Reorganize ast types 🏕

17 files changed, 554 insertions, 447 deletions

diff --git a/src/compute/dict.rs b/src/compute/dict.rs
index e4df0048..e6216572 100644
--- a/src/compute/dict.rs
+++ b/src/compute/dict.rs
@@ -52,38 +52,38 @@ impl<V> Dict<V> {
     /// Get a reference to the value with the given key.
     pub fn get<'a, K>(&self, key: K) -> Option<&V>
     where
-        K: Into<BorrowedKey<'a>>,
+        K: Into<RefKey<'a>>,
     {
         match key.into() {
-            BorrowedKey::Num(num) => self.nums.get(&num),
-            BorrowedKey::Str(string) => self.strs.get(string),
+            RefKey::Num(num) => self.nums.get(&num),
+            RefKey::Str(string) => self.strs.get(string),
         }
     }
 
     /// Borrow the value with the given key mutably.
     pub fn get_mut<'a, K>(&mut self, key: K) -> Option<&mut V>
     where
-        K: Into<BorrowedKey<'a>>,
+        K: Into<RefKey<'a>>,
     {
         match key.into() {
-            BorrowedKey::Num(num) => self.nums.get_mut(&num),
-            BorrowedKey::Str(string) => self.strs.get_mut(string),
+            RefKey::Num(num) => self.nums.get_mut(&num),
+            RefKey::Str(string) => self.strs.get_mut(string),
         }
     }
 
     /// Insert a value into the dictionary.
     pub fn insert<K>(&mut self, key: K, value: V)
     where
-        K: Into<OwnedKey>,
+        K: Into<DictKey>,
     {
         match key.into() {
-            OwnedKey::Num(num) => {
+            DictKey::Num(num) => {
                 self.nums.insert(num, value);
                 if self.lowest_free == num {
                     self.lowest_free += 1;
                 }
             }
-            OwnedKey::Str(string) => {
+            DictKey::Str(string) => {
                 self.strs.insert(string, value);
             }
         }
@@ -92,14 +92,14 @@ impl<V> Dict<V> {
     /// Remove the value with the given key from the dictionary.
     pub fn remove<'a, K>(&mut self, key: K) -> Option<V>
     where
-        K: Into<BorrowedKey<'a>>,
+        K: Into<RefKey<'a>>,
     {
         match key.into() {
-            BorrowedKey::Num(num) => {
+            RefKey::Num(num) => {
                 self.lowest_free = self.lowest_free.min(num);
                 self.nums.remove(&num)
             }
-            BorrowedKey::Str(string) => self.strs.remove(string),
+            RefKey::Str(string) => self.strs.remove(string),
         }
     }
 
@@ -116,10 +116,10 @@ impl<V> Dict<V> {
     }
 
     /// Iterator over all borrowed keys and values.
-    pub fn iter(&self) -> impl Iterator<Item = (BorrowedKey, &V)> {
+    pub fn iter(&self) -> impl Iterator<Item = (RefKey, &V)> {
         self.nums()
-            .map(|(&k, v)| (BorrowedKey::Num(k), v))
-            .chain(self.strs().map(|(k, v)| (BorrowedKey::Str(k), v)))
+            .map(|(&k, v)| (RefKey::Num(k), v))
+            .chain(self.strs().map(|(k, v)| (RefKey::Str(k), v)))
     }
 
     /// Iterate over all values in the dictionary.
@@ -138,11 +138,11 @@ impl<V> Dict<V> {
     }
 
     /// Move into an owned iterator over owned keys and values.
-    pub fn into_iter(self) -> impl Iterator<Item = (OwnedKey, V)> {
+    pub fn into_iter(self) -> impl Iterator<Item = (DictKey, V)> {
         self.nums
             .into_iter()
-            .map(|(k, v)| (OwnedKey::Num(k), v))
-            .chain(self.strs.into_iter().map(|(k, v)| (OwnedKey::Str(k), v)))
+            .map(|(k, v)| (DictKey::Num(k), v))
+            .chain(self.strs.into_iter().map(|(k, v)| (DictKey::Str(k), v)))
     }
 
     /// Move into an owned iterator over all values in the dictionary.
@@ -166,7 +166,7 @@ impl<V> Dict<V> {
 
 impl<'a, K, V> Index<K> for Dict<V>
 where
-    K: Into<BorrowedKey<'a>>,
+    K: Into<RefKey<'a>>,
 {
     type Output = V;
 
@@ -230,33 +230,39 @@ impl<V: Debug> Debug for Dict<V> {
 
 /// The owned variant of a dictionary key.
 #[derive(Debug, Clone, Eq, PartialEq, Ord, PartialOrd)]
-pub enum OwnedKey {
+pub enum DictKey {
     Num(u64),
     Str(String),
 }
 
-impl From<BorrowedKey<'_>> for OwnedKey {
-    fn from(key: BorrowedKey<'_>) -> Self {
+impl From<&Self> for DictKey {
+    fn from(key: &Self) -> Self {
+        key.clone()
+    }
+}
+
+impl From<RefKey<'_>> for DictKey {
+    fn from(key: RefKey<'_>) -> Self {
         match key {
-            BorrowedKey::Num(num) => Self::Num(num),
-            BorrowedKey::Str(string) => Self::Str(string.to_string()),
+            RefKey::Num(num) => Self::Num(num),
+            RefKey::Str(string) => Self::Str(string.to_string()),
         }
     }
 }
 
-impl From<u64> for OwnedKey {
+impl From<u64> for DictKey {
     fn from(num: u64) -> Self {
         Self::Num(num)
     }
 }
 
-impl From<String> for OwnedKey {
+impl From<String> for DictKey {
     fn from(string: String) -> Self {
         Self::Str(string)
     }
 }
 
-impl From<&'static str> for OwnedKey {
+impl From<&'static str> for DictKey {
     fn from(string: &'static str) -> Self {
         Self::Str(string.to_string())
     }
@@ -264,24 +270,24 @@ impl From<&'static str> for OwnedKey {
 
 /// The borrowed variant of a dictionary key.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd)]
-pub enum BorrowedKey<'a> {
+pub enum RefKey<'a> {
     Num(u64),
     Str(&'a str),
 }
 
-impl From<u64> for BorrowedKey<'static> {
+impl From<u64> for RefKey<'static> {
     fn from(num: u64) -> Self {
         Self::Num(num)
     }
 }
 
-impl<'a> From<&'a String> for BorrowedKey<'a> {
+impl<'a> From<&'a String> for RefKey<'a> {
     fn from(string: &'a String) -> Self {
         Self::Str(&string)
     }
 }
 
-impl<'a> From<&'a str> for BorrowedKey<'a> {
+impl<'a> From<&'a str> for RefKey<'a> {
     fn from(string: &'a str) -> Self {
         Self::Str(string)
     }
diff --git a/src/compute/value.rs b/src/compute/value.rs
index 1fcc4be2..cfbc302c 100644
--- a/src/compute/value.rs
+++ b/src/compute/value.rs
@@ -11,7 +11,7 @@ use crate::color::RgbaColor;
 use crate::layout::{Command, Commands, Dir, LayoutContext, SpecAlign};
 use crate::length::{Length, ScaleLength};
 use crate::paper::Paper;
-use crate::syntax::{Ident, Span, SpanWith, Spanned, SyntaxNode, SyntaxTree};
+use crate::syntax::{Ident, Span, SpanWith, Spanned, SynNode, SynTree};
 use crate::{DynFuture, Feedback, Pass};
 
 /// A computational value.
@@ -32,7 +32,7 @@ pub enum Value {
     /// A dictionary value: `(false, 12cm, greeting="hi")`.
     Dict(DictValue),
     /// A syntax tree containing typesetting content.
-    Tree(SyntaxTree),
+    Tree(SynTree),
     /// An executable function.
     Func(FuncValue),
     /// Layouting commands.
@@ -76,7 +76,7 @@ impl Spanned<Value> {
                 for entry in dict.into_values() {
                     if let Some(last_end) = end {
                         let span = Span::new(last_end, entry.key.start);
-                        let tree = vec![SyntaxNode::Spacing.span_with(span)];
+                        let tree = vec![SynNode::Spacing.span_with(span)];
                         commands.push(Command::LayoutSyntaxTree(tree));
                     }
 
@@ -89,7 +89,7 @@ impl Spanned<Value> {
             // Format with debug.
             val => {
                 let fmt = format!("{:?}", val);
-                let tree = vec![SyntaxNode::Text(fmt).span_with(self.span)];
+                let tree = vec![SynNode::Text(fmt).span_with(self.span)];
                 vec![Command::LayoutSyntaxTree(tree)]
             }
         }
@@ -340,7 +340,7 @@ impl_match!(String, "string", Value::Str(s) => s.clone());
 impl_match!(bool, "bool", &Value::Bool(b) => b);
 impl_match!(f64, "number", &Value::Number(n) => n);
 impl_match!(Length, "length", &Value::Length(l) => l);
-impl_match!(SyntaxTree, "tree", Value::Tree(t) => t.clone());
+impl_match!(SynTree, "tree", Value::Tree(t) => t.clone());
 impl_match!(DictValue, "dict", Value::Dict(t) => t.clone());
 impl_match!(FuncValue, "function", Value::Func(f) => f.clone());
 impl_match!(ScaleLength, "number or length",
diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index c053cda0..768ff160 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -25,7 +25,7 @@ use crate::compute::scope::Scope;
 use crate::font::SharedFontLoader;
 use crate::geom::{Margins, Size};
 use crate::style::{LayoutStyle, PageStyle, TextStyle};
-use crate::syntax::SyntaxTree;
+use crate::syntax::SynTree;
 
 use elements::LayoutElements;
 use prelude::*;
@@ -121,7 +121,7 @@ pub enum Command {
     /// This has the effect that the content fits nicely into the active line
     /// layouting, enabling functions to e.g. change the style of some piece of
     /// text while keeping it part of the current paragraph.
-    LayoutSyntaxTree(SyntaxTree),
+    LayoutSyntaxTree(SynTree),
 
