Compile "docopt": thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value'

[HoKim98]

When compiling the programs with the crate "docopt" in nightly, I ended up with a rustc panic.

just within Cargo.toml,

[dependencies]
docopt = "1"

The panic looks like:

thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', src/librustc/hir/mod.rs:81:37
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/libunwind.rs:86
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-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:1069
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1427
   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:198
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:218
  10: rustc_driver::report_ice
  11: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:515
  12: rust_begin_unwind
             at src/libstd/panicking.rs:419
  13: core::panicking::panic_fmt
             at src/libcore/panicking.rs:111
  14: core::panicking::panic
             at src/libcore/panicking.rs:54
  15: core::ops::function::FnOnce::call_once
  16: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::hir_owner>::compute
  17: rustc::dep_graph::graph::DepGraph::with_task_impl
  18: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  19: rustc::hir::map::Map::get_entry
  20: rustc::hir::map::Map::find
  21: rustc_passes::dead::MarkSymbolVisitor::check_def_id
  22: rustc_hir::intravisit::walk_item
  23: rustc_passes::dead::check_crate
  24: rustc_session::utils::<impl rustc_session::session::Session>::time
  25: rustc_interface::passes::analysis::{{closure}}::{{closure}}
  26: rustc_session::utils::<impl rustc_session::session::Session>::time
  27: rustc_interface::passes::analysis
  28: rustc::ty::query::__query_compute::analysis
  29: rustc::dep_graph::graph::DepGraph::with_task_impl
  30: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  31: rustc::ty::context::tls::enter_global
  32: rustc_interface::interface::run_compiler_in_existing_thread_pool
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

error: internal compiler error: unexpected panic

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 1.44.0-nightly (7ceebd98c 2020-03-17) running on x86_64-unknown-linux-gnu

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

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

query stack during panic:
#0 [hir_owner] processing `regex`
#1 [analysis] running analysis passes on this crate
end of query stack
error: could not compile `docopt`.

This only happens on nightly, not on stable or beta.

[tesuji]

Dup of #70041