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[ICE]: `None` in `self_ty.normalized.ty_adt_def()`

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C-bug F-checked_type_aliases I-ICE T-compiler WG-trait-system-refactor
Dominant language
Rust
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Description

snippet:

//@compile-flags: -Znext-solver=globally
#![feature(lazy_type_alias)]
struct Inv;
enum Foo<F: Fn()> {
    Bar,
    Var(F),
}
type Supertype = Foo<dyn Fn()>;

fn main() {
    let x: Inv = todo!();
    match x {
        Foo::Var(Supertype::Bar) => {}
        _ => {}
    }
}

Version information

rustc 1.95.0-nightly (1500f0f47 2026-02-22)
binary: rustc
commit-hash: 1500f0f47f5fe8ddcd6528f6c6c031b210b4eac5
commit-date: 2026-02-22
host: x86_64-unknown-linux-gnu
release: 1.95.0-nightly
LLVM version: 22.1.0

Possibly related line of code:
https://github.com/rust-lang/rust/blob/1500f0f47f5fe8ddcd6528f6c6c031b210b4eac5/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs#L976-L988

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Znext-solver=globally

Program output 

warning: the feature `lazy_type_alias` is incomplete and may not be safe to use and/or cause compiler crashes
 --> /tmp/icemaker_global_tempdir.XjHPTBIuznYH/rustc_testrunner_tmpdir_reporting.WcK5sUzG23U6/mvce.rs:1:12
  |
1 | #![feature(lazy_type_alias)]
  |            ^^^^^^^^^^^^^^^
  |
  = note: see issue #112792 <https://github.com/rust-lang/rust/issues/112792> for more information
  = note: `#[warn(incomplete_features)]` on by default

error[E0277]: the size for values of type `(dyn Fn() + 'static)` cannot be known at compilation time
 --> /tmp/icemaker_global_tempdir.XjHPTBIuznYH/rustc_testrunner_tmpdir_reporting.WcK5sUzG23U6/mvce.rs:7:1
  |
7 | type Supertype = Foo<dyn Fn()>;
  | ^^^^^^^^^^^^^^ doesn't have a size known at compile-time
  |
  = help: the trait `Sized` is not implemented for `(dyn Fn() + 'static)`
note: required by an implicit `Sized` bound in `Foo`
 --> /tmp/icemaker_global_tempdir.XjHPTBIuznYH/rustc_testrunner_tmpdir_reporting.WcK5sUzG23U6/mvce.rs:3:10
  |
3 | enum Foo<F: Fn()> {
  |          ^ required by the implicit `Sized` requirement on this type parameter in `Foo`
help: you could relax the implicit `Sized` bound on `F` if it were used through indirection like `&F` or `Box<F>`
 --> /tmp/icemaker_global_tempdir.XjHPTBIuznYH/rustc_testrunner_tmpdir_reporting.WcK5sUzG23U6/mvce.rs:3:10
  |
3 | enum Foo<F: Fn()> {
  |          ^ this could be changed to `F: ?Sized`...
4 |     Bar,
5 |     Var(F),
  |         - ...if indirection were used here: `Box<F>`

warning: unreachable expression
  --> /tmp/icemaker_global_tempdir.XjHPTBIuznYH/rustc_testrunner_tmpdir_reporting.WcK5sUzG23U6/mvce.rs:11:5
   |
10 |       let x: Inv = todo!();
   |                    ------- any code following this expression is unreachable
11 | /     match x {
12 | |         Foo::Var(Supertype::Bar) => {}
13 | |         _ => {}
14 | |     }
   | |_____^ unreachable expression
   |
   = note: `#[warn(unreachable_code)]` (part of `#[warn(unused)]`) on by default

error[E0308]: mismatched types
  --> /tmp/icemaker_global_tempdir.XjHPTBIuznYH/rustc_testrunner_tmpdir_reporting.WcK5sUzG23U6/mvce.rs:12:9
   |
11 |     match x {
   |           - this expression has type `Inv`
12 |         Foo::Var(Supertype::Bar) => {}
   |         ^^^^^^^^^^^^^^^^^^^^^^^^ expected `Inv`, found `Foo<_>`
   |
   = note: expected struct `Inv`
                found enum `Foo<_>`

