Fine-grained capturing

src/eval/capture.rs

@@ -1,32 +1,23 @@
 use std::rc::Rc;
 
-use super::{Scope, Scopes};
+use super::{Scope, Scopes, Value};
-use crate::syntax::{NodeKind, RedRef};
+use crate::syntax::ast::{ClosureParam, Expr, Ident, Imports, TypedNode};
+use crate::syntax::RedRef;
 
 /// A visitor that captures variable slots.
 pub struct CapturesVisitor<'a> {
     external: &'a Scopes<'a>,
+    internal: Scopes<'a>,
     captures: Scope,
 }
 
 impl<'a> CapturesVisitor<'a> {
     /// Create a new visitor for the given external scopes.
     pub fn new(external: &'a Scopes) -> Self {
-        Self { external, captures: Scope::new() }
+        Self {
-    }
+            external,
-
+            internal: Scopes::new(None),
-    pub fn visit(&mut self, node: RedRef) {
+            captures: Scope::new(),
-        match node.kind() {
-            NodeKind::Ident(ident) => {
-                if let Some(slot) = self.external.get(ident.as_str()) {
-                    self.captures.def_slot(ident.as_str(), Rc::clone(slot));
-                }
-            }
-            _ => {
-                for child in node.children() {
-                    self.visit(child);
-                }
-            }
         }
     }
 
@@ -34,4 +25,152 @@ impl<'a> CapturesVisitor<'a> {
     pub fn finish(self) -> Scope {
         self.captures
     }
+
+    /// Bind a new internal variable.
+    pub fn bind(&mut self, ident: Ident) {
+        self.internal.def_mut(ident.take(), Value::None);
+    }
+
+    /// Capture a variable if it isn't internal.
+    pub fn capture(&mut self, ident: Ident) {
+        if self.internal.get(&ident).is_none() {
+            if let Some(slot) = self.external.get(&ident) {
+                self.captures.def_slot(ident.take(), Rc::clone(slot));
+            }
+        }
+    }
+
+    /// Visit any node and collect all captured variables.
+    pub fn visit(&mut self, node: RedRef) {
+        match node.cast() {
+            // Every identifier is a potential variable that we need to capture.
+            // Identifiers that shouldn't count as captures because they
+            // actually bind a new name are handled further below (individually
+            // through the expressions that contain them).
+            Some(Expr::Ident(ident)) => self.capture(ident),
+
+            // A closure contains parameter bindings, which are bound before the
+            // body is evaluated. Take must be taken so that the default values
+            // of named parameters cannot access previous parameter bindings.
+            Some(Expr::Closure(expr)) => {
+                for param in expr.params() {
+                    if let ClosureParam::Named(named) = param {
+                        self.visit(named.expr().as_red());
+                    }
+                }
+
+                for param in expr.params() {
+                    match param {
+                        ClosureParam::Pos(ident) => self.bind(ident),
+                        ClosureParam::Named(named) => self.bind(named.name()),
+                        ClosureParam::Sink(ident) => self.bind(ident),
+                    }
+                }
+
+                self.visit(expr.body().as_red());
+            }
+
+            // A let expression contains a binding, but that binding is only
+            // active after the body is evaluated.
+            Some(Expr::Let(expr)) => {
+                if let Some(init) = expr.init() {
+                    self.visit(init.as_red());
+                }
+                self.bind(expr.binding());
+            }
+
+            // A for loop contains one or two bindings in its pattern. These are
+            // active after the iterable is evaluated but before the body is
+            // evaluated.
+            Some(Expr::For(expr)) => {
+                self.visit(expr.iter().as_red());
+                let pattern = expr.pattern();
+                if let Some(key) = pattern.key() {
+                    self.bind(key);
+                }
+                self.bind(pattern.value());
+                self.visit(expr.body().as_red());
+            }
+
+            // An import contains items, but these are active only after the
+            // path is evaluated.
+            Some(Expr::Import(expr)) => {
+                self.visit(expr.path().as_red());
+                if let Imports::Items(items) = expr.imports() {
+                    for item in items {
+                        self.bind(item);
+                    }
+                }
+            }
+
+            // Blocks and templates create a scope.
+            Some(Expr::Block(_) | Expr::Template(_)) => {
+                self.internal.enter();
+                for child in node.children() {
+                    self.visit(child);
+                }
+                self.internal.exit();
+            }
+
+            // Everything else is traversed from left to right.
+            _ => {
+                for child in node.children() {
+                    self.visit(child);
+                }
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::parse::parse;
+    use crate::source::SourceId;
+    use crate::syntax::RedNode;
+
+    #[track_caller]
+    fn test(src: &str, result: &[&str]) {
+        let green = parse(src);
+        let red = RedNode::from_root(green, SourceId::from_raw(0));
+
+        let mut scopes = Scopes::new(None);
+        scopes.def_const("x", 0);
+        scopes.def_const("y", 0);
+        scopes.def_const("z", 0);
+
+        let mut visitor = CapturesVisitor::new(&scopes);
+        visitor.visit(red.as_ref());
+
+        let captures = visitor.finish();
+        let mut names: Vec<_> = captures.iter().map(|(k, _)| k).collect();
+        names.sort();
+
+        assert_eq!(names, result);
+    }
+
+    #[test]
+    fn test_captures() {
+        // Let binding and function definition.
+        test("#let x = x", &["x"]);
+        test("#let x; {x + y}", &["y"]);
+        test("#let f(x, y) = x + y", &[]);
+
+        // Closure with different kinds of params.
+        test("{(x, y) => x + z}", &["z"]);
+        test("{(x: y, z) => x + z}", &["y"]);
+        test("{(..x) => x + y}", &["y"]);
+        test("{(x, y: x + z) => x + y}", &["x", "z"]);
+
+        // For loop.
+        test("#for x in y { x + z }", &["y", "z"]);
+        test("#for x, y in y { x + y }", &["y"]);
+
+        // Import.
+        test("#import x, y from z", &["z"]);
+        test("#import x, y, z from x + y", &["x", "y"]);
+
+        // Scoping.
+        test("{ let x = 1; { let y = 2; y }; x + y }", &["y"]);
+    }
 }

