compiler crash on innocent-looking match

[idubrov]

the compiler unexpectedly panicked. this is a bug.

I tried this code (hyper = "0.11.9"):

extern crate hyper;

pub fn crash(mime: &hyper::mime::Mime) -> bool {
  match (mime.subtype(), mime.suffix()) {
    (_, Some(hyper::mime::JSON)) => true,
    (hyper::mime::JSON, None) => true,
    _ => false,
  }
}

I expected to see this happen: code compiles (two top branches are incompatible)

Instead, this happened: compiler crashed; re-ordering two top branches fixes the issue

Meta

rustc --version --verbose:

rustc 1.24.0-nightly (5165ee9e2 2017-12-22)
binary: rustc
commit-hash: 5165ee9e209e0e70d89946ccbb7e90b9c0c3a7ac
commit-date: 2017-12-22
host: x86_64-apple-darwin
release: 1.24.0-nightly
LLVM version: 4.0

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 1.24.0-nightly (5165ee9e2 2017-12-22) running on x86_64-apple-darwin

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

thread 'rustc' panicked at 'assertion failed: rows.iter().all(|r| r.len() == v.len())', src/librustc_const_eval/_match.rs:596:4
stack backtrace:
   0:        0x11385781b - std::sys::unix::backtrace::tracing::imp::unwind_backtrace::h6748dc16a2d8df2e
   1:        0x113866fae - std::sys_common::backtrace::print::hc1ecb1e5559e6c33
   2:        0x113861410 - std::panicking::default_hook::{{closure}}::hb04e69910a65792e
   3:        0x11386110a - std::panicking::default_hook::h1ca336fe29972357
   4:        0x113861876 - std::panicking::rust_panic_with_hook::h02eae9f31985336e
   5:        0x1116feba1 - std::panicking::begin_panic::h0170dac5d8645b28
   6:        0x1116f50fa - rustc_const_eval::_match::is_useful::h23e3cdc562cbb328
   7:        0x1116f62b2 - rustc_const_eval::_match::is_useful_specialized::h3f912ded1cb5a78e
   8:        0x1116e6b7c - <core::iter::Map<I, F> as core::iter::iterator::Iterator>::try_fold::h8379d8eb0a7a9f77
   9:        0x1116f5320 - rustc_const_eval::_match::is_useful::h23e3cdc562cbb328
  10:        0x1116f62b2 - rustc_const_eval::_match::is_useful_specialized::h3f912ded1cb5a78e
  11:        0x1116e6b7c - <core::iter::Map<I, F> as core::iter::iterator::Iterator>::try_fold::h8379d8eb0a7a9f77
  12:        0x1116f5320 - rustc_const_eval::_match::is_useful::h23e3cdc562cbb328
  13:        0x1116f62b2 - rustc_const_eval::_match::is_useful_specialized::h3f912ded1cb5a78e
  14:        0x1116e6b7c - <core::iter::Map<I, F> as core::iter::iterator::Iterator>::try_fold::h8379d8eb0a7a9f77
  15:        0x1116f5320 - rustc_const_eval::_match::is_useful::h23e3cdc562cbb328
  16:        0x1116fcc67 - rustc_const_eval::check_match::check_arms::hf0b2a24697c406ea