     /// Add a finished layout.
     Add(BoxLayout),
diff --git a/src/layout/tree.rs b/src/layout/tree.rs
index 24a00367..14ff4630 100644
--- a/src/layout/tree.rs
+++ b/src/layout/tree.rs
@@ -5,12 +5,12 @@ use super::text::{layout_text, TextContext};
 use super::*;
 use crate::style::LayoutStyle;
 use crate::syntax::{
-    CallExpr, Decoration, Heading, Raw, Span, SpanWith, Spanned, SyntaxNode, SyntaxTree,
+    Decoration, Expr, NodeHeading, NodeRaw, Span, SpanWith, Spanned, SynNode, SynTree,
 };
 use crate::{DynFuture, Feedback, Pass};
 
 /// Layout a syntax tree into a collection of boxes.
-pub async fn layout_tree(tree: &SyntaxTree, ctx: LayoutContext<'_>) -> Pass<MultiLayout> {
+pub async fn layout_tree(tree: &SynTree, ctx: LayoutContext<'_>) -> Pass<MultiLayout> {
     let mut layouter = TreeLayouter::new(ctx);
     layouter.layout_tree(tree).await;
     layouter.finish()
@@ -44,7 +44,7 @@ impl<'a> TreeLayouter<'a> {
         Pass::new(self.layouter.finish(), self.feedback)
     }
 
-    fn layout_tree<'t>(&'t mut self, tree: &'t SyntaxTree) -> DynFuture<'t, ()> {
+    fn layout_tree<'t>(&'t mut self, tree: &'t SynTree) -> DynFuture<'t, ()> {
         Box::pin(async move {
             for node in tree {
                 self.layout_node(node).await;
@@ -52,26 +52,26 @@ impl<'a> TreeLayouter<'a> {
         })
     }
 
-    async fn layout_node(&mut self, node: &Spanned<SyntaxNode>) {
+    async fn layout_node(&mut self, node: &Spanned<SynNode>) {
         let decorate = |this: &mut Self, deco: Decoration| {
             this.feedback.decorations.push(deco.span_with(node.span));
         };
 
         match &node.v {
-            SyntaxNode::Spacing => self.layout_space(),
-            SyntaxNode::Linebreak => self.layouter.finish_line(),
-            SyntaxNode::Parbreak => self.layout_parbreak(),
+            SynNode::Spacing => self.layout_space(),
+            SynNode::Linebreak => self.layouter.finish_line(),
+            SynNode::Parbreak => self.layout_parbreak(),
 
-            SyntaxNode::ToggleItalic => {
+            SynNode::ToggleItalic => {
                 self.style.text.italic = !self.style.text.italic;
                 decorate(self, Decoration::Italic);
             }
-            SyntaxNode::ToggleBolder => {
+            SynNode::ToggleBolder => {
                 self.style.text.bolder = !self.style.text.bolder;
                 decorate(self, Decoration::Bold);
             }
 
-            SyntaxNode::Text(text) => {
+            SynNode::Text(text) => {
                 if self.style.text.italic {
                     decorate(self, Decoration::Italic);
                 }
@@ -81,12 +81,11 @@ impl<'a> TreeLayouter<'a> {
                 self.layout_text(text).await;
             }
 
-            SyntaxNode::Heading(heading) => self.layout_heading(heading).await,
+            SynNode::Raw(raw) => self.layout_raw(raw).await,
+            SynNode::Heading(heading) => self.layout_heading(heading).await,
 
-            SyntaxNode::Raw(raw) => self.layout_raw(raw).await,
-
-            SyntaxNode::Call(call) => {
-                self.layout_call(call.span_with(node.span)).await;
+            SynNode::Expr(expr) => {
+                self.layout_expr(expr.span_with(node.span)).await;
             }
         }
     }
@@ -115,19 +114,19 @@ impl<'a> TreeLayouter<'a> {
         );
     }
 
-    async fn layout_heading(&mut self, heading: &Heading) {
+    async fn layout_heading(&mut self, heading: &NodeHeading) {
         let style = self.style.text.clone();
         self.style.text.font_scale *= 1.5 - 0.1 * heading.level.v.min(5) as f64;
         self.style.text.bolder = true;
 
         self.layout_parbreak();
-        self.layout_tree(&heading.tree).await;
+        self.layout_tree(&heading.contents).await;
         self.layout_parbreak();
 
         self.style.text = style;
     }
 
-    async fn layout_raw(&mut self, raw: &Raw) {
+    async fn layout_raw(&mut self, raw: &NodeRaw) {
         if !raw.inline {
             self.layout_parbreak();
         }
@@ -153,7 +152,7 @@ impl<'a> TreeLayouter<'a> {
         }
     }
 
-    async fn layout_call(&mut self, call: Spanned<&CallExpr>) {
+    async fn layout_expr(&mut self, expr: Spanned<&Expr>) {
         let ctx = LayoutContext {
             style: &self.style,
             spaces: self.layouter.remaining(),
@@ -161,11 +160,11 @@ impl<'a> TreeLayouter<'a> {
             ..self.ctx
         };
 
-        let val = call.v.eval(&ctx, &mut self.feedback).await;
-        let commands = val.span_with(call.span).into_commands();
+        let val = expr.v.eval(&ctx, &mut self.feedback).await;
+        let commands = val.span_with(expr.span).into_commands();
 
         for command in commands {
-            self.execute_command(command, call.span).await;
+            self.execute_command(command, expr.span).await;
         }
     }
 
diff --git a/src/lib.rs b/src/lib.rs
index 10e1f810..f79acbdf 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -50,7 +50,7 @@ use crate::diagnostic::Diagnostic;
 use crate::font::SharedFontLoader;
 use crate::layout::{Commands, MultiLayout};
 use crate::style::{LayoutStyle, PageStyle, TextStyle};
-use crate::syntax::{Decoration, Offset, Pos, SpanVec, SyntaxTree};
+use crate::syntax::{Decoration, Offset, Pos, SpanVec, SynTree};
 
 /// Transforms source code into typesetted layouts.
 ///
@@ -85,12 +85,12 @@ impl Typesetter {
     }
 
     /// Parse source code into a syntax tree.
-    pub fn parse(&self, src: &str) -> Pass<SyntaxTree> {
+    pub fn parse(&self, src: &str) -> Pass<SynTree> {
         parse::parse(src)
     }
 
     /// Layout a syntax tree and return the produced layout.
-    pub async fn layout(&self, tree: &SyntaxTree) -> Pass<MultiLayout> {
+    pub async fn layout(&self, tree: &SynTree) -> Pass<MultiLayout> {
         use crate::layout::prelude::*;
 
         let margins = self.style.page.margins();
diff --git a/src/library/align.rs b/src/library/align.rs
index 55259fd5..c909087a 100644
--- a/src/library/align.rs
+++ b/src/library/align.rs
@@ -17,7 +17,7 @@ use super::*;
 pub async fn align(_: Span, mut args: DictValue, ctx: LayoutContext<'_>) -> Pass<Value> {
     let mut f = Feedback::new();
 
-    let content = args.take::<SyntaxTree>();
+    let content = args.take::<SynTree>();
     let h = args.take_key::<Spanned<SpecAlign>>("horizontal", &mut f);
     let v = args.take_key::<Spanned<SpecAlign>>("vertical", &mut f);
     let all = args
diff --git a/src/library/boxed.rs b/src/library/boxed.rs
index 672e77d1..e02b8c0c 100644
--- a/src/library/boxed.rs
+++ b/src/library/boxed.rs
@@ -13,7 +13,7 @@ pub async fn boxed(
 ) -> Pass<Value> {
     let mut f = Feedback::new();
 
-    let content = args.take::<SyntaxTree>().unwrap_or(SyntaxTree::new());
+    let content = args.take::<SynTree>().unwrap_or(SynTree::new());
 
     ctx.base = ctx.spaces[0].size;
     ctx.spaces.truncate(1);
diff --git a/src/library/font.rs b/src/library/font.rs
index e9f6f9b4..e0133822 100644
--- a/src/library/font.rs
+++ b/src/library/font.rs
@@ -28,7 +28,7 @@ pub async fn font(_: Span, mut args: DictValue, ctx: LayoutContext<'_>) -> Pass<
     let mut text = ctx.style.text.clone();
     let mut updated_fallback = false;
 
