diff --git a/rust/lib.rs b/rust/lib.rs
index 5ae47be..122743c 100644
--- a/rust/lib.rs
+++ b/rust/lib.rs
@@ -11,7 +11,7 @@ fn say_hello(name: &str) {
 }
 
 #[unsafe(no_mangle)]
-extern "C" fn hello(c: *const c_char) -> () {
+extern "C" fn hello(c: *const c_char) {
     say_hello(unsafe { CStr::from_ptr(c) }.to_str().unwrap())
 }
 
@@ -23,7 +23,7 @@ struct T {
 }
 
 #[unsafe(no_mangle)]
-extern "C" fn hello_struct(t: &T) -> () {
+extern "C" fn hello_struct(t: &T) {
     say_hello(&format!("{:?}", t))
 }
 
@@ -35,7 +35,7 @@ enum Shape {
 }
 
 #[unsafe(no_mangle)]
-extern "C" fn hello_shape(s: &Shape) -> () {
+extern "C" fn hello_shape(s: &Shape) {
     say_hello(&format!("{:?}", s))
 }
 
@@ -80,7 +80,7 @@ enum BTreeC {
 
 #[unsafe(no_mangle)]
 extern "C" fn sum_tree(t: &BTreeC) -> i64 {
-    (unsafe { std::mem::transmute::<_, &BTree<i64>>(t) }).sum()
+    (unsafe { std::mem::transmute::<&BTreeC, &BTree<i64>>(t) }).sum()
 }
 
 #[unsafe(no_mangle)]
@@ -89,9 +89,6 @@ extern "C" fn sum_slice(v: *const i64, s: usize) -> i64 {
 }
 
 #[unsafe(no_mangle)]
-extern "C" fn print_optional(x: Option<&i8>) -> () {
-    match x {
-        Some(x) => println!("{}", x / 2),
-        None => {}
-    }
+extern "C" fn print_optional(x: Option<&i8>) {
+    if let Some(x) = x { println!("{}", x / 2) }
 }