  17:        0x1116f4302 - rustc_const_eval::_match::MatchCheckCtxt::create_and_enter::h8ecb2ffcfac97c79
  18:        0x1116fc6f5 - <rustc_const_eval::check_match::MatchVisitor<'a, 'tcx> as rustc::hir::intravisit::Visitor<'tcx>>::visit_expr::h5dc4813f83674f01
  19:        0x1116fc4ee - <rustc_const_eval::check_match::MatchVisitor<'a, 'tcx> as rustc::hir::intravisit::Visitor<'tcx>>::visit_expr::h5dc4813f83674f01
  20:        0x1116fc860 - <rustc_const_eval::check_match::MatchVisitor<'a, 'tcx> as rustc::hir::intravisit::Visitor<'tcx>>::visit_body::h8627b10027254cdf
  21:        0x1116ff24d - rustc::session::Session::track_errors::he6d05d19e503027d
  22:        0x1116fc2a8 - rustc_const_eval::check_match::check_match::h581d60f966dd70ec
  23:        0x112015dee - rustc::dep_graph::graph::DepGraph::with_task_impl::he4debb199688f723
  24:        0x111d3054a - rustc_errors::Handler::track_diagnostics::he3d49a14b2f2a05b
  25:        0x111c209f0 - rustc::ty::maps::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::cycle_check::h3e96520081b37b2e
  26:        0x11208ad8e - rustc::ty::maps::<impl rustc::ty::maps::queries::check_match<'tcx>>::force::h9b0cabeb54488ef9
  27:        0x11208b46a - rustc::ty::maps::<impl rustc::ty::maps::queries::check_match<'tcx>>::try_get::h168429d15c730e8b
  28:        0x111ec85e0 - rustc::ty::maps::TyCtxtAt::check_match::h1e0137c83b27f485
  29:        0x111c721b3 - rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::check_match::h395b3ef7e5d51eb3
  30:        0x1116fc029 - rustc::hir::intravisit::Visitor::visit_nested_body::hc3711ac4cbc2ecf6
  31:        0x11170dedf - rustc::hir::Crate::visit_all_item_likes::hafcfad702b50d9ac
  32:        0x1116fc1cf - rustc_const_eval::check_match::check_crate::hfadb55aaa16d50c3
  33:        0x10d3ccbc6 - <std::thread::local::LocalKey<T>>::with::h0f69a10298329fdf
  34:        0x10d3cf7cc - <std::thread::local::LocalKey<T>>::with::hb51817b52c5d173a
  35:        0x10d41c95e - rustc::ty::context::TyCtxt::create_and_enter::h0fc228efc283eb64
  36:        0x10d396952 - rustc_driver::driver::compile_input::h82abb659e9ffafec
  37:        0x10d3f9d6d - rustc_driver::run_compiler::h4102658971d5220d
  38:        0x10d351d31 - std::sys_common::backtrace::__rust_begin_short_backtrace::ha73cd560ba1185a4
  39:        0x1138913ae - __rust_maybe_catch_panic
  40:        0x10d32b84d - <F as alloc::boxed::FnBox<A>>::call_box::h4a09b2de7d586e97
  41:        0x113850247 - std::sys_common::thread::start_thread::h4cededf2a7a0e7f8
  42:        0x11386a688 - std::sys::unix::thread::Thread::new::thread_start::hc0d8e233205f2988
  43:     0x7fff995e293a - _pthread_body
  44:     0x7fff995e2886 - _pthread_start

