A New World

69 files changed, 854 insertions, 1047 deletions

diff --git a/src/diag.rs b/src/diag.rs
index c4438307..e96dfb00 100644
--- a/src/diag.rs
+++ b/src/diag.rs
@@ -5,7 +5,7 @@ use std::io;
 use std::path::Path;
 
 use crate::syntax::{Span, Spanned};
-use crate::Context;
+use crate::World;
 
 /// Early-return with a [`TypError`].
 #[macro_export]
@@ -101,21 +101,21 @@ where
 /// Enrich a [`TypResult`] with a tracepoint.
 pub trait Trace<T> {
     /// Add the tracepoint to all errors that lie outside the `span`.
-    fn trace<F>(self, ctx: &Context, make_point: F, span: Span) -> Self
+    fn trace<F>(self, world: &dyn World, make_point: F, span: Span) -> Self
     where
         F: Fn() -> Tracepoint;
 }
 
 impl<T> Trace<T> for TypResult<T> {
-    fn trace<F>(self, ctx: &Context, make_point: F, span: Span) -> Self
+    fn trace<F>(self, world: &dyn World, make_point: F, span: Span) -> Self
     where
         F: Fn() -> Tracepoint,
     {
         self.map_err(|mut errors| {
-            let range = ctx.sources.range(span);
+            let range = world.source(span.source()).range(span);
             for error in errors.iter_mut() {
                 // Skip traces that surround the error.
-                let error_range = ctx.sources.range(error.span);
+                let error_range = world.source(error.span.source()).range(error.span);
                 if range.start <= error_range.start && range.end >= error_range.end {
                     continue;
                 }
diff --git a/src/eval/array.rs b/src/eval/array.rs
index 43261a22..6d558393 100644
--- a/src/eval/array.rs
+++ b/src/eval/array.rs
@@ -3,7 +3,7 @@ use std::fmt::{self, Debug, Formatter, Write};
 use std::ops::{Add, AddAssign};
 use std::sync::Arc;
 
-use super::{ops, Args, Func, Machine, Value};
+use super::{ops, Args, Func, Value, Vm};
 use crate::diag::{At, StrResult, TypResult};
 use crate::syntax::Spanned;
 use crate::util::ArcExt;
@@ -124,7 +124,7 @@ impl Array {
     }
 
     /// Return the first matching element.
-    pub fn find(&self, vm: &mut Machine, f: Spanned<Func>) -> TypResult<Option<Value>> {
+    pub fn find(&self, vm: &mut Vm, f: Spanned<Func>) -> TypResult<Option<Value>> {
         for item in self.iter() {
             let args = Args::new(f.span, [item.clone()]);
             if f.v.call(vm, args)?.cast::<bool>().at(f.span)? {
@@ -136,7 +136,7 @@ impl Array {
     }
 
     /// Return the index of the first matching element.
-    pub fn position(&self, vm: &mut Machine, f: Spanned<Func>) -> TypResult<Option<i64>> {
+    pub fn position(&self, vm: &mut Vm, f: Spanned<Func>) -> TypResult<Option<i64>> {
         for (i, item) in self.iter().enumerate() {
             let args = Args::new(f.span, [item.clone()]);
             if f.v.call(vm, args)?.cast::<bool>().at(f.span)? {
@@ -149,7 +149,7 @@ impl Array {
 
     /// Return a new array with only those elements for which the function
     /// returns true.
-    pub fn filter(&self, vm: &mut Machine, f: Spanned<Func>) -> TypResult<Self> {
+    pub fn filter(&self, vm: &mut Vm, f: Spanned<Func>) -> TypResult<Self> {
         let mut kept = vec![];
         for item in self.iter() {
             let args = Args::new(f.span, [item.clone()]);
@@ -161,7 +161,7 @@ impl Array {
     }
 
