Expose content representation more

13 files changed, 416 insertions, 385 deletions

diff --git a/src/eval/args.rs b/src/eval/args.rs
index 159e9a77..17bd9cb4 100644
--- a/src/eval/args.rs
+++ b/src/eval/args.rs
@@ -1,10 +1,11 @@
-use std::fmt::{self, Debug, Formatter, Write};
+use std::fmt::{self, Debug, Formatter};
 
-use ecow::EcoVec;
+use ecow::{eco_format, EcoVec};
 
 use super::{Array, Cast, Dict, Str, Value};
 use crate::diag::{bail, At, SourceResult};
 use crate::syntax::{Span, Spanned};
+use crate::util::pretty_array;
 
 /// Evaluated arguments to a function.
 #[derive(Clone, PartialEq, Hash)]
@@ -171,14 +172,9 @@ impl Args {
 
 impl Debug for Args {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        f.write_char('(')?;
-        for (i, arg) in self.items.iter().enumerate() {
-            arg.fmt(f)?;
-            if i + 1 < self.items.len() {
-                f.write_str(", ")?;
-            }
-        }
-        f.write_char(')')
+        let pieces: Vec<_> =
+            self.items.iter().map(|arg| eco_format!("{arg:?}")).collect();
+        f.write_str(&pretty_array(&pieces, false))
     }
 }
 
diff --git a/src/eval/array.rs b/src/eval/array.rs
index 53bae06f..8da9b3d2 100644
--- a/src/eval/array.rs
+++ b/src/eval/array.rs
@@ -1,11 +1,12 @@
 use std::cmp::Ordering;
-use std::fmt::{self, Debug, Formatter, Write};
+use std::fmt::{self, Debug, Formatter};
 use std::ops::{Add, AddAssign};
 
 use ecow::{eco_format, EcoString, EcoVec};
 
 use super::{ops, Args, Func, Value, Vm};
 use crate::diag::{bail, At, SourceResult, StrResult};
+use crate::util::pretty_array;
 
 /// Create a new [`Array`] from values.
 #[macro_export]
@@ -147,7 +148,6 @@ impl Array {
                 return Ok(Some(item.clone()));
             }
         }
-
         Ok(None)
     }
 
@@ -262,6 +262,14 @@ impl Array {
         self.0.iter().cloned().rev().collect()
     }
 
+    /// Split all values in the array.
+    pub fn split(&self, at: Value) -> Array {
+        self.as_slice()
+            .split(|value| *value == at)
+            .map(|subslice| Value::Array(subslice.iter().cloned().collect()))
+            .collect()
+    }
+
     /// Join all values in the array, optionally with separator and last
     /// separator (between the final two items).
     pub fn join(&self, sep: Option<Value>, mut last: Option<Value>) -> StrResult<Value> {
@@ -332,31 +340,10 @@ impl Array {
     }
 }
 
-/// The out of bounds access error message.
-#[cold]
-fn out_of_bounds(index: i64, len: i64) -> EcoString {
-    eco_format!("array index out of bounds (index: {}, len: {})", index, len)
-}
-
-/// The error message when the array is empty.
-#[cold]
-fn array_is_empty() -> EcoString {
-    "array is empty".into()
-}
-
 impl Debug for Array {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        f.write_char('(')?;
-        for (i, value) in self.iter().enumerate() {
-            value.fmt(f)?;
-            if i + 1 < self.0.len() {
-                f.write_str(", ")?;
-            }
-        }
-        if self.len() == 1 {
-            f.write_char(',')?;
-        }
-        f.write_char(')')
+        let pieces: Vec<_> = self.iter().map(|value| eco_format!("{value:?}")).collect();
+        f.write_str(&pretty_array(&pieces, self.len() == 1))
     }
 }
 
@@ -404,3 +391,15 @@ impl<'a> IntoIterator for &'a Array {
         self.iter()
     }
 }
+
+/// The error message when the array is empty.
+#[cold]
+fn array_is_empty() -> EcoString {
+    "array is empty".into()
+}
+
+/// The out of bounds access error message.
+#[cold]
+fn out_of_bounds(index: i64, len: i64) -> EcoString {
+    eco_format!("array index out of bounds (index: {}, len: {})", index, len)
+}
diff --git a/src/eval/dict.rs b/src/eval/dict.rs
index 6c1934c9..ececce07 100644
--- a/src/eval/dict.rs
+++ b/src/eval/dict.rs
@@ -1,5 +1,5 @@
 use std::collections::BTreeMap;
-use std::fmt::{self, Debug, Formatter, Write};
+use std::fmt::{self, Debug, Formatter};
 use std::ops::{Add, AddAssign};
 use std::sync::Arc;
 
@@ -8,7 +8,7 @@ use ecow::{eco_format, EcoString};
 use super::{array, Array, Str, Value};
 use crate::diag::StrResult;
 use crate::syntax::is_ident;
-use crate::util::ArcExt;
+use crate::util::{pretty_array, ArcExt};
 
 /// Create a new [`Dict`] from key-value pairs.
 #[macro_export]
@@ -132,31 +132,24 @@ impl Dict {
     }
 }
 
-/// The missing key access error message.
-#[cold]
-fn missing_key(key: &str) -> EcoString {
-    eco_format!("dictionary does not contain key {:?}", Str::from(key))
-}
-
 impl Debug for Dict {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        f.write_char('(')?;
         if self.is_empty() {
-            f.write_char(':')?;
+            return f.write_str("(:)");
         }
-        for (i, (key, value)) in self.iter().enumerate() {
-            if is_ident(key) {
-                f.write_str(key)?;
-            } else {
-                write!(f, "{key:?}")?;
-            }
-            f.write_str(": ")?;
-            value.fmt(f)?;
-            if i + 1 < self.0.len() {
-                f.write_str(", ")?;
-            }
-        }
-        f.write_char(')')
+
+        let pieces: Vec<_> = self
+            .iter()
+            .map(|(key, value)| {
+                if is_ident(key) {
+                    eco_format!("{key}: {value:?}")
+                } else {
+                    eco_format!("{key:?}: {value:?}")
+                }
+            })
+            .collect();
+
+        f.write_str(&pretty_array(&pieces, false))
     }
 }
 
