REPL Let doesn't type check definitions

[heades]

Consider the following example:

Grady> let x = triv 3
Grady> :d
["let x = triv (3)"]
Grady> :t x
NotArrowType Unit
Grady> 

However, the repl should never allow a definition that doesn't type check to be added to the queue.

[michaelto20]

fixed