     /// Transform each item in the array with a function.
-    pub fn map(&self, vm: &mut Machine, f: Spanned<Func>) -> TypResult<Self> {
+    pub fn map(&self, vm: &mut Vm, f: Spanned<Func>) -> TypResult<Self> {
         let enumerate = f.v.argc() == Some(2);
         Ok(self
             .iter()
@@ -178,7 +178,7 @@ impl Array {
     }
 
     /// Whether any element matches.
-    pub fn any(&self, vm: &mut Machine, f: Spanned<Func>) -> TypResult<bool> {
+    pub fn any(&self, vm: &mut Vm, f: Spanned<Func>) -> TypResult<bool> {
         for item in self.iter() {
             let args = Args::new(f.span, [item.clone()]);
             if f.v.call(vm, args)?.cast::<bool>().at(f.span)? {
@@ -190,7 +190,7 @@ impl Array {
     }
 
     /// Whether all elements match.
-    pub fn all(&self, vm: &mut Machine, f: Spanned<Func>) -> TypResult<bool> {
+    pub fn all(&self, vm: &mut Vm, f: Spanned<Func>) -> TypResult<bool> {
         for item in self.iter() {
             let args = Args::new(f.span, [item.clone()]);
             if !f.v.call(vm, args)?.cast::<bool>().at(f.span)? {
diff --git a/src/eval/capture.rs b/src/eval/capture.rs
index bbda96ad..b7570fe9 100644
--- a/src/eval/capture.rs
+++ b/src/eval/capture.rs
@@ -136,14 +136,14 @@ mod tests {
     use crate::parse::parse;
 
     #[track_caller]
-    fn test(src: &str, result: &[&str]) {
+    fn test(text: &str, result: &[&str]) {
         let mut scopes = Scopes::new(None);
         scopes.top.define("x", 0);
         scopes.top.define("y", 0);
         scopes.top.define("z", 0);
 
         let mut visitor = CapturesVisitor::new(&scopes);
-        let root = parse(src);
+        let root = parse(text);
         visitor.visit(&root);
 
         let captures = visitor.finish();
diff --git a/src/eval/dict.rs b/src/eval/dict.rs
index 837933b1..3ba72c8a 100644
--- a/src/eval/dict.rs
+++ b/src/eval/dict.rs
@@ -3,7 +3,7 @@ use std::fmt::{self, Debug, Formatter, Write};
 use std::ops::{Add, AddAssign};
 use std::sync::Arc;
 
-use super::{Args, Array, Func, Machine, Str, Value};
+use super::{Args, Array, Func, Str, Value, Vm};
 use crate::diag::{StrResult, TypResult};
 use crate::parse::is_ident;
 use crate::syntax::Spanned;
@@ -101,7 +101,7 @@ impl Dict {
     }
 
     /// Transform each pair in the array with a function.
-    pub fn map(&self, vm: &mut Machine, f: Spanned<Func>) -> TypResult<Array> {
+    pub fn map(&self, vm: &mut Vm, f: Spanned<Func>) -> TypResult<Array> {
         Ok(self
             .iter()
             .map(|(key, value)| {
diff --git a/src/eval/func.rs b/src/eval/func.rs
index bd312d66..d6b5252a 100644
--- a/src/eval/func.rs
+++ b/src/eval/func.rs
@@ -2,13 +2,13 @@ use std::fmt::{self, Debug, Formatter};
 use std::hash::{Hash, Hasher};
 use std::sync::Arc;
 
-use super::{Args, Eval, Flow, Machine, Scope, Scopes, Value};
+use super::{Args, Eval, Flow, Scope, Scopes, Value, Vm};
 use crate::diag::{StrResult, TypResult};
 use crate::model::{Content, NodeId, StyleMap};
 use crate::source::SourceId;
 use crate::syntax::ast::Expr;
 use crate::util::EcoString;
-use crate::Context;
+use crate::World;
 
