From 597fb735710a6cc1bf02919334c3d82718314cfe Mon Sep 17 00:00:00 2001
From: Simon Guest <simon.guest@tesujimath.org>
Date: Fri, 17 Nov 2023 12:06:36 +1300
Subject: [PATCH] Add not_ref()

---
 src/combinator.rs | 48 +++++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs        | 32 +++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/src/combinator.rs b/src/combinator.rs
index a8956cf4..d531c68c 100644
--- a/src/combinator.rs
+++ b/src/combinator.rs
@@ -2085,6 +2085,54 @@ where
     go_extra!(());
 }
 
+/// See [`Parser::not_ref`].
+pub struct NotRef<A, OA> {
+    pub(crate) parser: A,
+    #[allow(dead_code)]
+    pub(crate) phantom: EmptyPhantom<OA>,
+}
+
+impl<A: Copy, OA> Copy for NotRef<A, OA> {}
+impl<A: Clone, OA> Clone for NotRef<A, OA> {
+    fn clone(&self) -> Self {
+        Self {
+            parser: self.parser.clone(),
+            phantom: EmptyPhantom::new(),
+        }
+    }
+}
+
+impl<'a, I, E, A, OA> ParserSealed<'a, I, (), E> for NotRef<A, OA>
+where
+    I: BorrowInput<'a>,
+    E: ParserExtra<'a, I>,
+    A: Parser<'a, I, OA, E>,
+{
+    #[inline(always)]
+    fn go<M: Mode>(&self, inp: &mut InputRef<'a, '_, I, E>) -> PResult<M, ()> {
+        let before = inp.save();
+
+        let alt = inp.errors.alt.take();
+
+        let result = self.parser.go::<Check>(inp);
+        let result_span = inp.span_since(before.offset());
+        inp.rewind(before);
+
+        inp.errors.alt = alt;
+
+        match result {
+            Ok(()) => {
+                let (at, found) = inp.next_ref_inner();
+                inp.add_alt(at, None, found.map(|f| f.into()), result_span);
+                Err(())
+            }
+            Err(()) => Ok(M::bind(|| ())),
+        }
+    }
+
+    go_extra!(());
+}
+
 /// See [`Parser::and_is`].
 pub struct AndIs<A, B, OB> {
     pub(crate) parser_a: A,
diff --git a/src/lib.rs b/src/lib.rs
index 67190ad8..f77f09f1 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1421,6 +1421,38 @@ pub trait Parser<'a, I: Input<'a>, O, E: ParserExtra<'a, I> = extra::Default>:
         }
     }
 
+    /// Invert the result of the contained parser, failing if it succeeds and succeeding if it fails.
+    /// The output of this parser is always `()`, the unit type.
+    ///
+    /// This function is the borrowing equivalent of [`Parser::not`]. Where possible, it's recommended to use [`Parser::not`] instead.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use chumsky::{prelude::*, error::Simple};
+    /// let not_dashes = any_ref::<_, extra::Err<Simple<char>>>()
+    ///     .and_is(just('-').not_ref())
+    ///     .map(|c| *c)
+    ///     .repeated()
+    ///     .collect::<String>();
+    ///
+    /// let v1 = "abcdef".chars().collect::<Vec<_>>();
+    /// assert_eq!(not_dashes.parse(v1.as_slice()).into_result(), Ok("abcdef".to_string()));
+    /// let v2 = "09Qr-X-*&".chars().collect::<Vec<_>>();
+    /// assert!(not_dashes.parse(v2.as_slice()).has_errors());
+    /// let v3 = "-91024".chars().collect::<Vec<_>>();
+    /// assert!(not_dashes.parse(v3.as_slice()).has_errors());
+    /// ```
+    fn not_ref(self) -> NotRef<Self, O>
+    where
+        Self: Sized,
+    {
+        NotRef {
+            parser: self,
+            phantom: EmptyPhantom::new(),
+        }
+    }
+
     /// Parse a pattern zero or more times (analog to Regex's `<PAT>*`).
     ///
     /// Input is eagerly parsed. Be aware that the parser will accept no occurrences of the pattern too. Consider using