src/eval/mod.rs

@@ -174,8 +174,8 @@ impl Eval for Expr {
 
     fn eval(&self, ctx: &mut EvalContext) -> TypResult<Self::Output> {
         match self {
-            Self::Ident(v) => v.eval(ctx),
             Self::Lit(v) => v.eval(ctx),
+            Self::Ident(v) => v.eval(ctx),
             Self::Array(v) => v.eval(ctx).map(Value::Array),
             Self::Dict(v) => v.eval(ctx).map(Value::Dict),
             Self::Template(v) => v.eval(ctx).map(Value::Template),
@@ -200,17 +200,17 @@ impl Eval for Lit {
     type Output = Value;
 
     fn eval(&self, _: &mut EvalContext) -> TypResult<Self::Output> {
-        Ok(match *self {
+        Ok(match self.kind() {
-            Self::None(_) => Value::None,
+            LitKind::None => Value::None,
-            Self::Auto(_) => Value::Auto,
+            LitKind::Auto => Value::Auto,
-            Self::Bool(_, v) => Value::Bool(v),
+            LitKind::Bool(v) => Value::Bool(v),
-            Self::Int(_, v) => Value::Int(v),
+            LitKind::Int(v) => Value::Int(v),
-            Self::Float(_, v) => Value::Float(v),
+            LitKind::Float(v) => Value::Float(v),
-            Self::Length(_, v, unit) => Value::Length(Length::with_unit(v, unit)),
+            LitKind::Length(v, unit) => Value::Length(Length::with_unit(v, unit)),
-            Self::Angle(_, v, unit) => Value::Angle(Angle::with_unit(v, unit)),
+            LitKind::Angle(v, unit) => Value::Angle(Angle::with_unit(v, unit)),
-            Self::Percent(_, v) => Value::Relative(Relative::new(v / 100.0)),
+            LitKind::Percent(v) => Value::Relative(Relative::new(v / 100.0)),
-            Self::Fractional(_, v) => Value::Fractional(Fractional::new(v)),
+            LitKind::Fractional(v) => Value::Fractional(Fractional::new(v)),
-            Self::Str(_, ref v) => Value::Str(v.into()),
+            LitKind::Str(ref v) => Value::Str(v.into()),
         })
     }
 }
@@ -219,9 +219,9 @@ impl Eval for Ident {
     type Output = Value;
 
     fn eval(&self, ctx: &mut EvalContext) -> TypResult<Self::Output> {
-        match ctx.scopes.get(&self.string) {
+        match ctx.scopes.get(self) {
             Some(slot) => Ok(slot.borrow().clone()),
-            None => bail!(self.span, "unknown variable"),
+            None => bail!(self.span(), "unknown variable"),
         }
     }
 }
@@ -239,7 +239,7 @@ impl Eval for DictExpr {
 
     fn eval(&self, ctx: &mut EvalContext) -> TypResult<Self::Output> {
         self.items()
-            .map(|x| Ok((x.name().string.into(), x.expr().eval(ctx)?)))
+            .map(|x| Ok((x.name().take().into(), x.expr().eval(ctx)?)))
             .collect()
     }
 }
@@ -401,7 +401,7 @@ impl Eval for CallArgs {
                 CallArg::Named(x) => {
                     items.push(Arg {
                         span,
-                        name: Some(x.name().string.into()),
+                        name: Some(x.name().take().into()),
                         value: Spanned::new(x.expr().eval(ctx)?, x.expr().span()),
                     });
                 }
@@ -457,23 +457,23 @@ impl Eval for ClosureExpr {
         for param in self.params() {
             match param {
                 ClosureParam::Pos(name) => {
-                    params.push((name.string, None));
+                    params.push((name.take(), None));
                 }
                 ClosureParam::Named(named) => {
-                    params.push((named.name().string, Some(named.expr().eval(ctx)?)));
+                    params.push((named.name().take(), Some(named.expr().eval(ctx)?)));
                 }
                 ClosureParam::Sink(name) => {
                     if sink.is_some() {
-                        bail!(name.span, "only one argument sink is allowed");
+                        bail!(name.span(), "only one argument sink is allowed");
                     }
-                    sink = Some(name.string);
+                    sink = Some(name.take());
                 }
             }
         }
 