 /// An evaluatable function.
 #[derive(Clone, Hash)]
@@ -29,7 +29,7 @@ impl Func {
     /// Create a new function from a native rust function.
     pub fn from_fn(
         name: &'static str,
-        func: fn(&mut Machine, &mut Args) -> TypResult<Value>,
+        func: fn(&mut Vm, &mut Args) -> TypResult<Value>,
     ) -> Self {
         Self(Arc::new(Repr::Native(Native {
             name,
@@ -86,7 +86,7 @@ impl Func {
     }
 
     /// Call the function with the given arguments.
-    pub fn call(&self, vm: &mut Machine, mut args: Args) -> TypResult<Value> {
+    pub fn call(&self, vm: &mut Vm, mut args: Args) -> TypResult<Value> {
         let value = match self.0.as_ref() {
             Repr::Native(native) => (native.func)(vm, &mut args)?,
             Repr::Closure(closure) => closure.call(vm, &mut args)?,
@@ -100,8 +100,8 @@ impl Func {
     }
 
     /// Call the function without an existing virtual machine.
-    pub fn call_detached(&self, ctx: &mut Context, args: Args) -> TypResult<Value> {
-        let mut vm = Machine::new(ctx, vec![], Scopes::new(None));
+    pub fn call_detached(&self, world: &dyn World, args: Args) -> TypResult<Value> {
+        let mut vm = Vm::new(world, vec![], Scopes::new(None));
         self.call(&mut vm, args)
     }
 
@@ -144,7 +144,7 @@ struct Native {
     /// The name of the function.
     pub name: &'static str,
     /// The function pointer.
-    pub func: fn(&mut Machine, &mut Args) -> TypResult<Value>,
+    pub func: fn(&mut Vm, &mut Args) -> TypResult<Value>,
     /// The set rule.
     pub set: Option<fn(&mut Args) -> TypResult<StyleMap>>,
     /// The id of the node to customize with this function's show rule.
@@ -169,7 +169,7 @@ pub trait Node: 'static {
     ///
     /// This is passed only the arguments that remain after execution of the
     /// node's set rule.
-    fn construct(vm: &mut Machine, args: &mut Args) -> TypResult<Content>;
+    fn construct(vm: &mut Vm, args: &mut Args) -> TypResult<Content>;
 
     /// Parse relevant arguments into style properties for this node.
     ///
@@ -198,7 +198,7 @@ pub struct Closure {
 
 impl Closure {
     /// Call the function in the context with the arguments.
-    pub fn call(&self, vm: &mut Machine, args: &mut Args) -> TypResult<Value> {
+    pub fn call(&self, vm: &mut Vm, args: &mut Args) -> TypResult<Value> {
         // Don't leak the scopes from the call site. Instead, we use the scope
         // of captured variables we collected earlier.
         let mut scopes = Scopes::new(None);
@@ -228,9 +228,8 @@ impl Closure {
         };
 
         // Evaluate the body.
-        let mut sub = Machine::new(vm.ctx, route, scopes);
+        let mut sub = Vm::new(vm.world, route, scopes);
         let result = self.body.eval(&mut sub);
-        vm.deps.extend(sub.deps);
 
         // Handle control flow.
         match sub.flow {
diff --git a/src/eval/methods.rs b/src/eval/methods.rs
index 5072e688..08d7dd3f 100644
--- a/src/eval/methods.rs
+++ b/src/eval/methods.rs
@@ -1,13 +1,13 @@
 //! Methods on values.
 
-use super::{Args, Machine, Value};
+use super::{Args, Value, Vm};
 use crate::diag::{At, TypResult};
 use crate::syntax::Span;
 use crate::util::EcoString;
 
 /// Call a method on a value.
 pub fn call(
-    vm: &mut Machine,
+    vm: &mut Vm,
     value: Value,
     method: &str,
     mut args: Args,
diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index 2ab94785..bae9ac94 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -13,11 +13,11 @@ mod value;
 mod args;
 mod capture;
 mod func;
-mod machine;
 pub mod methods;
 pub mod ops;
 mod raw;
 mod scope;
+mod vm;
 
 pub use self::str::*;
 pub use args::*;
@@ -26,25 +26,25 @@ pub use capture::*;
 pub use cast::*;
 pub use dict::*;
 pub use func::*;
-pub use machine::*;
 pub use raw::*;
 pub use scope::*;
 pub use typst_macros::node;
 pub use value::*;
+pub use vm::*;
 
 use std::collections::BTreeMap;
 
 use unicode_segmentation::UnicodeSegmentation;
 
