From e6c5335d43bfbf2fffa3d3c44cde404c970e5ee6 Mon Sep 17 00:00:00 2001
From: John Turner <jturner.usa@gmail.com>
Date: Fri, 14 Nov 2025 20:04:27 +0000
Subject: disallow trailing delimiter in SeparatedBy combinator

---
 src/lib.rs     | 19 ++++++++++++++++++-
 tests/sexpr.rs |  4 ++--
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index acf2dcc..7c1bbcc 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -262,7 +262,10 @@ where
             };
 
             let rest = match self.delimiter.check(rest.clone()) {
-                Ok((rest, _)) => rest,
+                Ok((rest, _)) => match self.parser.check(rest.clone()) {
+                    Ok(_) => rest,
+                    Err(_) => return Some(Err(EM::bind(|| rest))),
+                },
                 _ => rest,
             };
 
@@ -1029,6 +1032,20 @@ mod test {
             .unwrap();
     }
 
+    #[test]
+    fn test_separated_list_with_trailing_delimiter() {
+        let input = "1.0.";
+        let it = InputIter::new(input);
+
+        assert!(
+            numeric1()
+                .separated_by(tag("."))
+                .at_least(1)
+                .check_finished(it)
+                .is_err()
+        );
+    }
+
     #[test]
     fn test_find() {
         let input = "hello world";
diff --git a/tests/sexpr.rs b/tests/sexpr.rs
index 1f8a0af..77ef3a0 100644
--- a/tests/sexpr.rs
+++ b/tests/sexpr.rs
@@ -2,7 +2,7 @@
 
 use mon::{
     Parser, ParserIter, alpha1, alphanumeric, alphanumeric1, input::InputIter, numeric1, tag,
-    whitespace,
+    whitespace, whitespace1,
 };
 
 #[derive(Debug)]
@@ -35,7 +35,7 @@ fn int<'a>() -> impl Parser<&'a str, Output = Sexpr> {
 fn sexpr<'a>() -> impl Parser<&'a str, Output = Sexpr> {
     |it| {
         sexpr()
-            .separated_by(whitespace().repeated().many())
+            .separated_by(whitespace1())
             .many()
             .delimited_by(tag("("), tag(")"))
             .map(|output| Sexpr::List(output))
-- 
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