Document From impls for cow.rs

Author: fee1-dead

library/alloc/src/vec/cow.rs

@@ -5,20 +5,38 @@ use super::Vec;
 
 #[stable(feature = "cow_from_vec", since = "1.8.0")]
 impl<'a, T: Clone> From<&'a [T]> for Cow<'a, [T]> {
+    /// Creates a [`Borrowed`] variant of [`Cow`]
+    /// from a slice.
+    ///
+    /// This conversion does not allocate or clone the data.
+    ///
+    /// [`Borrowed`]: crate::borrow::Cow::Borrowed
     fn from(s: &'a [T]) -> Cow<'a, [T]> {
         Cow::Borrowed(s)
     }
 }
 
 #[stable(feature = "cow_from_vec", since = "1.8.0")]
 impl<'a, T: Clone> From<Vec<T>> for Cow<'a, [T]> {
+    /// Creates an [`Owned`] variant of [`Cow`]
+    /// from an owned instance of [`Vec`].
+    ///
+    /// This conversion does not allocate or clone the data.
+    ///
+    /// [`Owned`]: crate::borrow::Cow::Owned
     fn from(v: Vec<T>) -> Cow<'a, [T]> {
         Cow::Owned(v)
     }
 }
 
 #[stable(feature = "cow_from_vec_ref", since = "1.28.0")]
 impl<'a, T: Clone> From<&'a Vec<T>> for Cow<'a, [T]> {
+    /// Creates a [`Borrowed`] variant of [`Cow`]
+    /// from a reference to [`Vec`].
+    ///
+    /// This conversion does not allocate or clone the data.
+    ///
+    /// [`Borrowed`]: crate::borrow::Cow::Borrowed
     fn from(v: &'a Vec<T>) -> Cow<'a, [T]> {
         Cow::Borrowed(v.as_slice())
     }