<p dir="auto">Hi, I used vec! the wrong way, and the compiler panicked.<br>
rustc -V -&gt; rustc 1.0.0-dev (built 2015-05-17)</p>
<p dir="auto">Sorry, if this is a dup, I looked but did not see a report of this.</p>
<div class="highlight highlight-source-rust notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="fn main() {
    vec!([]);
    println!(&quot;Hello, world!&quot;);
}"><pre class="notranslate"><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-en">vec</span><span class="pl-en">!</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>
    <span class="pl-en">println</span><span class="pl-en">!</span><span class="pl-kos">(</span><span class="pl-s">"Hello, world!"</span><span class="pl-kos">)</span><span class="pl-kos">;</span>
<span class="pl-kos">}</span></pre></div>
<p dir="auto">produces</p>
<div class="highlight highlight-source-shell notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="~/code/rust/panic/ § RUST_BACKTRACE=1 rustc src/main.rs                                                                                                                      (master*) [18:07:43]
&lt;std macros&gt;:3:1: 3:76 error: internal compiler error: cat_expr Errd
&lt;std macros&gt;:3 &lt; [ _ ] &gt; :: into_vec ( $ crate:: boxed:: Box:: new ( [ $ ( $ x ) , * ] ) ) )
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
&lt;std macros&gt;:1:1: 4:58 note: in expansion of vec!
src/main.rs:2:5: 2:14 note: expansion site
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&lt;Any&gt;', /build/rust/src/rustc-1.0.0/src/libsyntax/diagnostic.rs:149

stack backtrace:
   1:     0x7ff56b5d5189 - sys::backtrace::write::h85e36588f6ec519ed4r
   2:     0x7ff56b5dce96 - panicking::on_panic::h6e154bbd20295560jrw
   3:     0x7ff56b5a01a2 - rt::unwind::begin_unwind_inner::h58d8677c31c147e6t6v
   4:     0x7ff568b94a0d - rt::unwind::begin_unwind::h17109019831519213513
   5:     0x7ff568b949a2 - diagnostic::SpanHandler::span_bug::he871130351e8da9fEqB
   6:     0x7ff56942f163 - session::Session::span_bug::hf5507d592e7c6099PDq
   7:     0x7ff56a3d1a5d - check::regionck::visit_expr::h55b582b9adf67231Yhd
   8:     0x7ff56a3ce9d0 - check::regionck::Rcx&lt;'a, 'tcx&gt;::visit_fn_body::h894f2218ba6ba28epUc
   9:     0x7ff56a448546 - check::check_bare_fn::h16e5c54944c58ce3twn
  10:     0x7ff56a4463a2 - check::CheckItemBodiesVisitor&lt;'a, 'tcx&gt;.Visitor&lt;'tcx&gt;::visit_item::h960d90c3a6588469wtn
  11:     0x7ff56a50a34a - check_crate::closure.38028
  12:     0x7ff56a5056e0 - check_crate::h16da0c29bfd97789XcC
  13:     0x7ff56bb0fa08 - driver::phase_3_run_analysis_passes::h7268293564f4d974nGa
  14:     0x7ff56baf0b05 - driver::compile_input::hf89ed7761a9a5930Qba
  15:     0x7ff56bbb1fd1 - run_compiler::h61cd16b138828888z4b
  16:     0x7ff56bbafc22 - boxed::F.FnBox&lt;A&gt;::call_box::h3676213088059194772
  17:     0x7ff56bbaf159 - rt::unwind::try::try_fn::h2238843044414567073
  18:     0x7ff56b646b28 - rust_try_inner
  19:     0x7ff56b646b15 - rust_try
  20:     0x7ff56bbaf408 - boxed::F.FnBox&lt;A&gt;::call_box::h6492341214887270608
  21:     0x7ff56b5dbd81 - sys::thread::create::thread_start::ha66925ca4f47d19baqv
  22:     0x7ff566067353 - start_thread
  23:     0x7ff56b235bfc - __clone
