ICE: OpaqueCast unexpected because it isn't captured in rustc_middle/src/ty/closure.rs

Code

(hand-reduced)

#![warn(rust_2021_compatibility)]

trait Static<'a> {}

struct Foo((u32, u32));

fn main() {
    type T = impl Static;
    let foo: T = Foo((1u32, 2u32));
    let x = move || {
        let Foo((a, b)) = foo;
    };
}

I'm not sure whether it is okay to report ICE which requires #![warn(rust_2021_compatibility)] attribute.

(original, ~100 lines)

//@ edition:2018
//@ revisions: rpass1


// Regression test for #86753. The `type_implements_trait` query (since moved to a method)
// was encountering an ICE during incremental testing when hashing its arguments.
#![warn(rust_2021_compatibility)]

use std::future::Future;
use std::pin::Pin;
use std::task::{Poll, Context};

struct LocalSet {}
struct RunUntil<'a, F> {
    _local_set: &'a LocalSet,
    _future: F,
}
impl<'a, F> RunUntil<'a, F> {
    fn project<'pin>(self: Pin<&'pin mut Self>) -> Projection<'pin, 'a, F> {
        unimplemented!()
    }
}

struct Projection<'pin, 'a, F>
where
    RunUntil<'a, F>: 'pin,
{
    pub local_set: &'pin mut &'a LocalSet,
    pub future: Pin<&'pin mut F>,
}

impl LocalSet {
    fn with<T>(&self, _f: impl FnOnce() -> T) -> T {
        unimplemented!()
    }
}
impl<T: Future> Future for RunUntil<'_, T> {
    type Output = T::Output;
    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let me = self.project();
        me.local_set.with(|| {
            let _ = cx.waker();
            let f = me.future;
            let _ = f.poll(cx);
            Poll::Pending
        })
    }
}

fn main() {}


#![feature(arbitrary_self_types)]

trait Static<'a> {
    fn proof(self: *const Self, s: &'a str) -> &'static str;
}

fn bad_cast<'a>(x: Self::Output) -> *const dyn Static<'a> {
    x as _
}

impl Static<'static> for () {
    fn proof(self: *const Self, s: &'static str) -> &'static str {
        s
    }
}

fn extend_lifetime(s: &str) -> &'static str {
    bad_cast(&()).proof(s)
}

fn main() {
    let s = String::from("Hello World");
    let slice = extend_lifetime(&s);
    println!("Now it exists: {slice}");
    drop(s);
    println!("Now it’s gone: {slice}");
}



#![feature(type_alias_impl_trait)]

#[derive(Copy, Clone)]
struct Foo((u32, u32));

fn main() {
    type T = impl Static;
    let foo: T = Foo((1u32, 2u32));
    let x = move || {
        let Foo((a, b)) = foo;
    };
}

Error output

Command: rustc

error[E0106]: missing lifetime specifier
 --> r_closure331_419FDD4D.rs:8:19
  |
8 |     type T = impl Static;
  |                   ^^^^^^ expected named lifetime parameter
  |
  = note: for more information on higher-ranked polymorphism, visit https://doc.rust-lang.org/nomicon/hrtb.html
help: consider making the bound lifetime-generic with a new `'a` lifetime
  |
8 |     type T = impl for<'a> Static<'a>;
  |                   +++++++       ++++
help: consider introducing a named lifetime parameter
  |
8 |     type T<'a> = impl Static<'a>;
  |           ++++              ++++

error[E0658]: `impl Trait` in type aliases is unstable
 --> r_closure331_419FDD4D.rs:8:14
  |
8 |     type T = impl Static;
  |              ^^^^^^^^^^^
  |
  = note: see issue #63063 <https://github.com/rust-lang/rust/issues/63063> for more information
  = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
  = note: this compiler was built on 2024-06-18; consider upgrading it if it is out of date

Backtrace

error: internal compiler error: compiler/rustc_middle/src/ty/closure.rs:331:21: OpaqueCast unexpected because it isn't captured

thread 'rustc' panicked at compiler/rustc_middle/src/ty/closure.rs:331:21:
Box<dyn Any>
stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
   1: <rustc_errors::diagnostic::BugAbort as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
   2: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>::{closure#0}
   3: rustc_middle::ty::context::tls::with_opt::<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}
   4: rustc_middle::ty::context::tls::with_context_opt::<rustc_middle::ty::context::tls::with_opt<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
   5: rustc_middle::util::bug::bug_fmt
   6: rustc_middle::ty::closure::place_to_string_for_capture
   7: <rustc_hir_typeck::fn_ctxt::FnCtxt>::compute_2229_migrations
   8: <rustc_hir_typeck::fn_ctxt::FnCtxt>::analyze_closure
   9: <rustc_hir_typeck::upvar::InferBorrowKindVisitor as rustc_hir::intravisit::Visitor>::visit_expr
  10: <rustc_hir_typeck::upvar::InferBorrowKindVisitor as rustc_hir::intravisit::Visitor>::visit_block
  11: rustc_hir_typeck::typeck
      [... omitted 1 frame ...]
  12: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 8]>>>
  13: <rustc_hir_analysis::collect::type_of::opaque::TaitConstraintLocator>::check
  14: rustc_hir_analysis::collect::type_of::type_of_opaque
      [... omitted 1 frame ...]
  15: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>>
  16: rustc_hir_analysis::collect::type_of::type_of
      [... omitted 1 frame ...]
  17: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>>
  18: rustc_hir_analysis::check::check::check_item_type
  19: rustc_hir_analysis::check::wfcheck::check_well_formed
      [... omitted 1 frame ...]
  20: rustc_middle::query::plumbing::query_ensure_error_guaranteed::<rustc_query_system::query::caches::VecCache<rustc_hir::hir_id::OwnerId, rustc_middle::query::erase::Erased<[u8; 1]>>, ()>
  21: rustc_hir_analysis::check::wfcheck::check_mod_type_wf
      [... omitted 1 frame ...]
  22: rustc_hir_analysis::check_crate
  23: rustc_interface::passes::run_required_analyses
  24: rustc_interface::passes::analysis
      [... omitted 1 frame ...]
  25: <rustc_interface::queries::QueryResult<&rustc_middle::ty::context::GlobalCtxt>>::enter::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}::{closure#1}::{closure#3}>
  26: rustc_interface::interface::run_compiler::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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: please attach the file at `/Volumes/T7/workspace/240615_100chaos_tree_combine_typ/icefiles/rustc-ice-2024-06-19T06_47_34-44593.txt` to your bug report

