srfi-11: Do not expose variables to later clauses

The current implementation of srfi-11s let-values allows later clauses
to access and modify variables bound in earlier clauses when the clause
is not a proper list.

* module/srfi/srfi-11.scm (let-values): Fix switched variable names.
* test-suite/tests/srfi-11.test (let-values): Add test checking that the
  variable cannot be changed in later clauses.

module/srfi/srfi-11.scm

@@ -91,7 +91,7 @@
                     (syntax (call-with-values (lambda () exp)
                               (lambda (new-tmp ...) inner))))))
                ((vars exp)
-                (with-syntax ((((new-tmp . new-var) ...)
+                (with-syntax ((((new-var . new-tmp) ...)
                                (let lp ((vars (syntax vars)))
                                  (syntax-case vars ()
                                    ((id . rest)

test-suite/tests/srfi-11.test

@@ -74,7 +74,14 @@
 	'(unbound-variable . ".*")
       (let-values (((x) (values 1))
 		   ((y) (values (1+ x))))
-	#f))))
+	#f))
+
+    (pass-if "first binding with rest invisible to second expr"
+      (let* ((a 1)
+             (b (let-values (((a . b) (values 2 3))
+                             (c (begin (set! a 9) 4)))
+                  (list a b c))))
+        (equal? (cons a b) '(9 2 (3) (4)))))))
 
 ;;
 ;; let*-values