[idubrov]

Slightly simplified version (it's not valid Rust code -- not all patterns are covered -- but it crashes the compiler):

extern crate hyper;

use hyper::mime::Name;
use hyper::mime::JSON;

pub fn crash(subtype: Name, suffix: Option<Name>) -> bool {
  match (subtype, suffix) {
    (_, Some(_)) => true,
    (JSON, None) => true,
  }
}

Backtrace with debug logging from rustc (RUST_BACKTRACE=full RUST_LOG=rustc_const_eval):

TRACE:rustc_const_eval::eval: eval_const_expr_partial: expr(25: true)
TRACE:rustc_const_eval::eval: eval_const_expr_partial: expr(29: true)
DEBUG:rustc_const_eval::pattern: expr=expr(3890: Name{source: "json", insensitive: true,}) pat_ty=hyper::<unnamed>::Name<'static> pat_id=27
DEBUG:rustc_const_eval::pattern: expr=expr(3888: "json") pat_ty=&'static str pat_id=27
TRACE:rustc_const_eval::eval: eval_const_expr_partial: expr(3888: "json")
DEBUG:rustc_const_eval::pattern: expr=expr(3889: true) pat_ty=bool pat_id=27
TRACE:rustc_const_eval::eval: eval_const_expr_partial: expr(3889: true)
DEBUG:rustc_const_eval::_match: is_useful(
+
, [Pattern { ty: (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>), span: src/lib.rs:8:5: 8:17, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild } }, FieldPattern { field: field[1], pattern: Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } } }] } }])
DEBUG:rustc_const_eval::_match: is_useful_expand_first_col: pcx=PatternContext { ty: (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>), max_slice_length: 1 }, expanding Pattern { ty: (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>), span: src/lib.rs:8:5: 8:17, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild } }, FieldPattern { field: field[1], pattern: Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } } }] } }
DEBUG:rustc_const_eval::_match: is_useful - expanding constructors: [Single]
DEBUG:rustc_const_eval::_match: is_useful_specialized([Pattern { ty: (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>), span: src/lib.rs:8:5: 8:17, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild } }, FieldPattern { field: field[1], pattern: Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } } }] } }], Single, (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>))
DEBUG:rustc_const_eval::_match: constructor_sub_pattern_tys(Single, (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>))
DEBUG:rustc_const_eval::_match: patterns_for_variant([FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild } }, FieldPattern { field: field[1], pattern: Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } } }], [Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:1:1: 1:1, kind: Wild }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:1:1: 1:1, kind: Wild }]) = [Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } }]
DEBUG:rustc_const_eval::_match: specialize(Pattern { ty: (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>), span: src/lib.rs:8:5: 8:17, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild } }, FieldPattern { field: field[1], pattern: Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } } }] } }, [Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:1:1: 1:1, kind: Wild }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:1:1: 1:1, kind: Wild }]) = Some([Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } }])
DEBUG:rustc_const_eval::_match: is_useful(
+
, [Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } }])
DEBUG:rustc_const_eval::_match: is_useful_expand_first_col: pcx=PatternContext { ty: hyper::<unnamed>::Name<'<empty>>, max_slice_length: 1 }, expanding Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild }
DEBUG:rustc_const_eval::_match: is_useful - expanding wildcard
DEBUG:rustc_const_eval::_match: used_ctors = []
DEBUG:rustc_const_eval::_match: all_constructors(hyper::<unnamed>::Name<'<empty>>)
DEBUG:rustc_const_eval::_match: all_ctors = [Single]
DEBUG:rustc_const_eval::_match: missing_ctors=[Single] is_privately_empty=false is_declared_nonexhaustive=false
DEBUG:rustc_const_eval::_match: is_useful(
+
, [Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } }])
DEBUG:rustc_const_eval::_match: is_useful_expand_first_col: pcx=PatternContext { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, max_slice_length: 1 }, expanding Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } }
