syntax/parse: fixed bugs (thanks samth)

Please propagate this to the release branch.

svn: r17756

collects/syntax/private/stxparse/rep.ss

@@ -973,7 +973,7 @@
   (define (check-sc-expr x)
     (syntax-case x ()
       [sc (identifier? #'sc) (list #'sc null)]
-      [(sc arg ...) (identifier? #'sc) (list #'sc #'(arg ...))]
+      [(sc arg ...) (identifier? #'sc) (list #'sc (syntax->list #'(arg ...)))]
       [_ (raise-syntax-error #f "expected syntax class use" ctx x)]))
   (syntax-case stx ()
     [(rx sc)

collects/syntax/scribblings/parse-patterns.scrbl

@@ -104,6 +104,7 @@ means specifically @tech{@Spattern}.
                  (~not S-pattern)
                  #((unsyntax @svar[pattern-part]) ...)
                  #s(prefab-struct-key (unsyntax @svar[pattern-part]) ...)
+                 #&@#,svar[S-pattern]
                  (~rest S-pattern)
                  (@#,ref[~describe s] expr S-pattern)
                  A-pattern]
@@ -515,6 +516,17 @@ key and whose sequence of fields, when considered as a list, match the
 ]
 }
 
+@specsubform[#&@#,svar[S-pattern]]{ 
+
+Matches a term that is a box whose contents matches the inner
+@tech{@Spattern}.
+
+@myexamples[
+(syntax-parse #'#&5
+  [#&n:nat 'ok])
+]
+}
+
 @specsubform[(#, @defhere[~rest] S-pattern)]{
 
 Matches just like @scheme[S-pattern]. The @scheme[~rest] pattern form

collects/tests/stxparse/stxclass.ss

@@ -182,13 +182,31 @@
 (syntax-parse #'(+) #:literals ([plus +])
   [(plus) (void)])
 
-(define-syntax-class (nat> n)
-  #:description (format "nat > ~s" n)
+(define-syntax-class (Nat> n)
+  #:description (format "Nat > ~s" n)
   (pattern x:nat #:fail-unless (> (syntax-e #'x) n) #f))
 (syntax-parse #'(1 2 3)
   [(a:nat b0:nat c0:nat)
    #:with b #'b0
-   #:declare b (nat> (syntax-e #'a))
+   #:declare b (Nat> (syntax-e #'a))
    #:with c #'c0
-   #:declare c (nat> (syntax-e #'b0))
+   #:declare c (Nat> (syntax-e #'b0))
    (void)])
+
+(define-syntax-class (nat> bound)
+  #:opaque
+  #:description (format "natural number greater than ~s" bound)
+  (pattern n:nat
+           #:when (> (syntax-e #'n) bound)))
+
+(define-conventions nat-convs
+  [N (nat> 0)])
+
+(syntax-parse #'(5 4) #:conventions (nat-convs)
+  [(N ...) (void)])
+
+(let/ec escape
+  (with-handlers ([exn? (compose escape void)])
+    (syntax-parse #'(4 -1) #:conventions (nat-convs)
+      [(N ...) (void)]))
+  (error 'test-conv1 "didn't work"))