+ ### Error
+
+ # Is this value an error?
+ #
+ # assert "[]".to_json_value[0].is_error
+ # assert "[".to_json_value.is_error
+ # assert not "[]".to_json_value.is_error
+ fun is_error: Bool do return value isa Error
+
+ # Get this value as a `Error`.
+ #
+ # require: `self.is_error`
+ fun to_error: Error do return value.as(Error)
+
+ ### JsonParseError
+
+ # Is this value a parse error?
+ #
+ # assert "[".to_json_value.is_parse_error
+ # assert not "[]".to_json_value.is_parse_error
+ fun is_parse_error: Bool do return value isa JsonParseError
+
+ # Get this value as a `JsonParseError`.
+ #
+ # require: `self.is_parse_error`
+ fun to_parse_error: JsonParseError do return value.as(JsonParseError)
+
+ ### Children access
+