Support for MapKeys

[haejunejung]

It provides support for MapKeys.

Map is a key-value data structure commonly used for its efficiency, such as in hash maps. The MapKeys type is useful when you need to work with just the keys of a Map, allowing you to extract and use the key type independently from the value type.

type T0 = Map<string, string>;
type Expected = MapKeys<T0> // string

type T1 = Map<'0' | '1' | '2', string>;
type Expected = MapKeys<T1> // '0' | '1' | '2'

Here is a detailed implementation. playground