ICE: `None` in traits/vtable.rs

[matthiaskrgr]

auto-reduced (treereduce-rust):

#![feature(trait_upcasting)]
trait Supertrait<'a, 'b> {}

trait Subtrait<'a, 'b>: Supertrait<'a, 'b> {}

pub fn ok(x: &dyn for<'a, 'b> Subtrait<'a, 'b>) -> &dyn for<'a> Supertrait<'a, 'a> {
    x
}

pub fn main() {}

original:

//@ revisions: current next
//@ ignore-compare-mode-next-solver (explicit revisions)
//@[next] compile-flags: -Znext-solver

// We should be able to instantiate a binder during trait upcasting.
// This test could be `check-pass`, but we should make sure that we
// do so in both trait solvers.
#![feature(trait_upcasting)]
#![crate_type = "rlib"]
trait Supertrait<'a, 'b> {}

trait Subtrait<'a, 'b>: Supertrait<'a, 'b> {}

impl<'a> Supertrait<'a, 'a> for () {}
impl<'a> Subtrait<'a, 'a> for () {}
fn ok(x: &dyn for<'a, 'b> Subtrait<'a, 'b>) -> &dyn for<'a> Supertrait<'a, 'a> {
    x //~ ERROR mismatched types
    //[current]~^ ERROR mismatched types
}

Version information

rustc 1.83.0-nightly (d194948e5 2024-09-29)
binary: rustc
commit-hash: d194948e50e90f98c62fb64183bce4d866a665af
commit-date: 2024-09-29
host: x86_64-unknown-linux-gnu
release: 1.83.0-nightly
LLVM version: 19.1.0

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Clink-dead-code=true

Program output

warning: trait `Supertrait` is never used
 --> /tmp/icemaker_global_tempdir.J8Vr9e4vti8H/rustc_testrunner_tmpdir_reporting.0UEEGoO5Wkhs/mvce.rs:3:7
  |
3 | trait Supertrait<'a, 'b> {}
  |       ^^^^^^^^^^
  |
  = note: `#[warn(dead_code)]` on by default

warning: trait `Subtrait` is never used
 --> /tmp/icemaker_global_tempdir.J8Vr9e4vti8H/rustc_testrunner_tmpdir_reporting.0UEEGoO5Wkhs/mvce.rs:5:7
  |
5 | trait Subtrait<'a, 'b>: Supertrait<'a, 'b> {}
  |       ^^^^^^^^

warning: function `ok` is never used
 --> /tmp/icemaker_global_tempdir.J8Vr9e4vti8H/rustc_testrunner_tmpdir_reporting.0UEEGoO5Wkhs/mvce.rs:7:4
  |
7 | fn ok(x: &dyn for<'a, 'b> Subtrait<'a, 'b>) -> &dyn for<'a> Supertrait<'a, 'a> {
  |    ^^

