diff --git a/collects/framework/specs.ss b/collects/framework/specs.ss
new file mode 100644
index 0000000..d01a313
--- /dev/null
+++ b/collects/framework/specs.ss
@@ -0,0 +1,100 @@
+(module tmp mzscheme
+  (provide m)
+  (define-syntax m
+    (lambda (stx)
+      (syntax-case stx ()
+	[(_)
+	 (let ([x 1])
+	   (syntax x))]))))
+
+(module tmp2 mzscheme
+  (require tmp)
+  (m))
+
+(exit)
+
+(module provide/type mzscheme
+  (provide provide/type)
+
+  (require-for-syntax (lib "stx.ss" "syntax"))
+
+  (define-syntax provide/type
+    (lambda (stx)
+      (syntax-case stx ()
+	[(_ module-name internal-name external-name type)
+	 (let ([raise-error
+		(lambda (fmt . args)
+		  (error 'provide/type
+			 (string-append
+			  (format "~e" (syntax->datum (syntax module-name)))
+			  (apply format fmt args))))])
+	   (with-syntax ([new-defn
+			  (let loop ([type (syntax type)]
+				     [name (syntax internal-name)])
+			    (syntax-case type (-> number union boolean interface)
+			      [(dom -> rng)
+			        (with-syntax ([in (gensym 'in)]
+					      [out (gensym 'out)])
+				  (with-syntax ([a-checker (loop (syntax dom)
+								 (syntax in))]
+						[b-checker (loop (syntax rng)
+								 (syntax out))]
+						[name name])
+				    (syntax
+				     (if (procedure? name)
+					 (lambda (in)
+					   (let ([out (name a-checker)])
+					     b-checker))
+					 (raise-error "expected a procedure, got: ~e" name)))))]
+			      [(interface i-e)
+			       (syntax
+				(let ([interface i-e])
+				  (if (is-a? name interface)
+				      name
+				      (raise-error "expected an instance of ~e, got: ~e" name interface))))]
+			      [number
+			       (with-syntax ([name name])
+				 (syntax
+				  (if (number? name)
+				      name
+				      (raise-error "expected a number, got: ~e" name))))]
+			      [boolean
+			       (with-syntax ([name name])
+				 (syntax
+				  (if (boolean? name)
+				      name
+				      (raise-error "expected a boolean, got: ~e" name))))]))])
+	     (syntax
+	      (begin (define external-name new-defn)
+		     (provide external-name)))))]))))
+
+(module a mzscheme
+  (require provide/type)
+
+  (define (in-f g) (g 0))
+  (provide/type a in-f f ((number -> number) -> number)))
+
+(module b mzscheme
+  (require provide/type)
+
+  (define (in-g x) (+ x 1))
+  (provide/type b in-g g (number -> boolean)))
+
+(module c mzscheme
+  (require a b)
+
+  (display (f g)) (newline))
+
+(require (lib "pretty.ss"))
+
+(pretty-print
+ (syntax->datum
+  (expand
+   (syntax
+     (module a mzscheme
+       (require tmp)
+
+       (define (in-f g)
+	 (display g) (newline)
+	 (g 0))
+       (provide/type in-f f ((number -> number) -> number)))))))