Based on recently active topics such as Tuples conform to Equatable and Anonymous Structs, I'd like to throw my own pre-pitch onto the table as well: as struct syntax.
It's common for libraries to support functions that accept arbitrary dictionaries, one example being serializers:
func serialize(_ dictionary: [String: Any]) { ... } serialize( [ "name": "John Doe", "age": 40, "favoriteMeals": { "breakfast": "scrambled eggs", "lunch": "reuben", "dinner": "carbonara" } ] ) This approach has several problems:
- There's no clean way to enforce at compile-time that that the given dictionary is actually serializable. JSONSerialization performs this check at run-time, and
Encodablerequires employing type-erasure. - Similarly, this approach makes you prone to duplicate keys, something one would either have to explicitly check at run-time, or allow to pass through undetected.
With these issues in mind, I propose new syntactical sugar that enables a tuple declaration to be instantiated as an anonymous struct. For example:
let myValue = (foo: "bar", one: 1, true) as struct print(myValue.foo) // "bar" print(myValue.2) // "true" would desugar into
struct __some_struct { var foo: String var one: String var _2: Bool } let myValue = __some_struct(foo: "bar", one: 1, _2: true) print(myValue.foo) // "bar" print(myValue._2) // "true" This would also support limited protocol conformance, transforming the earlier example into something like:
func serialize<T: Encodable>(_ value: T) { ... } serialize( ( name: "John Doe", age: 40, favoriteMeals: ( breakfast: "scrambled eggs", lunch: "reuben", dinner: "carbonara" ) as Encodable struct ) as Encodable struct ) Clearly, this pitch is still quite rough, but I'd love to get feedback from folks here, especially on any language design shortcomings I'm likely missing.