Replace uses of `#[unsafe_destructor_blind_to_params]` with `#[may_dangle]`

CC #34761

14 files changed, 20 insertions, 29 deletions

diff --git a/src/liballoc/arc.rs b/src/liballoc/arc.rs
index 1cad8f7f407..393a6a315ca 100644
--- a/src/liballoc/arc.rs
+++ b/src/liballoc/arc.rs
@@ -706,7 +706,7 @@ impl<T: ?Sized> Arc<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> Drop for Arc<T> {
+unsafe impl<#[may_dangle] T: ?Sized> Drop for Arc<T> {
     /// Drops the `Arc`.
     ///
     /// This will decrement the strong reference count. If the strong reference
@@ -734,7 +734,6 @@ impl<T: ?Sized> Drop for Arc<T> {
     /// drop(foo);    // Doesn't print anything
     /// drop(foo2);   // Prints "dropped!"
     /// ```
-    #[unsafe_destructor_blind_to_params]
     #[inline]
     fn drop(&mut self) {
         // Because `fetch_sub` is already atomic, we do not need to synchronize
diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index f9dfdc0e075..3a487ca7b9d 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -79,9 +79,10 @@
 #![feature(const_fn)]
 #![feature(core_intrinsics)]
 #![feature(custom_attribute)]
-#![feature(dropck_parametricity)]
+#![feature(dropck_eyepatch)]
 #![cfg_attr(not(test), feature(exact_size_is_empty))]
 #![feature(fundamental)]
+#![feature(generic_param_attrs)]
 #![feature(lang_items)]
 #![feature(needs_allocator)]
 #![feature(optin_builtin_traits)]
diff --git a/src/liballoc/raw_vec.rs b/src/liballoc/raw_vec.rs
index f23ea0ea8bf..357a2724e00 100644
--- a/src/liballoc/raw_vec.rs
+++ b/src/liballoc/raw_vec.rs
@@ -539,8 +539,7 @@ impl<T> RawVec<T> {
     }
 }
 
-impl<T> Drop for RawVec<T> {
-    #[unsafe_destructor_blind_to_params]
+unsafe impl<#[may_dangle] T> Drop for RawVec<T> {
     /// Frees the memory owned by the RawVec *without* trying to Drop its contents.
     fn drop(&mut self) {
         let elem_size = mem::size_of::<T>();
diff --git a/src/liballoc/rc.rs b/src/liballoc/rc.rs
index 86f8c746646..010e378ef2f 100644
--- a/src/liballoc/rc.rs
+++ b/src/liballoc/rc.rs
@@ -644,7 +644,7 @@ impl<T: ?Sized> Deref for Rc<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> Drop for Rc<T> {
+unsafe impl<#[may_dangle] T: ?Sized> Drop for Rc<T> {
     /// Drops the `Rc`.
     ///
     /// This will decrement the strong reference count. If the strong reference
@@ -672,7 +672,6 @@ impl<T: ?Sized> Drop for Rc<T> {
     /// drop(foo);    // Doesn't print anything
     /// drop(foo2);   // Prints "dropped!"
     /// ```
-    #[unsafe_destructor_blind_to_params]
     fn drop(&mut self) {
         unsafe {
             let ptr = *self.ptr;
diff --git a/src/libarena/lib.rs b/src/libarena/lib.rs
index 6044bec2c5a..bf7333b4936 100644
--- a/src/libarena/lib.rs
+++ b/src/libarena/lib.rs
@@ -30,10 +30,10 @@
 
 #![feature(alloc)]
 #![feature(core_intrinsics)]
+#![feature(dropck_eyepatch)]
 #![feature(heap_api)]
-#![feature(heap_api)]
+#![feature(generic_param_attrs)]
 #![feature(staged_api)]
-#![feature(dropck_parametricity)]
 #![cfg_attr(test, feature(test))]
 
 #![allow(deprecated)]
@@ -258,8 +258,7 @@ impl<T> TypedArena<T> {
     }
 }
 
-impl<T> Drop for TypedArena<T> {
-    #[unsafe_destructor_blind_to_params]
+unsafe impl<#[may_dangle] T> Drop for TypedArena<T> {
     fn drop(&mut self) {
         unsafe {
             // Determine how much was filled.
diff --git a/src/libcollections/btree/map.rs b/src/libcollections/btree/map.rs
index 788236c24d0..98c71967f3c 100644
--- a/src/libcollections/btree/map.rs
+++ b/src/libcollections/btree/map.rs
@@ -137,8 +137,7 @@ pub struct BTreeMap<K, V> {
 }
 
