diff --git a/youmubot-cf/src/lib.rs b/youmubot-cf/src/lib.rs
index 0b90613..d49da9b 100644
--- a/youmubot-cf/src/lib.rs
+++ b/youmubot-cf/src/lib.rs
@@ -192,7 +192,7 @@ pub async fn ranks(ctx: &Context, m: &Message) -> CommandResult {
                 }
                 let ranks = &ranks[start..end];
 
-                const HEADERS: [&'static str; 4] = ["Rank", "Rating", "Handle", "Username"];
+                const HEADERS: [&str; 4] = ["Rank", "Rating", "Handle", "Username"];
                 const ALIGNS: [Align; 4] = [Right, Right, Left, Left];
 
                 let ranks_arr = ranks
@@ -354,11 +354,11 @@ pub(crate) async fn contest_rank_table(
                             if result.points > 0.0 {
                                 p_results.push(format!("{}", result.points));
                             } else if result.best_submission_time_seconds.is_some() {
-                                p_results.push(format!("{}", "?"));
+                                p_results.push("?".to_string());
                             } else if result.rejected_attempt_count > 0 {
                                 p_results.push(format!("-{}", result.rejected_attempt_count));
                             } else {
-                                p_results.push(format!("{}", "----"));
+                                p_results.push("----".to_string());
                             }
                         }
 
diff --git a/youmubot-core/src/community/roles.rs b/youmubot-core/src/community/roles.rs
index 7ca4d07..37887bd 100644
--- a/youmubot-core/src/community/roles.rs
+++ b/youmubot-core/src/community/roles.rs
@@ -56,7 +56,7 @@ async fn list(ctx: &Context, m: &Message, _: Args) -> CommandResult {
 
                         let roles = &roles[start..end];
 
-                        const ROLE_HEADERS: [&'static str; 3] = ["Name", "ID", "Description"];
+                        const ROLE_HEADERS: [&str; 3] = ["Name", "ID", "Description"];
                         const ROLE_ALIGNS: [Align; 3] = [Right, Right, Right];
 
                         let roles_arr = roles
diff --git a/youmubot-osu/src/discord/announcer.rs b/youmubot-osu/src/discord/announcer.rs
index 4fe9dc1..a1ee10f 100644
--- a/youmubot-osu/src/discord/announcer.rs
+++ b/youmubot-osu/src/discord/announcer.rs
@@ -203,7 +203,7 @@ impl Announcer {
         let (user, top_scores) = try_join!(user, top_scores)?;
         let mut user = user.unwrap();
         // if top scores exist, user would too
-        let events = std::mem::replace(&mut user.events, vec![])
+        let events = std::mem::take(&mut user.events)
             .into_iter()
             .filter_map(|v| v.to_event_rank())
             .filter(|s| Self::is_announceable_date(s.date, last_update, now))
@@ -344,7 +344,7 @@ impl<'a> CollectedScore<'a> {
             )
             .await?;
 
-        save_beatmap(&env, channel, bm).await.pls_ok();
+        save_beatmap(env, channel, bm).await.pls_ok();
         Ok(m)
     }
 }
diff --git a/youmubot-osu/src/discord/display.rs b/youmubot-osu/src/discord/display.rs
index 78dee39..6d306bc 100644
--- a/youmubot-osu/src/discord/display.rs
+++ b/youmubot-osu/src/discord/display.rs
@@ -298,7 +298,7 @@ mod scores {
                     })
                     .collect::<Vec<_>>();
 
-                const SCORE_HEADERS: [&'static str; 6] =
+                const SCORE_HEADERS: [&str; 6] =
                     ["#", "PP", "Acc", "Ranks", "Mods", "Beatmap"];
                 const SCORE_ALIGNS: [Align; 6] = [Right, Right, Right, Right, Right, Left];
 
@@ -310,7 +310,7 @@ mod scores {
                     .map(|(id, ((play, beatmap), (rank, pp)))| {
                         [
                             format!("{}", id + start + 1),
-                            format!("{}", pp),
+                            pp.to_string(),
                             format!("{:.2}%", play.accuracy(self.mode)),
                             format!("{}", rank),
                             play.mods.to_string(),
diff --git a/youmubot-osu/src/discord/interaction.rs b/youmubot-osu/src/discord/interaction.rs
index ef49263..79c69e2 100644
--- a/youmubot-osu/src/discord/interaction.rs
+++ b/youmubot-osu/src/discord/interaction.rs
@@ -16,9 +16,9 @@ use super::{
     BeatmapWithMode, OsuEnv,
 };
 
