ICE on the quicksilver library

[vorner]

Hello

I've hit an ICE on the quicksilver library when running clippy-nightly on it (version clippy 0.0.212 (fc5d0cc 2020-02-24)). It was first discovered by CI on my pull request (ryanisaacg/quicksilver#583) on MacOS, but I've reproduced it on Linux on master (commit f9c070e2a020f008f8ef10434da75a2e39535946) of the same repository. What I gather from these is:

• It's not platform specific.
• It's a relatively new regression on clippy (otherwise it wouldn't be possible to merge to master recently because of CI).
• (Unfortunately) it's not something I've introduced in the PR, so I don't know which part of the code triggers it.

$ cargo +nightly clippy
    Checking quicksilver v0.4.0-alpha0.2 (/home/vorner/prog/quicksilver)
error: internal compiler error: src/librustc_mir/dataflow/generic/engine.rs:315: Switch on discriminant of non-ADT

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:881:9
stack backtrace:
   0:     0x7fde1c3ac024 - backtrace::backtrace::libunwind::trace::hb827f4c466253f29
                               at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/libunwind.rs:86
   1:     0x7fde1c3ac024 - backtrace::backtrace::trace_unsynchronized::h9d5f4880ced35a0e
                               at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/mod.rs:66
   2:     0x7fde1c3ac024 - std::sys_common::backtrace::_print_fmt::hb1cddf0dbc858d5e
                               at src/libstd/sys_common/backtrace.rs:78
   3:     0x7fde1c3ac024 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h418b05c8466523f7
                               at src/libstd/sys_common/backtrace.rs:59
   4:     0x7fde1c3e52ac - core::fmt::write::hd7c4c3ef1c519f9c
                               at src/libcore/fmt/mod.rs:1053
   5:     0x7fde1c39dbf7 - std::io::Write::write_fmt::hea7ee7c2b0b56640
                               at src/libstd/io/mod.rs:1428
   6:     0x7fde1c3b0d15 - std::sys_common::backtrace::_print::hd48ee8e8dcfec814
                               at src/libstd/sys_common/backtrace.rs:62
   7:     0x7fde1c3b0d15 - std::sys_common::backtrace::print::hd560d375c3dd4d06
                               at src/libstd/sys_common/backtrace.rs:49
   8:     0x7fde1c3b0d15 - std::panicking::default_hook::{{closure}}::hbd5f2fc476d36ee7
                               at src/libstd/panicking.rs:204
   9:     0x7fde1c3b0a57 - std::panicking::default_hook::h04bf70bf3772f200
                               at src/libstd/panicking.rs:224
  10:     0x556f3eab1121 - clippy_driver::report_clippy_ice::h70f7057011ddbaa5
  11:     0x7fde1c3b1445 - std::panicking::rust_panic_with_hook::h98c3e5a93afaee15
                               at src/libstd/panicking.rs:474
  12:     0x7fde1f179ea3 - std::panicking::begin_panic::h58be6da30906897f
  13:     0x7fde1f1b5e80 - rustc_errors::HandlerInner::bug::h9a610a154219a6a0
  14:     0x7fde1f1b4ce0 - rustc_errors::Handler::bug::hb048846a869b0860
  15:     0x7fde1eea5fd9 - rustc::util::bug::opt_span_bug_fmt::{{closure}}::h0139aab91a8fd207
  16:     0x7fde1ee9f84b - rustc::ty::context::tls::with_opt::{{closure}}::hc44422f0c4b2e05d
  17:     0x7fde1ee9f7f2 - rustc::ty::context::tls::with_opt::h318453315d40d87e
  18:     0x7fde1eea5ee8 - rustc::util::bug::opt_span_bug_fmt::hb644edb52b614ddc
  19:     0x7fde1eea5e52 - rustc::util::bug::bug_fmt::ha9c9bce517bc984b
  20:     0x556f3ebc7ee4 - rustc_mir::dataflow::generic::engine::Engine<A>::iterate_to_fixpoint::h42e925aa7ac16cba
  21:     0x556f3eae2e0e - <clippy_lints::redundant_clone::RedundantClone as rustc_lint::passes::LateLintPass>::check_fn::h8a3a2b65a1044250
  22:     0x7fde1e557ea2 - <rustc_lint::late::LateLintPassObjects as rustc_lint::passes::LateLintPass>::check_fn::hbc95614e8c8705aa
  23:     0x7fde1cc22ad6 - <rustc_lint::late::LateContextAndPass<T> as rustc_hir::intravisit::Visitor>::visit_fn::hf388c68073d168ad
  24:     0x7fde1cbe5d6b - rustc_hir::intravisit::walk_expr::hc50689d3fbb81a55
  25:     0x7fde1cc2175d - <rustc_lint::late::LateContextAndPass<T> as rustc_hir::intravisit::Visitor>::visit_expr::h064f363b716a9170
  26:     0x7fde1cbe588f - rustc_hir::intravisit::walk_expr::hc50689d3fbb81a55
