Change all builders to mutably borrow (#443)

12 files changed, 89 insertions, 69 deletions

diff --git a/src/model/channel/attachment.rs b/src/model/channel/attachment.rs
index 1ba256f..4fd6305 100644
--- a/src/model/channel/attachment.rs
+++ b/src/model/channel/attachment.rs
@@ -53,7 +53,7 @@ impl Attachment {
     /// struct Handler;
     ///
     /// impl EventHandler for Handler {
-    ///     fn message(&self, _: Context, message: Message) {
+    ///     fn message(&self, _: Context, mut message: Message) {
     ///         for attachment in message.attachments {
     ///             let content = match attachment.download() {
     ///                 Ok(content) => content,
diff --git a/src/model/channel/channel_id.rs b/src/model/channel/channel_id.rs
index 66798fa..7314594 100644
--- a/src/model/channel/channel_id.rs
+++ b/src/model/channel/channel_id.rs
@@ -355,8 +355,10 @@ impl ChannelId {
     /// [`Channel::messages`]: ../channel/enum.Channel.html#method.messages
     /// [Read Message History]: ../permissions/struct.Permissions.html#associatedconstant.READ_MESSAGE_HISTORY
     pub fn messages<F>(&self, f: F) -> Result<Vec<Message>>
-        where F: FnOnce(GetMessages) -> GetMessages {
-        let mut map = f(GetMessages::default()).0;
+        where F: FnOnce(&mut GetMessages) -> &mut GetMessages {
+        let mut get_messages = GetMessages::default();
+        f(&mut get_messages);
+        let mut map = get_messages.0;
         let mut query = format!("?limit={}", map.remove(&"limit").unwrap_or(50));
 
         if let Some(after) = map.remove(&"after") {
@@ -481,11 +483,10 @@ impl ChannelId {
     /// [`ChannelId`]: struct.ChannelId.html
     /// [`ModelError::MessageTooLong`]: ../error/enum.Error.html#variant.MessageTooLong
     #[inline]
-    pub fn say<D: ::std::fmt::Display>(&self, content: D) -> Result<Message> {
-        self.send_message(|mut m| {
-            m.content(content);
-
-            m
+    pub fn say<D>(&self, content: D) -> Result<Message>
+    where D: ::std::fmt::Display {
+        self.send_message(|m| {
+            m.content(content)
         })
     }
 
@@ -510,10 +511,8 @@ impl ChannelId {
     ///
     /// let paths = vec!["/path/to/file.jpg", "path/to/file2.jpg"];
     ///
-    /// let _ = channel_id.send_files(paths, |mut m| {
-    ///     m.content("a file");
-    ///
-    ///     m
+    /// let _ = channel_id.send_files(paths, |m| {
+    ///     m.content("a file")
     /// });
     /// ```
     ///
@@ -530,10 +529,8 @@ impl ChannelId {
     ///
     /// let files = vec![(&f1, "my_file.jpg"), (&f2, "my_file2.jpg")];
     ///
-    /// let _ = channel_id.send_files(files, |mut m| {
-    ///     m.content("a file");
-    ///
-    ///     m
+    /// let _ = channel_id.send_files(files, |m| {
+    ///     m.content("a file")
     /// });
     /// ```
     ///
@@ -554,9 +551,12 @@ impl ChannelId {
     /// [Attach Files]: ../permissions/struct.Permissions.html#associatedconstant.ATTACH_FILES
     /// [Send Messages]: ../permissions/struct.Permissions.html#associatedconstant.SEND_MESSAGES
     #[cfg(feature = "utils")]
-    pub fn send_files<'a, F, T, It: IntoIterator<Item=T>>(&self, files: It, f: F) -> Result<Message>
-        where F: FnOnce(CreateMessage) -> CreateMessage, T: Into<AttachmentType<'a>> {
-        let mut msg = f(CreateMessage::default());
+    pub fn send_files<'a, F, T, It>(&self, files: It, f: F) -> Result<Message>
+        where for <'b> F: FnOnce(&'b mut CreateMessage<'b>) -> &'b mut CreateMessage<'b>,
+              T: Into<AttachmentType<'a>>, It: IntoIterator<Item=T> {
+        let mut create_message = CreateMessage::default();
+        let msg = f(&mut create_message);
+
 
         if let Some(content) = msg.0.get(&"content") {
             if let Value::String(ref content) = *content {
@@ -570,7 +570,7 @@ impl ChannelId {
             msg.0.insert("payload_json", json!({ "embed": e }));
         }
 
