thread 'rustc' panicked at 'assertion failed: rows.iter().all(|r| r.len() == v.len())', src/librustc_mir_build/hair/pattern/_match.rs:LL:CC note: run with `RUST_BACKTRACE=1` environment variable to display a 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 VERSION running on TARGET note: compiler flags: FLAGS