Imported array pointers may not be used directly, added an error message for this

phases/typecheck.ml

@@ -212,6 +212,12 @@ let rec typecheck node =
   | Const (FloatVal value, ann) ->
     Const (FloatVal value, Type Float :: ann)
 
+  (* Extern arrays variables are transformed to imported functions, so the
+   * pointer cannot be passed *)
+  | VarUse (GlobalDec (ArrayDims _, _, _), None, _) ->
+    raise (NodeError (node, "imported array pointers may only be \
+                             dereferenced, not used directly"))
+
   (* Variables inherit the type of their declaration *)
   | VarUse (dec, None, ann) ->
     VarUse (dec, None, Type (typeof dec) :: ann)

test/arrays/check_error/extern_array_arg.cvc

@@ -0,0 +1,8 @@
+extern int[n] arr;
+
+void foo(int[m] a) {}
+
+export int main() {
+    foo(arr);
+    return 0;
+}