-        let map = utils::vecmap_to_json_map(msg.0);
+        let map = utils::vecmap_to_json_map(msg.0.clone());
         http::send_files(self.0, files, map)
     }
 
@@ -595,8 +595,9 @@ impl ChannelId {
     /// [Send Messages]: ../permissions/struct.Permissions.html#associatedconstant.SEND_MESSAGES
     #[cfg(feature = "utils")]
     pub fn send_message<F>(&self, f: F) -> Result<Message>
-        where F: FnOnce(CreateMessage) -> CreateMessage {
-        let mut msg = f(CreateMessage::default());
+        where for <'b> F: FnOnce(&'b mut CreateMessage<'b>) -> &'b mut CreateMessage<'b> {
+        let mut create_message = CreateMessage::default();
+        let msg = f(&mut create_message);
 
         if !msg.2.is_empty() {
             if let Some(e) = msg.0.remove(&"embed") {
@@ -604,7 +605,7 @@ impl ChannelId {
             }
         }
 
-        let map = utils::vecmap_to_json_map(msg.0);
+        let map = utils::vecmap_to_json_map(msg.0.clone());
 
         Message::check_content_length(&map)?;
         Message::check_embed_length(&map)?;
@@ -612,10 +613,10 @@ impl ChannelId {
         let message = if msg.2.is_empty() {
             http::send_message(self.0, &Value::Object(map))?
         } else {
-            http::send_files(self.0, msg.2, map)?
+            http::send_files(self.0, msg.2.clone(), map)?
         };
 
-        if let Some(reactions) = msg.1 {
+        if let Some(reactions) = msg.1.clone() {
             for reaction in reactions {
                 self.create_reaction(message.id, reaction)?;
             }
diff --git a/src/model/channel/embed.rs b/src/model/channel/embed.rs
index 8b2a98c..8ce7696 100644
--- a/src/model/channel/embed.rs
+++ b/src/model/channel/embed.rs
@@ -84,18 +84,18 @@ impl Embed {
     /// ```rust,no_run
     /// use serenity::model::channel::Embed;
     ///
-    /// let embed = Embed::fake(|mut e| {
-    ///     e.title("Embed title");
-    ///     e.description("Making a basic embed");
-    ///     e.field("A field", "Has some content.", false);
-    ///
-    ///     e
+    /// let embed = Embed::fake(|e| {
+    ///     e.title("Embed title")
+    ///         .description("Making a basic embed")
+    ///         .field("A field", "Has some content.", false)
     /// });
     /// ```
     #[inline]
     pub fn fake<F>(f: F) -> Value
-        where F: FnOnce(CreateEmbed) -> CreateEmbed {
-        let map = utils::vecmap_to_json_map(f(CreateEmbed::default()).0);
+        where F: FnOnce(&mut CreateEmbed) -> &mut CreateEmbed {
+        let mut create_embed = CreateEmbed::default();
+        f(&mut create_embed);
+        let map = utils::vecmap_to_json_map(create_embed.0);
 
         Value::Object(map)
     }
diff --git a/src/model/channel/group.rs b/src/model/channel/group.rs
index e6946df..5607f3c 100644
--- a/src/model/channel/group.rs
+++ b/src/model/channel/group.rs
@@ -200,7 +200,7 @@ impl Group {
     /// [Read Message History]: ../permissions/struct.Permissions.html#associatedconstant.READ_MESSAGE_HISTORY
     #[inline]
     pub fn messages<F>(&self, f: F) -> Result<Vec<Message>>
-        where F: FnOnce(GetMessages) -> GetMessages {
+        where F: FnOnce(&mut GetMessages) -> &mut GetMessages {
         self.channel_id.messages(f)
     }
 
