Add test for dyn alignment

Author: Jules-Bertholet

tests/ui/attributes/fn-align-dyn.rs

@@ -0,0 +1,15 @@
+//@ run-pass
+#![feature(fn_align)]
+
+trait Test {
+    #[align(4096)]
+    fn foo(&self);
+
+    #[align(4096)]
+    fn foo1(&self);
+}
+
+fn main() {
+    assert_eq!((<dyn Test>::foo as fn(_) as usize & !1) % 4096, 0);
+    assert_eq!((<dyn Test>::foo1 as fn(_) as usize & !1) % 4096, 0);
+}