feat(status): add as_u16() method

A `From<StatusCode> for u16` has existed, but the docs cannot show it.
It also is slightly more annoying to use if type inference can't figure
the types out. This includes an explicit method to get a `u16`.

src/status.rs

@@ -307,7 +307,28 @@ impl StatusCode {
         }
     }
 
-    fn to_u16(&self) -> u16 {
+    /// Get the `u16` code from this `StatusCode`.
+    ///
+    /// Also available as `From`/`Into<u16>`.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use hyper::StatusCode;
+    ///
+    /// let status = StatusCode::Ok;
+    /// assert_eq!(status.as_u16(), 200);
+    ///
+    /// // Into
+    /// let num: u16 = status.into();
+    /// assert_eq!(num, 200);
+    ///
+    /// // From
+    /// let other = u16::from(status);
+    /// assert_eq!(num, other);
+    /// ```
+    #[inline]
+    pub fn as_u16(&self) -> u16 {
         match *self {
             StatusCode::Continue => 100,
             StatusCode::SwitchingProtocols => 101,
@@ -498,7 +519,7 @@ impl StatusCode {
     }
 
     fn class(&self) -> StatusClass {
-        match self.to_u16() {
+        match self.as_u16() {
             100...199 => StatusClass::Informational,
             200...299 => StatusClass::Success,
             300...399 => StatusClass::Redirection,
@@ -520,16 +541,17 @@ impl Copy for StatusCode {}
 ///            "123 <unknown status code>");
 /// ```
 impl fmt::Display for StatusCode {
+    #[inline]
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{} {}", self.to_u16(),
+        write!(f, "{} {}", self.as_u16(),
                self.canonical_reason().unwrap_or("<unknown status code>"))
     }
 }
 
 impl PartialEq for StatusCode {
     #[inline]
     fn eq(&self, other: &StatusCode) -> bool {
-        self.to_u16() == other.to_u16()
+        self.as_u16() == other.as_u16()
     }
 }
 
@@ -545,7 +567,7 @@ impl Clone for StatusCode {
 impl PartialOrd for StatusCode {
     #[inline]
     fn partial_cmp(&self, other: &StatusCode) -> Option<Ordering> {
-        self.to_u16().partial_cmp(&(other.to_u16()))
+        self.as_u16().partial_cmp(&(other.as_u16()))
     }
 }
 
@@ -570,7 +592,7 @@ impl Default for StatusCode {
 
 impl From<StatusCode> for u16 {
     fn from(code: StatusCode) -> u16 {
-        code.to_u16()
+        code.as_u16()
     }
 }
 
@@ -632,7 +654,7 @@ mod tests {
     //   - canonical reason
     fn validate(num: u16, status_code: StatusCode, _default_code: StatusCode, reason: Option<&str>) {
         assert_eq!(StatusCode::from_u16(num), status_code);
-        assert_eq!(status_code.to_u16(), num);
+        assert_eq!(status_code.as_u16(), num);
         //assert_eq!(status_code.class().default_code(), default_code);
         assert_eq!(status_code.canonical_reason(), reason);
     }