runtime-contract.js

//

import * as t from "types";

// STATIC: any
// RUNTIME: string
const someInput /*: any*/ = "input";

// runtime contract for value
const SomeUnion = t.OR(t.String, t.Number);

// STATIC: string | number
// RUNTIME: string
const someValue = SomeUnion.ensure(someInput);

// STATIC: { type: string | number, validated: false, value: any }
// RUNTIME: { type: ['string', 'number'], validated: false, value: 'input' }
const someValueBox = SomeUnion.box(someInput);

// runtime contract for function
const SomeFn = t.fn([t.String], t.Void);

// STATIC: (a: string | Box<string>) => void
const someFnBox = SomeFn.box(str => console.log(str));

// STATIC: error
// RUNTIME: ok
someFnBox(someValue);
// log: "input"

// STATIC: error
// RUNTIME: ok
someFnBox(someValueBox);
// log: "input"

// RUNTIME: { type: ['string'], validated: true, value: 'input' }
someValueBox;