@@ -307,7 +307,7 @@ impl Group {
     /// [Send Messages]: ../permissions/struct.Permissions.html#associatedconstant.SEND_MESSAGES
     #[inline]
     pub fn send_files<'a, F, T, It: IntoIterator<Item=T>>(&self, files: It, f: F) -> Result<Message>
-        where F: FnOnce(CreateMessage) -> CreateMessage, T: Into<AttachmentType<'a>> {
+        where for <'b> F: FnOnce(&'b mut CreateMessage<'b>) -> &'b mut CreateMessage<'b>, T: Into<AttachmentType<'a>> {
         self.channel_id.send_files(files, f)
     }
 
@@ -321,7 +321,8 @@ impl Group {
     /// [`CreateMessage`]: ../../builder/struct.CreateMessage.html
     /// [Send Messages]: ../permissions/struct.Permissions.html#associatedconstant.SEND_MESSAGES
     #[inline]
-    pub fn send_message<F: FnOnce(CreateMessage) -> CreateMessage>(&self, f: F) -> Result<Message> {
+    pub fn send_message<F>(&self, f: F) -> Result<Message>
+        where for <'b> F: FnOnce(&'b mut CreateMessage<'b>) -> &'b mut CreateMessage<'b> {
         self.channel_id.send_message(f)
     }
 
diff --git a/src/model/channel/guild_channel.rs b/src/model/channel/guild_channel.rs
index 046ca7c..e667efa 100644
--- a/src/model/channel/guild_channel.rs
+++ b/src/model/channel/guild_channel.rs
@@ -120,7 +120,7 @@ impl GuildChannel {
     /// ```
     #[cfg(feature = "utils")]
     pub fn create_invite<F>(&self, f: F) -> Result<RichInvite>
-        where F: FnOnce(CreateInvite) -> CreateInvite {
+        where F: FnOnce(&mut CreateInvite) -> &mut CreateInvite {
         #[cfg(feature = "cache")]
         {
             let req = Permissions::CREATE_INVITE;
@@ -129,8 +129,10 @@ impl GuildChannel {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
             }
         }
+        let mut invite = CreateInvite::default();
+        f(&mut invite);
 
-        let map = serenity_utils::vecmap_to_json_map(f(CreateInvite::default()).0);
+        let map = serenity_utils::vecmap_to_json_map(invite.0);
 
         http::create_invite(self.id.0, &map)
     }
@@ -419,7 +421,7 @@ impl GuildChannel {
     /// [Read Message History]: ../permissions/struct.Permissions.html#associatedconstant.READ_MESSAGE_HISTORY
     #[inline]
     pub fn messages<F>(&self, f: F) -> Result<Vec<Message>>
-        where F: FnOnce(GetMessages) -> GetMessages {
+        where F: FnOnce(&mut GetMessages) -> &mut GetMessages {
         self.id.messages(f)
     }
 
@@ -473,7 +475,7 @@ impl GuildChannel {
     /// struct Handler;
     ///
     /// impl EventHandler for Handler {
-    ///     fn message(&self, _: Context, msg: Message) {
+    ///     fn message(&self, _: Context, mut msg: Message) {
     ///         let channel = match CACHE.read().guild_channel(msg.channel_id) {
     ///             Some(channel) => channel,
     ///             None => return,
@@ -601,8 +603,9 @@ impl GuildChannel {
     /// [Attach Files]: ../permissions/struct.Permissions.html#associatedconstant.ATTACH_FILES
     /// [Send Messages]: ../permissions/struct.Permissions.html#associatedconstant.SEND_MESSAGES
     #[inline]
-    pub fn send_files<'a, F, T, It: IntoIterator<Item=T>>(&self, files: It, f: F) -> Result<Message>
-        where F: FnOnce(CreateMessage) -> CreateMessage, T: Into<AttachmentType<'a>> {
+    pub fn send_files<'a, F, T, It>(&self, files: It, f: F) -> Result<Message>
+        where for <'b> F: FnOnce(&'b mut CreateMessage<'b>) -> &'b mut CreateMessage<'b>,
+              T: Into<AttachmentType<'a>>, It: IntoIterator<Item=T> {
         self.id.send_files(files, f)
     }
 
