Fix day18 part1. It was broken when writing part2.

src/day18.rs

@@ -4,7 +4,7 @@ use nom::bytes::complete::tag;
 use nom::character::complete::{char, digit1, space0};
 use nom::combinator::map_res;
 use nom::multi::fold_many0;
-use nom::sequence::{delimited, preceded};
+use nom::sequence::{delimited, pair, preceded};
 use nom::IResult;
 use std::str::FromStr;
 
@@ -12,6 +12,41 @@ fn num(i: &str) -> IResult<&str, usize> {
     map_res(delimited(space0, digit1, space0), FromStr::from_str)(i)
 }
 
+#[aoc(day18, part1)]
+fn solve_d18_p1(input: &str) -> usize {
+    fn paren(i: &str) -> IResult<&str, usize> {
+        delimited(space0, delimited(tag("("), expr, tag(")")), space0)(i)
+    }
+
+    fn num_or_paren(i: &str) -> IResult<&str, usize> {
+        alt((num, paren))(i)
+    }
+
+    fn add_or_paren(i: &str) -> IResult<&str, usize> {
+        let (i, lhs) = num_or_paren(i)?;
+
+        fold_many0(preceded(char('+'), num_or_paren), lhs, |lhs, rhs| lhs + rhs)(i)
+    }
+
+    fn expr(i: &str) -> IResult<&str, usize> {
+        let (i, lhs) = add_or_paren(i)?;
+
+        fold_many0(
+            pair(alt((char('+'), char('*'))), num_or_paren),
+            lhs,
+            |lhs, (op, rhs)| match op {
+                '+' => lhs + rhs,
+                '*' => lhs * rhs,
+                _ => unreachable!(),
+            },
+        )(i)
+    }
+
+    input.split('\n').map(|line| expr(line).unwrap().1).sum()
+}
+
+#[aoc(day18, part2)]
+fn solve_d18_p2(input: &str) -> usize {
     fn paren(i: &str) -> IResult<&str, usize> {
         delimited(space0, delimited(tag("("), expr, tag(")")), space0)(i)
     }
@@ -32,34 +67,5 @@ fn expr(i: &str) -> IResult<&str, usize> {
         fold_many0(preceded(char('*'), add_or_paren), lhs, |lhs, rhs| lhs * rhs)(i)
     }
 
-#[aoc(day18, part1)]
-fn solve_d18_p1(input: &str) -> usize {
     input.split('\n').map(|line| expr(line).unwrap().1).sum()
 }
-
-#[aoc(day18, part2)]
-fn solve_d18_p2(input: &str) -> usize {
-    input.split('\n').map(|line| expr(line).unwrap().1).sum()
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn test_expr() {
-        assert_eq!(expr("2+2"), Ok(("", 4)));
-        assert_eq!(expr("1 + 2 * 3 + 4 * 5 + 6"), Ok(("", 231)));
-        assert_eq!(expr("1 + (2 * 3) + (4 * (5 + 6))"), Ok(("", 51)));
-        assert_eq!(expr("2 * 3 + (4 * 5)"), Ok(("", 46)));
-        assert_eq!(expr("5 + (8 * 3 + 9 + 3 * 4 * 3)"), Ok(("", 1445)));
-        assert_eq!(
-            expr("5 * 9 * (7 * 3 * 3 + 9 * 3 + (8 + 6 * 4))"),
-            Ok(("", 669060))
-        );
-        assert_eq!(
-            expr("((2 + 4 * 9) * (6 + 9 * 8 + 6) + 6) + 2 + 4 * 2"),
-            Ok(("", 23340))
-        );
-    }
-}