ICE: Shouldn't expect a placeholder type in implied bounds (yet) When return type in trait impl is `&impl Trait`

[nikvoid]

Code

pub fn main() {

}

pub trait Iced {
    fn get(&self) -> &impl Sized;
}

/// Impl causes ICE
impl Iced for () {
    fn get(&self) -> &impl Sized { &() }
} 

Meta

rustc --version --verbose:

rustc 1.76.0-nightly (37b2813a7 2023-11-24)
binary: rustc
commit-hash: 37b2813a7be580ef59048a6bd08444c79e5cc97f
commit-date: 2023-11-24
host: x86_64-pc-windows-msvc
release: 1.76.0-nightly
LLVM version: 17.0.5

Error output

thread 'rustc' panicked at compiler\rustc_trait_selection\src\traits\query\type_op\implied_outlives_bounds.rs:211:21:
not implemented: Shouldn't expect a placeholder type in implied bounds (yet)
stack backtrace:
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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 `E:\projects\rust-test\rustc-ice-2023-11-25T15_24_27-2620.txt` to your bug report

note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED] -C target-cpu=native

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [implied_outlives_bounds] computing implied outlives bounds for `&^1`
#1 [collect_return_position_impl_trait_in_trait_tys] comparing an impl and trait method signature, inferring any hidden `impl Trait` types in the process
#2 [type_of] computing type of `<impl at src\bin\ice.rs:10:1: 10:17>::{opaque#0}`
#3 [check_mod_impl_wf] checking that impls are well-formed in top-level module
#4 [analysis] running analysis passes on this crate
end of query stack

