RPITIT ICE when impl's fn is missing a type parameter

[jruderman]

Found with a modified fuzz-rustc

Code

#![feature(return_position_impl_trait_in_trait)]
#[allow(incomplete_features)]

struct S;

trait Foo {
    fn bar<T>() -> impl Sized;
}

impl Foo for S {
    fn bar() -> impl Sized {}
}

fn main() {
    S::bar();
}

Error output

error[E0049]: method `bar` has 0 type parameters but its trait declaration has 1 type parameter

error: internal compiler error: compiler/rustc_middle/src/ty/subst.rs:726:9: type parameter `T/#1` (T/1) out of range when substituting, substs=[S]

Full output including backtrace

error[E0049]: method `bar` has 0 type parameters but its trait declaration has 1 type parameter
  --> ra.rs:11:11
   |
7  |     fn bar<T>() -> impl Sized;
   |            - expected 1 type parameter
...
11 |     fn bar() -> impl Sized {}
   |           ^ found 0 type parameters

error: internal compiler error: compiler/rustc_middle/src/ty/subst.rs:726:9: type parameter `T/#1` (T/1) out of range when substituting, substs=[S]

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/e75aab045fc476f176a58c408f6b06f0e275c6e1/compiler/rustc_errors/src/lib.rs:1551:9
stack backtrace:
   0:        0x102887f12 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h1b594e9bcc0c6898
   1:        0x1028e64ba - core::fmt::write::h7c6f83d024852aa9
   2:        0x102879fec - std::io::Write::write_fmt::h97d969d4aea1606d
   3:        0x102887cda - std::sys_common::backtrace::print::h562dadf6028256bf
   4:        0x10288b0b6 - std::panicking::default_hook::{{closure}}::hee367e24075678e4
   5:        0x10288ae07 - std::panicking::default_hook::hcce3553a0befadd1
   6:        0x111ee1f3d - rustc_driver[f93b8a3886cc8b65]::DEFAULT_HOOK::{closure#0}::{closure#0}
   7:        0x10288b8b5 - std::panicking::rust_panic_with_hook::h4f6feaafc55c56a2
   8:        0x1165ff4d7 - std[38dd6138ba148cb2]::panicking::begin_panic::<rustc_errors[ef89fc2f19a46f90]::ExplicitBug>::{closure#0}
   9:        0x1165febe9 - std[38dd6138ba148cb2]::sys_common::backtrace::__rust_end_short_backtrace::<std[38dd6138ba148cb2]::panicking::begin_panic<rustc_errors[ef89fc2f19a46f90]::ExplicitBug>::{closure#0}, !>
  10:        0x116caaa39 - std[38dd6138ba148cb2]::panicking::begin_panic::<rustc_errors[ef89fc2f19a46f90]::ExplicitBug>
  11:        0x1165f92c9 - std[38dd6138ba148cb2]::panic::panic_any::<rustc_errors[ef89fc2f19a46f90]::ExplicitBug>
  12:        0x1165f753d - <rustc_errors[ef89fc2f19a46f90]::HandlerInner>::bug::<&alloc[dd1f1a43ef059f04]::string::String>
  13:        0x1165f7007 - <rustc_errors[ef89fc2f19a46f90]::Handler>::bug::<&alloc[dd1f1a43ef059f04]::string::String>
  14:        0x116753872 - rustc_middle[85091bb6846d2e9a]::ty::context::tls::with_context_opt::<rustc_middle[85091bb6846d2e9a]::ty::context::tls::with_opt<rustc_middle[85091bb6846d2e9a]::util::bug::opt_span_bug_fmt<rustc_span[50ad8565b2f1bbfb]::span_encoding::Span>::{closure#0}, ()>::{closure#0}, ()>
  15:        0x1167547d1 - rustc_middle[85091bb6846d2e9a]::util::bug::opt_span_bug_fmt::<rustc_span[50ad8565b2f1bbfb]::span_encoding::Span>
  16:        0x116cac3ee - rustc_middle[85091bb6846d2e9a]::util::bug::bug_fmt
  17:        0x116cac198 - <rustc_middle[85091bb6846d2e9a]::ty::subst::SubstFolder>::type_param_out_of_range
  18:        0x116733709 - <rustc_middle[85091bb6846d2e9a]::ty::subst::SubstFolder as rustc_middle[85091bb6846d2e9a]::ty::fold::TypeFolder>::fold_ty
  19:        0x116751365 - <&rustc_middle[85091bb6846d2e9a]::ty::list::List<rustc_middle[85091bb6846d2e9a]::ty::subst::GenericArg> as rustc_middle[85091bb6846d2e9a]::ty::fold::TypeFoldable>::try_fold_with::<rustc_middle[85091bb6846d2e9a]::ty::subst::SubstFolder>
