Recommend implementing Display over ToString

src/conversion/string.md

@@ -1,20 +1,22 @@
 # To and from Strings
 
-## `ToString`
+## Converting to String
 
-To convert any type to a `String` it is as simple as implementing the [`ToString`]
-trait for the type.
+To convert any type to a `String` is as simple as implementing the [`ToString`]
+trait for the type. Rather than doing so directly, you should implement the
+[`fmt::Display`][Display] trait which automagically provides [`ToString`] and
+also allows printing the type as discussed in the section on [`print!`][print].
 
 ```rust,editable
-use std::string::ToString;
+use std::fmt;
 
 struct Circle {
     radius: i32
 }
 
-impl ToString for Circle {
-    fn to_string(&self) -> String {
-        format!("Circle of radius {:?}", self.radius)
+impl fmt::Display for Circle {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "Circle of radius {}", self.radius)
     }
 }
 
@@ -47,5 +49,7 @@ fn main() {
 ```
 
 [`ToString`]: https://doc.rust-lang.org/std/string/trait.ToString.html
+[Display]: https://doc.rust-lang.org/std/fmt/trait.Display.html
+[print]: /hello/print.html
 [`parse`]: https://doc.rust-lang.org/std/primitive.str.html#method.parse
 [`FromStr`]: https://doc.rust-lang.org/std/str/trait.FromStr.html

src/hello/print.md

@@ -67,6 +67,9 @@ friendly fashion.
 Here, `fmt::Display` was used because the std library provides implementations
 for these types. To print text for custom types, more steps are required.
 
+Implementing the `fmt::Display` trait automagically implements the
+[`ToString`] trait which allows us to [convert] the type to [`String`][string].
+
 ### Activities
 
  * Fix the two issues in the above code (see FIXME) so that it runs without
@@ -87,3 +90,5 @@ and [`traits`][traits]
 [string]: std/str.html
 [structs]: custom_types/structs.html
 [traits]: trait.html
+[`ToString`]: https://doc.rust-lang.org/std/string/trait.ToString.html
+[convert]: /conversion/string.html