ICE with generics.

[10maurycy10]

Code

https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=3f6d8b903da8b01348137330371e7ff5

fn main() {
   println!("{:?}", {
   type T = ();

     pub fn cloneit (it: &'_ mut T) -> (&'_ mut T, &'_ mut T)
where
    for<'any> &'any mut T : Clone, {
        (it.clone(), it)
    }
}); }

Meta

rustc --version --verbose:

1.61.0-nightly (2022-03-05 c274e4969f058b1c6442)

Error output

Compiling playground v0.0.1 (/playground)
warning: type alias is never used: `T`
 [--> src/main.rs:3:4
](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=4c9140e1c57f836e8185361ea26f0541#)  |
3 |    type T = ();
  |    ^^^^^^^^^^^^
  |
  = note: `#[warn(dead_code)]` on by default

warning: function is never used: `clone`
 [--> src/main.rs:5:13
](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=4c9140e1c57f836e8185361ea26f0541#)  |
5 |      pub fn clone (it: &'_ mut T) -> (&'_ mut T, &'_ mut T)
  |             ^^^^^

error: internal compiler error: no errors encountered even though `delay_span_bug` issued

error: internal compiler error: Encountered error `Unimplemented` selecting `Binder(<&mut () as std::clone::Clone>, [])` during codegen
  |
  = note: delayed at compiler/rustc_trait_selection/src/traits/codegen.rs:69:32

thread 'rustc' panicked at 'Box<dyn Any>', compiler/rustc_errors/src/lib.rs:1266:13
stack backtrace:
   0:     0x7fce63604d2c - std::backtrace_rs::backtrace::libunwind::trace::hd9d6c66ed2138bb0
                               at /rustc/c274e4969f058b1c644243181ece9f829efa7594/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7fce63604d2c - std::backtrace_rs::backtrace::trace_unsynchronized::ha4edb04af5a111d2
                               at /rustc/c274e4969f058b1c644243181ece9f829efa7594/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7fce63604d2c - std::sys_common::backtrace::_print_fmt::h34bfe6ef54352a7f
                               at /rustc/c274e4969f058b1c644243181ece9f829efa7594/library/std/src/sys_common/backtrace.rs:66:5
   3:     0x7fce63604d2c - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h91638cd7890644b7
                               at /rustc/c274e4969f058b1c644243181ece9f829efa7594/library/std/src/sys_common/backtrace.rs:45:22
   4:     0x7fce6365ebec - core::fmt::write::h407f77bceaf22b75
                               at /rustc/c274e4969f058b1c644243181ece9f829efa7594/library/core/src/fmt/mod.rs:1190:17
   5:     0x7fce635f5801 - std::io::Write::write_fmt::h85de75cd3cb86034
                               at /rustc/c274e4969f058b1c644243181ece9f829efa7594/library/std/src/io/mod.rs:1655:15
   6:     0x7fce63607c65 - std::sys_common::backtrace::_print::h9303e0f315439c4b
                               at /rustc/c274e4969f058b1c644243181ece9f829efa7594/library/std/src/sys_common/backtrace.rs:48:5
   7:     0x7fce63607c65 - std::sys_common::backtrace::print::h278cbd6c00b20bf7
                               at /rustc/c274e4969f058b1c644243181ece9f829efa7594/library/std/src/sys_common/backtrace.rs:35:9
   8:     0x7fce63607c65 - std::panicking::default_hook::{{closure}}::h66dc8e0c0481f9ac
                               at /rustc/c274e4969f058b1c644243181ece9f829efa7594/library/std/src/panicking.rs:295:22
   9:     0x7fce63607908 - std::panicking::default_hook::h3732f22170eb6fcb
                               at /rustc/c274e4969f058b1c644243181ece9f829efa7594/library/std/src/panicking.rs:314:9
  10:     0x7fce63d9d4a1 - rustc_driver[a243c3d9738e9cda]::DEFAULT_HOOK::{closure#0}::{closure#0}
  11:     0x7fce63608501 - std::panicking::rust_panic_with_hook::hfa6a9afb1a6b2eff
                               at /rustc/c274e4969f058b1c644243181ece9f829efa7594/library/std/src/panicking.rs:702:17
  12:     0x7fce64e2dfb1 - std[54a224735ab911a]::panicking::begin_panic::<rustc_errors[e9d593471e7e5a86]::ExplicitBug>::{closure#0}
  13:     0x7fce64e2dea6 - std[54a224735ab911a]::sys_common::backtrace::__rust_end_short_backtrace::<std[54a224735ab911a]::panicking::begin_panic<rustc_errors[e9d593471e7e5a86]::ExplicitBug>::{closure#0}, !>
  14:     0x7fce64e348ef - std[54a224735ab911a]::panicking::begin_panic::<rustc_errors[e9d593471e7e5a86]::ExplicitBug>
  15:     0x7fce64e41756 - std[54a224735ab911a]::panic::panic_any::<rustc_errors[e9d593471e7e5a86]::ExplicitBug>
  16:     0x7fce664bd16e - <rustc_errors[e9d593471e7e5a86]::HandlerInner as core[f66f8263def5172a]::ops::drop::Drop>::drop
  17:     0x7fce65bfb338 - core[f66f8263def5172a]::ptr::drop_in_place::<rustc_session[7e14f15cd8696afc]::parse::ParseSess>
  18:     0x7fce65bfde8a - <alloc[16beeacba2f7b906]::rc::Rc<rustc_session[7e14f15cd8696afc]::session::Session> as core[f66f8263def5172a]::ops::drop::Drop>::drop
  19:     0x7fce65be652d - core[f66f8263def5172a]::ptr::drop_in_place::<rustc_interface[ee304f5e577cf6b9]::interface::Compiler>
  20:     0x7fce65be6033 - rustc_span[1b916fa4cb305af0]::with_source_map::<core[f66f8263def5172a]::result::Result<(), rustc_errors[e9d593471e7e5a86]::ErrorGuaranteed>, rustc_interface[ee304f5e577cf6b9]::interface::create_compiler_and_run<core[f66f8263def5172a]::result::Result<(), rustc_errors[e9d593471e7e5a86]::ErrorGuaranteed>, rustc_driver[a243c3d9738e9cda]::run_compiler::{closure#1}>::{closure#1}>
  21:     0x7fce65bd3f24 - rustc_interface[ee304f5e577cf6b9]::interface::create_compiler_and_run::<core[f66f8263def5172a]::result::Result<(), rustc_errors[e9d593471e7e5a86]::ErrorGuaranteed>, rustc_driver[a243c3d9738e9cda]::run_compiler::{closure#1}>
  22:     0x7fce65bd1f42 - <scoped_tls[a76d38c46f15ed9e]::ScopedKey<rustc_span[1b916fa4cb305af0]::SessionGlobals>>::set::<rustc_interface[ee304f5e577cf6b9]::interface::run_compiler<core[f66f8263def5172a]::result::Result<(), rustc_errors[e9d593471e7e5a86]::ErrorGuaranteed>, rustc_driver[a243c3d9738e9cda]::run_compiler::{closure#1}>::{closure#0}, core[f66f8263def5172a]::result::Result<(), rustc_errors[e9d593471e7e5a86]::ErrorGuaranteed>>
  23:     0x7fce65bd021f - std[54a224735ab911a]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[ee304f5e577cf6b9]::util::run_in_thread_pool_with_globals<rustc_interface[ee304f5e577cf6b9]::interface::run_compiler<core[f66f8263def5172a]::result::Result<(), rustc_errors[e9d593471e7e5a86]::ErrorGuaranteed>, rustc_driver[a243c3d9738e9cda]::run_compiler::{closure#1}>::{closure#0}, core[f66f8263def5172a]::result::Result<(), rustc_errors[e9d593471e7e5a86]::ErrorGuaranteed>>::{closure#0}, core[f66f8263def5172a]::result::Result<(), rustc_errors[e9d593471e7e5a86]::ErrorGuaranteed>>
  24:     0x7fce65bd0509 - <<std[54a224735ab911a]::thread::Builder>::spawn_unchecked_<rustc_interface[ee304f5e577cf6b9]::util::run_in_thread_pool_with_globals<rustc_interface[ee304f5e577cf6b9]::interface::run_compiler<core[f66f8263def5172a]::result::Result<(), rustc_errors[e9d593471e7e5a86]::ErrorGuaranteed>, rustc_driver[a243c3d9738e9cda]::run_compiler::{closure#1}>::{closure#0}, core[f66f8263def5172a]::result::Result<(), rustc_errors[e9d593471e7e5a86]::ErrorGuaranteed>>::{closure#0}, core[f66f8263def5172a]::result::Result<(), rustc_errors[e9d593471e7e5a86]::ErrorGuaranteed>>::{closure#1} as core[f66f8263def5172a]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  25:     0x7fce636128c3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hb7ce1f9a74daab59
                               at /rustc/c274e4969f058b1c644243181ece9f829efa7594/library/alloc/src/boxed.rs:1854:9
  26:     0x7fce636128c3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hc28d1f774d95b80d
                               at /rustc/c274e4969f058b1c644243181ece9f829efa7594/library/alloc/src/boxed.rs:1854:9
  27:     0x7fce636128c3 - std::sys::unix::thread::Thread::new::thread_start::h7c8916b17d3c6d45
                               at /rustc/c274e4969f058b1c644243181ece9f829efa7594/library/std/src/sys/unix/thread.rs:108:17
  28:     0x7fce63542609 - start_thread
  29:     0x7fce6345b163 - clone
  30:                0x0 - <unknown>

