diff --git a/src/builder.rs b/src/builder.rs
index 7a89085..811c3f1 100644
--- a/src/builder.rs
+++ b/src/builder.rs
@@ -719,9 +719,7 @@ impl<D: Clone> ImplementationBuilder<MariaDbDatabase<D>> for DefaultBuilder {
 
 impl<D: Clone> ImplementationBuilder<PostgresqlDatabase<D>> for DefaultBuilder {
   type Prerequisites = ();
-  fn prerequisites(resource: &PostgresqlDatabase<D>) -> Self::Prerequisites {
-    ()
-  }
+  fn prerequisites(_: &PostgresqlDatabase<D>) -> Self::Prerequisites {}
 
   type Implementation = (PostgreSQLDatabaseSymbol<'static, String, String, StdCommandRunner>,);
   fn create(
diff --git a/src/command_runner.rs b/src/command_runner.rs
index 5d8fd2f..0a64621 100644
--- a/src/command_runner.rs
+++ b/src/command_runner.rs
@@ -72,6 +72,7 @@ impl CommandRunner for StdCommandRunner {
       .expect("Failed to write to stdin");
     let res = child.wait_with_output().await;
     //println!("{:?}", res);
+    #[allow(clippy::let_and_return)]
     res
   }
 }
@@ -125,8 +126,8 @@ impl<U: AsRef<str>, C: CommandRunner> CommandRunner for SetuidCommandRunner<'_,
     let uid = get_user_by_name(self.user_name.as_ref())
       .expect("User does not exist")
       .uid();
-    let _set_home = TempSetEnv::new("HOME", format!("/home/{}", self.user_name.as_ref()));
-    let _set_dbus = TempSetEnv::new("XDG_RUNTIME_DIR", format!("/run/user/{}", uid));
+    let set_home = TempSetEnv::new("HOME", format!("/home/{}", self.user_name.as_ref()));
+    let set_dbus = TempSetEnv::new("XDG_RUNTIME_DIR", format!("/run/user/{}", uid));
     //println!("{} {:?}", program, args);
     let mut child = Command::new(program)
       .args(args)
@@ -143,6 +144,8 @@ impl<U: AsRef<str>, C: CommandRunner> CommandRunner for SetuidCommandRunner<'_,
       .await
       .expect("Failed to write to stdin");
     let res = child.wait_with_output().await;
+    drop(set_home);
+    drop(set_dbus);
     //println!("{:?}", res);
     res
   }
diff --git a/src/locator.rs b/src/locator.rs
index bdf17a7..739c8c3 100644
--- a/src/locator.rs
+++ b/src/locator.rs
@@ -15,23 +15,29 @@ use std::marker::PhantomData;
 use std::path::{Path, PathBuf};
 
 pub trait Policy {
+  #[must_use]
   fn acme_user() -> &'static str {
     "acme"
   }
+
+  #[must_use]
   fn user_home(user_name: &str) -> PathBuf {
-    format!("/home/{}", user_name).into()
+    Path::new("/home").join(user_name)
   }
 
+  #[must_use]
   fn user_name_for_domain(domain_name: &'_ str) -> String {
     domain_name.split('.').rev().fold(String::new(), |result, part| if result.is_empty() { result } else { result + "_" } + part)
   }
 
+  #[must_use]
   fn php_version() -> &'static str {
     "7.0"
   }
 
+  #[must_use]
   fn path_for_data(name: impl Display) -> PathBuf {
-    ("/root/data".as_ref() as &Path).join(format!("_{}", name))
+    Path::new("/root/data").join(format!("_{}", name))
   }
 }
 
