Impl Borrow and BorrowMut for String and Vec.

This enables them to be used in maps, especially with &str get values in a Map<String, T>.

src/linear_map.rs

@@ -71,7 +71,7 @@ where
     /// assert_eq!(map.capacity(), 8);
     /// ```
     pub fn capacity(&self) -> usize {
-        self.buffer.borrow().capacity()
+        self.buffer.capacity()
     }
 
     /// Clears the map, removing all key-value pairs.

src/string/mod.rs

@@ -1,6 +1,7 @@
 //! A fixed capacity [`String`](https://doc.rust-lang.org/std/string/struct.String.html).
 
 use core::{
+    borrow,
     char::DecodeUtf16Error,
     cmp::Ordering,
     fmt,
@@ -732,6 +733,17 @@ impl<S: Storage> ops::DerefMut for StringInner<S> {
     }
 }
 
+impl<S: Storage> borrow::Borrow<str> for StringInner<S> {
+    fn borrow(&self) -> &str {
+        self.as_str()
+    }
+}
+impl<S: Storage> borrow::BorrowMut<str> for StringInner<S> {
+    fn borrow_mut(&mut self) -> &mut str {
+        self.as_mut_str()
+    }
+}
+
 impl<S: Storage> AsRef<str> for StringInner<S> {
     #[inline]
     fn as_ref(&self) -> &str {

src/vec/mod.rs

@@ -1,5 +1,6 @@
 //! A fixed capacity [`Vec`](https://doc.rust-lang.org/std/vec/struct.Vec.html).
 
+use core::borrow;
 use core::{
     borrow::{Borrow, BorrowMut},
     cmp::Ordering,
@@ -1410,6 +1411,17 @@ impl<T, S: Storage> ops::DerefMut for VecInner<T, S> {
     }
 }
 
+impl<T, S: Storage> borrow::Borrow<[T]> for VecInner<T, S> {
+    fn borrow(&self) -> &[T] {
+        self.as_slice()
+    }
+}
+impl<T, S: Storage> borrow::BorrowMut<[T]> for VecInner<T, S> {
+    fn borrow_mut(&mut self) -> &mut [T] {
+        self.as_mut_slice()
+    }
+}
+
 impl<T, S: Storage> AsRef<VecInner<T, S>> for VecInner<T, S> {
     #[inline]
     fn as_ref(&self) -> &Self {