ICE: Unexpected def description when inspecting MIR

[dlrobertson]

Summary

When compiling the following:

pub enum TestMe {
    X(usize),
}

with the following rustc command:

rustc --crate-type=lib --out-dir=./build --emit=mir ./test.rs

the following ICE occurs:

error: internal compiler error: src/librustc_mir/util/pretty.rs:612: Unexpected def description Some(Variant(DefId(0/1:11 ~ test[8787]::TestMe[0]::Y[0])))

Versions

This appears to be a regression from stable to (beta|nightly). It occurs on nightly and beta, but I couldn't get the ICE to occur on stable (1.33).

Backtrace

Backtrace

error: internal compiler error: src/librustc_mir/util/pretty.rs:612: Unexpected def description Some(Variant(DefId(0/1:11 ~ test[8787]::TestMe[0]::Y[0])))

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:620:9
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:39
   1: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:71
   2: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:59
   3: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:197
   4: std::panicking::default_hook
             at src/libstd/panicking.rs:211
   5: core::ops::function::Fn::call
             at /home/drobertson/git/rust/src/libcore/ops/function.rs:69
   6: rustc::util::common::panic_hook
             at src/librustc/util/common.rs:39
   7: core::ops::function::Fn::call
             at /home/drobertson/git/rust/src/libcore/ops/function.rs:69
   8: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:478
   9: std::panicking::begin_panic
             at /home/drobertson/git/rust/src/libstd/panicking.rs:408
  10: rustc_errors::Handler::bug
             at src/librustc_errors/lib.rs:620
  11: rustc::util::bug::opt_span_bug_fmt::{{closure}}
             at src/librustc/util/bug.rs:36
  12: rustc::ty::context::tls::with_opt::{{closure}}
             at src/librustc/ty/context.rs:2120
  13: rustc::ty::context::tls::with_context_opt
             at src/librustc/ty/context.rs:2055
  14: rustc::ty::context::tls::with_opt
             at src/librustc/ty/context.rs:2120
  15: rustc::util::bug::opt_span_bug_fmt
             at src/librustc/util/bug.rs:32
  16: rustc::util::bug::bug_fmt
             at src/librustc/util/bug.rs:12
  17: rustc_mir::util::pretty::write_mir_sig
             at src/librustc_mir/util/pretty.rs:612
  18: rustc_mir::util::pretty::write_mir_intro
             at src/librustc_mir/util/pretty.rs:553
  19: rustc_mir::util::pretty::write_mir_fn
             at src/librustc_mir/util/pretty.rs:293
  20: rustc_mir::util::pretty::write_mir_pretty
             at src/librustc_mir/util/pretty.rs:269
  21: rustc_mir::transform::dump_mir::emit_mir
             at src/librustc_mir/transform/dump_mir.rs:65
  22: rustc_driver::driver::compile_input::{{closure}}
             at src/librustc_driver/driver.rs:327
  23: rustc_driver::driver::phase_3_run_analysis_passes::{{closure}}
             at src/librustc_driver/driver.rs:1220
  24: rustc::ty::context::tls::enter_global::{{closure}}::{{closure}}
             at /home/drobertson/git/rust/src/librustc/ty/context.rs:2009
  25: rustc::ty::context::tls::enter_context::{{closure}}
             at /home/drobertson/git/rust/src/librustc/ty/context.rs:1975
  26: rustc::ty::context::tls::set_tlv
             at /home/drobertson/git/rust/src/librustc/ty/context.rs:1908
  27: rustc::ty::context::tls::enter_context
             at /home/drobertson/git/rust/src/librustc/ty/context.rs:1974
  28: rustc::ty::context::tls::enter_global::{{closure}}
             at /home/drobertson/git/rust/src/librustc/ty/context.rs:2008
  29: rustc::ty::context::tls::with_thread_locals::{{closure}}::{{closure}}
             at /home/drobertson/git/rust/src/librustc/ty/context.rs:1963
  30: <std::thread::local::LocalKey<T>>::try_with
             at /home/drobertson/git/rust/src/libstd/thread/local.rs:296
  31: <std::thread::local::LocalKey<T>>::with
             at /home/drobertson/git/rust/src/libstd/thread/local.rs:242
  32: rustc::ty::context::tls::with_thread_locals::{{closure}}
             at /home/drobertson/git/rust/src/librustc/ty/context.rs:1955
  33: <std::thread::local::LocalKey<T>>::try_with
             at /home/drobertson/git/rust/src/libstd/thread/local.rs:296
  34: <std::thread::local::LocalKey<T>>::with
             at /home/drobertson/git/rust/src/libstd/thread/local.rs:242
  35: rustc::ty::context::tls::with_thread_locals
             at /home/drobertson/git/rust/src/librustc/ty/context.rs:1947
  36: rustc::ty::context::tls::enter_global
             at /home/drobertson/git/rust/src/librustc/ty/context.rs:1986
  37: rustc::ty::context::TyCtxt::create_and_enter
             at /home/drobertson/git/rust/src/librustc/ty/context.rs:1300
  38: rustc_driver::driver::phase_3_run_analysis_passes
             at src/librustc_driver/driver.rs:1201
  39: rustc_driver::driver::compile_input
             at src/librustc_driver/driver.rs:275
  40: rustc_driver::run_compiler_with_pool
             at src/librustc_driver/lib.rs:268
  41: rustc_driver::run_compiler::{{closure}}
             at src/librustc_driver/lib.rs:185
  42: rustc_driver::driver::spawn_thread_pool::{{closure}}
             at src/librustc_driver/driver.rs:61
  43: <scoped_tls::ScopedKey<T>>::set
             at /home/drobertson/.cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-1.0.0/src/lib.rs:137
  44: rustc_driver::driver::spawn_thread_pool
             at src/librustc_driver/driver.rs:60
  45: rustc_driver::run_compiler
             at src/librustc_driver/lib.rs:184
  46: rustc_driver::main::{{closure}}
             at src/librustc_driver/lib.rs:1401
  47: rustc_driver::run::{{closure}}::{{closure}}
             at src/librustc_driver/lib.rs:136
  48: <scoped_tls::ScopedKey<T>>::set
             at /home/drobertson/.cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-1.0.0/src/lib.rs:137
  49: syntax::with_globals::{{closure}}
             at /home/drobertson/git/rust/src/libsyntax/lib.rs:100
  50: <scoped_tls::ScopedKey<T>>::set
             at /home/drobertson/.cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-1.0.0/src/lib.rs:137
  51: syntax::with_globals
             at /home/drobertson/git/rust/src/libsyntax/lib.rs:99
  52: rustc_driver::run::{{closure}}
             at src/librustc_driver/lib.rs:135
  53: rustc_driver::monitor::{{closure}}
             at src/librustc_driver/lib.rs:1317
query stack during panic:
end of query stack
error: aborting due to previous error


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: rustc 1.35.0-dev running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib

[dlrobertson]

Pretty sure this is happening when creating the constructor for the variants (e.g. TestMe::X(_1: usize)). is_function is not set for Def::Variant here, so we hit the ICE.