@@ -625,7 +628,8 @@ impl GuildChannel {
     /// [`ModelError::MessageTooLong`]: ../error/enum.Error.html#variant.MessageTooLong
     /// [`Message`]: struct.Message.html
     /// [Send Messages]: ../permissions/struct.Permissions.html#associatedconstant.SEND_MESSAGES
-    pub fn send_message<F: FnOnce(CreateMessage) -> CreateMessage>(&self, f: F) -> Result<Message> {
+    pub fn send_message<F>(&self, f: F) -> Result<Message>
+    where for <'b> F: FnOnce(&'b mut CreateMessage<'b>) -> &'b mut CreateMessage<'b> {
         #[cfg(feature = "cache")]
         {
             let req = Permissions::SEND_MESSAGES;
diff --git a/src/model/channel/message.rs b/src/model/channel/message.rs
index 7a50b1f..0439c15 100644
--- a/src/model/channel/message.rs
+++ b/src/model/channel/message.rs
@@ -215,7 +215,7 @@ impl Message {
     /// [`EditMessage`]: ../../builder/struct.EditMessage.html
     /// [`the limit`]: ../../builder/struct.EditMessage.html#method.content
     pub fn edit<F>(&mut self, f: F) -> Result<()>
-        where F: FnOnce(EditMessage) -> EditMessage {
+        where F: FnOnce(&mut EditMessage) -> &mut EditMessage {
         #[cfg(feature = "cache")]
         {
             if self.author.id != CACHE.read().user.id {
@@ -230,10 +230,16 @@ impl Message {
         }
 
         if let Some(embed) = self.embeds.get(0) {
-            builder.embed(|_| CreateEmbed::from(embed.clone()));
+            let mut embed = CreateEmbed::from(embed.clone());
+            builder.embed( |e| {
+                *e = embed;
+                e
+            });
         }
 
-        let map = serenity_utils::vecmap_to_json_map(f(builder).0);
+        f(&mut builder);
+
+        let map = serenity_utils::vecmap_to_json_map(builder.0);
 
         match http::edit_message(self.channel_id.0, self.id.0, &Value::Object(map)) {
             Ok(edited) => {
diff --git a/src/model/channel/private_channel.rs b/src/model/channel/private_channel.rs
index 4d602c9..30defca 100644
--- a/src/model/channel/private_channel.rs
+++ b/src/model/channel/private_channel.rs
@@ -175,7 +175,7 @@ impl PrivateChannel {
     /// [Read Message History]: ../permissions/struct.Permissions.html#associatedconstant.READ_MESSAGE_HISTORY
     #[inline]
     pub fn messages<F>(&self, f: F) -> Result<Vec<Message>>
-        where F: FnOnce(GetMessages) -> GetMessages {
+        where F: FnOnce(&mut GetMessages) -> &mut GetMessages {
         self.id.messages(f)
     }
 
@@ -249,8 +249,9 @@ impl PrivateChannel {
     /// [Attach Files]: ../permissions/struct.Permissions.html#associatedconstant.ATTACH_FILES
     /// [Send Messages]: ../permissions/struct.Permissions.html#associatedconstant.SEND_MESSAGES
     #[inline]
-    pub fn send_files<'a, F, T, It: IntoIterator<Item=T>>(&self, files: It, f: F) -> Result<Message>
-        where F: FnOnce(CreateMessage) -> CreateMessage, T: Into<AttachmentType<'a>> {
+    pub fn send_files<'a, F, T, It>(&self, files: It, f: F) -> Result<Message>
+        where for <'b> F: FnOnce(&'b mut CreateMessage<'b>) -> &'b mut CreateMessage<'b>,
+              T: Into<AttachmentType<'a>>, It: IntoIterator<Item=T> {
         self.id.send_files(files, f)
     }
 