-pub(super) const BTN_CHECK: &'static str = "youmubot_osu_btn_check";
-pub(super) const BTN_LB: &'static str = "youmubot_osu_btn_lb";
-pub(super) const BTN_LAST: &'static str = "youmubot_osu_btn_last";
+pub(super) const BTN_CHECK: &str = "youmubot_osu_btn_check";
+pub(super) const BTN_LB: &str = "youmubot_osu_btn_lb";
+pub(super) const BTN_LAST: &str = "youmubot_osu_btn_last";
 
 /// Create an action row for score pages.
 pub fn score_components(guild_id: Option<GuildId>) -> CreateActionRow {
@@ -208,7 +208,7 @@ pub fn handle_lb_button<'a>(
             CreateInteractionResponse::Defer(CreateInteractionResponseMessage::new()),
         )
         .await?;
-        let scores = get_leaderboard(&ctx, &env, &bm, order, guild).await?;
+        let scores = get_leaderboard(ctx, &env, &bm, order, guild).await?;
 
         if scores.is_empty() {
             comp.create_followup(
@@ -230,7 +230,7 @@ pub fn handle_lb_button<'a>(
                 )),
             )
             .await?;
-        display_rankings_table(&ctx, reply, scores, &bm, order).await?;
+        display_rankings_table(ctx, reply, scores, &bm, order).await?;
         Ok(())
     })
 }
diff --git a/youmubot-osu/src/discord/link_parser.rs b/youmubot-osu/src/discord/link_parser.rs
index c994b02..6f9df08 100644
--- a/youmubot-osu/src/discord/link_parser.rs
+++ b/youmubot-osu/src/discord/link_parser.rs
@@ -49,7 +49,7 @@ pub fn parse_old_links<'a>(
                 .name("mode")
                 .map(|v| v.as_str().parse::<u8>())
                 .transpose()?
-                .map(|v| Mode::from(v));
+                .map(Mode::from);
             let embed = match req_type {
                 "b" => {
                     // collect beatmap info
@@ -57,9 +57,9 @@ pub fn parse_old_links<'a>(
                         .name("mods")
                         .and_then(|v| Mods::from_str(v.as_str()).pls_ok())
                         .unwrap_or(Mods::NOMOD);
-                    EmbedType::from_beatmap_id(&env, capture["id"].parse()?, mode, mods).await
+                    EmbedType::from_beatmap_id(env, capture["id"].parse()?, mode, mods).await
                 }
-                "s" => EmbedType::from_beatmapset_id(&env, capture["id"].parse()?).await,
+                "s" => EmbedType::from_beatmapset_id(env, capture["id"].parse()?).await,
                 _ => unreachable!(),
             }?;
             Ok(ToPrint {
@@ -92,11 +92,11 @@ pub fn parse_new_links<'a>(
                         .name("mods")
                         .and_then(|v| Mods::from_str(v.as_str()).pls_ok())
                         .unwrap_or(Mods::NOMOD);
-                    EmbedType::from_beatmap_id(&env, beatmap_id, mode, mods).await
+                    EmbedType::from_beatmap_id(env, beatmap_id, mode, mods).await
                 }
                 None => {
                     EmbedType::from_beatmapset_id(
-                        &env,
+                        env,
                         capture.name("set_id").unwrap().as_str().parse()?,
                     )
                     .await
@@ -124,7 +124,7 @@ pub fn parse_short_links<'a>(
                 .name("mods")
                 .and_then(|v| Mods::from_str(v.as_str()).pls_ok())
                 .unwrap_or(Mods::NOMOD);
-            let embed = EmbedType::from_beatmap_id(&env, id, mode, mods).await?;
+            let embed = EmbedType::from_beatmap_id(env, id, mode, mods).await?;
             Ok(ToPrint { embed, link, mode })
         })
         .collect::<stream::FuturesUnordered<_>>()
diff --git a/youmubot-osu/src/discord/mod.rs b/youmubot-osu/src/discord/mod.rs
index 19e9fd9..f5292d2 100644
--- a/youmubot-osu/src/discord/mod.rs
+++ b/youmubot-osu/src/discord/mod.rs
@@ -386,7 +386,7 @@ async fn add_user(target: serenity::model::id::UserId, user: User, env: &OsuEnv)
                     .user_best(UserID::ID(user.id), |f| f.mode(mode).limit(100))
                     .await
                     .pls_ok()
-                    .unwrap_or_else(|| vec![]);
+                    .unwrap_or_else(std::vec::Vec::new);
 
