ICE: `expected bits of u8, got Ty(10_u32,)`

[cushionbadak]

Code

(reduced)

trait Range {
    const FIRST: u8;
    const LAST: u8;
}

struct TwoDigits;
impl Range for TwoDigits {
    const FIRST:  = 10;
    const LAST: u8 = 99;
}

fn digits(x: u8) -> u32 {
    match x {
        TwoDigits::FIRST..=TwoDigits::LAST => 2,
    }
}

fn main() {}

Note: type notation at const FIRST: in TwoDigits is omitted. I guess that causes ICE

Original Code

//@ run-pass

#![allow(dead_code)]

trait Range {
    const FIRST: u8;
    const LAST: u8;
}

struct OneDigit;
impl Range for OneDigit {
    const FIRST: u8 = 0;
    const LAST: u8 = 9;
}

struct TwoDigits;
impl Range for TwoDigits {
    const FIRST:  = 10;
    const LAST: u8 = 99;
}

struct ThreeDigits;
impl Range for ThreeDigits {
    const FIRST: u8 = 100;
    const LAST: u8 = 255;
}

fn digits(x: u8) -> u32 {
    match x {
        OneDigit::FIRST..=OneDigit::LAST => 1,
        TwoDigits::FIRST..=TwoDigits::LAST => 2,
        ThreeDigits::FIRST..=ThreeDigits::LAST => 3,
    }
}

fn main() {
    assert_eq!(digits(100), 3);
}

Meta

rustc --version --verbose:

rustc 1.79.0-nightly (5f2c7d2bf 2024-03-25)
binary: rustc
commit-hash: 5f2c7d2bfd46cad00352ab7cd66242077e2e518c
commit-date: 2024-03-25
host: x86_64-apple-darwin
release: 1.79.0-nightly
LLVM version: 18.1.2

Command

rustc, no other options

Error output

error: missing type for `const` item
 --> reduced_23439712.rs:8:17
  |
8 |     const FIRST:  = 10;
  |                 ^ help: provide a type for the associated constant: `i32`

Backtrace

error: internal compiler error: /rustc/5f2c7d2bfd46cad00352ab7cd66242077e2e518c/compiler/rustc_middle/src/mir/consts.rs:344:32: expected bits of u8, got Ty(
                                    10_u32,
                                )

thread 'rustc' panicked at /rustc/5f2c7d2bfd46cad00352ab7cd66242077e2e518c/compiler/rustc_middle/src/mir/consts.rs:344:32:
Box<dyn Any>
stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
   1: <rustc_errors::diagnostic::BugAbort as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
   2: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>::{closure#0}
   3: rustc_middle::ty::context::tls::with_opt::<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}
   4: rustc_middle::ty::context::tls::with_context_opt::<rustc_middle::ty::context::tls::with_opt<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
   5: rustc_middle::util::bug::bug_fmt
   6: <rustc_pattern_analysis::rustc::RustcPatCtxt>::lower_pat_range_bdy
   7: <rustc_pattern_analysis::rustc::RustcPatCtxt>::lower_pat
   8: <rustc_mir_build::thir::pattern::check_match::MatchVisitor>::lower_pattern
   9: <rustc_mir_build::thir::pattern::check_match::MatchVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
  10: <rustc_mir_build::thir::pattern::check_match::MatchVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
  11: rustc_middle::thir::visit::walk_block::<rustc_mir_build::thir::pattern::check_match::MatchVisitor>
  12: <rustc_mir_build::thir::pattern::check_match::MatchVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
  13: <rustc_mir_build::thir::pattern::check_match::MatchVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
  14: rustc_mir_build::thir::pattern::check_match::check_match
      [... omitted 1 frame ...]
  15: rustc_mir_build::build::mir_build
  16: rustc_mir_transform::mir_built
      [... omitted 1 frame ...]
  17: rustc_mir_build::check_unsafety::check_unsafety
      [... omitted 1 frame ...]
  18: <rustc_middle::hir::map::Map>::par_body_owners::<rustc_interface::passes::analysis::{closure#1}::{closure#0}>::{closure#0}
  19: rustc_interface::passes::analysis
      [... omitted 1 frame ...]
  20: <rustc_interface::queries::QueryResult<&rustc_middle::ty::context::GlobalCtxt>>::enter::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}::{closure#1}::{closure#3}>
  21: rustc_interface::interface::run_compiler::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

note: it seems that this compiler `1.79.0-nightly (5f2c7d2bf 2024-03-25)` is outdated, a newer nightly should have been released in the mean time
  |
  = note: please consider running `rustup update nightly` to update the nightly channel and check if this problem still persists
  = note: if the problem still persists, 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: please attach the file at `/Volumes/T7/workspace/placeholder_rustexec/rustc-ice-2024-03-26T12_13_20-28368.txt` to your bug report

query stack during panic:
#0 [check_match] match-checking `digits`
#1 [mir_built] building MIR for `digits`
#2 [check_unsafety] unsafety-checking `digits`
#3 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 2 previous errors

Related Issues

• generic_const_exprs ICE with nested generic params #118244 and ICE with generic_const_exprs: expected bits of usize, got (Sub: 2_usize, 1_usize): usize #116637
  • Their ICEs are at fn eval_bits in compiler/rustc_middle/src/ty/consts.rs, and this ICE occured at fn eval_bits in compiler/rustc_middle/src/mir/consts.rs.
  • compiler/rustc_middle/src/ty/consts.rs (ICE-loc link for #118244),
  • compiler/rustc_middle/src/mir/consts.rs (ICE-loc link for this issue)

[GrigorenkoPV]

Regression in #120550, but I guess it is already known.

[oli-obk]

#120550 only exposed it more easily, the ICE can also be triggered on stable by invoking the function in an array length:

trait Range {
    const FIRST: u8;
    const LAST: u8;
}

struct TwoDigits;
impl Range for TwoDigits {
    const FIRST:  = 10;
    const LAST: u8 = 99;
}

const fn digits(x: u8) -> usize {
    match x {
        TwoDigits::FIRST..=TwoDigits::LAST => 0,
    }
}

const FOOMP: [(); {
    digits(42)
}] = [];

[oli-obk]

trait Range {
    const FIRST: u8;
    const LAST: u8;
}

struct TwoDigits;
impl Range for TwoDigits {
    const FIRST:  = 10;
    const LAST: u8 = 99;
}

const FOOMP: [(); {
    TwoDigits::FIRST as usize
}] = [];

has been ICEing with different messages since 1.23 (edit: but isn't ICEing anymore, edit: scalar size mismatch should be an ICE, not an error, huh?)

Further bisection can be done, but is probably not useful. I'll just fix the bug 😆