Support 'throw' expressions

Support proposal-throw-expressions.
That proposal is now stage-1, but worth to implements for convenience and this proposal not break backward-compatibilities.

Current

ts

const errorThrowExp = () => { throw new Error('Error!'); }
function errorThrowFn(maybeTrue) {
  if (maybeTrue){ 
    return ...;
  } else {
    throw new Error('Error!');
  }
}

js

const errorThrowExp = function() {throw new Error('Error!')}
function errorThrowFn(maybeTrue) {
  if (maybeTrue){ 
    return ...;
  } else {
    throw new Error('Error!');
  }
}

Proposal

ts

const errorThrower = () => throw new Error('Error!');
function errorThrowFn(maybeTrue: boolean) {
  return maybeTrue? ...: throw new Error('Error!');
}

js

const errorThrower = function() { throw new Error('Error!'); }
function errorThrowFn(maybeTrue: boolean) {
  return maybeTrue? ...: (function() { throw new Error('Error!') })();
}

[rbuckton]

https://github.com/Microsoft/TypeScript/tree/throwOperator?files=1

Currently it does not yet support unreachability checks at the expression level. Also, I am waiting for the next TC39 meeting to see if the proposal moves to Stage 2.

[DanielRosenwasser]

So is this proposal premature?

Nope, it’s fine to track it here. Like @kitsonk said, @rbuckton is championing it and is part of our team, but we will need it to reach a later stage before adopting it in TypeScript.

For what it’s worth, I’d be willing to bet he has a branch with an implementation of throw-expressions. 😄