-    let content = args.take::<SyntaxTree>();
+    let content = args.take::<SynTree>();
 
     if let Some(s) = args.take::<ScaleLength>() {
         match s {
diff --git a/src/parse/mod.rs b/src/parse/mod.rs
index 75ca7eb4..7a0002d6 100644
--- a/src/parse/mod.rs
+++ b/src/parse/mod.rs
@@ -12,14 +12,13 @@ pub use tokens::*;
 
 use std::str::FromStr;
 
-use super::*;
 use crate::color::RgbaColor;
-use crate::compute::dict::SpannedEntry;
+use crate::compute::dict::DictKey;
 use crate::syntax::*;
 use crate::{Feedback, Pass};
 
 /// Parse a string of source code.
-pub fn parse(src: &str) -> Pass<SyntaxTree> {
+pub fn parse(src: &str) -> Pass<SynTree> {
     Parser::new(src).parse()
 }
 
@@ -42,7 +41,7 @@ impl<'s> Parser<'s> {
         }
     }
 
-    fn parse(mut self) -> Pass<SyntaxTree> {
+    fn parse(mut self) -> Pass<SynTree> {
         let tree = self.parse_body_contents();
         Pass::new(tree, self.feedback)
     }
@@ -50,8 +49,8 @@ impl<'s> Parser<'s> {
 
 // Typesetting content.
 impl Parser<'_> {
-    fn parse_body_contents(&mut self) -> SyntaxTree {
-        let mut tree = SyntaxTree::new();
+    fn parse_body_contents(&mut self) -> SynTree {
+        let mut tree = SynTree::new();
 
         self.at_block_or_line_start = true;
         while !self.eof() {
@@ -63,7 +62,7 @@ impl Parser<'_> {
         tree
     }
 
-    fn parse_node(&mut self) -> Option<Spanned<SyntaxNode>> {
+    fn parse_node(&mut self) -> Option<Spanned<SynNode>> {
         let token = self.peek()?;
         let end = Span::at(token.span.end);
 
@@ -83,11 +82,7 @@ impl Parser<'_> {
                     self.at_block_or_line_start = true;
                 }
 
-                self.with_span(if n >= 2 {
-                    SyntaxNode::Parbreak
-                } else {
-                    SyntaxNode::Spacing
-                })
+                self.with_span(if n >= 2 { SynNode::Parbreak } else { SynNode::Spacing })
             }
 
             Token::LineComment(_) | Token::BlockComment(_) => {
@@ -99,15 +94,15 @@ impl Parser<'_> {
             Token::LeftBracket => {
                 let call = self.parse_bracket_call(false);
                 self.at_block_or_line_start = false;
-                call.map(SyntaxNode::Call)
+                call.map(|c| SynNode::Expr(Expr::Call(c)))
             }
 
-            Token::Star => self.with_span(SyntaxNode::ToggleBolder),
-            Token::Underscore => self.with_span(SyntaxNode::ToggleItalic),
-            Token::Backslash => self.with_span(SyntaxNode::Linebreak),
+            Token::Star => self.with_span(SynNode::ToggleBolder),
+            Token::Underscore => self.with_span(SynNode::ToggleItalic),
+            Token::Backslash => self.with_span(SynNode::Linebreak),
 
             Token::Hashtag if was_at_block_or_line_start => {
-                self.parse_heading().map(SyntaxNode::Heading)
+                self.parse_heading().map(SynNode::Heading)
             }
 
             Token::Raw { raw, backticks, terminated } => {
@@ -116,11 +111,11 @@ impl Parser<'_> {
                 }
 
                 let raw = resolve::resolve_raw(raw, backticks);
-                self.with_span(SyntaxNode::Raw(raw))
+                self.with_span(SynNode::Raw(raw))
             }
 
-            Token::Text(text) => self.with_span(SyntaxNode::Text(text.to_string())),
-            Token::Hashtag => self.with_span(SyntaxNode::Text("#".to_string())),
+            Token::Text(text) => self.with_span(SynNode::Text(text.to_string())),
+            Token::Hashtag => self.with_span(SynNode::Text("#".to_string())),
 
             Token::UnicodeEscape { sequence, terminated } => {
                 if !terminated {
@@ -128,7 +123,7 @@ impl Parser<'_> {
                 }
 
                 if let Some(c) = resolve::resolve_hex(sequence) {
-                    self.with_span(SyntaxNode::Text(c.to_string()))
+                    self.with_span(SynNode::Text(c.to_string()))
                 } else {
                     error!(@self.feedback, token.span, "invalid unicode escape sequence");
                     // TODO: Decide whether to render the escape sequence.
@@ -145,7 +140,7 @@ impl Parser<'_> {
         })
     }
 
-    fn parse_heading(&mut self) -> Spanned<Heading> {
+    fn parse_heading(&mut self) -> Spanned<NodeHeading> {
         let start = self.pos();
         self.assert(Token::Hashtag);
 
@@ -167,7 +162,7 @@ impl Parser<'_> {
 
         self.skip_ws();
 
-        let mut tree = SyntaxTree::new();
+        let mut tree = SynTree::new();
         while !self.eof() && !matches!(self.peekv(), Some(Token::Space(n)) if n >= 1) {
             if let Some(node) = self.parse_node() {
                 tree.push(node);
@@ -175,13 +170,13 @@ impl Parser<'_> {
         }
 
         let span = Span::new(start, self.pos());
-        Heading { level, tree }.span_with(span)
+        NodeHeading { level, contents: tree }.span_with(span)
     }
 }
 
 // Function calls.
 impl Parser<'_> {
-    fn parse_bracket_call(&mut self, chained: bool) -> Spanned<CallExpr> {
+    fn parse_bracket_call(&mut self, chained: bool) -> Spanned<ExprCall> {
         let before_bracket = self.pos();
         if !chained {
             self.start_group(Group::Bracket);
@@ -203,9 +198,9 @@ impl Parser<'_> {
             Some(_) => {
                 self.expected_at("colon", name.span.end);
                 while self.eat().is_some() {}
-                DictExpr::new()
+                LitDict::default()
             }
-            None => DictExpr::new(),
+            None => LitDict::default(),
         };
 
         self.end_group();
@@ -213,8 +208,9 @@ impl Parser<'_> {
         let (has_chained_child, end) = if self.peek().is_some() {
             let item = self.parse_bracket_call(true);
             let span = item.span;
-            let t = vec![item.map(SyntaxNode::Call)];
-            args.push(SpannedEntry::val(Expr::Tree(t).span_with(span)));
+            let tree = vec![item.map(|c| SynNode::Expr(Expr::Call(c)))];
+            let expr = Expr::Lit(Lit::Content(tree));
+            args.0.push(LitDictEntry { key: None, value: expr.span_with(span) });
             (true, span.end)
         } else {
             self.tokens.pop_mode();
@@ -227,40 +223,41 @@ impl Parser<'_> {
         if self.check(Token::LeftBracket) && !has_chained_child {
             self.start_group(Group::Bracket);
             self.tokens.push_mode(TokenMode::Body);
-
             let body = self.parse_body_contents();
-
             self.tokens.pop_mode();
             let body_span = self.end_group();
 
-            let expr = Expr::Tree(body);
-            args.push(SpannedEntry::val(expr.span_with(body_span)));
+            let expr = Expr::Lit(Lit::Content(body));
+            args.0.push(LitDictEntry {
+                key: None,
+                value: expr.span_with(body_span),
+            });
             span.expand(body_span);
         }
 
-        CallExpr { name, args }.span_with(span)
+        ExprCall { name, args }.span_with(span)
     }
 
-    fn parse_paren_call(&mut self, name: Spanned<Ident>) -> Spanned<CallExpr> {
+    fn parse_paren_call(&mut self, name: Spanned<Ident>) -> Spanned<ExprCall> {
         self.start_group(Group::Paren);
         let args = self.parse_dict_contents().0;
         let args_span = self.end_group();
         let span = Span::merge(name.span, args_span);
-        CallExpr { name, args }.span_with(span)
+        ExprCall { name, args }.span_with(span)
     }
 }
 
 // Dicts.
 impl Parser<'_> {
-    fn parse_dict_contents(&mut self) -> (DictExpr, bool) {
-        let mut dict = DictExpr::new();
+    fn parse_dict_contents(&mut self) -> (LitDict, bool) {
+        let mut dict = LitDict::default();
         let mut comma_and_keyless = true;
 
         while {
             self.skip_ws();
             !self.eof()
         } {
-            let (key, val) = if let Some(ident) = self.parse_ident() {
+            let (key, value) = if let Some(ident) = self.parse_ident() {
                 self.skip_ws();
 
                 match self.peekv() {
@@ -268,7 +265,7 @@ impl Parser<'_> {
                         self.eat();
                         self.skip_ws();
                         if let Some(value) = self.parse_expr() {
-                            (Some(ident), value)
+                            (Some(ident.map(|id| DictKey::Str(id.0))), value)
                         } else {
                             self.expected("value");
                             continue;
@@ -280,7 +277,7 @@ impl Parser<'_> {
                         (None, call.map(Expr::Call))
                     }
 
-                    _ => (None, ident.map(Expr::Ident)),
+                    _ => (None, ident.map(|id| Expr::Lit(Lit::Ident(id)))),
                 }
             } else if let Some(value) = self.parse_expr() {
                 (None, value)
@@ -289,17 +286,16 @@ impl Parser<'_> {
                 continue;
             };
 