@@ -286,7 +292,7 @@ impl<D: AsRef<Path>, POLICY> ResourceLocator<ServeCustom<D>> for DefaultLocator<
     resource: &ServeCustom<D>,
   ) -> (<ServeCustom<D> as Resource>::Artifact, Self::Prerequisites) {
     (
-      PathArtifact::from(("/etc/nginx/sites-enabled/".as_ref() as &Path).join(&resource.0)),
+      PathArtifact::from(Path::new("/etc/nginx/sites-enabled/").join(&resource.0)),
       (),
     )
   }
@@ -298,7 +304,7 @@ impl<D: AsRef<Path>, P, POLICY> ResourceLocator<ServePhp<D, P>> for DefaultLocat
     resource: &ServePhp<D, P>,
   ) -> (<ServePhp<D, P> as Resource>::Artifact, Self::Prerequisites) {
     (
-      PathArtifact::from(("/etc/nginx/sites-enabled/".as_ref() as &Path).join(&resource.0)),
+      PathArtifact::from(Path::new("/etc/nginx/sites-enabled/").join(&resource.0)),
       (),
     )
   }
@@ -313,7 +319,7 @@ impl<D: AsRef<Path>, P, POLICY> ResourceLocator<ServeService<D, P>> for DefaultL
     Self::Prerequisites,
   ) {
     (
-      PathArtifact::from(("/etc/nginx/sites-enabled/".as_ref() as &Path).join(&resource.0)),
+      PathArtifact::from(Path::new("/etc/nginx/sites-enabled/").join(&resource.0)),
       (),
     )
   }
@@ -325,7 +331,7 @@ impl<D: AsRef<Path>, POLICY> ResourceLocator<ServeRedir<D>> for DefaultLocator<P
     resource: &ServeRedir<D>,
   ) -> (<ServeRedir<D> as Resource>::Artifact, Self::Prerequisites) {
     (
-      PathArtifact::from(("/etc/nginx/sites-enabled/".as_ref() as &Path).join(&resource.0)),
+      PathArtifact::from(Path::new("/etc/nginx/sites-enabled/").join(&resource.0)),
       (),
     )
   }
@@ -340,7 +346,7 @@ impl<D: AsRef<Path>, P, POLICY> ResourceLocator<ServeStatic<D, P>> for DefaultLo
     Self::Prerequisites,
   ) {
     (
-      PathArtifact::from(("/etc/nginx/sites-enabled/".as_ref() as &Path).join(&resource.0)),
+      PathArtifact::from(Path::new("/etc/nginx/sites-enabled/").join(&resource.0)),
       (),
     )
   }
diff --git a/src/loggers.rs b/src/loggers.rs
index e5c8573..dcbd0e1 100644
--- a/src/loggers.rs
+++ b/src/loggers.rs
@@ -80,7 +80,7 @@ pub struct FilteringLogger<'a, L> {
 }
 
 impl<'a, L> FilteringLogger<'a, L> {
-  pub fn new(logger: &'a L, max_level: Level) -> Self {
+  pub const fn new(logger: &'a L, max_level: Level) -> Self {
     Self { logger, max_level }
   }
 }
@@ -104,6 +104,7 @@ pub struct StoringLogger {
 }
 
 impl StoringLogger {
+  #[must_use]
   pub fn new() -> Self {
     Self::default()
   }
diff --git a/src/setup/mod.rs b/src/setup/mod.rs
index cca4db8..a187a88 100644
--- a/src/setup/mod.rs
+++ b/src/setup/mod.rs
@@ -7,5 +7,6 @@ pub use symbol_runner::{
   SymbolRunner,
 };
 mod runnable;
+#[allow(clippy::module_inception)]
 mod setup;
 pub use setup::SetupFacade as Setup;
diff --git a/src/setup/runnable.rs b/src/setup/runnable.rs
index 5c3a1c3..4e3e087 100644
--- a/src/setup/runnable.rs
+++ b/src/setup/runnable.rs
@@ -16,6 +16,7 @@ pub trait Runnable {
 }
 
