pub const fn variant_count<T>() -> usize🔬This is a nightly-only experimental API. (
variant_count)Available on crate feature
mtls only.Expand description
Returns the number of variants in the enum type T.
If T is not an enum, calling this function will not result in undefined behavior, but the
return value is unspecified. Equally, if T is an enum with more variants than usize::MAX
the return value is unspecified. Uninhabited variants will be counted.
Note that an enum may be expanded with additional variants in the future
as a non-breaking change, for example if it is marked #[non_exhaustive],
which will change the result of this function.
§Examples
use std::mem;
enum Void {}
enum Foo { A(&'static str), B(i32), C(i32) }
assert_eq!(mem::variant_count::<Void>(), 0);
assert_eq!(mem::variant_count::<Foo>(), 3);
assert_eq!(mem::variant_count::<Option<!>>(), 2);
assert_eq!(mem::variant_count::<Result<!, !>>(), 2);