Reorganize syntax module

10 files changed, 336 insertions, 814 deletions

diff --git a/src/syntax/incremental.rs b/src/syntax/incremental.rs
index d5dea9d0..606daa2e 100644
--- a/src/syntax/incremental.rs
+++ b/src/syntax/incremental.rs
@@ -404,9 +404,23 @@ fn next_at_start(kind: &SyntaxKind, prev: bool) -> bool {
 #[cfg(test)]
 #[rustfmt::skip]
 mod tests {
+    use std::fmt::Debug;
+
     use super::*;
     use super::super::{parse, Source};
-    use super::super::tests::check;
+
+    #[track_caller]
+    fn check<T>(text: &str, found: T, expected: T)
+    where
+        T: Debug + PartialEq,
+    {
+        if found != expected {
+            println!("source:   {text:?}");
+            println!("expected: {expected:#?}");
+            println!("found:    {found:#?}");
+            panic!("test failed");
+        }
+    }
 
     #[track_caller]
     fn test(prev: &str, range: Range<usize>, with: &str, goal: Range<usize>) {
diff --git a/src/syntax/kind.rs b/src/syntax/kind.rs
index 54d5c81d..55f4b3ad 100644
--- a/src/syntax/kind.rs
+++ b/src/syntax/kind.rs
@@ -7,7 +7,7 @@ use crate::util::EcoString;
 
 /// All syntactical building blocks that can be part of a Typst document.
 ///
-/// Can be created by the tokenizer or by the parser.
+/// Can be created by the lexer or by the parser.
 #[derive(Debug, Clone, PartialEq)]
 pub enum SyntaxKind {
     /// A line comment: `// ...`.
diff --git a/src/syntax/tokens.rs b/src/syntax/lexer.rs
index 02bbd3a4..d5476774 100644
--- a/src/syntax/tokens.rs
+++ b/src/syntax/lexer.rs
@@ -9,13 +9,13 @@ use super::{ErrorPos, RawFields, SyntaxKind, Unit};
 use crate::geom::{AbsUnit, AngleUnit};
 use crate::util::{format_eco, EcoString};
 
-/// An iterator over the tokens of a string of source code.
+/// Splits up a string of source code into tokens.
 #[derive(Clone)]
-pub struct Tokens<'s> {
+pub struct Lexer<'s> {
     /// The underlying scanner.
     s: Scanner<'s>,
-    /// The mode the scanner is in. This determines what tokens it recognizes.
-    mode: TokenMode,
+    /// The mode the lexer is in. This determines what tokens it recognizes.
+    mode: LexMode,
     /// Whether the last token has been terminated.
     terminated: bool,
     /// Offsets the indentation on the first line of the source.
@@ -24,7 +24,7 @@ pub struct Tokens<'s> {
 
 /// What kind of tokens to emit.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
-pub enum TokenMode {
+pub enum LexMode {
     /// Text and markup.
     Markup,
     /// Math atoms, operators, etc.
@@ -33,15 +33,15 @@ pub enum TokenMode {
     Code,
 }
 
-impl<'s> Tokens<'s> {
-    /// Create a new token iterator with the given mode.
-    pub fn new(text: &'s str, mode: TokenMode) -> Self {
+impl<'s> Lexer<'s> {
+    /// Create a new lexer with the given mode.
+    pub fn new(text: &'s str, mode: LexMode) -> Self {
         Self::with_prefix("", text, mode)
     }
 
-    /// Create a new token iterator with the given mode and a prefix to offset
-    /// column calculations.
-    pub fn with_prefix(prefix: &str, text: &'s str, mode: TokenMode) -> Self {
+    /// Create a new lexer with the given mode and a prefix to offset column
+    /// calculations.
+    pub fn with_prefix(prefix: &str, text: &'s str, mode: LexMode) -> Self {
         Self {
             s: Scanner::new(text),
             mode,
@@ -50,13 +50,13 @@ impl<'s> Tokens<'s> {
         }
     }
 
-    /// Get the current token mode.
-    pub fn mode(&self) -> TokenMode {
+    /// Get the current lexing mode.
+    pub fn mode(&self) -> LexMode {
         self.mode
     }
 
-    /// Change the token mode.
-    pub fn set_mode(&mut self, mode: TokenMode) {
+    /// Change the lexing mode.
+    pub fn set_mode(&mut self, mode: LexMode) {
         self.mode = mode;
     }
 
@@ -87,10 +87,10 @@ impl<'s> Tokens<'s> {
     }
 }
 
-impl Iterator for Tokens<'_> {
+impl Iterator for Lexer<'_> {
     type Item = SyntaxKind;
 
-    /// Parse the next token in the source code.
+    /// Produce the next token.
     fn next(&mut self) -> Option<Self::Item> {
         let start = self.s.cursor();
         let c = self.s.eat()?;
@@ -106,16 +106,16 @@ impl Iterator for Tokens<'_> {
 
             // Other things.
             _ => match self.mode {
-                TokenMode::Markup => self.markup(start, c),
-                TokenMode::Math => self.math(start, c),
-                TokenMode::Code => self.code(start, c),
+                LexMode::Markup => self.markup(start, c),
+                LexMode::Math => self.math(start, c),
+                LexMode::Code => self.code(start, c),
             },
         })
     }
 }
 
 /// Shared.
-impl Tokens<'_> {
+impl Lexer<'_> {
     fn line_comment(&mut self) -> SyntaxKind {
         self.s.eat_until(is_newline);
         if self.s.peek().is_none() {
@@ -182,7 +182,7 @@ impl Tokens<'_> {
     }
 }
 
-impl Tokens<'_> {
+impl Lexer<'_> {
     fn markup(&mut self, start: usize, c: char) -> SyntaxKind {
         match c {
             // Blocks.
@@ -304,7 +304,7 @@ impl Tokens<'_> {
                 Some(keyword) => keyword,
                 None => SyntaxKind::Ident(read.into()),
             }
-        } else if self.mode == TokenMode::Markup {
+        } else if self.mode == LexMode::Markup {
             self.text(start)
         } else {
             SyntaxKind::Atom("#".into())
@@ -339,7 +339,7 @@ impl Tokens<'_> {
         if start < end {
             self.s.expect(':');
             SyntaxKind::Symbol(self.s.get(start..end).into())
-        } else if self.mode == TokenMode::Markup {
+        } else if self.mode == LexMode::Markup {
             SyntaxKind::Colon
         } else {
             SyntaxKind::Atom(":".into())
@@ -438,7 +438,7 @@ impl Tokens<'_> {
 }
 
 /// Math.
-impl Tokens<'_> {
+impl Lexer<'_> {
     fn math(&mut self, start: usize, c: char) -> SyntaxKind {
         match c {
             // Symbol shorthands.
@@ -507,7 +507,7 @@ impl Tokens<'_> {
 }
 
