error: internal compiler error: src/librustc_mir/borrow_check/universal_regions.rs:754: cannot convert ReEmpty(U0) to a region vid

[dpc]

Code

pub trait ResultExt {
    type Ok;
    fn err_eprint_and_ignore(self) -> Option<Self::Ok>;
}

impl<O, E> ResultExt for std::result::Result<O, E>
where
    E: std::error::Error,
{
    type Ok = O;
    fn err_eprint_and_ignore(self) -> Option<O>
    where
        Self: ,
    {
        match self {
            Err(e) => {
                eprintln!("{}", e);
                None
            }
            Ok(o) => Some(o),
        }
    }
}

Note: I've already spotted that where Self: , and after I've removed it, the ICE is gone.

Meta

The problem seems present on all stable, beta and nightly.

Error output

error: internal compiler error: src/librustc_mir/borrow_check/universal_regions.rs:754: cannot convert `ReEmpty(U0)` to a region vid

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:875:9
stack backtrace:
   Compiling crossbeam-deque v0.7.2
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/libunwind.rs:86
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:78
   3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
             at src/libstd/sys_common/backtrace.rs:59
   4: core::fmt::write
             at src/libcore/fmt/mod.rs:1063
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1426
   6: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:62
   7: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:49
   8: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:204
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:224
  10: rustc_driver::report_ice
  11: <alloc::boxed::Box<F> as core::ops::function::Fn<A>>::call
             at /rustc/8d69840ab92ea7f4d323420088dd8c9775f180cd/src/liballoc/boxed.rs:1031
  12: proc_macro::bridge::client::<impl proc_macro::bridge::Bridge>::enter::{{closure}}::{{closure}}
             at /rustc/8d69840ab92ea7f4d323420088dd8c9775f180cd/src/libproc_macro/bridge/client.rs:305
  13: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:474
  14: std::panicking::begin_panic
  15: rustc_errors::HandlerInner::bug
  16: rustc_errors::Handler::bug
  17: rustc::util::bug::opt_span_bug_fmt::{{closure}}
  18: rustc::ty::context::tls::with_opt::{{closure}}
  19: rustc::ty::context::tls::with_opt
  20: rustc::util::bug::opt_span_bug_fmt
  21: rustc::util::bug::bug_fmt
  22: rustc_mir::borrow_check::universal_regions::UniversalRegionIndices::to_region_vid::{{closure}}
  23: rustc_mir::borrow_check::universal_regions::UniversalRegionIndices::to_region_vid
  24: rustc_mir::borrow_check::region_infer::RegionInferenceContext::eval_verify_bound
  25: rustc_mir::borrow_check::region_infer::RegionInferenceContext::eval_verify_bound
  26: rustc_mir::borrow_check::region_infer::RegionInferenceContext::solve
  27: rustc_mir::borrow_check::nll::compute_regions
  28: rustc_mir::borrow_check::do_mir_borrowck
  29: rustc::ty::context::GlobalCtxt::enter_local
  30: rustc_mir::borrow_check::mir_borrowck
  31: rustc::ty::query::__query_compute::mir_borrowck
  32: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::mir_borrowck>::compute
  33: rustc::dep_graph::graph::DepGraph::with_task_impl
  34: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  35: rustc::ty::<impl rustc::ty::context::TyCtxt>::par_body_owners
  36: rustc_interface::passes::analysis
  37: rustc::ty::query::__query_compute::analysis
  38: rustc::dep_graph::graph::DepGraph::with_task_impl
  39: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  40: rustc::ty::context::tls::enter_global
  41: rustc_interface::interface::run_compiler_in_existing_thread_pool
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.43.1 (8d69840ab 2020-05-04) running on x86_64-unknown-linux-gnu

note: compiler flags: -C debuginfo=2 -C incremental --crate-type lib

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

query stack during panic:
#0 [mir_borrowck] borrow-checking `<std::result::Result<O, E> as result::ResultExt>::err_eprint_and_ignore`
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to previous error

error: could not compile `crev-common`.

To learn more, run the command again with --verbose.
warning: build failed, waiting for other jobs to finish...
error: build failed

[matthewjasper]

I can't reproduce this on rustc 1.45.0-nightly (a74d1862d 2020-05-14) nor on a dev build.