         // Clone the body expression so that we don't have a lifetime
         // dependence on the AST.
-        let name = self.name().map(|name| name.string);
+        let name = self.name().map(Ident::take);
         let body = self.body();
 
         // Define the actual function.
@@ -533,7 +533,7 @@ impl Eval for LetExpr {
             Some(expr) => expr.eval(ctx)?,
             None => Value::None,
         };
-        ctx.scopes.def_mut(self.binding().string, value);
+        ctx.scopes.def_mut(self.binding().take(), value);
         Ok(Value::None)
     }
 }
@@ -589,7 +589,7 @@ impl Eval for ForExpr {
 
                 #[allow(unused_parens)]
                 for ($($value),*) in $iter {
-                    $(ctx.scopes.def_mut(&$binding.string, $value);)*
+                    $(ctx.scopes.def_mut(&$binding, $value);)*
 
                     let value = self.body().eval(ctx)?;
                     output = ops::join(output, value)
@@ -603,7 +603,10 @@ impl Eval for ForExpr {
 
         let iter = self.iter().eval(ctx)?;
         let pattern = self.pattern();
-        match (pattern.key(), pattern.value(), iter) {
+        let key = pattern.key().map(Ident::take);
+        let value = pattern.value().take();
+
+        match (key, value, iter) {
             (None, v, Value::Str(string)) => iter!(for (v => value) in string.iter()),
             (None, v, Value::Array(array)) => {
                 iter!(for (v => value) in array.into_iter())
@@ -644,10 +647,10 @@ impl Eval for ImportExpr {
             }
             Imports::Items(idents) => {
                 for ident in idents {
-                    if let Some(slot) = module.scope.get(&ident.string) {
+                    if let Some(slot) = module.scope.get(&ident) {
-                        ctx.scopes.def_mut(ident.string, slot.borrow().clone());
+                        ctx.scopes.def_mut(ident.take(), slot.borrow().clone());
                     } else {
-                        bail!(ident.span, "unresolved import");
+                        bail!(ident.span(), "unresolved import");
                     }
                 }
             }
@@ -691,12 +694,12 @@ impl Access for Expr {
 
 impl Access for Ident {
     fn access<'a>(&self, ctx: &'a mut EvalContext) -> TypResult<RefMut<'a, Value>> {
-        match ctx.scopes.get(&self.string) {
+        match ctx.scopes.get(self) {
             Some(slot) => match slot.try_borrow_mut() {
                 Ok(guard) => Ok(guard),
-                Err(_) => bail!(self.span, "cannot mutate a constant"),
+                Err(_) => bail!(self.span(), "cannot mutate a constant"),
             },
-            None => bail!(self.span, "unknown variable"),
+            None => bail!(self.span(), "unknown variable"),
         }
     }
 }

src/eval/scope.rs

@@ -120,6 +120,8 @@ impl Scope {
 
 impl Debug for Scope {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        self.values.fmt(f)
+        f.debug_map()
+            .entries(self.values.iter().map(|(k, v)| (k, v.borrow())))
+            .finish()
     }
 }

src/geom/relative.rs

@@ -3,7 +3,7 @@ use super::*;
 /// A relative length.
 ///
 /// _Note_: `50%` is represented as `0.5` here, but stored as `50.0` in the
-/// corresponding [literal](crate::syntax::ast::Lit::Percent).
+/// corresponding [literal](crate::syntax::ast::LitKind::Percent).
 #[derive(Default, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
 pub struct Relative(N64);
 

src/parse/mod.rs

@@ -418,7 +418,7 @@ fn item(p: &mut Parser) -> ParseResult<NodeKind> {
 
     if p.at(&NodeKind::Colon) {
         marker.perform(p, NodeKind::Named, |p| {
-            if matches!(marker.peek(p).unwrap().kind(), &NodeKind::Ident(_)) {
+            if let Some(NodeKind::Ident(_)) = marker.peek(p).map(|c| c.kind()) {
                 p.eat();
                 expr(p)
             } else {

src/source.rs

@@ -145,7 +145,7 @@ impl SourceFile {
     }
 
     pub fn ast(&self) -> TypResult<Markup> {
-        let red = RedNode::new_root(self.root.clone(), self.id);
+        let red = RedNode::from_root(self.root.clone(), self.id);
         let errors = red.errors();
         if errors.is_empty() {
             Ok(red.cast().unwrap())

src/syntax/ast.rs

@@ -1,6 +1,8 @@
 //! A typed layer over the red-green tree.
 