DEBUG:rustc_const_eval::_match: is_useful - expanding constructors: [Variant(DefId(2/1:12166 ~ core[1805]::option[0]::Option[0]::Some[0]))]
DEBUG:rustc_const_eval::_match: is_useful_specialized([Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } }], Variant(DefId(2/1:12166 ~ core[1805]::option[0]::Option[0]::Some[0])), std::option::Option<hyper::<unnamed>::Name<'<empty>>>)
DEBUG:rustc_const_eval::_match: constructor_sub_pattern_tys(Variant(DefId(2/1:12166 ~ core[1805]::option[0]::Option[0]::Some[0])), std::option::Option<hyper::<unnamed>::Name<'<empty>>>)
DEBUG:rustc_const_eval::_match: patterns_for_variant([FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }], [Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:1:1: 1:1, kind: Wild }]) = [Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild }]
DEBUG:rustc_const_eval::_match: specialize(Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } }, [Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:1:1: 1:1, kind: Wild }]) = Some([Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild }])
DEBUG:rustc_const_eval::_match: is_useful(
+
, [Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild }])
DEBUG:rustc_const_eval::_match: is_useful_expand_first_col: pcx=PatternContext { ty: hyper::<unnamed>::Name<'<empty>>, max_slice_length: 1 }, expanding Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild }
DEBUG:rustc_const_eval::_match: is_useful - expanding wildcard
DEBUG:rustc_const_eval::_match: used_ctors = []
DEBUG:rustc_const_eval::_match: all_constructors(hyper::<unnamed>::Name<'<empty>>)
DEBUG:rustc_const_eval::_match: all_ctors = [Single]
DEBUG:rustc_const_eval::_match: missing_ctors=[Single] is_privately_empty=false is_declared_nonexhaustive=false
DEBUG:rustc_const_eval::_match: is_useful(
+
, [])
DEBUG:rustc_const_eval::_match: is_useful(
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ Pattern { ty: (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>), span: src/lib.rs:8:5: 8:17, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild } }, FieldPattern { field: field[1], pattern: Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } } }] } } +
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
, [Pattern { ty: (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>), span: src/lib.rs:9:5: 9:17, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'static>, span: src/lib.rs:9:6: 9:10, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } } }, FieldPattern { field: field[1], pattern: Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } } }] } } }, FieldPattern { field: field[1], pattern: Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:9:12: 9:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 0, subpatterns: [] } } }] } }])
DEBUG:rustc_const_eval::_match: is_useful_expand_first_col: pcx=PatternContext { ty: (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>), max_slice_length: 1 }, expanding Pattern { ty: (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>), span: src/lib.rs:9:5: 9:17, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'static>, span: src/lib.rs:9:6: 9:10, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } } }, FieldPattern { field: field[1], pattern: Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } } }] } } }, FieldPattern { field: field[1], pattern: Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:9:12: 9:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 0, subpatterns: [] } } }] } }
DEBUG:rustc_const_eval::_match: is_useful - expanding constructors: [Single]
DEBUG:rustc_const_eval::_match: is_useful_specialized([Pattern { ty: (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>), span: src/lib.rs:9:5: 9:17, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'static>, span: src/lib.rs:9:6: 9:10, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } } }, FieldPattern { field: field[1], pattern: Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } } }] } } }, FieldPattern { field: field[1], pattern: Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:9:12: 9:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 0, subpatterns: [] } } }] } }], Single, (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>))
DEBUG:rustc_const_eval::_match: constructor_sub_pattern_tys(Single, (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>))
