ICE: `Invalid bool 0x62` with associated_type_bounds

[matthiaskrgr]

rustc src/main.rs -Zcodegen-backend=cranelift -Zmir-opt-level=2

#![feature(associated_type_bounds)]

trait Tr1: Copy {
    type As1: Copy;
}

impl Tr1 for &str {
    type As1 = bool;
}

union Un3<T: Tr1<As1: 'static>> {
    outest: T,
    outer: &'static T::As1,
}

fn main() {
    let mut un3 = Un3 { outest: "baz" };

    assert_eq!(unsafe { *un3.outer }, true);
}

warning: variable does not need to be mutable
  --> src/main.rs:17:9
   |
17 |     let mut un3 = Un3 { outest: "baz" };
   |         ----^^^
   |         |
   |         help: remove this `mut`
   |
   = note: `#[warn(unused_mut)]` on by default

thread 'rustc' panicked at src/value_and_place.rs:318:13:
Invalid bool 0x62
stack backtrace:
   0:     0x7f569798b98c - std::backtrace_rs::backtrace::libunwind::trace::hdfc67f1e7ca3c26b
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
   1:     0x7f569798b98c - std::backtrace_rs::backtrace::trace_unsynchronized::heaa4a195a32ae345
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f569798b98c - std::sys_common::backtrace::_print_fmt::h4c39da8734214301
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x7f569798b98c - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hbf3d4e80620f48cb
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f56979de9c0 - core::fmt::rt::Argument::fmt::hc8377a2d1190c9aa
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/core/src/fmt/rt.rs:142:9
   5:     0x7f56979de9c0 - core::fmt::write::h92bfd03dd3380be9
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/core/src/fmt/mod.rs:1120:17
   6:     0x7f569797f84f - std::io::Write::write_fmt::hd1ba441fb09101d3
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/std/src/io/mod.rs:1766:15
   7:     0x7f569798b774 - std::sys_common::backtrace::_print::hd410e96536a9939b
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7f569798b774 - std::sys_common::backtrace::print::h4164b49f6454fc6a
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7f569798e407 - std::panicking::default_hook::{{closure}}::ha1a9f4255b168905
  10:     0x7f569798e16f - std::panicking::default_hook::hace399fd6c6ac32c
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/std/src/panicking.rs:292:9
  11:     0x7f569a6e48b0 - std[1dc220fc4c0ef824]::panicking::update_hook::<alloc[1aeee6991bd49b3f]::boxed::Box<rustc_driver_impl[45fab285649c23b2]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x7f569798eb48 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hfb05686be3af21d4
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/alloc/src/boxed.rs:2021:9
  13:     0x7f569798eb48 - std::panicking::rust_panic_with_hook::h687a0dbad3543b4f
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/std/src/panicking.rs:783:13
  14:     0x7f569798e89e - std::panicking::begin_panic_handler::{{closure}}::h0e1063442cc3cc04
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/std/src/panicking.rs:657:13
  15:     0x7f569798be56 - std::sys_common::backtrace::__rust_end_short_backtrace::h121fc3b3bde77e14
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/std/src/sys_common/backtrace.rs:171:18
  16:     0x7f569798e602 - rust_begin_unwind
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/std/src/panicking.rs:645:5
  17:     0x7f56979db0a5 - core::panicking::panic_fmt::h087e25bd2388ac03
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/core/src/panicking.rs:72:14
  18:     0x7f568e057655 - <rustc_codegen_cranelift[1e1ab29f9bae4b04]::value_and_place::CValue>::const_val
  19:     0x7f568e0188f8 - rustc_codegen_cranelift[1e1ab29f9bae4b04]::constant::codegen_const_value
  20:     0x7f568e011c07 - rustc_codegen_cranelift[1e1ab29f9bae4b04]::base::codegen_operand
  21:     0x7f568e00862f - rustc_codegen_cranelift[1e1ab29f9bae4b04]::base::codegen_fn_body
  22:     0x7f568e02283a - rustc_codegen_cranelift[1e1ab29f9bae4b04]::driver::aot::module_codegen::{closure#0}
  23:     0x7f568e01f9d5 - rustc_codegen_cranelift[1e1ab29f9bae4b04]::driver::aot::module_codegen
  24:     0x7f568e02c17c - rustc_codegen_cranelift[1e1ab29f9bae4b04]::driver::aot::run_aot
  25:     0x7f568e05abda - <rustc_codegen_cranelift[1e1ab29f9bae4b04]::CraneliftCodegenBackend as rustc_codegen_ssa[a0c122d06cf22e6d]::traits::backend::CodegenBackend>::codegen_crate
  26:     0x7f569c391705 - rustc_interface[56e8e5a742480a4b]::passes::start_codegen
  27:     0x7f569c390e5f - <rustc_interface[56e8e5a742480a4b]::queries::Queries>::codegen_and_build_linker
  28:     0x7f569c737e5c - rustc_interface[56e8e5a742480a4b]::interface::run_compiler::<core[d0ccb57ccfd673f9]::result::Result<(), rustc_span[476eee35b566d70f]::ErrorGuaranteed>, rustc_driver_impl[45fab285649c23b2]::run_compiler::{closure#0}>::{closure#0}
  29:     0x7f569c979ad4 - std[1dc220fc4c0ef824]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[56e8e5a742480a4b]::util::run_in_thread_with_globals<rustc_interface[56e8e5a742480a4b]::util::run_in_thread_pool_with_globals<rustc_interface[56e8e5a742480a4b]::interface::run_compiler<core[d0ccb57ccfd673f9]::result::Result<(), rustc_span[476eee35b566d70f]::ErrorGuaranteed>, rustc_driver_impl[45fab285649c23b2]::run_compiler::{closure#0}>::{closure#0}, core[d0ccb57ccfd673f9]::result::Result<(), rustc_span[476eee35b566d70f]::ErrorGuaranteed>>::{closure#0}, core[d0ccb57ccfd673f9]::result::Result<(), rustc_span[476eee35b566d70f]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[d0ccb57ccfd673f9]::result::Result<(), rustc_span[476eee35b566d70f]::ErrorGuaranteed>>
  30:     0x7f569c9798fd - <<std[1dc220fc4c0ef824]::thread::Builder>::spawn_unchecked_<rustc_interface[56e8e5a742480a4b]::util::run_in_thread_with_globals<rustc_interface[56e8e5a742480a4b]::util::run_in_thread_pool_with_globals<rustc_interface[56e8e5a742480a4b]::interface::run_compiler<core[d0ccb57ccfd673f9]::result::Result<(), rustc_span[476eee35b566d70f]::ErrorGuaranteed>, rustc_driver_impl[45fab285649c23b2]::run_compiler::{closure#0}>::{closure#0}, core[d0ccb57ccfd673f9]::result::Result<(), rustc_span[476eee35b566d70f]::ErrorGuaranteed>>::{closure#0}, core[d0ccb57ccfd673f9]::result::Result<(), rustc_span[476eee35b566d70f]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[d0ccb57ccfd673f9]::result::Result<(), rustc_span[476eee35b566d70f]::ErrorGuaranteed>>::{closure#1} as core[d0ccb57ccfd673f9]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  31:     0x7f56979989e5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h16241ade875ace78
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/alloc/src/boxed.rs:2007:9
  32:     0x7f56979989e5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h0d92a7e8b2e21f1b
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/alloc/src/boxed.rs:2007:9
  33:     0x7f56979989e5 - std::sys::unix::thread::Thread::new::thread_start::h9e600b3dd7be7655
                               at /rustc/f5dc2653fdd8b5d177b2ccbd84057954340a89fc/library/std/src/sys/unix/thread.rs:108:17
  34:     0x7f56977899eb - <unknown>
  35:     0x7f569780d7cc - <unknown>
  36:                0x0 - <unknown>

