<p dir="auto">It appears that when a type alias to array type which uses an undefined constant for it's size is defined, the compiler crashes. I have only been able to reproduce this with the constants defined in uint modules.</p>
<p dir="auto">This code</p>
<div class="highlight highlight-source-rust notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="// This line prevents the crash
// use std::usize;

type Array = [usize; usize::MAX];

pub fn main() { }"><pre class="notranslate"><span class="pl-c">// This line prevents the crash</span>
<span class="pl-c">// use std::usize;</span>

<span class="pl-k">type</span> <span class="pl-smi">Array</span> = <span class="pl-kos">[</span><span class="pl-smi">usize</span><span class="pl-kos">;</span> usize<span class="pl-kos">::</span><span class="pl-v">MAX</span><span class="pl-kos">]</span><span class="pl-kos">;</span>

<span class="pl-k">pub</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-kos">}</span></pre></div>
<p dir="auto">Causes this ICE</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="$ rustc --version
rustc 1.4.0-nightly (14b7591ee 2015-08-25)

$ RUST_BACKTRACE=1 rustc test.rs
error: internal compiler error: unexpected panic
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
thread 'rustc' panicked at 'path not fully resolved: PathResolution { base_def: DefPrimTy(TyUint(usize)), last_private: LastMod(AllPublic), depth: 1 }', ../src/librustc/middle/def.rs:80

stack backtrace:
   1:        0x112c8e9b0 - sys::backtrace::tracing::imp::write::h3e935b9f3aaf3eeePbs
   2:        0x112c969db - panicking::on_panic::h957ddaa69f7f85c8gOw
   3:        0x112c5aaa2 - rt::unwind::begin_unwind_inner::hb89bb27d32753510tjw
   4:        0x112c5b82d - rt::unwind::begin_unwind_fmt::he8dabdca760d872dziw
   5:        0x10fb7f27e - middle::const_eval::eval_const_expr_partial::hf609e26a8506489cQVk
   6:        0x10f382980 - astconv::ast_ty_to_ty::h68164822b6891101Fhx
   7:        0x10f3f9b21 - collect::type_scheme_of_item::h682b0ea5c5e15cc9d8z
   8:        0x10f3f1915 - collect::convert_typed_item::hd9be457a3a816bfbYcA
   9:        0x10f3de6a5 - collect::convert_item::h608bb1b0eec4bc39d7y
  10:        0x10f3d96a6 - collect::collect_item_types::h044e5c22dac41959Jiy
  11:        0x10f425cad - check_crate::h6947ac03da7c9939BAE
  12:        0x10f0237b1 - driver::phase_3_run_analysis_passes::closure.20559
  13:        0x10f00379a - middle::ty::ctxt&lt;'tcx&gt;::create_and_enter::h16983514113163001088
  14:        0x10effee13 - driver::phase_3_run_analysis_passes::h14634090375742016845
  15:        0x10efe3424 - driver::compile_input::h6df79a1a00f2ec91Tba
  16:        0x10f147e01 - run_compiler::hf8bd4801a975e1fd0bc
  17:        0x10f1456e9 - boxed::F.FnBox&lt;A&gt;::call_box::h17883815892091822200
  18:        0x10f1450e2 - rt::unwind::try::try_fn::h1123102451065047215
  19:        0x112c96598 - __rust_try
  20:        0x112c82f60 - rt::unwind::try::inner_try::he6f08bfba5a665ddmfw
  21:        0x10f145292 - boxed::F.FnBox&lt;A&gt;::call_box::h10813678079818206125
  22:        0x112c9590d - sys::thread::Thread::new::thread_start::h868305d2c1b7d5304Dv
  23:     0x7fff95650267 - _pthread_body
  24:     0x7fff956501e4 - _pthread_start"><pre class="notranslate"><code class="notranslate">$ rustc --version
rustc 1.4.0-nightly (14b7591ee 2015-08-25)

$ RUST_BACKTRACE=1 rustc test.rs
error: internal compiler error: unexpected panic
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
thread 'rustc' panicked at 'path not fully resolved: PathResolution { base_def: DefPrimTy(TyUint(usize)), last_private: LastMod(AllPublic), depth: 1 }', ../src/librustc/middle/def.rs:80

