Compiler panic when implementing a trait for another trait with a lifetime in a lib

[pmsanford]

This code will cause a compiler panic

#![crate_type = "lib"]

trait Foo for Sized? { }

trait Bar { }

impl<'a> Foo for Bar + 'a { }

link to run: http://is.gd/MC2wAS

message:

error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: http://doc.rust-lang.org/complement-bugreport.html
note: run with `RUST_BACKTRACE=1` for a backtrace
task 'rustc' panicked at 'assertion failed: bounds.is_none()', /Users/rustbuild/src/rust-buildbot/slave/nightly-mac/build/src/librustc/metadata/encoder.rs:1231

This panic only occurs when building as a lib, whether by the #![crate_type = "lib"] attribute or with the --crate-type lib command line option. If you remove the crate_type attribute and add a fn main() {} it does not panic.

[tomjakubowski]

Backtrace I got with that example:

task 'rustc' panicked at 'assertion failed: bounds.is_none()', /build/rust-git/src/rust/src/librustc/metadata/encoder.rs:1231

stack backtrace:
   1:     0x7fdb42752c20 - rt::backtrace::imp::write::hcc244d480521f5e9Pdt
   2:     0x7fdb42755ca0 - <unknown>
   3:     0x7fdb42f13c80 - unwind::begin_unwind_inner::h5eadd82ce47d0284E9c
   4:     0x7fdb432c0680 - <unknown>
   5:     0x7fdb43a535d0 - <unknown>
   6:     0x7fdb43a58d70 - <unknown>
   7:     0x7fdb435066c0 - <unknown>
   8:     0x7fdb435066c0 - <unknown>
   9:     0x7fdb43a5ae20 - <unknown>
  10:     0x7fdb43a5f320 - <unknown>
  11:     0x7fdb43684470 - metadata::encoder::encode_metadata::h633a4478d051f03eSbw
  12:     0x7fdb43683c70 - middle::trans::base::write_metadata::h30a48bed88474a06zQi
  13:     0x7fdb43685950 - middle::trans::base::trans_crate::haaa13fd4751fa866GYi
  14:     0x7fdb43a9fe70 - driver::driver::phase_4_translate_to_llvm::h85e6560af237b5f1kkC
  15:     0x7fdb43a97470 - driver::driver::compile_input::h02996843b5f2a565eRB
  16:     0x7fdb43b1a800 - <unknown>
  17:     0x7fdb43b1a6f0 - <unknown>
  18:     0x7fdb432f3bc0 - <unknown>
  19:     0x7fdb432f39b0 - <unknown>
  20:     0x7fdb44344a30 - <unknown>
  21:     0x7fdb42f60e00 - <unknown>
  22:     0x7fdb42f60df0 - rust_try
  23:     0x7fdb42f11600 - unwind::try::h333ab25385d8e012mYc
  24:     0x7fdb42f11490 - task::Task::run::h2157d702c714dd0du4b
  25:     0x7fdb44344770 - <unknown>
  26:     0x7fdb42f12ca0 - <unknown>
  27:     0x7fdb3def3060 - start_thread
  28:     0x7fdb42be4489 - __clone
  29:                0x0 - <unknown>

rustc version is rustc 0.13.0-dev (7a86aa83e 2014-11-12 21:07:09 +0000)

[msiemens]

I got a more detailled backtrace:

stack backtrace:
   1:     0x7f5363c08220 - rt::backtrace::imp::write::h64ddbb80732cebe7mft
   2:     0x7f5363c0b2a0 - failure::on_fail::h94b40e248cb876efXAt
   3:     0x7f53643da330 - unwind::begin_unwind_inner::h95c06af1b5484b5aE9c
   4:     0x7f53647a7390 - unwind::begin_unwind::h2953665953488925265
   5:     0x7f536500c360 - metadata::encoder::encode_info_for_item::h2fdf288e1d9b50a1X2u
   6:     0x7f53650120b0 - metadata::encoder::my_visit_item::closure.140832
   7:     0x7f5364a29320 - ast_map::Map<'ast>::with_path_next::h5678203148237041916
   8:     0x7f5364a29320 - ast_map::Map<'ast>::with_path_next::h5678203148237041916
   9:     0x7f53650140b0 - visit::walk_mod::h4122475244020002523
  10:     0x7f53650187b0 - metadata::encoder::encode_metadata_inner::he495ee9af76720e0wbw
  11:     0x7f5364bd25e0 - metadata::encoder::encode_metadata::h4800ccb08c786519Zaw
  12:     0x7f5364bd1dc0 - middle::trans::base::write_metadata::ha68b38aa6474f49aRPi
  13:     0x7f5364bd3b40 - middle::trans::base::trans_crate::hfdcd15c7cca1daefYXi
  14:     0x7f536505eda0 - driver::driver::phase_4_translate_to_llvm::h6acbdd487716233dyjC
  15:     0x7f5365054410 - driver::driver::compile_input::h6b78440b664993f7sQB
  16:     0x7f53650db7c0 - driver::run_compiler::h1e6c21018535d044JGF
  17:     0x7f53650db6b0 - driver::run::closure.146249
  18:     0x7f53647dcd20 - task::TaskBuilder<S>::try_future::closure.104741
  19:     0x7f53647dcb10 - task::TaskBuilder<S>::spawn_internal::closure.104712
  20:     0x7f5365934b50 - task::NativeSpawner.Spawner::spawn::closure.2549
  21:     0x7f536442f1e0 - rust_try_inner
  22:     0x7f536442f1d0 - rust_try
  23:     0x7f53643d7cb0 - unwind::try::h164a60eea6d3f88cmYc
  24:     0x7f53643d7b40 - task::Task::run::had29636eca7af1a3u4b
  25:     0x7f5365934890 - task::NativeSpawner.Spawner::spawn::closure.2475
  26:     0x7f53643d9350 - thread::thread_start::h1833ce4dca7b1a7erpc
  27:     0x7f535f3fae20 - start_thread
  28:     0x7f53640a5b59 - clone
  29:                0x0 - <unknown>

with

$ rustc --version
rustc 0.13.0-nightly (5745e4195 2014-11-12 22:57:16 +0000)

[tamird]

This now compiles:

#![crate_type = "lib"]

trait Foo { }

trait Bar { }

impl<'a> Foo for Bar + 'a { }