[rustc.git] / compiler / rustc_error_codes / src / error_codes / E0533.md

An item which isn't a unit struct, a variant, nor a constant has been used as a
match pattern.

Erroneous code example:

```compile_fail,E0533
struct Tortoise;

impl Tortoise {
    fn turtle(&self) -> u32 { 0 }
}

match 0u32 {
    Tortoise::turtle => {} // Error!
    _ => {}
}
if let Tortoise::turtle = 0u32 {} // Same error!
```

If you want to match against a value returned by a method, you need to bind the
value first:

```
struct Tortoise;

impl Tortoise {
    fn turtle(&self) -> u32 { 0 }
}

match 0u32 {
    x if x == Tortoise.turtle() => {} // Bound into `x` then we compare it!
    _ => {}
}
```
Commit	Line	Data
60c5eb7d XL	1	An item which isn't a unit struct, a variant, nor a constant has been used as a
	2	match pattern.
	3
	4	Erroneous code example:
	5
	6	```compile_fail,E0533
	7	struct Tortoise;
	8
	9	impl Tortoise {
	10	fn turtle(&self) -> u32 { 0 }
	11	}
	12
	13	match 0u32 {
	14	Tortoise::turtle => {} // Error!
	15	_ => {}
	16	}
	17	if let Tortoise::turtle = 0u32 {} // Same error!
	18	```
	19
	20	If you want to match against a value returned by a method, you need to bind the
	21	value first:
	22
	23	```
	24	struct Tortoise;
	25
	26	impl Tortoise {
	27	fn turtle(&self) -> u32 { 0 }
	28	}
	29
	30	match 0u32 {
	31	x if x == Tortoise.turtle() => {} // Bound into `x` then we compare it!
	32	_ => {}
	33	}
	34	```