ICE: failed to get layout

[matthiaskrgr]

Code

use std::mem;

pub struct S<T: Tr> {
    pub f: <T as Tr>::I,
}

pub trait Tr {
   type I: Tr;
}

impl<T: Tr> Tr for S<T> {
    type I = S<S<T>>;
}

impl Tr for () {
    type I = ();
}

fn foo<T: Tr>() -> usize {
    mem::size_of::<S<T>>()
}

fn main() {
    println!("{}", foo::<S<()>>());
}

Meta

rustc --version --verbose:

<version>

Error output

<output>

Backtrace

``` error[E0391]: cycle detected when computing layout of `S>` | = note: ...which requires computing layout of ` as Tr>::I`... = note: ...which again requires computing layout of `S>`, completing the cycle error: internal compiler error: compiler/rustc_codegen_llvm/src/context.rs:974:13: failed to get layout for `S>`: a cycle occurred during layout computation thread 'rustc' panicked at 'Box', /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/compiler/rustc_errors/src/lib.rs:994:33 stack backtrace: 0: 0x7f4c65369441 - std::backtrace_rs::backtrace::libunwind::trace::hb9be772067563b53 at /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5 1: 0x7f4c65369441 - std::backtrace_rs::backtrace::trace_unsynchronized::h031da30dc183647f at /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5 2: 0x7f4c65369441 - std::sys_common::backtrace::_print_fmt::h71eced90df8827aa at /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/library/std/src/sys_common/backtrace.rs:65:5 3: 0x7f4c65369441 - ::fmt::hae72971f9b1c0375 at /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/library/std/src/sys_common/backtrace.rs:44:22 4: 0x7f4c653ca0df - core::fmt::rt::Argument::fmt::h8155c503d36c9b86 at /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/library/core/src/fmt/rt.rs:138:9 5: 0x7f4c653ca0df - core::fmt::write::hbbb4251c2513c3ef at /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/library/core/src/fmt/mod.rs:1094:21 6: 0x7f4c6535c591 - std::io::Write::write_fmt::hdcff7ff4dad8c59b at /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/library/std/src/io/mod.rs:1712:15 7: 0x7f4c65369255 - std::sys_common::backtrace::_print::hb8bd80d5dffe8016 at /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/library/std/src/sys_common/backtrace.rs:47:5 8: 0x7f4c65369255 - std::sys_common::backtrace::print::hd57b6e007b7d9859 at /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/library/std/src/sys_common/backtrace.rs:34:9 9: 0x7f4c6536bee7 - std::panicking::default_hook::{{closure}}::h92b5b1db37900f49 10: 0x7f4c6536bcd4 - std::panicking::default_hook::h33b32947a165ebfe at /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/library/std/src/panicking.rs:288:9 11: 0x7f4c685707b5 - >::call_once::{shim:vtable#0} 12: 0x7f4c6536c607 - as core::ops::function::Fn>::call::h65038aad28115701 at /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/library/alloc/src/boxed.rs:1999:9 13: 0x7f4c6536c607 - std::panicking::rust_panic_with_hook::h6818a1a7c65e9cdd at /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/library/std/src/panicking.rs:695:13 14: 0x7f4c68402f91 - std[7223d5cfbaf62610]::panicking::begin_panic::::{closure#0} 15: 0x7f4c68401c26 - std[7223d5cfbaf62610]::sys_common::backtrace::__rust_end_short_backtrace::::{closure#0}, !> 16: 0x7f4c68401ac6 - std[7223d5cfbaf62610]::panicking::begin_panic:: 17: 0x7f4c683f6802 - ::span_bug:: 18: 0x7f4c683f5f46 - ::span_bug:: 19: 0x7f4c683faedd - rustc_middle[faa0e51d0d5710e5]::util::bug::opt_span_bug_fmt::::{closure#0} 20: 0x7f4c683faf0a - rustc_middle[faa0e51d0d5710e5]::ty::context::tls::with_opt::::{closure#0}, !>::{closure#0} 21: 0x7f4c683faaba - rustc_middle[faa0e51d0d5710e5]::ty::context::tls::with_context_opt::::{closure#0}, !>::{closure#0}, !