feat: Add move_semantics5 exercise. (rust-lang#746)

* feat: Add move_semantics5 exercise.

* feat: Add option3 exercise

* Address review comments. Fix typos, sentence formatting.

* Remove unwanted newline.

* Address review comments: make comment inline, fix format in print.

exercises/move_semantics/move_semantics5.rs

@@ -0,0 +1,14 @@
+// move_semantics5.rs
+// Make me compile without adding any newlines or removing any of the lines.
+// Execute `rustlings hint move_semantics5` for hints :)
+
+// I AM NOT DONE
+
+fn main() {
+    let mut x = 100;
+    let y = &mut x;
+    let z = &mut *y;
+    *y += 100;
+    *z += 1000;
+    assert_eq!(x, 1200);
+}

exercises/option/option3.rs

@@ -0,0 +1,19 @@
+// option3.rs
+// Make me compile! Execute `rustlings hint option3` for hints
+
+// I AM NOT DONE
+
+struct Point {
+    x: i32,
+    y: i32,
+}
+
+fn main() {
+    let y: Option<Point> = Some(Point { x: 100, y: 200 });
+
+    match y {
+        Some(p) => println!("Co-ordinates are {},{} ", p.x, p.y),
+        _ => println!("no match"),
+    }
+    y; // Fix without deleting this line.
+}

info.toml

@@ -210,6 +210,17 @@ So the end goal is to:
    - since we're not creating a new vec in `main` anymore, we need to create
      a new vec in `fill_vec`, similarly to the way we did in `main`"""
 
+[[exercises]]
+name = "move_semantics5"
+path = "exercises/move_semantics/move_semantics5.rs"
+mode = "compile"
+hint = """
+Carefully reason about the range in which each mutable reference is in
+vogue. Does updating the value of referrent (x) immediately after the
+mutable reference is taken helps? Read more about 'Mutable Referenes'
+in the book's section References and Borrowing':
+https://doc.rust-lang.org/book/ch04-02-references-and-borrowing.html#mutable-references."""
+
 # PRIMITIVE TYPES
 
 [[exercises]]
@@ -578,6 +589,16 @@ For example: Some(Some(variable)) = variable2
 Also see Option::flatten
 """
 
+[[exercises]]
+name = "option3"
+path = "exercises/option/option3.rs"
+mode = "compile"
+hint = """
+The compiler says a partial move happened in the `match`
+statement. How can this be avoided? The compiler shows the correction
+needed. After making the correction as suggested by the compiler, do
+read: https://doc.rust-lang.org/std/keyword.ref.html"""
+
 [[exercises]]
 name = "result1"
 path = "exercises/error_handling/result1.rs"