  20:        0x116627227 - <rustc_middle[85091bb6846d2e9a]::ty::Ty as rustc_middle[85091bb6846d2e9a]::ty::fold::TypeSuperFoldable>::super_fold_with::<rustc_middle[85091bb6846d2e9a]::ty::subst::SubstFolder>
  21:        0x11490dd7b - rustc_middle[85091bb6846d2e9a]::ty::util::fold_list::<rustc_middle[85091bb6846d2e9a]::ty::subst::SubstFolder, rustc_middle[85091bb6846d2e9a]::ty::Ty, <&rustc_middle[85091bb6846d2e9a]::ty::list::List<rustc_middle[85091bb6846d2e9a]::ty::Ty> as rustc_middle[85091bb6846d2e9a]::ty::fold::TypeFoldable>::try_fold_with<rustc_middle[85091bb6846d2e9a]::ty::subst::SubstFolder>::{closure#0}>
  22:        0x1149437cf - <rustc_middle[85091bb6846d2e9a]::ty::sty::Binder<rustc_middle[85091bb6846d2e9a]::ty::sty::FnSig> as rustc_middle[85091bb6846d2e9a]::ty::fold::TypeSuperFoldable>::super_fold_with::<rustc_middle[85091bb6846d2e9a]::ty::subst::SubstFolder>
  23:        0x114a0810e - rustc_hir_analysis[e85e3b9a54dc24a9]::check::compare_method::collect_trait_impl_trait_tys
  24:        0x1156ee435 - rustc_query_system[38b064a260926677]::query::plumbing::try_execute_query::<rustc_query_impl[fcf86a589ba14889]::plumbing::QueryCtxt, rustc_query_system[38b064a260926677]::query::caches::DefaultCache<rustc_span[50ad8565b2f1bbfb]::def_id::DefId, core[322641b34a183a]::result::Result<&std[38dd6138ba148cb2]::collections::hash::map::HashMap<rustc_span[50ad8565b2f1bbfb]::def_id::DefId, rustc_middle[85091bb6846d2e9a]::ty::Ty, core[322641b34a183a]::hash::BuildHasherDefault<rustc_hash[4b31e884d1fde7da]::FxHasher>>, rustc_errors[ef89fc2f19a46f90]::ErrorGuaranteed>>>
  25:        0x1157d8534 - rustc_query_system[38b064a260926677]::query::plumbing::get_query::<rustc_query_impl[fcf86a589ba14889]::queries::collect_trait_impl_trait_tys, rustc_query_impl[fcf86a589ba14889]::plumbing::QueryCtxt>
  26:        0x1166f0d57 - <rustc_middle[85091bb6846d2e9a]::ty::context::TyCtxt>::bound_trait_impl_trait_tys
  27:        0x11639afd9 - rustc_trait_selection[fbfc9000665c881]::traits::project::project
  28:        0x1163975f1 - rustc_trait_selection[fbfc9000665c881]::traits::project::opt_normalize_projection_type
  29:        0x116391d9e - rustc_trait_selection[fbfc9000665c881]::traits::project::normalize_projection_type
  30:        0x116390794 - <rustc_trait_selection[fbfc9000665c881]::traits::project::AssocTypeNormalizer as rustc_middle[85091bb6846d2e9a]::ty::fold::TypeFolder>::fold_ty
  31:        0x11481503b - rustc_middle[85091bb6846d2e9a]::ty::util::fold_list::<rustc_trait_selection[fbfc9000665c881]::traits::project::AssocTypeNormalizer, rustc_middle[85091bb6846d2e9a]::ty::Ty, <&rustc_middle[85091bb6846d2e9a]::ty::list::List<rustc_middle[85091bb6846d2e9a]::ty::Ty> as rustc_middle[85091bb6846d2e9a]::ty::fold::TypeFoldable>::try_fold_with<rustc_trait_selection[fbfc9000665c881]::traits::project::AssocTypeNormalizer>::{closure#0}>
  32:        0x1147e4c61 - <rustc_trait_selection[fbfc9000665c881]::traits::project::AssocTypeNormalizer>::fold::<rustc_middle[85091bb6846d2e9a]::ty::sty::FnSig>
  33:        0x1147eb22a - rustc_trait_selection[fbfc9000665c881]::traits::project::normalize::<rustc_middle[85091bb6846d2e9a]::ty::sty::FnSig>
  34:        0x1148730bc - <rustc_infer[f3d18b0d0d8e0a5e]::infer::InferCtxt as rustc_trait_selection[fbfc9000665c881]::infer::InferCtxtExt>::partially_normalize_associated_types_in::<rustc_middle[85091bb6846d2e9a]::ty::sty::FnSig>
  35:        0x11482b100 - <rustc_hir_typeck[bdb15a1f3923c127]::inherited::Inherited>::normalize_associated_types_in::<rustc_middle[85091bb6846d2e9a]::ty::sty::FnSig>