                 (
                     calculate_weighted_map_length(&scores, &env.beatmaps, mode)
@@ -413,7 +413,7 @@ async fn add_user(target: serenity::model::id::UserId, user: User, env: &OsuEnv)
                 })
         })
         .collect::<stream::FuturesOrdered<_>>()
-        .filter_map(|v| future::ready(v))
+        .filter_map(future::ready)
         .collect::<Map<_, _>>()
         .await;
 
@@ -605,7 +605,7 @@ pub(crate) async fn load_beatmap(
         }
     }
 
-    let b = cache::get_beatmap(&env, channel_id).await.ok().flatten();
+    let b = cache::get_beatmap(env, channel_id).await.ok().flatten();
     b.map(|b| (b, None))
 }
 
@@ -836,7 +836,7 @@ async fn get_user(
     mut args: Args,
     mode: Mode,
 ) -> CommandResult {
-    let user = to_user_id_query(args.single::<UsernameArg>().ok(), &env, msg.author.id).await?;
+    let user = to_user_id_query(args.single::<UsernameArg>().ok(), env, msg.author.id).await?;
     let osu_client = &env.client;
     let meta_cache = &env.beatmaps;
     let user = osu_client.user(&user, |f| f.mode(mode)).await?;
diff --git a/youmubot-osu/src/discord/oppai_cache.rs b/youmubot-osu/src/discord/oppai_cache.rs
index 1f0caf9..de3388b 100644
--- a/youmubot-osu/src/discord/oppai_cache.rs
+++ b/youmubot-osu/src/discord/oppai_cache.rs
@@ -193,7 +193,7 @@ impl BeatmapCache {
             })
             .collect::<Vec<_>>();
         for beatmap in &mut osu_files {
-            if beatmap.metadata.background_file != "" {
+            if !beatmap.metadata.background_file.is_empty() {
                 let bg = backgrounds
                     .entry(beatmap.metadata.background_file.clone())
                     .or_insert_with(|| {
@@ -205,7 +205,7 @@ impl BeatmapCache {
                             content: content.into_boxed_slice(),
                         }))
                     });
-                beatmap.beatmap_background = bg.clone();
+                beatmap.beatmap_background.clone_from(bg);
             }
         }
         Ok(osu_files)
diff --git a/youmubot-osu/src/discord/server_rank.rs b/youmubot-osu/src/discord/server_rank.rs
index 9b8de73..0166cc5 100644
--- a/youmubot-osu/src/discord/server_rank.rs
+++ b/youmubot-osu/src/discord/server_rank.rs
@@ -225,7 +225,7 @@ pub async fn server_rank(ctx: &Context, m: &Message, mut args: Args) -> CommandR
                         table_formatting(&headers, &ALIGNS, table)
                     }
                     RankQuery::PP => {
-                        const HEADERS: [&'static str; 6] =
+                        const HEADERS: [&str; 6] =
                             ["#", "pp", "Map length", "Map age", "Username", "Member"];
                         const ALIGNS: [Align; 6] = [Right, Right, Right, Right, Left, Left];
 
@@ -250,7 +250,7 @@ pub async fn server_rank(ctx: &Context, m: &Message, mut args: Args) -> CommandR
                         table_formatting(&HEADERS, &ALIGNS, table)
                     }
                     RankQuery::TotalPP => {
-                        const HEADERS: [&'static str; 4] = ["#", "Total pp", "Username", "Member"];
+                        const HEADERS: [&str; 4] = ["#", "Total pp", "Username", "Member"];
                         const ALIGNS: [Align; 4] = [Right, Right, Left, Left];
 
                         let table = users
@@ -338,7 +338,7 @@ pub async fn show_leaderboard(ctx: &Context, msg: &Message, mut args: Args) -> C
 
     let scores = {
         let reaction = msg.react(ctx, '⌛').await?;
-        let s = get_leaderboard(&ctx, &env, &bm, order, guild).await?;
+        let s = get_leaderboard(ctx, &env, &bm, order, guild).await?;
         reaction.delete(&ctx).await?;
         s
     };
@@ -360,7 +360,7 @@ pub async fn show_leaderboard(ctx: &Context, msg: &Message, mut args: Args) -> C
                     ),
                 )
                 .await?;
-            display_rankings_table(&ctx, reply, scores, &bm, order).await?;
+            display_rankings_table(ctx, reply, scores, &bm, order).await?;
         }
         ScoreListStyle::Grid => {
             let reply = msg
@@ -497,9 +497,9 @@ pub async fn display_rankings_table(
             let scores = scores[start..end].to_vec();
             let bm = (bm.0.clone(), bm.1);
             Box::pin(async move {
-                const SCORE_HEADERS: [&'static str; 8] =
+                const SCORE_HEADERS: [&str; 8] =
                     ["#", "Score", "Mods", "Rank", "Acc", "Combo", "Miss", "User"];
-                const PP_HEADERS: [&'static str; 8] =
+                const PP_HEADERS: [&str; 8] =
                     ["#", "PP", "Mods", "Rank", "Acc", "Combo", "Miss", "User"];
                 const ALIGNS: [Align; 8] = [Right, Right, Right, Right, Right, Right, Right, Left];
 
