RFC 2027: Add tests that feature gate properly gates

Author: bovinebuddha

src/test/ui/feature-gates/feature-gate-object_safe_for_dispatch.rs

@@ -0,0 +1,41 @@
+// Test that the use of the non object-safe trait objects
+// are gated by `object_safe_for_dispatch` feature gate.
+
+trait NonObjectSafe1: Sized {}
+
+trait NonObjectSafe2 {
+    fn static_fn() {}
+}
+
+trait NonObjectSafe3 {
+    fn foo<T>(&self);
+}
+
+trait NonObjectSafe4 {
+    fn foo(&self, &Self);
+}
+
+fn takes_non_object_safe_ref<T>(obj: &dyn NonObjectSafe1) {
+    //~^ ERROR E0038
+}
+
+fn return_non_object_safe_ref() -> &'static dyn NonObjectSafe2 {
+    //~^ ERROR E0038
+    loop {}
+}
+
+fn takes_non_object_safe_box(obj: Box<NonObjectSafe3>) {
+    //~^ ERROR E0038
+}
+
+fn return_non_object_safe_rc() -> std::rc::Rc<NonObjectSafe4> {
+    //~^ ERROR E0038
+    loop {}
+}
+
+trait Trait {}
+
+impl Trait for NonObjectSafe1 {}
+//~^ ERROR E0038
+
+fn main() {}

src/test/ui/feature-gates/feature-gate-object_safe_for_dispatch.stderr

@@ -0,0 +1,43 @@
+error[E0038]: the trait `NonObjectSafe1` cannot be made into an object
+  --> $DIR/feature-gate-object_safe_for_dispatch.rs:18:1
+   |
+LL | fn takes_non_object_safe_ref<T>(obj: &dyn NonObjectSafe1) {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `NonObjectSafe1` cannot be made into an object
+   |
+   = note: the trait cannot require that `Self : Sized`
+
+error[E0038]: the trait `NonObjectSafe2` cannot be made into an object
+  --> $DIR/feature-gate-object_safe_for_dispatch.rs:22:1
+   |
+LL | fn return_non_object_safe_ref() -> &'static dyn NonObjectSafe2 {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `NonObjectSafe2` cannot be made into an object
+   |
+   = note: method `static_fn` has no receiver
+
+error[E0038]: the trait `NonObjectSafe3` cannot be made into an object
+  --> $DIR/feature-gate-object_safe_for_dispatch.rs:27:1
+   |
+LL | fn takes_non_object_safe_box(obj: Box<NonObjectSafe3>) {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `NonObjectSafe3` cannot be made into an object
+   |
+   = note: method `foo` has generic type parameters
+
+error[E0038]: the trait `NonObjectSafe4` cannot be made into an object
+  --> $DIR/feature-gate-object_safe_for_dispatch.rs:31:1
+   |
+LL | fn return_non_object_safe_rc() -> std::rc::Rc<NonObjectSafe4> {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `NonObjectSafe4` cannot be made into an object
+   |
+   = note: method `foo` references the `Self` type in its arguments or return type
+
+error[E0038]: the trait `NonObjectSafe1` cannot be made into an object
+  --> $DIR/feature-gate-object_safe_for_dispatch.rs:38:6
+   |
+LL | impl Trait for NonObjectSafe1 {}
+   |      ^^^^^ the trait `NonObjectSafe1` cannot be made into an object
+   |
+   = note: the trait cannot require that `Self : Sized`
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0038`.