@@ -207,3 +200,9 @@ impl<'a> IntoIterator for &'a Dict {
         self.iter()
     }
 }
+
+/// The missing key access error message.
+#[cold]
+fn missing_key(key: &str) -> EcoString {
+    eco_format!("dictionary does not contain key {:?}", Str::from(key))
+}
diff --git a/src/eval/func.rs b/src/eval/func.rs
index 79ae142c..8da5c6bc 100644
--- a/src/eval/func.rs
+++ b/src/eval/func.rs
@@ -13,7 +13,7 @@ use super::{
     Vm,
 };
 use crate::diag::{bail, SourceResult, StrResult};
-use crate::model::{Content, NodeId, Selector, StyleMap};
+use crate::model::{NodeId, Selector, StyleMap};
 use crate::syntax::ast::{self, AstNode, Expr};
 use crate::syntax::{SourceId, Span, SyntaxNode};
 use crate::util::hash128;
@@ -29,7 +29,7 @@ enum Repr {
     /// A native Rust function.
     Native(NativeFunc),
     /// A function for a node.
-    Node(NodeFunc),
+    Node(NodeId),
     /// A user-defined closure.
     Closure(Closure),
     /// A nested function with pre-applied arguments.
@@ -156,13 +156,13 @@ impl Func {
 
     /// Create a selector for this function's node type.
     pub fn select(&self, fields: Option<Dict>) -> StrResult<Selector> {
-        match &**self.0 {
-            Repr::Node(node) => {
-                if node.id == item!(text_id) {
+        match **self.0 {
+            Repr::Node(id) => {
+                if id == item!(text_id) {
                     Err("to select text, please use a string or regex instead")?;
                 }
 
-                Ok(Selector::Node(node.id, fields))
+                Ok(Selector::Node(id, fields))
             }
             _ => Err("this function is not selectable")?,
         }
@@ -172,8 +172,8 @@ impl Func {
 impl Debug for Func {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         match self.name() {
-            Some(name) => write!(f, "<function {name}>"),
-            None => f.write_str("<function>"),
+            Some(name) => write!(f, "{name}"),
+            None => f.write_str("(..) => .."),
         }
     }
 }
@@ -190,6 +190,16 @@ impl From<Repr> for Func {
     }
 }
 
+impl From<NodeId> for Func {
+    fn from(id: NodeId) -> Self {
+        Repr::Node(id).into()
+    }
+}
+
+cast_to_value! {
+    v: NodeId => Value::Func(v.into())
+}
+
 /// A native Rust function.
 pub struct NativeFunc {
     /// The function's implementation.
@@ -223,36 +233,6 @@ where
     }
 }
 
-/// A function defined by a native Rust node.
-pub struct NodeFunc {
-    /// The node's id.
-    pub id: NodeId,
-    /// The node's constructor.
-    pub construct: fn(&Vm, &mut Args) -> SourceResult<Content>,
-    /// The node's set rule.
-    pub set: fn(&mut Args) -> SourceResult<StyleMap>,
-    /// Details about the function.
-    pub info: Lazy<FuncInfo>,
-}
-
-impl Hash for NodeFunc {
-    fn hash<H: Hasher>(&self, state: &mut H) {
-        self.id.hash(state);
-        (self.construct as usize).hash(state);
-        (self.set as usize).hash(state);
-    }
-}
-
-impl From<NodeFunc> for Func {
-    fn from(node: NodeFunc) -> Self {
-        Repr::Node(node).into()
-    }
-}
-
-cast_to_value! {
-    v: NodeFunc => Value::Func(v.into())
-}
-
 /// Details about a function.
 #[derive(Debug, Clone)]
 pub struct FuncInfo {
diff --git a/src/eval/methods.rs b/src/eval/methods.rs
index dcb1ca31..197a2f65 100644
--- a/src/eval/methods.rs
+++ b/src/eval/methods.rs
@@ -69,6 +69,13 @@ pub fn call(
             _ => return missing(),
         },
 
+        Value::Content(content) => match method {
+            "func" => Value::Func(content.id().into()),
+            "has" => Value::Bool(content.has(&args.expect::<EcoString>("field")?)),
+            "at" => content.at(&args.expect::<EcoString>("field")?).at(span)?.clone(),
+            _ => return missing(),
+        },
+
         Value::Array(array) => match method {
             "len" => Value::Int(array.len()),
             "first" => array.first().at(span)?.clone(),
@@ -96,6 +103,7 @@ pub fn call(
             "all" => Value::Bool(array.all(vm, args.expect("function")?)?),
             "flatten" => Value::Array(array.flatten()),
             "rev" => Value::Array(array.rev()),
+            "split" => Value::Array(array.split(args.expect("separator")?)),
             "join" => {
                 let sep = args.eat()?;
                 let last = args.named("last")?;
@@ -107,7 +115,7 @@ pub fn call(
 
