ICE from explicit tail call in defaulted trait method #144985
Description
Code
#![feature(explicit_tail_calls)] #![expect(incomplete_features)] trait Trait {} trait Trait { fn foo(&self) { become self.foo(); } }@rustbot labels +F-explicit_tail_calls +requires-incomplete-features
Meta
Reproducible on the playground with version 1.91.0-nightly (2025-08-05 ec7c02612527d185c379)
Error output
error[E0428]: the name `Trait` is defined multiple times --> src/lib.rs:6:1 | 4 | trait Trait {} | ----------- previous definition of the trait `Trait` here 5 | 6 | trait Trait { | ^^^^^^^^^^^ `Trait` redefined here | = note: `Trait` must be defined only once in the type namespace of this module error: internal compiler error: compiler/rustc_middle/src/ty/instance.rs:633:21: failed to resolve instance for <Self as Trait>::foo --> src/lib.rs:7:5 | 7 | fn foo(&self) { | ^^^^^^^^^^^^^ Backtrace
thread 'rustc' panicked at compiler/rustc_middle/src/ty/instance.rs:633:21: 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_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_middle::ty::instance::Instance>::expect_resolve 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_expr 10: <rustc_mir_build::check_tail_calls::TailCallCkVisitor as rustc_middle::thir::visit::Visitor>::visit_block 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 13: <rustc_mir_build::check_tail_calls::TailCallCkVisitor as rustc_middle::thir::visit::Visitor>::visit_expr [... omitted 1 frame ...] 14: rustc_mir_build::builder::build_mir 15: rustc_mir_transform::mir_built [... omitted 1 frame ...] 16: rustc_mir_build::check_unsafety::check_unsafety [... omitted 1 frame ...] 17: <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface::passes::run_required_analyses::{closure#1}::{closure#0}>::{closure#0} 18: rustc_interface::passes::analysis [... omitted 1 frame ...] 19: 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} 20: 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-2025-08-06T07_27_59-27.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 `Trait::foo` #1 [mir_built] building MIR for `Trait::foo` #2 [check_unsafety] unsafety-checking `Trait::foo` #3 [analysis] running analysis passes on this crate end of query stack For more information about this error, try `rustc --explain E0428`.