test: Update and un-xfail compile-fail/tag-that-dare-not...

src/test/compile-fail/tag-that-dare-not-speak-its-name.rs

@@ -1,8 +1,13 @@
-// -*- rust -*-
-// xfail-test
-// error-pattern:option
-use std;
-import vec::*;
+// error-pattern:mismatched types: expected `char` but found
+// Issue #876
+
+#[no_core];
+
+use core;
+
+fn last<T: copy>(v: [const T]) -> core::option<T> {
+    fail;
+}
 
 fn main() {
     let y;