-use super::{NodeKind, RedNode, RedRef, Span};
+use std::ops::Deref;
+
+use super::{Green, GreenData, NodeKind, RedNode, RedRef, Span};
 use crate::geom::{AngularUnit, LengthUnit};
 use crate::util::EcoString;
 
@@ -8,13 +10,24 @@ use crate::util::EcoString;
 pub trait TypedNode: Sized {
     /// Convert from a red node to a typed node.
     fn from_red(value: RedRef) -> Option<Self>;
+
+    /// A reference to the underlying red node.
+    fn as_red(&self) -> RedRef<'_>;
+
+    /// The source code location.
+    fn span(&self) -> Span {
+        self.as_red().span()
+    }
 }
 
 macro_rules! node {
     ($(#[$attr:meta])* $name:ident) => {
-        node!{$(#[$attr])* $name => $name}
+        node!{$(#[$attr])* $name: $name}
     };
-    ($(#[$attr:meta])* $variant:ident => $name:ident) => {
+    ($(#[$attr:meta])* $name:ident: $variant:ident) => {
+        node!{$(#[$attr])* $name: NodeKind::$variant}
+    };
+    ($(#[$attr:meta])* $name:ident: $($variant:pat)|*) => {
         #[derive(Debug, Clone, PartialEq)]
         #[repr(transparent)]
         $(#[$attr])*
@@ -22,22 +35,14 @@ macro_rules! node {
 
         impl TypedNode for $name {
             fn from_red(node: RedRef) -> Option<Self> {
-                if node.kind() != &NodeKind::$variant {
+                if matches!(node.kind(), $($variant)|*) {
-                    return None;
-                }
-
                     Some(Self(node.own()))
+                } else {
+                    None
                 }
             }
 
-        impl $name {
+            fn as_red(&self) -> RedRef<'_> {
-            /// The source code location.
-            pub fn span(&self) -> Span {
-                self.0.span()
-            }
-
-            /// The underlying red node.
-            pub fn as_red(&self) -> RedRef {
                 self.0.as_ref()
             }
         }
@@ -52,7 +57,27 @@ node! {
 impl Markup {
     /// The markup nodes.
     pub fn nodes(&self) -> impl Iterator<Item = MarkupNode> + '_ {
-        self.0.children().filter_map(RedRef::cast)
+        self.0.children().filter_map(|node| match node.kind() {
+            NodeKind::Space(_) => Some(MarkupNode::Space),
+            NodeKind::Linebreak => Some(MarkupNode::Linebreak),
+            NodeKind::Parbreak => Some(MarkupNode::Parbreak),
+            NodeKind::Strong => Some(MarkupNode::Strong),
+            NodeKind::Emph => Some(MarkupNode::Emph),
+            NodeKind::Text(s) => Some(MarkupNode::Text(s.clone())),
+            NodeKind::UnicodeEscape(c) => Some(MarkupNode::Text((*c).into())),
+            NodeKind::EnDash => Some(MarkupNode::Text("\u{2013}".into())),
+            NodeKind::EmDash => Some(MarkupNode::Text("\u{2014}".into())),
+            NodeKind::NonBreakingSpace => Some(MarkupNode::Text("\u{00A0}".into())),
+            NodeKind::Raw(raw) => Some(MarkupNode::Raw(RawNode {
+                block: raw.block,
+                lang: raw.lang.clone(),
+                text: raw.text.clone(),
+            })),
+            NodeKind::Heading => node.cast().map(MarkupNode::Heading),
+            NodeKind::List => node.cast().map(MarkupNode::List),
+            NodeKind::Enum => node.cast().map(MarkupNode::Enum),
+            _ => node.cast().map(MarkupNode::Expr),
+        })
     }
 }
 
@@ -83,28 +108,6 @@ pub enum MarkupNode {
     Expr(Expr),
 }
 
-impl TypedNode for MarkupNode {
-    fn from_red(node: RedRef) -> Option<Self> {
-        match node.kind() {
-            NodeKind::Space(_) => Some(MarkupNode::Space),
-            NodeKind::Linebreak => Some(MarkupNode::Linebreak),
-            NodeKind::Parbreak => Some(MarkupNode::Parbreak),
-            NodeKind::Strong => Some(MarkupNode::Strong),
-            NodeKind::Emph => Some(MarkupNode::Emph),
-            NodeKind::Text(s) => Some(MarkupNode::Text(s.clone())),
-            NodeKind::UnicodeEscape(c) => Some(MarkupNode::Text((*c).into())),
-            NodeKind::EnDash => Some(MarkupNode::Text("\u{2013}".into())),
-            NodeKind::EmDash => Some(MarkupNode::Text("\u{2014}".into())),
-            NodeKind::NonBreakingSpace => Some(MarkupNode::Text("\u{00A0}".into())),
-            NodeKind::Raw(_) => node.cast().map(MarkupNode::Raw),
-            NodeKind::Heading => node.cast().map(MarkupNode::Heading),
-            NodeKind::List => node.cast().map(MarkupNode::List),
-            NodeKind::Enum => node.cast().map(MarkupNode::Enum),
-            _ => node.cast().map(MarkupNode::Expr),
-        }
-    }
-}
-
 /// A raw block with optional syntax highlighting: `` `...` ``.
 #[derive(Debug, Clone, PartialEq)]
 pub struct RawNode {
@@ -118,22 +121,9 @@ pub struct RawNode {
     pub block: bool,
 }
 