DEBUG:rustc_const_eval::_match: patterns_for_variant([FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild } }, FieldPattern { field: field[1], pattern: Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } } }], [Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:1:1: 1:1, kind: Wild }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:1:1: 1:1, kind: Wild }]) = [Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } }]
DEBUG:rustc_const_eval::_match: specialize(Pattern { ty: (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>), span: src/lib.rs:8:5: 8:17, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild } }, FieldPattern { field: field[1], pattern: Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } } }] } }, [Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:1:1: 1:1, kind: Wild }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:1:1: 1:1, kind: Wild }]) = Some([Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } }])
DEBUG:rustc_const_eval::_match: patterns_for_variant([FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'static>, span: src/lib.rs:9:6: 9:10, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } } }, FieldPattern { field: field[1], pattern: Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } } }] } } }, FieldPattern { field: field[1], pattern: Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:9:12: 9:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 0, subpatterns: [] } } }], [Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:1:1: 1:1, kind: Wild }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:1:1: 1:1, kind: Wild }]) = [Pattern { ty: hyper::<unnamed>::Name<'static>, span: src/lib.rs:9:6: 9:10, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } } }, FieldPattern { field: field[1], pattern: Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } } }] } }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:9:12: 9:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 0, subpatterns: [] } }]
DEBUG:rustc_const_eval::_match: specialize(Pattern { ty: (hyper::<unnamed>::Name<'<empty>>, std::option::Option<hyper::<unnamed>::Name<'<empty>>>), span: src/lib.rs:9:5: 9:17, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'static>, span: src/lib.rs:9:6: 9:10, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } } }, FieldPattern { field: field[1], pattern: Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } } }] } } }, FieldPattern { field: field[1], pattern: Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:9:12: 9:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 0, subpatterns: [] } } }] } }, [Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:1:1: 1:1, kind: Wild }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:1:1: 1:1, kind: Wild }]) = Some([Pattern { ty: hyper::<unnamed>::Name<'static>, span: src/lib.rs:9:6: 9:10, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } } }, FieldPattern { field: field[1], pattern: Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } } }] } }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:9:12: 9:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 0, subpatterns: [] } }])
DEBUG:rustc_const_eval::_match: is_useful(
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild } + Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } } +
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
, [Pattern { ty: hyper::<unnamed>::Name<'static>, span: src/lib.rs:9:6: 9:10, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } } }, FieldPattern { field: field[1], pattern: Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } } }] } }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:9:12: 9:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 0, subpatterns: [] } }])
DEBUG:rustc_const_eval::_match: is_useful_expand_first_col: pcx=PatternContext { ty: hyper::<unnamed>::Name<'<empty>>, max_slice_length: 1 }, expanding Pattern { ty: hyper::<unnamed>::Name<'static>, span: src/lib.rs:9:6: 9:10, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } } }, FieldPattern { field: field[1], pattern: Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } } }] } }
DEBUG:rustc_const_eval::_match: is_useful - expanding constructors: [Single]