         Value::Dict(dict) => match method {
             "len" => Value::Int(dict.len()),
-            "at" => dict.at(&args.expect::<Str>("key")?).cloned().at(span)?,
+            "at" => dict.at(&args.expect::<Str>("key")?).at(span)?.clone(),
             "keys" => Value::Array(dict.keys()),
             "values" => Value::Array(dict.values()),
             "pairs" => Value::Array(dict.pairs()),
@@ -237,6 +245,7 @@ pub fn methods_on(type_name: &str) -> &[(&'static str, bool)] {
             ("starts-with", true),
             ("trim", true),
         ],
+        "content" => &[("func", false), ("has", true), ("at", true)],
         "array" => &[
             ("all", true),
             ("any", true),
@@ -248,6 +257,7 @@ pub fn methods_on(type_name: &str) -> &[(&'static str, bool)] {
             ("flatten", false),
             ("fold", true),
             ("insert", true),
+            ("split", true),
             ("join", true),
             ("last", false),
             ("len", false),
diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index fcfda263..145f961a 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -47,6 +47,7 @@ use unicode_segmentation::UnicodeSegmentation;
 use crate::diag::{
     bail, error, At, SourceError, SourceResult, StrResult, Trace, Tracepoint,
 };
+use crate::model::Unlabellable;
 use crate::model::{Content, Label, Recipe, Selector, StyleMap, Transform};
 use crate::syntax::ast::AstNode;
 use crate::syntax::{
@@ -357,12 +358,12 @@ fn eval_markup(
                 }
 
                 let tail = eval_markup(vm, exprs)?;
-                seq.push(tail.apply_recipe(vm.world, recipe)?)
+                seq.push(tail.styled_with_recipe(vm.world, recipe)?)
             }
             expr => match expr.eval(vm)? {
                 Value::Label(label) => {
                     if let Some(node) =
-                        seq.iter_mut().rev().find(|node| node.labellable())
+                        seq.iter_mut().rev().find(|node| !node.can::<dyn Unlabellable>())
                     {
                         *node = mem::take(node).labelled(label);
                     }
@@ -786,7 +787,7 @@ fn eval_code(
                 }
 
                 let tail = eval_code(vm, exprs)?.display();
-                Value::Content(tail.apply_recipe(vm.world, recipe)?)
+                Value::Content(tail.styled_with_recipe(vm.world, recipe)?)
             }
             _ => expr.eval(vm)?,
         };
@@ -979,6 +980,10 @@ impl Eval for ast::FuncCall {
 
     fn eval(&self, vm: &mut Vm) -> SourceResult<Self::Output> {
         let span = self.span();
+        if vm.depth >= MAX_CALL_DEPTH {
+            bail!(span, "maximum function call depth exceeded");
+        }
+
         let callee = self.callee();
         let in_math = in_math(&callee);
         let callee_span = callee.span();
@@ -1042,11 +1047,6 @@ impl Eval for ast::FuncCall {
             ));
         }
 
-        // Finally, just a normal function call!
-        if vm.depth >= MAX_CALL_DEPTH {
-            bail!(span, "maximum function call depth exceeded");
-        }
-
         let callee = callee.cast::<Func>().at(callee_span)?;
         let point = || Tracepoint::Call(callee.name().map(Into::into));
         callee.call(vm, args).trace(vm.world, point, span)
diff --git a/src/eval/ops.rs b/src/eval/ops.rs
index 52b9b06a..5efb68c3 100644
--- a/src/eval/ops.rs
+++ b/src/eval/ops.rs
@@ -340,6 +340,7 @@ pub fn equal(lhs: &Value, rhs: &Value) -> bool {
         (Symbol(a), Symbol(b)) => a == b,
         (Str(a), Str(b)) => a == b,
         (Label(a), Label(b)) => a == b,
+        (Content(a), Content(b)) => a == b,
         (Array(a), Array(b)) => a == b,
         (Dict(a), Dict(b)) => a == b,
         (Func(a), Func(b)) => a == b,
diff --git a/src/eval/value.rs b/src/eval/value.rs
index 9b9bc314..61af36f5 100644
--- a/src/eval/value.rs
+++ b/src/eval/value.rs
@@ -120,10 +120,7 @@ impl Value {
         match self {
             Self::Symbol(symbol) => symbol.clone().modified(&field).map(Self::Symbol),
             Self::Dict(dict) => dict.at(&field).cloned(),
-            Self::Content(content) => content
-                .field(&field)
-                .cloned()
-                .ok_or_else(|| eco_format!("unknown field `{field}`")),
+            Self::Content(content) => content.at(&field).cloned(),
             Self::Module(module) => module.get(&field).cloned(),
             v => Err(eco_format!("cannot access fields on type {}", v.type_name())),
         }
@@ -190,7 +187,7 @@ impl Debug for Value {
             Self::Symbol(v) => Debug::fmt(v, f),
             Self::Str(v) => Debug::fmt(v, f),
             Self::Label(v) => Debug::fmt(v, f),
-            Self::Content(_) => f.pad("[...]"),
+            Self::Content(v) => Debug::fmt(v, f),
             Self::Array(v) => Debug::fmt(v, f),
             Self::Dict(v) => Debug::fmt(v, f),
             Self::Func(v) => Debug::fmt(v, f),
diff --git a/src/ide/tooltip.rs b/src/ide/tooltip.rs
index ac0cb60b..4f281050 100644
--- a/src/ide/tooltip.rs
+++ b/src/ide/tooltip.rs
@@ -1,11 +1,15 @@
+use std::fmt::Write;
+
+use ecow::EcoString;
+
 use if_chain::if_chain;
-use unicode_segmentation::UnicodeSegmentation;
 
 use super::{analyze_expr, plain_docs_sentence, summarize_font_family};
 use crate::eval::{CastInfo, Tracer, Value};
 use crate::geom::{round_2, Length, Numeric};
 use crate::syntax::ast;
 use crate::syntax::{LinkedNode, Source, SyntaxKind};
+use crate::util::pretty_comma_list;
 use crate::World;
 