 #[async_trait(?Send)]
+#[allow(clippy::use_self)]
 impl<S> Runnable for S
 where
   Self: Symbol + Debug,
@@ -32,6 +33,7 @@ where
 
 macro_rules! runnable_for_tuple {
   ( $($name:ident)* ) => (
+    #[allow(clippy::let_unit_value)]
     #[async_trait(?Send)]
     #[allow(non_snake_case)]
     impl<$($name: Symbol + Debug,)*> Runnable for ($($name,)*) {
@@ -117,7 +119,7 @@ mod test {
     async fn run_symbol<S: Symbol + Debug, L: Logger>(
       &self,
       symbol: &S,
-      logger: &L,
+      _logger: &L,
       force: bool,
     ) -> Result<bool, Box<dyn Error>> {
       let run = force || !symbol.target_reached().await?;
diff --git a/src/setup/setup.rs b/src/setup/setup.rs
index 4efd0ab..472d52e 100644
--- a/src/setup/setup.rs
+++ b/src/setup/setup.rs
@@ -201,7 +201,7 @@ mod test {
     async fn run_symbol<S: Symbol + Debug, L: Logger>(
       &self,
       symbol: &S,
-      logger: &L,
+      _logger: &L,
       force: bool,
     ) -> Result<bool, Box<dyn Error>> {
       let run = force || !symbol.target_reached().await?;
@@ -239,10 +239,12 @@ mod test {
   #[derive(Clone)]
   struct Artifacts;
   impl<V> FromArtifact<TestResource<V>> for Artifacts {
-    fn from_artifact(from: ()) -> Self {
+    fn from_artifact(_from: ()) -> Self {
       Self
     }
+    #[allow(clippy::unused_unit)]
     fn into_artifact(self) -> () {
+      #[allow(clippy::unused_unit)]
       ()
     }
   }
diff --git a/src/setup/symbol_runner.rs b/src/setup/symbol_runner.rs
index 5448521..378cd90 100644
--- a/src/setup/symbol_runner.rs
+++ b/src/setup/symbol_runner.rs
@@ -17,27 +17,14 @@ pub trait SymbolRunner {
   ) -> Result<bool, Box<dyn Error>>;
 }
 
-#[derive(Debug)]
-pub enum SymbolRunError {
-  Symbol(Box<dyn Error>),
-  ExecuteDidNotReach(()),
-}
+#[derive(Debug, Default)]
+pub struct ExecuteDidNotReachError;
 
-impl Error for SymbolRunError {
-  fn cause(&self) -> Option<&dyn Error> {
-    match self {
-      Self::Symbol(ref e) => Some(&**e),
-      Self::ExecuteDidNotReach(_) => None,
-    }
-  }
-}
+impl Error for ExecuteDidNotReachError {}
 
-impl fmt::Display for SymbolRunError {
+impl fmt::Display for ExecuteDidNotReachError {
   fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-    match self {
-      Self::Symbol(ref e) => write!(f, "{}", e),
-      Self::ExecuteDidNotReach(_) => write!(f, "Target not reached after executing symbol"),
-    }
+    write!(f, "Target not reached after executing symbol")
   }
 }
 
@@ -45,7 +32,8 @@ impl fmt::Display for SymbolRunError {
 pub struct InitializingSymbolRunner;
 
 impl InitializingSymbolRunner {
-  pub fn new() -> Self {
+  #[must_use]
+  pub const fn new() -> Self {
     Self
   }
 
@@ -64,7 +52,7 @@ impl InitializingSymbolRunner {
     if target_reached {
       Ok(())
     } else {
-      Err(Box::new(SymbolRunError::ExecuteDidNotReach(())))
+      Err(Box::new(ExecuteDidNotReachError))
     }
   }
 }
@@ -102,7 +90,8 @@ impl SymbolRunner for InitializingSymbolRunner {
 pub struct DelayingSymbolRunner<R>(R);
 
 impl<R> DelayingSymbolRunner<R> {
-  pub fn new(symbol_runner: R) -> Self {
+  #[must_use]
+  pub const fn new(symbol_runner: R) -> Self {
     Self(symbol_runner)
   }
 }
@@ -137,7 +126,8 @@ where
 pub struct DrySymbolRunner;
 
 impl DrySymbolRunner {
-  pub fn new() -> Self {
+  #[must_use]
+  pub const fn new() -> Self {
     Self
   }
 }
@@ -172,7 +162,8 @@ impl SymbolRunner for DrySymbolRunner {
 pub struct ReportingSymbolRunner<R>(R);
 
