<p dir="auto">Offending code:</p>
<div class="highlight highlight-source-rust notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="extern crate core;
use core::fmt;

fn show_all&lt;I: fmt::String&gt;(iter: &amp;mut Iterator&lt;Item=I&gt;) {
    for i in *iter {
        println!(&quot;{}&quot;, i);
    }
}

fn main() {
    let v = vec![1i32, 2, 3, 4];
    show_all(&amp;mut v.iter());
}"><pre class="notranslate"><span class="pl-k">extern</span> <span class="pl-k">crate</span> core<span class="pl-kos">;</span>
<span class="pl-k">use</span> core<span class="pl-kos">::</span>fmt<span class="pl-kos">;</span>

<span class="pl-k">fn</span> <span class="pl-en">show_all</span><span class="pl-kos">&lt;</span><span class="pl-smi">I</span><span class="pl-kos">:</span> fmt<span class="pl-kos">::</span><span class="pl-smi">String</span><span class="pl-kos">&gt;</span><span class="pl-kos">(</span><span class="pl-s1">iter</span><span class="pl-kos">:</span> <span class="pl-c1">&amp;</span><span class="pl-k">mut</span> <span class="pl-smi">Iterator</span><span class="pl-kos">&lt;</span><span class="pl-smi">Item</span>=<span class="pl-smi">I</span><span class="pl-kos">&gt;</span><span class="pl-kos">)</span> <span class="pl-kos">{</span>
    <span class="pl-k">for</span> i <span class="pl-k">in</span> <span class="pl-c1">*</span>iter <span class="pl-kos">{</span>
        <span class="pl-en">println</span><span class="pl-en">!</span><span class="pl-kos">(</span><span class="pl-s">"{}"</span>, i<span class="pl-kos">)</span><span class="pl-kos">;</span>
    <span class="pl-kos">}</span>
<span class="pl-kos">}</span>

<span class="pl-k">fn</span> <span class="pl-en">main</span><span class="pl-kos">(</span><span class="pl-kos">)</span> <span class="pl-kos">{</span>
    <span class="pl-k">let</span> v = <span class="pl-en">vec</span><span class="pl-en">!</span><span class="pl-kos">[</span><span class="pl-c1">1i32</span>, <span class="pl-c1">2</span>, <span class="pl-c1">3</span>, <span class="pl-c1">4</span><span class="pl-kos">]</span><span class="pl-kos">;</span>
    <span class="pl-en">show_all</span><span class="pl-kos">(</span><span class="pl-c1">&amp;</span><span class="pl-k">mut</span> v<span class="pl-kos">.</span><span class="pl-en">iter</span><span class="pl-kos">(</span><span class="pl-kos">)</span><span class="pl-kos">)</span><span class="pl-kos">;</span>
<span class="pl-kos">}</span></pre></div>
<p dir="auto">Compiler error (formatted):</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="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&lt;llvm::Value*&gt;, const llvm::Twine&amp;): 
Assertion `(i &gt;= FTy-&gt;getNumParams() || FTy-&gt;getParamType(i) == Args[i]-&gt;getType()) &amp;&amp; 
&quot;Calling a function with a bad signature!&quot;' failed."><pre class="notranslate"><code class="notranslate">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&lt;llvm::Value*&gt;, const llvm::Twine&amp;): 
Assertion `(i &gt;= FTy-&gt;getNumParams() || FTy-&gt;getParamType(i) == Args[i]-&gt;getType()) &amp;&amp; 
"Calling a function with a bad signature!"' failed.
</code></pre></div>
<p dir="auto">Rust version:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="$ rustc --version
rustc 1.0.0-nightly (f4f10dba2 2015-01-17 20:31:08 +0000)"><pre class="notranslate"><code class="notranslate">$ rustc --version
rustc 1.0.0-nightly (f4f10dba2 2015-01-17 20:31:08 +0000)
</code></pre></div>
<h3 dir="auto">Code</h3>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="fn changer&lt;'a&gt;(mut things: Box&lt;Iterator&lt;Item=&amp;'a mut u8&gt;&gt;) {
    for item in *things { *item = 0 }
}

fn main() {
}"><pre class="notranslate"><code class="notranslate">fn changer&lt;'a&gt;(mut things: Box&lt;Iterator&lt;Item=&amp;'a mut u8&gt;&gt;) {
    for item in *things { *item = 0 }
}

fn main() {
}
</code></pre></div>
<h3 dir="auto">Error</h3>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="error: internal compiler error: trying to take the sizing type of &lt;core::iter::Iterator + 'static as core::iter::Iterator&gt;::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&lt;Any&gt;', /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&lt;A, R&gt;::invoke::h17305763774885229909
  27:        0x10d2362d0 - rt::unwind::try::try_fn::h8419390306595151514
  28:        0x110b0dba9 - rust_try_inner
  29:        0x110b0db96 - rust_try
  30:        0x10d236a16 - thunk::F.Invoke&lt;A, R&gt;::invoke::h8115208835806211442
  31:        0x110a92154 - sys::thread::thread_start::hf32c2ee467ccc238CEv
  32:     0x7fff9663c2fc - _pthread_body
  33:     0x7fff9663c279 - _pthread_body"><pre class="notranslate"><code class="notranslate">error: internal compiler error: trying to take the sizing type of &lt;core::iter::Iterator + 'static as core::iter::Iterator&gt;::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&lt;Any&gt;', /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&lt;A, R&gt;::invoke::h17305763774885229909
  27:        0x10d2362d0 - rt::unwind::try::try_fn::h8419390306595151514
  28:        0x110b0dba9 - rust_try_inner
  29:        0x110b0db96 - rust_try
  30:        0x10d236a16 - thunk::F.Invoke&lt;A, R&gt;::invoke::h8115208835806211442
  31:        0x110a92154 - sys::thread::thread_start::hf32c2ee467ccc238CEv
  32:     0x7fff9663c2fc - _pthread_body
  33:     0x7fff9663c279 - _pthread_body
</code></pre></div>
<h3 dir="auto">Version</h3>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="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"><pre class="notranslate"><code class="notranslate">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
</code></pre></div>