diff --git a/compiler-cli/src/dependencies.rs b/compiler-cli/src/dependencies.rs
index 16024c9aa..ecc5fa204 100644
--- a/compiler-cli/src/dependencies.rs
+++ b/compiler-cli/src/dependencies.rs
@@ -776,7 +776,6 @@ fn provide_package(
     let mut requirements = HashMap::new();
     parents.push(package_name);
     for (name, requirement) in config.dependencies.into_iter() {
-        let name = name;
         let version = match requirement {
             Requirement::Hex { version } => version,
             Requirement::Path { path } => {
diff --git a/compiler-core/src/analyse.rs b/compiler-core/src/analyse.rs
index 858c567ec..2c00cd627 100644
--- a/compiler-core/src/analyse.rs
+++ b/compiler-core/src/analyse.rs
@@ -130,7 +130,7 @@ pub fn infer_module<A>(
             package,
             direct_dependencies,
             warnings,
-            &mut env,
+            &env,
         )?;
         typed_statements.push(statement);
     }
@@ -934,7 +934,7 @@ fn record_imported_items_for_use_detection<A>(
     current_package: &str,
     direct_dependencies: &HashMap<SmolStr, A>,
     warnings: &TypeWarningEmitter,
-    environment: &mut Environment<'_>,
+    environment: &Environment<'_>,
 ) -> Result<TypedDefinition, Error> {
     let Import {
         documentation,
diff --git a/compiler-core/src/erlang.rs b/compiler-core/src/erlang.rs
index 420563236..c961e046c 100644
--- a/compiler-core/src/erlang.rs
+++ b/compiler-core/src/erlang.rs
@@ -1208,7 +1208,7 @@ fn module_fn_with_args<'a>(
     module: &'a str,
     name: &'a str,
     args: Vec<Document<'a>>,
-    env: &mut Env<'a>,
+    env: &Env<'a>,
 ) -> Document<'a> {
     let args = wrap_args(args);
     if module == env.module {
@@ -1397,14 +1397,14 @@ fn needs_begin_end_wrapping(expression: &TypedExpr) -> bool {
     }
 }
 
-fn todo<'a>(message: &'a Option<SmolStr>, location: SrcSpan, env: &mut Env<'a>) -> Document<'a> {
+fn todo<'a>(message: &'a Option<SmolStr>, location: SrcSpan, env: &Env<'a>) -> Document<'a> {
     let message = message
         .as_deref()
         .unwrap_or("This has not yet been implemented");
     erlang_error("todo", message, location, vec![], env)
 }
 
-fn panic<'a>(location: SrcSpan, message: Option<&'a str>, env: &mut Env<'a>) -> Document<'a> {
+fn panic<'a>(location: SrcSpan, message: Option<&'a str>, env: &Env<'a>) -> Document<'a> {
     let message = message.unwrap_or("panic expression evaluated");
     erlang_error("panic", message, location, vec![], env)
 }
diff --git a/compiler-core/src/javascript/expression.rs b/compiler-core/src/javascript/expression.rs
index 5da0d3ca0..d4ab598bd 100644
--- a/compiler-core/src/javascript/expression.rs
+++ b/compiler-core/src/javascript/expression.rs
@@ -630,10 +630,7 @@ impl<'module> Generator<'module> {
             // We can remove this when we get exhaustiveness checking.
             doc = doc
                 .append(" else {")
-                .append(
-                    docvec!(line(), self.case_no_match(location, subjects.into_iter())?)
-                        .nest(INDENT),
-                )
+                .append(docvec!(line(), self.case_no_match(location, subjects)?).nest(INDENT))
                 .append(line())
                 .append("}")
         }
diff --git a/compiler-core/src/language_server/feedback.rs b/compiler-core/src/language_server/feedback.rs
index 75394a7f0..8743e63ca 100644
--- a/compiler-core/src/language_server/feedback.rs
+++ b/compiler-core/src/language_server/feedback.rs
@@ -19,10 +19,7 @@ impl Feedback {
     }
 
     pub fn append_diagnostic(&mut self, path: Utf8PathBuf, diagnostic: Diagnostic) {
-        self.diagnostics
-            .entry(path)
-            .or_insert_with(Vec::new)
-            .push(diagnostic);
+        self.diagnostics.entry(path).or_default().push(diagnostic);
     }
 
     fn append_message(&mut self, diagnostic: Diagnostic) {
diff --git a/compiler-wasm/src/lib.rs b/compiler-wasm/src/lib.rs
index 37cda3b7d..058af6051 100644
--- a/compiler-wasm/src/lib.rs
+++ b/compiler-wasm/src/lib.rs
@@ -49,19 +49,19 @@ impl Default for CompileOptions {
 /// `target` language.
 pub fn compile_(options: CompileOptions) -> Result<HashMap<String, String>, String> {
     let paths = ProjectPaths::at_filesystem_root();
-    let mut wfs = WasmFileSystem::new();
+    let wfs = WasmFileSystem::new();
 
     for (path, source) in options.source_files.iter() {
-        write_source_file(source, path, &mut wfs);
+        write_source_file(source, path, &wfs);
     }
 
     let _package =
-        compile_project(&mut wfs, options.target, &options).map_err(|e| e.pretty_string())?;
+        compile_project(&wfs, options.target, &options).map_err(|e| e.pretty_string())?;
 
     Ok(gather_compiled_files(&paths, &wfs, options.target).unwrap())
 }
 
-fn write_source_file<P: AsRef<Utf8Path>>(source: &str, path: P, wfs: &mut WasmFileSystem) {
+fn write_source_file<P: AsRef<Utf8Path>>(source: &str, path: P, wfs: &WasmFileSystem) {
     wfs.write(path.as_ref(), source)
         .expect("should always succeed with the virtual file system");
 }
@@ -86,7 +86,7 @@ fn manifest_from_name(name: &str) -> ManifestPackage {
 }
 
 fn compile_project(
-    wfs: &mut WasmFileSystem,
+    wfs: &WasmFileSystem,
     target: Target,
     compile_options: &CompileOptions,
 ) -> Result<Built, Error> {