Add rust_docs rule

Additional updates to Rust rules:
* Consolidate BUILD files for Rust distribution.
* Prevent rust_binary from depending directly on cc_library.
* Update Rust version to 1.3.0

RELNOTES: [rust] Add rust_docs rule for generating rustdoc.

--
MOS_MIGRATED_REVID=103827592

1 files changed, 31 insertions, 0 deletions

diff --git a/examples/rust/hello_lib/src/greeter.rs b/examples/rust/hello_lib/src/greeter.rs
index be59ff888d..2a4a2f1d3f 100644
--- a/examples/rust/hello_lib/src/greeter.rs
+++ b/examples/rust/hello_lib/src/greeter.rs
@@ -12,19 +12,50 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+/// Object that displays a greeting.
 pub struct Greeter {
     greeting: String,
 }
 
+/// Implementation of Greeter.
 impl Greeter {
+    /// Constructs a new `Greeter`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use hello_lib::greeter;
+    ///
+    /// let greeter = Greeter::new("Hello");
+    /// ```
     pub fn new(greeting: &str) -> Greeter {
         Greeter { greeting: greeting.to_string(), }
     }
 
+    /// Returns the greeting as a string.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use hello_lib::greeter;
+    ///
+    /// let greeter = Greeter::new("Hello");
+    /// let greeting = greeter.greeting("World");
+    /// ```
     pub fn greeting(&self, thing: &str) -> String {
         format!("{} {}", &self.greeting, thing)
     }
 
+    /// Prints the greeting.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use hello_lib::greeter;
+    ///
+    /// let greeter = Greeter::new("Hello");
+    /// greeter.greet("World");
+    /// ```
     pub fn greet(&self, thing: &str) {
         println!("{} {}", &self.greeting, thing);
     }