+(defparse skip-until (:context (context token-scanner-context)
+ (&key (keep-end nil keep-end-p))
+ &rest token-types)
+ "Discard tokens until we find one listed in TOKEN-TYPES.
+
+ If KEEP-END is true then retain the found token for later; otherwise
+ discard it. KEEP-END defaults to true if multiple TOKEN-TYPES are given;
+ otherwise false. If end-of-file is encountered then the indicator list is
+ simply the list of TOKEN-TYPES; otherwise the result is `nil'."
+ `(skip-until ,(parser-scanner context)
+ (list ,@token-types)
+ :keep-end ,(if keep-end-p keep-end
+ (> (length token-types) 1))))
+
+(defparse error (:context (context token-scanner-context)
+ (&key) sub &optional (recover t))
+ "Try to parse SUB; if it fails then report an error, and parse RECOVER.
+
+ This is the main way to recover from errors and continue parsing. Even
+ then, it's not especially brilliant.
+
+ If the SUB parser succeeds then just propagate its result: it's like we
+ were never here. Otherwise, try to recover in a sensible way so we can
+ continue parsing. The details of this recovery are subject to change, but
+ the final action is generally to invoke the RECOVER parser and return its
+ result."
+ `(parse-error-recover ,(parser-scanner context)
+ (parser () ,sub)
+ (parser () ,recover)))
+