Type checking in JS about bosquelanguage

[mrkmarron]

Bosque is statically typed, with records, tuples, objects, union, and (limited) intersection types.

In Bosque the open record type {...} is a record with some number of properties with unknown names. We allow type checks and casts with the syntax:

function foo(arg: {...}): {f:Int, g:Int} | {f:String, g:Bool} | None {
    //check if arg is of type {f:Int, g:Int}
    if(arg->is[{f:Int, g:Int}](arg)) {
        return arg->as[{f:Int, g:Int}](); //cast to type
    }

    return arg->tryAs[{f:String, g:Bool}](); //try cast or return None if it fails
}

Currently we don't have a nice JSON interop story and I would like to do something here. From your comment I assume you are thinking something like:

function foo(data: String): {f: Int, g: Int} {
var check = JSON::is[{f: Int, g: Int}](data); //check if string is JSON format that is convertable to record type
if(check) {
    return JSON::parse[{f: Int, g: Int}](data); //parse the json string as the given record type
}
else {
    return none;
}

[chriskuech]

I suppose, though that looks pretty verbose. I'd rather just JSON::parse[{f: Int, g: Int}](data) throw an error/return an optional. If Bosque ever had an interop story with TypeScript or JS modules, the general case of converting an any or unknown type to a stronger type would be much more beneficial--I can't remember the last time I called JSON.parse directly.