Something that compiles at least.

2020/src/day2.rs

@@ -43,7 +43,6 @@ struct Policy {
     password: String,
 }
 
-#[aoc_generator(day2)]
 fn parse_regex<'a>(input: &'a str) -> impl Iterator<Item = Policy> + 'a {
     let re = Regex::new(r"(\d+)-(\d+) (\w): (.*)").expect("Failed to compile regex");
     input
@@ -59,7 +58,6 @@ fn parse_regex<'a>(input: &'a str) -> impl Iterator<Item = Policy> + 'a {
         })
 }
 
-#[aoc_generator(day2, part1, handrolled)]
 fn parse_handrolled<'a>(input: &'a str) -> impl Iterator<Item = Policy> + 'a {
     // Example line:
     //   1-3 a: abcde
@@ -94,12 +92,14 @@ fn is_valid_policy_part1(p: &Policy) -> bool {
 }
 
 #[aoc(day2, part1)]
-fn valid_policy_count_part1(policies: &mut dyn Iterator<Item = Policy>) -> usize {
+fn valid_policy_count_part1(input: &str) -> usize {
+    let policies = parse_regex(input);
     policies.filter(|p| is_valid_policy_part1(p)).count()
 }
 
 #[aoc(day2, part1, handrolled)]
-fn valid_policy_count_handrolled_part1(policies: &mut dyn Iterator<Item = Policy>) -> usize {
+fn valid_policy_count_handrolled_part1(input: &str) -> usize {
+    let policies = parse_handrolled(input);
     policies.filter(|p| is_valid_policy_part1(p)).count()
 }
 
@@ -114,7 +114,8 @@ fn is_valid_policy_part2(p: &Policy) -> bool {
 }
 
 #[aoc(day2, part2)]
-fn valid_policy_count_part2(policies: &mut dyn Iterator<Item = Policy>) -> usize {
+fn valid_policy_count_part2(input: &str) -> usize {
+    let policies = parse_regex(input);
     policies.filter(|p| is_valid_policy_part2(p)).count()
 }
 
@@ -155,11 +156,11 @@ mod tests {
 
     #[test]
     fn validate_count_part1() {
-        assert_eq!(valid_policy_count_part1(&mut parse_regex(INPUT)), 2);
+        assert_eq!(valid_policy_count_part1(INPUT), 2);
     }
 
     #[test]
     fn validate_count_part2() {
-        assert_eq!(valid_policy_count_part2(&mut parse_regex(INPUT)), 1);
+        assert_eq!(valid_policy_count_part2(INPUT), 1);
     }
 }