-            let behind = val.span.end;
-            if let Some(key) = key {
+            if let Some(key) = &key {
                 comma_and_keyless = false;
-                dict.insert(key.v.0, SpannedEntry::new(key.span, val));
                 self.feedback
                     .decorations
                     .push(Decoration::DictKey.span_with(key.span));
-            } else {
-                dict.push(SpannedEntry::val(val));
             }
 
+            let behind = value.span.end;
+            dict.0.push(LitDictEntry { key, value });
+
             if {
                 self.skip_ws();
                 self.eof()
@@ -311,27 +307,25 @@ impl Parser<'_> {
             comma_and_keyless = false;
         }
 
-        let coercable = comma_and_keyless && !dict.is_empty();
+        let coercable = comma_and_keyless && !dict.0.is_empty();
         (dict, coercable)
     }
 }
 
-type Binop = fn(Box<Spanned<Expr>>, Box<Spanned<Expr>>) -> Expr;
-
 // Expressions and values.
 impl Parser<'_> {
     fn parse_expr(&mut self) -> Option<Spanned<Expr>> {
         self.parse_binops("summand", Self::parse_term, |token| match token {
-            Token::Plus => Some(Expr::Add),
-            Token::Hyphen => Some(Expr::Sub),
+            Token::Plus => Some(BinOp::Add),
+            Token::Hyphen => Some(BinOp::Sub),
             _ => None,
         })
     }
 
     fn parse_term(&mut self) -> Option<Spanned<Expr>> {
         self.parse_binops("factor", Self::parse_factor, |token| match token {
-            Token::Star => Some(Expr::Mul),
-            Token::Slash => Some(Expr::Div),
+            Token::Star => Some(BinOp::Mul),
+            Token::Slash => Some(BinOp::Div),
             _ => None,
         })
     }
@@ -341,7 +335,7 @@ impl Parser<'_> {
         &mut self,
         operand_name: &str,
         mut parse_operand: impl FnMut(&mut Self) -> Option<Spanned<Expr>>,
-        mut parse_op: impl FnMut(Token) -> Option<Binop>,
+        mut parse_op: impl FnMut(Token) -> Option<BinOp>,
     ) -> Option<Spanned<Expr>> {
         let mut left = parse_operand(self)?;
 
@@ -353,8 +347,12 @@ impl Parser<'_> {
 
                 if let Some(right) = parse_operand(self) {
                     let span = Span::merge(left.span, right.span);
-                    let v = op(Box::new(left), Box::new(right));
-                    left = v.span_with(span);
+                    let expr = Expr::Binary(ExprBinary {
+                        lhs: left.map(Box::new),
+                        op: op.span_with(token.span),
+                        rhs: right.map(Box::new),
+                    });
+                    left = expr.span_with(span);
                     self.skip_ws();
                     continue;
                 }
@@ -375,7 +373,11 @@ impl Parser<'_> {
             self.skip_ws();
             if let Some(factor) = self.parse_factor() {
                 let span = Span::merge(hyph.span, factor.span);
-                Some(Expr::Neg(Box::new(factor)).span_with(span))
+                let expr = Expr::Unary(ExprUnary {
+                    op: UnOp::Neg.span_with(hyph.span),
+                    expr: factor.map(Box::new),
+                });
+                Some(expr.span_with(span))
             } else {
                 error!(@self.feedback, hyph.span, "dangling minus");
                 None
@@ -396,7 +398,7 @@ impl Parser<'_> {
                 if self.check(Token::LeftParen) {
                     self.parse_paren_call(name).map(Expr::Call)
                 } else {
-                    name.map(Expr::Ident)
+                    name.map(|n| Expr::Lit(Lit::Ident(n)))
                 }
             }
 
@@ -404,21 +406,19 @@ impl Parser<'_> {
                 if !terminated {
                     self.expected_at("quote", span.end);
                 }
-                self.with_span(Expr::Str(resolve::resolve_string(string)))
+                self.with_span(Expr::Lit(Lit::Str(resolve::resolve_string(string))))
             }
 
-            Token::Bool(b) => self.with_span(Expr::Bool(b)),
-            Token::Number(n) => self.with_span(Expr::Number(n)),
-            Token::Length(s) => self.with_span(Expr::Length(s)),
+            Token::Bool(b) => self.with_span(Expr::Lit(Lit::Bool(b))),
+            Token::Number(n) => self.with_span(Expr::Lit(Lit::Float(n))),
+            Token::Length(s) => self.with_span(Expr::Lit(Lit::Length(s))),
             Token::Hex(s) => {
-                if let Ok(color) = RgbaColor::from_str(s) {
-                    self.with_span(Expr::Color(color))
-                } else {
+                let color = RgbaColor::from_str(s).unwrap_or_else(|_| {
                     // Heal color by assuming black.
                     error!(@self.feedback, span, "invalid color");
-                    let healed = RgbaColor::new_healed(0, 0, 0, 255);
-                    self.with_span(Expr::Color(healed))
-                }
+                    RgbaColor::new_healed(0, 0, 0, 255)
+                });
+                self.with_span(Expr::Lit(Lit::Color(color)))
             }
 
             // This could be a dictionary or a parenthesized expression. We
@@ -430,9 +430,9 @@ impl Parser<'_> {
                 let span = self.end_group();
 
                 let expr = if coercable {
-                    dict.into_values().next().expect("dict is coercable").val.v
+                    dict.0.into_iter().next().expect("dict is coercable").value.v
                 } else {
-                    Expr::Dict(dict)
+                    Expr::Lit(Lit::Dict(dict))
                 };
 
                 expr.span_with(span)
@@ -442,19 +442,17 @@ impl Parser<'_> {
             Token::LeftBrace => {
                 self.start_group(Group::Brace);
                 self.tokens.push_mode(TokenMode::Body);
-
                 let tree = self.parse_body_contents();
-
                 self.tokens.pop_mode();
                 let span = self.end_group();
-                Expr::Tree(tree).span_with(span)
+                Expr::Lit(Lit::Content(tree)).span_with(span)
             }
 
             // This is a bracketed function call.
             Token::LeftBracket => {
                 let call = self.parse_bracket_call(false);
-                let tree = vec![call.map(SyntaxNode::Call)];
-                Expr::Tree(tree).span_with(span)
+                let tree = vec![call.map(|c| SynNode::Expr(Expr::Call(c)))];
+                Expr::Lit(Lit::Content(tree)).span_with(span)
             }
 
             _ => return None,
diff --git a/src/parse/resolve.rs b/src/parse/resolve.rs
index d4babd25..f9919373 100644
--- a/src/parse/resolve.rs
+++ b/src/parse/resolve.rs
@@ -1,7 +1,7 @@
 //! Resolve strings and raw blocks.
 
 use super::{is_newline, Scanner};
-use crate::syntax::{Ident, Raw};
+use crate::syntax::{Ident, NodeRaw};
 
 /// Resolves all escape sequences in a string.
 pub fn resolve_string(string: &str) -> String {
@@ -49,17 +49,17 @@ pub fn resolve_hex(sequence: &str) -> Option<char> {
 }
 
 /// Resolves the language tag and trims the raw text.
-pub fn resolve_raw(raw: &str, backticks: usize) -> Raw {
+pub fn resolve_raw(raw: &str, backticks: usize) -> NodeRaw {
     if backticks > 1 {
         let (tag, inner) = split_at_lang_tag(raw);
         let (lines, had_newline) = trim_and_split_raw(inner);
-        Raw {
+        NodeRaw {
             lang: Ident::new(tag),
             lines,
             inline: !had_newline,
         }
     } else {
-        Raw {
+        NodeRaw {
             lang: None,
             lines: split_lines(raw),
             inline: true,
diff --git a/src/parse/tests.rs b/src/parse/tests.rs
index e516af32..302e93ee 100644
--- a/src/parse/tests.rs
+++ b/src/parse/tests.rs
@@ -6,33 +6,33 @@ use std::fmt::Debug;
 
 use super::parse;
 use crate::color::RgbaColor;
-use crate::compute::dict::SpannedEntry;
+use crate::compute::dict::DictKey;
 use crate::length::Length;
 use crate::syntax::*;
 
 // ------------------------------ Construct Syntax Nodes ------------------------------ //
 
 use Decoration::*;
-use SyntaxNode::{
+use SynNode::{
     Linebreak as L, Parbreak as P, Spacing as S, ToggleBolder as B, ToggleItalic as I,
 };
 
-fn T(text: &str) -> SyntaxNode {
-    SyntaxNode::Text(text.to_string())
+fn T(text: &str) -> SynNode {
+    SynNode::Text(text.to_string())
 }
 
 macro_rules! H {
     ($level:expr, $($tts:tt)*) => {
-        SyntaxNode::Heading(Heading {
+        SynNode::Heading(NodeHeading {
             level: Spanned::zero($level),
-            tree: Tree![@$($tts)*],
+            contents: Tree![@$($tts)*],
         })
     };
 }
 
 macro_rules! R {
     ($lang:expr, $inline:expr, $($line:expr),* $(,)?) => {{
-        SyntaxNode::Raw(Raw {
+        SynNode::Raw(NodeRaw {
             lang: $lang,
             lines: vec![$($line.to_string()) ,*],
             inline: $inline,
@@ -45,53 +45,73 @@ fn Lang(lang: &str) -> Option<Ident> {
 }
 
 macro_rules! F {
-    ($($tts:tt)*) => { SyntaxNode::Call(Call!(@$($tts)*)) }
+    ($($tts:tt)*) => { SynNode::Expr(Expr::Call(Call!(@$($tts)*))) }
 }
 
