Fix handling of (or) in match.

svn: r13295

collects/scheme/match/parse-helper.ss

@@ -177,9 +177,9 @@
     #f))
 
 ;; (listof pat) syntax -> void
+;; ps is never null
 ;; check that all the ps bind the same set of variables
-(define (all-vars ps stx)
-  (when (null? ps) (error 'bad))
+(define (all-vars ps stx)  
   (let* ([first-vars (bound-vars (car ps))]
          [l (length ps)]
          [ht (make-free-identifier-mapping)])

collects/scheme/match/parse-legacy.ss

@@ -25,8 +25,10 @@
       "This expander only works with the standard match syntax")]
     [(and p ...)
      (make-And (map parse (syntax->list #'(p ...))))]
-    [(or p ...)
-     (let ([ps (map parse (syntax->list #'(p ...)))])
+    [(or)
+     (make-Not (make-Dummy stx))]
+    [(or p ps ...)
+     (let ([ps (map parse (syntax->list #'(p ps ...)))])
        (all-vars ps stx)
        (make-Or ps))]
     [(not p ...)

collects/scheme/match/parse.ss

@@ -38,8 +38,10 @@
      (make-Var #'v)]
     [(and p ...)
      (make-And (map parse (syntax->list #'(p ...))))]
-    [(or p ...)
-     (let ([ps (map parse (syntax->list #'(p ...)))])
+    [(or)
+     (make-Not (make-Dummy stx))]
+    [(or p ps ...)
+     (let ([ps (map parse (syntax->list #'(p ps ...)))])
        (all-vars ps stx)
        (make-Or ps))]
     [(not p ...)

collects/tests/match/examples.ss

@@ -598,4 +598,9 @@
               [(? number?) (z)]))
           (lambda _ 12)))
 
+
+   (comp 4
+	 (match 3
+	  [(or) 1]
+	  [_ 4]))
    ))