Use null for erased values to aid serialization

port/Data/IORef.newt

@@ -5,11 +5,11 @@ import Prelude
 -- We should test this at some point
 
 ptype IORef : U → U
-pfunc primNewIORef uses (MkIORes MkUnit) : ∀ a. a → IO (IORef a) := `(_, a) => (w) => MkIORes(undefined, [a], w)`
-pfunc primReadIORef uses (MkIORes MkUnit) : ∀ a. IORef a → IO a := `(_, ref) => (w) => MkIORes(undefined, ref[0], w)`
+pfunc primNewIORef uses (MkIORes MkUnit) : ∀ a. a → IO (IORef a) := `(_, a) => (w) => MkIORes(null, [a], w)`
+pfunc primReadIORef uses (MkIORes MkUnit) : ∀ a. IORef a → IO a := `(_, ref) => (w) => MkIORes(null, ref[0], w)`
 pfunc primWriteIORef uses (MkIORes MkUnit) : ∀ a. IORef a → a → IO Unit := `(_, ref, a) => (w) => {
   ref[0] = a
-  return MkIORes(undefined,MkUnit,w)
+  return MkIORes(null,MkUnit,w)
 }`
 
 newIORef : ∀ io a. {{HasIO io}} → a → io (IORef a)

port/Lib/Compile.newt

@@ -236,7 +236,7 @@ expToDoc (Apply x xs) = expToDoc x ++ text "(" ++ nest 2 (commaSep (map expToDoc
 expToDoc (Var nm) = jsIdent nm
 expToDoc (JLam nms (JReturn exp)) = text "(" <+> commaSep (map jsIdent nms) <+> text ") =>" <+> text "(" ++ expToDoc exp ++ text ")"
 expToDoc (JLam nms body) = text "(" <+> commaSep (map jsIdent nms) <+> text ") =>" <+> bracket "{" (stmtToDoc body) "}"
-expToDoc JUndefined = text "undefined"
+expToDoc JUndefined = text "null"
 expToDoc (Index obj ix) = expToDoc obj ++ text "(" ++ expToDoc ix ++ text " :: Nil)"
 expToDoc (Dot obj nm) = expToDoc obj ++ text "." ++ jsIdent nm
 

port/Node.newt

@@ -8,12 +8,12 @@ pfunc readFile uses (fs MkIORes Left Right) : (fn : String) -> IO (Either String
   let result
   try {
     let content = fs.readFileSync(fn, 'utf8')
-    result = Right(undefined, undefined, content)
+    result = Right(null, null, content)
   } catch (e) {
     let err = ""+e
-    result = Left(undefined, undefined, e)
+    result = Left(null, null, e)
   }
-  return MkIORes(undefined, result, w)
+  return MkIORes(null, result, w)
 }`
 
 -- I wonder if I should automatically `uses` the constructors in the types
@@ -21,12 +21,12 @@ pfunc writeFile uses (fs MkIORes MkUnit) : String → String → IO (Either Stri
   let result
   try {
     fs.writeFileSync(fn, content, 'utf8')
-    result = Right(undefined, undefined, MkUnit)
+    result = Right(null, null, MkUnit)
   } catch (e) {
       let err = ""+e
-      result = Left(undefined, undefined, e)
+      result = Left(null, null, e)
   }
-  return MkIORes(undefined, result, w)
+  return MkIORes(null, result, w)
 }`
 
 -- maybe System.exit or something, like the original putStrLn msg >> exitFailure