diff --git a/youmubot-osu/src/lib.rs b/youmubot-osu/src/lib.rs
index 733b380..c37cbed 100644
--- a/youmubot-osu/src/lib.rs
+++ b/youmubot-osu/src/lib.rs
@@ -123,7 +123,7 @@ impl Client {
         let s = match self.rosu.score(score_id).await {
             Ok(v) => v,
             Err(rosu_v2::error::OsuError::NotFound) => return Ok(None),
-            e @ _ => e?,
+            e => e?,
         };
         Ok(Some(s.into()))
     }
diff --git a/youmubot-prelude/src/announcer.rs b/youmubot-prelude/src/announcer.rs
index 5c86f83..71377bc 100644
--- a/youmubot-prelude/src/announcer.rs
+++ b/youmubot-prelude/src/announcer.rs
@@ -77,7 +77,7 @@ impl MemberToChannels {
     /// Gets the channel list of an user related to that channel.
     pub async fn channels_of(
         &self,
-        http: impl CacheHttp + Clone + Sync,
+        http: impl CacheHttp + Clone,
         u: impl Into<UserId>,
     ) -> Vec<ChannelId> {
         let u: UserId = u.into();
@@ -105,6 +105,12 @@ pub struct AnnouncerHandler {
 }
 
 /// Announcer-managing related.
+impl Default for AnnouncerHandler {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl AnnouncerHandler {
     /// Create a new instance of the handler.
     pub fn new() -> Self {
@@ -119,7 +125,7 @@ impl AnnouncerHandler {
     pub fn add(
         &mut self,
         key: &'static str,
-        announcer: impl Announcer + Send + Sync + 'static,
+        announcer: impl Announcer + Sync + 'static,
     ) -> &mut Self {
         if self
             .announcers
@@ -136,12 +142,12 @@ impl AnnouncerHandler {
     }
 
     pub fn run(self, client: &Client) -> AnnouncerRunner {
-        let runner = AnnouncerRunner {
+        
+        AnnouncerRunner {
             cache_http: CacheAndHttp::from_client(client),
             data: client.data.clone(),
             announcers: self.announcers,
-        };
-        runner
+        }
     }
 }
 
diff --git a/youmubot-prelude/src/setup.rs b/youmubot-prelude/src/setup.rs
index 62494b9..6624882 100644
--- a/youmubot-prelude/src/setup.rs
+++ b/youmubot-prelude/src/setup.rs
@@ -39,11 +39,11 @@ pub async fn setup_prelude(
     // Set up the SQL client.
     data.insert::<crate::SQLClient>(sql_pool.clone());
 
-    let env = Env {
+    
+
+    Env {
         http: http_client,
         sql: sql_pool,
         members: member_cache,
-    };
-
-    env
+    }
 }
diff --git a/youmubot/src/compose_framework.rs b/youmubot/src/compose_framework.rs
index 77228fd..1296cbd 100644
--- a/youmubot/src/compose_framework.rs
+++ b/youmubot/src/compose_framework.rs
@@ -28,7 +28,7 @@ impl Framework for ComposedFramework {
     }
     async fn init(&mut self, client: &Client) {
         for f in self.frameworks.iter_mut() {
-            f.init(&client).await
+            f.init(client).await
         }
     }
 }
diff --git a/youmubot/src/main.rs b/youmubot/src/main.rs
index 921a1ff..d2f2da6 100644
--- a/youmubot/src/main.rs
+++ b/youmubot/src/main.rs
@@ -115,7 +115,7 @@ impl EventHandler for Handler {
             .iter()
             .map(|hook| {
                 hook.write()
-                    .then(|mut h| async move { h.call(&ctx, &interaction).await })
+                    .then(|mut h| async move { h.call(ctx, interaction).await })
             })
             .collect::<stream::FuturesUnordered<_>>()
             .for_each(|v| async move {