diff --git a/compiler/codegen/mod_gen.rs b/compiler/codegen/mod_gen.rs
index 415b1cab..ec9dfbdb 100644
--- a/compiler/codegen/mod_gen.rs
+++ b/compiler/codegen/mod_gen.rs
@@ -188,7 +188,7 @@ impl<'am, 'sl, 'interner> ModCtx<'am, 'sl, 'interner> {
         initialise: F,
     ) -> LLVMValueRef
     where
-        F: FnOnce(LLVMValueRef) -> (),
+        F: FnOnce(LLVMValueRef),
     {
         unsafe {
             let function = LLVMGetNamedFunction(self.module, name.as_ptr() as *const _);
diff --git a/compiler/lib.rs b/compiler/lib.rs
index 1814965d..611a0ea8 100644
--- a/compiler/lib.rs
+++ b/compiler/lib.rs
@@ -85,7 +85,7 @@ pub fn program_to_evaluable(
 
         return Err(vec![Diagnostic::error()
             .with_message("no main! function defined in entry module")
-            .with_labels(vec![Label::primary(source_file.file_id(), 0..0)
+            .with_labels(vec![Label::primary(source_file.file_id(), 0..1)
                 .with_message("main! function expected in this file")])]);
     };
 
diff --git a/compiler/mir/eval_hir.rs b/compiler/mir/eval_hir.rs
index 0bf47611..538a69ff 100644
--- a/compiler/mir/eval_hir.rs
+++ b/compiler/mir/eval_hir.rs
@@ -225,7 +225,7 @@ impl EvalHirCtx {
         value: Value,
         insert_local: &mut F,
     ) where
-        F: FnMut(hir::LocalId, Value) -> (),
+        F: FnMut(hir::LocalId, Value),
     {
         if let Some(local_id) = scalar.local_id() {
             insert_local(*local_id, value);
@@ -239,7 +239,7 @@ impl EvalHirCtx {
         value: Value,
         insert_local: &mut F,
     ) where
-        F: FnMut(hir::LocalId, Value) -> (),
+        F: FnMut(hir::LocalId, Value),
     {
         let mut iter = value.into_unsized_list_iter();
 
@@ -259,7 +259,7 @@ impl EvalHirCtx {
         value: Value,
         insert_local: &mut F,
     ) where
-        F: FnMut(hir::LocalId, Value) -> (),
+        F: FnMut(hir::LocalId, Value),
     {
         use crate::hir::destruc::Destruc;
 
diff --git a/compiler/tests/integration.rs b/compiler/tests/integration.rs
index 6c56540c..4f205d51 100644
--- a/compiler/tests/integration.rs
+++ b/compiler/tests/integration.rs
@@ -340,7 +340,7 @@ async fn result_for_single_test(
                         "unexpected status {} returned from integration test",
                         output.status,
                     ))
-                    .with_labels(vec![Label::primary(source_file.file_id(), 0..0)
+                    .with_labels(vec![Label::primary(source_file.file_id(), 0..1)
                         .with_message("integration test file")])]);
             }
         }
@@ -352,7 +352,7 @@ async fn result_for_single_test(
                         "unexpected status {} returned from integration test",
                         output.status,
                     ))
-                    .with_labels(vec![Label::primary(source_file.file_id(), 0..0)
+                    .with_labels(vec![Label::primary(source_file.file_id(), 0..1)
                         .with_message("integration test file")])]);
             }
         }
diff --git a/compiler/typeck/destruc.rs b/compiler/typeck/destruc.rs
index c3c98152..6ade2ad4 100644
--- a/compiler/typeck/destruc.rs
+++ b/compiler/typeck/destruc.rs
@@ -57,7 +57,7 @@ pub fn type_for_decl_destruc(
 
 fn visit_scalar_locals<F>(scalar: &destruc::Scalar<hir::Lowered>, visitor: &mut F)
 where
-    F: FnMut(hir::LocalId, &hir::DeclTy) -> (),
+    F: FnMut(hir::LocalId, &hir::DeclTy),
 {
     if let Some(local_id) = scalar.local_id() {
         visitor(*local_id, scalar.ty());
@@ -72,7 +72,7 @@ pub fn visit_locals<F>(
     visitor: &mut F,
 ) -> Option<hir::LocalId>
 where
-    F: FnMut(hir::LocalId, &hir::DeclTy) -> (),
+    F: FnMut(hir::LocalId, &hir::DeclTy),
 {
     match destruc {
         destruc::Destruc::Scalar(_, ref scalar) => {
diff --git a/runtime/persistent/vector.rs b/runtime/persistent/vector.rs
index 88128b75..ecae9112 100644
--- a/runtime/persistent/vector.rs
+++ b/runtime/persistent/vector.rs
@@ -626,7 +626,7 @@ mod test {
 
     fn assert_nodes_deallocated<T>(block: T)
     where
-        T: FnOnce() -> (),
+        T: FnOnce(),
     {
         assert_eq!(
             0,