+{- Cases to think about
+ (let x=y+1 in \x. (x,x))
+ --> let x=y+1 in (\x1. (x1,x1))
+ (\x. let x = y+1 in (x,x))
+ --> let x1 = y+1 in (\x. (x1,x1)
+ (let x=y+1 in (x,x), let x=y-1 in (x,x))
+ --> let x=y+1 in let x1=y-1 in ((x,x),(x1,x1))
+
+Watch out!
+ (let x=y+1 in let z=x+1 in (z,z)
+ --> matches (p,p) but watch out that the use of
+ x on z's rhs is OK!
+I'm removing the cloning because that makes the above case
+fail, because the inner let looks as if it has locally-bound vars -}
+