diff --git a/cstree/examples/math.rs b/cstree/examples/math.rs
index ae44a4e..a98f6a2 100644
--- a/cstree/examples/math.rs
+++ b/cstree/examples/math.rs
@@ -114,7 +114,7 @@ fn print(indent: usize, element: SyntaxElementRef<'_>, resolver: &impl Resolver)
     print!("{:indent$}", "", indent = indent);
     match element {
         NodeOrToken::Node(node) => {
-            println!("- {:?}", kind);
+            println!("- {kind:?}");
             for child in node.children_with_tokens() {
                 print(indent + 2, child, resolver);
             }
diff --git a/cstree/examples/s_expressions.rs b/cstree/examples/s_expressions.rs
index dcbe7a3..f37b3fb 100644
--- a/cstree/examples/s_expressions.rs
+++ b/cstree/examples/s_expressions.rs
@@ -392,7 +392,7 @@ nan
     let root = parse.root();
     let resolver = &parse.resolver;
     let res = root.sexps().map(|it| it.eval(resolver)).collect::<Vec<_>>();
-    eprintln!("{:?}", res);
+    eprintln!("{res:?}");
     assert_eq!(res, vec![Some(92), Some(92), None, None, Some(92),])
 }
 
diff --git a/cstree/src/interning/lasso_compat/token_interner.rs b/cstree/src/interning/lasso_compat/token_interner.rs
index 35b8e75..248baa4 100644
--- a/cstree/src/interning/lasso_compat/token_interner.rs
+++ b/cstree/src/interning/lasso_compat/token_interner.rs
@@ -15,7 +15,7 @@ const DEFAULT_STRING_CAPACITY: usize = 512;
 
 /// Default memory in bytes that the interner will initially allocate space for.
 /// Value recommended by the author of `lasso`.
-const DEFAULT_BYTE_CAPACITY: NonZeroUsize = unsafe { NonZeroUsize::new_unchecked(4096) };
+const DEFAULT_BYTE_CAPACITY: NonZeroUsize = NonZeroUsize::new(4096).unwrap();
 
 macro_rules! impl_traits {
     (for $interner:ty $(, if #[cfg(feature = $feature:literal)])?) => {
diff --git a/cstree/src/syntax/element.rs b/cstree/src/syntax/element.rs
index bef407a..27fbdc4 100644
--- a/cstree/src/syntax/element.rs
+++ b/cstree/src/syntax/element.rs
@@ -292,7 +292,7 @@ impl<'a, S: Syntax, D> SyntaxElementRef<'a, S, D> {
 
     /// Returns an iterator along the chain of parents of this node.
     #[inline]
-    pub fn ancestors(&self) -> impl Iterator<Item = &'a SyntaxNode<S, D>> {
+    pub fn ancestors(&self) -> impl Iterator<Item = &'a SyntaxNode<S, D>> + use<'a, S, D> {
         match self {
             NodeOrToken::Node(it) => it.ancestors(),
             NodeOrToken::Token(it) => it.parent().ancestors(),
diff --git a/cstree/src/syntax/iter.rs b/cstree/src/syntax/iter.rs
index 74926d8..fdc0ae1 100644
--- a/cstree/src/syntax/iter.rs
+++ b/cstree/src/syntax/iter.rs
@@ -66,12 +66,21 @@ impl ExactSizeIterator for Iter<'_> {
 impl FusedIterator for Iter<'_> {}
 
 /// An iterator over the child nodes of a [`SyntaxNode`].
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub struct SyntaxNodeChildren<'n, S: Syntax, D: 'static = ()> {
     inner:  Iter<'n>,
     parent: &'n SyntaxNode<S, D>,
 }
 
+impl<S: Syntax, D> Clone for SyntaxNodeChildren<'_, S, D> {
+    fn clone(&self) -> Self {
+        Self {
+            inner:  self.inner.clone(),
+            parent: self.parent,
+        }
+    }
+}
+
 impl<'n, S: Syntax, D> SyntaxNodeChildren<'n, S, D> {
     #[inline]
     pub(super) fn new(parent: &'n SyntaxNode<S, D>) -> Self {
@@ -118,12 +127,21 @@ impl<S: Syntax, D> ExactSizeIterator for SyntaxNodeChildren<'_, S, D> {
 impl<S: Syntax, D> FusedIterator for SyntaxNodeChildren<'_, S, D> {}
 