note: 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: rustc 1.61.0-nightly (c274e4969 2022-03-05) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type bin -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:
end of query stack
warning: `playground` (bin "playground") generated 2 warnings
error: could not compile `playground`; 2 warnings emitted

[compiler-errors]

This is due to an (almost) trivially unsatisfiable bound. Minimized:

pub fn clone(it: &mut ()) -> &mut ()
where
    for<'any> &'any mut (): Clone,
{
    it.clone()
}

[eignnx]

Played around a little and found that:

1. The same ICE is generated on version 1.59.0 stable.

2. If a 'static lifetime is used, no ICE is generated:
   https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=eba7813b633302c60221d58389a58468
   Instead you get this error (which seems to be correct):

Compiling playground v0.0.1 (/playground)
error[[E0277]](https://doc.rust-lang.org/stable/error-index.html#E0277): the trait bound `&'static mut (): Clone` is not satisfied
 [--> src/lib.rs:3:5
](https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=eba7813b633302c60221d58389a58468#)  |
3 |     &'static mut (): Clone,
  |     ^^^^^^^^^^^^^^^^^^^^^^ the trait `Clone` is not implemented for `&'static mut ()`
  |
  = help: see issue #48214

For more information about this error, try `rustc --explain E0277`.
error: could not compile `playground` due to previous error

[compiler-errors]

Gonna claim this because I've been thinking about it recently: #93008, https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/What.20to.20do.20with.20trivially-false.20trivial_bounds

@rustbot claim