 /// Code.
-impl Tokens<'_> {
+impl Lexer<'_> {
     fn code(&mut self, start: usize, c: char) -> SyntaxKind {
         match c {
             // Blocks.
diff --git a/src/syntax/linked.rs b/src/syntax/linked.rs
index 2826835e..e69de29b 100644
--- a/src/syntax/linked.rs
+++ b/src/syntax/linked.rs
@@ -1,274 +0,0 @@
-use std::fmt::{self, Debug, Formatter};
-use std::ops::{Deref, Range};
-use std::rc::Rc;
-
-use super::{SyntaxKind, SyntaxNode};
-
-/// A syntax node in a context.
-///
-/// Knows its exact offset in the file and provides access to its
-/// children, parent and siblings.
-///
-/// **Note that all sibling and leaf accessors skip over trivia!**
-#[derive(Clone)]
-pub struct LinkedNode<'a> {
-    node: &'a SyntaxNode,
-    parent: Option<Rc<Self>>,
-    index: usize,
-    offset: usize,
-}
-
-impl<'a> LinkedNode<'a> {
-    /// Start a new traversal at the source's root node.
-    pub fn new(root: &'a SyntaxNode) -> Self {
-        Self { node: root, parent: None, index: 0, offset: 0 }
-    }
-
-    /// Get the contained syntax node.
-    pub fn get(&self) -> &'a SyntaxNode {
-        self.node
-    }
-
-    /// The index of this node in its parent's children list.
-    pub fn index(&self) -> usize {
-        self.index
-    }
-
-    /// The absolute byte offset of the this node in the source file.
-    pub fn offset(&self) -> usize {
-        self.offset
-    }
-
-    /// The byte range of the this node in the source file.
-    pub fn range(&self) -> Range<usize> {
-        self.offset..self.offset + self.node.len()
-    }
-
-    /// Get this node's children.
-    pub fn children(&self) -> LinkedChildren<'a> {
-        LinkedChildren {
-            parent: Rc::new(self.clone()),
-            iter: self.node.children().enumerate(),
-            front: self.offset,
-            back: self.offset + self.len(),
-        }
-    }
-}
-
-/// Access to parents and siblings.
-impl<'a> LinkedNode<'a> {
-    /// Get this node's parent.
-    pub fn parent(&self) -> Option<&Self> {
-        self.parent.as_deref()
-    }
-
-    /// Get the kind of this node's parent.
-    pub fn parent_kind(&self) -> Option<&'a SyntaxKind> {
-        Some(self.parent()?.node.kind())
-    }
-
-    /// Get the first previous non-trivia sibling node.
-    pub fn prev_sibling(&self) -> Option<Self> {
-        let parent = self.parent()?;
-        let index = self.index.checked_sub(1)?;
-        let node = parent.node.children().nth(index)?;
-        let offset = self.offset - node.len();
-        let prev = Self { node, parent: self.parent.clone(), index, offset };
-        if prev.kind().is_trivia() {
-            prev.prev_sibling()
-        } else {
-            Some(prev)
-        }
-    }
-
-    /// Get the next non-trivia sibling node.
-    pub fn next_sibling(&self) -> Option<Self> {
-        let parent = self.parent()?;
-        let index = self.index.checked_add(1)?;
-        let node = parent.node.children().nth(index)?;
-        let offset = self.offset + self.node.len();
-        let next = Self { node, parent: self.parent.clone(), index, offset };
-        if next.kind().is_trivia() {
-            next.next_sibling()
-        } else {
-            Some(next)
-        }
-    }
-}
-
-/// Access to leafs.
-impl<'a> LinkedNode<'a> {
-    /// Get the rightmost non-trivia leaf before this node.
-    pub fn prev_leaf(&self) -> Option<Self> {
-        let mut node = self.clone();
-        while let Some(prev) = node.prev_sibling() {
-            if let Some(leaf) = prev.rightmost_leaf() {
-                return Some(leaf);
-            }
-            node = prev;
-        }
-        self.parent()?.prev_leaf()
-    }
-
-    /// Find the leftmost contained non-trivia leaf.
-    pub fn leftmost_leaf(&self) -> Option<Self> {
-        if self.is_leaf() && !self.kind().is_trivia() && !self.kind().is_error() {
-            return Some(self.clone());
-        }
-
-        for child in self.children() {
-            if let Some(leaf) = child.leftmost_leaf() {
-                return Some(leaf);
-            }
-        }
-
-        None
-    }
-
-    /// Get the leaf at the specified cursor position.
-    pub fn leaf_at(&self, cursor: usize) -> Option<Self> {
-        if self.node.children().len() == 0 && cursor <= self.offset + self.len() {
-            return Some(self.clone());
-        }
-
-        let mut offset = self.offset;
-        let count = self.node.children().len();
-        for (i, child) in self.children().enumerate() {
-            let len = child.len();
-            if (offset < cursor && cursor <= offset + len)
-                || (offset == cursor && i + 1 == count)
-            {
-                return child.leaf_at(cursor);
-            }
-            offset += len;
-        }
-
-        None
-    }
-
-    /// Find the rightmost contained non-trivia leaf.
-    pub fn rightmost_leaf(&self) -> Option<Self> {
-        if self.is_leaf() && !self.kind().is_trivia() {
-            return Some(self.clone());
-        }
-
-        for child in self.children().rev() {
-            if let Some(leaf) = child.rightmost_leaf() {
-                return Some(leaf);
-            }
-        }
-
-        None
-    }
-
-    /// Get the leftmost non-trivia leaf after this node.
-    pub fn next_leaf(&self) -> Option<Self> {
-        let mut node = self.clone();
-        while let Some(next) = node.next_sibling() {
-            if let Some(leaf) = next.leftmost_leaf() {
-                return Some(leaf);
-            }
-            node = next;
-        }
-        self.parent()?.next_leaf()
-    }
-}
-
-impl Deref for LinkedNode<'_> {
-    type Target = SyntaxNode;
-
-    fn deref(&self) -> &Self::Target {
-        self.get()
-    }
-}
-
-impl Debug for LinkedNode<'_> {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        self.node.fmt(f)
-    }
-}
-
-/// An iterator over the children of a linked node.
-pub struct LinkedChildren<'a> {
-    parent: Rc<LinkedNode<'a>>,
-    iter: std::iter::Enumerate<std::slice::Iter<'a, SyntaxNode>>,
-    front: usize,
-    back: usize,
-}
-
-impl<'a> Iterator for LinkedChildren<'a> {
-    type Item = LinkedNode<'a>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        self.iter.next().map(|(index, node)| {
-            let offset = self.front;
-            self.front += node.len();
-            LinkedNode {
-                node,
-                parent: Some(self.parent.clone()),
-                index,
-                offset,
-            }
-        })
-    }
-
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        self.iter.size_hint()
-    }
-}
-
-impl DoubleEndedIterator for LinkedChildren<'_> {
-    fn next_back(&mut self) -> Option<Self::Item> {
-        self.iter.next_back().map(|(index, node)| {
-            self.back -= node.len();
-            LinkedNode {
-                node,
-                parent: Some(self.parent.clone()),
-                index,
-                offset: self.back,
-            }
-        })
-    }
-}
-
-impl ExactSizeIterator for LinkedChildren<'_> {}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use crate::syntax::Source;
-
-    #[test]
-    fn test_linked_node() {
-        let source = Source::detached("#set text(12pt, red)");
-
-        // Find "text".
-        let node = LinkedNode::new(source.root()).leaf_at(7).unwrap();
-        assert_eq!(node.offset(), 5);
-        assert_eq!(node.len(), 4);
-        assert_eq!(node.kind(), &SyntaxKind::Ident("text".into()));
-
-        // Go back to "#set". Skips the space.
-        let prev = node.prev_sibling().unwrap();
-        assert_eq!(prev.offset(), 0);
-        assert_eq!(prev.len(), 4);
-        assert_eq!(prev.kind(), &SyntaxKind::Set);
-    }
-
-    #[test]
-    fn test_linked_node_non_trivia_leaf() {
-        let source = Source::detached("#set fun(12pt, red)");
-        let leaf = LinkedNode::new(source.root()).leaf_at(6).unwrap();
-        let prev = leaf.prev_leaf().unwrap();
-        assert_eq!(leaf.kind(), &SyntaxKind::Ident("fun".into()));
-        assert_eq!(prev.kind(), &SyntaxKind::Set);
-
-        let source = Source::detached("#let x = 10");
-        let leaf = LinkedNode::new(source.root()).leaf_at(9).unwrap();
-        let prev = leaf.prev_leaf().unwrap();
-        let next = leaf.next_leaf().unwrap();
-        assert_eq!(prev.kind(), &SyntaxKind::Eq);
-        assert_eq!(leaf.kind(), &SyntaxKind::Space { newlines: 0 });
-        assert_eq!(next.kind(), &SyntaxKind::Int(10));
-    }
-}
diff --git a/src/syntax/mod.rs b/src/syntax/mod.rs
index 4f159b83..81524aa2 100644
--- a/src/syntax/mod.rs
+++ b/src/syntax/mod.rs
@@ -4,25 +4,20 @@ pub mod ast;
 
