ICE: `Failed to normalize Alias(Projection, AliasTy ..`

[matthiaskrgr]

Code

trait Trait {
    type RefTarget;
}

impl Trait for () where Missing: Trait {}

struct Other {
    data: <() as Trait>::RefTarget,
}

fn main() {
    unsafe {
        std::mem::transmute::<Option<()>, Option<&Other>>(None);
    }
}

Meta

rustc --version --verbose:

rustc 1.72.0-nightly (5bd28f5ea 2023-06-28)
binary: rustc
commit-hash: 5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0
commit-date: 2023-06-28
host: x86_64-unknown-linux-gnu
release: 1.72.0-nightly
LLVM version: 16.0.5

Error output

<output>

Backtrace

error[E0412]: cannot find type `Missing` in this scope
 --> treereduce.out:5:25
  |
5 | impl Trait for () where Missing: Trait {}
  |                         ^^^^^^^ not found in this scope

error[E0046]: not all trait items implemented, missing: `RefTarget`
 --> treereduce.out:5:1
  |
2 |     type RefTarget;
  |     -------------- `RefTarget` from trait
...
5 | impl Trait for () where Missing: Trait {}
  | ^^^^^^^^^^^^^^^^^ missing `RefTarget` in implementation

error: internal compiler error: compiler/rustc_middle/src/ty/normalize_erasing_regions.rs:195:90: Failed to normalize <() as Trait>::RefTarget, maybe try to call `try_normalize_erasing_regions` instead

