SERVER-49022 introduces the 'ErrorAnnotation' type, which is used to provide information about an operator for generating document validation errors such as the operator's name, how it was specified by the user, and the desired error generation behavior. Currently, these ErrorAnnotations are constructed at parse time within expression_parser.cpp so, suffice it to say, before the MatchExpression parser is removed (SERVER-49485), the construction of these ErrorAnnotations should be moved elsewhere (perhaps during the translation of CST to MatchExpression; SERVER-48790) so that error generation for document validation does not break.