nushell/crates/nu-parser/src
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
..
deparse.rs allow empty string arguments (#9420) 2023-06-13 07:30:30 -05:00
eval.rs Fix broken constants in scopes (#9679) 2023-07-14 00:02:05 +03:00
flatten.rs Avoid blocking when o+e> redirects too much stderr message (#8784) 2023-05-17 17:47:03 -05:00
known_external.rs Document and critically review ShellError variants - Ep. 3 (#8340) 2023-03-06 18:33:09 +01:00
lex.rs allow comment in multiple line pipeline (#9436) 2023-06-15 13:11:42 +02:00
lib.rs Add virtual path abstraction layer (#9245) 2023-05-23 23:48:50 +03:00
lite_parser.rs Let with pipeline (#9589) 2023-07-03 17:45:10 +12:00
parse_keywords.rs Custom command input/output types (#9690) 2023-07-15 09:51:28 +12:00
parse_patterns.rs add match guards (#9621) 2023-07-16 12:25:12 +12:00
parser_path.rs Add virtual path abstraction layer (#9245) 2023-05-23 23:48:50 +03:00
parser.rs add match guards (#9621) 2023-07-16 12:25:12 +12:00
type_check.rs Custom command input/output types (#9690) 2023-07-15 09:51:28 +12:00