error: 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: please attach the file at `/tmp/im/f/rustc-ice-2023-11-27T10_34_27-3324716.txt` to your bug report

note: compiler flags: -Z codegen-backend=cranelift -Z mir-opt-level=2

query stack during panic:
end of query stack
stmt _3 = const {transmute(0x62): bool}
fn main() -> () {
    let mut _0: ();
    let mut _1: Un3<&str>;
    let mut _2: &bool;
    let _3: bool;
    let mut _4: bool;
    let mut _5: bool;
    let _6: !;
    let mut _7: std::option::Option<std::fmt::Arguments<'_>>;
    scope 1 {
        debug un3 => _1;
        let mut _8: &bool;
        scope 2 {
        }
        scope 3 {
            debug left_val => _2;
            debug right_val => const _;
            scope 4 {
                debug kind => const core::panicking::AssertKind::Eq;
            }
        }
    }

    bb0: {
        _1 = Un3::<&str> { outest: const "baz" };
        _3 = const {transmute(0x62): bool};
        _2 = &_3;
        _8 = const _;
        _5 = (*_2);
        _4 = Eq(move _5, const true);
        switchInt(move _4) -> [0: bb2, otherwise: bb1];
    }

    bb1: {
        return;
    }

    bb2: {
        _7 = std::option::Option::<std::fmt::Arguments<'_>>::None;
        _6 = core::panicking::assert_failed::<bool, bool>(const core::panicking::AssertKind::Eq, move _2, move _8, move _7) -> unwind continue;
    }
}

[matthiaskrgr]

woth noting that miri rejects this as UB

error: Undefined Behavior: constructing invalid value: encountered 0x62, but expected a boolean --> src/main.rs:19:25	19	assert_eq!(unsafe { *un3.outer }, true);	^^^^^^^^^^ constructing invalid value: encountered 0x62, but expected a boolean

[bjorn3]

I can't reproduce this with latest cg_clif. I don't know if it is fixed now or if I did something wrong.

[matthiaskrgr]

fn main() {
    let b = unsafe { std::mem::transmute::<u8, bool>(2) };
    let _x = b == std::hint::black_box(true); //~ ERROR: interpreting an invalid 8-bit value as a bool
}

with Zcodegen-backend=cranelift -Zmir-opt-level=2 still repros this