ICE: `layout errored yet tail '{type error}' is not a type parameter or a projection`

[matthiaskrgr]

auto-reduced (treereduce-rust):

trait Trait {
    type RefTarget;
}

impl Trait for () {}

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

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

original:

trait Trait {
    type RefTarget;
}

impl Trait for () where S<{}>: {}

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

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

Version information

rustc 1.79.0-nightly (1dea922ea 2024-04-16)
binary: rustc
commit-hash: 1dea922ea6e74f99a0e97de5cdb8174e4dea0444
commit-date: 2024-04-16
host: x86_64-unknown-linux-gnu
release: 1.79.0-nightly
LLVM version: 18.1.3

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc

Program output

error[E0046]: not all trait items implemented, missing: `RefTarget`
 --> /tmp/icemaker_global_tempdir.pZhDC78qbnNh/rustc_testrunner_tmpdir_reporting.yD8R6X6DQSXY/mvce.rs:5:1
  |
2 |     type RefTarget;
  |     -------------- `RefTarget` from trait
...
5 | impl Trait for () {}
  | ^^^^^^^^^^^^^^^^^ missing `RefTarget` in implementation

error: internal compiler error: compiler/rustc_middle/src/ty/layout.rs:339:26: SizeSkeleton::compute(&Other): layout errored (Unknown(Alias(Projection, AliasTy { args: [Other], def_id: DefId(2:2049 ~ core[a6f4]::ptr::metadata::Pointee::Metadata) }))), yet tail `{type error}` is not a type parameter or a projection