 // ------------------------------- Construct Expressions ------------------------------ //
 
-use Expr::{Bool, Color, Length as Len, Number as Num};
+use BinOp::*;
+use UnOp::*;
 
 fn Id(ident: &str) -> Expr {
-    Expr::Ident(Ident(ident.to_string()))
+    Expr::Lit(Lit::Ident(Ident(ident.to_string())))
+}
+fn Bool(b: bool) -> Expr {
+    Expr::Lit(Lit::Bool(b))
+}
+fn _Int(int: i64) -> Expr {
+    Expr::Lit(Lit::Int(int))
+}
+fn Float(float: f64) -> Expr {
+    Expr::Lit(Lit::Float(float))
+}
+fn _Percent(percent: f64) -> Expr {
+    Expr::Lit(Lit::Percent(percent))
+}
+fn Len(length: Length) -> Expr {
+    Expr::Lit(Lit::Length(length))
+}
+fn Color(color: RgbaColor) -> Expr {
+    Expr::Lit(Lit::Color(color))
 }
 fn Str(string: &str) -> Expr {
-    Expr::Str(string.to_string())
+    Expr::Lit(Lit::Str(string.to_string()))
 }
 
 macro_rules! Dict {
     (@dict=$dict:expr,) => {};
     (@dict=$dict:expr, $key:expr => $value:expr $(, $($tts:tt)*)?) => {{
         let key = Into::<Spanned<&str>>::into($key);
-        let val = Into::<Spanned<Expr>>::into($value);
-        $dict.insert(key.v, SpannedEntry::new(key.span, val));
+        let key = key.map(Into::<DictKey>::into);
+        let value = Into::<Spanned<Expr>>::into($value);
+        $dict.0.push(LitDictEntry { key: Some(key), value });
         Dict![@dict=$dict, $($($tts)*)?];
     }};
     (@dict=$dict:expr, $value:expr $(, $($tts:tt)*)?) => {
-        let val = Into::<Spanned<Expr>>::into($value);
-        $dict.push(SpannedEntry::val(val));
+        let value = Into::<Spanned<Expr>>::into($value);
+        $dict.0.push(LitDictEntry { key: None, value });
         Dict![@dict=$dict, $($($tts)*)?];
     };
     (@$($tts:tt)*) => {{
         #[allow(unused_mut)]
-        let mut dict = DictExpr::new();
+        let mut dict = LitDict::default();
         Dict![@dict=dict, $($tts)*];
         dict
     }};
-    ($($tts:tt)*) => { Expr::Dict(Dict![@$($tts)*]) };
+    ($($tts:tt)*) => { Expr::Lit(Lit::Dict(Dict![@$($tts)*])) };
 }
 
 macro_rules! Tree {
     (@$($node:expr),* $(,)?) => {
-        vec![$(Into::<Spanned<SyntaxNode>>::into($node)),*]
+        vec![$(Into::<Spanned<SynNode>>::into($node)),*]
     };
-    ($($tts:tt)*) => { Expr::Tree(Tree![@$($tts)*]) };
+    ($($tts:tt)*) => { Expr::Lit(Lit::Content(Tree![@$($tts)*])) };
 }
 
 macro_rules! Call {
     (@$name:expr $(; $($tts:tt)*)?) => {{
         let name = Into::<Spanned<&str>>::into($name);
-        CallExpr {
+        ExprCall {
             name: name.map(|n| Ident(n.to_string())),
             args: Dict![@$($($tts)*)?],
         }
@@ -99,20 +119,22 @@ macro_rules! Call {
     ($($tts:tt)*) => { Expr::Call(Call![@$($tts)*]) };
 }
 
-fn Neg<T: Into<Spanned<Expr>>>(e1: T) -> Expr {
-    Expr::Neg(Box::new(e1.into()))
-}
-fn Add<T: Into<Spanned<Expr>>>(e1: T, e2: T) -> Expr {
-    Expr::Add(Box::new(e1.into()), Box::new(e2.into()))
-}
-fn Sub<T: Into<Spanned<Expr>>>(e1: T, e2: T) -> Expr {
-    Expr::Sub(Box::new(e1.into()), Box::new(e2.into()))
+fn Unary(op: impl Into<Spanned<UnOp>>, expr: impl Into<Spanned<Expr>>) -> Expr {
+    Expr::Unary(ExprUnary {
+        op: op.into(),
+        expr: expr.into().map(Box::new),
+    })
 }
-fn Mul<T: Into<Spanned<Expr>>>(e1: T, e2: T) -> Expr {
-    Expr::Mul(Box::new(e1.into()), Box::new(e2.into()))
-}
-fn Div<T: Into<Spanned<Expr>>>(e1: T, e2: T) -> Expr {
-    Expr::Div(Box::new(e1.into()), Box::new(e2.into()))
+fn Binary(
+    op: impl Into<Spanned<BinOp>>,
+    lhs: impl Into<Spanned<Expr>>,
+    rhs: impl Into<Spanned<Expr>>,
+) -> Expr {
+    Expr::Binary(ExprBinary {
+        lhs: lhs.into().map(Box::new),
+        op: op.into(),
+        rhs: rhs.into().map(Box::new),
+    })
 }
 
 // ------------------------------------ Test Macros ----------------------------------- //
@@ -321,12 +343,12 @@ fn test_parse_function_names() {
 #[test]
 fn test_parse_chaining() {
     // Things the parser has to make sense of
-    t!("[hi: (5.0, 2.1 >> you]" => F!("hi"; Dict![Num(5.0), Num(2.1)], Tree![F!("you")]));
+    t!("[hi: (5.0, 2.1 >> you]" => F!("hi"; Dict![Float(5.0), Float(2.1)], Tree![F!("you")]));
     t!("[box >>][Hi]"           => F!("box"; Tree![T("Hi")]));
     t!("[box >> pad: 1pt][Hi]"  => F!("box"; Tree![
         F!("pad"; Len(Length::pt(1.0)), Tree!(T("Hi")))
     ]));
-    t!("[bold: 400, >> emph >> sub: 1cm]" => F!("bold"; Num(400.0), Tree![
+    t!("[bold: 400, >> emph >> sub: 1cm]" => F!("bold"; Float(400.0), Tree![
         F!("emph"; Tree!(F!("sub"; Len(Length::cm(1.0)))))
     ]));
 
@@ -354,7 +376,7 @@ fn test_parse_colon_starting_func_args() {
 
 #[test]
 fn test_parse_function_bodies() {
-    t!("[val: 1][*Hi*]" => F!("val"; Num(1.0), Tree![B, T("Hi"), B]));
+    t!("[val: 1][*Hi*]" => F!("val"; Float(1.0), Tree![B, T("Hi"), B]));
     e!(" [val][ */]"    => s(8, 10, "unexpected end of block comment"));
 
     // Raw in body.
@@ -384,9 +406,9 @@ fn test_parse_values() {
     v!("\"hi\""    => Str("hi"));
     v!("true"      => Bool(true));
     v!("false"     => Bool(false));
-    v!("1.0e-4"    => Num(1e-4));
-    v!("3.14"      => Num(3.14));
-    v!("50%"       => Num(0.5));
+    v!("1.0e-4"    => Float(1e-4));
+    v!("3.14"      => Float(3.14));
+    v!("50%"       => Float(0.5));
     v!("4.5cm"     => Len(Length::cm(4.5)));
     v!("12e1pt"    => Len(Length::pt(12e1)));
     v!("#f7a20500" => Color(RgbaColor::new(0xf7, 0xa2, 0x05, 0x00)));
@@ -411,7 +433,7 @@ fn test_parse_values() {
                            s(13, 13, "expected closing bracket"));
 
     // Spanned.
-    ts!("[val: 1.4]" => s(0, 10, F!(s(1, 4, "val"); s(6, 9, Num(1.4)))));
+    ts!("[val: 1.4]" => s(0, 10, F!(s(1, 4, "val"); s(6, 9, Float(1.4)))));
 }
 
 #[test]
@@ -420,40 +442,50 @@ fn test_parse_expressions() {
     v!("(hi)" => Id("hi"));
 
     // Operations.
-    v!("-1"          => Neg(Num(1.0)));
-    v!("-- 1"        => Neg(Neg(Num(1.0))));
-    v!("3.2in + 6pt" => Add(Len(Length::inches(3.2)), Len(Length::pt(6.0))));
-    v!("5 - 0.01"    => Sub(Num(5.0), Num(0.01)));
-    v!("(3mm * 2)"   => Mul(Len(Length::mm(3.0)), Num(2.0)));
-    v!("12e-3cm/1pt" => Div(Len(Length::cm(12e-3)), Len(Length::pt(1.0))));
+    v!("-1"          => Unary(Neg, Float(1.0)));
+    v!("-- 1"        => Unary(Neg, Unary(Neg, Float(1.0))));
+    v!("3.2in + 6pt" => Binary(Add, Len(Length::inches(3.2)), Len(Length::pt(6.0))));
+    v!("5 - 0.01"    => Binary(Sub, Float(5.0), Float(0.01)));
+    v!("(3mm * 2)"   => Binary(Mul, Len(Length::mm(3.0)), Float(2.0)));
+    v!("12e-3cm/1pt" => Binary(Div, Len(Length::cm(12e-3)), Len(Length::pt(1.0))));
 
