ICE during migration to Rust 2021, crate: stm32h7xx-hal

[hargoniX]

Code

Regarding a minimal example I am afraid I'm not quite able to provide one, this bug occured when i was migrating
https://github.com/stm32-rs/stm32h7xx-hal to Rust 2021 as part of the testing efforts. The branch/PR with the
Rust 2021 modifications can be found here stm32-rs/stm32h7xx-hal#236. I did cfgment all
modules except the ones that are required to trigger the bug out: https://github.com/stm32-rs/stm32h7xx-hal/blob/rust2021/src/lib.rs#L250-L253. And removed most code and modules from the rcc module: https://github.com/stm32-rs/stm32h7xx-hal/blob/rust2021/src/rcc/mod.rs#L144-L155, nailing the bug down to src/rcc/pll.rs (as the error message suggested). Then i minized further in pll.rs (its 200 lines now, the rest is just tests) And I was in fact able to pin point the panic to this piece of code:
https://github.com/stm32-rs/stm32h7xx-hal/blob/rust2021/src/rcc/pll.rs#L95-L104, if I comment it out the ICE doesn't occur anymore so I would guess that this is what the compiler is having issues with.

Meta

rustc --version --verbose:

rustc 1.55.0-nightly (67b03007c 2021-07-23)
binary: rustc
commit-hash: 67b03007cf40f2331892d5b0f65d2917ac3603d5
commit-date: 2021-07-23
host: x86_64-unknown-linux-gnu
release: 1.55.0-nightly
LLVM version: 12.0.1

Error output

Compilation command I used was: cargo +nightly build --features=rt,stm32h743

<warnings about unused variables because of my minimization>

thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', compiler/rustc_mir_build/src/build/matches/mod.rs:1685:53
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 1.55.0-nightly (67b03007c 2021-07-23) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z unstable-options -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2 -C link-arg=-Tlink.x --crate-type lib

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

query stack during panic:
#0 [mir_built] building MIR for `rcc::pll::<impl at src/rcc/pll.rs:189:1: 199:2>::pll1_setup::{closure#1}`
#1 [unsafety_check_result] unsafety-checking `rcc::pll::<impl at src/rcc/pll.rs:189:1: 199:2>::pll1_setup::{closure#1}`
end of query stack
warning: `stm32h7xx-hal` (lib) generated 5 warnings
error: could not compile `stm32h7xx-hal`; 5 warnings emitted

Backtrace

thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', compiler/rustc_mir_build/src/build/matches/mod.rs:1685:53
stack backtrace:
   0: rust_begin_unwind
             at /rustc/67b03007cf40f2331892d5b0f65d2917ac3603d5/library/std/src/panicking.rs:515:5
   1: core::panicking::panic_fmt
             at /rustc/67b03007cf40f2331892d5b0f65d2917ac3603d5/library/core/src/panicking.rs:92:14
   2: core::panicking::panic
             at /rustc/67b03007cf40f2331892d5b0f65d2917ac3603d5/library/core/src/panicking.rs:50:5
   3: rustc_mir_build::build::matches::<impl rustc_mir_build::build::Builder>::bind_and_guard_matched_candidate
   4: rustc_mir_build::build::matches::<impl rustc_mir_build::build::Builder>::bind_pattern
   5: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
   6: <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
   7: alloc::vec::source_iter_marker::<impl alloc::vec::spec_from_iter::SpecFromIter<T,I> for alloc::vec::Vec<T>>::from_iter
   8: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::expr_into_dest
   9: rustc_mir_build::build::expr::as_temp::<impl rustc_mir_build::build::Builder>::as_temp_inner
  10: rustc_mir_build::build::expr::as_place::<impl rustc_mir_build::build::Builder>::expr_as_place
  11: rustc_mir_build::build::expr::as_place::<impl rustc_mir_build::build::Builder>::expr_as_place
  12: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::expr_into_dest
  13: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
  14: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::expr_into_dest
  15: rustc_mir_build::build::block::<impl rustc_mir_build::build::Builder>::ast_block_stmts
  16: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
  17: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::expr_into_dest
  18: rustc_mir_build::build::expr::as_temp::<impl rustc_mir_build::build::Builder>::as_temp_inner
  19: rustc_mir_build::build::expr::as_place::<impl rustc_mir_build::build::Builder>::expr_as_place
  20: rustc_mir_build::build::expr::as_place::<impl rustc_mir_build::build::Builder>::expr_as_place
  21: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::expr_into_dest
  22: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
  23: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::expr_into_dest
  24: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
  25: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::expr_into_dest
  26: rustc_mir_build::build::construct_fn
  27: rustc_infer::infer::InferCtxtBuilder::enter
  28: rustc_mir_build::build::mir_built
  29: rustc_query_system::query::plumbing::get_query_impl
  30: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::mir_built
  31: rustc_mir::transform::check_unsafety::unsafety_check_result
  32: core::ops::function::FnOnce::call_once
  33: rustc_query_system::query::plumbing::get_query_impl
  34: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::unsafety_check_result
  35: rustc_mir::transform::mir_const
  36: rustc_query_system::query::plumbing::get_query_impl
  37: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::mir_const
  38: rustc_mir::transform::mir_promoted
  39: rustc_query_system::query::plumbing::get_query_impl
  40: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::mir_promoted
  41: rustc_mir::borrow_check::mir_borrowck
  42: core::ops::function::FnOnce::call_once
  43: rustc_query_system::query::plumbing::get_query_impl
  44: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::mir_borrowck
  45: rustc_middle::ty::<impl rustc_middle::ty::context::TyCtxt>::par_body_owners
  46: rustc_interface::passes::analysis
  47: rustc_query_system::query::plumbing::get_query_impl
  48: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::analysis
  49: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  50: rustc_span::with_source_map
  51: rustc_interface::interface::create_compiler_and_run
  52: scoped_tls::ScopedKey<T>::set
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 1.55.0-nightly (67b03007c 2021-07-23) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z unstable-options -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2 -C link-arg=-Tlink.x --crate-type lib

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

query stack during panic:
#0 [mir_built] building MIR for `rcc::pll::<impl at src/rcc/pll.rs:189:1: 199:2>::pll1_setup::{closure#1}`
#1 [unsafety_check_result] unsafety-checking `rcc::pll::<impl at src/rcc/pll.rs:189:1: 199:2>::pll1_setup::{closure#1}`
#2 [mir_const] processing MIR for `rcc::pll::<impl at src/rcc/pll.rs:189:1: 199:2>::pll1_setup::{closure#1}`
#3 [mir_promoted] processing `rcc::pll::<impl at src/rcc/pll.rs:189:1: 199:2>::pll1_setup::{closure#1}`
#4 [mir_borrowck] borrow-checking `rcc::pll::<impl at src/rcc/pll.rs:189:1: 199:2>::pll1_setup::{closure#1}`
#5 [analysis] running analysis passes on this crate
end of query stack

[ehuss]

Thanks for the report! Here's a somewhat minimized reproduction:

pub fn foo() {
    let ref_x_ck = 123;
    let _y = || match ref_x_ck {
        2_000_000..=3_999_999 => {}
        _ => {}
    };
}

[ehuss]

cc @rust-lang/wg-rfc-2229

[roxelo]

@rustbot claim