lua: if/else/elseif body scoping via (let () …); else-branch leak fixed +3 tests

lib/lua/transpile.sx

@@ -303,13 +303,18 @@
           rhs))
       (else (error "lua-transpile: bad assignment target")))))
 
+(define
+  lua-tx-if-body
+  (fn (body)
+    (list (make-symbol "let") (list) body)))
+
 (define
   lua-tx-if
   (fn
     (node)
     (let
       ((cnd (lua-tx (nth node 1)))
-        (then-body (lua-tx (nth node 2)))
+        (then-body (lua-tx-if-body (lua-tx (nth node 2))))
         (elseifs (nth node 3))
         (else-body (nth node 4)))
       (if
@@ -333,7 +338,7 @@
           clauses
           (append
             clauses
-            (list (list (make-symbol "else") (lua-tx else-body)))))))))
+            (list (list (make-symbol "else") (lua-tx-if-body (lua-tx else-body))))))))))
 
 (define
   lua-tx-elseif
@@ -341,7 +346,7 @@
     (pair)
     (list
       (list (make-symbol "lua-truthy?") (lua-tx (first pair)))
-      (lua-tx (nth pair 1)))))
+      (lua-tx-if-body (lua-tx (nth pair 1))))))
 
 (define
   lua-tx-while