cargo doc

README.md

@@ -113,6 +113,7 @@ It is now mid-August, and *Easy Rust* is almost 400 pages long. I am still writi
   - [Cargo](#cargo)
   - [Taking_user_input](#taking-user-input)
   - [Using files](#using-files) 
+  - [Cargo doc](#cargo-doc)
 
 # Part 1 - Rust in your browser
 
@@ -12392,3 +12393,118 @@ Dad: Yep. The world didn't turn color until sometimes in the 1930s...And it was
 That's really weird.
 Well, truth is stranger than fiction.
 ```
+
+## cargo doc
+
+You might have noticed that Rust documentation always looks almost the same. On the left side you can see `struct`s and `trait`s, code examples are on the right, etc. This is because you can automatically make documentation just by typing `cargo doc`.
+
+Even making a project with nothing can help you learn about traits in Rust. For example, here are two structs that do almost nothing, and a `fn main()` that also does nothing.
+
+```rust
+struct DoesNothing {}
+struct PrintThing {}
+
+impl PrintThing {
+    fn prints_something() {
+        println!("I am printing something");
+    }
+}
+
+fn main() {
+    
+}
+```
+
+
+But if you type `cargo doc --open`, you can see a lot more information than you expected. First it shows you this:
+
+```text
+Crate rust_book
+
+Structs
+DoesNothing	
+PrintThing	
+
+Functions
+main
+```
+
+But if you click on one of the structs, it will show you a lot of traits that you didn't think were there:
+
+```text
+Struct rust_book::DoesNothing
+[+] Show declaration
+Auto Trait Implementations
+impl RefUnwindSafe for DoesNothing
+impl Send for DoesNothing
+impl Sync for DoesNothing
+impl Unpin for DoesNothing
+impl UnwindSafe for DoesNothing
+Blanket Implementations
+impl<T> Any for T
+where
+    T: 'static + ?Sized, 
+[src]
+[+]
+impl<T> Borrow<T> for T
+where
+    T: ?Sized, 
+[src]
+[+]
+impl<T> BorrowMut<T> for T
+where
+    T: ?Sized, 
+[src]
+[+]
+impl<T> From<T> for T
+[src]
+[+]
+impl<T, U> Into<U> for T
+where
+    U: From<T>, 
+[src]
+[+]
+impl<T, U> TryFrom<U> for T
+where
+    U: Into<T>, 
+[src]
+[+]
+impl<T, U> TryInto<U> for T
+where
+    U: TryFrom<T>, 
+````
+
+This is because of all the traits that Rust automatically makes for every type.
+
+Then if we add some documentation comments you can see them when you type `cargo doc`.
+
+```rust
+/// This is a struct that does nothing
+struct DoesNothing {}
+/// This struct only has one method.
+struct PrintThing {}
+/// It just prints the same message.
+impl PrintThing {
+    fn prints_something() {
+        println!("I am printing something");
+    }
+}
+
+fn main() {
+    
+}
+```
+
+
+Now it will print:
+
+```text
+Crate rust_book
+Structs
+DoesNothing	This is a struct that does nothing
+PrintThing	This struct only has one method.
+Functions
+main
+```
+
+`cargo doc` is very nice when you use a lot of other people's crates. Because these crates are all on different websites, it can take some time to search them all. But if you use `cargo doc`, you will have them all in the same place on your hard drive.