 /// An iterator over the children of a [`SyntaxNode`].
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub struct SyntaxElementChildren<'n, S: Syntax, D: 'static = ()> {
     inner:  Iter<'n>,
     parent: &'n SyntaxNode<S, D>,
 }
 
+impl<S: Syntax, D> Clone for SyntaxElementChildren<'_, S, D> {
+    fn clone(&self) -> Self {
+        Self {
+            inner:  self.inner.clone(),
+            parent: self.parent,
+        }
+    }
+}
+
 impl<'n, S: Syntax, D> SyntaxElementChildren<'n, S, D> {
     #[inline]
     pub(super) fn new(parent: &'n SyntaxNode<S, D>) -> Self {
@@ -166,3 +184,35 @@ impl<S: Syntax, D> ExactSizeIterator for SyntaxElementChildren<'_, S, D> {
     }
 }
 impl<S: Syntax, D> FusedIterator for SyntaxElementChildren<'_, S, D> {}
+
+#[cfg(test)]
+#[allow(dead_code)]
+mod tests {
+    use super::*;
+
+    #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+    struct DummyKind;
+
+    impl Syntax for DummyKind {
+        fn from_raw(_: crate::RawSyntaxKind) -> Self {
+            unreachable!()
+        }
+
+        fn into_raw(self) -> crate::RawSyntaxKind {
+            unreachable!()
+        }
+
+        fn static_text(self) -> Option<&'static str> {
+            unreachable!()
+        }
+    }
+
+    struct NotClone;
+
+    fn assert_clone<C: Clone>() {}
+
+    fn test_impls_clone() {
+        assert_clone::<SyntaxNodeChildren<DummyKind, NotClone>>();
+        assert_clone::<SyntaxElementChildren<DummyKind, NotClone>>();
+    }
+}
diff --git a/cstree/src/syntax/node.rs b/cstree/src/syntax/node.rs
index 429b1da..356e0f6 100644
--- a/cstree/src/syntax/node.rs
+++ b/cstree/src/syntax/node.rs
@@ -851,9 +851,7 @@ impl<S: Syntax, D> SyntaxNode<S, D> {
         let range = self.text_range();
         assert!(
             range.start() <= offset && offset <= range.end(),
-            "Bad offset: range {:?} offset {:?}",
-            range,
-            offset
+            "Bad offset: range {range:?} offset {offset:?}"
         );
         if range.is_empty() {
             return TokenAtOffset::None;
@@ -940,7 +938,7 @@ impl GreenNode {
         &self,
         start_index: usize,
         mut offset: TextSize,
-    ) -> impl Iterator<Item = (GreenElementRef, (usize, TextSize))> {
+    ) -> impl Iterator<Item = (GreenElementRef<'_>, (usize, TextSize))> {
         self.children()
             .skip(start_index)
             .enumerate()
@@ -956,7 +954,7 @@ impl GreenNode {
         &self,
         end_index: usize,
         mut offset: TextSize,
-    ) -> impl Iterator<Item = (GreenElementRef, (usize, TextSize))> {
+    ) -> impl Iterator<Item = (GreenElementRef<'_>, (usize, TextSize))> {
         self.children()
             .take(end_index)
             .rev()
diff --git a/cstree/src/syntax/resolved.rs b/cstree/src/syntax/resolved.rs
index 500d611..4c97301 100644
--- a/cstree/src/syntax/resolved.rs
+++ b/cstree/src/syntax/resolved.rs
@@ -713,7 +713,7 @@ impl<'a, S: Syntax, D> ResolvedElementRef<'a, S, D> {
 
