[format] allow identifier macro

format.rkt

@@ -40,11 +40,17 @@
                       (if t (quasisyntax/loc #'f (ann #,a #,t)) a))])
         (quasisyntax/loc #'f
           (format template #,@arg+*))))]
+   [f:id
+    (syntax/loc #'f format)]
    [(f tmp arg* ...)
     (syntax/loc #'f (format tmp arg* ...))]))
 
-(define-syntax-rule (printf: arg* ...)
+(define-syntax printf:
-  (display (format: arg* ...)))
+  (syntax-parser
+   [f:id
+    (syntax/loc #'f printf)]
+   [(f arg* ...)
+    (syntax/loc #'f (display (format: arg* ...)))]))
 
 ;; -----------------------------------------------------------------------------
 

test/format/pass.rkt

@@ -39,4 +39,16 @@
   (parameterize ([error-print-width 4])
     (test-format: ["~a ~.a" "hello" "world"] "hello w..."))
 
+  ;; Higher-order use: should work, but lose typechecking
+  (check-equal?
+    ((lambda ([f : (-> String Any String)] [x : Any]) (f "hello ~a" x))
+     format: 'world)
+    "hello world")
+
+  (check-exn exn:fail:contract?
+    (lambda ()
+      ((lambda ([f : (-> String Any Void)])
+         (f "~b" "not-a-number"))
+       printf:)))
+
 )