X-Git-Url: https://git.distorted.org.uk/~mdw/sod/blobdiff_plain/239fa5bd3dff0b38b0cebdd3438311f21c24ba4f..7e94c5fe2eff01fe81fde1f54c53d3eefb254ba0:/src/lexer-impl.lisp

diff --git a/src/lexer-impl.lisp b/src/lexer-impl.lisp
index f474590..ba1f7c1 100644
--- a/src/lexer-impl.lisp
+++ b/src/lexer-impl.lisp
@@ -39,9 +39,6 @@
 ;;;--------------------------------------------------------------------------
 ;;; Indicators and error messages.
 
-(defvar *indicator-map* (make-hash-table)
-  "Hash table mapping indicator objects to human-readable descriptions.")
-
 (defun show-char (stream char &optional colonp atsignp)
   "Format CHAR to STREAM in a readable way.
 
@@ -52,6 +49,41 @@
 	 (format stream "`~C'" char))
 	(t (format stream "<~(~:C~)>" char))))
 
+(defun skip-until (scanner token-types &key keep-end)
+  "This is the implementation of the `skip-until' parser."
+  (do ((consumedp nil t))
+      ((member (token-type scanner) token-types)
+       (unless keep-end (scanner-step scanner))
+       (values nil t (or keep-end consumedp)))
+    (when (scanner-at-eof-p scanner)
+      (return (values token-types nil consumedp)))
+    (scanner-step scanner)))
+
+(defun parse-error-recover (scanner parser recover)
+  "This is the implementation of the `error' parser."
+  (multiple-value-bind (result win consumedp) (funcall parser)
+    (cond ((or win (and (not consumedp) (scanner-at-eof-p scanner)))
+	   ;; If we succeeded then there's nothing for us to do here.  On the
+	   ;; other hand, if we failed, didn't consume any tokens, and we're
+	   ;; at end-of-file, then there's not much hope of making onward
+	   ;; progress, so in this case we propagate the failure rather than
+	   ;; trying to recover.  And we assume that the continuation will
+	   ;; somehow arrange to report the problem, and avoid inundating the
+	   ;; user with error reports.
+	   (values result win consumedp))
+	  (t
+	   ;; Now we have to do some kind of sensible error recovery.  The
+	   ;; important thing to do here is to make sure that we make some
+	   ;; progress.  If we consumed any tokens then we're fine, and we'll
+	   ;; just try the provided recovery strategy.  Otherwise, if we're
+	   ;; not at EOF, then we can ensure progress by discarding the
+	   ;; current token.  Finally, if we are at EOF then our best bet is
+	   ;; simply to propagate the current failure back to the caller, but
+	   ;; we handled that case above.
+	   (syntax-error scanner result :continuep t)
+	   (unless consumedp (scanner-step scanner))
+	   (funcall recover)))))
+
 ;;;--------------------------------------------------------------------------
 ;;; Token scanning.