 impl<R> ReportingSymbolRunner<R> {
-  pub fn new(symbol_runner: R) -> Self {
+  #[must_use]
+  pub const fn new(symbol_runner: R) -> Self {
     Self(symbol_runner)
   }
 }
@@ -251,6 +242,7 @@ mod test {
       T: Iterator<Item = Result<bool, Box<dyn Error>>>,
     > DummySymbol<T, E>
   {
+    #[must_use]
     fn new<
       IE: IntoIterator<IntoIter = E, Item = Result<(), Box<dyn Error>>>,
       IT: IntoIterator<IntoIter = T, Item = Result<bool, Box<dyn Error>>>,
diff --git a/src/storage.rs b/src/storage.rs
index a963414..aa4ce9d 100644
--- a/src/storage.rs
+++ b/src/storage.rs
@@ -14,6 +14,7 @@ pub trait Storage {
 pub struct SimpleStorage(PathBuf);
 
 impl SimpleStorage {
+  #[must_use]
   pub const fn new(base: PathBuf) -> Self {
     Self(base)
   }
diff --git a/src/symbols/dir.rs b/src/symbols/dir.rs
index f9fdacc..1a60af2 100644
--- a/src/symbols/dir.rs
+++ b/src/symbols/dir.rs
@@ -11,7 +11,7 @@ pub struct Dir<P> {
 }
 
 impl<P> Dir<P> {
-  pub fn new(path: P) -> Self {
+  pub const fn new(path: P) -> Self {
     Self { path }
   }
 }
diff --git a/src/symbols/file.rs b/src/symbols/file.rs
index edff275..a3763c1 100644
--- a/src/symbols/file.rs
+++ b/src/symbols/file.rs
@@ -12,7 +12,7 @@ pub struct File<D, C> {
 }
 
 impl<D, C> File<D, C> {
-  pub fn new(path: D, content: C) -> Self {
+  pub const fn new(path: D, content: C) -> Self {
     Self { path, content }
   }
 }
diff --git a/src/symbols/git/checkout.rs b/src/symbols/git/checkout.rs
index e2ad4a5..14593ba 100644
--- a/src/symbols/git/checkout.rs
+++ b/src/symbols/git/checkout.rs
@@ -63,7 +63,12 @@ impl<C: CommandRunner, _C: Borrow<C>, P: AsRef<Path>, S: AsRef<str>, B: AsRef<st
   }
 
   async fn execute(&self) -> Result<(), Box<dyn Error>> {
-    if !self.target.as_ref().exists() {
+    if self.target.as_ref().exists() {
+      self
+        .run_git(&["fetch", self.source.as_ref(), self.branch.as_ref()])
+        .await?;
+      self.run_git(&["merge", "FETCH_HEAD"]).await?;
+    } else {
       self
         .command_runner
         .borrow()
@@ -80,11 +85,6 @@ impl<C: CommandRunner, _C: Borrow<C>, P: AsRef<Path>, S: AsRef<str>, B: AsRef<st
           ],
         )
         .await?;
-    } else {
-      self
-        .run_git(&["fetch", self.source.as_ref(), self.branch.as_ref()])
-        .await?;
-      self.run_git(&["merge", "FETCH_HEAD"]).await?;
     }
     Ok(())
   }
diff --git a/src/symbols/git/submodules.rs b/src/symbols/git/submodules.rs
index e35eabf..5413b8d 100644
--- a/src/symbols/git/submodules.rs
+++ b/src/symbols/git/submodules.rs
@@ -13,7 +13,7 @@ pub struct GitSubmodules<'a, P, C> {
 }
 
