Panic in match against non-unit variant as if it were unit variant

[estk]

First off, I would be interested in trying to fix this, seems simple enough. I figured I would start by filing a bug to document the issue and perhaps get some info on how best to fix this.

❯ rustc --version
rustc 1.33.0-nightly (4c2be9c97 2019-01-22)

The code:

pub enum SchemaBody {
    Group(Group),
    ...
}
impl CodeGenerator for SchemaBody {
    fn codegen(&self, ctx: &mut Context) -> TokenStream {
    match self {
        Self::Group => TokenStream::new(),
        ...
    }

The panic came from:

rust/src/librustc_typeck/check/_match.rs

Line 795 in 9323499

_ => bug!("unexpected pattern definition: {:?}", def)

The panic content:

warning: unused import: `std::str::FromStr`
 --> src/schema.rs:8:5
  |
8 | use std::str::FromStr;
  |     ^^^^^^^^^^^^^^^^^
  |
  = note: #[warn(unused_imports)] on by default

 INFO 2019-01-30T18:23:41Z: rustc::traits::fulfill: selecting trait `Binder(TraitPredicate(<proc_macro2::Ident as std::convert::AsRef<str>>))` at depth 0 yielded Err
error: internal compiler error: src/librustc_typeck/check/_match.rs:795: unexpected pattern definition: VariantCtor(DefId(0/1:1359 ~ xmlschemer[e672]::schema[0]::SchemaBody[0]::Group[0]), Fn)

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:589:9
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
   1: std::sys_common::backtrace::_print
   2: std::panicking::default_hook::{{closure}}
   3: std::panicking::default_hook
   4: rustc::util::common::panic_hook
   5: std::panicking::rust_panic_with_hook
   6: std::panicking::begin_panic
   7: rustc_errors::Handler::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::bug_fmt
  14: rustc_typeck::check::_match::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::check_pat_walk
  15: <core::iter::Map<I, F> as core::iter::iterator::Iterator>::fold
  16: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  17: rustc_typeck::check::_match::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::check_match
  18: rustc_typeck::check::FnCtxt::check_expr_kind
  19: rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_needs
  20: rustc_typeck::check::FnCtxt::check_decl_initializer
  21: rustc_typeck::check::FnCtxt::check_decl_local
  22: rustc_typeck::check::FnCtxt::check_stmt
  23: rustc_typeck::check::FnCtxt::check_block_with_expected
  24: rustc_typeck::check::FnCtxt::check_expr_kind
  25: rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_needs
  26: rustc_typeck::check::FnCtxt::check_return_expr
  27: rustc_typeck::check::check_fn
  28: rustc::ty::context::GlobalCtxt::enter_local
  29: rustc_typeck::check::typeck_tables_of
  30: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::typeck_tables_of<'tcx>>::compute
  31: rustc::dep_graph::graph::DepGraph::with_task_impl
  32: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::try_get_with
  33: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::ensure_query
  34: rustc::session::Session::track_errors
  35: rustc_typeck::check::typeck_item_bodies
  36: rustc::ty::query::__query_compute::typeck_item_bodies
  37: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::typeck_item_bodies<'tcx>>::compute
  38: rustc::dep_graph::graph::DepGraph::with_task_impl
  39: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::try_get_with
  40: rustc::util::common::time
  41: rustc_typeck::check_crate
  42: <std::thread::local::LocalKey<T>>::with
  43: rustc::ty::context::TyCtxt::create_and_enter
  44: rustc_driver::driver::compile_input
  45: <scoped_tls::ScopedKey<T>>::set
  46: rustc_driver::run_compiler
  47: <scoped_tls::ScopedKey<T>>::set
query stack during panic:
#0 [typeck_tables_of] processing `<schema::SchemaBody as schema::CodeGenerator>::codegen`
#1 [typeck_item_bodies] type-checking all item bodies
end of query stack
error: aborting due to previous error


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 1.33.0-nightly (4c2be9c97 2019-01-22) running on x86_64-apple-darwin

