Evaluate level 1 expression
(fun x -> x + 6) (1 + 3)
Run binding time analysis on level 1 expression
(fun x -> (1:D + (((fun y -> 3 + y): S -> S) 5))) : D
Staging level 2 expression
fun x -> (1 lift + ((sfun y -> 3 s+ y) $ 5) lift)