fix return error

test.sl

@@ -1,9 +1,18 @@
-fn test() {
-    if true {
-        print;
-    } else if false {
-        dont_print;
-    } else {
-        "uwu";
+fn fizzbuzz() {
+    let i = 0;
+    while i < 100 {
+        # don't have function calls yet :(
     }
-}
+}
+
+fn single_fizzbuzz(n) {
+    if n % 15 == 0 {
+        return "FizzBuzz";
+    } else if n % 5 == 0 {
+        return "Buzz";
+    } else if n % 3 == 0 {
+        return "Fizz";
+    } else {
+        return n;
+    }
+}