stack backtrace:
   1:        0x112c8e9b0 - sys::backtrace::tracing::imp::write::h3e935b9f3aaf3eeePbs
   2:        0x112c969db - panicking::on_panic::h957ddaa69f7f85c8gOw
   3:        0x112c5aaa2 - rt::unwind::begin_unwind_inner::hb89bb27d32753510tjw
   4:        0x112c5b82d - rt::unwind::begin_unwind_fmt::he8dabdca760d872dziw
   5:        0x10fb7f27e - middle::const_eval::eval_const_expr_partial::hf609e26a8506489cQVk
   6:        0x10f382980 - astconv::ast_ty_to_ty::h68164822b6891101Fhx
   7:        0x10f3f9b21 - collect::type_scheme_of_item::h682b0ea5c5e15cc9d8z
   8:        0x10f3f1915 - collect::convert_typed_item::hd9be457a3a816bfbYcA
   9:        0x10f3de6a5 - collect::convert_item::h608bb1b0eec4bc39d7y
  10:        0x10f3d96a6 - collect::collect_item_types::h044e5c22dac41959Jiy
  11:        0x10f425cad - check_crate::h6947ac03da7c9939BAE
  12:        0x10f0237b1 - driver::phase_3_run_analysis_passes::closure.20559
  13:        0x10f00379a - middle::ty::ctxt&lt;'tcx&gt;::create_and_enter::h16983514113163001088
  14:        0x10effee13 - driver::phase_3_run_analysis_passes::h14634090375742016845
  15:        0x10efe3424 - driver::compile_input::h6df79a1a00f2ec91Tba
  16:        0x10f147e01 - run_compiler::hf8bd4801a975e1fd0bc
  17:        0x10f1456e9 - boxed::F.FnBox&lt;A&gt;::call_box::h17883815892091822200
  18:        0x10f1450e2 - rt::unwind::try::try_fn::h1123102451065047215
  19:        0x112c96598 - __rust_try
  20:        0x112c82f60 - rt::unwind::try::inner_try::he6f08bfba5a665ddmfw
  21:        0x10f145292 - boxed::F.FnBox&lt;A&gt;::call_box::h10813678079818206125
  22:        0x112c9590d - sys::thread::Thread::new::thread_start::h868305d2c1b7d5304Dv
  23:     0x7fff95650267 - _pthread_body
  24:     0x7fff956501e4 - _pthread_start
</code></pre></div>
<p dir="auto">Implementing my own fd_set because, per <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="93116784" data-permission-text="Title is private" data-url="https://github.com/rust-lang/rust/issues/26794" data-hovercard-type="issue" data-hovercard-url="/rust-lang/rust/issues/26794/hovercard" href="https://github.com/rust-lang/rust/issues/26794">#26794</a>, I can't find one exported elsewhere.  But trying to be clever about the size of the required array causes a panic:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="extern crate libc;

pub struct fd_set {
    pub __fds_bits: [libc::c_long ; (1024 / usize::BITS)],
}

fn main () {
}"><pre class="notranslate"><code class="notranslate">extern crate libc;

pub struct fd_set {
    pub __fds_bits: [libc::c_long ; (1024 / usize::BITS)],
}

fn main () {
}
</code></pre></div>
<p dir="auto">Causes the following output:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="error: internal compiler error: unexpected panic
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
thread 'rustc' panicked at 'path not fully resolved: PathResolution { base_def: DefPrimTy(TyUint(usize)), last_private: LastMod(AllPublic), depth: 1 }', ../src/librustc/middle/def.rs:81

