Panic after unresolved import: at 'attempted .def_id() on invalid def

[wolfgang42]

rustc --version --verbose:

rustc 1.8.0-nightly (fae516277 2016-02-13)
binary: rustc
commit-hash: fae516277b6da46b6c1cf568765c90fad2f9ae4b
commit-date: 2016-02-13
host: i686-unknown-linux-gnu
release: 1.8.0-nightly

Rust panicked on me while I was trying to set up a module. Here's a minimal testcase:

lib.rs:

mod m;
pub extern fn rust_main() {
    m::A::new();
}

m/mod.rs:

pub use A;

Backtrace:

m/mod.rs:1:9: 1:10 error: unresolved import `A`. There is no `A` in `???`. Did you mean to use `m`? [E0432]
m/mod.rs:1 pub use A;
                   ^
m/mod.rs:1:9: 1:10 help: run `rustc --explain E0432` to see a detailed explanation
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 'attempted .def_id() on invalid def: Err', ../src/librustc/middle/def.rs:142
stack backtrace:
   1: 0xb730834c - sys::backtrace::tracing::imp::write::h387a32948d611c79yru
   2: 0xb7311a31 - panicking::default_handler::_$u7b$$u7b$closure$u7d$$u7d$::closure.43392
   3: 0xb73114f8 - panicking::default_handler::hbf5aa91fdd0e1426mZy
   4: 0xb72d6339 - sys_common::unwind::begin_unwind_inner::hea259e071eb3dc55ngt
   5: 0xb72d6dd7 - sys_common::unwind::begin_unwind_fmt::had5362fd9bafeb0ctft
   6: 0xb60084b4 - middle::def::Def::def_id::hef18388ebff5ec86tys
   7: 0xb6caed36 - Resolver<'a, 'tcx>::resolve_path::h1ce47674c3a213038Sf
   8: 0xb6cb346a - Resolver<'a, 'tcx>::resolve_possibly_assoc_item::ha95ba1347bcc1bbbMQf
   9: 0xb6c8c28e - Resolver<'a, 'tcx>::resolve_expr::hb74f3c390e893b10cmg
  10: 0xb6cb9812 - intravisit::walk_expr::h1636770688153136850
  11: 0xb6c8e92d - Resolver<'a, 'tcx>::resolve_expr::hb74f3c390e893b10cmg
  12: 0xb6c8b998 - Resolver<'a, 'tcx>::resolve_block::h1690ef974f337496qof
  13: 0xb6c9468b - Resolver<'a, 'tcx>::resolve_function::h467d20f519802367S3e
  14: 0xb6ca2129 - intravisit::walk_item::h6828430058389820728
  15: 0xb6c89afc - Resolver<'a, 'tcx>::resolve_item::h6a78afdf3910c505yQe
  16: 0xb6cba644 - resolve_crate::h5df60da85863a96eKUg
  17: 0xb762084e - driver::phase_3_run_analysis_passes::h17332131489947047735
  18: 0xb75f560c - driver::compile_input::h9355f12a614fab1eBca
  19: 0xb75e575a - run_compiler::h3b7dbf7e780f38ff8Gc
  20: 0xb75e29b9 - sys_common::unwind::try::try_fn::h12326713950973088752
  21: 0xb7305d07 - __rust_try
  22: 0xb72fd876 - sys_common::unwind::inner_try::hb7a6267c6246d1cepdt
  23: 0xb75e32ef - boxed::F.FnBox<A>::call_box::h13838458491994583776
  24: 0xb730febb - sys::thread::Thread::new::thread_start::hbf982ddd460a42b7GWx
  25: 0xb2666f6f - start_thread
  26: 0xb718abed - clone
  27:        0x0 - <unknown>

[alexcrichton]

cc @jseyfried (looks like a nightly-only bug)

[jseyfried]

This is a duplicate of #31714, it was also caused by #31338.

[alexcrichton]

Aha, thanks @jseyfried!