thread 'rustc' panicked at compiler/rustc_trait_selection/src/traits/vtable.rs:426:77:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0:     0x7402f1ccf4ca - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h9a066335bbf3c70b
   1:     0x7402f24033e6 - core::fmt::write::h4d7b6dcfa06e4b7a
   2:     0x7402f35b5bd1 - std::io::Write::write_fmt::h4eb2f351153c62f5
   3:     0x7402f1ccf322 - std::sys::backtrace::BacktraceLock::print::h61d14380f524de24
   4:     0x7402f1cd1841 - std::panicking::default_hook::{{closure}}::hee65cb92729f1c6f
   5:     0x7402f1cd1674 - std::panicking::default_hook::h10225ef2c1ae2cf5
   6:     0x7402f0d9cacf - std[48a393fc970d1838]::panicking::update_hook::<alloc[639799fc786021ce]::boxed::Box<rustc_driver_impl[72d45a44622a3bfe]::install_ice_hook::{closure#0}>>::{closure#0}
   7:     0x7402f1cd1f58 - std::panicking::rust_panic_with_hook::hb124b874e22ff2c5
   8:     0x7402f1cd1cf6 - std::panicking::begin_panic_handler::{{closure}}::h69c13d865db3420d
   9:     0x7402f1ccf979 - std::sys::backtrace::__rust_end_short_backtrace::h435b1bbccf81cd41
  10:     0x7402f1cd19ec - rust_begin_unwind
  11:     0x7402ef5f5bd0 - core::panicking::panic_fmt::haafd805879858244
  12:     0x7402ef4357ec - core::panicking::panic::hc1dd6eb7439635bd
  13:     0x7402efe0cdf9 - core::option::unwrap_failed::heaa361f2da5b5d1a
  14:     0x7402f1b6e761 - rustc_trait_selection[fa1246763012ec30]::traits::vtable::supertrait_vtable_slot
  15:     0x7402f17e5946 - rustc_query_impl[ec7eda03afdf420d]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[ec7eda03afdf420d]::query_impl::supertrait_vtable_slot::dynamic_query::{closure#2}::{closure#0}, rustc_middle[192bdac49f720747]::query::erase::Erased<[u8; 16usize]>>
  16:     0x7402f17ca559 - <rustc_query_impl[ec7eda03afdf420d]::query_impl::supertrait_vtable_slot::dynamic_query::{closure#2} as core[a5e590a05170c700]::ops::function::FnOnce<(rustc_middle[192bdac49f720747]::ty::context::TyCtxt, (rustc_middle[192bdac49f720747]::ty::Ty, rustc_middle[192bdac49f720747]::ty::Ty))>>::call_once
  17:     0x7402f1741ddc - rustc_query_system[4eeeb108be8c1cc5]::query::plumbing::try_execute_query::<rustc_query_impl[ec7eda03afdf420d]::DynamicConfig<rustc_query_system[4eeeb108be8c1cc5]::query::caches::DefaultCache<(rustc_middle[192bdac49f720747]::ty::Ty, rustc_middle[192bdac49f720747]::ty::Ty), rustc_middle[192bdac49f720747]::query::erase::Erased<[u8; 16usize]>>, false, false, false>, rustc_query_impl[ec7eda03afdf420d]::plumbing::QueryCtxt, false>
  18:     0x7402f18063e2 - rustc_query_impl[ec7eda03afdf420d]::query_impl::supertrait_vtable_slot::get_query_non_incr::__rust_end_short_backtrace
  19:     0x7402f2a3c1b6 - rustc_codegen_ssa[3c131d82a17c56d8]::base::unsized_info::<rustc_codegen_llvm[808d3172d33b3fe]::builder::Builder>
  20:     0x7402f2a3c4d1 - rustc_codegen_ssa[3c131d82a17c56d8]::base::unsize_ptr::<rustc_codegen_llvm[808d3172d33b3fe]::builder::Builder>
  21:     0x7402f2a42ba9 - <rustc_codegen_ssa[3c131d82a17c56d8]::mir::FunctionCx<rustc_codegen_llvm[808d3172d33b3fe]::builder::Builder>>::codegen_rvalue_operand
  22:     0x7402f324c8fe - rustc_codegen_ssa[3c131d82a17c56d8]::mir::codegen_mir::<rustc_codegen_llvm[808d3172d33b3fe]::builder::Builder>
  23:     0x7402f322d335 - rustc_codegen_llvm[808d3172d33b3fe]::base::compile_codegen_unit::module_codegen
  24:     0x7402f31c9553 - <rustc_codegen_llvm[808d3172d33b3fe]::LlvmCodegenBackend as rustc_codegen_ssa[3c131d82a17c56d8]::traits::backend::ExtraBackendMethods>::compile_codegen_unit
  25:     0x7402f31c604d - <rustc_codegen_llvm[808d3172d33b3fe]::LlvmCodegenBackend as rustc_codegen_ssa[3c131d82a17c56d8]::traits::backend::CodegenBackend>::codegen_crate
  26:     0x7402f33fc770 - <rustc_interface[c07a9da7023f0850]::queries::Linker>::codegen_and_build_linker
  27:     0x7402f3131e8b - rustc_interface[c07a9da7023f0850]::interface::run_compiler::<core[a5e590a05170c700]::result::Result<(), rustc_span[28a6cfa051eff088]::ErrorGuaranteed>, rustc_driver_impl[72d45a44622a3bfe]::run_compiler::{closure#0}>::{closure#1}
  28:     0x7402f31bcc10 - std[48a393fc970d1838]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[c07a9da7023f0850]::util::run_in_thread_with_globals<rustc_interface[c07a9da7023f0850]::util::run_in_thread_pool_with_globals<rustc_interface[c07a9da7023f0850]::interface::run_compiler<core[a5e590a05170c700]::result::Result<(), rustc_span[28a6cfa051eff088]::ErrorGuaranteed>, rustc_driver_impl[72d45a44622a3bfe]::run_compiler::{closure#0}>::{closure#1}, core[a5e590a05170c700]::result::Result<(), rustc_span[28a6cfa051eff088]::ErrorGuaranteed>>::{closure#0}, core[a5e590a05170c700]::result::Result<(), rustc_span[28a6cfa051eff088]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[a5e590a05170c700]::result::Result<(), rustc_span[28a6cfa051eff088]::ErrorGuaranteed>>
  29:     0x7402f31bd2f0 - <<std[48a393fc970d1838]::thread::Builder>::spawn_unchecked_<rustc_interface[c07a9da7023f0850]::util::run_in_thread_with_globals<rustc_interface[c07a9da7023f0850]::util::run_in_thread_pool_with_globals<rustc_interface[c07a9da7023f0850]::interface::run_compiler<core[a5e590a05170c700]::result::Result<(), rustc_span[28a6cfa051eff088]::ErrorGuaranteed>, rustc_driver_impl[72d45a44622a3bfe]::run_compiler::{closure#0}>::{closure#1}, core[a5e590a05170c700]::result::Result<(), rustc_span[28a6cfa051eff088]::ErrorGuaranteed>>::{closure#0}, core[a5e590a05170c700]::result::Result<(), rustc_span[28a6cfa051eff088]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[a5e590a05170c700]::result::Result<(), rustc_span[28a6cfa051eff088]::ErrorGuaranteed>>::{closure#1} as core[a5e590a05170c700]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  30:     0x7402f31bd6eb - std::sys::pal::unix::thread::Thread::new::thread_start::h8fe6ba811b9bdf93
  31:     0x7402f484739d - <unknown>
  32:     0x7402f48cc49c - <unknown>
  33:                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 1.83.0-nightly (d194948e5 2024-09-29) running on x86_64-unknown-linux-gnu

note: compiler flags: -C link-dead-code=true -Z dump-mir-dir=dir

query stack during panic:
#0 [supertrait_vtable_slot] finding the slot within vtable for trait object `dyn for<'a> Supertrait<'a, 'a>` vtable ptr during trait upcasting coercion from `dyn for<'a, 'b> Subtrait<'a, 'b>` vtable
end of query stack
warning: 3 warnings emitted

@rustbot label +F-trait_upcasting

[matthiaskrgr]

bisects to #130866