 impl<'a, P, C> GitSubmodules<'a, P, C> {
-  pub fn new(target: P, command_runner: &'a C) -> Self {
+  pub const fn new(target: P, command_runner: &'a C) -> Self {
     Self {
       target,
       command_runner,
diff --git a/src/symbols/mariadb/dump.rs b/src/symbols/mariadb/dump.rs
index 8276532..1b503fa 100644
--- a/src/symbols/mariadb/dump.rs
+++ b/src/symbols/mariadb/dump.rs
@@ -34,8 +34,8 @@ impl<'a, N, C: CommandRunner, S> Dump<'a, N, C, S> {
 impl<N: AsRef<str>, C: CommandRunner, S: Storage> Symbol for Dump<'_, N, C, S> {
   async fn target_reached(&self) -> Result<bool, Box<dyn Error>> {
     let dump_date = self.storage.recent_date()?;
-    let _modified_date = self.run_sql(&format!("select UNIX_TIMESTAMP(MAX(UPDATE_TIME)) from information_schema.tables WHERE table_schema = '{}'", self.db_name.as_ref())).await?;
-    let modified_date = _modified_date.trim_end();
+    let output = self.run_sql(&format!("select UNIX_TIMESTAMP(MAX(UPDATE_TIME)) from information_schema.tables WHERE table_schema = '{}'", self.db_name.as_ref())).await?;
+    let modified_date = output.trim_end();
     Ok(modified_date != "NULL" && u64::from_str(modified_date)? <= dump_date)
   }
 
diff --git a/src/symbols/systemd/user_session.rs b/src/symbols/systemd/user_session.rs
index 5de3342..1f41d46 100644
--- a/src/symbols/systemd/user_session.rs
+++ b/src/symbols/systemd/user_session.rs
@@ -11,7 +11,7 @@ pub struct UserSession<'a, U, C> {
 }
 
 impl<'a, U, C> UserSession<'a, U, C> {
-  pub fn new(user_name: U, command_runner: &'a C) -> Self {
+  pub const fn new(user_name: U, command_runner: &'a C) -> Self {
     Self {
       user_name,
       command_runner,
diff --git a/src/symbols/tls/csr.rs b/src/symbols/tls/csr.rs
index 3b35681..4af3683 100644
--- a/src/symbols/tls/csr.rs
+++ b/src/symbols/tls/csr.rs
@@ -14,7 +14,7 @@ pub struct Csr<C, D, K, P> {
 }
 
 impl<C, D, K, P> Csr<C, D, K, P> {
-  pub fn new(command_runner: C, domain: D, key_path: K, csr_path: P) -> Self {
+  pub const fn new(command_runner: C, domain: D, key_path: K, csr_path: P) -> Self {
     Self {
       command_runner,
       domain,
diff --git a/src/symbols/tls/key.rs b/src/symbols/tls/key.rs
index c5287c0..720d7ab 100644
--- a/src/symbols/tls/key.rs
+++ b/src/symbols/tls/key.rs
@@ -8,19 +8,17 @@ use std::path::Path;
 pub struct Key<C, P> {
   file_path: P,
   command_runner: C,
+  bytes: u32,
 }
 
 impl<C, P> Key<C, P> {
-  pub fn new(command_runner: C, file_path: P) -> Self {
+  pub const fn new(command_runner: C, file_path: P) -> Self {
     Self {
       file_path,
       command_runner,
+      bytes: 4096,
     }
   }
-
-  fn get_bytes(&self) -> u32 {
-    4096
-  }
 }
 
 #[async_trait(?Send)]
@@ -57,7 +55,7 @@ impl<C: CommandRunner, P: AsRef<Path>> Symbol for Key<C, P> {
           "genrsa",
           "-out",
           self.file_path.as_ref(),
-          self.get_bytes().to_string(),
+          self.bytes.to_string(),
         ],
       )
       .await
diff --git a/src/symbols/user.rs b/src/symbols/user.rs
index 5d54f3f..db784a7 100644
--- a/src/symbols/user.rs
+++ b/src/symbols/user.rs
@@ -15,7 +15,7 @@ pub struct User<U, C> {
 }
 
 impl<U, C> User<U, C> {
-  pub fn new(user_name: U, command_runner: C) -> Self {
+  pub const fn new(user_name: U, command_runner: C) -> Self {
     Self {
       user_name,
       command_runner,
@@ -41,7 +41,7 @@ impl<U: AsRef<str>, C: CommandRunner> Symbol for User<U, C> {
     // adduser is not reentrant because finding the next uid
     // and creating the account is not an atomic operation
     let wait = WAIT.acquire().await;
-    self
+    let res = self
       .command_runner
       .run_successfully(
         "adduser",
@@ -51,7 +51,9 @@ impl<U: AsRef<str>, C: CommandRunner> Symbol for User<U, C> {
           self.user_name.as_ref(),
         ],
       )
-      .await
+      .await;
+    drop(wait);
+    res
   }
 }
 