 /// Describe the item under the cursor.
@@ -60,31 +64,27 @@ fn expr_tooltip(world: &(dyn World + 'static), leaf: &LinkedNode) -> Option<Tool
         return None;
     }
 
-    let mut tooltip = String::new();
-    let mut iter = values.into_iter().enumerate();
-    for (i, value) in (&mut iter).take(Tracer::MAX - 1) {
-        if i > 0 && !tooltip.is_empty() {
-            tooltip.push_str(", ");
-        }
-        let repr = value.repr();
-        let repr = repr.as_str();
-        let len = repr.len();
-        if len <= 40 {
-            tooltip.push_str(repr);
-        } else {
-            let mut graphemes = repr.graphemes(true);
-            let r = graphemes.next_back().map_or(0, str::len);
-            let l = graphemes.take(40).map(str::len).sum();
-            tooltip.push_str(&repr[..l]);
-            tooltip.push_str("...");
-            tooltip.push_str(&repr[len - r..]);
+    let mut last = None;
+    let mut pieces: Vec<EcoString> = vec![];
+    let mut iter = values.iter();
+    for value in (&mut iter).take(Tracer::MAX - 1) {
+        if let Some((prev, count)) = &mut last {
+            if *prev == value {
+                *count += 1;
+                continue;
+            } else if *count > 1 {
+                write!(pieces.last_mut().unwrap(), " (x{count})").unwrap();
+            }
         }
+        pieces.push(value.repr().into());
+        last = Some((value, 1));
     }
 
     if iter.next().is_some() {
-        tooltip.push_str(", ...");
+        pieces.push("...".into());
     }
 
+    let tooltip = pretty_comma_list(&pieces, false);
     (!tooltip.is_empty()).then(|| Tooltip::Code(tooltip))
 }
 
diff --git a/src/model/content.rs b/src/model/content.rs
index d845ce1e..b895553c 100644
--- a/src/model/content.rs
+++ b/src/model/content.rs
@@ -2,22 +2,24 @@ use std::any::TypeId;
 use std::fmt::{self, Debug, Formatter, Write};
 use std::hash::{Hash, Hasher};
 use std::iter::{self, Sum};
-use std::ops::{Add, AddAssign};
+use std::ops::{Add, AddAssign, Deref};
 
 use comemo::Tracked;
-use ecow::{EcoString, EcoVec};
+use ecow::{eco_format, EcoString, EcoVec};
+use once_cell::sync::Lazy;
 
 use super::{node, Guard, Recipe, Style, StyleMap};
 use crate::diag::{SourceResult, StrResult};
-use crate::eval::{cast_from_value, Args, Cast, NodeFunc, Value, Vm};
+use crate::eval::{cast_from_value, Args, FuncInfo, Str, Value, Vm};
 use crate::syntax::Span;
+use crate::util::pretty_array;
 use crate::World;
 
 /// Composable representation of styled content.
 #[derive(Clone, Hash)]
 pub struct Content {
     id: NodeId,
-    span: Option<Span>,
+    span: Span,
     fields: EcoVec<(EcoString, Value)>,
     modifiers: EcoVec<Modifier>,
 }
@@ -33,7 +35,7 @@ impl Content {
     pub fn new<T: Node>() -> Self {
         Self {
             id: T::id(),
-            span: None,
+            span: Span::detached(),
             fields: EcoVec::new(),
             modifiers: EcoVec::new(),
         }
@@ -52,82 +54,67 @@ impl Content {
         }
     }
 
-    /// Attach a span to the content.
-    pub fn spanned(mut self, span: Span) -> Self {
-        if let Some(styled) = self.to::<StyledNode>() {
-            self = StyledNode::new(styled.map(), styled.body().spanned(span)).pack();
-        }
-        self.span = Some(span);
-        self
-    }
-
-    /// Attach a label to the content.
-    pub fn labelled(self, label: Label) -> Self {
-        self.with_field("label", label)
+    /// The id of the contained node.
+    pub fn id(&self) -> NodeId {
+        self.id
     }
 
-    /// Style this content with a style entry.
-    pub fn styled(self, style: impl Into<Style>) -> Self {
-        self.styled_with_map(style.into().into())
+    /// Whether the contained node is of type `T`.
+    pub fn is<T>(&self) -> bool
+    where
+        T: Node + 'static,
+    {
+        self.id == NodeId::of::<T>()
     }
 
-    /// Style this content with a full style map.
-    pub fn styled_with_map(self, styles: StyleMap) -> Self {
-        if styles.is_empty() {
-            self
-        } else if let Some(styled) = self.to::<StyledNode>() {
-            let mut map = styled.map();
-            map.apply(styles);
-            StyledNode::new(map, styled.body()).pack()
-        } else {
-            StyledNode::new(styles, self).pack()
-        }
+    /// Cast to `T` if the contained node is of type `T`.
+    pub fn to<T>(&self) -> Option<&T>
+    where
+        T: Node + 'static,
+    {
+        self.is::<T>().then(|| unsafe { std::mem::transmute(self) })
     }
 
-    /// Style this content with a recipe, eagerly applying it if possible.
-    pub fn apply_recipe(
-        self,
-        world: Tracked<dyn World>,
-        recipe: Recipe,
-    ) -> SourceResult<Self> {
-        if recipe.selector.is_none() {
-            recipe.apply(world, self)
-        } else {
-            Ok(self.styled(Style::Recipe(recipe)))
-        }
+    /// Whether this content has the given capability.
+    pub fn can<C>(&self) -> bool
+    where
+        C: ?Sized + 'static,
+    {
+        (self.id.0.vtable)(TypeId::of::<C>()).is_some()
     }
 