thread 'rustc' panicked at compiler/rustc_middle/src/ty/layout.rs:339:26:
Box<dyn Any>
stack backtrace:
   0:     0x7ddcbbec1cd5 - std::backtrace_rs::backtrace::libunwind::trace::h4570894ec6e934bd
                               at /rustc/1dea922ea6e74f99a0e97de5cdb8174e4dea0444/library/std/src/../../backtrace/src/backtrace/libunwind.rs:105:5
   1:     0x7ddcbbec1cd5 - std::backtrace_rs::backtrace::trace_unsynchronized::h8e38265835f5092c
                               at /rustc/1dea922ea6e74f99a0e97de5cdb8174e4dea0444/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7ddcbbec1cd5 - std::sys_common::backtrace::_print_fmt::hcc100545c13c51ae
                               at /rustc/1dea922ea6e74f99a0e97de5cdb8174e4dea0444/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x7ddcbbec1cd5 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h63aa418d14a98965
                               at /rustc/1dea922ea6e74f99a0e97de5cdb8174e4dea0444/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7ddcbbf10f9b - core::fmt::rt::Argument::fmt::h0e4984b8632d694b
                               at /rustc/1dea922ea6e74f99a0e97de5cdb8174e4dea0444/library/core/src/fmt/rt.rs:165:63
   5:     0x7ddcbbf10f9b - core::fmt::write::h666dcbeea4b0bb0e
                               at /rustc/1dea922ea6e74f99a0e97de5cdb8174e4dea0444/library/core/src/fmt/mod.rs:1157:21
   6:     0x7ddcbbeb68df - std::io::Write::write_fmt::h28d16f793a75f183
                               at /rustc/1dea922ea6e74f99a0e97de5cdb8174e4dea0444/library/std/src/io/mod.rs:1832:15
   7:     0x7ddcbbec1aae - std::sys_common::backtrace::_print::he08fa3b3df648c57
                               at /rustc/1dea922ea6e74f99a0e97de5cdb8174e4dea0444/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7ddcbbec1aae - std::sys_common::backtrace::print::hbc1c6a549ba18d53
                               at /rustc/1dea922ea6e74f99a0e97de5cdb8174e4dea0444/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7ddcbbec4429 - std::panicking::default_hook::{{closure}}::h452c80da7053da38
  10:     0x7ddcbbec416d - std::panicking::default_hook::hed123a5761019ac1
                               at /rustc/1dea922ea6e74f99a0e97de5cdb8174e4dea0444/library/std/src/panicking.rs:291:9
  11:     0x7ddcb8887a2b - std[2ce6f5251f47c1eb]::panicking::update_hook::<alloc[b271cfb3f3240113]::boxed::Box<rustc_driver_impl[41cead0f6bccae97]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x7ddcbbec4b2c - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h1ebfc40cd82c2169
                               at /rustc/1dea922ea6e74f99a0e97de5cdb8174e4dea0444/library/alloc/src/boxed.rs:2032:9
  13:     0x7ddcbbec4b2c - std::panicking::rust_panic_with_hook::hcdf9ea59f53f1733
                               at /rustc/1dea922ea6e74f99a0e97de5cdb8174e4dea0444/library/std/src/panicking.rs:792:13
  14:     0x7ddcb88b7fa4 - std[2ce6f5251f47c1eb]::panicking::begin_panic::<rustc_errors[a3deda365ad118db]::ExplicitBug>::{closure#0}
  15:     0x7ddcb88b4956 - std[2ce6f5251f47c1eb]::sys_common::backtrace::__rust_end_short_backtrace::<std[2ce6f5251f47c1eb]::panicking::begin_panic<rustc_errors[a3deda365ad118db]::ExplicitBug>::{closure#0}, !>
  16:     0x7ddcb88afee6 - std[2ce6f5251f47c1eb]::panicking::begin_panic::<rustc_errors[a3deda365ad118db]::ExplicitBug>
  17:     0x7ddcb88c0fd1 - <rustc_errors[a3deda365ad118db]::diagnostic::BugAbort as rustc_errors[a3deda365ad118db]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  18:     0x7ddcb8d6996c - rustc_middle[1c73b0b9b5d630bc]::util::bug::opt_span_bug_fmt::<rustc_span[5eb068f1d282c6c3]::span_encoding::Span>::{closure#0}
  19:     0x7ddcb8d50eba - rustc_middle[1c73b0b9b5d630bc]::ty::context::tls::with_opt::<rustc_middle[1c73b0b9b5d630bc]::util::bug::opt_span_bug_fmt<rustc_span[5eb068f1d282c6c3]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  20:     0x7ddcb8d50d5b - rustc_middle[1c73b0b9b5d630bc]::ty::context::tls::with_context_opt::<rustc_middle[1c73b0b9b5d630bc]::ty::context::tls::with_opt<rustc_middle[1c73b0b9b5d630bc]::util::bug::opt_span_bug_fmt<rustc_span[5eb068f1d282c6c3]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  21:     0x7ddcb6950ab0 - rustc_middle[1c73b0b9b5d630bc]::util::bug::bug_fmt
  22:     0x7ddcbb3980df - <rustc_middle[1c73b0b9b5d630bc]::ty::layout::SizeSkeleton>::compute.cold
  23:     0x7ddcb8d3cdf5 - <rustc_middle[1c73b0b9b5d630bc]::ty::layout::SizeSkeleton>::compute::{closure#1}
  24:     0x7ddcbb398416 - <rustc_middle[1c73b0b9b5d630bc]::ty::layout::SizeSkeleton>::compute.cold
  25:     0x7ddcba849d01 - <rustc_hir_typeck[3f614bc6655f91fa]::fn_ctxt::FnCtxt>::check_transmute
  26:     0x7ddcb9e53ec9 - rustc_hir_typeck[3f614bc6655f91fa]::typeck
  27:     0x7ddcb9e51c89 - rustc_query_impl[5bd0ae940d929779]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[5bd0ae940d929779]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[1c73b0b9b5d630bc]::query::erase::Erased<[u8; 8usize]>>
