Make `User.discriminator` a u16

Change the User struct's `discriminator` field to a u16 for performance.

The User struct's `discriminator` field was previously a u16 but changed
to a `String` for ease-of-use. Lately the library has been gearing more
towards performance where possible while not sacrificing ergonomics
_too much_ in most scenarios.

3 files changed, 11 insertions, 20 deletions

diff --git a/src/model/channel/message.rs b/src/model/channel/message.rs
index 5dc59a1..13178ba 100644
--- a/src/model/channel/message.rs
+++ b/src/model/channel/message.rs
@@ -1,3 +1,4 @@
+use std::fmt::Write;
 use std::mem;
 use ::constants;
 use ::client::rest;
@@ -199,7 +200,7 @@ impl Message {
             at_distinct.push('@');
             at_distinct.push_str(&u.name);
             at_distinct.push('#');
-            at_distinct.push_str(&u.discriminator);
+            let _ = write!(at_distinct, "{}", u.discriminator);
             result = result.replace(&u.mention(), &at_distinct);
         }
 
diff --git a/src/model/guild/mod.rs b/src/model/guild/mod.rs
index bd9a7ee..0daeec1 100644
--- a/src/model/guild/mod.rs
+++ b/src/model/guild/mod.rs
@@ -686,12 +686,13 @@ impl Guild {
     ///
     /// [`Member`]: struct.Member.html
     pub fn member_named(&self, name: &str) -> Option<&Member> {
-        let hash_pos = name.find('#');
-
-        let (name, discrim) = if let Some(pos) = hash_pos {
+        let (name, discrim) = if let Some(pos) = name.find('#') {
             let split = name.split_at(pos);
 
-            (split.0, Some(split.1))
+            match split.1.parse::<u16>() {
+                Ok(discrim_int) => (split.0, Some(discrim_int)),
+                Err(_) => (name, None),
+            }
         } else {
             (&name[..], None)
         };
diff --git a/src/model/user.rs b/src/model/user.rs
index 686d394..040effa 100644
--- a/src/model/user.rs
+++ b/src/model/user.rs
@@ -318,7 +318,8 @@ pub struct User {
     /// the same [`name`]. The name+discriminator pair is always unique.
     ///
     /// [`name`]: #structfield.name
-    pub discriminator: String,
+    #[serde(deserialize_with="deserialize_u16")]
+    pub discriminator: u16,
     /// The account's username. Changing username will trigger a discriminator
     /// change if the username+discriminator pair becomes non-unique.
     #[serde(rename="username")]
@@ -366,20 +367,8 @@ impl User {
     /// Returns the formatted URL to the user's default avatar URL.
     ///
     /// This will produce a PNG URL.
-    ///
-    /// # Errors
-    ///
-    /// Returns an [`Error::Num`] if there was an error parsing the
-    /// discriminator. Theoretically this is not possible.
-    ///
-    /// Returns an [`Error::Other`] if the remainder of the calculation
-    /// `discriminator % 5` can not be matched. This is also probably not going
-    /// to occur.
-    ///
-    /// [`Error::Num`]: ../enum.Error.html#variant.Num
-    /// [`Error::Other`]: ../enum.Error.html#variant.Other
-    pub fn default_avatar_url(&self) -> Result<String> {
-        Ok(cdn!("/embed/avatars/{}.png", self.discriminator.parse::<u16>()? % 5u16).to_owned())
+    pub fn default_avatar_url(&self) -> String {
+        cdn!("/embed/avatars/{}.png", self.discriminator % 5u16).to_owned()
     }
 
     /// Sends a message to a user through a direct message channel. This is a