-impl TypedNode for RawNode {
-    fn from_red(node: RedRef) -> Option<Self> {
-        match node.kind() {
-            NodeKind::Raw(raw) => Some(Self {
-                block: raw.block,
-                lang: raw.lang.clone(),
-                text: raw.text.clone(),
-            }),
-            _ => None,
-        }
-    }
-}
-
 node! {
     /// A section heading: `= Introduction`.
-    Heading => HeadingNode
+    HeadingNode: Heading
 }
 
 impl HeadingNode {
@@ -154,7 +144,7 @@ impl HeadingNode {
 
 node! {
     /// An item in an unordered list: `- ...`.
-    List => ListNode
+    ListNode: List
 }
 
 impl ListNode {
@@ -166,7 +156,7 @@ impl ListNode {
 
 node! {
     /// An item in an enumeration (ordered list): `1. ...`.
-    Enum => EnumNode
+    EnumNode: Enum
 }
 
 impl EnumNode {
@@ -190,10 +180,10 @@ impl EnumNode {
 /// An expression.
 #[derive(Debug, Clone, PartialEq)]
 pub enum Expr {
-    /// An identifier: `left`.
-    Ident(Ident),
     /// A literal: `1`, `true`, ...
     Lit(Lit),
+    /// An identifier: `left`.
+    Ident(Ident),
     /// An array expression: `(1, "hi", 12cm)`.
     Array(ArrayExpr),
     /// A dictionary expression: `(thickness: 3pt, pattern: dashed)`.
@@ -251,6 +241,29 @@ impl TypedNode for Expr {
             _ => node.cast().map(Self::Lit),
         }
     }
+
+    fn as_red(&self) -> RedRef<'_> {
+        match self {
+            Self::Lit(v) => v.as_red(),
+            Self::Ident(v) => v.as_red(),
+            Self::Array(v) => v.as_red(),
+            Self::Dict(v) => v.as_red(),
+            Self::Template(v) => v.as_red(),
+            Self::Group(v) => v.as_red(),
+            Self::Block(v) => v.as_red(),
+            Self::Unary(v) => v.as_red(),
+            Self::Binary(v) => v.as_red(),
+            Self::Call(v) => v.as_red(),
+            Self::Closure(v) => v.as_red(),
+            Self::With(v) => v.as_red(),
+            Self::Let(v) => v.as_red(),
+            Self::If(v) => v.as_red(),
+            Self::While(v) => v.as_red(),
+            Self::For(v) => v.as_red(),
+            Self::Import(v) => v.as_red(),
+            Self::Include(v) => v.as_red(),
+        }
+    }
 }
 
 impl Expr {
@@ -267,99 +280,72 @@ impl Expr {
             | Self::Include(_)
         )
     }
-
-    /// Return the expression's span.
-    pub fn span(&self) -> Span {
-        match self {
-            Self::Ident(ident) => ident.span,
-            Self::Lit(lit) => lit.span(),
-            Self::Array(array) => array.span(),
-            Self::Dict(dict) => dict.span(),
-            Self::Template(template) => template.span(),
-            Self::Group(group) => group.span(),
-            Self::Block(block) => block.span(),
-            Self::Unary(unary) => unary.span(),
-            Self::Binary(binary) => binary.span(),
-            Self::Call(call) => call.span(),
-            Self::Closure(closure) => closure.span(),
-            Self::With(with) => with.span(),
-            Self::Let(let_) => let_.span(),
-            Self::If(if_) => if_.span(),
-            Self::While(while_) => while_.span(),
-            Self::For(for_) => for_.span(),
-            Self::Import(import) => import.span(),
-            Self::Include(include) => include.span(),
-        }
-    }
 }
 