     // More complex.
-    v!("(3.2in + 6pt)*(5/2-1)" => Mul(
-        Add(Len(Length::inches(3.2)), Len(Length::pt(6.0))),
-        Sub(Div(Num(5.0), Num(2.0)), Num(1.0))
+    v!("(3.2in + 6pt)*(5/2-1)" => Binary(
+        Mul,
+        Binary(Add, Len(Length::inches(3.2)), Len(Length::pt(6.0))),
+        Binary(Sub, Binary(Div, Float(5.0), Float(2.0)), Float(1.0))
     ));
-    v!("(6.3E+2+4* - 3.2pt)/2" => Div(
-        Add(Num(6.3e2), Mul(Num(4.0), Neg(Len(Length::pt(3.2))))),
-        Num(2.0)
+    v!("(6.3E+2+4* - 3.2pt)/2" => Binary(
+        Div,
+        Binary(Add, Float(6.3e2), Binary(
+            Mul,
+            Float(4.0),
+            Unary(Neg, Len(Length::pt(3.2)))
+        )),
+        Float(2.0)
     ));
 
     // Associativity of multiplication and division.
-    v!("3/4*5" => Mul(Div(Num(3.0), Num(4.0)), Num(5.0)));
+    v!("3/4*5" => Binary(Mul, Binary(Div, Float(3.0), Float(4.0)), Float(5.0)));
 
     // Spanned.
     ts!("[val: 1 + 3]" => s(0, 12, F!(
-        s(1, 4, "val"); s(6, 11, Add(s(6, 7, Num(1.0)), s(10, 11, Num(3.0))))
+        s(1, 4, "val"); s(6, 11, Binary(
+            s(8, 9, Add),
+            s(6, 7, Float(1.0)),
+            s(10, 11, Float(3.0))
+        ))
     )));
 
     // Span of parenthesized expression contains parens.
-    ts!("[val: (1)]" => s(0, 10, F!(s(1, 4, "val"); s(6, 9, Num(1.0)))));
+    ts!("[val: (1)]" => s(0, 10, F!(s(1, 4, "val"); s(6, 9, Float(1.0)))));
 
     // Invalid expressions.
     v!("4pt--"        => Len(Length::pt(4.0)));
     e!("[val: 4pt--]" => s(10, 11, "dangling minus"),
                          s(6, 10, "missing right summand"));
 
-    v!("3mm+4pt*"        => Add(Len(Length::mm(3.0)), Len(Length::pt(4.0))));
+    v!("3mm+4pt*"        => Binary(Add, Len(Length::mm(3.0)), Len(Length::pt(4.0))));
     e!("[val: 3mm+4pt*]" => s(10, 14, "missing right factor"));
 }
 
@@ -464,8 +496,8 @@ fn test_parse_dicts() {
     v!("(false)"            => Bool(false));
     v!("(true,)"            => Dict![Bool(true)]);
     v!("(key=val)"          => Dict!["key" => Id("val")]);
-    v!("(1, 2)"             => Dict![Num(1.0), Num(2.0)]);
-    v!("(1, key=\"value\")" => Dict![Num(1.0), "key" => Str("value")]);
+    v!("(1, 2)"             => Dict![Float(1.0), Float(2.0)]);
+    v!("(1, key=\"value\")" => Dict![Float(1.0), "key" => Str("value")]);
 
     // Decorations.
     d!("[val: key=hi]"    => s(6, 9, DictKey));
@@ -483,7 +515,7 @@ fn test_parse_dicts() {
 #[test]
 fn test_parse_dicts_compute_func_calls() {
     v!("empty()"                  => Call!("empty"));
-    v!("add ( 1 , 2 )"            => Call!("add"; Num(1.0), Num(2.0)));
+    v!("add ( 1 , 2 )"            => Call!("add"; Float(1.0), Float(2.0)));
     v!("items(\"fire\", #f93a6d)" => Call!("items";
         Str("fire"), Color(RgbaColor::new(0xf9, 0x3a, 0x6d, 0xff))
     ));
@@ -492,7 +524,7 @@ fn test_parse_dicts_compute_func_calls() {
     v!("css(1pt, rgb(90, 102, 254), \"solid\")" => Call!(
         "css";
         Len(Length::pt(1.0)),
-        Call!("rgb"; Num(90.0), Num(102.0), Num(254.0)),
+        Call!("rgb"; Float(90.0), Float(102.0), Float(254.0)),
         Str("solid"),
     ));
 
@@ -501,7 +533,7 @@ fn test_parse_dicts_compute_func_calls() {
     e!("[val: lang(中文]" => s(17, 17, "expected closing paren"));
 
     // Invalid name.
-    v!("👠(\"abc\", 13e-5)"        => Dict!(Str("abc"), Num(13.0e-5)));
+    v!("👠(\"abc\", 13e-5)"        => Dict!(Str("abc"), Float(13.0e-5)));
     e!("[val: 👠(\"abc\", 13e-5)]" => s(6, 10, "expected value, found invalid token"));
 }
 
@@ -509,10 +541,10 @@ fn test_parse_dicts_compute_func_calls() {
 fn test_parse_dicts_nested() {
     v!("(1, ( ab=(), d = (3, 14pt) )), false" =>
         Dict![
-            Num(1.0),
+            Float(1.0),
             Dict!(
                 "ab" => Dict![],
-                "d"  => Dict!(Num(3.0), Len(Length::pt(14.0))),
+                "d"  => Dict!(Float(3.0), Len(Length::pt(14.0))),
             ),
         ],
         Bool(false),
@@ -546,7 +578,7 @@ fn test_parse_dicts_errors() {
         s(10, 11, "expected value, found equals sign"));
 