 mod incremental;
 mod kind;
-mod linked;
+mod lexer;
 mod node;
 mod parser;
 mod parsing;
 mod resolve;
 mod source;
 mod span;
-mod tokens;
 
 pub use self::kind::*;
-pub use self::linked::*;
+pub use self::lexer::*;
 pub use self::node::*;
 pub use self::parsing::*;
 pub use self::source::*;
 pub use self::span::*;
-pub use self::tokens::*;
 
 use incremental::reparse;
 use parser::*;
-
-#[cfg(test)]
-mod tests;
diff --git a/src/syntax/node.rs b/src/syntax/node.rs
index 62c07ffb..13556ede 100644
--- a/src/syntax/node.rs
+++ b/src/syntax/node.rs
@@ -1,5 +1,6 @@
 use std::fmt::{self, Debug, Display, Formatter};
-use std::ops::Range;
+use std::ops::{Deref, Range};
+use std::rc::Rc;
 use std::sync::Arc;
 
 use super::ast::AstNode;
@@ -526,6 +527,235 @@ impl PartialEq for NodeData {
     }
 }
 
+/// A syntax node in a context.
+///
+/// Knows its exact offset in the file and provides access to its
+/// children, parent and siblings.
+///
+/// **Note that all sibling and leaf accessors skip over trivia!**
+#[derive(Clone)]
+pub struct LinkedNode<'a> {
+    node: &'a SyntaxNode,
+    parent: Option<Rc<Self>>,
+    index: usize,
+    offset: usize,
+}
+
+impl<'a> LinkedNode<'a> {
+    /// Start a new traversal at the source's root node.
+    pub fn new(root: &'a SyntaxNode) -> Self {
+        Self { node: root, parent: None, index: 0, offset: 0 }
+    }
+
+    /// Get the contained syntax node.
+    pub fn get(&self) -> &'a SyntaxNode {
+        self.node
+    }
+
+    /// The index of this node in its parent's children list.
+    pub fn index(&self) -> usize {
+        self.index
+    }
+
+    /// The absolute byte offset of the this node in the source file.
+    pub fn offset(&self) -> usize {
+        self.offset
+    }
+
+    /// The byte range of the this node in the source file.
+    pub fn range(&self) -> Range<usize> {
+        self.offset..self.offset + self.node.len()
+    }
+
+    /// Get this node's children.
+    pub fn children(&self) -> LinkedChildren<'a> {
+        LinkedChildren {
+            parent: Rc::new(self.clone()),
+            iter: self.node.children().enumerate(),
+            front: self.offset,
+            back: self.offset + self.len(),
+        }
+    }
+}
+
+/// Access to parents and siblings.
+impl<'a> LinkedNode<'a> {
+    /// Get this node's parent.
+    pub fn parent(&self) -> Option<&Self> {
+        self.parent.as_deref()
+    }
+
+    /// Get the kind of this node's parent.
+    pub fn parent_kind(&self) -> Option<&'a SyntaxKind> {
+        Some(self.parent()?.node.kind())
+    }
+
+    /// Get the first previous non-trivia sibling node.
+    pub fn prev_sibling(&self) -> Option<Self> {
+        let parent = self.parent()?;
+        let index = self.index.checked_sub(1)?;
+        let node = parent.node.children().nth(index)?;
+        let offset = self.offset - node.len();
+        let prev = Self { node, parent: self.parent.clone(), index, offset };
+        if prev.kind().is_trivia() {
+            prev.prev_sibling()
+        } else {
+            Some(prev)
+        }
+    }
+
+    /// Get the next non-trivia sibling node.
+    pub fn next_sibling(&self) -> Option<Self> {
+        let parent = self.parent()?;
+        let index = self.index.checked_add(1)?;
+        let node = parent.node.children().nth(index)?;
+        let offset = self.offset + self.node.len();
+        let next = Self { node, parent: self.parent.clone(), index, offset };
+        if next.kind().is_trivia() {
+            next.next_sibling()
+        } else {
+            Some(next)
+        }
+    }
+}
+
+/// Access to leafs.
+impl<'a> LinkedNode<'a> {
+    /// Get the rightmost non-trivia leaf before this node.
+    pub fn prev_leaf(&self) -> Option<Self> {
+        let mut node = self.clone();
+        while let Some(prev) = node.prev_sibling() {
+            if let Some(leaf) = prev.rightmost_leaf() {
+                return Some(leaf);
+            }
+            node = prev;
+        }
+        self.parent()?.prev_leaf()
+    }
+
+    /// Find the leftmost contained non-trivia leaf.
+    pub fn leftmost_leaf(&self) -> Option<Self> {
+        if self.is_leaf() && !self.kind().is_trivia() && !self.kind().is_error() {
+            return Some(self.clone());
+        }
+
+        for child in self.children() {
+            if let Some(leaf) = child.leftmost_leaf() {
+                return Some(leaf);
+            }
+        }
+
+        None
+    }
+
+    /// Get the leaf at the specified cursor position.
+    pub fn leaf_at(&self, cursor: usize) -> Option<Self> {
+        if self.node.children().len() == 0 && cursor <= self.offset + self.len() {
+            return Some(self.clone());
+        }
+
+        let mut offset = self.offset;
+        let count = self.node.children().len();
+        for (i, child) in self.children().enumerate() {
+            let len = child.len();
+            if (offset < cursor && cursor <= offset + len)
+                || (offset == cursor && i + 1 == count)
+            {
+                return child.leaf_at(cursor);
+            }
+            offset += len;
+        }
+
+        None
+    }
+
+    /// Find the rightmost contained non-trivia leaf.
+    pub fn rightmost_leaf(&self) -> Option<Self> {
+        if self.is_leaf() && !self.kind().is_trivia() {
+            return Some(self.clone());
