: rustc

commit-hash: 9854143

commit-date: 2015-04-02

build-date: 2015-04-02

host: x86_64-apple-darwin

release: 1.0.0-beta

---- CODE resulting in ICE -------

use std::f64;
use std::fs::File;
use std::io::{BufRead, BufReader};

#[derive(Default)]
struct Output {
count: i64,
min: f64,
max: f64,
var: f64,
qk: f64, // helper variables for
mk: f64, // variance calculation
}

fn main() {
let file = File::open("data_random_small.txt");
let buf = BufReader::new(file.unwrap());
let out = compute_statistics(buf);
}

// compute_statistics computes basic statistics for the content of the
// provided BufReader
fn compute_statistics(buf: BufReader<File>) -> Output {
let mut out = Output { count: 0, min: f64::MAX, max: -f64::MAX, var: 0.0,
qk: 0.0, mk: 0.0};
for line_r in buf.lines() {
let line = line_r.unwrap();
let n_r = line.to_string().parse::<f64>();
let n = n_r.unwrap();

// update variance
let k: f64 = out.count as f64;
out.qk += (k - 1.0) * (n - out.mk) * (n - out.mk) / k;
out.mk += (n - out.mk) / k;

out.count += 1;
}
let k: f64 = out.count as f64;
out.var = out.qk / (k-1);
out
}

The issue appears to be the second to last line. The compiler should reject (k-1). Changing this to

out.var = out.qk / (k-1.0);

results in proper compilation. Also, removing the previous scope of the for loop works and the compiler then properly complains about the (k-1) bit. Below is the backtrace:

----- BACKTRACE ----

error: internal compiler error: Impl DefId { krate: 2, node: 39365 } was matchable against Obligation(predicate=Binder(TraitPredicate(core::ops::Sub<_>)),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>', /Users/rustbuild/src/rust-buildbot/slave/beta-dist-rustc-mac/build/src/libsyntax/diagnostic.rs:190

stack backtrace:
1: 0x107943f77 - sys::backtrace::write::h799ab135045ca9ca1LC
2: 0x107971e4d - panicking::on_panic::h9502e488a92fc8bcHAI
3: 0x1078962de - rt::unwind::begin_unwind_inner::hf0537788ee16eadbiiI
4: 0x1070755ae - rt::unwind::begin_unwind::h447731439410619827
5: 0x107075df9 - diagnostic::Handler::bug::hb6bac6e14e70580aZsB
6: 0x104b9c3be - middle::traits::select::SelectionContext<'cx, 'tcx>::rematch_impl::h00902254f92fe252QxT
7: 0x104b9bd08 - middle::infer::InferCtxt<'a, 'tcx>::commit_if_ok::h14474907185931287891
8: 0x104b7ce94 - middle::traits::select::SelectionContext<'cx, 'tcx>::confirm_candidate::h3f1d070f70ab815cMPS
9: 0x104b509c6 - middle::traits::select::SelectionContext<'cx, 'tcx>::select::hc528f249f6251cb8OQQ
10: 0x104b6098a - middle::traits::project::project_type::h7ca468ea33bc79f1AwP
11: 0x104b5e367 - middle::traits::project::opt_normalize_projection_type::h766518f8b1310230cpP
12: 0x104b57d86 - middle::traits::project::poly_project_and_unify_type::closure.83535
13: 0x104b55bc0 - middle::traits::project::poly_project_and_unify_type::h44012951a95c13e5l5O
14: 0x104b4d206 - middle::traits::fulfill::FulfillmentContext<'tcx>::select::h7d8cf023413c2180uHO
15: 0x104b4c848 - middle::traits::fulfill::FulfillmentContext<'tcx>::select_where_possible::h0397a49aa695a23cIGO
16: 0x103efa433 - check::vtable::select_fcx_obligations_where_possible::h99330aa4e9f6a658d4b
17: 0x103f3448d - check::FnCtxt<'a, 'tcx>::resolve_type_vars_if_possible::h7c8e59ec20a8f3b2qYo
18: 0x103fb0a3e - check::op::check_binop::h7e7f29a781258fb2u5m
19: 0x10400878d - check::check_expr_with_unifier::h13696137427352880546
20: 0x103ff552c - check::check_expr_with_unifier::h7970691808293538245
21: 0x103fb0a33 - check::op::check_binop::h7e7f29a781258fb2u5m
22: 0x103ff43c3 - check::check_expr_with_unifier::h7970691808293538245
23: 0x10400fab9 - check::check_expr_with_unifier::h6698900367440735538
24: 0x103fbe705 - check::check_block_with_expected::h60bff5b1f9d55793fps
25: 0x103f9ae05 - check::check_fn::h410d0ffafb47f675l1n
26: 0x103fb932e - check::check_bare_fn::h05c77be534ada2cfUQn
27: 0x103fb2ee2 - check::check_item::h9d89bedf29e4fe82F9n
28: 0x10408f676 - check_crate::closure.36302
29: 0x104089ae7 - check_crate::h09aa7856a322fd44bwC
30: 0x103da9355 - driver::phase_3_run_analysis_passes::h1af60e7c926ca39dgGa
31: 0x103d8da85 - driver::compile_input::h27cf4320fd56e5cbQba
32: 0x103e4ba15 - run_compiler::h93c68a2a3c26052bV4b
33: 0x103e491e2 - boxed::F.FnBox<A>::call_box::h4498816167135712709
34: 0x103e486d7 - rt::unwind::try::try_fn::h2387014819904265058
35: 0x1079fbea8 - rust_try_inner
36: 0x1079fbe95 - rust_try
37: 0x103e489ca - boxed::F.FnBox<A>::call_box::h4850138824497903476
38: 0x10795b37d - sys::thread::create::thread_start::h42d6d904fce5365aihH
39: 0x7fff82bc6267 - _pthread_body
40: 0x7fff82bc61e4 - _pthread_start