nushell/crates/nu-command/tests
mike 5bfec20244
add match guards (#9621)
## description

this pr adds [match
guards](https://doc.rust-lang.org/reference/expressions/match-expr.html#match-guards)
to match patterns
```nushell
match $x {
   _ if $x starts-with 'nu' => {},
   $x => {}
}
```

these work pretty much like rust's match guards, with few limitations:

1. multiple matches using the `|` are not (yet?) supported
 
```nushell
match $num {
    0 | _ if (is-odd $num) => {},
    _ => {}
}
```

2. blocks cannot be used as guards, (yet?)

```nushell
match $num {
    $x if { $x ** $x == inf } => {},
     _ => {}
}
```

## checklist
- [x] syntax
- [x] syntax highlighting[^1]
- [x] semantics
- [x] tests
- [x] clean up

[^1]: defered for another pr
2023-07-16 12:25:12 +12:00
..
commands add match guards (#9621) 2023-07-16 12:25:12 +12:00
format_conversions Input output checking (#9680) 2023-07-14 15:20:35 +12:00
main.rs Break up interdependencies of command crates (#9429) 2023-06-14 23:12:55 +02:00