ICE: failed to resolve instance for <fn() -> impl ...>

[tBuLi12]

Code

trait Handler {
    fn handle(&self) {}
}

impl<H: Handler, F: Fn() -> H> Handler for F {}

impl<L: Handler> Handler for (L,) {}

fn one() -> impl Handler {
    (one,)
}

fn main() {
    one.handle();
}

Meta

rustc --version --verbose:

rustc 1.76.0 (07dca489a 2024-02-04)
binary: rustc
commit-hash: 07dca489ac2d933c78d3c5158e3f43beefeb02ce
commit-date: 2024-02-04
host: x86_64-pc-windows-msvc
release: 1.76.0
LLVM version: 17.0.6

Error output

error: internal compiler error: compiler\rustc_middle\src\ty\instance.rs:414:25: failed to resolve instance for <fn() -> impl Handler {one} as Handler>::handle: Ok(
                                    None,
                                )

Backtrace

thread 'rustc' panicked at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce\compiler\rustc_errors\src\lib.rs:1119:75:
Box<dyn Any>
stack backtrace:
   0:     0x7ffe056a22c2 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h7851e041f2b8bcc2
   1:     0x7ffe056d4cdd - core::fmt::write::h1642dfca37b49735
   2:     0x7ffe05698ca1 - <std::io::IoSlice as core::fmt::Debug>::fmt::h7801514a6fc13a4a
   3:     0x7ffe056a20ea - std::sys_common::backtrace::lock::h8caaa69a6cc2258b
   4:     0x7ffe056a5529 - std::panicking::default_hook::h67f6260a0bf37eca
   5:     0x7ffe056a51e5 - std::panicking::default_hook::h67f6260a0bf37eca
   6:     0x7ffe09f2fb03 - <tracing_subscriber[b129777695c18cc]::fmt::format::Writer>::write_fmt
   7:     0x7ffe056a5b43 - std::panicking::rust_panic_with_hook::h870983d929e74e12
   8:     0x7ffe0b3b7438 - <rustc_span[64dbdf40f18d9543]::symbol::MacroRulesNormalizedIdent as rustc_errors[9e3a9f6acb1d6850]::diagnostic::IntoDiagnosticArg>::into_diagnostic_arg
   9:     0x7ffe0b3b6d59 - <rustc_span[64dbdf40f18d9543]::symbol::MacroRulesNormalizedIdent as rustc_errors[9e3a9f6acb1d6850]::diagnostic::IntoDiagnosticArg>::into_diagnostic_arg
  10:     0x7ffe0b3afb39 - <std[9ab95dd99822253f]::io::error::Error as rustc_errors[9e3a9f6acb1d6850]::diagnostic::IntoDiagnosticArg>::into_diagnostic_arg
  11:     0x7ffe0b39747c - <rustc_errors[9e3a9f6acb1d6850]::diagnostic_builder::Bug as rustc_errors[9e3a9f6acb1d6850]::diagnostic_builder::EmissionGuarantee>::diagnostic_builder_emit_producing_guarantee
  12:     0x7ffe0b23f3b7 - rustc_middle[29ac2ae09cb008db]::ty::context::tls::TLV::__getit::destroy
  13:     0x7ffe0b23d3b3 - rustc_middle[29ac2ae09cb008db]::util::bug::bug_fmt
  14:     0x7ffe0b23d21d - <rustc_middle[29ac2ae09cb008db]::traits::util::Elaborator as core[d8a3f01ca499b8ab]::iter::traits::iterator::Iterator>::next
  15:     0x7ffe0b23d1ea - <rustc_middle[29ac2ae09cb008db]::traits::util::Elaborator as core[d8a3f01ca499b8ab]::iter::traits::iterator::Iterator>::next
  16:     0x7ffe0b23d2c2 - rustc_middle[29ac2ae09cb008db]::util::bug::bug_fmt
  17:     0x7ffe09de7917 - <rustc_middle[29ac2ae09cb008db]::ty::instance::Instance>::expect_resolve
  18:     0x7ffe091dbf2b - <rustc_monomorphize[5b0405cbcca7e001]::collector::MirUsedCollector as rustc_middle[29ac2ae09cb008db]::mir::visit::Visitor>::visit_constant
  19:     0x7ffe091d8c8b - <rustc_monomorphize[5b0405cbcca7e001]::collector::MirUsedCollector as rustc_middle[29ac2ae09cb008db]::mir::visit::Visitor>::visit_operand
  20:     0x7ffe088a6645 - <rustc_hir_analysis[2ba85467cc3c2e66]::check::wfcheck::check_where_clauses::{closure#2}::CountParams as rustc_type_ir[fb309861c70c8016]::visit::TypeVisitor<rustc_middle[29ac2ae09cb008db]::ty::context::TyCtxt>>::visit_const
  21:     0x7ffe088abe52 - <rustc_hir_analysis[2ba85467cc3c2e66]::check::wfcheck::check_where_clauses::{closure#2}::CountParams as rustc_type_ir[fb309861c70c8016]::visit::TypeVisitor<rustc_middle[29ac2ae09cb008db]::ty::context::TyCtxt>>::visit_const