  24:                0x0 - &lt;unknown&gt;"><pre class="notranslate"><span class="pl-k">~</span>/code/rust/panic/ § RUST_BACKTRACE=1 rustc src/main.rs                                                                                                                      (master<span class="pl-k">*</span>) [18:07:43]
<span class="pl-k">&lt;</span>std macros<span class="pl-k">&gt;</span>:3:1: 3:76 error: internal compiler error: cat_expr Errd
<span class="pl-k">&lt;</span>std macros<span class="pl-k">&gt;</span>:3 <span class="pl-k">&lt;</span> [ _ ] <span class="pl-k">&gt;</span> :: into_vec ( $ crate:: boxed:: Box:: new ( [ $ ( $ x ) , <span class="pl-k">*</span> ] ) ) )
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<span class="pl-k">&lt;</span>std macros<span class="pl-k">&gt;</span>:1:1: 4:58 note: <span class="pl-k">in</span> expansion of vec<span class="pl-k">!</span>
src/main.rs:2:5: 2:14 note: expansion site
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 <span class="pl-s"><span class="pl-pds">`</span>RUST_BACKTRACE=1<span class="pl-pds">`</span></span> <span class="pl-k">for</span> a backtrace
thread <span class="pl-s"><span class="pl-pds">'</span>rustc<span class="pl-pds">'</span></span> panicked at <span class="pl-s"><span class="pl-pds">'</span>Box&lt;Any&gt;<span class="pl-pds">'</span></span>, /build/rust/src/rustc-1.0.0/src/libsyntax/diagnostic.rs:149

stack backtrace:
   1:     0x7ff56b5d5189 - sys::backtrace::write::h85e36588f6ec519ed4r
   2:     0x7ff56b5dce96 - panicking::on_panic::h6e154bbd20295560jrw
   3:     0x7ff56b5a01a2 - rt::unwind::begin_unwind_inner::h58d8677c31c147e6t6v
   4:     0x7ff568b94a0d - rt::unwind::begin_unwind::h17109019831519213513
   5:     0x7ff568b949a2 - diagnostic::SpanHandler::span_bug::he871130351e8da9fEqB
   6:     0x7ff56942f163 - session::Session::span_bug::hf5507d592e7c6099PDq
   7:     0x7ff56a3d1a5d - check::regionck::visit_expr::h55b582b9adf67231Yhd
   8:     0x7ff56a3ce9d0 - check::regionck::Rcx<span class="pl-k">&lt;</span><span class="pl-s"><span class="pl-pds">'</span>a, <span class="pl-pds">'</span></span>tcx<span class="pl-k">&gt;</span>::visit_fn_body::h894f2218ba6ba28epUc
   9:     0x7ff56a448546 - check::check_bare_fn::h16e5c54944c58ce3twn
  10:     0x7ff56a4463a2 - check::CheckItemBodiesVisitor<span class="pl-k">&lt;</span><span class="pl-s"><span class="pl-pds">'</span>a, <span class="pl-pds">'</span></span>tcx<span class="pl-k">&gt;</span>.Visitor<span class="pl-k">&lt;</span><span class="pl-s"><span class="pl-pds">'</span>tcx&gt;::visit_item::h960d90c3a6588469wtn</span>
<span class="pl-s">  11:     0x7ff56a50a34a - check_crate::closure.38028</span>
<span class="pl-s">  12:     0x7ff56a5056e0 - check_crate::h16da0c29bfd97789XcC</span>
<span class="pl-s">  13:     0x7ff56bb0fa08 - driver::phase_3_run_analysis_passes::h7268293564f4d974nGa</span>
<span class="pl-s">  14:     0x7ff56baf0b05 - driver::compile_input::hf89ed7761a9a5930Qba</span>
<span class="pl-s">  15:     0x7ff56bbb1fd1 - run_compiler::h61cd16b138828888z4b</span>
<span class="pl-s">  16:     0x7ff56bbafc22 - boxed::F.FnBox&lt;A&gt;::call_box::h3676213088059194772</span>
<span class="pl-s">  17:     0x7ff56bbaf159 - rt::unwind::try::try_fn::h2238843044414567073</span>
<span class="pl-s">  18:     0x7ff56b646b28 - rust_try_inner</span>
