Creates a class that is one of the supplied arguments. This function takes any number of objects, and returns the type that is the type-union of the singletons of those objects. For example, the expression
one-of(#"foo", #"bar", #"baz")
is equivalent to
type-union(singleton(#"foo"), singleton(#"bar"), singleton(#"baz"))
| #rest things | Instances of <object>. The allowable classes. |
| res | An instance of <type>. The resulting type from the supplied classes. |