ICE in librustc_const_eval: bad ty_hint: TyBool, Int(1, Unsuffixed)

[scottmcm]

Playing with different ways to do static_assert!, I found an ICE. Reduced testcase:

fn main() {
    let _ : [(); ((1 < 2) == false) as usize] = [];
}

Happens in stable and nightly; here's the nightly backtrace from play:

rustc 1.16.0-nightly (eedaa94e3 2017-02-02)
error: internal compiler error: /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_const_eval/eval.rs:1105: bad ty_hint: TyBool, Int(1, Unsuffixed)

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<Any>', /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_errors/lib.rs:416
stack backtrace:
   1:     0x7f958019e45c - std::sys::imp::backtrace::tracing::imp::write::hf7294f5e24536b4a
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:42
   2:     0x7f95801ac90e - std::panicking::default_hook::{{closure}}::h9a07d0b00c43fbee
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/panicking.rs:351
   3:     0x7f95801ac4b3 - std::panicking::default_hook::hf25feff2d08bf39b
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/panicking.rs:361
   4:     0x7f95801acdab - std::panicking::rust_panic_with_hook::h4cb8c6fbb8386ccf
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/panicking.rs:555
   5:     0x7f95787bce37 - std::panicking::begin_panic::h133cfd00382ed92d
   6:     0x7f95787d251d - rustc_errors::Handler::bug::h0c95eedc3adddeaa
   7:     0x7f957d2cf10a - rustc::session::opt_span_bug_fmt::{{closure}}::hb77f1c2804eeb101
   8:     0x7f957d2cebc5 - rustc::session::opt_span_bug_fmt::h6020528146c503fb
   9:     0x7f957d2ce822 - rustc::session::bug_fmt::h80c5b006234b3146
  10:     0x7f957e0d3f36 - rustc_const_eval::eval::eval_const_expr_partial::h8d1162fa05e95e72
  11:     0x7f957e0cdad1 - rustc_const_eval::eval::eval_const_expr_partial::h8d1162fa05e95e72
  12:     0x7f957e0cdad1 - rustc_const_eval::eval::eval_const_expr_partial::h8d1162fa05e95e72
  13:     0x7f957e0cdd5e - rustc_const_eval::eval::eval_const_expr_partial::h8d1162fa05e95e72
  14:     0x7f957e0d64b3 - rustc_const_eval::eval::eval_length::h137b8f408aab940b
  15:     0x7f957ebdf58b - <rustc_typeck::astconv::AstConv<'gcx, 'tcx> + 'o>::ast_ty_to_ty::hf1f13e8dab321530
  16:     0x7f957eba1553 - <rustc_typeck::check::GatherLocalsVisitor<'a, 'gcx, 'tcx> as rustc::hir::intravisit::Visitor<'gcx>>::visit_local::h3eb6465c4518baea
  17:     0x7f957eb102d6 - rustc::hir::intravisit::walk_expr::h1fd71fafa6424277
  18:     0x7f957eba1cd5 - rustc_typeck::check::check_fn::hdcc283c26b22bc9e
  19:     0x7f957eba0f04 - rustc_typeck::check::check_bare_fn::hf15cf554a01d6e48
  20:     0x7f957eb9e0f5 - rustc_typeck::check::check_item_bodies::ha330650a58a36448
  21:     0x7f957ec0ba47 - rustc_typeck::check_crate::h06f4ceb61c7f6528
  22:     0x7f958054af27 - rustc_driver::driver::phase_3_run_analysis_passes::{{closure}}::h074ad5edbf4a7db7
  23:     0x7f958053d356 - rustc_driver::driver::phase_3_run_analysis_passes::h380fa931cb354859
  24:     0x7f958052b160 - rustc_driver::driver::compile_input::hab977ae496b3a6f1
  25:     0x7f9580575a94 - rustc_driver::run_compiler::h81290683db66a63c
  26:     0x7f9580481ebb - std::panicking::try::do_call::h00942d7a5d04424f
  27:     0x7f95801b5bea - __rust_maybe_catch_panic
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libpanic_unwind/lib.rs:98
  28:     0x7f95804aa122 - <F as alloc::boxed::FnBox<A>>::call_box::hd87f7ab2fccbd670
  29:     0x7f95801ab764 - std::sys::imp::thread::Thread::new::thread_start::hc16926852e47c008
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/liballoc/boxed.rs:624
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/sys_common/thread.rs:21
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/sys/unix/thread.rs:84
  30:     0x7f9577f676b9 - start_thread
  31:     0x7f957fe6182c - clone
  32:                0x0 - <unknown>

[larsluthman]

My fix attempt is at #39812 .