[rustc.git] / compiler / rustc_error_codes / src / error_codes / E0029.md

Something other than numbers and characters has been used for a range.

Erroneous code example:

```compile_fail,E0029
let string = "salutations !";

// The ordering relation for strings cannot be evaluated at compile time,
// so this doesn't work:
match string {
    "hello" ..= "world" => {}
    _ => {}
}

// This is a more general version, using a guard:
match string {
    s if s >= "hello" && s <= "world" => {}
    _ => {}
}
```

In a match expression, only numbers and characters can be matched against a
range. This is because the compiler checks that the range is non-empty at
compile-time, and is unable to evaluate arbitrary comparison functions. If you
want to capture values of an orderable type between two end-points, you can use
a guard.
Commit	Line	Data
60c5eb7d XL	1	Something other than numbers and characters has been used for a range.
	2
	3	Erroneous code example:
	4
	5	```compile_fail,E0029
	6	let string = "salutations !";
	7
	8	// The ordering relation for strings cannot be evaluated at compile time,
	9	// so this doesn't work:
	10	match string {
	11	"hello" ..= "world" => {}
	12	_ => {}
	13	}
	14
	15	// This is a more general version, using a guard:
	16	match string {
	17	s if s >= "hello" && s <= "world" => {}
	18	_ => {}
	19	}
	20	```
	21
	22	In a match expression, only numbers and characters can be matched against a
	23	range. This is because the compiler checks that the range is non-empty at
	24	compile-time, and is unable to evaluate arbitrary comparison functions. If you
	25	want to capture values of an orderable type between two end-points, you can use
	26	a guard.