Function discriminant_value
const fn discriminant_value<T>(v: &T) -> <T as DiscriminantKind>::Discriminant
Returns the value of the discriminant for the variant in 'v';
if T has no discriminant, returns 0.
Note that, unlike most intrinsics, this is safe to call;
it does not require an unsafe block.
Therefore, implementations must not require the user to uphold
any safety invariants.
The stabilized version of this intrinsic is core::mem::discriminant.