Panic with incremental compilation: None.unwrap() in rustc_incremental::persist::hash::HashContext::hash

[Rufflewind]

I ran into this with CARGO_INCREMENTAL=1 cargo run --release. Incremental compilation was working just fine for the past few hours, but suddenly it panicked after I refactored a bunch of code from src/bin/X.rs to src/lib.rs.

Unfortunately, I wasn't able to reproduce this panic after calling cargo clean.

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

note: rustc 1.22.0-nightly (14039a42a 2017-09-22) running on x86_64-unknown-linux-gnu

note: run with `RUST_BACKTRACE=1` for a backtrace

thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', /checkout/src/libcore/option.rs:335:20
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: std::sys::imp::backtrace::tracing::imp::unwind_backtrace
             at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at /checkout/src/libstd/sys_common/backtrace.rs:71
   2: std::panicking::default_hook::{{closure}}
             at /checkout/src/libstd/sys_common/backtrace.rs:60
             at /checkout/src/libstd/panicking.rs:381
   3: std::panicking::default_hook
             at /checkout/src/libstd/panicking.rs:391
   4: std::panicking::rust_panic_with_hook
             at /checkout/src/libstd/panicking.rs:577
   5: std::panicking::begin_panic
             at /checkout/src/libstd/panicking.rs:538
   6: std::panicking::begin_panic_fmt
             at /checkout/src/libstd/panicking.rs:522
   7: rust_begin_unwind
             at /checkout/src/libstd/panicking.rs:498
   8: core::panicking::panic_fmt
             at /checkout/src/libcore/panicking.rs:71
   9: core::panicking::panic
             at /checkout/src/libcore/panicking.rs:51
  10: rustc_incremental::persist::hash::HashContext::hash
  11: rustc_incremental::persist::load::decode_dep_graph
  12: rustc_incremental::persist::load::load_dep_graph
  13: rustc::ty::context::TyCtxt::create_and_enter
  14: rustc_driver::driver::compile_input
  15: rustc_driver::run_compiler

[michaelwoerister]

Thanks for the bug report!

As of #44772, which was only merged very recently, the HashContext type is completely gone, but it's possible that a variation of the bug still exists. Would you mind re-testing with the latest nightly?

[Rufflewind]

Okay, I'll update my nightly and let you know if I run into a crash again. Thanks!

I guess I may as well close this for now.