Harlan Exception unfriendliness. ^^

[its2mc]

Hey it would be great if the exceptions had more clarity.

[eholk]

Here's the program that initially prompted this issue:

(module
  (define(main)
    (let (Y (vector 1 2 3 4))
      (println Y)
     (return 0))))

It says some stuff about reification and matching elements. The problem is the let binding needs an extra set of parentheses. We should add a more friendly error message in the lint pass.