ICE: <type> was a subtype of <type> but now is not?

[OddCoincidence]

I got this pretty weird ICE while in the middle of a refactor.

\error[E0624]: method `count` is private
   --> vm/src/obj/objrange.rs:115:41
    |
115 |         "count" => context.new_rustfunc(PyRangeRef::count),
    |                                         ^^^^^^^^^^^^^^^^^

error: internal compiler error: src/librustc_typeck/check/mod.rs:5549: instantiate_value_path: (UFCS) pyobject::PyRef<obj::objrange::PyRange> was a subtype of pyobject::PyRef<obj::objlist::PyList> but now is not?
   --> vm/src/obj/objrange.rs:115:41
    |
115 |         "count" => context.new_rustfunc(PyRangeRef::count),
    |                                         ^^^^^^^^^^^^^^^^^

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:526:9
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:39
   1: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:70
   2: std::panicking::default_hook::{{closure}}
             at src/libstd/sys_common/backtrace.rs:58
             at src/libstd/panicking.rs:200
   3: std::panicking::default_hook
             at src/libstd/panicking.rs:215
   4: rustc::util::common::panic_hook
   5: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:482
   6: std::panicking::begin_panic
   7: rustc_errors::Handler::span_bug
   8: rustc::util::bug::opt_span_bug_fmt::{{closure}}
   9: rustc::ty::context::tls::with_opt::{{closure}}
  10: rustc::ty::context::tls::with_context_opt
  11: rustc::ty::context::tls::with_opt
  12: rustc::util::bug::opt_span_bug_fmt
  13: rustc::util::bug::span_bug_fmt
  14: rustc_typeck::check::FnCtxt::instantiate_value_path
  15: rustc_typeck::check::FnCtxt::check_expr_kind
  16: rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_needs
  17: rustc_typeck::check::FnCtxt::check_argument_types
  18: rustc_typeck::check::FnCtxt::check_method_argument_types
  19: rustc_typeck::check::FnCtxt::check_expr_kind
  20: rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_needs
  21: rustc_typeck::check::FnCtxt::check_argument_types
  22: rustc_typeck::check::FnCtxt::check_method_argument_types
  23: rustc_typeck::check::FnCtxt::check_expr_kind
  24: rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_needs
  25: rustc_typeck::check::FnCtxt::check_stmt
  26: rustc_typeck::check::FnCtxt::check_block_with_expected
  27: rustc_typeck::check::FnCtxt::check_expr_kind
  28: rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_needs
  29: rustc_typeck::check::FnCtxt::check_return_expr
  30: rustc_typeck::check::check_fn
  31: rustc::ty::context::GlobalCtxt::enter_local
  32: rustc_typeck::check::typeck_tables_of
  33: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::typeck_tables_of<'tcx>>::compute
  34: rustc::dep_graph::graph::DepGraph::with_task_impl
  35: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::try_get_with
  36: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::ensure_query
  37: rustc::session::Session::track_errors
  38: rustc_typeck::check::typeck_item_bodies
  39: rustc::ty::query::__query_compute::typeck_item_bodies
  40: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::typeck_item_bodies<'tcx>>::compute
  41: rustc::dep_graph::graph::DepGraph::with_task_impl
  42: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::try_get_with
  43: rustc::util::common::time
  44: rustc_typeck::check_crate
  45: <std::thread::local::LocalKey<T>>::with
  46: rustc::ty::context::TyCtxt::create_and_enter
  47: rustc_driver::driver::compile_input
  48: rustc_driver::run_compiler_with_pool
  49: <scoped_tls::ScopedKey<T>>::set
  50: rustc_driver::run_compiler
  51: <scoped_tls::ScopedKey<T>>::set
query stack during panic:
#0 [typeck_tables_of] processing `obj::objrange::init`
#1 [typeck_item_bodies] type-checking all item bodies
end of query stack
error: aborting due to 3 previous errors

I don't know how to turn this into a minimal example, so here's the offending code that reproduces this error: OddCoincidence/RustPython@836f267

[estebank]

What version of the compiler are you using?

[OddCoincidence]

$ rustc --version
rustc 1.33.0 (2aa4c46cf 2019-02-28)