In Scheme mode @|| will also throw an error instead of being read as a

comment.  This is to avoid confusing situations like

  (define foo (list x '@|| y))

which quoted the `y' since @|| was read as a comment.

svn: r15789

collects/scribble/reader.ss

@@ -391,10 +391,12 @@
         (let*-values ([(line col pos) (port-next-location inp)]
                       [(xs) (get)])
           (cond [(not xs) xs]
-                [(null? xs) (make-special-comment #f)]
+                [(or (null? xs) (not (null? (cdr xs))))
-                [(null? (cdr xs)) (car xs)]
+                 (read-error line col pos
-                [else (read-error line col pos
+                             "a ~a|...| form in Scheme mode must have ~a"
-                                  "too many escape expressions")]))
+                             ch:command
+                             "exactly one escaped expression")]
+                [else (car xs)]))
         (get))))
 
   ;; called only when we must see a command in the input

collects/tests/scribble/reader.ss

@@ -636,6 +636,22 @@ bar}
 ---
 \foo{\" -\error-> #rx":1:6: read: expected a closing '\"'$"
 ---
+@|1 2|
+-@error->
+#rx"a @|...| form in Scheme mode must have exactly one escaped expression"
+---
+@||
+-@error->
+#rx"a @|...| form in Scheme mode must have exactly one escaped expression"
+---
+\|1 2|
+-\error->
+#rx"a \\\\|...| form in Scheme mode must have exactly one escaped expression"
+---
+\||
+-\error->
+#rx"a \\\\|...| form in Scheme mode must have exactly one escaped expression"
+---
 ;; -------------------- inside-reader
 ---
 foo bar baz  -@i->  "foo bar baz"