ICE: 'internal error: entered unreachable code', compiler/rustc_resolve/src/imports.rs:965:70

Code

use clippy::a::b;

fn main() {}

Meta

Playground
Happens on stable and nightly.

rustc 1.50.0 (cb75ad5db 2021-02-10)
rustc 1.52.0-nightly (f5f33ec0e 2021-03-19)

Error output

Compiler crash

Backtrace

Compiling playground v0.0.1 (/playground)
thread 'rustc' panicked at 'internal error: entered unreachable code', compiler/rustc_resolve/src/imports.rs:958:70
stack backtrace:
   0: rust_begin_unwind
             at /rustc/cb75ad5db02783e8b0222fee363c5f63f7e2cf5b/library/std/src/panicking.rs:493:5
   1: core::panicking::panic_fmt
             at /rustc/cb75ad5db02783e8b0222fee363c5f63f7e2cf5b/library/core/src/panicking.rs:92:14
   2: core::panicking::panic
             at /rustc/cb75ad5db02783e8b0222fee363c5f63f7e2cf5b/library/core/src/panicking.rs:50:5
   3: rustc_resolve::imports::ImportResolver::finalize_import
   4: rustc_resolve::imports::ImportResolver::finalize_imports
   5: rustc_resolve::Resolver::resolve_crate
   6: rustc_interface::passes::configure_and_expand_inner
   7: rustc_interface::passes::configure_and_expand::{{closure}}
   8: rustc_data_structures::box_region::PinnedGenerator<I,A,R>::new
   9: rustc_interface::passes::configure_and_expand
  10: rustc_interface::queries::Queries::expansion
  11: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  12: rustc_span::with_source_map
  13: rustc_interface::interface::create_compiler_and_run
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.50.0 (cb75ad5db 2021-02-10) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2 --crate-type bin

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
end of query stack
error: could not compile `playground`

To learn more, run the command again with --verbose.

[apiraino]

This regression looks to be really old. Could not pinpoint a specific commit while bisecting

********************************************************************************
Regression in nightly-2018-11-20
********************************************************************************
found 6 bors merge commits in the specified range
  commit[0] 2018-11-18UTC: Auto merge of #56017 - alexcrichton:debug-test, r=alexcrichton
  commit[1] 2018-11-18UTC: Auto merge of #55672 - RalfJung:miri-extern-types, r=eddyb
  commit[2] 2018-11-19UTC: Auto merge of #56042 - petrochenkov:nuni, r=petrochenkov
  commit[3] 2018-11-19UTC: Auto merge of #56051 - pietroalbini:rollup, r=pietroalbini
  commit[4] 2018-11-19UTC: Auto merge of #56060 - nrc:save-path-fallback, r=zackmdavis
  commit[5] 2018-11-19UTC: Auto merge of #55971 - SergioBenitez:skip-non-semantic, r=alexcrichton
ERROR: no commits between 13c9439925797cd7a65c917d047c07a500d9bfe6 and 
5aff30734b0e1056b1003459fbb27af199f51822 within last 167 days

[jyn514]

@apiraino I don't think this is a regression, the --edition 2018 flag just didn't exist before 1.31 (the panic doesn't occur without --edition).

[camelid]

Assigning P-low and removing I-prioritize as discussed in the prioritization working group.

@rustbot label: +P-low -I-prioritize