The runtime class field information.
The documentation of the field. This information is only available
if the compiler flag
-D use_rtti_doc was in place. Otherwise, or
if the field has no documentation, the value is
The line number where the field is defined. This information is only
available if the field has an expression.
Otherwise the value is
The list of available overloads for the fields or
null if no overloads
The type of the field.