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

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

[2019-01-30T18:23:42Z INFO  cargo::core::compiler::job_queue] end: xmlschemer v0.1.0 (/Users/evan/rust/xmlschemer) => Target(lib)/Profile(dev) => Host
[2019-01-30T18:23:42Z DEBUG cargo] exit_with_error; err=CliError { error: Some(ProcessError { desc: "process didn\'t exit successfully: `rustc --edition=2018 --crate-name xmlschemer src/lib.rs --color always --crate-type lib --emit=dep-info,link -C debuginfo=2 -C metadata=9bdca844f3332aaa -C extra-filename=-9bdca844f3332aaa --out-dir /Users/evan/rust/xmlschemer/target/debug/deps -C incremental=/Users/evan/rust/xmlschemer/target/debug/incremental -L dependency=/Users/evan/rust/xmlschemer/target/debug/deps --extern clap=/Users/evan/rust/xmlschemer/target/debug/deps/libclap-a23f3ee74267101d.rlib --extern heck=/Users/evan/rust/xmlschemer/target/debug/deps/libheck-563b7994f02e64e3.rlib --extern if_chain=/Users/evan/rust/xmlschemer/target/debug/deps/libif_chain-6aadb789477ede7c.rlib --extern log=/Users/evan/rust/xmlschemer/target/debug/deps/liblog-45ef69e8215812e9.rlib --extern pretty_env_logger=/Users/evan/rust/xmlschemer/target/debug/deps/libpretty_env_logger-37685c937e93e60a.rlib --extern proc_macro2=/Users/evan/rust/xmlschemer/target/debug/deps/libproc_macro2-17e36e282c84be40.rlib --extern quote=/Users/evan/rust/xmlschemer/target/debug/deps/libquote-af4db6a3f849bcbe.rlib --extern rustfmt_nightly=/Users/evan/rust/xmlschemer/target/debug/deps/librustfmt_nightly-5cf5c0282729abd2.rlib --extern serde=/Users/evan/rust/xmlschemer/target/debug/deps/libserde-8e6194039e047282.rlib --extern serde_xml_rs=/Users/evan/rust/xmlschemer/target/debug/deps/libserde_xml_rs-f084d2902482aeaf.rlib --extern serde_derive=/Users/evan/rust/xmlschemer/target/debug/deps/libserde_derive-e37160e203f98c35.dylib --extern syn=/Users/evan/rust/xmlschemer/target/debug/deps/libsyn-2bf5c4461ccaa30c.rlib --extern xml=/Users/evan/rust/xmlschemer/target/debug/deps/libxml-b8b441b14c916eaf.rlib` (exit code: 101)", exit: Some(ExitStatus(ExitStatus(25856))), output: None }

stack backtrace:
   0: failure::backtrace::internal::InternalBacktrace::new::h474badb9ffce7bc7 (0x103b16f3b)
   1: <failure::backtrace::Backtrace as core::default::Default>::default::h45cb1f41e3daf8ec (0x103b17114)
   2: cargo::util::process_builder::ProcessBuilder::exec_with_streaming::h921b193535c0e9ef (0x1034fb6f5)
   3: <cargo::core::compiler::DefaultExecutor as cargo::core::compiler::Executor>::exec_and_capture_output::hf0dfafb1f405e584 (0x103732873)
   4: <F as cargo::core::compiler::job::FnBox<A, R>>::call_box::hd5b96495299b4cd2 (0x103730700)
   5: <F as cargo::core::compiler::job::FnBox<A, R>>::call_box::h05bcb4a6b3baee91 (0x103519d99)
   6: <F as cargo::core::compiler::job::FnBox<A, R>>::call_box::h05bcb4a6b3baee91 (0x103519d99)
   7: cargo::core::compiler::job::Job::run::h61355f8d9cb1d572 (0x103519e6e)
   8: crossbeam_utils::thread::ScopedThreadBuilder::spawn::{{closure}}::h8f338d85344a6ba7 (0x10374aed9)
   9: std::sys_common::backtrace::__rust_begin_short_backtrace::ha3ba31f6b7a9d297 (0x1034125fd)
  10: ___rust_maybe_catch_panic (0x103b3d7fe)
  11: <F as alloc::boxed::FnBox<A>>::call_box::hda9b9217608f805a (0x10341c889)
  12: std::sys::unix::thread::Thread::new::thread_start::h9fabc538beb0d7ac (0x103b3cdcb)
  13: __pthread_body (0x7fff78fc033c)
  14: __pthread_start (0x7fff78fc32a6)

stack backtrace:
   0: failure::backtrace::internal::InternalBacktrace::new::h474badb9ffce7bc7 (0x103b16f3b)
   1: <failure::backtrace::Backtrace as core::default::Default>::default::h45cb1f41e3daf8ec (0x103b17114)
   2: <F as cargo::core::compiler::job::FnBox<A, R>>::call_box::hd5b96495299b4cd2 (0x1037307a1)
   3: <F as cargo::core::compiler::job::FnBox<A, R>>::call_box::h05bcb4a6b3baee91 (0x103519d99)
   4: <F as cargo::core::compiler::job::FnBox<A, R>>::call_box::h05bcb4a6b3baee91 (0x103519d99)
   5: cargo::core::compiler::job::Job::run::h61355f8d9cb1d572 (0x103519e6e)
   6: crossbeam_utils::thread::ScopedThreadBuilder::spawn::{{closure}}::h8f338d85344a6ba7 (0x10374aed9)
   7: std::sys_common::backtrace::__rust_begin_short_backtrace::ha3ba31f6b7a9d297 (0x1034125fd)
   8: ___rust_maybe_catch_panic (0x103b3d7fe)
   9: <F as alloc::boxed::FnBox<A>>::call_box::hda9b9217608f805a (0x10341c889)
  10: std::sys::unix::thread::Thread::new::thread_start::h9fabc538beb0d7ac (0x103b3cdcb)
  11: __pthread_body (0x7fff78fc033c)
  12: __pthread_start (0x7fff78fc32a6)

[jonas-schievink]

Can you post the full code needed to reproduce this (or a minimal example)?

[estebank]

Repro:

#![feature(type_alias_enum_variants)]
pub enum Enum {
    A(usize),
}

impl Enum {
    fn foo(&self) -> () {
        match self {
            Self::A => (),
        }
    }
}

fn main() {}