[decomp] Split condition and body of until after building expressions (#768)

* improve until decomp

* fix tests

test/decompiler/reference/kernel/gcommon_REF.gc

@@ -171,13 +171,11 @@
   (let ((obj-type (-> obj type))
         (end-type object)
         )
-   (until (begin
-           (set! obj-type (-> obj-type parent))
-           (= obj-type end-type)
-           )
+   (until (= obj-type end-type)
     (if (= obj-type parent-type)
      (return #t)
      )
+    (set! obj-type (-> obj-type parent))
     )
    )
   #f
@@ -186,13 +184,11 @@
 ;; definition for function type-type?
 (defun type-type? ((child-type type) (parent-type type))
   (let ((end-type object))
-   (until (begin
-           (set! child-type (-> child-type parent))
-           (or (= child-type end-type) (zero? child-type))
-           )
+   (until (or (= child-type end-type) (zero? child-type))
     (if (= child-type parent-type)
      (return #t)
      )
+    (set! child-type (-> child-type parent))
     )
    )
   #f

test/decompiler/reference/kernel/gstring_REF.gc

@@ -356,15 +356,12 @@
   (let ((end-of-append (&-> (the-as (pointer uint8) append-str) 3)))
    (let ((location-of-char (string-skip-to-char (-> append-str data) char)))
     (when (= (-> location-of-char 0) char)
-     (until (begin
-             (set! end-of-append location-of-char)
-             (set!
-              location-of-char
-              (string-skip-to-char (&-> location-of-char 1) char)
-              )
-             (!= (-> location-of-char 0) char)
-             )
-      (empty)
+     (until (!= (-> location-of-char 0) char)
+      (set! end-of-append location-of-char)
+      (set!
+       location-of-char
+       (string-skip-to-char (&-> location-of-char 1) char)
+       )
       )
      )
     )