> 22: 0x7f4c66d96d44 - rustc_middle[faa0e51d0d5710e5]::util::bug::span_bug_fmt:: 23: 0x7f4c6840d400 - ::handle_layout_err 24: 0x7f4c6840d312 - ::spanned_layout_of::{closure#0} 25: 0x7f4c66db0a4e - ::spanned_layout_of 26: 0x7f4c66da905f - >::codegen_rvalue_operand 27: 0x7f4c66d756bc - rustc_codegen_ssa[ec866eaa3e7fa1d8]::mir::codegen_mir:: 28: 0x7f4c67a12312 - rustc_codegen_llvm[f6e646cf3297fbe4]::base::compile_codegen_unit::module_codegen 29: 0x7f4c67a11160 - rustc_codegen_llvm[f6e646cf3297fbe4]::base::compile_codegen_unit 30: 0x7f4c67c55486 - rustc_codegen_ssa[ec866eaa3e7fa1d8]::base::codegen_crate:: 31: 0x7f4c67c54d52 - ::codegen_crate 32: 0x7f4c67803e90 - rustc_interface[145311d2418df64f]::passes::start_codegen 33: 0x7f4c677fef07 - ::enter::<::ongoing_codegen::{closure#0}::{closure#0}, core[65ac48eb02ee08bd]::result::Result, rustc_span[418048bff763fbc6]::ErrorGuaranteed>> 34: 0x7f4c677fe4e8 - ::ongoing_codegen 35: 0x7f4c677fdc23 - ::enter::, rustc_span[418048bff763fbc6]::ErrorGuaranteed>> 36: 0x7f4c677fb38f - std[7223d5cfbaf62610]::sys_common::backtrace::__rust_begin_short_backtrace::, rustc_driver_impl[2c3cd2b22615ac74]::run_compiler::{closure#1}>::{closure#0}, core[65ac48eb02ee08bd]::result::Result<(), rustc_span[418048bff763fbc6]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[65ac48eb02ee08bd]::result::Result<(), rustc_span[418048bff763fbc6]::ErrorGuaranteed>> 37: 0x7f4c67e59e9e - <::spawn_unchecked_, rustc_driver_impl[2c3cd2b22615ac74]::run_compiler::{closure#1}>::{closure#0}, core[65ac48eb02ee08bd]::result::Result<(), rustc_span[418048bff763fbc6]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[65ac48eb02ee08bd]::result::Result<(), rustc_span[418048bff763fbc6]::ErrorGuaranteed>>::{closure#1} as core[65ac48eb02ee08bd]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} 38: 0x7f4c65376ad5 - as core::ops::function::FnOnce>::call_once::haa143886c5139467 at /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/library/alloc/src/boxed.rs:1985:9 39: 0x7f4c65376ad5 - as core::ops::function::FnOnce>::call_once::ha0b7575cc93abe25 at /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/library/alloc/src/boxed.rs:1985:9 40: 0x7f4c65376ad5 - std::sys::unix::thread::Thread::new::thread_start::ha9600bcb75fadfd8 at /rustc/129195f57c02c8a8e4cfc4b766d4ff7a3a837882/library/std/src/sys/unix/thread.rs:108:17 41: 0x7f4c65112bb5 - 42: 0x7f4c65194d90 - 43: 0x0 - 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 1.71.0-nightly (129195f57 2023-05-04) running on x86_64-unknown-linux-gnu query stack during panic: end of query stack error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0391`. ```

[matthiaskrgr]

Regression in https://github.com/rust-lang/rust/pull/111097 :sweat_smile: cc @oli-obk

[oli-obk]

bwahaha, oh yea, code assuming layout computation can't fail... uh... we should change the sites where that happens to calling abort_if_errors instead of bug!

[matthiaskrgr]

tbh I find it a bit concerning that this did not trigger anything in our ci :/ The code originally is from https://github.com/rust-lang/rust/issues/22919 which was fixed in 2015

[oli-obk]

Our code coverage of rustc via its test suite is probably not very high in the error cases.

Do you have ideas for changing this fundamentally? I guess step 0 would be to actually generate coverage information

[matthiaskrgr]

hm, ./src/tools/miri/tests/fail/layout_cycle.rs would have failed if we had built it regularly with rustc, I guess the test pr that fixed https://github.com/rust-lang/rust/issues/22919 could also have added more tests.

[oli-obk]

I guess we could test all miri tests against miri and against rustc

[atsuzaki]

@rustbot claim

[atsuzaki]

(I think) this is the trait method that needs to change (most implementors directly return ! or just propagates the LayoutError). I'm not quite sure how to best change this. Perhaps just change it to no return?

https://github.com/rust-lang/rust/blob/ce042889f7f0d687368a9704eff64cf9542bac6d/compiler/rustc_middle/src/ty/layout.rs#L635-L648

[oli-obk]

you can make the ! returners always invoke span_fatal, irrespective of the LayoutError variant.