     /// Returns an iterator along the chain of parents of this node.
     #[inline]
-    pub fn ancestors(&self) -> impl Iterator<Item = &'a ResolvedNode<S, D>> {
+    pub fn ancestors(&self) -> impl Iterator<Item = &'a ResolvedNode<S, D>> + use<'a, S, D> {
         match self {
             NodeOrToken::Node(it) => it.ancestors(),
             NodeOrToken::Token(it) => it.parent().ancestors(),
diff --git a/cstree/src/syntax/text.rs b/cstree/src/syntax/text.rs
index b613556..a0724f4 100644
--- a/cstree/src/syntax/text.rs
+++ b/cstree/src/syntax/text.rs
@@ -40,13 +40,20 @@ use crate::{
 /// let sub = text.slice(2.into()..5.into());
 /// assert_eq!(sub, "748");
 /// ```
-#[derive(Clone)]
 pub struct SyntaxText<'n, 'i, I: ?Sized, S: Syntax, D: 'static = ()> {
     node:     &'n SyntaxNode<S, D>,
     range:    TextRange,
     resolver: &'i I,
 }
 
+impl<I: ?Sized, S: Syntax, D> Clone for SyntaxText<'_, '_, I, S, D> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl<I: ?Sized, S: Syntax, D> Copy for SyntaxText<'_, '_, I, S, D> {}
+
 impl<'n, 'i, I: Resolver<TokenKey> + ?Sized, S: Syntax, D> SyntaxText<'n, 'i, I, S, D> {
     pub(crate) fn new(node: &'n SyntaxNode<S, D>, resolver: &'i I) -> Self {
         let range = node.text_range();
@@ -84,6 +91,18 @@ impl<'n, 'i, I: Resolver<TokenKey> + ?Sized, S: Syntax, D> SyntaxText<'n, 'i, I,
         found(res)
     }
 
+    /// If `self.contains_char(c)`, returns `Some(pos)`, where `pos` is the byte position of the
+    /// last appearance of `c`. Otherwise, returns `None`.
+    pub fn rfind_char(&self, c: char) -> Option<TextSize> {
+        let mut acc: TextSize = 0.into();
+        let mut res = None;
+        self.for_each_chunk(|chunk| {
+            res = chunk.rfind(c).map(|pos| acc + TextSize::from(pos as u32)).or(res);
+            acc += TextSize::of(chunk);
+        });
+        res
+    }
+
     /// If `offset < self.len()`, returns `Some(c)`, where `c` is the first `char` at or after
     /// `offset` (in bytes). Otherwise, returns `None`.
     pub fn char_at(&self, offset: TextSize) -> Option<char> {
@@ -143,7 +162,7 @@ impl<'n, 'i, I: Resolver<TokenKey> + ?Sized, S: Syntax, D> SyntaxText<'n, 'i, I,
     /// See also [`fold_chunks`](SyntaxText::fold_chunks) for folds that always succeed.
     pub fn try_fold_chunks<T, F, E>(&self, init: T, mut f: F) -> Result<T, E>
     where
-        F: FnMut(T, &str) -> Result<T, E>,
+        F: FnMut(T, &'i str) -> Result<T, E>,
     {
         self.tokens_with_ranges().try_fold(init, move |acc, (token, range)| {
             f(acc, &token.resolve_text(self.resolver)[range])
@@ -188,7 +207,7 @@ impl<'n, 'i, I: Resolver<TokenKey> + ?Sized, S: Syntax, D> SyntaxText<'n, 'i, I,
         self.fold_chunks((), |(), chunk| f(chunk))
     }
 
-    fn tokens_with_ranges(&self) -> impl Iterator<Item = (&SyntaxToken<S, D>, TextRange)> {
+    fn tokens_with_ranges(&self) -> impl Iterator<Item = (&'n SyntaxToken<S, D>, TextRange)> + use<'i, 'n, I, S, D> {
         let text_range = self.range;
         self.node
             .descendants_with_tokens()
@@ -201,11 +220,9 @@ impl<'n, 'i, I: Resolver<TokenKey> + ?Sized, S: Syntax, D> SyntaxText<'n, 'i, I,
     }
 }
 
+#[inline]
 fn found<T>(res: Result<(), T>) -> Option<T> {
-    match res {
-        Ok(()) => None,
-        Err(it) => Some(it),
-    }
+    res.err()
 }
 
 impl<I: Resolver<TokenKey> + ?Sized, S: Syntax, D> fmt::Debug for SyntaxText<'_, '_, I, S, D> {
@@ -378,7 +395,7 @@ mod private {
 