query stack during panic:
#0 [typeck] type-checking `main`
#1 [type_of_opaque] computing type of opaque `main::T::{opaque#0}`
#2 [type_of] computing type of `main::T::{opaque#0}`
#3 [check_well_formed] checking that `main::T::{opaque#0}` is well-formed
#4 [check_mod_type_wf] checking that types are well-formed in top-level module
#5 [analysis] running analysis passes on this crate
end of query stack
error[E0391]: cycle detected when computing type of opaque `main::T::{opaque#0}`
 --> r_closure331_419FDD4D.rs:8:14
  |
8 |     type T = impl Static;
  |              ^^^^^^^^^^^
  |
note: ...which requires type-checking `main`...
 --> r_closure331_419FDD4D.rs:7:1
  |
7 | fn main() {
  | ^^^^^^^^^
  = note: ...which requires evaluating trait selection obligation `main::T: core::panic::unwind_safe::RefUnwindSafe`...
  = note: ...which again requires computing type of opaque `main::T::{opaque#0}`, completing the cycle
note: cycle used when computing type of `main::T::{opaque#0}`
 --> r_closure331_419FDD4D.rs:8:14
  |
8 |     type T = impl Static;
  |              ^^^^^^^^^^^
  = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information

error: aborting due to 4 previous errors

Some errors have detailed explanations: E0106, E0391, E0658.
For more information about an error, try `rustc --explain E0106`.

Note

ICE location: compiler/rustc_middle/src/ty/closure.rs#L331

rust/compiler/rustc_middle/src/ty/closure.rs

Lines 309 to 332 in 8fcd4dd

    
           match proj.kind { 
        
               HirProjectionKind::Deref => { 
        
                   curr_string = format!("*{curr_string}"); 
        
               } 
        
               HirProjectionKind::Field(idx, variant) => match place.ty_before_projection(i).kind() { 
        
                   ty::Adt(def, ..) => { 
        
                       curr_string = format!( 
        
                           "{}.{}", 
        
                           curr_string, 
        
                           def.variant(variant).fields[idx].name.as_str() 
        
                       ); 
        
                   } 
        
                   ty::Tuple(_) => { 
        
                       curr_string = format!("{}.{}", curr_string, idx.index()); 
        
                   } 
        
                   _ => { 
        
                       bug!( 
        
                           "Field projection applied to a type other than Adt or Tuple: {:?}.", 
        
                           place.ty_before_projection(i).kind() 
        
                       ) 
        
                   } 
        
               }, 
        
               proj => bug!("{:?} unexpected because it isn't captured", proj), 
        
           }

Might be related to Issue-109298, which points to identical ICE location.

~~Regression in nightly-2023-04-21 (39c6804...8bdcc62)~~

Sorry, I mean nightly-2022-07-26

closing as duplicate of #155497

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ICE: `OpaqueCast unexpected because it isn't captured` in `rustc_middle/src/ty/closure.rs` #126667

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	match proj.kind {
	HirProjectionKind::Deref => {
	curr_string = format!("*{curr_string}");
	}
	HirProjectionKind::Field(idx, variant) => match place.ty_before_projection(i).kind() {
	ty::Adt(def, ..) => {
	curr_string = format!(
	"{}.{}",
	curr_string,
	def.variant(variant).fields[idx].name.as_str()
	);
	}
	ty::Tuple(_) => {
	curr_string = format!("{}.{}", curr_string, idx.index());
	}
	_ => {
	bug!(
	"Field projection applied to a type other than Adt or Tuple: {:?}.",
	place.ty_before_projection(i).kind()
	)
	}
	},
	proj => bug!("{:?} unexpected because it isn't captured", proj),
	}

ICE: OpaqueCast unexpected because it isn't captured in rustc_middle/src/ty/closure.rs #126667

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GrigorenkoPV commented on Jun 19, 2024

lcnr commented on Oct 5, 2026

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ICE: `OpaqueCast unexpected because it isn't captured` in `rustc_middle/src/ty/closure.rs` #126667