gap property
Gap says why the winning shape could not be fitted into an adoptable value, when it could not. It is separate from Refusal because they are different facts: a refusal means the ranking below proves nothing, a gap means the ranking stands and only the value is missing.
Please note: This property should have been non-nullable! Since the specification file does not include a default value (using the "default:" property), however, the generated source code must fall back to having a nullable type. Consider adding a "default:" property in the specification file to hide this note.
Implementation
String? gap;