Chrome Version       : 49.0.2623.112 (Official Build) m (64-bit)
URLs (if applicable) :

What steps will reproduce the problem?
(1) Open the devtools
(2) Go to the console tab and type: 
(3) {a:1}),({b:2}

What is the expected result?
It should throw a syntax error


What happens instead?
It displays Object {b: 2}


Please provide any additional information below. Attach a screenshot if
possible.

I think it would make sense to try to first parse it by itself and see if it is a syntax error before doing the auto params, something as simple as Function(expression) should do the trick. Note that this will also solve for the problem of this input:

{let a = 4; console.log(a)}

So far the only way I've found to get around this is to do something like this:

/**/ {let a = 4; console.log(a)}