internal compiler error: assertion failed: bpos.to_usize() >= mbc.pos.to_usize() + mbc.bytes

[fintelia]

I tried this code:

lib.rs:

#![feature(iterator_step_by)]
#![feature(ord_max_min)]
#![feature(test)]
#![feature(unboxed_closures)]
#![feature(try_from)]
#![feature(slice_patterns)]
#![feature(non_ascii_idents)]

pub mod precompute;

precompute.rs:

#[test]
fn it_works() {
    fn inner() -> f64 {
        let µ = 1.0;
        µ
    }
    let _µ = inner();
}

I expected to see this happen: compile properly and tests pass.

Instead, this happened: internal compiler error.

Possibly related to #46773, but I wasn't sure since the backtraces seemed rather different.

Meta

rustc --version --verbose:

rustc 1.26.0-nightly (063deba92 2018-02-23)
binary: rustc
commit-hash: 063deba92e44809125a433ca6e6c1ad0993313bf
commit-date: 2018-02-23
host: x86_64-unknown-linux-gnu
release: 1.26.0-nightly
LLVM version: 6.0

Backtrace:

   Compiling unicode v0.1.0 (file:///home/jonathan/tmp/unicode)
thread 'rustc' panicked at 'assertion failed: bpos.to_usize() >= mbc.pos.to_usize() + mbc.bytes', libsyntax/codemap.rs:764:17
stack backtrace:
   0:     0x7f065582e063 - std::sys::unix::backtrace::tracing::imp::unwind_backtrace::hd00aa766a56fe293
                               at libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1:     0x7f0655825554 - std::sys_common::backtrace::_print::h54da06fb16cb9ad6
                               at libstd/sys_common/backtrace.rs:71
   2:     0x7f065582ac9d - std::panicking::default_hook::{{closure}}::h67dd2c5bdfbcdba1
                               at libstd/sys_common/backtrace.rs:59
                               at libstd/panicking.rs:206
   3:     0x7f065582a999 - std::panicking::default_hook::h14daf183f7987b45
                               at libstd/panicking.rs:222
   4:     0x7f065582b0ff - std::panicking::rust_panic_with_hook::haf158391394f8248
                               at libstd/panicking.rs:400
   5:     0x7f06516247c5 - std::panicking::begin_panic::hc4b15280f4aac00e
   6:     0x7f06516ada1b - syntax::codemap::CodeMap::bytepos_to_file_charpos::h1904a2e0951f1ef0
   7:     0x7f06516aa4e4 - syntax::codemap::CodeMap::lookup_char_pos::hf465c34067aaa7fe
   8:     0x7f064aaf53f3 - rustc_trans::mir::FunctionCx::set_debug_loc::h1fab6c6c56da0887
   9:     0x7f064aafb4db - rustc_trans::mir::trans_mir::hd5460c3409d3184b
  10:     0x7f064aabd553 - rustc_trans::base::trans_instance::h7a0842c683f85f40
  11:     0x7f064aac8f4d - rustc_trans::base::compile_codegen_unit::h89925300458c236e
  12:     0x7f065241df64 - rustc::dep_graph::graph::DepGraph::with_task_impl::h8d57a8788dba82ff
  13:     0x7f06527f5b50 - rustc::ty::maps::<impl rustc::ty::maps::queries::compile_codegen_unit<'tcx>>::force::h9473f2f719c9e900
  14:     0x7f06527f6f2f - rustc::ty::maps::<impl rustc::ty::maps::queries::compile_codegen_unit<'tcx>>::try_get::hb1acd3d0f00d8e17
  15:     0x7f0652816a4c - rustc::ty::maps::TyCtxtAt::compile_codegen_unit::h0f13d4057b5fa559
  16:     0x7f065280f5b9 - rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::compile_codegen_unit::h57dae7b07151dfca
  17:     0x7f064aabf637 - rustc_trans::base::trans_crate::h510f789f4dd2fca5
  18:     0x7f064ab1b007 - <rustc_trans::LlvmTransCrate as rustc_trans_utils::trans_crate::TransCrate>::trans_crate::hc34c86a7991a2357
  19:     0x7f0655be16c2 - rustc_driver::driver::phase_4_translate_to_llvm::heb37816963659b45
  20:     0x7f0655bda6ce - rustc_driver::driver::compile_input::{{closure}}::hb05e220533907e90
  21:     0x7f0655b7176e - rustc::ty::context::TyCtxt::create_and_enter::h74bf9fb47bfc54a3
  22:     0x7f0655bd867b - rustc_driver::driver::compile_input::hac1d19a7e4d66b92
  23:     0x7f0655bf575a - rustc_driver::run_compiler::h5fd8f6d44462a7b6
  24:     0x7f0655b20a8a - std::sys_common::backtrace::__rust_begin_short_backtrace::h093a629e65f72505
  25:     0x7f0655843c4e - __rust_maybe_catch_panic
                               at libpanic_unwind/lib.rs:102
  26:     0x7f0655b59ca6 - <F as alloc::boxed::FnBox<A>>::call_box::h41c53d796e08f220
  27:     0x7f065583b00b - std::sys::unix::thread::Thread::new::thread_start::h72150edde1f62ab4
                               at /checkout/src/liballoc/boxed.rs:798
                               at libstd/sys_common/thread.rs:24
                               at libstd/sys/unix/thread.rs:90
  28:     0x7f065070f7fb - start_thread
  29:     0x7f06554f3b5e - clone
  30:                0x0 - <unknown>

[fintelia]

Slightly simpler example:

main.rs:

#![feature(non_ascii_idents)]

mod inner;
fn main() {
    inner::inner();
}

inner.rs:

pub fn foo() -> f64 {
    let µ = 1.0;
    µ
}