Type Alias PropertiesOfType<O, V>

PropertiesOfType: keyof {
    [Property in keyof O as [V] extends [never]
        ? [NonNullable<O[Property]>] extends [never] ? Property : never
        : [NonNullable<O[Property]>] extends [never]
            ? never
            : NonNullable<O[Property]> extends V ? Property : never]: never
}

Returns the properties of object O with types that extend type V. Ignores undefined types.