Improve consistence

Author: TimTheBig

library/alloc/src/collections/vec_deque/mod.rs

@@ -3044,6 +3044,7 @@ impl<T, A: Allocator> From<Vec<T, A>> for VecDeque<T, A> {
     /// [`Vec<T>`]: crate::vec::Vec
     /// [`VecDeque<T>`]: crate::collections::VecDeque
     ///
+    /// ## Cost
     /// This conversion is guaranteed to run in *O*(1) time
     /// and to not re-allocate the `Vec`'s buffer or allocate
     /// any additional memory.

library/core/src/ptr/non_null.rs

@@ -1652,6 +1652,7 @@ impl<T: ?Sized> hash::Hash for NonNull<T> {
 
 #[unstable(feature = "ptr_internals", issue = "none")]
 impl<T: ?Sized> From<Unique<T>> for NonNull<T> {
+    /// Return `Unique` casted to a `NonNull`.
     #[inline]
     fn from(unique: Unique<T>) -> Self {
         unique.as_non_null_ptr()

library/std/src/sync/mpsc.rs

@@ -1148,6 +1148,7 @@ impl<T> From<SendError<T>> for TrySendError<T> {
     ///
     /// This conversion always returns a `TrySendError::Disconnected` containing the data in the `SendError<T>`.
     ///
+    /// ## Cost
     /// No data is allocated on the heap.
     fn from(err: SendError<T>) -> TrySendError<T> {
         match err {
@@ -1198,6 +1199,7 @@ impl From<RecvError> for TryRecvError {
     ///
     /// This conversion always returns `TryRecvError::Disconnected`.
     ///
+    /// ## Cost
     /// No data is allocated on the heap.
     fn from(err: RecvError) -> TryRecvError {
         match err {
@@ -1233,6 +1235,7 @@ impl From<RecvError> for RecvTimeoutError {
     ///
     /// This conversion always returns `RecvTimeoutError::Disconnected`.
     ///
+    /// ## Cost
     /// No data is allocated on the heap.
     fn from(err: RecvError) -> RecvTimeoutError {
         match err {

library/std/src/sync/poison.rs

@@ -340,7 +340,7 @@ impl<T> PoisonError<T> {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> From<PoisonError<T>> for TryLockError<T> {
-    /// Wrap `PoisonError` in `Poisoned` variant.
+    /// Wrap `PoisonError` in the `Poisoned` variant.
     fn from(err: PoisonError<T>) -> TryLockError<T> {
         TryLockError::Poisoned(err)
     }