Backtrace

thread 'rustc' panicked at compiler\rustc_trait_selection\src\traits\query\type_op\implied_outlives_bounds.rs:211:21:
not implemented: Shouldn't expect a placeholder type in implied bounds (yet)
stack backtrace:
   0:     0x7ffa1a14ddff - std::backtrace::Backtrace::force_capture::h3f668b79418f22f9
   1:     0x7ffa1a14dd64 - std::backtrace::Backtrace::force_capture::h3f668b79418f22f9
   2:     0x7ffa102f5949 - <tracing_subscriber[c47e476d72039508]::util::TryInitError as core[5caf4f20ff5a4def]::fmt::Display>::fmt
   3:     0x7ffa1a166903 - std::panicking::rust_panic_with_hook::h81a622fcd9e6c3bd
   4:     0x7ffa1a16676b - <std::panicking::begin_panic_handler::StaticStrPayload as core::panic::PanicPayload>::take_box::heaf78657578f08f1
   5:     0x7ffa1a163949 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h455546a8643c8c2e
   6:     0x7ffa1a1664b4 - rust_begin_unwind
   7:     0x7ffa1a1bb1e7 - core::panicking::panic_fmt::ha0f2e731394baff3
   8:     0x7ffa0fde00af - rustc_trait_selection[e2e03292c3acd521]::traits::normalize_param_env_or_error
   9:     0x7ffa0fe253da - <rustc_infer[295366c5eee344e]::traits::project::ProjectionCacheKey as rustc_trait_selection[e2e03292c3acd521]::traits::project::ProjectionCacheKeyExt>::from_poly_projection_predicate
  10:     0x7ffa0fde435c - rustc_trait_selection[e2e03292c3acd521]::traits::query::type_op::implied_outlives_bounds::compute_implied_outlives_bounds_inner
  11:     0x7ffa0fb26a44 - rustc_traits[f20ef36d848666e1]::type_op::type_op_prove_predicate
  12:     0x7ffa0fb17557 - rustc_traits[f20ef36d848666e1]::implied_outlives_bounds::implied_outlives_bounds
  13:     0x7ffa0fb64493 - <rustc_query_impl[c8293b5f85111528]::plumbing::QueryCtxt as rustc_query_system[cef96664c9ada928]::query::QueryContext>::load_side_effects
  14:     0x7ffa0fb9f2ed - <rustc_query_impl[c8293b5f85111528]::plumbing::QueryCtxt as rustc_query_system[cef96664c9ada928]::query::QueryContext>::load_side_effects
  15:     0x7ffa0eea03e2 - <dyn std[6105eaff722720a9]::io::Write as nu_ansi_term[58d86d1c798192ea]::write::AnyWrite>::write_str
  16:     0x7ffa0fdfdd4b - <rustc_infer[295366c5eee344e]::infer::InferCtxt as rustc_trait_selection[e2e03292c3acd521]::traits::outlives_bounds::InferCtxtExt>::implied_outlives_bounds
  17:     0x7ffa0f5104e3 - <rustc_hir_analysis[28b5b319a1019660]::autoderef::Autoderef>::into_obligations
  18:     0x7ffa1072ad6c - rustc_hir_analysis[28b5b319a1019660]::check::compare_impl_item::collect_return_position_impl_trait_in_trait_tys
  19:     0x7ffa10e45d37 - <rustc_query_impl[c8293b5f85111528]::plumbing::QueryCtxt as rustc_query_system[cef96664c9ada928]::query::QueryContext>::depth_limit_error
  20:     0x7ffa10e9deb3 - <rustc_query_impl[c8293b5f85111528]::plumbing::QueryCtxt as rustc_query_system[cef96664c9ada928]::query::QueryContext>::depth_limit_error
  21:     0x7ffa0fbdb257 - <rustc_query_impl[c8293b5f85111528]::plumbing::QueryCtxt as rustc_query_system[cef96664c9ada928]::query::QueryContext>::load_side_effects
  22:     0x7ffa10e28301 - <rustc_span[bb17ac722f92f365]::def_id::LocalDefId as rustc_query_impl[c8293b5f85111528]::profiling_support::SpecIntoSelfProfilingString>::spec_to_self_profile_string
  23:     0x7ffa0f4ea4eb - <rustc_hir_analysis[28b5b319a1019660]::collect::resolve_bound_vars::BoundVarContext as rustc_hir[6c53a7437ef4457d]::intravisit::Visitor>::visit_lifetime
  24:     0x7ffa0f4f416c - rustc_hir_analysis[28b5b319a1019660]::collect::type_of::type_of
  25:     0x7ffa0fb6494b - <rustc_query_impl[c8293b5f85111528]::plumbing::QueryCtxt as rustc_query_system[cef96664c9ada928]::query::QueryContext>::load_side_effects
  26:     0x7ffa0fb7b6c1 - <rustc_query_impl[c8293b5f85111528]::plumbing::QueryCtxt as rustc_query_system[cef96664c9ada928]::query::QueryContext>::load_side_effects
  27:     0x7ffa0fbdb257 - <rustc_query_impl[c8293b5f85111528]::plumbing::QueryCtxt as rustc_query_system[cef96664c9ada928]::query::QueryContext>::load_side_effects
  28:     0x7ffa0fb59848 - rustc_query_impl[c8293b5f85111528]::query_callbacks
  29:     0x7ffa0f54353c - rustc_hir_analysis[28b5b319a1019660]::check::wfcheck::check_well_formed
  30:     0x7ffa0f543a93 - rustc_hir_analysis[28b5b319a1019660]::check::wfcheck::check_well_formed
  31:     0x7ffa0f51f039 - rustc_hir_analysis[28b5b319a1019660]::check::wfcheck::check_well_formed
  32:     0x7ffa0ede954f - rustc_query_impl[c8293b5f85111528]::profiling_support::alloc_self_profile_query_strings
  33:     0x7ffa0edcc76f - rustc_query_impl[c8293b5f85111528]::dynamic_queries
  34:     0x7ffa0edef001 - rustc_query_impl[c8293b5f85111528]::profiling_support::alloc_self_profile_query_strings
  35:     0x7ffa0ee3d7d3 - rustc_query_impl[c8293b5f85111528]::profiling_support::alloc_self_profile_query_strings
  36:     0x7ffa0eec339c - <dyn std[6105eaff722720a9]::io::Write as nu_ansi_term[58d86d1c798192ea]::write::AnyWrite>::write_str
  37:     0x7ffa0f4a38f3 - rustc_hir_analysis[28b5b319a1019660]::check_crate
  38:     0x7ffa0f27427d - rustc_interface[141774b3faf88461]::passes::analysis
  39:     0x7ffa0edeba2d - rustc_query_impl[c8293b5f85111528]::profiling_support::alloc_self_profile_query_strings
  40:     0x7ffa0eece209 - <dyn std[6105eaff722720a9]::io::Write as nu_ansi_term[58d86d1c798192ea]::write::AnyWrite>::write_str
  41:     0x7ffa0edeec3c - rustc_query_impl[c8293b5f85111528]::profiling_support::alloc_self_profile_query_strings
  42:     0x7ffa0ee14577 - rustc_query_impl[c8293b5f85111528]::profiling_support::alloc_self_profile_query_strings
  43:     0x7ffa0eea9d47 - <dyn std[6105eaff722720a9]::io::Write as nu_ansi_term[58d86d1c798192ea]::write::AnyWrite>::write_str
  44:     0x7ffa0c2f999d - rustc_driver_impl[7d4818c60294d5bb]::main
  45:     0x7ffa0c30c064 - <rustc_middle[903a3d62136ee3d2]::ty::SymbolName as core[5caf4f20ff5a4def]::fmt::Debug>::fmt
  46:     0x7ffa0c300b33 - <rustc_middle[903a3d62136ee3d2]::ty::SymbolName as core[5caf4f20ff5a4def]::fmt::Debug>::fmt
  47:     0x7ffa0c30865c - <rustc_middle[903a3d62136ee3d2]::ty::SymbolName as core[5caf4f20ff5a4def]::fmt::Debug>::fmt
  48:     0x7ffa0c301661 - <rustc_middle[903a3d62136ee3d2]::ty::SymbolName as core[5caf4f20ff5a4def]::fmt::Debug>::fmt
  49:     0x7ffa0c30ae5f - <rustc_middle[903a3d62136ee3d2]::ty::SymbolName as core[5caf4f20ff5a4def]::fmt::Debug>::fmt
  50:     0x7ffa0c30af78 - <rustc_middle[903a3d62136ee3d2]::ty::SymbolName as core[5caf4f20ff5a4def]::fmt::Debug>::fmt
  51:     0x7ffa1a178a7c - std::sys::windows::thread::Thread::new::h28d06cd1c8f6e0e9
  52:     0x7ffa75d926ad - BaseThreadInitThunk
  53:     0x7ffa7754aa68 - RtlUserThreadStart


rustc version: 1.76.0-nightly (37b2813a7 2023-11-24)
platform: x86_64-pc-windows-msvc

query stack during panic:
#0 [implied_outlives_bounds] computing implied outlives bounds for `&^1`
#1 [collect_return_position_impl_trait_in_trait_tys] comparing an impl and trait method signature, inferring any hidden `impl Trait` types in the process
#2 [type_of] computing type of `<impl at src\bin\ice.rs:10:1: 10:17>::{opaque#0}`
#3 [check_mod_impl_wf] checking that impls are well-formed in top-level module
#4 [analysis] running analysis passes on this crate
end of query stack

[matthiaskrgr]

Regression in nightly-2023-11-21
Regression in #118082
Regression in #118000 ping @compiler-errors

[compiler-errors]

Shouldn't expect a placeholder type in implied bounds

Except for where I made an implied bounds explicitly take placeholders 🤦

I'll fix this, sorry!