 #[stable(feature = "btree_drop", since = "1.7.0")]
-impl<K, V> Drop for BTreeMap<K, V> {
-    #[unsafe_destructor_blind_to_params]
+unsafe impl<#[may_dangle] K, #[may_dangle] V> Drop for BTreeMap<K, V> {
     fn drop(&mut self) {
         unsafe {
             for _ in ptr::read(self).into_iter() {
diff --git a/src/libcollections/lib.rs b/src/libcollections/lib.rs
index 68b067012d3..9ca56d0aea6 100644
--- a/src/libcollections/lib.rs
+++ b/src/libcollections/lib.rs
@@ -35,10 +35,11 @@
 #![feature(box_syntax)]
 #![cfg_attr(not(test), feature(char_escape_debug))]
 #![feature(core_intrinsics)]
-#![feature(dropck_parametricity)]
+#![feature(dropck_eyepatch)]
 #![feature(exact_size_is_empty)]
 #![feature(fmt_internals)]
 #![feature(fused)]
+#![feature(generic_param_attrs)]
 #![feature(heap_api)]
 #![feature(inclusive_range)]
 #![feature(lang_items)]
diff --git a/src/libcollections/linked_list.rs b/src/libcollections/linked_list.rs
index 31085509088..7f913d4afe4 100644
--- a/src/libcollections/linked_list.rs
+++ b/src/libcollections/linked_list.rs
@@ -726,8 +726,7 @@ impl<T> LinkedList<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> Drop for LinkedList<T> {
-    #[unsafe_destructor_blind_to_params]
+unsafe impl<#[may_dangle] T> Drop for LinkedList<T> {
     fn drop(&mut self) {
         while let Some(_) = self.pop_front_node() {}
     }
diff --git a/src/libcollections/vec.rs b/src/libcollections/vec.rs
index f2ef54f6e56..48a432943d2 100644
--- a/src/libcollections/vec.rs
+++ b/src/libcollections/vec.rs
@@ -1763,8 +1763,7 @@ impl<T: Ord> Ord for Vec<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> Drop for Vec<T> {
-    #[unsafe_destructor_blind_to_params]
+unsafe impl<#[may_dangle] T> Drop for Vec<T> {
     fn drop(&mut self) {
         unsafe {
             // use drop for [T]
@@ -2033,8 +2032,7 @@ impl<T: Clone> Clone for IntoIter<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> Drop for IntoIter<T> {
-    #[unsafe_destructor_blind_to_params]
+unsafe impl<#[may_dangle] T> Drop for IntoIter<T> {
     fn drop(&mut self) {
         // destroy the remaining elements
         for _x in self.by_ref() {}
diff --git a/src/libcollections/vec_deque.rs b/src/libcollections/vec_deque.rs
index 67621b860bf..f3a95fa9291 100644
--- a/src/libcollections/vec_deque.rs
+++ b/src/libcollections/vec_deque.rs
@@ -69,8 +69,7 @@ impl<T: Clone> Clone for VecDeque<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> Drop for VecDeque<T> {
-    #[unsafe_destructor_blind_to_params]
+unsafe impl<#[may_dangle] T> Drop for VecDeque<T> {
     fn drop(&mut self) {
         let (front, back) = self.as_mut_slices();
         unsafe {
diff --git a/src/libstd/collections/hash/table.rs b/src/libstd/collections/hash/table.rs
index 2cd9362a657..1ab62130cd3 100644
--- a/src/libstd/collections/hash/table.rs
+++ b/src/libstd/collections/hash/table.rs
@@ -1061,8 +1061,7 @@ impl<K: Clone, V: Clone> Clone for RawTable<K, V> {
     }
 }
 
-impl<K, V> Drop for RawTable<K, V> {
-    #[unsafe_destructor_blind_to_params]
+unsafe impl<#[may_dangle] K, #[may_dangle] V> Drop for RawTable<K, V> {
     fn drop(&mut self) {
         if self.capacity == 0 {
             return;
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index fc5c6968544..3f1975525e4 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -250,13 +250,14 @@
 #![feature(const_fn)]
 #![feature(core_float)]
 #![feature(core_intrinsics)]
-#![feature(dropck_parametricity)]
+#![feature(dropck_eyepatch)]
 #![feature(exact_size_is_empty)]
 #![feature(float_extras)]
 #![feature(float_from_str_radix)]
 #![feature(fn_traits)]
 #![feature(fnbox)]
 #![feature(fused)]
+#![feature(generic_param_attrs)]
 #![feature(hashmap_hasher)]
 #![feature(heap_api)]
 #![feature(inclusive_range)]
diff --git a/src/libstd/sync/mutex.rs b/src/libstd/sync/mutex.rs
index f6dbe01d7bd..f8426e3b578 100644
--- a/src/libstd/sync/mutex.rs
+++ b/src/libstd/sync/mutex.rs
@@ -280,8 +280,7 @@ impl<T: ?Sized> Mutex<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> Drop for Mutex<T> {
-    #[unsafe_destructor_blind_to_params]
+unsafe impl<#[may_dangle] T: ?Sized> Drop for Mutex<T> {
     fn drop(&mut self) {
         // This is actually safe b/c we know that there is no further usage of
         // this mutex (it's up to the user to arrange for a mutex to get
diff --git a/src/libstd/sync/rwlock.rs b/src/libstd/sync/rwlock.rs
index 0a11c71706b..adbb98e4b1f 100644
--- a/src/libstd/sync/rwlock.rs
+++ b/src/libstd/sync/rwlock.rs
@@ -310,8 +310,7 @@ impl<T: ?Sized> RwLock<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> Drop for RwLock<T> {
-    #[unsafe_destructor_blind_to_params]
+unsafe impl<#[may_dangle] T: ?Sized> Drop for RwLock<T> {
     fn drop(&mut self) {
         // IMPORTANT: This code needs to be kept in sync with `RwLock::into_inner`.
         unsafe { self.inner.destroy() }