DEBUG:rustc_const_eval::_match: is_useful_specialized([Pattern { ty: hyper::<unnamed>::Name<'static>, span: src/lib.rs:9:6: 9:10, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } } }, FieldPattern { field: field[1], pattern: Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } } }] } }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:9:12: 9:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 0, subpatterns: [] } }], Single, hyper::<unnamed>::Name<'<empty>>)
DEBUG:rustc_const_eval::_match: constructor_sub_pattern_tys(Single, hyper::<unnamed>::Name<'<empty>>)
DEBUG:rustc_const_eval::_match: specialize(Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:6: 8:7, kind: Wild }, [Pattern { ty: (), span: src/lib.rs:1:1: 1:1, kind: Wild }, Pattern { ty: (), span: src/lib.rs:1:1: 1:1, kind: Wild }]) = Some([Pattern { ty: (), span: src/lib.rs:1:1: 1:1, kind: Wild }, Pattern { ty: (), span: src/lib.rs:1:1: 1:1, kind: Wild }])
DEBUG:rustc_const_eval::_match: patterns_for_variant([FieldPattern { field: field[0], pattern: Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } } }, FieldPattern { field: field[1], pattern: Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } } }], [Pattern { ty: (), span: src/lib.rs:1:1: 1:1, kind: Wild }, Pattern { ty: (), span: src/lib.rs:1:1: 1:1, kind: Wild }]) = [Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } }, Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } }]
DEBUG:rustc_const_eval::_match: specialize(Pattern { ty: hyper::<unnamed>::Name<'static>, span: src/lib.rs:9:6: 9:10, kind: Leaf { subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } } }, FieldPattern { field: field[1], pattern: Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } } }] } }, [Pattern { ty: (), span: src/lib.rs:1:1: 1:1, kind: Wild }, Pattern { ty: (), span: src/lib.rs:1:1: 1:1, kind: Wild }]) = Some([Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } }, Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } }])
DEBUG:rustc_const_eval::_match: is_useful(
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ Pattern { ty: (), span: src/lib.rs:1:1: 1:1, kind: Wild } + Pattern { ty: (), span: src/lib.rs:1:1: 1:1, kind: Wild } + Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } } +
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
, [Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } }, Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:9:12: 9:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 0, subpatterns: [] } }])
DEBUG:rustc_const_eval::_match: is_useful_expand_first_col: pcx=PatternContext { ty: (), max_slice_length: 1 }, expanding Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } }
DEBUG:rustc_const_eval::_match: is_useful - expanding constructors: [Single]
DEBUG:rustc_const_eval::_match: is_useful_specialized([Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } }, Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:9:12: 9:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 0, subpatterns: [] } }], Single, ())
DEBUG:rustc_const_eval::_match: constructor_sub_pattern_tys(Single, ())
DEBUG:rustc_const_eval::_match: specialize(Pattern { ty: (), span: src/lib.rs:1:1: 1:1, kind: Wild }, []) = Some([])
DEBUG:rustc_const_eval::_match: specialize(Pattern { ty: &'static str, span: src/lib.rs:9:6: 9:10, kind: Deref { subpattern: Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } } } }, []) = Some([Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } }])
DEBUG:rustc_const_eval::_match: is_useful(
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ Pattern { ty: (), span: src/lib.rs:1:1: 1:1, kind: Wild } + Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:8:9: 8:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 1, subpatterns: [FieldPattern { field: field[0], pattern: Pattern { ty: hyper::<unnamed>::Name<'<empty>>, span: src/lib.rs:8:14: 8:15, kind: Wild } }] } } +
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
, [Pattern { ty: str, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: &'static str, val: Str("json") } } }, Pattern { ty: bool, span: src/lib.rs:9:6: 9:10, kind: Constant { value: Const { ty: bool, val: Bool(true) } } }, Pattern { ty: std::option::Option<hyper::<unnamed>::Name<'<empty>>>, span: src/lib.rs:9:12: 9:16, kind: Variant { adt_def: std::option::Option, substs: Slice([hyper::<unnamed>::Name<'<empty>>]), variant_index: 0, subpatterns: [] } }])
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 1.24.0-dev running on x86_64-apple-darwin