  22:     0x7ffe088a8518 - <rustc_hir_analysis[2ba85467cc3c2e66]::check::wfcheck::check_where_clauses::{closure#2}::CountParams as rustc_type_ir[fb309861c70c8016]::visit::TypeVisitor<rustc_middle[29ac2ae09cb008db]::ty::context::TyCtxt>>::visit_const
  23:     0x7ffe091d14bd - rustc_monomorphize[5b0405cbcca7e001]::partitioning::collect_and_partition_mono_items
  24:     0x7ffe08ad038a - rustc_query_impl[1b1c3ff2f5873f4d]::profiling_support::alloc_self_profile_query_strings
  25:     0x7ffe08a9b22d - rustc_traits[39dfbaf382113380]::type_op::type_op_normalize_fn_sig
  26:     0x7ffe08b493fc - rustc_query_impl[1b1c3ff2f5873f4d]::profiling_support::alloc_self_profile_query_strings
  27:     0x7ffe08aee434 - rustc_query_impl[1b1c3ff2f5873f4d]::profiling_support::alloc_self_profile_query_strings
  28:     0x7ffe08afaf7e - rustc_query_impl[1b1c3ff2f5873f4d]::profiling_support::alloc_self_profile_query_strings
  29:     0x7ffe0ab43c44 - <rustc_query_impl[1b1c3ff2f5873f4d]::plumbing::QueryCtxt as rustc_query_system[79eaec2bcc989eb1]::query::QueryContext>::depth_limit_error
  30:     0x7ffe06100464 - <rustc_codegen_llvm[8a535c964cfc05c8]::back::lto::ModuleBuffer as core[d8a3f01ca499b8ab]::ops::drop::Drop>::drop
  31:     0x7ffe060e2cff - <rustc_codegen_llvm[8a535c964cfc05c8]::LlvmCodegenBackend as rustc_codegen_ssa[1dc4bfd57c326e00]::traits::backend::CodegenBackend>::codegen_crate
  32:     0x7ffe060a9439 - rustc_interface[9ef98228d448de4b]::interface::parse_check_cfg
  33:     0x7ffe06090b37 - rustc_interface[9ef98228d448de4b]::passes::start_codegen
  34:     0x7ffe060a27e2 - rustc_interface[9ef98228d448de4b]::interface::parse_check_cfg
  35:     0x7ffe06081b0f - <rustc_interface[9ef98228d448de4b]::queries::Queries>::codegen_and_build_linker
  36:     0x7ffe06040ee1 - rustc_driver_impl[5ff3db5439d2e5e5]::args::arg_expand_all
  37:     0x7ffe06058809 - <rustc_middle[29ac2ae09cb008db]::ty::SymbolName as core[d8a3f01ca499b8ab]::fmt::Debug>::fmt
  38:     0x7ffe0605770f - <rustc_middle[29ac2ae09cb008db]::ty::SymbolName as core[d8a3f01ca499b8ab]::fmt::Debug>::fmt
  39:     0x7ffe06061068 - <rustc_middle[29ac2ae09cb008db]::ty::SymbolName as core[d8a3f01ca499b8ab]::fmt::Debug>::fmt
  40:     0x7ffe056b7ebc - std::sys::windows::thread::Thread::new::h827e23232df84eef
  41:     0x7fff00ab257d - BaseThreadInitThunk
  42:     0x7fff0196aa58 - RtlUserThreadStart

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 1.76.0 (07dca489a 2024-02-04) running on x86_64-pc-windows-msvc

note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED]

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack

[compiler-errors]

This is correctly reported as an overflow in the new trait solver:

error[E0275]: overflow evaluating the requirement `impl Handler == (fn() -> impl Handler {one},)`
  --> <source>:10:5
   |
10 |     (one,)
   |     ^^^^^^

error[E0275]: overflow evaluating the requirement `(fn() -> impl Handler {one},) <: impl Handler`
  --> <source>:9:26
   |
9  |   fn one() -> impl Handler {
   |  __________________________^
10 | |     (one,)
11 | | }
   | |_^

error: aborting due to 2 previous errors

[GrigorenkoPV]

On 1.34 and before that, the compiler SIGSEGVs with stack overflow.

On 1.35-1.40 it works just fine, surprisingly.

On 1.41-1.47 it ICEs with thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:918:9.

On 1.48-1.61 it ICEs with "no errors encountered even though delay_span_bug issued".

On 1.62-1.67 it ICEs with "called Option::unwrap() on a None value', compiler/rustc_monomorphize/src/collector.rs:934:13".

Starting with 1.68 it ICEs with the same message as in the issue.