Adapt inplace collection leak test to check for no leaks

Author: SkiFire13

library/alloc/tests/vec.rs

@@ -1110,23 +1110,31 @@ fn test_from_iter_specialization_panic_during_iteration_drops() {
 }
 
 #[test]
-fn test_from_iter_specialization_panic_during_drop_leaks() {
-    static mut DROP_COUNTER: usize = 0;
+fn test_from_iter_specialization_panic_during_drop_doesnt_leak() {
+    static mut DROP_COUNTER_SHOULD_BE_DROPPED: usize = 0;
+    static mut DROP_COUNTER_DROPPED_TWICE: usize = 0;
 
     #[derive(Debug)]
     enum Droppable {
+        ShouldBeDropped,
         DroppedTwice(Box<i32>),
         PanicOnDrop,
     }
 
     impl Drop for Droppable {
         fn drop(&mut self) {
             match self {
+                Droppable::ShouldBeDropped => {
+                    unsafe {
+                        DROP_COUNTER_SHOULD_BE_DROPPED += 1;
+                    }
+                    println!("Dropping ShouldBeDropped!")
+                }
                 Droppable::DroppedTwice(_) => {
                     unsafe {
-                        DROP_COUNTER += 1;
+                        DROP_COUNTER_DROPPED_TWICE += 1;
                     }
-                    println!("Dropping!")
+                    println!("Dropping DroppedTwice!")
                 }
                 Droppable::PanicOnDrop => {
                     if !std::thread::panicking() {
@@ -1137,21 +1145,17 @@ fn test_from_iter_specialization_panic_during_drop_leaks() {
         }
     }
 
-    let mut to_free: *mut Droppable = core::ptr::null_mut();
-    let mut cap = 0;
-
     let _ = std::panic::catch_unwind(AssertUnwindSafe(|| {
-        let mut v = vec![Droppable::DroppedTwice(Box::new(123)), Droppable::PanicOnDrop];
-        to_free = v.as_mut_ptr();
-        cap = v.capacity();
-        let _ = v.into_iter().take(0).collect::<Vec<_>>();
+        let v = vec![
+            Droppable::ShouldBeDropped,
+            Droppable::DroppedTwice(Box::new(123)),
+            Droppable::PanicOnDrop,
+        ];
+        let _ = v.into_iter().take(1).collect::<Vec<_>>();
     }));
 
-    assert_eq!(unsafe { DROP_COUNTER }, 1);
-    // clean up the leak to keep miri happy
-    unsafe {
-        drop(Vec::from_raw_parts(to_free, 0, cap));
-    }
+    assert_eq!(unsafe { DROP_COUNTER_SHOULD_BE_DROPPED }, 1);
+    assert_eq!(unsafe { DROP_COUNTER_DROPPED_TWICE }, 1);
 }
 
 // regression test for issue #85322. Peekable previously implemented InPlaceIterable,