[paulddraper]

TypeScript is perfectly this. (And other gradually typed solutions; TS is simply the most popular one.)

You have the madness of thousand of developers flinging code at the universe due to the easiness of browsers, JS, and npm.

This results in great speed, but not great quality.

When your project/company now wants quality, you keep your code but transition to types. (In OSS space, Angular and Yarn projects have both done JS => TS migrations of some form.)

[ashishb]

Afaik, typescript is pretty bad in terms of catching some basic errors. Types are not enforced. A caller can change sync function to async, breaking the functionality downstream.

[xzel]

You can decide if they're enforced or not. That is part of how it is gradual typing.

[paulddraper]

Yes gradually typed languages are usually looser/more flexible about static typing.

> A caller can change sync function to async, breaking the functionality downstream.

I think you mean callee?

Are you taking about using a returned result? Because most languages permit ignoring return values.

If you want to check out promise use, check out https://tsetse.info/must-use-promises

[ashishb]

Sorry, I did mean callee.

Consider

``` const myIntValue = f(); ```

This code will silently break when f changes from sync to async.

[bcherny]

Right, but there will be an error where you consume myIntValue:

  const myIntValue = f()
  
  // Error TS2365: Operator '+' cannot be applied to types 'Promise<number>' and '2'
  const myResult = myIntValue + 2
  
  async function f() {
    return 42
  }