 #[cfg(test)]
 mod tests {
-    use crate::{build::GreenNodeBuilder, RawSyntaxKind};
+    use crate::{build::GreenNodeBuilder, interning::TokenInterner, RawSyntaxKind};
 
     use super::*;
 
@@ -429,9 +446,9 @@ mod tests {
             let t2 = t2.resolve_text(&resolver);
             let expected = t1.to_string() == t2.to_string();
             let actual = t1 == t2;
-            assert_eq!(expected, actual, "`{}` (SyntaxText) `{}` (SyntaxText)", t1, t2);
+            assert_eq!(expected, actual, "`{t1}` (SyntaxText) `{t2}` (SyntaxText)");
             let actual = t1 == t2.to_string().as_str();
-            assert_eq!(expected, actual, "`{}` (SyntaxText) `{}` (&str)", t1, t2);
+            assert_eq!(expected, actual, "`{t1}` (SyntaxText) `{t2}` (&str)");
         }
         fn check(t1: &[&str], t2: &[&str]) {
             do_check(t1, t2);
@@ -450,4 +467,17 @@ mod tests {
         check(&["{", "abc", "}"], &["{", "123", "}", "{"]);
         check(&["{", "abc", "}ab"], &["{", "abc", "}", "ab"]);
     }
+
+    #[allow(dead_code)]
+    mod impl_asserts {
+        use super::*;
+
+        struct NotClone;
+
+        fn assert_copy<C: Copy>() {}
+
+        fn test_impls_copy() {
+            assert_copy::<SyntaxText<TokenInterner, SyntaxKind, NotClone>>();
+        }
+    }
 }
diff --git a/cstree/src/syntax/token.rs b/cstree/src/syntax/token.rs
index bcd1ff9..65dd902 100644
--- a/cstree/src/syntax/token.rs
+++ b/cstree/src/syntax/token.rs
@@ -58,13 +58,13 @@ impl<S: Syntax, D> SyntaxToken<S, D> {
         write!(target, "{:?}@{:?}", self.kind(), self.text_range())?;
         let text = self.resolve_text(resolver);
         if text.len() < 25 {
-            return write!(target, " {:?}", text);
+            return write!(target, " {text:?}");
         }
 
         for idx in 21..25 {
             if text.is_char_boundary(idx) {
                 let text = format!("{} ...", &text[..idx]);
-                return write!(target, " {:?}", text);
+                return write!(target, " {text:?}");
             }
         }
         unreachable!()
diff --git a/cstree/tests/it/basic.rs b/cstree/tests/it/basic.rs
index c02fc3b..207bdab 100644
--- a/cstree/tests/it/basic.rs
+++ b/cstree/tests/it/basic.rs
@@ -149,18 +149,18 @@ fn inline_resolver() {
         let leaf1_0 = leaf1_0.into_token().unwrap();
         assert_eq!(leaf1_0.text(), "1.0");
         assert_eq!(leaf1_0.text_range(), TextRange::at(6.into(), 3.into()));
-        assert_eq!(format!("{}", leaf1_0), leaf1_0.text());
-        assert_eq!(format!("{:?}", leaf1_0), "SyntaxKind(5)@6..9 \"1.0\"");
+        assert_eq!(format!("{leaf1_0}"), leaf1_0.text());
+        assert_eq!(format!("{leaf1_0:?}"), "SyntaxKind(5)@6..9 \"1.0\"");
     }
     {
         let node2 = tree.children().nth(2).unwrap();
         assert_eq!(node2.text(), "2.02.12.2");
         let resolver = node2.resolver();
         assert_eq!(node2.resolve_text(resolver.as_ref()), node2.text());
-        assert_eq!(format!("{}", node2).as_str(), node2.text());
-        assert_eq!(format!("{:?}", node2), "SyntaxKind(6)@9..18");
+        assert_eq!(format!("{node2}").as_str(), node2.text());
+        assert_eq!(format!("{node2:?}"), "SyntaxKind(6)@9..18");
         assert_eq!(
-            format!("{:#?}", node2),
+            format!("{node2:#?}"),
             r#"SyntaxKind(6)@9..18
   SyntaxKind(7)@9..12 "2.0"
   SyntaxKind(8)@12..15 "2.1"