  28:     0x7ddcb9e3e271 - rustc_query_system[7ae2b61b6d9bea48]::query::plumbing::try_execute_query::<rustc_query_impl[5bd0ae940d929779]::DynamicConfig<rustc_query_system[7ae2b61b6d9bea48]::query::caches::VecCache<rustc_span[5eb068f1d282c6c3]::def_id::LocalDefId, rustc_middle[1c73b0b9b5d630bc]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[5bd0ae940d929779]::plumbing::QueryCtxt, false>
  29:     0x7ddcb9e3cb8c - rustc_query_impl[5bd0ae940d929779]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  30:     0x7ddcb9e3c758 - <rustc_middle[1c73b0b9b5d630bc]::hir::map::Map>::par_body_owners::<rustc_hir_analysis[55b246c3f202a5fd]::check_crate::{closure#4}>::{closure#0}
  31:     0x7ddcb9e3b441 - rustc_hir_analysis[55b246c3f202a5fd]::check_crate
  32:     0x7ddcba42307a - rustc_interface[e8e8772a2baf35df]::passes::analysis
  33:     0x7ddcba422bd5 - rustc_query_impl[5bd0ae940d929779]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[5bd0ae940d929779]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[1c73b0b9b5d630bc]::query::erase::Erased<[u8; 1usize]>>
  34:     0x7ddcba9a2a65 - rustc_query_system[7ae2b61b6d9bea48]::query::plumbing::try_execute_query::<rustc_query_impl[5bd0ae940d929779]::DynamicConfig<rustc_query_system[7ae2b61b6d9bea48]::query::caches::SingleCache<rustc_middle[1c73b0b9b5d630bc]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[5bd0ae940d929779]::plumbing::QueryCtxt, false>
  35:     0x7ddcba9a27c9 - rustc_query_impl[5bd0ae940d929779]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  36:     0x7ddcba890614 - rustc_interface[e8e8772a2baf35df]::interface::run_compiler::<core[a6f449f0b0283003]::result::Result<(), rustc_span[5eb068f1d282c6c3]::ErrorGuaranteed>, rustc_driver_impl[41cead0f6bccae97]::run_compiler::{closure#0}>::{closure#0}
  37:     0x7ddcba95e200 - std[2ce6f5251f47c1eb]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[e8e8772a2baf35df]::util::run_in_thread_with_globals<rustc_interface[e8e8772a2baf35df]::util::run_in_thread_pool_with_globals<rustc_interface[e8e8772a2baf35df]::interface::run_compiler<core[a6f449f0b0283003]::result::Result<(), rustc_span[5eb068f1d282c6c3]::ErrorGuaranteed>, rustc_driver_impl[41cead0f6bccae97]::run_compiler::{closure#0}>::{closure#0}, core[a6f449f0b0283003]::result::Result<(), rustc_span[5eb068f1d282c6c3]::ErrorGuaranteed>>::{closure#0}, core[a6f449f0b0283003]::result::Result<(), rustc_span[5eb068f1d282c6c3]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[a6f449f0b0283003]::result::Result<(), rustc_span[5eb068f1d282c6c3]::ErrorGuaranteed>>
  38:     0x7ddcba95e006 - <<std[2ce6f5251f47c1eb]::thread::Builder>::spawn_unchecked_<rustc_interface[e8e8772a2baf35df]::util::run_in_thread_with_globals<rustc_interface[e8e8772a2baf35df]::util::run_in_thread_pool_with_globals<rustc_interface[e8e8772a2baf35df]::interface::run_compiler<core[a6f449f0b0283003]::result::Result<(), rustc_span[5eb068f1d282c6c3]::ErrorGuaranteed>, rustc_driver_impl[41cead0f6bccae97]::run_compiler::{closure#0}>::{closure#0}, core[a6f449f0b0283003]::result::Result<(), rustc_span[5eb068f1d282c6c3]::ErrorGuaranteed>>::{closure#0}, core[a6f449f0b0283003]::result::Result<(), rustc_span[5eb068f1d282c6c3]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[a6f449f0b0283003]::result::Result<(), rustc_span[5eb068f1d282c6c3]::ErrorGuaranteed>>::{closure#2} as core[a6f449f0b0283003]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  39:     0x7ddcbbecea1b - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hcc8d2a2ce029e331
                               at /rustc/1dea922ea6e74f99a0e97de5cdb8174e4dea0444/library/alloc/src/boxed.rs:2018:9
  40:     0x7ddcbbecea1b - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h23d36ed0db50e565
                               at /rustc/1dea922ea6e74f99a0e97de5cdb8174e4dea0444/library/alloc/src/boxed.rs:2018:9
  41:     0x7ddcbbecea1b - std::sys::pal::unix::thread::Thread::new::thread_start::h6f03de8fdd6d8209
                               at /rustc/1dea922ea6e74f99a0e97de5cdb8174e4dea0444/library/std/src/sys/pal/unix/thread.rs:108:17
  42:     0x7ddcb56a955a - <unknown>
  43:     0x7ddcb5726a3c - <unknown>
  44:                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: please make sure that you have updated to the latest nightly

note: rustc 1.79.0-nightly (1dea922ea 2024-04-16) running on x86_64-unknown-linux-gnu

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

For more information about this error, try `rustc --explain E0046`.

[compiler-errors]

is not a type parameter or a projection

that's true, it's a type error

(should be a quick fix)

[matthiaskrgr]

you may also enjoy this gem:
error: internal compiler error: compiler/rustc_infer/src/infer/at.rs:400:21: relating different kinds: {const error}: {type error} KeyNil
(found somewhere else)

[matthiaskrgr]

Ah, this ( #123031 ) one bisects to #123491 fyi @gurry ^^

[gurry]

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