ZeroValue returns the equal zero value based on the input type.

FieldArg holds the data needed by the template engine to generate code based on the protogen.Field.

MessageArg holds the data needed by the template engine to generate code based on the protogen.Message.

MethodArg holds the data needed by the template engine to generate code based on the protogen.Method.

ServiceArg holds the data needed by the template engine to generate code based on the protogen.Service.