ice: unequal types in stable mir

[matthiaskrgr]

I tried this code:

type BuiltIn = for<'a> fn(&str);

struct Function {
    inner: BuiltIn,
}

impl Function {
    fn new(subr: BuiltIn) -> Self {
        Self { inner: subr }
    }
}

fn dummy(_: &str) {}

#[kani::proof]
fn main() {
    let func1 = Function::new(dummy);
    let func2 = Function::new(dummy);
    let inner: fn(&'static _) -> _ = func1.inner;
    assert!(inner == func2.inner);
}

using the following command line invocation:

kani file.rs 

with Kani version: 0.46.0

I expected to see this happen: explanation

Instead, this happened: explanation

Kani Rust Verifier 0.46.0 (standalone)
thread 'rustc' panicked at compiler/stable_mir/src/mir/body.rs:384:17:
assertion `left == right` failed
  left: Ty { id: 5, kind: RigidTy(FnPtr(Binder { value: FnSig { inputs_and_output: [Ty { id: 4, kind: RigidTy(Ref(Region { kind: ReErased }, Ty { id: 10, kind: RigidTy(Str) }, Not)) }, Ty { id: 6, kind: RigidTy(Tuple([])) }], c_variadic: false, unsafety: Normal, abi: Rust }, bound_vars: [] })) }
 right: Ty { id: 2, kind: RigidTy(FnPtr(Binder { value: FnSig { inputs_and_output: [Ty { id: 9, kind: RigidTy(Ref(Region { kind: ReBound(0, BoundRegion { var: 0, kind: BrAnon }) }, Ty { id: 10, kind: RigidTy(Str) }, Not)) }, Ty { id: 6, kind: RigidTy(Tuple([])) }], c_variadic: false, unsafety: Normal, abi: Rust }, bound_vars: [Region(BrAnon)] })) }
stack backtrace:
   0:     0x7f3644d8be86 - std::backtrace_rs::backtrace::libunwind::trace::haa62de98ce20d13c
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
   1:     0x7f3644d8be86 - std::backtrace_rs::backtrace::trace_unsynchronized::h4bc7f582e9f49dbd
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f3644d8be86 - std::sys_common::backtrace::_print_fmt::h07d78988ae6e922d
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x7f3644d8be86 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::he72c24e459b4aee4
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f3644dde740 - core::fmt::rt::Argument::fmt::h9ff3b213e1468f5f
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/core/src/fmt/rt.rs:142:9
   5:     0x7f3644dde740 - core::fmt::write::h0ab1f59280077a18
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/core/src/fmt/mod.rs:1120:17
   6:     0x7f3644d7f7bf - std::io::Write::write_fmt::h2f48f6201433d434
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/std/src/io/mod.rs:1810:15
   7:     0x7f3644d8bc64 - std::sys_common::backtrace::_print::h710dac96d5446d07
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7f3644d8bc64 - std::sys_common::backtrace::print::h22982b9f2c94c190
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7f3644d8e9f7 - std::panicking::default_hook::{{closure}}::h19052586580466eb
  10:     0x7f3644d8e759 - std::panicking::default_hook::h9f3f4c25f2a49543
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/std/src/panicking.rs:292:9
  11:     0x557ba698b29d - kani_compiler::session::PANIC_HOOK::{{closure}}::{{closure}}::h62bee1eb7956b9f6
  12:     0x557ba698aaa3 - kani_compiler::codegen_cprover_gotoc::utils::debug::DEFAULT_HOOK::{{closure}}::{{closure}}::h252d31e703366824
  13:     0x7f3644d8f146 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h0ebb0eb5cf5e84f1
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/alloc/src/boxed.rs:2030:9
  14:     0x7f3644d8f146 - std::panicking::rust_panic_with_hook::hb83cfb3ac729d1b2
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/std/src/panicking.rs:785:13
  15:     0x7f3644d8ee92 - std::panicking::begin_panic_handler::{{closure}}::hf6588d71adde3329
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/std/src/panicking.rs:659:13
  16:     0x7f3644d8c386 - std::sys_common::backtrace::__rust_end_short_backtrace::hfa69dd6720275711
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/std/src/sys_common/backtrace.rs:171:18
  17:     0x7f3644d8ebe4 - rust_begin_unwind
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/std/src/panicking.rs:647:5
  18:     0x7f3644ddae45 - core::panicking::panic_fmt::h3d775185360585e3
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/core/src/panicking.rs:72:14
  19:     0x7f3644ddb3db - core::panicking::assert_failed_inner::h0e5c67b40620ee84
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/core/src/panicking.rs:342:17
  20:     0x7f3648718ca3 - core[2f78b8535a2e64fa]::panicking::assert_failed::<stable_mir[64b791d3cb4792a]::ty::Ty, stable_mir[64b791d3cb4792a]::ty::Ty>
