Transpile into Babel/tcomb syntax

[jednano]

I know this is a stretch, but what if you could set a flag to transpile TS code into code that would be readable by babel-plugin-tcomb, which came out recently? This would enable runtime type checking, which I previously brought up in #1573, but it would require interfaces be transpiled into structs:

interface Point {
    x: number;
    y: number;
}

function foo(point: Point) {
    return point.x * point.y;
}

becomes...

import t from 'tcomb';

const Point = t.struct({
    x: t.Number,
    y: t.Number
});

function foo(point: Point) {
    return point.x * point.y;
}

If not provided directly by the compiler, the same could be achieved by a 3rd party module, if only a concrete syntax tree #625 were provided.

Related issues:

• Support Pluggable, 3rd-party Type Systems #2944
• Runtime type checking #1573
• Concrete Syntax Tree #625

[jednano]

For the record, I already have node modules that transpile from TS into ES6 and then Babel transpiles it from there and it works great! If only this last missing piece of the puzzle were implemented, we would have an awesome solution for both compile time and runtime type checking!

[mhegazy]

I think this is an interesting and useful proposition. I would say the best way this can be implemented is as an emitter extension; we first need to allow for an extension point in the emitter to allow for additional transformations. @rbuckton has a change to make this doable today: #4010 and some helper factory functions in #3762.

[DanielRosenwasser]

Related is #1573.

[mhegazy]

The TypeScript compiler should expose a transformation API that enable these scenarios. i do not think this belongs in the core though. We are working on enabling a plug-able emitter transformation system, so this, along with an extension should address the OP.