[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
  }