add tests for the arbitrary_self_types, which won't pass yet

src/test/compile-fail/arbitrary-self-types-inherent-impl.rs

@@ -0,0 +1,11 @@
+#![feature(arbitrary_self_types)]
+
+use std::rc::Rc;
+
+struct Foo;
+
+impl Foo {
+    fn foo(self: Rc<Self>) {} //~ ERROR arbitrary self types are only allowed for trait methods
+}
+
+fn main() {}

src/test/compile-fail/arbitrary-self-types-not-object-safe.rs

@@ -0,0 +1,42 @@
+#![feature(arbitrary_self_types)]
+
+use std::rc::Rc;
+
+trait Foo {
+    fn foo(self: Rc<Self>) -> usize;
+}
+
+trait Bar {
+    fn foo(self: Rc<Self>) -> usize where Self: Sized;
+    fn bar(self: Box<Self>) -> usize;
+}
+
+impl Foo for usize {
+    fn foo(self: Rc<Self>) -> usize {
+        *self
+    }
+}
+
+impl Bar for usize {
+    fn foo(self: Rc<Self>) -> usize {
+        *self
+    }
+
+    fn bar(self: Box<Self>) -> usize {
+        *self
+    }
+}
+
+fn make_foo() {
+    let x = Box::new(5usize) as Box<Foo>;
+    //~^ ERROR E0038
+    //~| NOTE the method `foo` has an arbitrary self type
+    //~| NOTE the trait `Foo` cannot be made into an object
+}
+
+fn make_bar() {
+    let x = Box::new(5usize) as Box<Bar>;
+    x.bar();
+}
+
+fn main() {}

src/test/compile-fail/feature-gate-arbitrary-self-types.rs

@@ -0,0 +1,17 @@
+use std::rc::Rc;
+
+trait Foo {
+    fn foo(self: Rc<Box<Self>>); //~ ERROR arbitrary self types are unstable
+}
+
+struct Bar;
+
+impl Foo for Bar {
+    fn foo(self: Rc<Box<Self>>) {} //~ ERROR arbitrary self types are unstable
+}
+
+impl Bar {
+    fn bar(self: Box<Rc<Self>>) {} //~ ERROR arbitrary self types are unstable
+}
+
+fn main() {}