fixed PR 8737

svn: r6596

collects/mzlib/private/contract.ss

@@ -174,7 +174,8 @@ improve method arity mismatch contract violation error messages?
              [(null? clauses) null]
              [else
               (let ([clause (car clauses)])
-                (syntax-case clause (struct rename)
+                ;; compare raw identifiers for `struct' and `rename' just like provide does
+                (syntax-case* clause (struct rename) (λ (x y) (eq? (syntax-e x) (syntax-e y))) 
                   [(rename this-name new-name contract)
                    (and (identifier? (syntax this-name))
                         (identifier? (syntax new-name)))

collects/tests/mzscheme/contract-test.ss

@@ -5088,6 +5088,18 @@ so that propagation occurs.
       (eval 'pc19-ans))
    1)
 
+  ;; test that unit & contract don't collide over the name `struct'
+  (test/spec-passed
+   'provide/contract20
+   '(eval '(module tmp mzscheme
+             (require (lib "contract.ss")
+                      (lib "unit.ss"))
+             
+             (define-struct s (a b))
+             
+             (provide/contract
+              [struct s ([a number?]
+                         [b symbol?])]))))
   
   (contract-error-test
    #'(begin