ICE in coreutils: ERROR:rbml::reader: failed to find block with tag 56

[steveklabnik]

When trying to update uutils/coreutils to HEAD, I got this ICE:

ERROR:rbml::reader: failed to find block with tag 56
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 'explicit panic', ../src/librbml/lib.rs:395
stack backtrace:
   1:     0x7f60e8d337ae - sys::backtrace::tracing::imp::write::hb34e7b18704c1262Nlt
   2:     0x7f60e8d39fc5 - panicking::log_panic::closure.39173
   3:     0x7f60e8d39a2d - panicking::log_panic::h3e03128aaf32c48aZlx
   4:     0x7f60e8cfde33 - sys_common::unwind::begin_unwind_inner::h0bb9257f91805234eds
   5:     0x7f60e0ff285f - sys_common::unwind::begin_unwind::h8390130464056353774
   6:     0x7f60e0ff1986 - reader::get_doc::ha149a8570b2a7aacUxa
   7:     0x7f60e6c4c267 - iter::Map<I, F>.Iterator::next::h10861963622162946434
   8:     0x7f60e6c4bb8a - metadata::decoder::get_crate_deps::h9c9520eca05039edFio
   9:     0x7f60e6c585fd - metadata::creader::CrateReader<'a>::register_crate::h2a16aca49f291f70xep
  10:     0x7f60e6c5b55b - metadata::creader::CrateReader<'a>::resolve_crate::he5c783f43bf9c4f3sip
  11:     0x7f60e6c54e9c - metadata::creader::LocalCrateReader<'a, 'b>.visit..Visitor<'v>::visit_item::h05e7119c4b9ab1c5fQo
  12:     0x7f60e6c631df - metadata::creader::LocalCrateReader<'a, 'b>::read_crates::h0ee70b91136113a5kKp
  13:     0x7f60e9230af6 - driver::phase_3_run_analysis_passes::h16445406629327651071
  14:     0x7f60e92154cf - driver::compile_input::h67ced99e47f688630ba
  15:     0x7f60e937c61b - run_compiler::h920f4fedaef0ff122qc
  16:     0x7f60e9379e96 - boxed::F.FnBox<A>::call_box::h9381656930713324193
  17:     0x7f60e93797a4 - sys_common::unwind::try::try_fn::h630556235912263734
  18:     0x7f60e8d313e8 - __rust_try
  19:     0x7f60e8d2591b - sys_common::unwind::try::inner_try::heed00aff77e8028aM9r
  20:     0x7f60e937993e - boxed::F.FnBox<A>::call_box::h7166621089447816916
  21:     0x7f60e8d38a83 - sys::thread::Thread::new::thread_start::hf717c900e74acb2fbEw
  22:     0x7f60e22a70a3 - start_thread
  23:     0x7f60e89b304c - clone
  24:                0x0 - <unknown>

Version:

$ rustc --version
rustc 1.5.0-nightly (7bf4c885f 2015-09-26)

code: uutils/coreutils#690

[steveklabnik]

apparently, this happens as a side effect of the build process. i had built with stable, then tried to build with nightly, giving incorrect metadata