Generate Typescript Definitions from sanctuary-def declarations

[JAForbes]

This might be impossible, but I'd be willing to explore it if anyone else is interested.

If a definition was statically analysable (no dynamic generation of types), it should technically be possible to spit out a typescript <filename>.tsd definition file that matches the runtime definitions.

You'd get compile time and run time checking in tandem for free, and editor support.

The .tsd files would automatically be detected by typescript tooling (editors/command line tools) whenever that module is required/imported.

Something like:

const add = 
  $.def('add', {}, [$.Number, $.Number], (a,b) => a + b)

Might generate:

type add = (a : number, b: number ) : number

And something like:

const a = $.TypeVariable('a')
const SomeRecord = $.RecordType({ a: $.String , b: $.Function(a) })

Might generate

interface SomeRecord {
  a: string
  , b: (a: <T>) : T
}

The tool in question could bail out if the sanctuary definitions aren't statically analyzable, and suggest ways to make it analysable (using const for example).

As I said, this may be impossible, but I thought I'd at least suggest it. :)

[davidchambers]

This would be very cool indeed. It's somewhat related to #39.

[RichardForrester]

It seems that this has been done several times now, e.g., PropTypes, GraphQL.