TypeErasedEncodable.swift

import Foundation

struct Property: Encodable {
    let name: String
    @AnyEncodable
    var value: Encodable
}

@propertyWrapper struct AnyEncodable: Encodable {
    let wrappedValue: Encodable

    func encode(to encoder: Encoder) throws {
        try wrappedValue.encode(to: encoder)
    }
}

let prop1 = Property(name: "int", value: 5)
let prop2 = Property(name: "string", value: "Hello!")
let prop3 = Property(name: "nestedArray", value: [prop1, prop2])
let prop4 = Property(name: "wtf", value: ["deep": prop3])

let jsonEncoder = JSONEncoder()

print(try String(data: jsonEncoder.encode(prop1), encoding: .utf8)!)
print(try String(data: jsonEncoder.encode(prop2), encoding: .utf8)!)
print(try String(data: jsonEncoder.encode(prop3), encoding: .utf8)!)
print(try String(data: jsonEncoder.encode(prop4), encoding: .utf8)!)

/*
Prints:

{"name":"int","value":5}
{"name":"string","value":"Hello!"}
{"name":"nestedArray","value":[{"name":"int","value":5},{"name":"string","value":"Hello!"}]}
{"name":"wtf","value":{"deep":{"name":"nestedArray","value":[{"name":"int","value":5},{"name":"string","value":"Hello!"}]}}}

*/