@@ -269,7 +270,8 @@ impl PrivateChannel {
     /// [`CreateMessage`]: ../../builder/struct.CreateMessage.html
     /// [`Message`]: struct.Message.html
     #[inline]
-    pub fn send_message<F: FnOnce(CreateMessage) -> CreateMessage>(&self, f: F) -> Result<Message> {
+    pub fn send_message<F>(&self, f: F) -> Result<Message>
+    where for <'b> F: FnOnce(&'b mut CreateMessage<'b>) -> &'b mut CreateMessage<'b> {
         self.id.send_message(f)
     }
 
diff --git a/src/model/guild/guild_id.rs b/src/model/guild/guild_id.rs
index abb3262..a7872f5 100644
--- a/src/model/guild/guild_id.rs
+++ b/src/model/guild/guild_id.rs
@@ -191,8 +191,11 @@ impl GuildId {
     /// [`Guild::create_role`]: ../guild/struct.Guild.html#method.create_role
     /// [Manage Roles]: ../permissions/struct.Permissions.html#associatedconstant.MANAGE_ROLES
     #[inline]
-    pub fn create_role<F: FnOnce(EditRole) -> EditRole>(&self, f: F) -> Result<Role> {
-        let map = utils::vecmap_to_json_map(f(EditRole::default()).0);
+    pub fn create_role<F>(&self, f: F) -> Result<Role>
+    where F: FnOnce(&mut EditRole) -> &mut EditRole {
+        let mut edit_role = EditRole::default();
+        f(&mut edit_role);
+        let map = utils::vecmap_to_json_map(edit_role.0);
 
         let role = http::create_role(self.0, &map)?;
 
@@ -272,8 +275,11 @@ impl GuildId {
     /// [`Guild::edit`]: ../guild/struct.Guild.html#method.edit
     /// [Manage Guild]: ../permissions/struct.Permissions.html#associatedconstant.MANAGE_GUILD
     #[inline]
-    pub fn edit<F: FnOnce(EditGuild) -> EditGuild>(&mut self, f: F) -> Result<PartialGuild> {
-        let map = utils::vecmap_to_json_map(f(EditGuild::default()).0);
+    pub fn edit<F>(&mut self, f: F) -> Result<PartialGuild>
+    where F: FnOnce(&mut EditGuild) -> &mut EditGuild{
+        let mut edit_guild = EditGuild::default();
+        f(&mut edit_guild);
+        let map = utils::vecmap_to_json_map(edit_guild.0);
 
         http::edit_guild(self.0, &map)
     }
diff --git a/src/model/guild/mod.rs b/src/model/guild/mod.rs
index ada70da..3f1baad 100644
--- a/src/model/guild/mod.rs
+++ b/src/model/guild/mod.rs
@@ -418,7 +418,7 @@ impl Guild {
     /// [`Role`]: struct.Role.html
     /// [Manage Roles]: ../permissions/struct.Permissions.html#associatedconstant.MANAGE_ROLES
     pub fn create_role<F>(&self, f: F) -> Result<Role>
-        where F: FnOnce(EditRole) -> EditRole {
+        where F: FnOnce(&mut EditRole) -> &mut EditRole {
         #[cfg(feature = "cache")]
         {
             let req = Permissions::MANAGE_ROLES;
@@ -520,7 +520,7 @@ impl Guild {
     /// [`ModelError::InvalidPermissions`]: ../error/enum.Error.html#variant.InvalidPermissions
     /// [Manage Guild]: ../permissions/struct.Permissions.html#associatedconstant.MANAGE_GUILD
     pub fn edit<F>(&mut self, f: F) -> Result<()>
-        where F: FnOnce(EditGuild) -> EditGuild {
+        where F: FnOnce(&mut EditGuild) -> &mut EditGuild {
         #[cfg(feature = "cache")]
         {
             let req = Permissions::MANAGE_GUILD;
diff --git a/src/model/guild/partial_guild.rs b/src/model/guild/partial_guild.rs
index 38066e4..38f4d53 100644
--- a/src/model/guild/partial_guild.rs
+++ b/src/model/guild/partial_guild.rs
@@ -155,7 +155,8 @@ impl PartialGuild {
     /// [`Guild::create_role`]: struct.Guild.html#method.create_role
     /// [Manage Roles]: ../permissions/struct.Permissions.html#associatedconstant.MANAGE_ROLES
     #[inline]
-    pub fn create_role<F: FnOnce(EditRole) -> EditRole>(&self, f: F) -> Result<Role> {
+    pub fn create_role<F>(&self, f: F) -> Result<Role>
+    where F: FnOnce(&mut EditRole) -> &mut EditRole {
         self.id.create_role(f)
     }
 