+        }
+
+        for child in self.children().rev() {
+            if let Some(leaf) = child.rightmost_leaf() {
+                return Some(leaf);
+            }
+        }
+
+        None
+    }
+
+    /// Get the leftmost non-trivia leaf after this node.
+    pub fn next_leaf(&self) -> Option<Self> {
+        let mut node = self.clone();
+        while let Some(next) = node.next_sibling() {
+            if let Some(leaf) = next.leftmost_leaf() {
+                return Some(leaf);
+            }
+            node = next;
+        }
+        self.parent()?.next_leaf()
+    }
+}
+
+impl Deref for LinkedNode<'_> {
+    type Target = SyntaxNode;
+
+    fn deref(&self) -> &Self::Target {
+        self.get()
+    }
+}
+
+impl Debug for LinkedNode<'_> {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        self.node.fmt(f)
+    }
+}
+
+/// An iterator over the children of a linked node.
+pub struct LinkedChildren<'a> {
+    parent: Rc<LinkedNode<'a>>,
+    iter: std::iter::Enumerate<std::slice::Iter<'a, SyntaxNode>>,
+    front: usize,
+    back: usize,
+}
+
+impl<'a> Iterator for LinkedChildren<'a> {
+    type Item = LinkedNode<'a>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.iter.next().map(|(index, node)| {
+            let offset = self.front;
+            self.front += node.len();
+            LinkedNode {
+                node,
+                parent: Some(self.parent.clone()),
+                index,
+                offset,
+            }
+        })
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+impl DoubleEndedIterator for LinkedChildren<'_> {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        self.iter.next_back().map(|(index, node)| {
+            self.back -= node.len();
+            LinkedNode {
+                node,
+                parent: Some(self.parent.clone()),
+                index,
+                offset: self.back,
+            }
+        })
+    }
+}
+
+impl ExactSizeIterator for LinkedChildren<'_> {}
+
 /// Result of numbering a node within an interval.
 pub(super) type NumberingResult = Result<(), Unnumberable>;
 
@@ -540,3 +770,43 @@ impl Display for Unnumberable {
 }
 
 impl std::error::Error for Unnumberable {}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::syntax::Source;
+
+    #[test]
+    fn test_linked_node() {
+        let source = Source::detached("#set text(12pt, red)");
+
+        // Find "text".
+        let node = LinkedNode::new(source.root()).leaf_at(7).unwrap();
+        assert_eq!(node.offset(), 5);
+        assert_eq!(node.len(), 4);
+        assert_eq!(node.kind(), &SyntaxKind::Ident("text".into()));
+
+        // Go back to "#set". Skips the space.
+        let prev = node.prev_sibling().unwrap();
+        assert_eq!(prev.offset(), 0);
+        assert_eq!(prev.len(), 4);
+        assert_eq!(prev.kind(), &SyntaxKind::Set);
+    }
+
+    #[test]
+    fn test_linked_node_non_trivia_leaf() {
+        let source = Source::detached("#set fun(12pt, red)");
+        let leaf = LinkedNode::new(source.root()).leaf_at(6).unwrap();
+        let prev = leaf.prev_leaf().unwrap();
+        assert_eq!(leaf.kind(), &SyntaxKind::Ident("fun".into()));
+        assert_eq!(prev.kind(), &SyntaxKind::Set);
+
+        let source = Source::detached("#let x = 10");
+        let leaf = LinkedNode::new(source.root()).leaf_at(9).unwrap();
+        let prev = leaf.prev_leaf().unwrap();
+        let next = leaf.next_leaf().unwrap();
+        assert_eq!(prev.kind(), &SyntaxKind::Eq);
+        assert_eq!(leaf.kind(), &SyntaxKind::Space { newlines: 0 });
+        assert_eq!(next.kind(), &SyntaxKind::Int(10));
+    }
+}
diff --git a/src/syntax/parser.rs b/src/syntax/parser.rs
index 74be792f..d2ef6e0e 100644
--- a/src/syntax/parser.rs
+++ b/src/syntax/parser.rs
@@ -2,13 +2,13 @@ use std::fmt::{self, Display, Formatter};
 use std::mem;
 use std::ops::Range;
 
-use super::{ErrorPos, SyntaxKind, SyntaxNode, TokenMode, Tokens};
+use super::{ErrorPos, LexMode, Lexer, SyntaxKind, SyntaxNode};
 use crate::util::{format_eco, EcoString};
 
 /// A convenient token-based parser.
 pub struct Parser<'s> {
     /// An iterator over the source tokens.
-    tokens: Tokens<'s>,
+    tokens: Lexer<'s>,
     /// Whether we are at the end of the file or of a group.
     eof: bool,
     /// The current token.
@@ -29,15 +29,15 @@ pub struct Parser<'s> {
 
 impl<'s> Parser<'s> {
     /// Create a new parser for the source string.
-    pub fn new(text: &'s str, mode: TokenMode) -> Self {
+    pub fn new(text: &'s str, mode: LexMode) -> Self {
         Self::with_prefix("", text, mode)
     }
 
     /// Create a new parser for the source string that is prefixed by some text
     /// that does not need to be parsed but taken into account for column
     /// calculation.
-    pub fn with_prefix(prefix: &str, text: &'s str, mode: TokenMode) -> Self {
-        let mut tokens = Tokens::with_prefix(prefix, text, mode);
+    pub fn with_prefix(prefix: &str, text: &'s str, mode: LexMode) -> Self {
+        let mut tokens = Lexer::with_prefix(prefix, text, mode);
         let current = tokens.next();
         Self {
             tokens,
@@ -91,7 +91,7 @@ impl<'s> Parser<'s> {
         let until = self.trivia_start();
         let mut children = mem::replace(&mut self.children, prev);
 
