liberalize un{quote,syntax}-spliciing to allow a non-list at the end of an enclosing list

svn: r8083

collects/scheme/private/qq-and-or.ss

@@ -275,9 +275,10 @@
 						(if (zero? level)
 						    (let-values
 							(((l) (normal l old-l)))
-						      (let-values
+                                                      (if (stx-null? l)
-							  ()
+                                                          uqsd
-							(list (quote-syntax qq-append) uqsd l)))
+                                                          (list (quote-syntax qq-append)
+                                                                uqsd l)))
 						    (let-values
 							(((restx) (qq-list rest (sub1 level))))
 						      (let-values

collects/scheme/private/qqstx.ss

@@ -66,6 +66,13 @@
 		     stx)]
 		   [((unsyntax-splicing x) . rest)
 		    (if (zero? depth)
+                        (if (stx-null? (syntax rest))
+                            (with-syntax ([temp (car (generate-temporaries '(uqs1)))])
+                              (convert-k (datum->syntax
+                                          stx
+                                          (syntax temp)
+                                          stx)
+                                         (list #'[temp x])))
                             (let ([rest-done-k
                                    (lambda (rest-v bindings)
                                      (with-syntax ([temp (car (generate-temporaries '(uqs)))]
@@ -81,7 +88,7 @@
                               (loop (syntax rest) depth
                                     (lambda ()
                                       (rest-done-k (syntax rest) null))
-				rest-done-k))
+                                    rest-done-k)))
 			(let ([mk-rest-done-k
 			       (lambda (x-v x-bindings)
 				 (lambda (rest-v rest-bindings)

collects/scribblings/gui/font-list-class.scrbl

@@ -33,7 +33,7 @@ Creates an empty font list.
                                    [underline any/c #f]
                                    [smoothing (one-of/c 'default 'partly-smoothed 'smoothed 'unsmoothed) 'default]
                                    [size-in-pixels? any/c #f])
-              void?])]{
+              (is-a?/c font%)])]{
 
 Finds an existing font in the list or creates a new one (that is
  automatically added to the list). The arguments are the same as for

collects/scribblings/reference/syntax.scrbl

@@ -1013,12 +1013,18 @@ and the result of the @scheme[_expr] takes the place of the
 @scheme[(unquote-splicing _expr)] similarly escapes, but the
 @scheme[_expr] must produce a list, and its elements are spliced as
 multiple values place of the @scheme[(unquote-splicing _expr)], which
-must appear as the @scheme[car] or a quoted pair.
+must appear as the @scheme[car] or a quoted pair; if the @scheme[cdr]
+of the relevant quoted pair is empty, then @scheme[_expr] need not
+produce a list, and its result is used directly in place of the quoted
+pair (in the same way that @scheme[append] accepts a non-list final
+argument).
 
 @examples[
 (eval:alts (#,(scheme quasiquote) (0 1 2)) `(0 1 2))
-(eval:alts (#,(scheme quasiquote) (0 (#,(scheme unquote) (+ 1 2)) 4)) `(1 ,(+ 1 2) 4))
+(eval:alts (#,(scheme quasiquote) (0 (#,(scheme unquote) (+ 1 2)) 4)) `(0 ,(+ 1 2) 4))
-(eval:alts (#,(scheme quasiquote) (0 (#,(scheme unquote-splicing) (list 1 2)) 4)) `(1 ,@(list 1 2) 4))
+(eval:alts (#,(scheme quasiquote) (0 (#,(scheme unquote-splicing) (list 1 2)) 4)) `(0 ,@(list 1 2) 4))
+(eval:alts (#,(scheme quasiquote) (0 (#,(scheme unquote-splicing) 1) 4)) `(0 ,@1 4))
+(eval:alts (#,(scheme quasiquote) (0 (#,(scheme unquote-splicing) 1))) `(0 ,@1))
 ]
 
 A @scheme[quasiquote], @scheme[unquote], or @scheme[unquote-splicing]

collects/tests/mzscheme/syntax.ss

@@ -663,7 +663,7 @@
 (syntax-test #'(unquote-splicing 7))
 
 (syntax-test #'`(1 . ,@5))
-(error-test #'`(1 ,@5))
+(test (cons 1 5) 'qq `(1 ,@5))
 (error-test #'`(1 ,@5 2))
 
 (define (qq-test e)