stack backtrace:
   1:     0x7fc464f645ee - sys::backtrace::write::h04a6ced565b26815Lqs
   2:     0x7fc464f6c214 - panicking::on_panic::h521f84b604e22dfel8w
   3:     0x7fc464f2f04e - rt::unwind::begin_unwind_inner::hd3dee614a0e1c16cZNw
   4:     0x7fc464f2fd7c - rt::unwind::begin_unwind_fmt::ha4ce6704c81423045Mw
   5:     0x7fc462f5c059 - middle::const_eval::eval_const_expr_with_substs::h5244545712744191145
   6:     0x7fc462f5a532 - middle::const_eval::eval_const_expr_with_substs::h5244545712744191145
   7:     0x7fc462f5a8e3 - middle::const_eval::eval_const_expr_with_substs::h5244545712744191145
   8:     0x7fc462f0d04b - middle::const_eval::eval_const_expr_partial::h2b23a01d787e9d5efLk
   9:     0x7fc464740802 - astconv::ast_ty_to_ty::hb2c49d2cf31c029bYUv
  10:     0x7fc4647bcaa3 - iter::Map&lt;I, F&gt;.Iterator::next::h1378750426170396750
  11:     0x7fc4647b1ad8 - collect::convert_struct::h6351cd87dbfb23b7u5x
  12:     0x7fc4647a3080 - collect::convert_item::h502c0d9543ddcc68AKx
  13:     0x7fc46479e467 - collect::collect_item_types::hbd4ad720377bedf8RRw
  14:     0x7fc4647ec15b - check_crate::h594ee0148d251222uZC
  15:     0x7fc4654c4c69 - driver::phase_3_run_analysis_passes::closure.15783
  16:     0x7fc4654c3633 - middle::ty::ctxt&lt;'tcx&gt;::create_and_enter::h349256048753845929
  17:     0x7fc4654bea17 - driver::phase_3_run_analysis_passes::h15521018079403107052
  18:     0x7fc4654a1266 - driver::compile_input::hbf698b02349f7ce3Tba
  19:     0x7fc46557aed3 - run_compiler::hd724b5fef3441688y7b
  20:     0x7fc4655788ae - boxed::F.FnBox&lt;A&gt;::call_box::h6609070342514802751
  21:     0x7fc4655780f9 - rt::unwind::try::try_fn::h10774555836369096370
  22:     0x7fc464fe5d48 - rust_try_inner
  23:     0x7fc464fe5d35 - rust_try
  24:     0x7fc464f578a7 - rt::unwind::try::inner_try::hb0d7a3eb324339ceSJw
  25:     0x7fc46557830b - boxed::F.FnBox&lt;A&gt;::call_box::h18179817771297192954
  26:     0x7fc464f6ae71 - sys::thread::Thread::new::thread_start::hf8c7448e27294ed0PTv
  27:     0x7fc45eb9c529 - start_thread
  28:     0x7fc464bc322c - __clone
  29:                0x0 - &lt;unknown&gt;"><pre class="notranslate"><code class="notranslate">error: internal compiler error: unexpected panic
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
thread 'rustc' panicked at 'path not fully resolved: PathResolution { base_def: DefPrimTy(TyUint(usize)), last_private: LastMod(AllPublic), depth: 1 }', ../src/librustc/middle/def.rs:81

stack backtrace:
   1:     0x7fc464f645ee - sys::backtrace::write::h04a6ced565b26815Lqs
   2:     0x7fc464f6c214 - panicking::on_panic::h521f84b604e22dfel8w
   3:     0x7fc464f2f04e - rt::unwind::begin_unwind_inner::hd3dee614a0e1c16cZNw
   4:     0x7fc464f2fd7c - rt::unwind::begin_unwind_fmt::ha4ce6704c81423045Mw
   5:     0x7fc462f5c059 - middle::const_eval::eval_const_expr_with_substs::h5244545712744191145
   6:     0x7fc462f5a532 - middle::const_eval::eval_const_expr_with_substs::h5244545712744191145
   7:     0x7fc462f5a8e3 - middle::const_eval::eval_const_expr_with_substs::h5244545712744191145
   8:     0x7fc462f0d04b - middle::const_eval::eval_const_expr_partial::h2b23a01d787e9d5efLk
   9:     0x7fc464740802 - astconv::ast_ty_to_ty::hb2c49d2cf31c029bYUv
  10:     0x7fc4647bcaa3 - iter::Map&lt;I, F&gt;.Iterator::next::h1378750426170396750
  11:     0x7fc4647b1ad8 - collect::convert_struct::h6351cd87dbfb23b7u5x
  12:     0x7fc4647a3080 - collect::convert_item::h502c0d9543ddcc68AKx
  13:     0x7fc46479e467 - collect::collect_item_types::hbd4ad720377bedf8RRw
  14:     0x7fc4647ec15b - check_crate::h594ee0148d251222uZC
  15:     0x7fc4654c4c69 - driver::phase_3_run_analysis_passes::closure.15783
  16:     0x7fc4654c3633 - middle::ty::ctxt&lt;'tcx&gt;::create_and_enter::h349256048753845929
  17:     0x7fc4654bea17 - driver::phase_3_run_analysis_passes::h15521018079403107052
  18:     0x7fc4654a1266 - driver::compile_input::hbf698b02349f7ce3Tba
  19:     0x7fc46557aed3 - run_compiler::hd724b5fef3441688y7b
  20:     0x7fc4655788ae - boxed::F.FnBox&lt;A&gt;::call_box::h6609070342514802751
  21:     0x7fc4655780f9 - rt::unwind::try::try_fn::h10774555836369096370
  22:     0x7fc464fe5d48 - rust_try_inner
  23:     0x7fc464fe5d35 - rust_try
  24:     0x7fc464f578a7 - rt::unwind::try::inner_try::hb0d7a3eb324339ceSJw
  25:     0x7fc46557830b - boxed::F.FnBox&lt;A&gt;::call_box::h18179817771297192954
  26:     0x7fc464f6ae71 - sys::thread::Thread::new::thread_start::hf8c7448e27294ed0PTv
  27:     0x7fc45eb9c529 - start_thread
  28:     0x7fc464bc322c - __clone
  29:                0x0 - &lt;unknown&gt;
</code></pre></div>