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

thread 'rustc' panicked at 'assertion failed: rows.iter().all(|r| r.len() == v.len())', src/librustc_const_eval/_match.rs:596:4
stack backtrace:
   0:        0x10faf150b - std::sys::unix::backtrace::tracing::imp::unwind_backtrace::h75b9c1727f1ef869
   1:        0x10fae715b - std::sys_common::backtrace::print::h6c9dc2e8a46cfcb3
   2:        0x10faf7340 - std::panicking::default_hook::{{closure}}::h62969d07dd48231f
   3:        0x10faf703b - std::panicking::default_hook::hc7bb3cdedbae3f74
   4:        0x10faf7945 - std::panicking::rust_panic_with_hook::h796eb4b897c20bd9
   5:        0x10d5513e1 - std::panicking::begin_panic::hfdc17ff79f8f7e85
   6:        0x10d55f7ea - rustc_const_eval::_match::is_useful::h31020025e7ee4e84
   7:        0x10d560f24 - rustc_const_eval::_match::is_useful_specialized::h862dbc0f1cfee8ae
   8:        0x10d550f8c - <core::iter::Map<I, F> as core::iter::iterator::Iterator>::try_fold::hf5bef1a2e44f6bea
   9:        0x10d55fb9f - rustc_const_eval::_match::is_useful::h31020025e7ee4e84
  10:        0x10d560f24 - rustc_const_eval::_match::is_useful_specialized::h862dbc0f1cfee8ae
  11:        0x10d550f8c - <core::iter::Map<I, F> as core::iter::iterator::Iterator>::try_fold::hf5bef1a2e44f6bea
  12:        0x10d55fb9f - rustc_const_eval::_match::is_useful::h31020025e7ee4e84
  13:        0x10d560f24 - rustc_const_eval::_match::is_useful_specialized::h862dbc0f1cfee8ae
  14:        0x10d550f8c - <core::iter::Map<I, F> as core::iter::iterator::Iterator>::try_fold::hf5bef1a2e44f6bea
  15:        0x10d55fb9f - rustc_const_eval::_match::is_useful::h31020025e7ee4e84
  16:        0x10d568c35 - rustc_const_eval::check_match::check_arms::h55b7d80427a0d221
  17:        0x10d55d535 - rustc_const_eval::_match::MatchCheckCtxt::create_and_enter::h0683545c00eb0be9
  18:        0x10d5686a5 - <rustc_const_eval::check_match::MatchVisitor<'a, 'tcx> as rustc::hir::intravisit::Visitor<'tcx>>::visit_expr::h18950677cdbcad93
  19:        0x10d56848e - <rustc_const_eval::check_match::MatchVisitor<'a, 'tcx> as rustc::hir::intravisit::Visitor<'tcx>>::visit_expr::h18950677cdbcad93
  20:        0x10d568820 - <rustc_const_eval::check_match::MatchVisitor<'a, 'tcx> as rustc::hir::intravisit::Visitor<'tcx>>::visit_body::h200db49919baea77
  21:        0x10d570bcd - rustc::session::Session::track_errors::ha9bcb3c6cca859aa
  22:        0x10d5682a8 - rustc_const_eval::check_match::check_match::h5cae592ad199b4a6
  23:        0x10dffed66 - rustc::dep_graph::graph::DepGraph::with_task_impl::h2bc36caea8b204ce
  24:        0x10dcccc2a - rustc_errors::Handler::track_diagnostics::h55c906c2f86ddbe7
  25:        0x10dbd7d19 - rustc::ty::maps::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::cycle_check::h83a7504f84ac4116
  26:        0x10e0d3064 - rustc::ty::maps::<impl rustc::ty::maps::queries::check_match<'tcx>>::force::hb1a2f35449b34af0
  27:        0x10e0d3aac - rustc::ty::maps::<impl rustc::ty::maps::queries::check_match<'tcx>>::try_get::h5f69492c7f6191be
  28:        0x10dec8a10 - rustc::ty::maps::TyCtxtAt::check_match::h6e312737ad3b3f98
  29:        0x10dc2a733 - rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::check_match::hf3b2ac7af11fe550
  30:        0x10d568029 - rustc::hir::intravisit::Visitor::visit_nested_body::h8f5d7c5d7808fe9e
  31:        0x10d57a016 - rustc::hir::Crate::visit_all_item_likes::hc291ce83d88cfc77
  32:        0x10d5681cf - rustc_const_eval::check_match::check_crate::hcc976b79a9699624
  33:        0x1094bc9a1 - <std::thread::local::LocalKey<T>>::with::h9ba93edf630e5ba1
  34:        0x1094bd2fc - <std::thread::local::LocalKey<T>>::with::h9ff8e241f7614255
  35:        0x10950a48d - rustc::ty::context::TyCtxt::create_and_enter::hba5cc46e91825fe5
  36:        0x1094800fb - rustc_driver::driver::compile_input::h096e96e4036103a7
  37:        0x1094e85f8 - rustc_driver::run_compiler::h410671cff69818f3
  38:        0x10943b881 - std::sys_common::backtrace::__rust_begin_short_backtrace::h715b34804abd2a85
  39:        0x10fb2c35e - __rust_maybe_catch_panic
  40:        0x1094f3497 - std::panicking::try::h72a42d0775e3129a
  41:        0x1094156ba - <F as alloc::boxed::FnBox<A>>::call_box::h748044d708036f85
  42:        0x10fae9f17 - std::sys_common::thread::start_thread::hbccb1a1515a8b445
  43:        0x10fb08338 - std::sys::unix::thread::Thread::new::thread_start::ha9d840ea903629e8
  44:     0x7fff995e293a - _pthread_body
  45:     0x7fff995e2886 - _pthread_start

[arielb1]

Minified:

mod my_mod {
    #[derive(Clone, Copy, Eq, PartialEq, PartialOrd, Ord, Hash)]
    pub struct Name<'a> {
        source: &'a str,
    }

    pub const JSON: Name = Name { source: "JSON" };
}

pub fn crash() -> bool {
  match (my_mod::JSON, None) {
    (_, Some(my_mod::JSON)) => true,
    (my_mod::JSON, None) => true,
    _ => false,
  }
}

fn main() {}