  21:     0x7f364871c6a6 - <stable_mir[64b791d3cb4792a]::mir::body::BinOp>::ty
  22:     0x7f364871c86c - <stable_mir[64b791d3cb4792a]::mir::body::Rvalue>::ty
  23:     0x557ba691e1f9 - kani_compiler::codegen_cprover_gotoc::codegen::statement::<impl kani_compiler::codegen_cprover_gotoc::context::goto_ctx::GotocCtx>::codegen_statement::h9ef1fd17419243a3
  24:     0x557ba69373eb - kani_compiler::codegen_cprover_gotoc::utils::debug::<impl kani_compiler::codegen_cprover_gotoc::context::goto_ctx::GotocCtx>::call_with_panic_debug_info::h70ea6b1d619c790d
  25:     0x557ba69f9e9a - kani_compiler::codegen_cprover_gotoc::compiler_interface::GotocCodegenBackend::codegen_items::h179e069baadeebc1
  26:     0x557ba69b1430 - scoped_tls::ScopedKey<T>::set::h462dbe7b3063cb5c
  27:     0x557ba69e91a4 - rustc_smir::rustc_internal::init::hdab7351afa62793a
  28:     0x557ba69b4054 - stable_mir::compiler_interface::run::hdc01671daf50c78a
  29:     0x557ba69fd62e - <kani_compiler::codegen_cprover_gotoc::compiler_interface::GotocCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate::hd5728f8a33105c7d
  30:     0x7f364986aff0 - rustc_interface[79a3a7c6d29fbb15]::passes::start_codegen
  31:     0x7f364986a75c - <rustc_interface[79a3a7c6d29fbb15]::queries::Queries>::codegen_and_build_linker
  32:     0x7f3649b7a44a - rustc_interface[79a3a7c6d29fbb15]::interface::run_compiler::<core[2f78b8535a2e64fa]::result::Result<(), rustc_span[8cc10a3d00093188]::ErrorGuaranteed>, rustc_driver_impl[27708ea34d8a9a18]::run_compiler::{closure#0}>::{closure#0}
  33:     0x7f3649de5986 - std[da4468a6436061de]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[79a3a7c6d29fbb15]::util::run_in_thread_with_globals<rustc_interface[79a3a7c6d29fbb15]::util::run_in_thread_pool_with_globals<rustc_interface[79a3a7c6d29fbb15]::interface::run_compiler<core[2f78b8535a2e64fa]::result::Result<(), rustc_span[8cc10a3d00093188]::ErrorGuaranteed>, rustc_driver_impl[27708ea34d8a9a18]::run_compiler::{closure#0}>::{closure#0}, core[2f78b8535a2e64fa]::result::Result<(), rustc_span[8cc10a3d00093188]::ErrorGuaranteed>>::{closure#0}, core[2f78b8535a2e64fa]::result::Result<(), rustc_span[8cc10a3d00093188]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[2f78b8535a2e64fa]::result::Result<(), rustc_span[8cc10a3d00093188]::ErrorGuaranteed>>
  34:     0x7f3649de57b3 - <<std[da4468a6436061de]::thread::Builder>::spawn_unchecked_<rustc_interface[79a3a7c6d29fbb15]::util::run_in_thread_with_globals<rustc_interface[79a3a7c6d29fbb15]::util::run_in_thread_pool_with_globals<rustc_interface[79a3a7c6d29fbb15]::interface::run_compiler<core[2f78b8535a2e64fa]::result::Result<(), rustc_span[8cc10a3d00093188]::ErrorGuaranteed>, rustc_driver_impl[27708ea34d8a9a18]::run_compiler::{closure#0}>::{closure#0}, core[2f78b8535a2e64fa]::result::Result<(), rustc_span[8cc10a3d00093188]::ErrorGuaranteed>>::{closure#0}, core[2f78b8535a2e64fa]::result::Result<(), rustc_span[8cc10a3d00093188]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[2f78b8535a2e64fa]::result::Result<(), rustc_span[8cc10a3d00093188]::ErrorGuaranteed>>::{closure#1} as core[2f78b8535a2e64fa]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  35:     0x7f3644d98735 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hda2c57e98ef914e1
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/alloc/src/boxed.rs:2016:9
  36:     0x7f3644d98735 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h4c1ca1ffb3984aed
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/alloc/src/boxed.rs:2016:9
  37:     0x7f3644d98735 - std::sys::pal::unix::thread::Thread::new::thread_start::h6dfa281031503fa8
                               at /rustc/7ffc697ce10f19447c0ce338428ae4b9bc0c041c/library/std/src/sys/pal/unix/thread.rs:108:17
  38:     0x7f3644a979eb - <unknown>
  39:     0x7f3644b1b7cc - <unknown>
  40:                0x0 - <unknown>

Kani unexpectedly panicked during compilation.
Please file an issue here: https://github.com/model-checking/kani/issues/new?labels=bug&template=bug_report.md

[Kani] current codegen item: codegen_function: main
main
[Kani] current codegen location: Loc { file: "issue-91636.rs", function: None, start_line: 16, start_col: Some(1), end_line: 16, end_col: Some(10) }
error: /home/matthias/.kani/kani-0.46.0/bin/kani-compiler exited with status exit status: 101