diff --git a/src/templates/nginx/server.rs b/src/templates/nginx/server.rs
index fe7aa60..9f04bbd 100644
--- a/src/templates/nginx/server.rs
+++ b/src/templates/nginx/server.rs
@@ -1,6 +1,7 @@
 use std::fmt::Display;
 use std::path::Path;
 
+#[must_use]
 pub fn default_server<P: AsRef<Path>>(challenges_snippet_path: P) -> String {
   format!(
     "server {{
@@ -12,6 +13,7 @@ pub fn default_server<P: AsRef<Path>>(challenges_snippet_path: P) -> String {
   )
 }
 
+#[must_use]
 pub fn server_config<D: Display, C: AsRef<Path>, K: AsRef<Path>, T: Display, S: AsRef<Path>>(
   domain: D,
   cert_path: C,
@@ -53,6 +55,7 @@ server {{
   )
 }
 
+#[must_use]
 pub fn php_snippet<SOCKET: AsRef<Path>, STATIC: AsRef<Path>>(
   index: &'static str,
   socket_path: SOCKET,
@@ -71,6 +74,7 @@ pub fn php_snippet<SOCKET: AsRef<Path>, STATIC: AsRef<Path>>(
   )
 }
 
+#[must_use]
 pub fn redir_snippet(target: &str) -> String {
   format!(
     "location / {{
@@ -85,6 +89,7 @@ pub trait SocketSpec {
 }
 
 impl<T: AsRef<Path>> SocketSpec for T {
+  #[must_use]
   fn to_nginx(&self) -> String {
     format!("unix:{}:", self.as_ref().to_str().unwrap())
   }
@@ -94,17 +99,20 @@ impl<T: AsRef<Path>> SocketSpec for T {
 pub struct LocalTcpSocket(usize);
 
 impl LocalTcpSocket {
+  #[must_use]
   pub const fn new(x: usize) -> Self {
     Self(x)
   }
 }
 
 impl SocketSpec for LocalTcpSocket {
+  #[must_use]
   fn to_nginx(&self) -> String {
     format!("localhost:{}", self.0)
   }
 }
 
+#[must_use]
 pub fn proxy_snippet<S: SocketSpec, STATIC: AsRef<Path>>(
   socket_path: &S,
   static_path: STATIC,
@@ -125,6 +133,7 @@ pub fn proxy_snippet<S: SocketSpec, STATIC: AsRef<Path>>(
   )
 }
 
+#[must_use]
 pub fn static_snippet<S: AsRef<Path>>(static_path: S) -> String {
   format!(
     "root                    {};
@@ -134,6 +143,7 @@ pub fn static_snippet<S: AsRef<Path>>(static_path: S) -> String {
   )
 }
 
+#[must_use]
 pub fn dokuwiki_snippet() -> String {
   "
   location ~ /(data/|conf/|bin/|inc/|install.php) { deny all; }
@@ -149,6 +159,7 @@ pub fn dokuwiki_snippet() -> String {
   }".into()
 }
 
+#[must_use]
 pub fn nextcloud_snippet() -> String {
   "
   client_max_body_size 500M;
diff --git a/src/to_artifact.rs b/src/to_artifact.rs
index e158f07..e45cda9 100644
--- a/src/to_artifact.rs
+++ b/src/to_artifact.rs
@@ -17,6 +17,8 @@ macro_rules! to_artifact {
 for_each_tuple!(to_artifact);
 
 impl<T: Resource> ToArtifact for Option<T> {
+  // FIXME: https://github.com/rust-lang/rust-clippy/issues/2843
+  #![allow(clippy::use_self)]
   type Artifact = Option<T::Artifact>;
 }