-        if self.tokens.mode() == TokenMode::Markup {
+        if self.tokens.mode() == LexMode::Markup {
             self.children.push(SyntaxNode::inner(kind, children));
         } else {
             // Trailing trivia should not be wrapped into the new node.
@@ -121,7 +121,7 @@ impl<'s> Parser<'s> {
         self.prev_end = self.tokens.cursor();
         self.bump();
 
-        if self.tokens.mode() != TokenMode::Markup {
+        if self.tokens.mode() != LexMode::Markup {
             // Skip whitespace and comments.
             while self.current.as_ref().map_or(false, |x| self.is_trivia(x)) {
                 self.bump();
@@ -235,9 +235,9 @@ impl<'s> Parser<'s> {
     pub fn start_group(&mut self, kind: Group) {
         self.groups.push(GroupEntry { kind, prev_mode: self.tokens.mode() });
         self.tokens.set_mode(match kind {
-            Group::Bracket | Group::Strong | Group::Emph => TokenMode::Markup,
-            Group::Math | Group::MathRow(_, _) => TokenMode::Math,
-            Group::Brace | Group::Paren | Group::Expr => TokenMode::Code,
+            Group::Bracket | Group::Strong | Group::Emph => LexMode::Markup,
+            Group::Math | Group::MathRow(_, _) => LexMode::Math,
+            Group::Brace | Group::Paren | Group::Expr => LexMode::Code,
         });
 
         match kind {
@@ -296,7 +296,7 @@ impl<'s> Parser<'s> {
         // Rescan the peeked token if the mode changed.
         if rescan {
             let mut target = self.prev_end();
-            if group_mode != TokenMode::Markup {
+            if group_mode != LexMode::Markup {
                 let start = self.trivia_start().0;
                 target = self.current_start
                     - self.children[start..].iter().map(SyntaxNode::len).sum::<usize>();
@@ -488,7 +488,7 @@ impl Marker {
             }
 
             // Don't expose trivia in code.
-            if p.tokens.mode() != TokenMode::Markup && child.kind().is_trivia() {
+            if p.tokens.mode() != LexMode::Markup && child.kind().is_trivia() {
                 continue;
             }
 
@@ -515,7 +515,7 @@ struct GroupEntry {
     pub kind: Group,
     /// The mode the parser was in _before_ the group started (to which we go
     /// back once the group ends).
-    pub prev_mode: TokenMode,
+    pub prev_mode: LexMode,
 }
 
 /// A group, confined by optional start and end delimiters.
diff --git a/src/syntax/parsing.rs b/src/syntax/parsing.rs
index 7f557fac..a6e6c861 100644
--- a/src/syntax/parsing.rs
+++ b/src/syntax/parsing.rs
@@ -2,21 +2,21 @@ use std::collections::HashSet;
 
 use super::ast::{Assoc, BinOp, UnOp};
 use super::{
-    ErrorPos, Group, Marker, ParseError, ParseResult, Parser, SyntaxKind, SyntaxNode,
-    TokenMode,
+    ErrorPos, Group, LexMode, Marker, ParseError, ParseResult, Parser, SyntaxKind,
+    SyntaxNode,
 };
 use crate::util::EcoString;
 
 /// Parse a source file.
 pub fn parse(text: &str) -> SyntaxNode {
-    let mut p = Parser::new(text, TokenMode::Markup);
+    let mut p = Parser::new(text, LexMode::Markup);
     markup(&mut p, true);
     p.finish().into_iter().next().unwrap()
 }
 
 /// Parse code directly, only used for syntax highlighting.
 pub fn parse_code(text: &str) -> SyntaxNode {
-    let mut p = Parser::new(text, TokenMode::Code);
+    let mut p = Parser::new(text, LexMode::Code);
     p.perform(SyntaxKind::CodeBlock, code);
     p.finish().into_iter().next().unwrap()
 }
@@ -29,7 +29,7 @@ pub(crate) fn reparse_code_block(
     text: &str,
     end_pos: usize,
 ) -> Option<(Vec<SyntaxNode>, bool, usize)> {
-    let mut p = Parser::with_prefix(prefix, text, TokenMode::Code);
+    let mut p = Parser::with_prefix(prefix, text, LexMode::Code);
     if !p.at(SyntaxKind::LeftBrace) {
         return None;
     }
@@ -53,7 +53,7 @@ pub(crate) fn reparse_content_block(
     text: &str,
     end_pos: usize,
 ) -> Option<(Vec<SyntaxNode>, bool, usize)> {
-    let mut p = Parser::with_prefix(prefix, text, TokenMode::Code);
+    let mut p = Parser::with_prefix(prefix, text, LexMode::Code);
     if !p.at(SyntaxKind::LeftBracket) {
         return None;
     }
@@ -81,7 +81,7 @@ pub(crate) fn reparse_markup_elements(
     mut at_start: bool,
     min_indent: usize,
 ) -> Option<(Vec<SyntaxNode>, bool, usize)> {
-    let mut p = Parser::with_prefix(prefix, text, TokenMode::Markup);
+    let mut p = Parser::with_prefix(prefix, text, LexMode::Markup);
 
