Unexpected None, no reproduction

[ghost]

When this ICE happened, I tried to create a minimal reproduction right away; this was apparently a mistake, as after a few changes to my code, the crash vanished and I couldn't get it to come back. I'm reporting this anyway with the hope that someone might be able to work backwards from the point of the crash and figure out where the bad None is coming from.

Code

While I was trying to figure out which part of my code was triggering this issue by deleting various pieces and recompiling, it disappeared and refused to come back even after restoring my code back to where it was when the crash happened. I therefore have been unable to reproduce the issue with any specific code. I understand that this probably makes this issue very difficult to investigate.

Meta

rustc --version --verbose:

rustc 1.50.0-nightly (3d6705aa5 2020-12-07)
binary: rustc
commit-hash: 3d6705aa5abffe94c83bf09af8c3ba3c599845fc
commit-date: 2020-12-07
host: x86_64-unknown-linux-musl
release: 1.50.0-nightly

My build situation is very weird. The code being compiled is no_std, rustc is given -Z pre-link-args=-nostartfiles, and cargo is given -Z build-std=core,alloc --target x86_64-unknown-linux-gnu. There are probably other weird things around that I missed when I dug through my build setup and Cargo.tomls.

Error output

thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', compiler/rustc_middle/src/ty/query/mod.rs:235:5
note: run with `RUST_BACKTRACE=1` environment variable to display a 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-nightly (3d6705aa5 2020-12-07) running on x86_64-unknown-linux-musl

note: compiler flags: -Z pre-link-args=-nostartfiles -Z unstable-options -C panic=abort -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin

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

query stack during panic:
end of query stack
thread '<unnamed>' panicked at 'assertion failed: `(left == right)`
  left: `LLVMing`,
 right: `Codegenning`', /rustc/3d6705aa5abffe94c83bf09af8c3ba3c599845fc/compiler/rustc_codegen_ssa/src/back/write.rs:1425:21

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-nightly (3d6705aa5 2020-12-07) running on x86_64-unknown-linux-musl

note: compiler flags: -Z pre-link-args=-nostartfiles -Z unstable-options -C panic=abort -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin

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

query stack during panic:
end of query stack

I tried to create a minimal reproduction before I ran with RUST_BACKTRACE, so unfortunately I don't have a backtrace to report. Again, I know this makes this very hard to investigate.

[RustyYato]

I ran into exactly the same error in my crate contextual, on the ICE-2 branch linked below (I have all build artifacts, just in case this was a caching issue, like #79835, but if that's not the case I'll be removing the target dir)

https://github.com/RustyYato/contextual/tree/ICE-2

edit: (I've updated the mvp from the ICE branch to the ICE-2 branch)

I'll try and get that as minimal as I can get it

$ rustc --version --verbose
rustc 1.50.0-nightly (3d6705aa5 2020-12-07)
binary: rustc
commit-hash: 3d6705aa5abffe94c83bf09af8c3ba3c599845fc
commit-date: 2020-12-07
host: x86_64-pc-windows-msvc
release: 1.50.0-nightly

Backtrace

thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', compiler\rustc_middle\src\ty\query\mod.rs:235:5
stack backtrace:
   0:     0x7ffbcd57b865 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h106ca6f8fb6a294d
   1:     0x7ffbcd5a727b - core::fmt::write::h6390b994d95aebdb
   2:     0x7ffbcd56cefd - <std::io::IoSlice as core::fmt::Debug>::fmt::hd713332ae62141f3
   3:     0x7ffbcd57fbdd - std::panicking::take_hook::h78f8a454f3a4df82
   4:     0x7ffbcd57f66a - std::panicking::take_hook::h78f8a454f3a4df82
   5:     0x7ffba5661127 - rustc_driver::report_ice::h4bc3647b6f621de8
   6:     0x7ffbcd580730 - std::panicking::rust_panic_with_hook::h931fd6f26be82856
   7:     0x7ffbcd5801d3 - rust_begin_unwind
   8:     0x7ffbcd57c20f - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h106ca6f8fb6a294d
   9:     0x7ffbcd580159 - rust_begin_unwind
  10:     0x7ffbcd5a32f0 - core::panicking::panic_fmt::h45da916c710b88f7
  11:     0x7ffbcd5a323c - core::panicking::panic::h3a7a516f2be28c18
  12:     0x7ffba9902a70 - rustc_middle::ty::query::force_from_dep_node::h841e1a791cab1f4a
  13:     0x7ffba8d0a65a - <rustc_incremental::assert_dep_graph::GraphvizDepGraph as rustc_graphviz::Labeller>::node_label::h0377fe93b350976d
  14:     0x7ffba8d21410 - rustc_incremental::persist::fs::garbage_collect_session_directories::h8752c03e5176082c
  15:     0x7ffba8cd84d9 - rustc_incremental::persist::save::save_work_product_index::h9f355c816532590a
  16:     0x7ffba8cd4634 - punycode::encode::h3996edd3fcfd4e50
  17:     0x7ffba8d20ca9 - rustc_incremental::persist::fs::garbage_collect_session_directories::h8752c03e5176082c
  18:     0x7ffba8cd7715 - rustc_incremental::persist::save::save_dep_graph::h454bb9997b91eed7
  19:     0x7ffba8bf5790 - rustc_codegen_ssa::base::finalize_tcx::h0bd1f35d020d2bd3
  20:     0x7ffba5a74565 - <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate::h409f60e0ae4aaf13
  21:     0x7ffba5858ede - rustc_interface::interface::parse_cfgspecs::he4e421c50de55949
  22:     0x7ffba588d3da - rustc_interface::passes::BoxedResolver::to_resolver_outputs::hb096f93f8cf6df4c
  23:     0x7ffba58d5a46 - rustc_interface::queries::Queries::ongoing_codegen::ha9e2915cfb307d3a
  24:     0x7ffba5608b74 - <rustc_codegen_ssa::back::linker::MsvcLinker as rustc_codegen_ssa::back::linker::Linker>::no_crt_objects::h47dd01e667a15f55
  25:     0x7ffba5699aac - <rustc_driver::args::Error as core::fmt::Debug>::fmt::hb838ed2d57a61e3c
  26:     0x7ffba5609bfc - <rustc_codegen_ssa::back::linker::MsvcLinker as rustc_codegen_ssa::back::linker::Linker>::no_crt_objects::h47dd01e667a15f55
  27:     0x7ffba56b0f84 - <rustc_driver::args::Error as core::fmt::Debug>::fmt::hb838ed2d57a61e3c
  28:     0x7ffba56b8270 - rustc_ast::util::parser::prec_let_scrutinee_needs_par::h0da38a96661182e5
  29:     0x7ffba5612a3d - <rustc_codegen_ssa::back::linker::MsvcLinker as rustc_codegen_ssa::back::linker::Linker>::no_crt_objects::h47dd01e667a15f55
  30:     0x7ffbcd58f4f7 - std::sys::windows::thread::Thread::new::h05d768f6146b61f1
  31:     0x7ffc07127034 - BaseThreadInitThunk
  32:     0x7ffc07e9cec1 - RtlUserThreadStart

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-nightly (3d6705aa5 2020-12-07) running on x86_64-pc-windows-msvc

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin

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

query stack during panic:
end of query stack
warning: 2 warnings emitted

[ghost]

I'm pretty sure it's a cache issue; I took a look at the error location and it's in a function called try_load_from_on_disk_cache.

[ghost]

Having looked a little deeper, this is probably related to #79835.

[RustyYato]

Yeah, I've seen ICEs like this previously, which is why I saved all the build artifacts. That way I always have a repro

[camelid]

Looks like a duplicate of #79661.