ICE with 1.0.0 when accidentally using integer literal in a float expression

[rsaarelm]

Replication:

#!/bin/bash

cat > ice.rs <<EOF
pub fn cubic_out(t: f32) -> f32 {
    let u = t - 1.0;
    u * u * u + 1.0
}

pub fn cubic_in_out(t: f32) -> f32 {
    if t < 0.5 {
        4.0 * t * t * t
    } else {
        let u = 2.0 * t - 2.0;
        0.5 * u * u * u + 1 // <- should have been 1.0
    }
}

fn main() {}
EOF

RUST_BACKTRACE=1 rustc ice.rs
rustc --version
uname -a

Output:

error: internal compiler error: Impl DefId { krate: 2, node: 22039 } was matchable against Obligation(predicate=Binder(TraitPredicate(core::ops::Add<_>)),depth=1) but now is not
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>', /home/rustbuild/src/rust-buildbot/slave/stable-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:209

stack backtrace:
   1:     0x7f2bee48b449 - sys::backtrace::write::hbc46dc0cfb3b9537d4r
   2:     0x7f2bee493156 - panicking::on_panic::h74d3c14d86c58ac8jrw
   3:     0x7f2bee456462 - rt::unwind::begin_unwind_inner::h382cea404b11eb00t6v
   4:     0x7f2beba433fd - rt::unwind::begin_unwind::h6365792021826883910
   5:     0x7f2beba43abb - diagnostic::Handler::bug::h8da0df7c5604a97agwB
   6:     0x7f2bec5da5c9 - middle::traits::select::SelectionContext<'cx, 'tcx>::rematch_impl::hb810aa50e0642064QXT
   7:     0x7f2bec5da058 - middle::infer::InferCtxt<'a, 'tcx>::commit_if_ok::h11340253380734990355
   8:     0x7f2bec5c4691 - middle::traits::select::SelectionContext<'cx, 'tcx>::confirm_candidate::h8d339edae207ea7dSfT
   9:     0x7f2bec5a39d4 - middle::traits::select::SelectionContext<'cx, 'tcx>::select::hb26a930282b51b57vhR
  10:     0x7f2bec5ae835 - middle::traits::project::project_type::hcc7bca026d7e1d2bCYP
  11:     0x7f2bec5ad418 - middle::traits::project::opt_normalize_projection_type::h4a097d94b366c5ceeRP
  12:     0x7f2bec5aa130 - middle::traits::project::project_and_unify_type::h9cf73365a74ef3d28zP
  13:     0x7f2bec5a853c - middle::infer::InferCtxt<'a, 'tcx>::commit_if_ok::h9241733706551492922
  14:     0x7f2bec5a0b5d - middle::traits::fulfill::FulfillmentContext<'tcx>::select::h2e0ac81f16f15072G9O
  15:     0x7f2bec5a058b - middle::traits::fulfill::FulfillmentContext<'tcx>::select_where_possible::h0b137ff14b482b66U8O
  16:     0x7f2bed272bf8 - check::vtable::select_fcx_obligations_where_possible::ha6ba35a732d29514r5b
  17:     0x7f2bed290c6a - check::FnCtxt<'a, 'tcx>::resolve_type_vars_if_possible::h5ccd1e4895d48de9Vwo
  18:     0x7f2bed2f21ee - check::op::check_binop::h4d254cc3af37a49dXMm
  19:     0x7f2bed32f8fd - check::check_expr_with_unifier::h16758040784423113870
  20:     0x7f2bed2ffedc - check::check_block_with_expected::h31a6d6204e48ff42nUr
  21:     0x7f2bed33ba1e - check::check_expr_with_unifier::h7613982835395653666
  22:     0x7f2bed315d39 - check::check_expr_with_unifier::check_then_else::h2bc634554fa150fbxkq
  23:     0x7f2bed32fbdd - check::check_expr_with_unifier::h16758040784423113870
  24:     0x7f2bed2ffedc - check::check_block_with_expected::h31a6d6204e48ff42nUr
  25:     0x7f2bed2e26c6 - check::check_fn::h1656833949835747UGn
  26:     0x7f2bed2fb594 - check::check_bare_fn::h1ca89f422d965ecetwn
  27:     0x7f2bed2f96f2 - check::CheckItemBodiesVisitor<'a, 'tcx>.Visitor<'tcx>::visit_item::h29ccc99d00d684a7wtn
  28:     0x7f2bed3bd69a - check_crate::closure.38028
  29:     0x7f2bed3b8a30 - check_crate::h22dcd95e17a2d96dXcC
  30:     0x7f2bee9cfcc8 - driver::phase_3_run_analysis_passes::h43926ceca86caa9fnGa
  31:     0x7f2bee9b0dc5 - driver::compile_input::hb78754f2f33c01efQba
  32:     0x7f2beea724d1 - run_compiler::h258d36d5501c1cdfz4b
  33:     0x7f2beea70122 - boxed::F.FnBox<A>::call_box::h7239693171334256553
  34:     0x7f2beea6f659 - rt::unwind::try::try_fn::h14329119008520845439
  35:     0x7f2bee505ac8 - rust_try_inner
  36:     0x7f2bee505ab5 - rust_try
  37:     0x7f2beea6f908 - boxed::F.FnBox<A>::call_box::h17332056298259451807
  38:     0x7f2bee492041 - sys::thread::create::thread_start::h490278b5c3c0b49faqv
  39:     0x7f2be8d36373 - start_thread
  40:     0x7f2bee0ec27c - clone
  41:                0x0 - <unknown>

rustc 1.0.0 (a59de37e9 2015-05-13) (built 2015-05-14)
Linux 3.19.3-3-ARCH #1 SMP PREEMPT Wed Apr 8 14:10:00 CEST 2015 x86_64 GNU/Linux

[arielb1]

This is a known bug. It is fixed in 1.2 (by #25344). Maybe we should backport that fix to 1.1?

[steveklabnik]

We're being very conservative with backports, ICE fixes don't really qualify.

Thank you for the report @rsaarelm !