     let mut node: Option<&SyntaxNode> = None;
     let mut iter = reference.iter();
diff --git a/src/syntax/tests.rs b/src/syntax/tests.rs
deleted file mode 100644
index 7b5dd870..00000000
--- a/src/syntax/tests.rs
+++ /dev/null
@@ -1,483 +0,0 @@
-#![allow(non_snake_case)]
-
-use std::num::NonZeroUsize;
-use std::sync::Arc;
-
-use super::*;
-use crate::geom::{AbsUnit, AngleUnit};
-
-use ErrorPos::*;
-use Option::None;
-use SyntaxKind::*;
-use TokenMode::{Code, Markup};
-
-use std::fmt::Debug;
-
-#[track_caller]
-pub fn check<T>(text: &str, found: T, expected: T)
-where
-    T: Debug + PartialEq,
-{
-    if found != expected {
-        println!("source:   {text:?}");
-        println!("expected: {expected:#?}");
-        println!("found:    {found:#?}");
-        panic!("test failed");
-    }
-}
-
-fn Space(newlines: usize) -> SyntaxKind {
-    SyntaxKind::Space { newlines }
-}
-
-fn Raw(text: &str, lang: Option<&str>, block: bool) -> SyntaxKind {
-    SyntaxKind::Raw(Arc::new(RawFields {
-        text: text.into(),
-        lang: lang.map(Into::into),
-        block,
-    }))
-}
-
-fn Str(string: &str) -> SyntaxKind {
-    SyntaxKind::Str(string.into())
-}
-
-fn Text(string: &str) -> SyntaxKind {
-    SyntaxKind::Text(string.into())
-}
-
-fn Ident(ident: &str) -> SyntaxKind {
-    SyntaxKind::Ident(ident.into())
-}
-
-fn Error(pos: ErrorPos, message: &str) -> SyntaxKind {
-    SyntaxKind::Error(pos, message.into())
-}
-
-/// Building blocks for suffix testing.
-///
-/// We extend each test case with a collection of different suffixes to make
-/// sure tokens end at the correct position. These suffixes are split into
-/// blocks, which can be disabled/enabled per test case. For example, when
-/// testing identifiers we disable letter suffixes because these would
-/// mingle with the identifiers.
-///
-/// Suffix blocks:
-/// - ' ': spacing
-/// - 'a': letters
-/// - '1': numbers
-/// - '/': symbols
-const BLOCKS: &str = " a1/";
-
-// Suffixes described by four-tuples of:
-//
-// - block the suffix is part of
-// - mode in which the suffix is applicable
-// - the suffix string
-// - the resulting suffix NodeKind
-fn suffixes() -> impl Iterator<Item = (char, Option<TokenMode>, &'static str, SyntaxKind)>
-{
-    [
-        // Whitespace suffixes.
-        (' ', None, " ", Space(0)),
-        (' ', None, "\n", Space(1)),
-        (' ', None, "\r", Space(1)),
-        (' ', None, "\r\n", Space(1)),
-        // Letter suffixes.
-        ('a', Some(Markup), "hello", Text("hello")),
-        ('a', Some(Markup), "💚", Text("💚")),
-        ('a', Some(Code), "val", Ident("val")),
-        ('a', Some(Code), "α", Ident("α")),
-        ('a', Some(Code), "_", Ident("_")),
-        // Number suffixes.
-        ('1', Some(Code), "2", Int(2)),
-        ('1', Some(Code), ".2", Float(0.2)),
-        // Symbol suffixes.
-        ('/', None, "[", LeftBracket),
-        ('/', None, "//", LineComment),
-        ('/', None, "/**/", BlockComment),
-        ('/', Some(Markup), "*", Star),
-        ('/', Some(Markup), r"\\", Escape('\\')),
-        ('/', Some(Markup), "#let", Let),
-        ('/', Some(Code), "(", LeftParen),
-        ('/', Some(Code), ":", Colon),
-        ('/', Some(Code), "+=", PlusEq),
-    ]
-    .into_iter()
-}
-
-macro_rules! t {
-    (Both $($tts:tt)*) => {
-        t!(Markup $($tts)*);
-        t!(Code $($tts)*);
-    };
-    ($mode:ident $([$blocks:literal])?: $text:expr => $($token:expr),*) => {{
-        // Test without suffix.
-        t!(@$mode: $text => $($token),*);
-
-        // Test with each applicable suffix.
-        for (block, mode, suffix, ref token) in suffixes() {
-            let text = $text;
-            #[allow(unused_variables)]
-            let blocks = BLOCKS;
-            $(let blocks = $blocks;)?
-            assert!(!blocks.contains(|c| !BLOCKS.contains(c)));
-            if (mode.is_none() || mode == Some($mode)) && blocks.contains(block) {
-                t!(@$mode: format!("{}{}", text, suffix) => $($token,)* token);
-            }
-        }
-    }};
-    (@$mode:ident: $text:expr => $($token:expr),*) => {{
-        let text = $text;
-        let found = Tokens::new(&text, $mode).collect::<Vec<_>>();
-        let expected = vec![$($token.clone()),*];
-        check(&text, found, expected);
-    }};
-}
-
-#[test]
-fn test_tokenize_brackets() {
-    // Test in markup.
-    t!(Markup: "{"       => LeftBrace);
-    t!(Markup: "}"       => RightBrace);
-    t!(Markup: "["       => LeftBracket);
-    t!(Markup: "]"       => RightBracket);
-    t!(Markup[" /"]: "(" => Text("("));
-    t!(Markup[" /"]: ")" => Text(")"));
-
-    // Test in code.
-    t!(Code: "{" => LeftBrace);
-    t!(Code: "}" => RightBrace);
-    t!(Code: "[" => LeftBracket);
-    t!(Code: "]" => RightBracket);
-    t!(Code: "(" => LeftParen);
-    t!(Code: ")" => RightParen);
-}
-
-#[test]
-fn test_tokenize_whitespace() {
-    // Test basic whitespace.
-    t!(Both["a1/"]: ""         => );
-    t!(Both["a1/"]: " "        => Space(0));
-    t!(Both["a1/"]: "    "     => Space(0));
-    t!(Both["a1/"]: "\t"       => Space(0));
-    t!(Both["a1/"]: "  \t"     => Space(0));
-    t!(Both["a1/"]: "\u{202F}" => Space(0));
-
-    // Test newline counting.
-    t!(Both["a1/"]: "\n"           => Space(1));
-    t!(Both["a1/"]: "\n "          => Space(1));
-    t!(Both["a1/"]: "  \n"         => Space(1));
-    t!(Both["a1/"]: "  \n   "      => Space(1));
-    t!(Both["a1/"]: "\r\n"         => Space(1));
-    t!(Both["a1/"]: "\r\n\r"       => Space(2));