     // Unexpected equals sign.
-    v!("z=y=4"        => Num(4.0), "z" => Id("y"));
+    v!("z=y=4"        => "z" => Id("y"), Float(4.0));
     e!("[val: z=y=4]" =>
         s(9, 9, "expected comma"),
         s(9, 10, "expected value, found equals sign"));
diff --git a/src/syntax/expr.rs b/src/syntax/expr.rs
new file mode 100644
index 00000000..817b3d6e
--- /dev/null
+++ b/src/syntax/expr.rs
@@ -0,0 +1,124 @@
+//! Expressions.
+
+use super::span::{SpanWith, Spanned};
+use super::{Decoration, Ident, Lit, LitDict};
+use crate::compute::value::Value;
+use crate::layout::LayoutContext;
+use crate::Feedback;
+
+/// An expression.
+#[derive(Debug, Clone, PartialEq)]
+pub enum Expr {
+    /// A literal: `true`, `1cm`, `"hi"`, `{_Hey!_}`.
+    Lit(Lit),
+    /// A unary operation: `-x`.
+    Unary(ExprUnary),
+    /// A binary operation: `a + b`, `a / b`.
+    Binary(ExprBinary),
+    /// An invocation of a function: `[foo: ...]`, `foo(...)`.
+    Call(ExprCall),
+}
+
+impl Expr {
+    /// Evaluate the expression to a value.
+    pub async fn eval(&self, ctx: &LayoutContext<'_>, f: &mut Feedback) -> Value {
+        match self {
+            Self::Lit(lit) => lit.eval(ctx, f).await,
+            Self::Unary(unary) => unary.eval(ctx, f).await,
+            Self::Binary(binary) => binary.eval(ctx, f).await,
+            Self::Call(call) => call.eval(ctx, f).await,
+        }
+    }
+}
+
+/// A unary operation: `-x`.
+#[derive(Debug, Clone, PartialEq)]
+pub struct ExprUnary {
+    /// The operator: `-`.
+    pub op: Spanned<UnOp>,
+    /// The expression to operator on: `x`.
+    pub expr: Spanned<Box<Expr>>,
+}
+
+impl ExprUnary {
+    /// Evaluate the expression to a value.
+    pub async fn eval(&self, _: &LayoutContext<'_>, _: &mut Feedback) -> Value {
+        match self.op.v {
+            UnOp::Neg => todo!("eval neg"),
+        }
+    }
+}
+
+/// A unary operator.
+#[derive(Debug, Clone, PartialEq)]
+pub enum UnOp {
+    /// The negation operator: `-`.
+    Neg,
+}
+
+/// A binary operation: `a + b`, `a / b`.
+#[derive(Debug, Clone, PartialEq)]
+pub struct ExprBinary {
+    /// The left-hand side of the operation: `a`.
+    pub lhs: Spanned<Box<Expr>>,
+    /// The operator: `+`.
+    pub op: Spanned<BinOp>,
+    /// The right-hand side of the operation: `b`.
+    pub rhs: Spanned<Box<Expr>>,
+}
+
+impl ExprBinary {
+    /// Evaluate the expression to a value.
+    pub async fn eval(&self, _: &LayoutContext<'_>, _: &mut Feedback) -> Value {
+        match self.op.v {
+            BinOp::Add => todo!("eval add"),
+            BinOp::Sub => todo!("eval sub"),
+            BinOp::Mul => todo!("eval mul"),
+            BinOp::Div => todo!("eval div"),
+        }
+    }
+}
+
+/// A binary operator.
+#[derive(Debug, Clone, PartialEq)]
+pub enum BinOp {
+    /// The addition operator: `+`.
+    Add,
+    /// The subtraction operator: `-`.
+    Sub,
+    /// The multiplication operator: `*`.
+    Mul,
+    /// The division operator: `/`.
+    Div,
+}
+
+/// An invocation of a function: `[foo: ...]`, `foo(...)`.
+#[derive(Debug, Clone, PartialEq)]
+pub struct ExprCall {
+    /// The name of the function.
+    pub name: Spanned<Ident>,
+    /// The arguments to the function.
+    pub args: LitDict,
+}
+
+impl ExprCall {
+    /// Evaluate the call expression to a value.
+    pub async fn eval(&self, ctx: &LayoutContext<'_>, f: &mut Feedback) -> Value {
+        let name = &self.name.v;
+        let span = self.name.span;
+        let args = self.args.eval(ctx, f).await;
+
+        if let Some(func) = ctx.scope.func(name) {
+            let pass = func(span, args, ctx.clone()).await;
+            f.extend(pass.feedback);
+            f.decorations.push(Decoration::Resolved.span_with(span));
+            pass.output
+        } else {
+            if !name.is_empty() {
+                error!(@f, span, "unknown function");
+                f.decorations.push(Decoration::Unresolved.span_with(span));
+            }
+            Value::Dict(args)
+        }
+    }
+}
diff --git a/src/syntax/ident.rs b/src/syntax/ident.rs
new file mode 100644
index 00000000..5ab7c73c
--- /dev/null
+++ b/src/syntax/ident.rs
@@ -0,0 +1,58 @@
+//! Unicode identifiers.
+
+use std::ops::Deref;
+
+use unicode_xid::UnicodeXID;
+
+/// An identifier as defined by unicode with a few extra permissible characters.
+///
+/// This is defined as in the [Unicode Standard], but allows additionally
+/// `-` and `_` as starting and continuing characters.
+///
+/// [Unicode Standard]: http://www.unicode.org/reports/tr31/
+#[derive(Debug, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
+pub struct Ident(pub String);
+
+impl Ident {
+    /// Create a new identifier from a string checking that it is a valid.
+    pub fn new(ident: impl AsRef<str> + Into<String>) -> Option<Self> {
+        if is_ident(ident.as_ref()) {
+            Some(Self(ident.into()))
+        } else {
+            None
+        }
+    }
+
+    /// Return a reference to the underlying string.
+    pub fn as_str(&self) -> &str {
+        self
+    }
+}
+
+impl AsRef<str> for Ident {
+    fn as_ref(&self) -> &str {
+        self
+    }
+}
+
+impl Deref for Ident {
+    type Target = str;
+
+    fn deref(&self) -> &Self::Target {
+        self.0.as_str()
+    }
+}
+
+/// Whether the string is a valid identifier.
+pub fn is_ident(string: &str) -> bool {
+    let mut chars = string.chars();
+    if matches!(chars.next(), Some(c) if c.is_xid_start() || is_also_ok(c)) {
+        chars.all(|c| c.is_xid_continue() || is_also_ok(c))
+    } else {
+        false
+    }
+}
+
+fn is_also_ok(c: char) -> bool {
+    c == '-' || c == '_'
+}
diff --git a/src/syntax/lit.rs b/src/syntax/lit.rs
new file mode 100644
index 00000000..e9807a17
--- /dev/null
+++ b/src/syntax/lit.rs
@@ -0,0 +1,99 @@
+//! Literals.
+
+use super::{Expr, Ident, SpanWith, Spanned, SynTree};
+use crate::color::RgbaColor;
+use crate::compute::dict::{DictKey, SpannedEntry};
+use crate::compute::value::{DictValue, Value};
+use crate::layout::LayoutContext;
+use crate::length::Length;
+use crate::{DynFuture, Feedback};
+
+/// A literal.
+#[derive(Debug, Clone, PartialEq)]
+pub enum Lit {
+    /// A identifier literal: `left`.
+    Ident(Ident),
+    /// A boolean literal: `true`, `false`.
+    Bool(bool),
+    /// An integer literal: `120`.
+    Int(i64),
+    /// A floating-point literal: `1.2`, `10e-4`.
+    Float(f64),
+    /// A percent literal: `50%`.
+    Percent(f64),
+    /// A length literal: `12pt`, `3cm`.
+    Length(Length),
+    /// A color literal: `#ffccee`.
+    Color(RgbaColor),
+    /// A string literal: `"hello!"`.
+    Str(String),
+    /// A dictionary literal: `(false, 12cm, greeting = "hi")`.
+    Dict(LitDict),
+    /// A content literal: `{*Hello* there!}`.
+    Content(SynTree),
+}
+
+impl Lit {
+    /// Evaluate the dictionary literal to a dictionary value.
+    pub async fn eval<'a>(
+        &'a self,
+        ctx: &'a LayoutContext<'a>,
+        f: &'a mut Feedback,
+    ) -> Value {
+        match *self {
+            Lit::Ident(ref i) => Value::Ident(i.clone()),
+            Lit::Bool(b) => Value::Bool(b),
+            Lit::Int(i) => Value::Number(i as f64),
+            Lit::Float(f) => Value::Number(f as f64),
+            Lit::Percent(p) => Value::Number(p as f64 / 100.0),
+            Lit::Length(l) => Value::Length(l),
+            Lit::Color(c) => Value::Color(c),
+            Lit::Str(ref s) => Value::Str(s.clone()),
+            Lit::Dict(ref d) => Value::Dict(d.eval(ctx, f).await),
+            Lit::Content(ref c) => Value::Tree(c.clone()),
+        }
+    }
+}
+
+/// A dictionary literal: `(false, 12cm, greeting = "hi")`.
+#[derive(Debug, Default, Clone, PartialEq)]
+pub struct LitDict(pub Vec<LitDictEntry>);
+
+impl LitDict {
+    /// Create an empty dict literal.
+    pub fn new() -> Self {
+        Self(vec![])
+    }
+
+    /// Evaluate the dictionary literal to a dictionary value.
+    pub fn eval<'a>(
+        &'a self,
+        ctx: &'a LayoutContext<'a>,
+        f: &'a mut Feedback,
+    ) -> DynFuture<'a, DictValue> {
+        Box::pin(async move {
+            let mut dict = DictValue::new();
+
+            for entry in &self.0 {
+                let val = entry.value.v.eval(ctx, f).await;
+                let spanned = val.span_with(entry.value.span);
+                if let Some(key) = &entry.key {
+                    dict.insert(&key.v, SpannedEntry::new(key.span, spanned));
+                } else {
+                    dict.push(SpannedEntry::val(spanned));
+                }
+            }
+
+            dict
+        })
+    }
+}
+
+/// An entry in a dictionary literal: `false` or `greeting = "hi"`.
+#[derive(Debug, Clone, PartialEq)]
+pub struct LitDictEntry {
+    /// The key of the entry if there was one: `greeting`.
+    pub key: Option<Spanned<DictKey>>,
+    /// The value of the entry: `"hi"`.
+    pub value: Spanned<Expr>,
+}
diff --git a/src/syntax/mod.rs b/src/syntax/mod.rs
index 0809d33f..f4472df5 100644
--- a/src/syntax/mod.rs
+++ b/src/syntax/mod.rs
@@ -1,12 +1,24 @@
 //! Syntax types.
 
+mod expr;
+mod ident;
+mod lit;
 mod span;
 mod token;
 mod tree;
 
+/// Abstract syntax tree definition.
+pub mod ast {
+    use super::*;
+    pub use expr::*;
+    pub use lit::*;
+    pub use tree::*;
+}
+
+pub use ast::*;
+pub use ident::*;
 pub use span::*;
 pub use token::*;
-pub use tree::*;
 
 /// Decorations for semantic syntax highlighting.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
diff --git a/src/syntax/span.rs b/src/syntax/span.rs
index eb029479..62929706 100644
--- a/src/syntax/span.rs
+++ b/src/syntax/span.rs
@@ -42,8 +42,10 @@ impl<T> Offset for SpanVec<T> {
 #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
 #[cfg_attr(feature = "serialize", derive(serde::Serialize))]
 pub struct Spanned<T> {
-    pub span: Span,
+    /// The spanned value.
     pub v: T,
+    /// The location in source code of the value.
+    pub span: Span,
 }
 
 impl<T> Spanned<T> {
diff --git a/src/syntax/tree.rs b/src/syntax/tree.rs
index c4ce3ad2..80bca399 100644
--- a/src/syntax/tree.rs
+++ b/src/syntax/tree.rs
@@ -1,26 +1,15 @@
 //! The syntax tree.
 
