Add test

src/test/compile-fail/dyn-trait-compatibility.rs

@@ -20,10 +20,5 @@ type A3 = dyn<<dyn as dyn>::dyn>;
 //~^ ERROR cannot find type `dyn` in this scope
 //~| ERROR cannot find type `dyn` in this scope
 //~| ERROR Use of undeclared type or module `dyn`
-type A4 = dyn(dyn, dyn) -> dyn;
-//~^ ERROR cannot find type `dyn` in this scope
-//~| ERROR cannot find type `dyn` in this scope
-//~| ERROR cannot find type `dyn` in this scope
-//~| ERROR cannot find type `dyn` in this scope
 
 fn main() {}

src/test/run-pass/dyn-trait.rs

@@ -17,6 +17,8 @@ static BYTE: u8 = 33;
 fn main() {
     let x: &(dyn 'static + Display) = &BYTE;
     let y: Box<dyn Display + 'static> = Box::new(BYTE);
+    let _: &dyn (Display) = &BYTE;
+    let _: &dyn (::std::fmt::Display) = &BYTE;
     let xstr = format!("{}", x);
     let ystr = format!("{}", y);
     assert_eq!(xstr, "33");