correct handling of different recursive postfix expressions,
to prevent previous regression of only allowing homogeneous
postfix recursion.

<<<

a[1][2][3]
a.b("hi")!?++--

>>>

(expr (subscript (expr (subscript (expr (subscript (expr (name a)) (expr 1))) (expr 2))) (expr 3)))
(expr (increment/decrement -- postfix (expr (increment/decrement ++ postfix (expr (try (expr (must (expr (call/construct (expr (member of (expr (name a)) named b)) (arg (expr "hi"))))))))))))