-    t!(Both["a1/"]: "  \n\t \n  "  => Space(2));
-    t!(Both["a1/"]: "\n\r"         => Space(2));
-    t!(Both["a1/"]: " \r\r\n \x0D" => Space(3));
-}
-
-#[test]
-fn test_tokenize_text() {
-    // Test basic text.
-    t!(Markup[" /"]: "hello"      => Text("hello"));
-    t!(Markup[" /"]: "reha-world" => Text("reha-world"));
-
-    // Test code symbols in text.
-    t!(Markup[" /"]: "a():\"b" => Text("a()"), Colon, SmartQuote { double: true }, Text("b"));
-    t!(Markup[" /"]: ";,|/+"  => Text(";,|/+"));
-    t!(Markup[" /"]: "=-a"     => Eq, Minus, Text("a"));
-    t!(Markup[" "]: "#123"     => Text("#123"));
-
-    // Test text ends.
-    t!(Markup[""]: "hello " => Text("hello"), Space(0));
-    t!(Markup[""]: "hello~" => Text("hello"), Shorthand('\u{00A0}'));
-}
-
-#[test]
-fn test_tokenize_escape_sequences() {
-    // Test escapable symbols.
-    t!(Markup: r"\\" => Escape('\\'));
-    t!(Markup: r"\/" => Escape('/'));
-    t!(Markup: r"\[" => Escape('['));
-    t!(Markup: r"\]" => Escape(']'));
-    t!(Markup: r"\{" => Escape('{'));
-    t!(Markup: r"\}" => Escape('}'));
-    t!(Markup: r"\*" => Escape('*'));
-    t!(Markup: r"\_" => Escape('_'));
-    t!(Markup: r"\=" => Escape('='));
-    t!(Markup: r"\~" => Escape('~'));
-    t!(Markup: r"\'" => Escape('\''));
-    t!(Markup: r#"\""# => Escape('"'));
-    t!(Markup: r"\`" => Escape('`'));
-    t!(Markup: r"\$" => Escape('$'));
-    t!(Markup: r"\#" => Escape('#'));
-    t!(Markup: r"\a"   => Escape('a'));
-    t!(Markup: r"\u"   => Escape('u'));
-    t!(Markup: r"\1"   => Escape('1'));
-
-    // Test basic unicode escapes.
-    t!(Markup: r"\u{}"     => Error(Full, "invalid unicode escape sequence"));
-    t!(Markup: r"\u{2603}" => Escape('☃'));
-    t!(Markup: r"\u{P}"    => Error(Full, "invalid unicode escape sequence"));
-
-    // Test unclosed unicode escapes.
-    t!(Markup[" /"]: r"\u{"     => Error(End, "expected closing brace"));
-    t!(Markup[" /"]: r"\u{1"    => Error(End, "expected closing brace"));
-    t!(Markup[" /"]: r"\u{26A4" => Error(End, "expected closing brace"));
-    t!(Markup[" /"]: r"\u{1Q3P" => Error(End, "expected closing brace"));
-    t!(Markup: r"\u{1🏕}"       => Error(End, "expected closing brace"), Text("🏕"), RightBrace);
-}
-
-#[test]
-fn test_tokenize_markup_symbols() {
-    // Test markup tokens.
-    t!(Markup[" a1"]: "*"   => Star);
-    t!(Markup: "_"          => Underscore);
-    t!(Markup[""]: "==="    => Eq, Eq, Eq);
-    t!(Markup["a1/"]: "= "  => Eq, Space(0));
-    t!(Markup[" "]: r"\"    => Linebreak);
-    t!(Markup: "~"          => Shorthand('\u{00A0}'));
-    t!(Markup["a1/"]: "-?"  => Shorthand('\u{00AD}'));
-    t!(Markup["a "]: r"a--" => Text("a"), Shorthand('\u{2013}'));
-    t!(Markup["a1/"]: "- "  => Minus, Space(0));
-    t!(Markup[" "]: "+"     => Plus);
-    t!(Markup[" "]: "1."    => EnumNumbering(NonZeroUsize::new(1).unwrap()));
-    t!(Markup[" "]: "1.a"   => EnumNumbering(NonZeroUsize::new(1).unwrap()), Text("a"));
-    t!(Markup[" /"]: "a1."  => Text("a1."));
-}
-
-#[test]
-fn test_tokenize_code_symbols() {
-    // Test all symbols.
-    t!(Code: ","        => Comma);
-    t!(Code: ";"        => Semicolon);
-    t!(Code: ":"        => Colon);
-    t!(Code: "+"        => Plus);
-    t!(Code: "-"        => Minus);
-    t!(Code[" a1"]: "*" => Star);
-    t!(Code[" a1"]: "/" => Slash);
-    t!(Code[" a/"]: "." => Dot);
-    t!(Code: "="        => Eq);
-    t!(Code: "=="       => EqEq);
-    t!(Code: "!="       => ExclEq);
-    t!(Code[" /"]: "<"  => Lt);
-    t!(Code: "<="       => LtEq);
-    t!(Code: ">"        => Gt);
-    t!(Code: ">="       => GtEq);
-    t!(Code: "+="       => PlusEq);
-    t!(Code: "-="       => HyphEq);
-    t!(Code: "*="       => StarEq);
-    t!(Code: "/="       => SlashEq);
-    t!(Code: ".."       => Dots);
-    t!(Code: "=>"       => Arrow);
-
-    // Test combinations.
-    t!(Code: "<=>"        => LtEq, Gt);
-    t!(Code[" a/"]: "..." => Dots, Dot);
-
-    // Test hyphen as symbol vs part of identifier.
-    t!(Code[" /"]: "-1"   => Minus, Int(1));
-    t!(Code[" /"]: "-a"   => Minus, Ident("a"));
-    t!(Code[" /"]: "--1"  => Minus, Minus, Int(1));
-    t!(Code[" /"]: "--_a" => Minus, Minus, Ident("_a"));
-    t!(Code[" /"]: "a-b"  => Ident("a-b"));
-
-    // Test invalid.
-    t!(Code: r"\" => Error(Full, "not valid here"));
-}
-
-#[test]
-fn test_tokenize_keywords() {
-    // A list of a few (not all) keywords.
-    let list = [
-        ("not", Not),
-        ("let", Let),
-        ("if", If),
-        ("else", Else),
-        ("for", For),
-        ("in", In),
-        ("import", Import),
-    ];
-
-    for (s, t) in list.clone() {
-        t!(Markup[" "]: format!("#{}", s) => t);
-        t!(Markup[" "]: format!("#{0}#{0}", s) => t, t);
-        t!(Markup[" /"]: format!("# {}", s) => Text(&format!("# {s}")));
-    }
-
-    for (s, t) in list {
-        t!(Code[" "]: s => t);
-        t!(Markup[" /"]: s => Text(s));
-    }
-
-    // Test simple identifier.
-    t!(Markup[" "]: "#letter" => Ident("letter"));
-    t!(Code[" /"]: "falser"   => Ident("falser"));
-    t!(Code[" /"]: "None"     => Ident("None"));
-    t!(Code[" /"]: "True"     => Ident("True"));
-}
-
-#[test]
-fn test_tokenize_raw_blocks() {
-    // Test basic raw block.
-    t!(Markup: "``"     => Raw("", None, false));
-    t!(Markup: "`raw`"  => Raw("raw", None, false));
-    t!(Markup[""]: "`]" => Error(End, "expected 1 backtick"));
-
-    // Test special symbols in raw block.
-    t!(Markup: "`[brackets]`" => Raw("[brackets]", None, false));