-    /// Repeat this content `n` times.
-    pub fn repeat(&self, n: i64) -> StrResult<Self> {
-        let count = usize::try_from(n)
-            .map_err(|_| format!("cannot repeat this content {} times", n))?;
-
-        Ok(Self::sequence(vec![self.clone(); count]))
+    /// Cast to a trait object if this content has the given capability.
+    pub fn with<C>(&self) -> Option<&C>
+    where
+        C: ?Sized + 'static,
+    {
+        let vtable = (self.id.0.vtable)(TypeId::of::<C>())?;
+        let data = self as *const Self as *const ();
+        Some(unsafe { &*crate::util::fat::from_raw_parts(data, vtable) })
     }
-}
 
-impl Content {
-    /// The id of the contained node.
-    pub fn id(&self) -> NodeId {
-        self.id
+    /// The node's span.
+    pub fn span(&self) -> Span {
+        self.span
     }
 
-    /// The node's human-readable name.
-    pub fn name(&self) -> &'static str {
-        self.id.name()
+    /// Attach a span to the content.
+    pub fn spanned(mut self, span: Span) -> Self {
+        self.span = span;
+        self
     }
 
-    /// The node's span.
-    pub fn span(&self) -> Option<Span> {
-        self.span
+    /// Access a field on the content.
+    pub fn field(&self, name: &str) -> Option<&Value> {
+        self.fields
+            .iter()
+            .find(|(field, _)| field == name)
+            .map(|(_, value)| value)
     }
 
-    /// The content's label.
-    pub fn label(&self) -> Option<&Label> {
-        match self.field("label")? {
-            Value::Label(label) => Some(label),
-            _ => None,
-        }
+    /// List all fields on the content.
+    pub fn fields(&self) -> &[(EcoString, Value)] {
+        &self.fields
     }
 
     /// Attach a field to the content.
@@ -150,88 +137,88 @@ impl Content {
         }
     }
 
-    /// Access a field on the content.
-    pub fn field(&self, name: &str) -> Option<&Value> {
-        static NONE: Value = Value::None;
-        self.fields
-            .iter()
-            .find(|(field, _)| field == name)
-            .map(|(_, value)| value)
-            .or_else(|| (name == "label").then(|| &NONE))
+    /// Whether the content has the specified field.
+    pub fn has(&self, field: &str) -> bool {
+        self.field(field).is_some()
+    }
+
+    /// Borrow the value of the given field.
+    pub fn at(&self, field: &str) -> StrResult<&Value> {
+        self.field(field).ok_or_else(|| missing_field(field))
     }
 
-    #[track_caller]
-    pub fn cast_required_field<T: Cast>(&self, name: &str) -> T {
-        match self.field(name) {
-            Some(value) => value.clone().cast().unwrap(),
-            None => field_is_missing(name),
+    /// The content's label.
+    pub fn label(&self) -> Option<&Label> {
+        match self.field("label")? {
+            Value::Label(label) => Some(label),
+            _ => None,
         }
     }
 
-    /// List all fields on the content.
-    pub fn fields(&self) -> &[(EcoString, Value)] {
-        &self.fields
+    /// Attach a label to the content.
+    pub fn labelled(self, label: Label) -> Self {
+        self.with_field("label", label)
     }
 
-    /// Whether the contained node is of type `T`.
-    pub fn is<T>(&self) -> bool
-    where
-        T: Node + 'static,
-    {
-        self.id == NodeId::of::<T>()
+    /// Style this content with a style entry.
+    pub fn styled(self, style: impl Into<Style>) -> Self {
+        self.styled_with_map(style.into().into())
     }
 
-    /// Cast to `T` if the contained node is of type `T`.
-    pub fn to<T>(&self) -> Option<&T>
-    where
-        T: Node + 'static,
-    {
-        self.is::<T>().then(|| unsafe { std::mem::transmute(self) })
+    /// Style this content with a full style map.
+    pub fn styled_with_map(self, styles: StyleMap) -> Self {
+        if styles.is_empty() {
+            self
+        } else if let Some(styled) = self.to::<StyledNode>() {
+            let mut map = styled.styles();
+            map.apply(styles);
+            StyledNode::new(map, styled.body()).pack()
+        } else {
+            StyledNode::new(styles, self).pack()
+        }
     }
 
-    /// Whether this content has the given capability.
-    pub fn has<C>(&self) -> bool
-    where
-        C: ?Sized + 'static,
-    {
-        (self.id.0.vtable)(TypeId::of::<C>()).is_some()
+    /// Style this content with a recipe, eagerly applying it if possible.
+    pub fn styled_with_recipe(
+        self,
+        world: Tracked<dyn World>,
+        recipe: Recipe,
+    ) -> SourceResult<Self> {
+        if recipe.selector.is_none() {
+            recipe.apply(world, self)
+        } else {
+            Ok(self.styled(Style::Recipe(recipe)))
+        }
     }
 
-    /// Cast to a trait object if this content has the given capability.
-    pub fn with<C>(&self) -> Option<&C>
-    where
-        C: ?Sized + 'static,
-    {
-        let vtable = (self.id.0.vtable)(TypeId::of::<C>())?;
-        let data = self as *const Self as *const ();
-        Some(unsafe { &*crate::util::fat::from_raw_parts(data, vtable) })
+    /// Repeat this content `n` times.
+    pub fn repeat(&self, n: i64) -> StrResult<Self> {
+        let count = usize::try_from(n)
+            .map_err(|_| format!("cannot repeat this content {} times", n))?;
+
+        Ok(Self::sequence(vec![self.clone(); count]))
     }
+}
 