  36:        0x1146da936 - <rustc_hir_typeck[bdb15a1f3923c127]::fn_ctxt::FnCtxt>::confirm_builtin_call
  37:        0x1146d7994 - <rustc_hir_typeck[bdb15a1f3923c127]::fn_ctxt::FnCtxt>::check_call
  38:        0x114741c82 - <rustc_hir_typeck[bdb15a1f3923c127]::fn_ctxt::FnCtxt>::check_expr_kind
  39:        0x1146eb680 - <rustc_hir_typeck[bdb15a1f3923c127]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  40:        0x1147010c5 - <rustc_hir_typeck[bdb15a1f3923c127]::fn_ctxt::FnCtxt>::check_stmt
  41:        0x1147017ef - <rustc_hir_typeck[bdb15a1f3923c127]::fn_ctxt::FnCtxt>::check_block_with_expected
  42:        0x114742068 - <rustc_hir_typeck[bdb15a1f3923c127]::fn_ctxt::FnCtxt>::check_expr_kind
  43:        0x1146eb680 - <rustc_hir_typeck[bdb15a1f3923c127]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  44:        0x1146ec6ba - <rustc_hir_typeck[bdb15a1f3923c127]::fn_ctxt::FnCtxt>::check_return_expr
  45:        0x11482c608 - rustc_hir_typeck[bdb15a1f3923c127]::check::check_fn
  46:        0x1148293cd - <rustc_hir_typeck[bdb15a1f3923c127]::inherited::InheritedBuilder>::enter::<rustc_hir_typeck[bdb15a1f3923c127]::typeck_with_fallback<rustc_hir_typeck[bdb15a1f3923c127]::typeck::{closure#0}>::{closure#0}::{closure#1}, &rustc_middle[85091bb6846d2e9a]::ty::context::TypeckResults>
  47:        0x1147c2ffa - rustc_hir_typeck[bdb15a1f3923c127]::typeck
  48:        0x1156d5159 - rustc_query_system[38b064a260926677]::query::plumbing::try_execute_query::<rustc_query_impl[fcf86a589ba14889]::plumbing::QueryCtxt, rustc_query_system[38b064a260926677]::query::caches::DefaultCache<rustc_span[50ad8565b2f1bbfb]::def_id::LocalDefId, &rustc_middle[85091bb6846d2e9a]::ty::context::TypeckResults>>
  49:        0x1157dab8c - rustc_query_system[38b064a260926677]::query::plumbing::get_query::<rustc_query_impl[fcf86a589ba14889]::queries::typeck, rustc_query_impl[fcf86a589ba14889]::plumbing::QueryCtxt>
  50:        0x11485276c - std[38dd6138ba148cb2]::panicking::try::<(), core[322641b34a183a]::panic::unwind_safe::AssertUnwindSafe<rustc_data_structures[2eed7d44fa552923]::sync::par_for_each_in<&[rustc_span[50ad8565b2f1bbfb]::def_id::LocalDefId], <rustc_middle[85091bb6846d2e9a]::hir::map::Map>::par_body_owners<rustc_hir_typeck[bdb15a1f3923c127]::typeck_item_bodies::{closure#0}>::{closure#0}>::{closure#0}::{closure#0}>>
  51:        0x1148524a5 - rustc_data_structures[2eed7d44fa552923]::sync::par_for_each_in::<&[rustc_span[50ad8565b2f1bbfb]::def_id::LocalDefId], <rustc_middle[85091bb6846d2e9a]::hir::map::Map>::par_body_owners<rustc_hir_typeck[bdb15a1f3923c127]::typeck_item_bodies::{closure#0}>::{closure#0}>
  52:        0x1147c277d - rustc_hir_typeck[bdb15a1f3923c127]::typeck_item_bodies
  53:        0x11576edb9 - rustc_query_system[38b064a260926677]::query::plumbing::try_execute_query::<rustc_query_impl[fcf86a589ba14889]::plumbing::QueryCtxt, rustc_query_system[38b064a260926677]::query::caches::DefaultCache<(), ()>>
  54:        0x1157cf339 - rustc_query_system[38b064a260926677]::query::plumbing::get_query::<rustc_query_impl[fcf86a589ba14889]::queries::typeck_item_bodies, rustc_query_impl[fcf86a589ba14889]::plumbing::QueryCtxt>
  55:        0x11493b3f4 - <rustc_session[304ed9bc7c986c94]::session::Session>::time::<(), rustc_hir_analysis[e85e3b9a54dc24a9]::check_crate::{closure#7}>
  56:        0x114a5a5df - rustc_hir_analysis[e85e3b9a54dc24a9]::check_crate
  57:        0x111fa53ba - rustc_interface[bab52cec3fba6e57]::passes::analysis
  58:        0x115760b7c - rustc_query_system[38b064a260926677]::query::plumbing::try_execute_query::<rustc_query_impl[fcf86a589ba14889]::plumbing::QueryCtxt, rustc_query_system[38b064a260926677]::query::caches::DefaultCache<(), core[322641b34a183a]::result::Result<(), rustc_errors[ef89fc2f19a46f90]::ErrorGuaranteed>>>
