Minor updates based on instruction (#1583)

This contains some minor updates from #1565.

---------

Co-authored-by: Marshall Pierce <575695+marshallpierce@users.noreply.github.com>

src/memory-management/exercise.rs

@@ -42,6 +42,8 @@ struct Package {
 impl Package {
     // ANCHOR_END: Package
     // ANCHOR: as_dependency
+    /// Return a representation of this package as a dependency, for use in
+    /// building other packages.
     fn as_dependency(&self) -> Dependency {
         // ANCHOR_END: as_dependency
         Dependency {

src/slices-and-lifetimes/lifetime-annotations.md

@@ -2,10 +2,10 @@
 minutes: 10
 ---
 
-# Lifetimes
+# Lifetime Annotations
 
-A reference has a _lifetime_, which must "outlive" the value it refers to. This
-is verified by the borrow checker.
+A reference has a _lifetime_, which must not "outlive" the value it refers to.
+This is verified by the borrow checker.
 
 The lifetime can be implicit - this is what we have seen so far.  Lifetimes can
 also be explicit: `&'a Point`, `&'document str`.  Lifetimes start with `'` and
@@ -19,7 +19,7 @@ ambiguity; the compiler verifies that there is a valid solution.
 Lifetimes become more complicated when considering passing values to and
 returning values from functions.
 
-```rust,compile_fail
+```rust,eitable,compile_fail
 #[derive(Debug)]
 struct Point(i32, i32);
 

src/smart-pointers/box.md

@@ -35,27 +35,29 @@ Recursive data types or data types with dynamic sizes need to use a `Box`:
 ```rust,editable
 #[derive(Debug)]
 enum List<T> {
-    Cons(T, Box<List<T>>),
+    /// A non-empty list, consisting of the first element and the rest of the list.
+    Element(T, Box<List<T>>),
+    /// An empty list.
     Nil,
 }
 
 fn main() {
-    let list: List<i32> = List::Cons(1, Box::new(List::Cons(2, Box::new(List::Nil))));
+    let list: List<i32> = List::Element(1, Box::new(List::Element(2, Box::new(List::Nil))));
     println!("{list:?}");
 }
 ```
 
 ```bob
  Stack                           Heap
-.- - - - - - - - - - - - -.     .- - - - - - - - - - - - - - - - - - - - - - - -.
-:                         :     :                                               :
-:    list                 :     :                                               :
-:   +------+----+----+    :     :    +------+----+----+    +------+----+----+   :
-:   | Cons | 1  | o--+----+-----+--->| Cons | 2  | o--+--->| Nil  | // | // |   :
-:   +------+----+----+    :     :    +------+----+----+    +------+----+----+   :
-:                         :     :                                               :
-:                         :     :                                               :
-'- - - - - - - - - - - - -'     '- - - - - - - - - - - - - - - - - - - - - - - -'
+.- - - - - - - - - - - - - - .     .- - - - - - - - - - - - - - - - - - - - - - - - -.
+:                            :     :                                                 :
+:    list                    :     :                                                 :
+:   +---------+----+----+    :     :    +---------+----+----+    +------+----+----+  :
+:   | Element | 1  | o--+----+-----+--->| Element | 2  | o--+--->| Nil  | // | // |  :
+:   +---------+----+----+    :     :    +---------+----+----+    +------+----+----+  :
+:                            :     :                                                 :
+:                            :     :                                                 :
+'- - - - - - - - - - - - - - '     '- - - - - - - - - - - - - - - - - - - - - - - - -'
 ```
 <details>
 
@@ -79,12 +81,12 @@ element of the `List` in the heap.
 ```rust,editable
 #[derive(Debug)]
 enum List<T> {
-    Cons(T, Box<List<T>>),
+    Element(T, Box<List<T>>),
     Nil,
 }
 
 fn main() {
-    let list: List<i32> = List::Cons(1, Box::new(List::Cons(2, Box::new(List::Nil))));
+    let list: List<i32> = List::Element(1, Box::new(List::Element(2, Box::new(List::Nil))));
     println!("{list:?}");
 }
 ```
@@ -94,15 +96,15 @@ allows the compiler to optimize the memory layout:
 
 ```bob
  Stack                           Heap
-.- - - - - - - - - - - - -.     .- - - - - - - - - - - - - - - - - - - - - - -.
-:                         :     :                                             :
-:    list                 :     :                                             :
-:   +----+----+           :     :    +----+----+    +----+------+             :
-:   | 1  | o--+-----------+-----+--->| 2  | o--+--->| // | null |             :
-:   +----+----+           :     :    +----+----+    +----+------+             :
-:                         :     :                                             :
-:                         :     :                                             :
-`- - - - - - - - - - - - -'     '- - - - - - - - - - - - - - - - - - - - - - -'
+.- - - - - - - - - - - - - - .     .- - - - - - - - - - - - - -.
+:                            :     :                           :
+:    list                    :     :                           :
+:   +---------+----+----+    :     :    +---------+----+----+  :
+:   | Element | 1  | o--+----+-----+--->| Element | 2  | // |  :
+:   +---------+----+----+    :     :    +---------+----+----+  :
+:                            :     :                           :
+:                            :     :                           :
+'- - - - - - - - - - - - - - '     '- - - - - - - - - - - - - -'
 ```
 
 </details>