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/compiler/rustc_errors/src/lib.rs:1650:9
stack backtrace:
   0:     0x7f645761be31 - std::backtrace_rs::backtrace::libunwind::trace::h8bc3e596fd6e6181
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7f645761be31 - std::backtrace_rs::backtrace::trace_unsynchronized::h9a0656fedca2f962
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f645761be31 - std::sys_common::backtrace::_print_fmt::h11ca79bc953fda0e
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/std/src/sys_common/backtrace.rs:65:5
   3:     0x7f645761be31 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h23585af82c540d61
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f645767d5df - core::fmt::rt::Argument::fmt::h1e7f4bcecbee3fbb
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/core/src/fmt/rt.rs:138:9
   5:     0x7f645767d5df - core::fmt::write::h41633f265152b738
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/core/src/fmt/mod.rs:1094:21
   6:     0x7f645760e967 - std::io::Write::write_fmt::hdf9fdeebf4391d4c
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/std/src/io/mod.rs:1714:15
   7:     0x7f645761bc45 - std::sys_common::backtrace::_print::h0761f433dadea582
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7f645761bc45 - std::sys_common::backtrace::print::hffcd468cc9baf957
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7f645761e9f3 - std::panicking::default_hook::{{closure}}::h70eb212f41458c90
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/std/src/panicking.rs:269:22
  10:     0x7f645761e784 - std::panicking::default_hook::hf217f8886a1385fc
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/std/src/panicking.rs:288:9
  11:     0x7f645642217b - <rustc_driver_impl[ea51492c730803db]::install_ice_hook::{closure#0} as core[6e72eb595340d7ba]::ops::function::FnOnce<(&core[6e72eb595340d7ba]::panic::panic_info::PanicInfo,)>>::call_once::{shim:vtable#0}
  12:     0x7f645761f21e - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hdf84d12f536c7065
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/alloc/src/boxed.rs:2024:9
  13:     0x7f645761f21e - std::panicking::rust_panic_with_hook::h7901b0073bb3ed74
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/std/src/panicking.rs:709:13
  14:     0x7f64568f6d91 - std[4a840e81aae3439]::panicking::begin_panic::<rustc_errors[74566eb9727f9d9c]::ExplicitBug>::{closure#0}
  15:     0x7f64568f5106 - std[4a840e81aae3439]::sys_common::backtrace::__rust_end_short_backtrace::<std[4a840e81aae3439]::panicking::begin_panic<rustc_errors[74566eb9727f9d9c]::ExplicitBug>::{closure#0}, !>
  16:     0x7f64568f4626 - std[4a840e81aae3439]::panicking::begin_panic::<rustc_errors[74566eb9727f9d9c]::ExplicitBug>
  17:     0x7f645696ae94 - <rustc_errors[74566eb9727f9d9c]::HandlerInner>::bug::<alloc[6fd48550c51b5745]::string::String>
  18:     0x7f645696ad16 - <rustc_errors[74566eb9727f9d9c]::Handler>::bug::<alloc[6fd48550c51b5745]::string::String>
  19:     0x7f64568f204c - rustc_middle[9f74ec5cb00a905a]::util::bug::opt_span_bug_fmt::<rustc_span[624dabdd61f2978b]::span_encoding::Span>::{closure#0}
  20:     0x7f64568f1f8a - rustc_middle[9f74ec5cb00a905a]::ty::context::tls::with_opt::<rustc_middle[9f74ec5cb00a905a]::util::bug::opt_span_bug_fmt<rustc_span[624dabdd61f2978b]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  21:     0x7f64568f1f5a - rustc_middle[9f74ec5cb00a905a]::ty::context::tls::with_context_opt::<rustc_middle[9f74ec5cb00a905a]::ty::context::tls::with_opt<rustc_middle[9f74ec5cb00a905a]::util::bug::opt_span_bug_fmt<rustc_span[624dabdd61f2978b]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  22:     0x7f645488cc4d - rustc_middle[9f74ec5cb00a905a]::util::bug::bug_fmt
  23:     0x7f64549cf295 - <rustc_middle[9f74ec5cb00a905a]::ty::normalize_erasing_regions::NormalizeAfterErasingRegionsFolder>::normalize_generic_arg_after_erasing_regions
  24:     0x7f64549cef43 - <rustc_middle[9f74ec5cb00a905a]::ty::Ty as rustc_type_ir[2174c24ce5957ab4]::fold::TypeFoldable<rustc_middle[9f74ec5cb00a905a]::ty::context::TyCtxt>>::fold_with::<rustc_middle[9f74ec5cb00a905a]::ty::normalize_erasing_regions::NormalizeAfterErasingRegionsFolder>
  25:     0x7f6454c26fec - <rustc_middle[9f74ec5cb00a905a]::ty::context::TyCtxt>::struct_tail_erasing_lifetimes
  26:     0x7f64554e6d15 - <rustc_middle[9f74ec5cb00a905a]::ty::layout::SizeSkeleton>::compute
  27:     0x7f645690e0c1 - <rustc_middle[9f74ec5cb00a905a]::ty::layout::SizeSkeleton>::compute::{closure#1}
  28:     0x7f64554e6fd7 - <rustc_middle[9f74ec5cb00a905a]::ty::layout::SizeSkeleton>::compute
  29:     0x7f64559e88f2 - <rustc_hir_typeck[510371791de31c85]::fn_ctxt::FnCtxt>::check_transmute
  30:     0x7f6454d17195 - rustc_hir_typeck[510371791de31c85]::typeck
  31:     0x7f64544533ee - rustc_query_impl[a5bf74a69bd3660]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a5bf74a69bd3660]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[9f74ec5cb00a905a]::query::erase::Erased<[u8; 8usize]>>
  32:     0x7f64544533be - <rustc_query_impl[a5bf74a69bd3660]::query_impl::typeck::dynamic_query::{closure#2} as core[6e72eb595340d7ba]::ops::function::FnOnce<(rustc_middle[9f74ec5cb00a905a]::ty::context::TyCtxt, rustc_span[624dabdd61f2978b]::def_id::LocalDefId)>>::call_once
  33:     0x7f645452891d - rustc_query_system[d65e888f3fe19f8d]::query::plumbing::try_execute_query::<rustc_query_impl[a5bf74a69bd3660]::DynamicConfig<rustc_query_system[d65e888f3fe19f8d]::query::caches::VecCache<rustc_span[624dabdd61f2978b]::def_id::LocalDefId, rustc_middle[9f74ec5cb00a905a]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[a5bf74a69bd3660]::plumbing::QueryCtxt, false>