error[E0277]: the size for values of type `(dyn Fn() + 'static)` cannot be known at compilation time
  --> /tmp/icemaker_global_tempdir.XjHPTBIuznYH/rustc_testrunner_tmpdir_reporting.WcK5sUzG23U6/mvce.rs:12:18
   |
12 |         Foo::Var(Supertype::Bar) => {}
   |                  ^^^^^^^^^^^^^^ doesn't have a size known at compile-time
   |
   = help: the trait `Sized` is not implemented for `(dyn Fn() + 'static)`
note: required by a bound in `Foo::Bar`
  --> /tmp/icemaker_global_tempdir.XjHPTBIuznYH/rustc_testrunner_tmpdir_reporting.WcK5sUzG23U6/mvce.rs:3:10
   |
 3 | enum Foo<F: Fn()> {
   |          ^ required by this bound in `Foo::Bar`
 4 |     Bar,
   |     --- required by a bound in this unit variant

error[E0277]: expected a `Fn()` closure, found `Foo<dyn Fn()>`
  --> /tmp/icemaker_global_tempdir.XjHPTBIuznYH/rustc_testrunner_tmpdir_reporting.WcK5sUzG23U6/mvce.rs:12:9
   |
12 |         Foo::Var(Supertype::Bar) => {}
   |         ^^^^^^^^^^^^^^^^^^^^^^^^ expected an `Fn()` closure, found `Foo<dyn Fn()>`
   |
help: the trait `Fn()` is not implemented for `Foo<dyn Fn()>`
  --> /tmp/icemaker_global_tempdir.XjHPTBIuznYH/rustc_testrunner_tmpdir_reporting.WcK5sUzG23U6/mvce.rs:3:1
   |
 3 | enum Foo<F: Fn()> {
   | ^^^^^^^^^^^^^^^^^
   = note: wrap the `Foo<dyn Fn()>` in a closure with no arguments: `|| { /* code */ }`
note: required by a bound in `Foo::Var`
  --> /tmp/icemaker_global_tempdir.XjHPTBIuznYH/rustc_testrunner_tmpdir_reporting.WcK5sUzG23U6/mvce.rs:3:13
   |
 3 | enum Foo<F: Fn()> {
   |             ^^^^ required by this bound in `Foo::Var`
 4 |     Bar,
 5 |     Var(F),
   |     --- required by a bound in this tuple variant