@@ -209,7 +210,7 @@ impl PartialGuild {
     ///
     /// [Manage Guild]: ../permissions/struct.Permissions.html#associatedconstant.MANAGE_GUILD
     pub fn edit<F>(&mut self, f: F) -> Result<()>
-        where F: FnOnce(EditGuild) -> EditGuild {
+        where F: FnOnce(&mut EditGuild) -> &mut EditGuild {
         match self.id.edit(f) {
             Ok(guild) => {
                 self.afk_channel_id = guild.afk_channel_id;
diff --git a/src/model/user.rs b/src/model/user.rs
index d0a02df..5676fd1 100644
--- a/src/model/user.rs
+++ b/src/model/user.rs
@@ -438,10 +438,8 @@ impl User {
     ///                 url,
     ///             );
     ///
-    ///             let dm = msg.author.direct_message(|mut m| {
-    ///                 m.content(&help);
-    ///
-    ///                 m
+    ///             let dm = msg.author.direct_message(|m| {
+    ///                 m.content(&help)
     ///             });
     ///
     ///             match dm {
@@ -486,7 +484,7 @@ impl User {
     #[allow(let_and_return)]
     #[cfg(feature = "builder")]
     pub fn direct_message<F>(&self, f: F) -> Result<Message>
-        where F: FnOnce(CreateMessage) -> CreateMessage {
+        where for <'b> F: FnOnce(&'b mut CreateMessage<'b>) -> &'b mut CreateMessage<'b> {
         if self.bot {
             return Err(Error::Model(ModelError::MessagingBot));
         }
@@ -547,7 +545,8 @@ impl User {
     /// [direct_message]: #method.direct_message
     #[cfg(feature = "builder")]
     #[inline]
-    pub fn dm<F: FnOnce(CreateMessage) -> CreateMessage>(&self, f: F) -> Result<Message> {
+    pub fn dm<F>(&self, f: F) -> Result<Message>
+    where for <'b> F: FnOnce(&'b mut CreateMessage<'b>) -> &'b mut CreateMessage<'b> {
         self.direct_message(f)
     }
 
diff --git a/src/model/webhook.rs b/src/model/webhook.rs
index 5f0c294..b87bef8 100644
--- a/src/model/webhook.rs
+++ b/src/model/webhook.rs
@@ -199,11 +199,11 @@ impl Webhook {
     /// });
     /// ```
     #[inline]
-    pub fn execute<F: FnOnce(ExecuteWebhook) -> ExecuteWebhook>(&self,
-                                                                wait: bool,
-                                                                f: F)
-                                                                -> Result<Option<Message>> {
-        let map = utils::vecmap_to_json_map(f(ExecuteWebhook::default()).0);
+    pub fn execute<F>(&self, wait: bool, f: F) -> Result<Option<Message>>
+    where F: FnOnce(&mut ExecuteWebhook) -> &mut ExecuteWebhook {
+        let mut execute_webhook = ExecuteWebhook::default();
+        f(&mut execute_webhook);
+        let map = utils::vecmap_to_json_map(execute_webhook.0);
 
         http::execute_webhook(self.id.0, &self.token, wait, &map)
     }