<span class="pl-s">  19:     0x7ff56b646b15 - rust_try</span>
<span class="pl-s">  20:     0x7ff56bbaf408 - boxed::F.FnBox&lt;A&gt;::call_box::h6492341214887270608</span>
<span class="pl-s">  21:     0x7ff56b5dbd81 - sys::thread::create::thread_start::ha66925ca4f47d19baqv</span>
<span class="pl-s">  22:     0x7ff566067353 - start_thread</span>
<span class="pl-s">  23:     0x7ff56b235bfc - __clone</span>
<span class="pl-s">  24:                0x0 - &lt;unknown&gt;</span></pre></div>
<p dir="auto">Test case:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="fn main() { []; }"><pre class="notranslate"><code class="notranslate">fn main() { []; }
</code></pre></div>
<p dir="auto">Output:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="$ RUST_BACKTRACE=1 rustc test.rs 
test.rs:1:13: 1:15 error: internal compiler error: cat_expr Errd
test.rs:1 fn main() { []; }
                      ^~
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&lt;Any&gt;', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:129

stack backtrace:
   1:         0xcc029720 - sys::backtrace::write::h66f3f2784d0f6c5ddgA
   2:         0xcc051b80 - panicking::on_panic::h6fdde9e4e9166fe6jaJ
   3:         0xcbf91c30 - rt::unwind::begin_unwind_inner::hba10c536ef2aae75MQI
   4:         0xc92a10c0 - rt::unwind::begin_unwind::h11287547919384241778
   5:         0xc92a1050 - diagnostic::SpanHandler::span_bug::h551f703868554ecfUBD
   6:         0xc9e32fe0 - session::Session::span_bug::h10f6b5fdbea6485fbjp
   7:         0xcb6c5920 - check::regionck::visit_expr::hc78138689559ecf8Yrd
   8:         0xcb6c35c0 - check::regionck::Rcx&lt;'a, 'tcx&gt;::visit_fn_body::h75e2fac33dc50b43a4c
   9:         0xcb75ee50 - check::check_bare_fn::hf42e5aabaa5cb880Oan
  10:         0xcb756f40 - check::check_item::hdbe569c101f96905stn
  11:         0xcb822f10 - check_crate::closure.36015
  12:         0xcb81d9c0 - check_crate::h9d44bf3fde687089EXB
  13:         0xcc6a38c0 - driver::phase_3_run_analysis_passes::h36c633d41f11ca74wFa
  14:         0xcc689ec0 - driver::compile_input::h0de317319ab5c701Hba
  15:         0xcc754e20 - run_compiler::hffa0c0711e361de8E5b
  16:         0xcc753720 - thunk::F.Invoke&lt;A, R&gt;::invoke::h12673221910893163557
  17:         0xcc752610 - rt::unwind::try::try_fn::h15130568597725528481
  18:         0xcc0bd740 - rust_try_inner
  19:         0xcc0bd730 - rust_try
  20:         0xcc752910 - thunk::F.Invoke&lt;A, R&gt;::invoke::h3924406537784056782
  21:         0xcc03d990 - sys::thread::thread_start::h3734be2229bd3edegEE
  22:         0xc5f650c0 - start_thread
  23:         0xcbc0a449 - __clone
  24:                0x0 - &lt;unknown&gt;"><pre class="notranslate"><code class="notranslate">$ RUST_BACKTRACE=1 rustc test.rs 
test.rs:1:13: 1:15 error: internal compiler error: cat_expr Errd
test.rs:1 fn main() { []; }
                      ^~
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&lt;Any&gt;', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:129

stack backtrace:
   1:         0xcc029720 - sys::backtrace::write::h66f3f2784d0f6c5ddgA
   2:         0xcc051b80 - panicking::on_panic::h6fdde9e4e9166fe6jaJ
   3:         0xcbf91c30 - rt::unwind::begin_unwind_inner::hba10c536ef2aae75MQI
   4:         0xc92a10c0 - rt::unwind::begin_unwind::h11287547919384241778
