[throwaway4good]

I put the parenthesis one step further to the right - so you would get:

   let y = f(()2, 3)

Which possibly wouldn't parse.

[juki]

That would depend on the language. Paredit is mainly made for Lisp where that would be legal (aside from the comma between 2 and 3). In some other languages that could also be allowed for casts.

[throwaway4good]

(It possibly wouldn't parse in a language with C-style syntax.)