LOOP :INITIALLY clauses and scope of initializers
reported by Bruno Haible sbcl-devel "various SBCL bugs" from CLISP
test suite, originally by Thomas F. Burdick.
;; According to the HyperSpec 220.127.116.11.4, in for-as-equals-then, var is
;; initialized to the result of evaluating form1. 18.104.22.168 says that
;; initially clauses are evaluated in the loop prologue, which precedes all
;; loop code except for the initial settings provided by with, for, or as.
(loop :for x = 0 :then (1+ x)
:for y = (1+ x) :then (ash y 1)
:for z :across #(1 3 9 27 81 243)
:for w = (+ x y z)
:until (>= w 100) :collect w)
Expected: (2 6 15 38)