Type Alias Usage 

pub type Usage = Ident<KnownUsage, u16>;

A Usage ID value.

Aliased Type

pub enum Usage {
    Known(KnownUsage),
    Reserved(u16),
}

Variants

Known(KnownUsage)

A well-known value.

Reserved(u16)

A reserved value.

This can be used to identify vendor-specific types.