-use std::fmt::{self, Debug, Formatter};
-use std::ops::Deref;
-
-use unicode_xid::UnicodeXID;
-
-use super::span::{SpanVec, SpanWith, Spanned};
-use super::Decoration;
-use crate::color::RgbaColor;
-use crate::compute::dict::{Dict, SpannedEntry};
-use crate::compute::value::{DictValue, Value};
-use crate::layout::LayoutContext;
-use crate::length::Length;
-use crate::{DynFuture, Feedback};
+use super::span::{SpanVec, Spanned};
+use super::{Expr, Ident};
 
 /// A collection of nodes which form a tree together with the nodes' children.
-pub type SyntaxTree = SpanVec<SyntaxNode>;
+pub type SynTree = SpanVec<SynNode>;
 
 /// A syntax node, which encompasses a single logical entity of parsed source
 /// code.
 #[derive(Debug, Clone, PartialEq)]
-pub enum SyntaxNode {
+pub enum SynNode {
     /// Whitespace containing less than two newlines.
     Spacing,
     /// A forced line break.
@@ -34,11 +23,11 @@ pub enum SyntaxNode {
     /// Plain text.
     Text(String),
     /// An optionally syntax-highlighted raw block.
-    Raw(Raw),
-    /// Section headings.
-    Heading(Heading),
-    /// A function call.
-    Call(CallExpr),
+    Raw(NodeRaw),
+    /// A section heading.
+    Heading(NodeHeading),
+    /// An expression.
+    Expr(Expr),
 }
 
 /// A raw block, rendered in monospace with optional syntax highlighting.
@@ -103,7 +92,7 @@ pub enum SyntaxNode {
 ///   you can always force leading or trailing whitespace simply by adding more
 ///   spaces.
 #[derive(Debug, Clone, PartialEq)]
-pub struct Raw {
+pub struct NodeRaw {
     /// An optional identifier specifying the language to syntax-highlight in.
     pub lang: Option<Ident>,
     /// The lines of raw text, determined as the raw string between the
@@ -122,221 +111,9 @@ pub struct Raw {
 
 /// A section heading.
 #[derive(Debug, Clone, PartialEq)]
-pub struct Heading {
+pub struct NodeHeading {
     /// The section depth (how many hashtags minus 1).
     pub level: Spanned<u8>,
-    pub tree: SyntaxTree,
-}
-
-/// An expression.
-#[derive(Clone, PartialEq)]
-pub enum Expr {
-    /// An identifier: `ident`.
-    Ident(Ident),
-    /// A string: `"string"`.
-    Str(String),
-    /// A boolean: `true, false`.
-    Bool(bool),
-    /// A number: `1.2, 200%`.
-    Number(f64),
-    /// A length: `2cm, 5.2in`.
-    Length(Length),
-    /// A color value with alpha channel: `#f79143ff`.
-    Color(RgbaColor),
-    /// A dictionary expression: `(false, 12cm, greeting="hi")`.
-    Dict(DictExpr),
-    /// A syntax tree containing typesetting content.
-    Tree(SyntaxTree),
-    /// A function call expression: `cmyk(37.7, 0, 3.9, 1.1)`.
-    Call(CallExpr),
-    /// An operation that negates the contained expression.
-    Neg(Box<Spanned<Expr>>),
-    /// An operation that adds the contained expressions.
-    Add(Box<Spanned<Expr>>, Box<Spanned<Expr>>),
-    /// An operation that subtracts the contained expressions.
-    Sub(Box<Spanned<Expr>>, Box<Spanned<Expr>>),
-    /// An operation that multiplies the contained expressions.
-    Mul(Box<Spanned<Expr>>, Box<Spanned<Expr>>),
-    /// An operation that divides the contained expressions.
-    Div(Box<Spanned<Expr>>, Box<Spanned<Expr>>),
-}
-
-impl Expr {
-    /// A natural-language name of the type of this expression, e.g.
-    /// "identifier".
-    pub fn name(&self) -> &'static str {
-        use Expr::*;
-        match self {
-            Ident(_) => "identifier",
-            Str(_) => "string",
-            Bool(_) => "bool",
-            Number(_) => "number",
-            Length(_) => "length",
-            Color(_) => "color",
-            Dict(_) => "dictg",
-            Tree(_) => "syntax tree",
-            Call(_) => "function call",
-            Neg(_) => "negation",
-            Add(_, _) => "addition",
-            Sub(_, _) => "subtraction",
-            Mul(_, _) => "multiplication",
-            Div(_, _) => "division",
-        }
-    }
-
-    /// Evaluate the expression to a value.
-    pub async fn eval(&self, ctx: &LayoutContext<'_>, f: &mut Feedback) -> Value {
-        use Expr::*;
-        match self {
-            Ident(i) => Value::Ident(i.clone()),
-            Str(s) => Value::Str(s.clone()),
-            &Bool(b) => Value::Bool(b),
-            &Number(n) => Value::Number(n),
-            &Length(s) => Value::Length(s),
-            &Color(c) => Value::Color(c),
-            Dict(t) => Value::Dict(t.eval(ctx, f).await),
-            Tree(t) => Value::Tree(t.clone()),
-            Call(call) => call.eval(ctx, f).await,
-            Neg(_) => todo!("eval neg"),
-            Add(_, _) => todo!("eval add"),
-            Sub(_, _) => todo!("eval sub"),
-            Mul(_, _) => todo!("eval mul"),
-            Div(_, _) => todo!("eval div"),
-        }
-    }
-}
-
-impl Debug for Expr {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        use Expr::*;
-        match self {
-            Ident(i) => i.fmt(f),
-            Str(s) => s.fmt(f),
-            Bool(b) => b.fmt(f),
-            Number(n) => n.fmt(f),
-            Length(s) => s.fmt(f),
-            Color(c) => c.fmt(f),
-            Dict(t) => t.fmt(f),
-            Tree(t) => t.fmt(f),
-            Call(c) => c.fmt(f),
-            Neg(e) => write!(f, "-{:?}", e),
-            Add(a, b) => write!(f, "({:?} + {:?})", a, b),
-            Sub(a, b) => write!(f, "({:?} - {:?})", a, b),
-            Mul(a, b) => write!(f, "({:?} * {:?})", a, b),
-            Div(a, b) => write!(f, "({:?} / {:?})", a, b),
-        }
-    }
-}
-
-/// An identifier as defined by unicode with a few extra permissible characters.
-#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
-pub struct Ident(pub String);
-
-impl Ident {
-    /// Create a new identifier from a string checking that it is a valid.
-    pub fn new(ident: impl AsRef<str> + Into<String>) -> Option<Self> {
-        if is_ident(ident.as_ref()) {
-            Some(Self(ident.into()))
-        } else {
-            None
-        }
-    }
-
-    /// Return a reference to the underlying string.
-    pub fn as_str(&self) -> &str {
-        self
-    }
-}
-
-impl AsRef<str> for Ident {
-    fn as_ref(&self) -> &str {
-        self
-    }
-}
-
-impl Deref for Ident {
-    type Target = str;
-
-    fn deref(&self) -> &Self::Target {
-        self.0.as_str()
-    }
-}
-
-impl Debug for Ident {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "`{}`", self.0)
-    }
-}
-
-/// Whether the string is a valid identifier.
-pub fn is_ident(string: &str) -> bool {
-    fn is_ok(c: char) -> bool {
-        c == '-' || c == '_'
-    }
-
-    let mut chars = string.chars();
-    if matches!(chars.next(), Some(c) if c.is_xid_start() || is_ok(c)) {
-        chars.all(|c| c.is_xid_continue() || is_ok(c))
-    } else {
-        false
-    }
-}
-
-/// A dictionary of expressions.
-///
-/// # Example
-/// ```typst
-/// (false, 12cm, greeting="hi")
-/// ```
-pub type DictExpr = Dict<SpannedEntry<Expr>>;
-
-impl DictExpr {
-    /// Evaluate the dictionary expression to a dictionary value.
-    pub fn eval<'a>(
-        &'a self,
-        ctx: &'a LayoutContext<'a>,
-        f: &'a mut Feedback,
-    ) -> DynFuture<'a, DictValue> {
-        Box::pin(async move {
-            let mut dict = DictValue::new();
-
-            for (key, entry) in self.iter() {
-                let val = entry.val.v.eval(ctx, f).await;
-                let spanned = val.span_with(entry.val.span);
-                let entry = SpannedEntry::new(entry.key, spanned);
-                dict.insert(key, entry);
-            }
-
-            dict
-        })
-    }
-}
-
-/// An invocation of a function.
-#[derive(Debug, Clone, PartialEq)]
-pub struct CallExpr {
-    pub name: Spanned<Ident>,
-    pub args: DictExpr,
-}
-
-impl CallExpr {
-    /// Evaluate the call expression to a value.
-    pub async fn eval(&self, ctx: &LayoutContext<'_>, f: &mut Feedback) -> Value {
-        let name = &self.name.v;
-        let span = self.name.span;
-        let args = self.args.eval(ctx, f).await;
-
-        if let Some(func) = ctx.scope.func(name) {
-            let pass = func(span, args, ctx.clone()).await;
-            f.extend(pass.feedback);
-            f.decorations.push(Decoration::Resolved.span_with(span));
-            pass.output
-        } else {
-            if !name.is_empty() {
-                error!(@f, span, "unknown function");
-                f.decorations.push(Decoration::Unresolved.span_with(span));
-            }
-            Value::Dict(args)
-        }
-    }
+    /// The contents of the heading.
+    pub contents: SynTree,
 }