+node! {
     /// A literal: `1`, `true`, ...
+    Lit: NodeKind::None
+       | NodeKind::Auto
+       | NodeKind::Bool(_)
+       | NodeKind::Int(_)
+       | NodeKind::Float(_)
+       | NodeKind::Length(_, _)
+       | NodeKind::Angle(_, _)
+       | NodeKind::Percentage(_)
+       | NodeKind::Fraction(_)
+       | NodeKind::Str(_)
+}
+
+impl Lit {
+    /// The kind of literal.
+    pub fn kind(&self) -> LitKind {
+        match *self.0.kind() {
+            NodeKind::None => LitKind::None,
+            NodeKind::Auto => LitKind::Auto,
+            NodeKind::Bool(v) => LitKind::Bool(v),
+            NodeKind::Int(v) => LitKind::Int(v),
+            NodeKind::Float(v) => LitKind::Float(v),
+            NodeKind::Length(v, unit) => LitKind::Length(v, unit),
+            NodeKind::Angle(v, unit) => LitKind::Angle(v, unit),
+            NodeKind::Percentage(v) => LitKind::Percent(v),
+            NodeKind::Fraction(v) => LitKind::Fractional(v),
+            NodeKind::Str(ref v) => LitKind::Str(v.clone()),
+            _ => panic!("literal is of wrong kind"),
+        }
+    }
+}
+
+/// The kind of a literal.
 #[derive(Debug, Clone, PartialEq)]
-pub enum Lit {
+pub enum LitKind {
     /// The none literal: `none`.
-    None(Span),
+    None,
     /// The auto literal: `auto`.
-    Auto(Span),
+    Auto,
     /// A boolean literal: `true`, `false`.
-    Bool(Span, bool),
+    Bool(bool),
     /// An integer literal: `120`.
-    Int(Span, i64),
+    Int(i64),
     /// A floating-point literal: `1.2`, `10e-4`.
-    Float(Span, f64),
+    Float(f64),
     /// A length literal: `12pt`, `3cm`.
-    Length(Span, f64, LengthUnit),
+    Length(f64, LengthUnit),
     /// An angle literal:  `1.5rad`, `90deg`.
-    Angle(Span, f64, AngularUnit),
+    Angle(f64, AngularUnit),
     /// A percent literal: `50%`.
     ///
     /// _Note_: `50%` is stored as `50.0` here, but as `0.5` in the
     /// corresponding [value](crate::geom::Relative).
-    Percent(Span, f64),
+    Percent(f64),
     /// A fraction unit literal: `1fr`.
-    Fractional(Span, f64),
+    Fractional(f64),
     /// A string literal: `"hello!"`.
-    Str(Span, EcoString),
+    Str(EcoString),
-}
-
-impl TypedNode for Lit {
-    fn from_red(node: RedRef) -> Option<Self> {
-        match *node.kind() {
-            NodeKind::None => Some(Self::None(node.span())),
-            NodeKind::Auto => Some(Self::Auto(node.span())),
-            NodeKind::Bool(v) => Some(Self::Bool(node.span(), v)),
-            NodeKind::Int(v) => Some(Self::Int(node.span(), v)),
-            NodeKind::Float(v) => Some(Self::Float(node.span(), v)),
-            NodeKind::Length(v, unit) => Some(Self::Length(node.span(), v, unit)),
-            NodeKind::Angle(v, unit) => Some(Self::Angle(node.span(), v, unit)),
-            NodeKind::Percentage(v) => Some(Self::Percent(node.span(), v)),
-            NodeKind::Fraction(v) => Some(Self::Fractional(node.span(), v)),
-            NodeKind::Str(ref v) => Some(Self::Str(node.span(), v.clone())),
-            _ => None,
-        }
-    }
-}
-
-impl Lit {
-    /// The source code location.
-    pub fn span(&self) -> Span {
-        match *self {
-            Self::None(span) => span,
-            Self::Auto(span) => span,
-            Self::Bool(span, _) => span,
-            Self::Int(span, _) => span,
-            Self::Float(span, _) => span,
-            Self::Length(span, _, _) => span,
-            Self::Angle(span, _, _) => span,
-            Self::Percent(span, _) => span,
-            Self::Fractional(span, _) => span,
-            Self::Str(span, _) => span,
-        }
-    }
 }
 
 node! {
     /// An array expression: `(1, "hi", 12cm)`.
-    Array => ArrayExpr
+    ArrayExpr: Array
 }
 
 impl ArrayExpr {
@@ -371,7 +357,7 @@ impl ArrayExpr {
 
 node! {
     /// A dictionary expression: `(thickness: 3pt, pattern: dashed)`.
-    Dict => DictExpr
+    DictExpr: Dict
 }
 
 impl DictExpr {
@@ -400,7 +386,7 @@ impl Named {
 
 node! {
     /// A template expression: `[*Hi* there!]`.
-    Template => TemplateExpr
+    TemplateExpr: Template
 }
 
 impl TemplateExpr {
@@ -412,7 +398,7 @@ impl TemplateExpr {
 
 node! {
     /// A grouped expression: `(1 + 2)`.
-    Group => GroupExpr
+    GroupExpr: Group
 }
 
 impl GroupExpr {
@@ -424,7 +410,7 @@ impl GroupExpr {
 
 node! {
     /// A block expression: `{ let x = 1; x + 2 }`.
-    Block => BlockExpr
+    BlockExpr: Block
 }
 
 impl BlockExpr {
@@ -436,14 +422,15 @@ impl BlockExpr {
 
 node! {
     /// A unary operation: `-x`.
-    Unary => UnaryExpr
+    UnaryExpr: Unary
 }
 
 impl UnaryExpr {
     /// The operator: `-`.
     pub fn op(&self) -> UnOp {
         self.0
-            .cast_first_child()
+            .children()
+            .find_map(|node| UnOp::from_token(node.kind()))
             .expect("unary expression is missing operator")
     }
 
