Issue To Be Solved

CompositeValue currently only supports stored fields.

Some built-in ("native") composite values have computed fields.

Add support for computed fields to CompositeValue, so it can be used to represent built-in values.

Suggested Solution

• Add a field computedFields to CompositeValue, which has an ordered map of string to func() Value entries
• On member access, also look up the requested member name in computedFields
• Tests