Add a simple test case

src/test/ui/rfc-2632-const-trait-impl/const-drop.rs

@@ -0,0 +1,23 @@
+#![feature(const_trait_impl)]
+#![feature(const_fn_trait_bound)]
+#![feature(const_mut_refs)]
+#![feature(const_panic)]
+
+struct S;
+
+impl const Drop for S {
+    fn drop(&mut self) {
+        // NB: There is no way to tell that a const destructor is ran,
+        // because even if we can operate on mutable variables, it will
+        // not be reflected because everything is `const`. So we panic
+        // here, attempting to make the CTFE engine error.
+        panic!("much const drop")
+        //~^ ERROR evaluation of constant value failed
+    }
+}
+
+const fn a<T: ~const Drop>(_: T) {}
+
+const _: () = a(S);
+
+fn main() {}

src/test/ui/rfc-2632-const-trait-impl/const-drop.stderr

@@ -0,0 +1,25 @@
+error[E0080]: evaluation of constant value failed
+  --> $DIR/const-drop.rs:14:9
+   |
+LL |         panic!("much const drop")
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |         |
+   |         the evaluated program panicked at 'much const drop', $DIR/const-drop.rs:14:9
+   |         inside `<S as Drop>::drop` at $SRC_DIR/std/src/panic.rs:LL:COL
+...
+LL | const fn a<T: ~const Drop>(_: T) {}
+   |                                   - inside `a::<S>` at $DIR/const-drop.rs:19:35
+LL | 
+LL | const _: () = a(S);
+   |               ---- inside `_` at $DIR/const-drop.rs:21:15
+   |
+  ::: $SRC_DIR/core/src/ptr/mod.rs:LL:COL
+   |
+LL | pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T) {
+   | ------------------------------------------------------- inside `std::ptr::drop_in_place::<S> - shim(Some(S))` at $SRC_DIR/core/src/ptr/mod.rs:LL:COL
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0080`.