Merge pull request #1369 from xiaochuanyu/extern-crate

Update extern crate related sections

src/SUMMARY.md

@@ -82,8 +82,8 @@
     - [File hierarchy](mod/split.md)
 
 - [Crates](crates.md)
-    - [Library](crates/lib.md)
-    - [`extern crate`](crates/link.md)
+    - [Creating a Library](crates/lib.md)
+    - [Using a Library](crates/using_lib.md)
 
 - [Cargo](cargo.md)
     - [Dependencies](cargo/deps.md)

src/crates/lib.md

@@ -1,4 +1,4 @@
-# Library
+# Creating a Library
 
 Let's create a library, and then see how to link it to another crate.
 

src/crates/using_lib.md

@@ -0,0 +1,27 @@
+# Using a Library
+
+To link a crate to this new library you may use `rustc`'s `--extern` flag. All 
+of its items will then be imported under a module named the same as the library.
+This module generally behaves the same way as any other module.
+
+```rust,ignore
+// extern crate rary; // May be required for Rust 2015 edition or earlier
+
+fn main() {
+    rary::public_function();
+
+    // Error! `private_function` is private
+    //rary::private_function();
+
+    rary::indirect_access();
+}
+```
+
+```txt
+# Where library.rlib is the path to the compiled library, assumed that it's
+# in the same directory here:
+$ rustc executable.rs --extern rary=library.rlib --edition=2018 && ./executable 
+called rary's `public_function()`
+called rary's `indirect_access()`, that
+> called rary's `private_function()`
+```

src/mod/use.md

@@ -4,8 +4,6 @@ The `use` declaration can be used to bind a full path to a new name, for easier
 access. It is often used like this:
 
 ```rust,editable,ignore
-// extern crate deeply; // normally, this would exist and not be commented out!
-
 use crate::deeply::nested::{
     my_first_function,
     my_second_function,

src/testing/integration_testing.md

@@ -10,7 +10,7 @@ Cargo looks for integration tests in `tests` directory next to `src`.
 File `src/lib.rs`:
 
 ```rust,ignore
-// Assume that crate is called adder, will have to extern it in integration test.
+// Define this in a crate called `adder`.
 pub fn add(a: i32, b: i32) -> i32 {
     a + b
 }
@@ -19,9 +19,6 @@ pub fn add(a: i32, b: i32) -> i32 {
 File with test: `tests/integration_test.rs`:
 
 ```rust,ignore
-// extern crate we're testing, same as any other code would do.
-extern crate adder;
-
 #[test]
 fn test_add() {
     assert_eq!(adder::add(3, 2), 5);
@@ -66,9 +63,6 @@ pub fn setup() {
 File with test: `tests/integration_test.rs`
 
 ```rust,ignore
-// extern crate we're testing, same as any other code will do.
-extern crate adder;
-
 // importing common module.
 mod common;