+#[doc(hidden)]
+impl Content {
     /// Disable a show rule recipe.
-    #[doc(hidden)]
     pub fn guarded(mut self, id: Guard) -> Self {
         self.modifiers.push(Modifier::Guard(id));
         self
     }
 
     /// Mark this content as prepared.
-    #[doc(hidden)]
     pub fn prepared(mut self) -> Self {
         self.modifiers.push(Modifier::Prepared);
         self
     }
 
     /// Whether this node was prepared.
-    #[doc(hidden)]
     pub fn is_prepared(&self) -> bool {
         self.modifiers.contains(&Modifier::Prepared)
     }
 
-    /// Whether a label can be attached to the content.
-    pub(crate) fn labellable(&self) -> bool {
-        !self.has::<dyn Unlabellable>()
-    }
-
     /// Whether no show rule was executed for this node so far.
     pub(super) fn is_pristine(&self) -> bool {
         !self
@@ -257,32 +244,24 @@ impl Content {
 
 impl Debug for Content {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        struct Pad<'a>(&'a str);
-        impl Debug for Pad<'_> {
-            fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-                f.pad(self.0)
-            }
+        let name = self.id.name;
+        if let Some(text) = item!(text_str)(self) {
+            f.write_char('[')?;
+            f.write_str(&text)?;
+            f.write_char(']')?;
+            return Ok(());
+        } else if name == "space" {
+            return f.write_str("[ ]");
         }
 
-        if let Some(styled) = self.to::<StyledNode>() {
-            styled.map().fmt(f)?;
-            styled.body().fmt(f)
-        } else if let Some(seq) = self.to::<SequenceNode>() {
-            f.debug_list().entries(&seq.children()).finish()
-        } else if self.id.name() == "space" {
-            ' '.fmt(f)
-        } else if self.id.name() == "text" {
-            self.field("text").unwrap().fmt(f)
-        } else {
-            f.write_str(self.name())?;
-            if self.fields.is_empty() {
-                return Ok(());
-            }
-            f.write_char(' ')?;
-            f.debug_map()
-                .entries(self.fields.iter().map(|(name, value)| (Pad(name), value)))
-                .finish()
-        }
+        let pieces: Vec<_> = self
+            .fields
+            .iter()
+            .map(|(name, value)| eco_format!("{name}: {value:?}"))
+            .collect();
+
+        f.write_str(name)?;
+        f.write_str(&pretty_array(&pieces, false))
     }
 }
 
@@ -292,6 +271,17 @@ impl Default for Content {
     }
 }
 
+impl PartialEq for Content {
+    fn eq(&self, other: &Self) -> bool {
+        self.id == other.id
+            && self.fields.len() == other.fields.len()
+            && self
+                .fields
+                .iter()
+                .all(|(name, value)| other.field(name) == Some(value))
+    }
+}
+
 impl Add for Content {
     type Output = Self;
 
@@ -323,48 +313,6 @@ impl Sum for Content {
     }
 }
 
-/// A node with applied styles.
-///
-/// Display: Styled
-/// Category: special
-#[node]
-pub struct StyledNode {
-    /// The styles.
-    #[required]
-    pub map: StyleMap,
-
-    /// The styled content.
-    #[required]
-    pub body: Content,
-}
-
-cast_from_value! {
-    StyleMap: "style map",
-}
-
-/// A sequence of nodes.
-///
-/// Combines other arbitrary content. So, when you write `[Hi] + [you]` in
-/// Typst, the two text nodes are combined into a single sequence node.
-///
-/// Display: Sequence
-/// Category: special
-#[node]
-pub struct SequenceNode {
-    #[variadic]
-    pub children: Vec<Content>,
-}
-
-/// A label for a node.
-#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
-pub struct Label(pub EcoString);
-
-impl Debug for Label {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "<{}>", self.0)
-    }
-}
-
 /// A constructable, stylable content node.
 pub trait Node: Construct + Set + Sized + 'static {
     /// The node's ID.
@@ -372,33 +320,22 @@ pub trait Node: Construct + Set + Sized + 'static {
 
     /// Pack a node into type-erased content.
     fn pack(self) -> Content;
-
-    /// The node's function.
-    fn func() -> NodeFunc;
 }
 
 /// A unique identifier for a node.
 #[derive(Copy, Clone)]
-pub struct NodeId(&'static NodeMeta);
+pub struct NodeId(pub &'static NodeMeta);
 
 impl NodeId {
+    /// Get the id of a node.
     pub fn of<T: Node>() -> Self {
         T::id()
     }
-
-    pub fn from_meta(meta: &'static NodeMeta) -> Self {
-        Self(meta)
-    }
-
-    /// The name of the identified node.
-    pub fn name(self) -> &'static str {
-        self.0.name
-    }
 }
 
 impl Debug for NodeId {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        f.pad(self.name())
+        f.pad(self.name)
     }
 }
 
@@ -416,10 +353,26 @@ impl PartialEq for NodeId {
     }
 }
 
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+impl Deref for NodeId {
+    type Target = NodeMeta;
+
+    fn deref(&self) -> &Self::Target {
+        self.0
+    }
+}
+
+/// Static node for a node.
 pub struct NodeMeta {
+    /// The node's name.
     pub name: &'static str,
+    /// The node's vtable for caspability dispatch.
     pub vtable: fn(of: TypeId) -> Option<*const ()>,
+    /// The node's constructor.
+    pub construct: fn(&Vm, &mut Args) -> SourceResult<Content>,
+    /// The node's set rule.
+    pub set: fn(&mut Args) -> SourceResult<StyleMap>,
+    /// Details about the function.
+    pub info: Lazy<FuncInfo>,
 }
 
