Fixed mistakes and missing semicolon in enum

en/src/compound-types/enum.md

@@ -3,7 +3,7 @@
 
 ```rust,editable
 
-// fix the errors
+// Fix the errors
 enum Number {
     Zero,
     One,
@@ -25,18 +25,18 @@ enum Number2 {
 
 
 fn main() {
-    // a enum variant can be converted to a integer by `as`
+    // An enum variant can be converted to a integer by `as`
     assert_eq!(Number::One, Number1::One);
     assert_eq!(Number1::One, Number2::One);
 
-    println!("Success!")
+    println!("Success!");
 } 
 ```
 
-2. 🌟 each enum variant can hold its own data.
+2. 🌟 Each enum variant can hold its own data.
 ```rust,editable
 
-// fill in the blank
+// Fill in the blank
 enum Message {
     Quit,
     Move { x: i32, y: i32 },
@@ -45,17 +45,17 @@ enum Message {
 }
 
 fn main() {
-    let msg1 = Message::Move{__}; // instantiating with x = 1, y = 2 
-    let msg2 = Message::Write(__); // instantiating with "hello, world!"
+    let msg1 = Message::Move{__}; // Instantiating with x = 1, y = 2 
+    let msg2 = Message::Write(__); // Instantiating with "hello, world!"
 
-    println!("Success!")
+    println!("Success!");
 } 
 ```
 
-3. 🌟🌟 we can get the data which a enum variant is holding by pattern match
+3. 🌟🌟 We can get the data which an enum variant is holding by pattern match.
 ```rust,editable
 
-// fill in the blank and fix the error
+// Fill in the blank and fix the error
 enum Message {
     Quit,
     Move { x: i32, y: i32 },
@@ -72,7 +72,7 @@ fn main() {
         panic!("NEVER LET THIS RUN！");
     }
 
-    println!("Success!")
+    println!("Success!");
 } 
 ```
 
@@ -80,7 +80,7 @@ fn main() {
 
 ```rust,editable
 
-// fill in the blank and fix the errors
+// Fill in the blank and fix the errors
 enum Message {
     Quit,
     Move { x: i32, y: i32 },
@@ -105,11 +105,11 @@ fn show_message(msg: Message) {
 }
 ```
 
-5. 🌟🌟 As there is no `null` in Rust, we have to use enum  `Option<T>`  to deal the cases when value is absent.
+5. 🌟🌟 Since there is no `null` in Rust, we have to use enum  `Option<T>`  to deal with the cases when the value is absent.
 ```rust,editable
 
-// fill in the blank to make the `println` work.
-// also add some code to prevent the `panic` from running.
+// Fill in the blank to make the `println` work.
+// Also add some code to prevent the `panic` from running.
 fn main() {
     let five = Some(5);
     let six = plus_one(five);
@@ -118,7 +118,7 @@ fn main() {
     if let __ = six {
         println!("{}", n);
 
-        println!("Success!")
+        println!("Success!");
     } 
         
     panic!("NEVER LET THIS RUN！");
@@ -133,7 +133,7 @@ fn plus_one(x: Option<i32>) -> Option<i32> {
 ```
 
 
-6. 🌟🌟🌟🌟 implement a `linked-list` via enums.
+6. 🌟🌟🌟🌟 Implement a `linked-list` via enums.
 
 ```rust,editable
 
@@ -166,12 +166,12 @@ impl List {
         // depends on the variant of `self`
         // `self` has type `&List`, and `*self` has type `List`, matching on a
         // concrete type `T` is preferred over a match on a reference `&T`
-        // after Rust 2018 you can use self here and tail (with no ref) below as well,
+        // After Rust 2018 you can use self here and tail (with no ref) below as well,
         // rust will infer &s and ref tail. 
         // See https://doc.rust-lang.org/edition-guide/rust-2018/ownership-and-lifetimes/default-match-bindings.html
         match *self {
             // Can't take ownership of the tail, because `self` is borrowed;
-            // instead take a reference to the tail
+            // Instead take a reference to the tail
             Cons(_, ref tail) => 1 + tail.len(),
             // Base Case: An empty list has zero length
             Nil => 0