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.

6 files changed, 24 insertions, 35 deletions

diff --git a/src/client/error.rs b/src/client/error.rs
index 225f2d3..a3df57c 100644
--- a/src/client/error.rs
+++ b/src/client/error.rs
@@ -22,10 +22,8 @@ use ::model::{ChannelType, Permissions};
 /// let mut client = Client::login(&token);
 ///
 /// client.on_member_unban(|context, guild_id, user| {
-///     let discriminator = user.discriminator.parse::<u16>().unwrap();
-///
 ///     // If the user has an even discriminator, don't re-ban them.
-///     if discriminator % 2 == 0 {
+///     if user.discriminator % 2 == 0 {
 ///         return;
 ///     }
 ///
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
diff --git a/tests/test_formatters.rs b/tests/test_formatters.rs
index 3b52dac..fa36832 100644
--- a/tests/test_formatters.rs
+++ b/tests/test_formatters.rs
@@ -49,7 +49,7 @@ fn test_mention() {
         id: UserId(6),
         avatar: None,
         bot: false,
-        discriminator: "4132".to_owned(),
+        discriminator: 4132,
         name: "fake".to_owned(),
     };
     let member = Member {
diff --git a/tests/test_user.rs b/tests/test_user.rs
index dd51f44..790243e 100644
--- a/tests/test_user.rs
+++ b/tests/test_user.rs
@@ -7,7 +7,7 @@ fn gen() -> User {
         id: UserId(210),
         avatar: Some("abc".to_owned()),
         bot: true,
-        discriminator: "1432".to_owned(),
+        discriminator: 1432,
         name: "test".to_owned(),
     }
 }
@@ -31,14 +31,14 @@ fn test_core() {
 fn default_avatars() {
     let mut user = gen();
 
-    user.discriminator = "0".to_owned();
-    assert!(user.default_avatar_url().unwrap().ends_with("0.png"));
-    user.discriminator = "1".to_owned();
-    assert!(user.default_avatar_url().unwrap().ends_with("1.png"));
-    user.discriminator = "2".to_owned();
-    assert!(user.default_avatar_url().unwrap().ends_with("2.png"));
-    user.discriminator = "3".to_owned();
-    assert!(user.default_avatar_url().unwrap().ends_with("3.png"));
-    user.discriminator = "4".to_owned();
-    assert!(user.default_avatar_url().unwrap().ends_with("4.png"));
+    user.discriminator = 0;
+    assert!(user.default_avatar_url().ends_with("0.png"));
+    user.discriminator = 1;
+    assert!(user.default_avatar_url().ends_with("1.png"));
+    user.discriminator = 2;
+    assert!(user.default_avatar_url().ends_with("2.png"));
+    user.discriminator = 3;
+    assert!(user.default_avatar_url().ends_with("3.png"));
+    user.discriminator = 4;
+    assert!(user.default_avatar_url().ends_with("4.png"));
 }