  34:     0x7f6455dce971 - rustc_query_impl[a5bf74a69bd3660]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  35:     0x7f64545a5bad - rustc_query_impl[a5bf74a69bd3660]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a5bf74a69bd3660]::query_impl::used_trait_imports::dynamic_query::{closure#2}::{closure#0}, rustc_middle[9f74ec5cb00a905a]::query::erase::Erased<[u8; 8usize]>>
  36:     0x7f64545a5b0e - <rustc_query_impl[a5bf74a69bd3660]::query_impl::used_trait_imports::dynamic_query::{closure#2} as core[6e72eb595340d7ba]::ops::function::FnOnce<(rustc_middle[9f74ec5cb00a905a]::ty::context::TyCtxt, rustc_span[624dabdd61f2978b]::def_id::LocalDefId)>>::call_once
  37:     0x7f645452891d - rustc_query_system[d65e888f3fe19f8d]::query::plumbing::try_execute_query::<rustc_query_impl[a5bf74a69bd3660]::DynamicConfig<rustc_query_system[d65e888f3fe19f8d]::query::caches::VecCache<rustc_span[624dabdd61f2978b]::def_id::LocalDefId, rustc_middle[9f74ec5cb00a905a]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[a5bf74a69bd3660]::plumbing::QueryCtxt, false>
  38:     0x7f6455daa741 - rustc_query_impl[a5bf74a69bd3660]::query_impl::used_trait_imports::get_query_non_incr::__rust_end_short_backtrace
  39:     0x7f64558f4af0 - rustc_hir_analysis[5549e2304bca0734]::check_unused::check_crate
  40:     0x7f64558f1e31 - rustc_hir_analysis[5549e2304bca0734]::check_crate
  41:     0x7f64558ea91a - rustc_interface[b943f00ad50b5541]::passes::analysis
  42:     0x7f6455933aba - rustc_query_impl[a5bf74a69bd3660]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a5bf74a69bd3660]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[9f74ec5cb00a905a]::query::erase::Erased<[u8; 1usize]>>
  43:     0x7f6455933aa9 - <rustc_query_impl[a5bf74a69bd3660]::query_impl::analysis::dynamic_query::{closure#2} as core[6e72eb595340d7ba]::ops::function::FnOnce<(rustc_middle[9f74ec5cb00a905a]::ty::context::TyCtxt, ())>>::call_once
  44:     0x7f6455ab2da8 - rustc_query_system[d65e888f3fe19f8d]::query::plumbing::try_execute_query::<rustc_query_impl[a5bf74a69bd3660]::DynamicConfig<rustc_query_system[d65e888f3fe19f8d]::query::caches::SingleCache<rustc_middle[9f74ec5cb00a905a]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[a5bf74a69bd3660]::plumbing::QueryCtxt, false>
  45:     0x7f6455ab2b79 - rustc_query_impl[a5bf74a69bd3660]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  46:     0x7f6455a86a55 - <rustc_middle[9f74ec5cb00a905a]::ty::context::GlobalCtxt>::enter::<rustc_driver_impl[ea51492c730803db]::run_compiler::{closure#1}::{closure#2}::{closure#4}, core[6e72eb595340d7ba]::result::Result<(), rustc_span[624dabdd61f2978b]::ErrorGuaranteed>>
  47:     0x7f64556b9341 - <rustc_interface[b943f00ad50b5541]::interface::Compiler>::enter::<rustc_driver_impl[ea51492c730803db]::run_compiler::{closure#1}::{closure#2}, core[6e72eb595340d7ba]::result::Result<core[6e72eb595340d7ba]::option::Option<rustc_interface[b943f00ad50b5541]::queries::Linker>, rustc_span[624dabdd61f2978b]::ErrorGuaranteed>>
  48:     0x7f64556b4575 - rustc_span[624dabdd61f2978b]::set_source_map::<core[6e72eb595340d7ba]::result::Result<(), rustc_span[624dabdd61f2978b]::ErrorGuaranteed>, rustc_interface[b943f00ad50b5541]::interface::run_compiler<core[6e72eb595340d7ba]::result::Result<(), rustc_span[624dabdd61f2978b]::ErrorGuaranteed>, rustc_driver_impl[ea51492c730803db]::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
  49:     0x7f64556b3996 - <scoped_tls[8088cff701f74b4a]::ScopedKey<rustc_span[624dabdd61f2978b]::SessionGlobals>>::set::<rustc_interface[b943f00ad50b5541]::interface::run_compiler<core[6e72eb595340d7ba]::result::Result<(), rustc_span[624dabdd61f2978b]::ErrorGuaranteed>, rustc_driver_impl[ea51492c730803db]::run_compiler::{closure#1}>::{closure#0}, core[6e72eb595340d7ba]::result::Result<(), rustc_span[624dabdd61f2978b]::ErrorGuaranteed>>
  50:     0x7f64556b2f46 - std[4a840e81aae3439]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[b943f00ad50b5541]::util::run_in_thread_pool_with_globals<rustc_interface[b943f00ad50b5541]::interface::run_compiler<core[6e72eb595340d7ba]::result::Result<(), rustc_span[624dabdd61f2978b]::ErrorGuaranteed>, rustc_driver_impl[ea51492c730803db]::run_compiler::{closure#1}>::{closure#0}, core[6e72eb595340d7ba]::result::Result<(), rustc_span[624dabdd61f2978b]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[6e72eb595340d7ba]::result::Result<(), rustc_span[624dabdd61f2978b]::ErrorGuaranteed>>
  51:     0x7f64556b2cee - <<std[4a840e81aae3439]::thread::Builder>::spawn_unchecked_<rustc_interface[b943f00ad50b5541]::util::run_in_thread_pool_with_globals<rustc_interface[b943f00ad50b5541]::interface::run_compiler<core[6e72eb595340d7ba]::result::Result<(), rustc_span[624dabdd61f2978b]::ErrorGuaranteed>, rustc_driver_impl[ea51492c730803db]::run_compiler::{closure#1}>::{closure#0}, core[6e72eb595340d7ba]::result::Result<(), rustc_span[624dabdd61f2978b]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[6e72eb595340d7ba]::result::Result<(), rustc_span[624dabdd61f2978b]::ErrorGuaranteed>>::{closure#1} as core[6e72eb595340d7ba]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  52:     0x7f6457629695 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h61eb867555625a06
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/alloc/src/boxed.rs:2010:9
  53:     0x7f6457629695 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hb80c29f89b136b72
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/alloc/src/boxed.rs:2010:9
  54:     0x7f6457629695 - std::sys::unix::thread::Thread::new::thread_start::hf4205715d65b27a6
                               at /rustc/5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0/library/std/src/sys/unix/thread.rs:108:17
  55:     0x7f645309644b - <unknown>
  56:     0x7f6453119e40 - <unknown>
  57:                0x0 - <unknown>

