Issue 1:
Offending code:

extern crate core;
use core::fmt;

fn show_all<I: fmt::String>(iter: &mut Iterator<Item=I>) {
for i in *iter {
println!("{}", i);
}
}

fn main() {
let v = vec![1i32, 2, 3, 4];
show_all(&mut v.iter());
}

Compiler error (formatted):

rustc: /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/llvm/lib/IR/Instructions.cpp:281:
void llvm::CallInst::init(llvm::Value*, llvm::ArrayRef<llvm::Value*>, const llvm::Twine&):
Assertion `(i >= FTy->getNumParams() || FTy->getParamType(i) == Args[i]->getType()) &&
"Calling a function with a bad signature!"' failed.

Rust version:

$ rustc --version
rustc 1.0.0-nightly (f4f10dba2 2015-01-17 20:31:08 +0000)

Issue 2:
Code

fn changer<'a>(mut things: Box<Iterator<Item=&'a mut u8>>) {
for item in *things { *item = 0 }
}

fn main() {
}

Error

error: internal compiler error: trying to take the sizing type of <core::iter::Iterator + 'static as core::iter::Iterator>::Item, an unsized type
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>', /Users/shep/Projects/rust/src/libsyntax/diagnostic.rs:182

stack backtrace:
1: 0x110a80d05 - sys::backtrace::write::h57cb71e45a6ad05bARs
2: 0x110aa667f - failure::on_fail::h1e60313e5a552ea32Ty
3: 0x110a0bb6a - rt::unwind::begin_unwind_inner::h591d6980cb1eb9bb2By
4: 0x10e753937 - rt::unwind::begin_unwind::h15926596774839260564
5: 0x10e7542a8 - diagnostic::Handler::bug::h4055c4ca2e17f0c6DLF
6: 0x10dd63cb8 - session::Session::bug::h5d1941c792f1e4caroq
7: 0x10d326a23 - trans::type_of::sizing_type_of::hded88082b54ddc4bgSo
8: 0x10d4422eb - trans::adt::represent_type_uncached::h5d90b81a92acc1b47xH
9: 0x10d320cd3 - trans::adt::represent_type::hdeb853742a302b7fHuH
10: 0x10d30c662 - trans::type_of::type_of::h0a1f71fc9850898aYYo
11: 0x10d30c34c - trans::type_of::type_of::h0a1f71fc9850898aYYo
12: 0x10d3b803f - trans::type_of::type_of_rust_fn::hf6b24d412c4c9582xOo
13: 0x10d41665c - trans::meth::trans_trait_callee_from_llval::h2aa4e324f7a786d6kwz
14: 0x10d413a56 - trans::meth::trans_object_shim::hfa24eaa4bec56008jBz
15: 0x10d31eb5f - trans::meth::trans_method_callee::hce96e8ac9be0c90eq6y
16: 0x10d385573 - trans::callee::trans_call_inner::h12246188759747685167
17: 0x10d354691 - trans::expr::trans_rvalue_stmt_unadjusted::hd58bf8791601bef4kQi
18: 0x10d306c8d - trans::expr::trans_into::h8bab20af1840b0a57xh
19: 0x10d307605 - trans::controlflow::trans_block::h051994b75eb2405cS1d
20: 0x10d3d0f44 - trans::base::trans_closure::hb694bfd51133ec9fMSt
21: 0x10d2f2a2b - trans::base::trans_fn::h816a9b6a32db67faj3t
22: 0x10d2ee086 - trans::base::trans_item::h223cbaffa1a561c6aqu
23: 0x10d3d8718 - trans::base::trans_crate::h7f75c26047f82847vlv
24: 0x10d19064e - driver::phase_4_translate_to_llvm::h17f0f28873e0c2d6uFa
25: 0x10d172501 - driver::compile_input::h059943f6c48c38c7vba
26: 0x10d239173 - thunk::F.Invoke<A, R>::invoke::h17305763774885229909
27: 0x10d2362d0 - rt::unwind::try::try_fn::h8419390306595151514
28: 0x110b0dba9 - rust_try_inner
29: 0x110b0db96 - rust_try
30: 0x10d236a16 - thunk::F.Invoke<A, R>::invoke::h8115208835806211442
31: 0x110a92154 - sys::thread::thread_start::hf32c2ee467ccc238CEv
32: 0x7fff9663c2fc - _pthread_body
33: 0x7fff9663c279 - _pthread_body

Version

rustc 0.13.0-dev (5773bdeff 2015-01-04 21:36:41 +0000)
binary: rustc
commit-hash: 5773bdefff2e47cc007f5cc2af3f80b30303d45a
commit-date: 2015-01-04 21:36:41 +0000
host: x86_64-apple-darwin
release: 0.13.0-dev