  27:     0x7fde1cc2175d - <rustc_lint::late::LateContextAndPass<T> as rustc_hir::intravisit::Visitor>::visit_expr::h064f363b716a9170
  28:     0x7fde1cbe3ea4 - rustc_hir::intravisit::walk_fn::hb1ab6a429c347b95
  29:     0x7fde1cc22b28 - <rustc_lint::late::LateContextAndPass<T> as rustc_hir::intravisit::Visitor>::visit_fn::hf388c68073d168ad
  30:     0x7fde1cbe151b - rustc_hir::intravisit::walk_impl_item::h694704945c920509
  31:     0x7fde1cc23d7a - rustc_hir::intravisit::Visitor::visit_nested_impl_item::h2c06a584ff95e81e
  32:     0x7fde1cbe7c60 - rustc_hir::intravisit::walk_item::hc287e2ca1d181213
  33:     0x7fde1cc236f0 - rustc_hir::intravisit::Visitor::visit_nested_item::hc262e27f3402b63a
  34:     0x7fde1cbe72fe - rustc_hir::intravisit::walk_item::hc287e2ca1d181213
  35:     0x7fde1cc236f0 - rustc_hir::intravisit::Visitor::visit_nested_item::hc262e27f3402b63a
  36:     0x7fde1cbe72fe - rustc_hir::intravisit::walk_item::hc287e2ca1d181213
  37:     0x7fde1cc236f0 - rustc_hir::intravisit::Visitor::visit_nested_item::hc262e27f3402b63a
  38:     0x7fde1cbe051e - rustc_hir::intravisit::walk_crate::he0129b4584847e5e
  39:     0x7fde1cbfc9fd - rustc_lint::late::late_lint_pass_crate::hf6c7eeacd17818aa
  40:     0x7fde1cbfebdb - rustc_session::utils::<impl rustc_session::session::Session>::time::h4489ea2fab066dd6
  41:     0x7fde1c3c3037 - __rust_maybe_catch_panic
                               at src/libpanic_unwind/lib.rs:86
  42:     0x7fde1cc4d4b3 - <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::hf801a16fdd1855fd
  43:     0x7fde1c3c3037 - __rust_maybe_catch_panic
                               at src/libpanic_unwind/lib.rs:86
  44:     0x7fde1cc024ea - rustc_session::utils::<impl rustc_session::session::Session>::time::hffe079e22d8b4c1f
  45:     0x7fde1cc914d6 - rustc_interface::passes::analysis::h63d05e45aafa63ee
  46:     0x7fde1ca16996 - rustc::ty::query::__query_compute::analysis::h60e0f763171ec6a8
  47:     0x7fde1ca80431 - rustc::dep_graph::graph::DepGraph::with_task_impl::hbc0032d204a86012
  48:     0x7fde1ca5785a - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query::hc8a26b5b4e3eb76d
  49:     0x7fde1ca8e737 - rustc::ty::context::tls::enter_global::h399f42f54f02e409
  50:     0x7fde1ca60544 - rustc_interface::interface::run_compiler_in_existing_thread_pool::hd42a83f4abcbfb40
  51:     0x7fde1ca0e53f - syntax::attr::with_globals::hd9a92937c7834975
  52:     0x7fde1ca12013 - std::sys_common::backtrace::__rust_begin_short_backtrace::h45dd6de2ed720c8b
  53:     0x7fde1c3c3037 - __rust_maybe_catch_panic
                               at src/libpanic_unwind/lib.rs:86
  54:     0x7fde1ca62686 - core::ops::function::FnOnce::call_once{{vtable.shim}}::hfcc630e86458e868
  55:     0x7fde1c38e1ff - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::ha0137aa2056446ec
                               at /rustc/0eb878d2aa6e3a1cb315f3f328681b26bb4bffdb/src/liballoc/boxed.rs:1017
  56:     0x7fde1c3c1940 - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::h335d32c504b6aa26
                               at /rustc/0eb878d2aa6e3a1cb315f3f328681b26bb4bffdb/src/liballoc/boxed.rs:1017
  57:     0x7fde1c3c1940 - std::sys_common::thread::start_thread::h6e1133a4f62ec9db
                               at src/libstd/sys_common/thread.rs:13
  58:     0x7fde1c3c1940 - std::sys::unix::thread::Thread::new::thread_start::h0a1909c3d640ef9b
                               at src/libstd/sys/unix/thread.rs:80
  59:     0x7fde1c2d82d7 - start_thread
                               at /var/tmp/portage/sys-libs/glibc-2.30-r4/work/glibc-2.30/nptl/pthread_create.c:479
  60:     0x7fde1c1e4d9f - clone
  61:                0x0 - <unknown>

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

note: we would appreciate a bug report: https://github.com/rust-lang/rust-clippy/issues/new

note: Clippy version: clippy 0.0.212 (fc5d0cc 2020-02-24)

query stack during panic:
#0 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to previous error

Is the repository this happens on + the full backtrace good enough so someone would know what happens, or should I try some more investigation (I might find some time to dig further, but I don't really know in which direction)?

[JohnTitor]

Duplicate of #5238
And fix is already submitted on rust-lang/rust, thanks!