Stable ICE: &mut request::Request<'mw, B, D> was a subtype of &mut request::Request<'_, _, _> but now is not? #45855

error: internal compiler error: /checkout/src/librustc_typeck/check/method/confirm.rs:345: &mut request::Request<'mw, B, D> was a subtype of &mut request::Request<'_, _, _> but now is not?
  --> src/body_parser.rs:81:14
   |
81 |         self.get_ref::<FormBodyParser>().map_err(|e| (StatusCode::BadRequest, e))
   |              ^^^^^^^

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 1.21.0 (3b72af97e 2017-10-09) running on x86_64-unknown-linux-gnu

note: run with `RUST_BACKTRACE=1` for a backtrace

thread 'rustc' panicked at 'Box<Any>', /checkout/src/librustc_errors/lib.rs:437:8
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: std::sys::imp::backtrace::tracing::imp::unwind_backtrace
             at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at /checkout/src/libstd/sys_common/backtrace.rs:71
   2: std::panicking::default_hook::{{closure}}
             at /checkout/src/libstd/sys_common/backtrace.rs:60
             at /checkout/src/libstd/panicking.rs:381
   3: std::panicking::default_hook
             at /checkout/src/libstd/panicking.rs:391
   4: std::panicking::rust_panic_with_hook
             at /checkout/src/libstd/panicking.rs:611
   5: std::panicking::begin_panic
   6: rustc_errors::Handler::span_bug
   7: rustc::session::opt_span_bug_fmt::{{closure}}
   8: rustc::session::span_bug_fmt
   9: rustc_typeck::check::FnCtxt::check_method_call
  10: rustc_typeck::check::FnCtxt::check_expr_kind
  11: rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_lvalue_pref
  12: rustc_typeck::check::FnCtxt::check_method_call
  13: rustc_typeck::check::FnCtxt::check_expr_kind
  14: rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_lvalue_pref
  15: rustc_typeck::check::FnCtxt::check_block_with_expected::{{closure}}
  16: rustc_typeck::check::FnCtxt::check_block_with_expected
  17: rustc_typeck::check::FnCtxt::check_expr_kind
  18: rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_lvalue_pref
  19: rustc_typeck::check::FnCtxt::check_return_expr
  20: rustc_typeck::check::check_fn
  21: rustc_typeck::check::typeck_tables_of::{{closure}}
  22: rustc_typeck::check::typeck_tables_of
  23: rustc::dep_graph::graph::DepGraph::with_task
  24: rustc::ty::maps::<impl rustc::ty::maps::queries::typeck_tables_of<'tcx>>::try_get
  25: rustc::ty::maps::TyCtxtAt::typeck_tables_of
  26: rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::typeck_tables_of
  27: rustc_typeck::check::typeck_item_bodies
  28: rustc::dep_graph::graph::DepGraph::with_task
  29: rustc::ty::maps::<impl rustc::ty::maps::queries::typeck_item_bodies<'tcx>>::try_get
  30: rustc::ty::maps::TyCtxtAt::typeck_item_bodies
  31: rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::typeck_item_bodies
  32: rustc_typeck::check_crate
  33: rustc::ty::context::TyCtxt::create_and_enter
  34: rustc_driver::driver::compile_input
  35: rustc_driver::run_compiler