   5:         0xc92a1050 - diagnostic::SpanHandler::span_bug::h551f703868554ecfUBD
   6:         0xc9e32fe0 - session::Session::span_bug::h10f6b5fdbea6485fbjp
   7:         0xcb6c5920 - check::regionck::visit_expr::hc78138689559ecf8Yrd
   8:         0xcb6c35c0 - check::regionck::Rcx&lt;'a, 'tcx&gt;::visit_fn_body::h75e2fac33dc50b43a4c
   9:         0xcb75ee50 - check::check_bare_fn::hf42e5aabaa5cb880Oan
  10:         0xcb756f40 - check::check_item::hdbe569c101f96905stn
  11:         0xcb822f10 - check_crate::closure.36015
  12:         0xcb81d9c0 - check_crate::h9d44bf3fde687089EXB
  13:         0xcc6a38c0 - driver::phase_3_run_analysis_passes::h36c633d41f11ca74wFa
  14:         0xcc689ec0 - driver::compile_input::h0de317319ab5c701Hba
  15:         0xcc754e20 - run_compiler::hffa0c0711e361de8E5b
  16:         0xcc753720 - thunk::F.Invoke&lt;A, R&gt;::invoke::h12673221910893163557
  17:         0xcc752610 - rt::unwind::try::try_fn::h15130568597725528481
  18:         0xcc0bd740 - rust_try_inner
  19:         0xcc0bd730 - rust_try
  20:         0xcc752910 - thunk::F.Invoke&lt;A, R&gt;::invoke::h3924406537784056782
  21:         0xcc03d990 - sys::thread::thread_start::h3734be2229bd3edegEE
  22:         0xc5f650c0 - start_thread
  23:         0xcbc0a449 - __clone
  24:                0x0 - &lt;unknown&gt;
</code></pre></div>
<p dir="auto">Compiler version:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="rustc 1.0.0-nightly (b47aebe3f 2015-02-26) (built 2015-02-27)
binary: rustc
commit-hash: b47aebe3fc2da06c760fd8ea19f84cbc41d34831
commit-date: 2015-02-26
build-date: 2015-02-27
host: x86_64-unknown-linux-gnu
release: 1.0.0-nightly"><pre class="notranslate"><code class="notranslate">rustc 1.0.0-nightly (b47aebe3f 2015-02-26) (built 2015-02-27)
binary: rustc
commit-hash: b47aebe3fc2da06c760fd8ea19f84cbc41d34831
commit-date: 2015-02-26
build-date: 2015-02-27
host: x86_64-unknown-linux-gnu
release: 1.0.0-nightly
</code></pre></div>
<p dir="auto">I modified the test case in <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="59341575" data-permission-text="Title is private" data-url="https://github.com/rust-lang/rust/issues/22894" data-hovercard-type="issue" data-hovercard-url="/rust-lang/rust/issues/22894/hovercard" href="https://github.com/rust-lang/rust/issues/22894">#22894</a> by moving the <code class="notranslate">&amp;*""</code> into <code class="notranslate">fn main()</code>, and I saw the same ICE.  I then changed the <code class="notranslate">""</code> to the similar <code class="notranslate">&amp;[]</code>, and I saw an ICE with a different error message and a different stack trace (e.g. phase 3 instead of phase 4).  The <code class="notranslate">&amp;</code> and <code class="notranslate">*</code> are unnecessary.</p>
<p dir="auto">I also see the <code class="notranslate">cat_expr Errd</code> message in <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="56894364" data-permission-text="Title is private" data-url="https://github.com/rust-lang/rust/issues/22037" data-hovercard-type="issue" data-hovercard-url="/rust-lang/rust/issues/22037/hovercard" href="https://github.com/rust-lang/rust/issues/22037">#22037</a>, but there are differences -- this issue happens in phase 3 rather than 4, and there is no "fictitious type" message.</p>