thread 'rustc' (163240) panicked at /rustc-dev/1500f0f47f5fe8ddcd6528f6c6c031b210b4eac5/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs:982:63:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0:     0x7fd377fb80eb - <<std[8fa6c4d7877d9fa6]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[8d2c922a005dfed9]::fmt::Display>::fmt
   1:     0x7fd378621648 - core[8d2c922a005dfed9]::fmt::write
   2:     0x7fd377fcf0f6 - <std[8fa6c4d7877d9fa6]::sys::stdio::unix::Stderr as std[8fa6c4d7877d9fa6]::io::Write>::write_fmt
   3:     0x7fd377f8e1d8 - std[8fa6c4d7877d9fa6]::panicking::default_hook::{closure#0}
   4:     0x7fd377fab553 - std[8fa6c4d7877d9fa6]::panicking::default_hook
   5:     0x7fd376f84080 - std[8fa6c4d7877d9fa6]::panicking::update_hook::<alloc[e536beed0316d181]::boxed::Box<rustc_driver_impl[f1389595c05d78d8]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7fd377fab832 - std[8fa6c4d7877d9fa6]::panicking::panic_with_hook
   7:     0x7fd377f8e2ca - std[8fa6c4d7877d9fa6]::panicking::panic_handler::{closure#0}
   8:     0x7fd377f84fe9 - std[8fa6c4d7877d9fa6]::sys::backtrace::__rust_end_short_backtrace::<std[8fa6c4d7877d9fa6]::panicking::panic_handler::{closure#0}, !>
   9:     0x7fd377f8fcfd - __rustc[d7af78fd024a5d6e]::rust_begin_unwind
  10:     0x7fd3753ed78c - core[8d2c922a005dfed9]::panicking::panic_fmt
  11:     0x7fd374642312 - core[8d2c922a005dfed9]::panicking::panic
  12:     0x7fd374f373c9 - core[8d2c922a005dfed9]::option::unwrap_failed
  13:     0x7fd3792d7163 - <rustc_hir_typeck[aadce8c622caaa3b]::fn_ctxt::FnCtxt>::instantiate_value_path
  14:     0x7fd378a37216 - <rustc_hir_typeck[aadce8c622caaa3b]::fn_ctxt::FnCtxt>::check_pat
  15:     0x7fd378a3aefa - <rustc_hir_typeck[aadce8c622caaa3b]::fn_ctxt::FnCtxt>::check_pat_inner
  16:     0x7fd378a36b13 - <rustc_hir_typeck[aadce8c622caaa3b]::fn_ctxt::FnCtxt>::check_pat
  17:     0x7fd378a32f6a - <rustc_hir_typeck[aadce8c622caaa3b]::fn_ctxt::FnCtxt>::check_expr_match
  18:     0x7fd378a5ac7b - <rustc_hir_typeck[aadce8c622caaa3b]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  19:     0x7fd378a53a70 - <rustc_hir_typeck[aadce8c622caaa3b]::fn_ctxt::FnCtxt>::check_expr_block
  20:     0x7fd378a59817 - <rustc_hir_typeck[aadce8c622caaa3b]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  21:     0x7fd378a28610 - rustc_hir_typeck[aadce8c622caaa3b]::check::check_fn
  22:     0x7fd3793f1332 - rustc_hir_typeck[aadce8c622caaa3b]::typeck_with_inspect::{closure#0}
  23:     0x7fd3793efd72 - rustc_query_impl[cec139e1f3385ac4]::query_impl::typeck::invoke_provider_fn::__rust_begin_short_backtrace
  24:     0x7fd378db853e - rustc_query_impl[cec139e1f3385ac4]::execution::try_execute_query::<rustc_data_structures[1a0237db0a3cda6a]::vec_cache::VecCache<rustc_span[8a11d63785993c5a]::def_id::LocalDefId, rustc_middle[60c2cf3af82b0a08]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[60c2cf3af82b0a08]::dep_graph::graph::DepNodeIndex>, {rustc_query_impl[cec139e1f3385ac4]::QueryFlags { is_anon: false, is_depth_limit: false, is_feedable: false }}, false>
  25:     0x7fd378db8109 - rustc_query_impl[cec139e1f3385ac4]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  26:     0x7fd378db1b4e - <rustc_middle[60c2cf3af82b0a08]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_hir_analysis[a8016fad3afadedb]::check_crate::{closure#2}>::{closure#0}
  27:     0x7fd378db156e - rustc_hir_analysis[a8016fad3afadedb]::check_crate
  28:     0x7fd378db50ac - rustc_interface[b6ce98af9df5606d]::passes::analysis
  29:     0x7fd3797e1499 - rustc_query_impl[cec139e1f3385ac4]::execution::try_execute_query::<rustc_middle[60c2cf3af82b0a08]::query::caches::SingleCache<rustc_middle[60c2cf3af82b0a08]::query::erase::ErasedData<[u8; 0usize]>>, {rustc_query_impl[cec139e1f3385ac4]::QueryFlags { is_anon: false, is_depth_limit: false, is_feedable: false }}, false>
  30:     0x7fd3797e10c8 - rustc_query_impl[cec139e1f3385ac4]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  31:     0x7fd37982088b - rustc_interface[b6ce98af9df5606d]::interface::run_compiler::<(), rustc_driver_impl[f1389595c05d78d8]::run_compiler::{closure#0}>::{closure#1}
  32:     0x7fd3797d09fe - std[8fa6c4d7877d9fa6]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[b6ce98af9df5606d]::util::run_in_thread_with_globals<rustc_interface[b6ce98af9df5606d]::util::run_in_thread_pool_with_globals<rustc_interface[b6ce98af9df5606d]::interface::run_compiler<(), rustc_driver_impl[f1389595c05d78d8]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  33:     0x7fd3797d10e0 - <std[8fa6c4d7877d9fa6]::thread::lifecycle::spawn_unchecked<rustc_interface[b6ce98af9df5606d]::util::run_in_thread_with_globals<rustc_interface[b6ce98af9df5606d]::util::run_in_thread_pool_with_globals<rustc_interface[b6ce98af9df5606d]::interface::run_compiler<(), rustc_driver_impl[f1389595c05d78d8]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[8d2c922a005dfed9]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  34:     0x7fd3797d1f6c - <std[8fa6c4d7877d9fa6]::sys::thread::unix::Thread>::new::thread_start
  35:     0x7fd3732a598b - <unknown>
  36:     0x7fd373329a0c - <unknown>
  37:                0x0 - <unknown>

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 make sure that you have updated to the latest nightly

note: rustc 1.95.0-nightly (1500f0f47 2026-02-22) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z next-solver=globally -Z dump-mir-dir=dir

query stack during panic:
#0 [typeck] type-checking `main`
#1 [analysis] running analysis passes on crate `mvce`
end of query stack
error: aborting due to 4 previous errors; 2 warnings emitted

Some errors have detailed explanations: E0277, E0308.
For more information about an error, try `rustc --explain E0277`.

@rustbot label +F-lazy_type_alias +WG-trait-system-refactor

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the ICE with the supplied a.rs snippet and -Znext-solver=globally. Start at compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs:976-988, especially FnCtxt::instantiate_value_path, and trace the failing pattern type-checking path shown in the stack trace. Done means the example reports its existing type errors without rustc panicking.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
45/100

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