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 1.72.0-nightly (5bd28f5ea 2023-06-28) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [typeck] type-checking `main`
#1 [used_trait_imports] finding used_trait_imports `main`
#2 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 3 previous errors

Some errors have detailed explanations: E0046, E0412.
For more information about an error, try `rustc --explain E0046`.

[matthiaskrgr]

Regression in nightly-2022-05-28

found 8 bors merge commits in the specified range
  commit[0] 2022-05-26: Auto merge of #97434 - matthiaskrgr:rollup-7j3y16l, r=matthiaskrgr
  commit[1] 2022-05-26: Auto merge of #97386 - nnethercote:optimize-pos-adjustments, r=bjorn3
  commit[2] 2022-05-27: Auto merge of #96298 - petrochenkov:fromgen, r=estebank
  commit[3] 2022-05-27: Auto merge of #97444 - compiler-errors:rollup-2gvdav6, r=compiler-errors
  commit[4] 2022-05-27: Auto merge of #97004 - nnethercote:proc-macro-tweaks, r=eddyb
  commit[5] 2022-05-27: Auto merge of #97442 - hafeoz:master, r=GuillaumeGomez
  commit[6] 2022-05-27: Auto merge of #96046 - oli-obk:const_typeck, r=cjgillot
  commit[7] 2022-05-27: Auto merge of #96790 - lqd:update_jemalloc, r=Mark-Simulacrum
ERROR: no CI builds available between 490324f7b29d5f1a1e063a563045d790091ed639 and ebbcbfc236ced21d5e6a92269edb704692ff26b8 within last 167 days

[matthiaskrgr]

This regressed again in #120847 cc @oli-obk

[oli-obk]

Not a regression, this was always possible: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=75705348c1fa16884e7912bc00bf9f92