Forcing evaluation of some expressions to detect multiple uses of variable in while loops.

docs/Todo.md

@@ -3,7 +3,6 @@
 ## Critical Bugs
 * Ensure 'Array.pop-back' is memory safe and shrinks the array properly.
 * Can't define globals of with heap allocated types (String, structs, etc.)
-* Looping over a block of code where an external array is endo-map:ed over.
 * Arrays can contain references, this will lead to dangling pointers.
 
 ## Ugliness

examples/bugs.carp

@@ -1,2 +1,6 @@
 ;; This file contains examples of unsolved bugs
 
+(defn main []
+  (let [stuff [@"a" @"b" @"c"]]
+    (while true
+      (Array.delete stuff))))

src/ManageMemory.hs

@@ -144,12 +144,14 @@ manageMemory typeEnv globalEnv root =
                  manage body
                  postDeleters <- get
                  -- Visit an extra time to simulate repeated use
-                 _ <- visit expr
-                 _ <- visit body
+                 visitedExpr2 <- visit expr
+                 visitedBody2 <- visit body
                  let diff = postDeleters Set.\\ preDeleters
                  put (postDeleters Set.\\ diff) -- Same as just pre deleters, right?!
                  return $ do okExpr <- visitedExpr
                              okBody <- visitedBody
+                             okExpr2 <- visitedExpr2 -- This evaluates the second visit so that it actually produces the error
+                             okBody2 <- visitedBody2 -- And this one too. Laziness FTW.
                              let newInfo = setDeletersOnInfo i diff
                              return (XObj (Lst (whileExpr : okExpr : okBody : [])) newInfo t)