 /// A node's constructor function.
@@ -440,8 +393,51 @@ pub trait Set {
 /// Indicates that a node cannot be labelled.
 pub trait Unlabellable {}
 
+/// A label for a node.
+#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
+pub struct Label(pub EcoString);
+
+impl Debug for Label {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "<{}>", self.0)
+    }
+}
+
+/// A sequence of nodes.
+///
+/// Combines other arbitrary content. So, when you write `[Hi] + [you]` in
+/// Typst, the two text nodes are combined into a single sequence node.
+///
+/// Display: Sequence
+/// Category: special
+#[node]
+pub struct SequenceNode {
+    #[variadic]
+    pub children: Vec<Content>,
+}
+
+/// A node with applied styles.
+///
+/// Display: Styled
+/// Category: special
+#[node]
+pub struct StyledNode {
+    /// The styles.
+    #[required]
+    pub styles: StyleMap,
+
+    /// The styled content.
+    #[required]
+    pub body: Content,
+}
+
+cast_from_value! {
+    StyleMap: "style map",
+}
+
+/// The missing key access error message.
 #[cold]
 #[track_caller]
-fn field_is_missing(name: &str) -> ! {
-    panic!("required field `{name}` is missing")
+fn missing_field(key: &str) -> EcoString {
+    eco_format!("content does not contain field {:?}", Str::from(key))
 }
diff --git a/src/model/realize.rs b/src/model/realize.rs
index 502774bb..c4c67a4f 100644
--- a/src/model/realize.rs
+++ b/src/model/realize.rs
@@ -3,11 +3,11 @@ use crate::diag::SourceResult;
 
 /// Whether the target is affected by show rules in the given style chain.
 pub fn applicable(target: &Content, styles: StyleChain) -> bool {
-    if target.has::<dyn Prepare>() && !target.is_prepared() {
+    if target.can::<dyn Prepare>() && !target.is_prepared() {
         return true;
     }
 
-    if target.has::<dyn Show>() && target.is_pristine() {
+    if target.can::<dyn Show>() && target.is_pristine() {
         return true;
     }
 
@@ -51,7 +51,7 @@ pub fn realize(
     if let Some(showable) = target.with::<dyn Show>() {
         let guard = Guard::Base(target.id());
         if realized.is_none() && !target.is_guarded(guard) {
-            realized = Some(showable.show(vt, target, styles)?);
+            realized = Some(showable.show(vt, styles)?);
         }
     }
 
@@ -135,23 +135,13 @@ fn try_apply(
 /// Preparations before execution of any show rule.
 pub trait Prepare {
     /// Prepare the node for show rule application.
-    fn prepare(
-        &self,
-        vt: &mut Vt,
-        this: Content,
-        styles: StyleChain,
-    ) -> SourceResult<Content>;
+    fn prepare(&self, vt: &mut Vt, styles: StyleChain) -> SourceResult<Content>;
 }
 
 /// The base recipe for a node.
 pub trait Show {
     /// Execute the base recipe for this node.
-    fn show(
-        &self,
-        vt: &mut Vt,
-        this: &Content,
-        styles: StyleChain,
-    ) -> SourceResult<Content>;
+    fn show(&self, vt: &mut Vt, styles: StyleChain) -> SourceResult<Content>;
 }
 
 /// Post-process a node after it was realized.
diff --git a/src/model/styles.rs b/src/model/styles.rs
index 3239bb17..b803bc34 100644
--- a/src/model/styles.rs
+++ b/src/model/styles.rs
@@ -1,13 +1,14 @@
-use std::fmt::{self, Debug, Formatter};
+use std::fmt::{self, Debug, Formatter, Write};
 use std::iter;
 
 use comemo::Tracked;
-use ecow::EcoString;
+use ecow::{eco_format, EcoString};
 
 use super::{Content, Label, Node, NodeId};
 use crate::diag::{SourceResult, Trace, Tracepoint};
 use crate::eval::{cast_from_value, Args, Cast, Dict, Func, Regex, Value};
 use crate::syntax::Span;
+use crate::util::pretty_array;
 use crate::World;
 
 /// A map of style properties.
@@ -79,10 +80,13 @@ impl PartialEq for StyleMap {
 
 impl Debug for StyleMap {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        for entry in self.0.iter() {
-            writeln!(f, "{:?}", entry)?;
+        if let [style] = self.0.as_slice() {
+            return style.fmt(f);
         }
-        Ok(())
+
+        let pieces: Vec<_> =
+            self.0.iter().map(|value| eco_format!("{value:?}")).collect();
+        f.write_str(&pretty_array(&pieces, false))
     }
 }
 
@@ -160,7 +164,7 @@ impl Property {
 
 impl Debug for Property {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "#set {}({}: {:?})", self.node.name(), self.name, self.value)?;
+        write!(f, "set {}({}: {:?})", self.node.name, self.name, self.value)?;
         Ok(())
     }
 }
@@ -203,12 +207,10 @@ impl Recipe {
             Transform::Func(func) => {
                 let args = Args::new(self.span, [Value::Content(content.clone())]);
                 let mut result = func.call_detached(world, args);
-                if let Some(span) = content.span() {
-                    // For selector-less show rules, a tracepoint makes no sense.
-                    if self.selector.is_some() {
-                        let point = || Tracepoint::Show(content.name().into());
-                        result = result.trace(world, point, span);
-                    }
+                // For selector-less show rules, a tracepoint makes no sense.
+                if self.selector.is_some() {
+                    let point = || Tracepoint::Show(content.id().name.into());
+                    result = result.trace(world, point, content.span());
                 }
                 Ok(result?.display())
             }
@@ -219,12 +221,18 @@ impl Recipe {
 
 impl Debug for Recipe {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "#show {:?}: {:?}", self.selector, self.transform)
+        f.write_str("show")?;
+        if let Some(selector) = &self.selector {
+            f.write_char(' ')?;
+            selector.fmt(f)?;
+        }
+        f.write_str(": ")?;
+        self.transform.fmt(f)
     }
 }
 
