Type Alias IsOptionalKeyOf<Type, Key>

IsOptionalKeyOf: IsAny<Type | Key> extends true
    ? never
    : Key extends keyof Type
        ? Type extends Record<Key, Type[Key]> ? false : true
        : false

Returns a boolean for whether the given key is an optional key of the given type.

Copied from the IsOptionalKeyOf type in the type-fest package so that this package's public types do not depend on type-fest (see the note in type-checks.ts).