Fixes tests

Upsilon/Binder/Binder.cs

@@ -277,8 +277,11 @@ namespace Upsilon.Binder
             {
                 var fullStopIndexExpression = (BoundFullStopIndexExpression) expression;
                 var indexerExpression = fullStopIndexExpression.Expression;
-                var indexerVariable = (TableVariableSymbol)ResolveVariable(indexerExpression);
-                return indexerVariable.Variables[fullStopIndexExpression.Index];
+                var indexerVariable = ResolveVariable(indexerExpression);
+                if (indexerVariable.Type == Type.Table)
+                {
+                    return ((TableVariableSymbol)indexerVariable).Variables[fullStopIndexExpression.Index];
+                }
             }
             return null;
         }

Upsilon/Binder/VariableSymbol.cs

@@ -63,4 +63,16 @@ namespace Upsilon.Binder
             Variables = variables;
         }
     }
+
+    public class UserDataVariableSymbol : VariableSymbol
+    {
+        public BoundTypeDefinition BoundTypeDefinition { get; }
+
+        public UserDataVariableSymbol(string name, bool local, BoundTypeDefinition boundTypeDefinition)
+            :base (name, Type.UserData, local)
+        {
+            BoundTypeDefinition = boundTypeDefinition;
+        }
+    }
+
 }