Updating lints page to reflect recent changes

src/doc/rustc/src/lints/index.md

@@ -39,19 +39,38 @@
 users some time to fix the code to accommodate the change. After some time,
 the warning may become an error.
 
-The following is an example of what a future-incompatible looks like:
+The following is an example of what future-incompatible code looks like:
+
+```rust,compile_fail
+#![allow(unused)]
+enum E {
+    A,
+}
+impl Drop for E {
+    fn drop(&mut self) {
+        println!("Drop");
+    }
+}
+
+#[allow(cenum_impl_drop_cast)]
+fn main() {
+    let e = E::A;
+    let i = e as u32;
+}
+```
+
+This will produce the following warning:
 
 ```text
-warning: borrow of packed field is unsafe and requires unsafe function or block (error E0133)
-  --> lint_example.rs:11:13
-   |
-11 |     let y = &x.data.0;
-   |             ^^^^^^^^^
-   |
-   = note: `#[warn(safe_packed_borrows)]` on by default
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #46043 <https://github.com/rust-lang/rust/issues/46043>
-   = note: fields of packed structs might be misaligned: dereferencing a misaligned pointer or even just creating a misaligned reference is undefined behavior
+> warning: cannot cast enum `E` into integer `u32` because it implements `Drop`
+>   --> src/main.rs:14:13
+>    |
+> 14 |     let i = e as u32;
+>    |             ^^^^^^^^
+>    |
+>    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+>    = note: for more information, see issue #73333 <https://github.com/rust-lang/rust/issues/73333>
+> 
 ```
 
 For more information about the process and policy of future-incompatible