Issue 1:
#![allow(dead_code)]

#[derive(Show)]
struct Cell;

struct Grid {
cols: [[Cell; 6]; 6]
}

impl Grid {
fn iter(&self) -> Box<Iterator<Item = &Cell>> {
Box::new(self.cols.iter().flat_map(|x| x.iter()))
}
fn fill(&mut self) {
for cell in *self.iter() {
println!("here's a cell: {:?}", cell);
}
}
}

fn main() {
}

Error and backtrace:

rustc: /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/llvm/lib/IR/Instructions.cpp:550: void llvm::InvokeInst::init(llvm::Value*, llvm::BasicBlock*, llvm::BasicBlock*, llvm::ArrayRef<llvm::Value*>, const llvm::Twine&): Assertion (i >= FTy->getNumParams() || FTy->getParamType(i) == Args[i]->getType()) && "Invoking a function with a bad signature!"' failed.`

Program received signal SIGABRT, Aborted.
[Switching to Thread 0x7fffefbff700 (LWP 4538)]
0x00007ffff711e107 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
56 ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0 0x00007ffff711e107 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#1 0x00007ffff711f4e8 in __GI_abort () at abort.c:89
#2 0x00007ffff7117226 in __assert_fail_base (fmt=0x7ffff724d968 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n",
assertion=assertion@entry=0x7ffff4bec220 "(i >= FTy->getNumParams() || FTy->getParamType(i) == Args[i]->getType()) && \"Invoking a function with a bad signature!\"",
file=file@entry=0x7ffff4bea228 "/home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/llvm/lib/IR/Instructions.cpp", line=line@entry=550,
function=function@entry=0x7ffff4beda20 <llvm::InvokeInst::init(llvm::Value*, llvm::BasicBlock*, llvm::BasicBlock*, llvm::ArrayRef<llvm::Value*>, llvm::Twine const&)::__PRETTY_FUNCTION__> "void llvm::InvokeInst::init(llvm::Value*, llvm::BasicBlock*, llvm::BasicBlock*, llvm::ArrayRef<llvm::Value*>, const llvm::Twine&)") at assert.c:92
#3 0x00007ffff71172d2 in __GI___assert_fail (assertion=0x7ffff4bec220 "(i >= FTy->getNumParams() || FTy->getParamType(i) == Args[i]->getType()) && \"Invoking a function with a bad signature!\"",
file=0x7ffff4bea228 "/home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/llvm/lib/IR/Instructions.cpp", line=550,
function=0x7ffff4beda20 <llvm::InvokeInst::init(llvm::Value*, llvm::BasicBlock*, llvm::BasicBlock*, llvm::ArrayRef<llvm::Value*>, llvm::Twine const&)::__PRETTY_FUNCTION__> "void llvm::InvokeInst::init(llvm::Value*, llvm::BasicBlock*, llvm::BasicBlock*, llvm::ArrayRef<llvm::Value*>, const llvm::Twine&)") at assert.c:101
#4 0x00007ffff419be6d in llvm::InvokeInst::init(llvm::Value*, llvm::BasicBlock*, llvm::BasicBlock*, llvm::ArrayRef<llvm::Value*>, llvm::Twine const&) () from /usr/local/lib/librustc_llvm-4e7c5e5c.so
#5 0x00007ffff319a6e1 in llvm::IRBuilder<true, llvm::ConstantFolder, llvm::IRBuilderDefaultInserter<true> >::CreateInvoke(llvm::Value*, llvm::BasicBlock*, llvm::BasicBlock*, llvm::ArrayRef<llvm::Value*>, llvm::Twine const&) ()
from /usr/local/lib/librustc_llvm-4e7c5e5c.so
#6 0x00007ffff40e28ce in LLVMBuildInvoke () from /usr/local/lib/librustc_llvm-4e7c5e5c.so
#7 0x00007ffff6569050 in trans::base::invoke::h4cd8ec174fe38a29DTs () from /usr/local/lib/librustc_trans-4e7c5e5c.so
#8 0x00007ffff65dcba1 in trans::callee::trans_call_inner::h2302436840455011871 () from /usr/local/lib/librustc_trans-4e7c5e5c.so
#9 0x00007ffff65a4bc0 in trans::expr::trans_rvalue_stmt_unadjusted::h3e17f3a20f297c29BMi () from /usr/local/lib/librustc_trans-4e7c5e5c.so
#10 0x00007ffff6553bbe in trans::expr::trans_into::ha60adcbe08fa3bdbKyh () from /usr/local/lib/librustc_trans-4e7c5e5c.so
#11 0x00007ffff65545d1 in trans::controlflow::trans_block::hdd6a1a94b7524b90B3d () from /usr/local/lib/librustc_trans-4e7c5e5c.so
#12 0x00007ffff66226ad in trans::base::trans_closure::h1947fd5123bfe895EYt () from /usr/local/lib/librustc_trans-4e7c5e5c.so
#13 0x00007ffff653ede7 in trans::base::trans_fn::h5d061f11fc4ac1e7j9t () from /usr/local/lib/librustc_trans-4e7c5e5c.so
#14 0x00007ffff653b00f in trans::base::trans_item::h34ec82732f0498f3Ewu () from /usr/local/lib/librustc_trans-4e7c5e5c.so
#15 0x00007ffff6628dad in trans::base::trans_crate::he5ffa45aaa619f67lsv () from /usr/local/lib/librustc_trans-4e7c5e5c.so
#16 0x00007ffff7aef844 in driver::phase_4_translate_to_llvm::h98aea3c7bb04643bPFa () from /usr/local/lib/librustc_driver-4e7c5e5c.so
#17 0x00007ffff7acb49d in driver::compile_input::h04aea004c559b910xba () from /usr/local/lib/librustc_driver-4e7c5e5c.so
#18 0x00007ffff7b9a96a in monitor::unboxed_closure.22497 () from /usr/local/lib/librustc_driver-4e7c5e5c.so
#19 0x00007ffff7b98f82 in thunk::F.Invoke$LT$A$C$$u{20}R$GT$::invoke::h11849311349984608396 () from /usr/local/lib/librustc_driver-4e7c5e5c.so
#20 0x00007ffff7b97c6f in rt::unwind::try::try_fn::h13617610205470131813 () from /usr/local/lib/librustc_driver-4e7c5e5c.so
#21 0x00007ffff76196c9 in rust_try_inner () from /usr/local/lib/libstd-4e7c5e5c.so
#22 0x00007ffff76196b6 in rust_try () from /usr/local/lib/libstd-4e7c5e5c.so
#23 0x00007ffff7b98386 in thunk::F.Invoke$LT$A$C$$u{20}R$GT$::invoke::h14452289732390470265 () from /usr/local/lib/librustc_driver-4e7c5e5c.so
#24 0x00007ffff75a19b2 in sys::thread::thread_start::h93b0d38960a9fcacqrw () from /usr/local/lib/libstd-4e7c5e5c.so
#25 0x00007ffff1b510a4 in start_thread (arg=0x7fffefbff700) at pthread_create.c:309
#26 0x00007ffff71ceccd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

rustc 1.0.0-nightly (44a287e6e 2015-01-08 17:03:40 -0800)
binary: rustc
commit-hash: 44a287e6eb22ec3c2a687fc156813577464017f7
commit-date: 2015-01-08 17:03:40 -0800
host: x86_64-unknown-linux-gnu
release: 1.0.0-nightly

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