clippy rustc panic

[tdyas]

cargo version: cargo 1.48.0 (65cbdd2dc 2020-10-14)
rustc version: rustc 1.48.0 (7eac88abb 2020-11-16)

I encountered a rustc panic while running cargo clippy. I made a source code change and then the panic occurred. After reverting the source code change, the panic still occurs even though clippy ran just fine on the code before the change.

Panic message:

thread 'rustc' panicked at 'assertion failed: `(left == right)`
  left: `1`,
 right: `1002111927320821928687967599834759150`', compiler/rustc_middle/src/ty/query/on_disk_cache.rs:553:5
stack backtrace:
   0:        0x103478aa4 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hcfc48256a5ab8835
   1:        0x1034df590 - core::fmt::write::haf3903118f694c48
   2:        0x10346a0a6 - std::io::Write::write_fmt::h7385463ac87804ed
   3:        0x10347d46f - std::panicking::default_hook::{{closure}}::h91bd4c58cf71392b
   4:        0x10347d13d - std::panicking::default_hook::h7bd29c87df967048
   5:        0x102d1a790 - clippy_driver::report_clippy_ice::ha6f8893b9494152a
   6:        0x10347db9e - std::panicking::rust_panic_with_hook::hae2b05f08a320721
   7:        0x10347d6fb - std::panicking::begin_panic_handler::{{closure}}::h72d68d3a77e0b718
   8:        0x103478f18 - std::sys_common::backtrace::__rust_end_short_backtrace::h7c5e286792f94edb
   9:        0x10347d6ba - _rust_begin_unwind
  10:        0x103503e4b - std::panicking::begin_panic_fmt::h6826a3ebe3a95a51
  11:        0x10ec65c21 - rustc_middle::ty::query::on_disk_cache::OnDiskCache::new::hbdcff5bfe914d997
  12:        0x10df2ad24 - rustc_incremental::persist::load::load_query_result_cache::h9d7279d740050e3e
  13:        0x10ac4d178 - rustc_interface::passes::create_global_ctxt::h0a00e9a607f14bd6
  14:        0x10ac7e33d - rustc_interface::queries::Queries::global_ctxt::he0bb274ddf484806
  15:        0x10aa7d1ea - rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter::heacbf49337f5fb9d
  16:        0x10aa5a321 - rustc_span::with_source_map::h3927afb6bcf6a169
  17:        0x10aa787c9 - scoped_tls::ScopedKey<T>::set::h5608e7cc9397961b
  18:        0x10aa80644 - std::sys_common::backtrace::__rust_begin_short_backtrace::h9b82f31f81e95856
  19:        0x10aa135bc - core::ops::function::FnOnce::call_once{{vtable.shim}}::h5baa2aca5ae17340
  20:        0x10348bb7d - std::sys::unix::thread::Thread::new::thread_start::he3e6719579180a65
  21:     0x7fff6ae5a109 - __pthread_start

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-clippy/issues/new

note: Clippy version: clippy 0.0.212 (7eac88abb 2020-11-16)

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

I ran cargo clean and re-ran clippy again with the code change, and now it works fine.

I suspect some form of corruption of the on-disk cache given the panic originated in on_disk_cache.rs and was fixed by wiping the cache.

[giraffate]

Thaks for your report!

It might be a rustc bug, not Clippy. This is similar to rust-lang/rust#71733.

[giraffate]

Thanks for your comment on rust-lang/rust.

I'm closing this because it seems to be a rustc bug, not Clippy.