[olliej]

haha, oh ASI - I was very confused by your example as I read this as if it was

  > const foo1 = function(a, b) { return a + b; }
  (2, 3)
  > console.log(foo1) // prints 5

  > const foo2 = (a, b) => { return a + b; }
  (2, 3)
  > console.log(foo2) // prints [Function: foo]

Even though it makes no sense for (2, 3) to be a result in those cases, that was just how I ended up reading it, and I was exceptionally confused about how the printed output could possibly happen.

A super nice example of how subtle differences can really change things though.

As a side note, ASI for JS is actually super easy to implement and the rules are actually really simple (leaving aside whether the feature itself is good :D ) as it's just "these specific statements can have a new line instead of a semicolon" - so in the parser instead of consume(semicolon) you can just do "semicolon or newline" (You can check the logic in JSC in https://github.com/WebKit/WebKit/blob/main/Source/JavaScript... - just look for autoSemicolon() or autoSemi() I can't recall off the top of my head)