-    t!(Markup[""]: r"`\`` "   => Raw(r"\", None, false), Error(End, "expected 1 backtick"));
-
-    // Test separated closing backticks.
-    t!(Markup: "```not `y`e`t```" => Raw("`y`e`t", Some("not"), false));
-
-    // Test more backticks.
-    t!(Markup: "``nope``"             => Raw("", None, false), Text("nope"), Raw("", None, false));
-    t!(Markup: "````🚀````"           => Raw("", None, false));
-    t!(Markup[""]: "`````👩‍🚀````noend" => Error(End, "expected 5 backticks"));
-    t!(Markup[""]: "````raw``````"    => Raw("", Some("raw"), false), Raw("", None, false));
-}
-
-#[test]
-fn test_tokenize_idents() {
-    // Test valid identifiers.
-    t!(Code[" /"]: "x"           => Ident("x"));
-    t!(Code[" /"]: "value"       => Ident("value"));
-    t!(Code[" /"]: "__main__"    => Ident("__main__"));
-    t!(Code[" /"]: "_snake_case" => Ident("_snake_case"));
-
-    // Test non-ascii.
-    t!(Code[" /"]: "α"    => Ident("α"));
-    t!(Code[" /"]: "ម្តាយ" => Ident("ម្តាយ"));
-
-    // Test hyphen parsed as identifier.
-    t!(Code[" /"]: "kebab-case" => Ident("kebab-case"));
-    t!(Code[" /"]: "one-10"     => Ident("one-10"));
-}
-
-#[test]
-fn test_tokenize_numeric() {
-    let ints = [("7", 7), ("012", 12)];
-    let floats = [
-        (".3", 0.3),
-        ("0.3", 0.3),
-        ("3.", 3.0),
-        ("3.0", 3.0),
-        ("14.3", 14.3),
-        ("10e2", 1000.0),
-        ("10e+0", 10.0),
-        ("10e+1", 100.0),
-        ("10e-2", 0.1),
-        ("10.e1", 100.0),
-        ("10.e-1", 1.0),
-        (".1e1", 1.0),
-        ("10E2", 1000.0),
-    ];
-
-    // Test integers.
-    for &(s, v) in &ints {
-        t!(Code[" /"]: s => Int(v));
-    }
-
-    // Test floats.
-    for &(s, v) in &floats {
-        t!(Code[" /"]: s => Float(v));
-    }
-
-    // Test attached numbers.
-    t!(Code[" /"]: ".2.3"  => Float(0.2), Float(0.3));
-    t!(Code[" /"]: "1.2.3"  => Float(1.2), Float(0.3));
-    t!(Code[" /"]: "1e-2+3" => Float(0.01), Plus, Int(3));
-
-    // Test float from too large integer.
-    let large = i64::MAX as f64 + 1.0;
-    t!(Code[" /"]: large.to_string() => Float(large));
-
-    // Combined integers and floats.
-    let nums = ints.iter().map(|&(k, v)| (k, v as f64)).chain(floats);
-
-    let suffixes: &[(&str, fn(f64) -> SyntaxKind)] = &[
-        ("mm", |x| Numeric(x, Unit::Length(AbsUnit::Mm))),
-        ("pt", |x| Numeric(x, Unit::Length(AbsUnit::Pt))),
-        ("cm", |x| Numeric(x, Unit::Length(AbsUnit::Cm))),
-        ("in", |x| Numeric(x, Unit::Length(AbsUnit::In))),
-        ("rad", |x| Numeric(x, Unit::Angle(AngleUnit::Rad))),
-        ("deg", |x| Numeric(x, Unit::Angle(AngleUnit::Deg))),
-        ("em", |x| Numeric(x, Unit::Em)),
-        ("fr", |x| Numeric(x, Unit::Fr)),
-        ("%", |x| Numeric(x, Unit::Percent)),
-    ];
-
-    // Numeric types.
-    for &(suffix, build) in suffixes {
-        for (s, v) in nums.clone() {
-            t!(Code[" /"]: format!("{}{}", s, suffix) => build(v));
-        }
-    }
-
-    // Multiple dots close the number.
-    t!(Code[" /"]: "1..2"   => Int(1), Dots, Int(2));
-    t!(Code[" /"]: "1..2.3" => Int(1), Dots, Float(2.3));
-    t!(Code[" /"]: "1.2..3" => Float(1.2), Dots, Int(3));
-
-    // Test invalid.
-    t!(Code[" /"]: "1foo" => Error(Full, "invalid number suffix"));
-}
-
-#[test]
-fn test_tokenize_strings() {
-    // Test basic strings.
-    t!(Code: "\"hi\""        => Str("hi"));
-    t!(Code: "\"hi\nthere\"" => Str("hi\nthere"));
-    t!(Code: "\"🌎\""        => Str("🌎"));
-
-    // Test unterminated.
-    t!(Code[""]: "\"hi" => Error(End, "expected quote"));
-
-    // Test escaped quote.
-    t!(Code: r#""a\"bc""# => Str("a\"bc"));
-    t!(Code[""]: r#""\""# => Error(End, "expected quote"));
-}
-
-#[test]
-fn test_tokenize_line_comments() {
-    // Test line comment with no trailing newline.
-    t!(Both[""]: "//" => LineComment);
-
-    // Test line comment ends at newline.
-    t!(Both["a1/"]: "//bc\n"   => LineComment, Space(1));
-    t!(Both["a1/"]: "// bc \n" => LineComment, Space(1));
-    t!(Both["a1/"]: "//bc\r\n" => LineComment, Space(1));
-
-    // Test nested line comments.
-    t!(Both["a1/"]: "//a//b\n" => LineComment, Space(1));
-}
-
-#[test]
-fn test_tokenize_block_comments() {
-    // Test basic block comments.
-    t!(Both[""]: "/*" => BlockComment);
-    t!(Both: "/**/"   => BlockComment);
-    t!(Both: "/*🏞*/" => BlockComment);
-    t!(Both: "/*\n*/" => BlockComment);
-
-    // Test depth 1 and 2 nested block comments.
-    t!(Both: "/* /* */ */"  => BlockComment);
-    t!(Both: "/*/*/**/*/*/" => BlockComment);
-
-    // Test two nested, one unclosed block comments.
-    t!(Both[""]: "/*/*/**/*/" => BlockComment);
-
-    // Test all combinations of up to two following slashes and stars.
-    t!(Both[""]: "/*"   => BlockComment);
-    t!(Both[""]: "/*/"  => BlockComment);
-    t!(Both[""]: "/**"  => BlockComment);
-    t!(Both[""]: "/*//" => BlockComment);
-    t!(Both[""]: "/*/*" => BlockComment);
-    t!(Both[""]: "/**/" => BlockComment);
-    t!(Both[""]: "/***" => BlockComment);
-
-    // Test unexpected terminator.
-    t!(Both: "/*Hi*/*/" => BlockComment,
-        Error(Full, "unexpected end of block comment"));
-}
diff --git a/src/util/eco.rs b/src/util/eco.rs
index 8f519504..dccb68a8 100644
--- a/src/util/eco.rs
+++ b/src/util/eco.rs
@@ -46,7 +46,7 @@ const LIMIT: usize = 14;
 
 impl EcoString {
     /// Create a new, empty string.
-    pub fn new() -> Self {
+    pub const fn new() -> Self {
         Self(Repr::Small { buf: [0; LIMIT], len: 0 })
     }