correct error message and add to test

src/comp/middle/typeck.rs

@@ -621,7 +621,7 @@ fn compare_impl_method(tcx: ty::ctxt, sp: span, impl_m: ty::method,
                           "` has an incompatible set of type parameters");
         ty::mk_fn(tcx, impl_m.fty)
     } else if vec::len(impl_m.fty.inputs) != vec::len(if_m.fty.inputs) {
-        tcx.sess.span_err(sp,#fmt["method `%s`` has %u parameters \
+        tcx.sess.span_err(sp,#fmt["method `%s` has %u parameters \
                                    but the iface has %u",
                                   if_m.ident,
                                   vec::len(impl_m.fty.inputs),

src/test/compile-fail/iface-impl-different-num-params.rs

@@ -3,6 +3,7 @@ iface foo {
 }
 impl of foo for int {
     fn bar() -> int {
+        //!^ ERROR method `bar` has 0 parameters but the iface has 1
         self
     }
 }