try some boxed stuff

src/parse/parser.rs

@@ -188,10 +188,23 @@ impl Keyword {
 
 pub trait Parser<'a, Output> {
     fn parse(&self, &'a Bump, State<'a>) -> ParseResult<'a, Output>;
+
+    fn arena(&self) -> &'a Bump;
+
+    fn map<F, NewOutput>(self, transform: F) -> BoxedParser<'a, NewOutput>
+    where
+        Self: Sized + 'a,
+        Output: 'a,
+        NewOutput: 'a,
+        F: Fn(Output) -> NewOutput + 'a,
+    {
+        BoxedParser::new(self.arena(), map(self, transform))
+    }
 }
 
 pub struct BoxedParser<'a, Output> {
     parser: &'a (dyn Parser<'a, Output> + 'a),
+    arena: &'a Bump,
 }
 
 impl<'a, Output> BoxedParser<'a, Output> {
@@ -201,16 +214,18 @@ impl<'a, Output> BoxedParser<'a, Output> {
     {
         BoxedParser {
             parser: arena.alloc(parser),
+            arena,
         }
     }
 }
 
-impl<'a, F, Output> Parser<'a, Output> for F
+impl<'a, Output> Parser<'a, Output> for BoxedParser<'a, Output> {
-where
-    F: Fn(&'a Bump, State<'a>) -> ParseResult<'a, Output>,
-{
     fn parse(&self, arena: &'a Bump, state: State<'a>) -> ParseResult<'a, Output> {
-        self(arena, state)
+        self.parser.parse(arena, state)
+    }
+
+    fn arena(&self) -> &'a Bump {
+        self.arena
     }
 }
 
@@ -230,7 +245,7 @@ where
     move |arena, state| get_parser().parse(arena, state)
 }
 
-pub fn map<'a, P, F, Before, After>(parser: P, transform: F) -> impl Parser<'a, After>
+fn map<'a, P, F, Before, After>(parser: P, transform: F) -> impl Parser<'a, After>
 where
     P: Parser<'a, Before>,
     F: Fn(Before) -> After,
@@ -242,7 +257,7 @@ where
     }
 }
 
-pub fn map_with_arena<'a, P, F, Before, After>(parser: P, transform: F) -> impl Parser<'a, After>
+fn map_with_arena<'a, P, F, Before, After>(parser: P, transform: F) -> impl Parser<'a, After>
 where
     P: Parser<'a, Before>,
     F: Fn(&'a Bump, Before) -> After,