 /// A selector in a show rule.
-#[derive(Debug, Clone, PartialEq, Hash)]
+#[derive(Clone, PartialEq, Hash)]
 pub enum Selector {
     /// Matches a specific type of node.
     ///
@@ -267,6 +275,23 @@ impl Selector {
     }
 }
 
+impl Debug for Selector {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        match self {
+            Self::Node(node, dict) => {
+                f.write_str(node.name)?;
+                if let Some(dict) = dict {
+                    f.write_str(".where")?;
+                    dict.fmt(f)?;
+                }
+                Ok(())
+            }
+            Self::Label(label) => label.fmt(f),
+            Self::Regex(regex) => regex.fmt(f),
+        }
+    }
+}
+
 cast_from_value! {
     Selector: "selector",
     text: EcoString => Self::text(&text),
@@ -276,7 +301,7 @@ cast_from_value! {
 }
 
 /// A show rule transformation that can be applied to a match.
-#[derive(Debug, Clone, Hash)]
+#[derive(Clone, Hash)]
 pub enum Transform {
     /// Replacement content.
     Content(Content),
@@ -286,6 +311,16 @@ pub enum Transform {
     Style(StyleMap),
 }
 
+impl Debug for Transform {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        match self {
+            Self::Content(content) => content.fmt(f),
+            Self::Func(func) => func.fmt(f),
+            Self::Style(styles) => styles.fmt(f),
+        }
+    }
+}
+
 cast_from_value! {
     Transform,
     content: Content => Self::Content(content),
@@ -434,9 +469,9 @@ impl<'a> StyleChain<'a> {
                     .map(|property| property.value.clone()),
             )
             .map(move |value| {
-                value.cast().unwrap_or_else(|err| {
-                    panic!("{} (for {}.{})", err, node.name(), name)
-                })
+                value
+                    .cast()
+                    .unwrap_or_else(|err| panic!("{} (for {}.{})", err, node.name, name))
             })
     }
 
diff --git a/src/util/mod.rs b/src/util/mod.rs
index 54b9fe27..a3fad8ca 100644
--- a/src/util/mod.rs
+++ b/src/util/mod.rs
@@ -6,12 +6,12 @@ mod buffer;
 
 pub use buffer::Buffer;
 
-use std::any::TypeId;
 use std::fmt::{self, Debug, Formatter};
 use std::hash::Hash;
 use std::path::{Component, Path, PathBuf};
 use std::sync::Arc;
 
+use ecow::EcoString;
 use siphasher::sip128::{Hasher128, SipHasher};
 
 /// Turn a closure into a struct implementing [`Debug`].
@@ -133,35 +133,63 @@ impl PathExt for Path {
     }
 }
 
-/// An alternative type id that prints as something readable in debug mode.
-#[derive(Copy, Clone, Eq, PartialEq, Hash)]
-pub struct ReadableTypeId {
-    id: TypeId,
-    #[cfg(debug_assertions)]
-    name: &'static str,
+/// Format something as a a comma-separated list that support horizontal
+/// formatting but falls back to vertical formatting if the pieces are too long.
+pub fn pretty_array(pieces: &[EcoString], trailing_comma: bool) -> String {
+    let list = pretty_comma_list(&pieces, trailing_comma);
+    let mut buf = String::new();
+    buf.push('(');
+    if list.contains('\n') {
+        buf.push('\n');
+        buf.push_str(&indent(&list, 2));
+        buf.push('\n');
+    } else {
+        buf.push_str(&list);
+    }
+    buf.push(')');
+    buf
 }
 
-impl ReadableTypeId {
-    /// The type id of the given type.
-    pub fn of<T: 'static>() -> Self {
-        Self {
-            id: TypeId::of::<T>(),
-            #[cfg(debug_assertions)]
-            name: std::any::type_name::<T>(),
+/// Format something as a a comma-separated list that support horizontal
+/// formatting but falls back to vertical formatting if the pieces are too long.
+pub fn pretty_comma_list(pieces: &[EcoString], trailing_comma: bool) -> String {
+    const MAX_WIDTH: usize = 50;
+
+    let mut buf = String::new();
+    let len = pieces.iter().map(|s| s.len()).sum::<usize>()
+        + 2 * pieces.len().saturating_sub(1);
+
+    if len <= MAX_WIDTH {
+        for (i, piece) in pieces.iter().enumerate() {
+            if i > 0 {
+                buf.push_str(", ");
+            }
+            buf.push_str(piece);
+        }
+        if trailing_comma {
+            buf.push(',');
+        }
+    } else {
+        for piece in pieces {
+            buf.push_str(piece.trim());
+            buf.push_str(",\n");
         }
     }
+
+    buf
 }
 
-impl Debug for ReadableTypeId {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        #[cfg(debug_assertions)]
-        if let Some(part) = self.name.split("::").last() {
-            f.pad(part)?;
+/// Indent a string by two spaces.
+pub fn indent(text: &str, amount: usize) -> String {
+    let mut buf = String::new();
+    for (i, line) in text.lines().enumerate() {
+        if i > 0 {
+            buf.push('\n');
         }
-
-        #[cfg(not(debug_assertions))]
-        f.pad("ReadableTypeId")?;
-
-        Ok(())
+        for _ in 0..amount {
+            buf.push(' ');
+        }
+        buf.push_str(line);
     }
+    buf
 }