Required trait properties override inherited prototype properties with undefined about es-lab HOT 2 CLOSED

This issue was closed by revision r412.

The problem was due to the way Trait.create deals with required properties:

      if (pd.required) && !(name in proto)) {
          throw new Error('Missing required property: '+name);
      } else ...

In this case, properties present in 'proto' will not trigger an Error, but 
rather than skipping pd altogether, the 
code will continue in the else branch.

Changing the logic as follows fixes this problem:

      if (pd.required) {
        if (!(name in proto)) {
          throw new Error('Missing required property: '+name);
        }

Fixed in r412.