[rustc.git] / src / doc / reference / src / types / never.md

# Never type

> **<sup>Syntax</sup>**\
> _NeverType_ : `!`

The never type `!` is a type with no values, representing the result of
computations that never complete. Expressions of type `!` can be coerced into
any other type.

```rust,should_panic
#![feature(never_type)]
let x: ! = panic!();
// Can be coerced into any type.
let y: u32 = x;
```

**NB.** The never type was expected to be stabilized in 1.41, but due
to some last minute regressions detected the stabilization was
temporarily reverted. The `!` type can only appear in function return
types presently. See [the tracking
issue](https://github.com/rust-lang/rust/issues/35121) for more
details.
Commit	Line	Data
13cf67c4 XL	1	# Never type
	2
	3	> <sup>Syntax</sup>\
	4	> _NeverType_ : `!`
	5
	6	The never type `!` is a type with no values, representing the result of
	7	computations that never complete. Expressions of type `!` can be coerced into
	8	any other type.
60c5eb7d XL	9
	10	```rust,should_panic
	11	#![feature(never_type)]
	12	let x: ! = panic!();
	13	// Can be coerced into any type.
	14	let y: u32 = x;
	15	```
	16
	17	NB. The never type was expected to be stabilized in 1.41, but due
	18	to some last minute regressions detected the stabilization was
	19	temporarily reverted. The `!` type can only appear in function return
	20	types presently. See [the tracking
	21	issue](https://github.com/rust-lang/rust/issues/35121) for more
	22	details.