@@ -464,12 +451,6 @@ pub enum UnOp {
     Not,
 }
 
-impl TypedNode for UnOp {
-    fn from_red(node: RedRef) -> Option<Self> {
-        Self::from_token(node.kind())
-    }
-}
-
 impl UnOp {
     /// Try to convert the token into a unary operation.
     pub fn from_token(token: &NodeKind) -> Option<Self> {
@@ -501,14 +482,15 @@ impl UnOp {
 
 node! {
     /// A binary operation: `a + b`.
-    Binary => BinaryExpr
+    BinaryExpr: Binary
 }
 
 impl BinaryExpr {
     /// The binary operator: `+`.
     pub fn op(&self) -> BinOp {
         self.0
-            .cast_first_child()
+            .children()
+            .find_map(|node| BinOp::from_token(node.kind()))
             .expect("binary expression is missing operator")
     }
 
@@ -566,12 +548,6 @@ pub enum BinOp {
     DivAssign,
 }
 
-impl TypedNode for BinOp {
-    fn from_red(node: RedRef) -> Option<Self> {
-        Self::from_token(node.kind())
-    }
-}
-
 impl BinOp {
     /// Try to convert the token into a binary operation.
     pub fn from_token(token: &NodeKind) -> Option<Self> {
@@ -671,7 +647,7 @@ pub enum Associativity {
 
 node! {
     /// An invocation of a function: `foo(...)`.
-    Call => CallExpr
+    CallExpr: Call
 }
 
 impl CallExpr {
@@ -717,6 +693,14 @@ impl TypedNode for CallArg {
             _ => node.cast().map(CallArg::Pos),
         }
     }
+
+    fn as_red(&self) -> RedRef<'_> {
+        match self {
+            Self::Pos(v) => v.as_red(),
+            Self::Named(v) => v.as_red(),
+            Self::Spread(v) => v.as_red(),
+        }
+    }
 }
 
 impl CallArg {
@@ -732,7 +716,7 @@ impl CallArg {
 
 node! {
     /// A closure expression: `(x, y) => z`.
-    Closure => ClosureExpr
+    ClosureExpr: Closure
 }
 
 impl ClosureExpr {
@@ -779,6 +763,14 @@ impl TypedNode for ClosureParam {
             _ => None,
         }
     }
+
+    fn as_red(&self) -> RedRef<'_> {
+        match self {
+            Self::Pos(v) => v.as_red(),
+            Self::Named(v) => v.as_red(),
+            Self::Sink(v) => v.as_red(),
+        }
+    }
 }
 
 node! {
@@ -840,7 +832,17 @@ node! {
 impl ImportExpr {
     /// The items to be imported.
     pub fn imports(&self) -> Imports {
-        self.0.cast_first_child().expect("import is missing items")
+        self.0
+            .children()
+            .find_map(|node| match node.kind() {
+                NodeKind::Star => Some(Imports::Wildcard),
+                NodeKind::ImportItems => {
+                    let items = node.children().filter_map(RedRef::cast).collect();
+                    Some(Imports::Items(items))
+                }
+                _ => None,
+            })
+            .expect("import is missing items")
     }
 
     /// The location of the importable file.
@@ -858,19 +860,6 @@ pub enum Imports {
     Items(Vec<Ident>),
 }
 
-impl TypedNode for Imports {
-    fn from_red(node: RedRef) -> Option<Self> {
-        match node.kind() {
-            NodeKind::Star => Some(Imports::Wildcard),
-            NodeKind::ImportItems => {
-                let items = node.children().filter_map(RedRef::cast).collect();
-                Some(Imports::Items(items))
-            }
-            _ => None,
-        }
-    }
-}
-
 node! {
     /// An include expression: `include "chapter1.typ"`.
     IncludeExpr
@@ -967,23 +956,28 @@ impl ForPattern {
     }
 }
 
+node! {
     /// An identifier.
-#[derive(Debug, Clone, PartialEq)]
+    Ident: NodeKind::Ident(_)
-pub struct Ident {
-    /// The source code location.
-    pub span: Span,
-    /// The identifier string.
-    pub string: EcoString,
 }
 
-impl TypedNode for Ident {
+impl Ident {
-    fn from_red(node: RedRef) -> Option<Self> {
+    /// Take out the contained [`EcoString`].
-        match node.kind() {
+    pub fn take(self) -> EcoString {
-            NodeKind::Ident(string) => Some(Ident {
+        match self.0.green {
-                span: node.span(),
+            Green::Token(GreenData { kind: NodeKind::Ident(id), .. }) => id,
-                string: string.clone(),
+            _ => panic!("identifier is of wrong kind"),
-            }),
+        }
-            _ => None,
+    }
+}
+
+impl Deref for Ident {
+    type Target = str;
+
+    fn deref(&self) -> &Self::Target {
+        match &self.0.green {
+            Green::Token(GreenData { kind: NodeKind::Ident(id), .. }) => id,
+            _ => panic!("identifier is of wrong kind"),
         }
     }
 }

src/syntax/mod.rs

@@ -187,11 +187,20 @@ pub struct RedNode {
 }
 
 impl RedNode {
-    /// Create a new root node from a [`GreenNode`].
+    /// Create a new red node from a root [`GreenNode`].
-    pub fn new_root(root: Rc<GreenNode>, id: SourceId) -> Self {
+    pub fn from_root(root: Rc<GreenNode>, id: SourceId) -> Self {
         Self { id, offset: 0, green: root.into() }
     }
 
