Explicit tail call returning a HRTB causes ICE: "hir typeck should have checked the return type already" #144892
Description
Code
#![feature(explicit_tail_calls)]
#![allow(incomplete_features)]
fn foo<'a>() -> fn(&'static i32) {
become bar();
}
fn bar() -> for<'a> fn(&'a i32) {
dummy
}
fn dummy(_: &i32) {}@rustbot labels +F-explicit_tail_calls +requires-incomplete-features
Meta
Reproducible on the playground with version 1.91.0-nightly (2025-08-03 f34ba774c78ea32b7c40)
Error output
error: internal compiler error: compiler/rustc_mir_build/src/check_tail_calls.rs:130:17: hir typeck should have checked the return type already
--> src/lib.rs:5:5
|
5 | become bar();
| ^^^^^^^^^^^^
Backtrace
thread 'rustc' panicked at compiler/rustc_mir_build/src/check_tail_calls.rs:130:17:
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_errors::DiagCtxtHandle>::span_bug::<rustc_span::span_encoding::Span, alloc::string::String>
3: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>::{closure#0}
4: 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::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}, !>
6: rustc_middle::util::bug::span_bug_fmt::<rustc_span::span_encoding::Span>
7: <rustc_mir_build::check_tail_calls::TailCallCkVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
8: <rustc_mir_build::check_tail_calls::TailCallCkVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
9: <rustc_mir_build::check_tail_calls::TailCallCkVisitor as rustc_middle::thir::visit::Visitor>::visit_block
10: <rustc_mir_build::check_tail_calls::TailCallCkVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
11: <rustc_mir_build::check_tail_calls::TailCallCkVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
12: <rustc_mir_build::check_tail_calls::TailCallCkVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
[... omitted 1 frame ...]
13: rustc_mir_build::builder::build_mir
14: rustc_mir_transform::mir_built
[... omitted 1 frame ...]
15: rustc_mir_build::check_unsafety::check_unsafety
[... omitted 1 frame ...]
16: <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface::passes::run_required_analyses::{closure#1}::{closure#0}>::{closure#0}
17: rustc_interface::passes::analysis
[... omitted 1 frame ...]
18: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
19: rustc_interface::interface::run_compiler::<(), 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 `/playground/rustc-ice-2025-08-04T08_41_41-26.txt` to your bug report
note: compiler flags: --crate-type lib -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2
note: some of the compiler flags provided by cargo are hidden
query stack during panic:
#0 [check_tail_calls] tail-call-checking `foo`
#1 [mir_built] building MIR for `foo`
#2 [check_unsafety] unsafety-checking `foo`
#3 [analysis] running analysis passes on this crate
end of query stack
error: could not compile `playground` (lib)