  59:        0x1157daf39 - rustc_query_system[38b064a260926677]::query::plumbing::get_query::<rustc_query_impl[fcf86a589ba14889]::queries::analysis, rustc_query_impl[fcf86a589ba14889]::plumbing::QueryCtxt>
  60:        0x111e71416 - <rustc_interface[bab52cec3fba6e57]::passes::QueryContext>::enter::<rustc_driver[f93b8a3886cc8b65]::run_compiler::{closure#1}::{closure#2}::{closure#3}, core[322641b34a183a]::result::Result<(), rustc_errors[ef89fc2f19a46f90]::ErrorGuaranteed>>
  61:        0x111eb568d - rustc_span[50ad8565b2f1bbfb]::with_source_map::<core[322641b34a183a]::result::Result<(), rustc_errors[ef89fc2f19a46f90]::ErrorGuaranteed>, rustc_interface[bab52cec3fba6e57]::interface::run_compiler<core[322641b34a183a]::result::Result<(), rustc_errors[ef89fc2f19a46f90]::ErrorGuaranteed>, rustc_driver[f93b8a3886cc8b65]::run_compiler::{closure#1}>::{closure#0}::{closure#1}>
  62:        0x111ea55bc - <scoped_tls[5d80669e9829205e]::ScopedKey<rustc_span[50ad8565b2f1bbfb]::SessionGlobals>>::set::<rustc_interface[bab52cec3fba6e57]::interface::run_compiler<core[322641b34a183a]::result::Result<(), rustc_errors[ef89fc2f19a46f90]::ErrorGuaranteed>, rustc_driver[f93b8a3886cc8b65]::run_compiler::{closure#1}>::{closure#0}, core[322641b34a183a]::result::Result<(), rustc_errors[ef89fc2f19a46f90]::ErrorGuaranteed>>
  63:        0x111e7437a - std[38dd6138ba148cb2]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[bab52cec3fba6e57]::util::run_in_thread_pool_with_globals<rustc_interface[bab52cec3fba6e57]::interface::run_compiler<core[322641b34a183a]::result::Result<(), rustc_errors[ef89fc2f19a46f90]::ErrorGuaranteed>, rustc_driver[f93b8a3886cc8b65]::run_compiler::{closure#1}>::{closure#0}, core[322641b34a183a]::result::Result<(), rustc_errors[ef89fc2f19a46f90]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[322641b34a183a]::result::Result<(), rustc_errors[ef89fc2f19a46f90]::ErrorGuaranteed>>
  64:        0x111e5ab4b - <<std[38dd6138ba148cb2]::thread::Builder>::spawn_unchecked_<rustc_interface[bab52cec3fba6e57]::util::run_in_thread_pool_with_globals<rustc_interface[bab52cec3fba6e57]::interface::run_compiler<core[322641b34a183a]::result::Result<(), rustc_errors[ef89fc2f19a46f90]::ErrorGuaranteed>, rustc_driver[f93b8a3886cc8b65]::run_compiler::{closure#1}>::{closure#0}, core[322641b34a183a]::result::Result<(), rustc_errors[ef89fc2f19a46f90]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[322641b34a183a]::result::Result<(), rustc_errors[ef89fc2f19a46f90]::ErrorGuaranteed>>::{closure#1} as core[322641b34a183a]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  65:        0x102894967 - std::sys::unix::thread::Thread::new::thread_start::hae9a83a2ac729f3b
  66:     0x7ff80d84d4e1 - __pthread_start

note: 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: rustc 1.67.0-nightly (e75aab045 2022-11-09) running on x86_64-apple-darwin

query stack during panic:
#0 [collect_trait_impl_trait_tys] comparing an impl and trait method signature, inferring any hidden `impl Trait` types in the process
#1 [typeck] type-checking `main`
#2 [typeck_item_bodies] type-checking all item bodies
#3 [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 E0049`.

Not a regression

This ICEd in nightly-2022-09-10 when RPITIT was first introduced

Version

rustc 1.67.0-nightly (e75aab045 2022-11-09)
binary: rustc
commit-hash: e75aab045fc476f176a58c408f6b06f0e275c6e1
commit-date: 2022-11-09
host: x86_64-apple-darwin
release: 1.67.0-nightly
LLVM version: 15.0.4

@rustbot label +F-return_position_impl_trait_in_trait