+    /// Create a new red node from a node kind and a span.
+    pub fn from_data(kind: NodeKind, span: Span) -> Self {
+        Self {
+            id: span.source,
+            offset: span.start,
+            green: Green::Token(GreenData { kind, len: span.len() }),
+        }
+    }
+
     /// Convert to a borrowed representation.
     pub fn as_ref(&self) -> RedRef<'_> {
         RedRef {
@@ -540,7 +549,7 @@ pub enum NodeKind {
     /// A percentage: `50%`.
     ///
     /// _Note_: `50%` is stored as `50.0` here, as in the corresponding
-    /// [literal](ast::Lit::Percent).
+    /// [literal](ast::LitKind::Percent).
     Percentage(f64),
     /// A fraction unit: `3fr`.
     Fraction(f64),

src/syntax/pretty.rs

@@ -198,8 +198,8 @@ impl Pretty for EnumNode {
 impl Pretty for Expr {
     fn pretty(&self, p: &mut Printer) {
         match self {
-            Self::Ident(v) => v.pretty(p),
             Self::Lit(v) => v.pretty(p),
+            Self::Ident(v) => v.pretty(p),
             Self::Array(v) => v.pretty(p),
             Self::Dict(v) => v.pretty(p),
             Self::Template(v) => v.pretty(p),
@@ -222,17 +222,17 @@ impl Pretty for Expr {
 
 impl Pretty for Lit {
     fn pretty(&self, p: &mut Printer) {
-        match self {
+        match self.kind() {
-            Self::None(_) => p.push_str("none"),
+            LitKind::None => p.push_str("none"),
-            Self::Auto(_) => p.push_str("auto"),
+            LitKind::Auto => p.push_str("auto"),
-            Self::Bool(_, v) => write!(p, "{}", v).unwrap(),
+            LitKind::Bool(v) => write!(p, "{}", v).unwrap(),
-            Self::Int(_, v) => write!(p, "{}", v).unwrap(),
+            LitKind::Int(v) => write!(p, "{}", v).unwrap(),
-            Self::Float(_, v) => write!(p, "{}", v).unwrap(),
+            LitKind::Float(v) => write!(p, "{}", v).unwrap(),
-            Self::Length(_, v, u) => write!(p, "{}{:?}", v, u).unwrap(),
+            LitKind::Length(v, u) => write!(p, "{}{:?}", v, u).unwrap(),
-            Self::Angle(_, v, u) => write!(p, "{}{:?}", v, u).unwrap(),
+            LitKind::Angle(v, u) => write!(p, "{}{:?}", v, u).unwrap(),
-            Self::Percent(_, v) => write!(p, "{}%", v).unwrap(),
+            LitKind::Percent(v) => write!(p, "{}%", v).unwrap(),
-            Self::Fractional(_, v) => write!(p, "{}fr", v).unwrap(),
+            LitKind::Fractional(v) => write!(p, "{}fr", v).unwrap(),
-            Self::Str(_, v) => write!(p, "{:?}", v).unwrap(),
+            LitKind::Str(v) => write!(p, "{:?}", v).unwrap(),
         }
     }
 }
@@ -508,7 +508,7 @@ impl Pretty for IncludeExpr {
 
 impl Pretty for Ident {
     fn pretty(&self, p: &mut Printer) {
-        p.push_str(&self.string);
+        p.push_str(self);
     }
 }
 

src/syntax/span.rs

@@ -88,6 +88,11 @@ impl Span {
         Self { end, ..self }
     }
 
+    /// The byte length of the spanned region.
+    pub fn len(self) -> usize {
+        self.end - self.start
+    }
+
     /// A new span at the position of this span's start.
     pub fn at_start(&self) -> Span {
         Self::at(self.source, self.start)

tests/typ/code/closure.typ

@@ -56,6 +56,52 @@
   test(f(), 3)
 }
 
+---
+// Import bindings.
+{
+  let b = "target.typ"
+  let f() = {
+    import b from b
+    b
+  }
+  test(f(), 1)
+}
+
+---
+// For loop bindings.
+{
+  let v = (1, 2, 3)
+  let s = 0
+  let f() = {
+    for v in v { s += v }
+  }
+  f()
+  test(s, 6)
+}
+
+---
+// Let + closure bindings.
+{
+  let g = "hi"
+  let f() = {
+    let g() = "bye"
+    g()
+  }
+  test(f(), "bye")
+}
+
+---
+// Parameter bindings.
+{
+  let x = 5
+  let g() = {
+    let f(x, y: x) = x + y
+    f
+  }
+
+  test(g()(8), 13)
+}
+
 ---
 // Don't leak environment.
 {