-use crate::diag::{At, StrResult, Trace, Tracepoint, TypResult};
+use crate::diag::{failed_to_load, At, StrResult, Trace, Tracepoint, TypResult};
 use crate::geom::{Angle, Em, Fraction, Length, Ratio};
 use crate::library;
 use crate::model::{Content, Pattern, Recipe, StyleEntry, StyleMap};
-use crate::source::{SourceId, SourceStore};
+use crate::source::SourceId;
 use crate::syntax::ast::*;
 use crate::syntax::{Span, Spanned};
 use crate::util::EcoString;
-use crate::Context;
+use crate::World;
 
 /// Evaluate a source file and return the resulting module.
 ///
@@ -52,29 +52,24 @@ use crate::Context;
 /// layoutable contents or diagnostics in the form of a vector of error
 /// messages with file and span information.
 pub fn evaluate(
-    ctx: &mut Context,
+    world: &dyn World,
     id: SourceId,
     mut route: Vec<SourceId>,
 ) -> TypResult<Module> {
     // Prevent cyclic evaluation.
     if route.contains(&id) {
-        let path = ctx.sources.get(id).path().display();
+        let path = world.source(id).path().display();
         panic!("Tried to cyclicly evaluate {}", path);
     }
 
     route.push(id);
 
-    // Parse the file.
-    let source = ctx.sources.get(id);
-    let ast = source.ast()?;
-    let rev = source.rev();
-
     // Evaluate the module.
-    let std = ctx.config.std.clone();
-    let scopes = Scopes::new(Some(&std));
-    let mut vm = Machine::new(ctx, route, scopes);
+    let ast = world.source(id).ast()?;
+    let std = &world.config().std;
+    let scopes = Scopes::new(Some(std));
+    let mut vm = Vm::new(world, route, scopes);
     let result = ast.eval(&mut vm);
-    vm.deps.push((id, rev));
 
     // Handle control flow.
     if let Some(flow) = vm.flow {
@@ -82,11 +77,7 @@ pub fn evaluate(
     }
 
     // Assemble the module.
-    Ok(Module {
-        scope: vm.scopes.top,
-        content: result?,
-        deps: vm.deps,
-    })
+    Ok(Module { scope: vm.scopes.top, content: result? })
 }
 
 /// An evaluated module, ready for importing or layouting.
@@ -96,15 +87,6 @@ pub struct Module {
     pub scope: Scope,
     /// The module's layoutable contents.
     pub content: Content,
-    /// The source file revisions this module depends on.
-    pub deps: Vec<(SourceId, usize)>,
-}
-
-impl Module {
-    /// Whether the module is still valid for the given sources.
-    pub fn valid(&self, sources: &SourceStore) -> bool {
-        self.deps.iter().all(|&(id, rev)| rev == sources.get(id).rev())
-    }
 }
 
 /// Evaluate an expression.
@@ -113,20 +95,20 @@ pub trait Eval {
     type Output;
 
     /// Evaluate the expression to the output value.
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output>;
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output>;
 }
 
 impl Eval for Markup {
     type Output = Content;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         eval_markup(vm, &mut self.nodes())
     }
 }
 
 /// Evaluate a stream of markup nodes.
 fn eval_markup(
-    vm: &mut Machine,
+    vm: &mut Vm,
     nodes: &mut impl Iterator<Item = MarkupNode>,
 ) -> TypResult<Content> {
     let flow = vm.flow.take();
@@ -175,7 +157,7 @@ fn eval_markup(
 impl Eval for MarkupNode {
     type Output = Content;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         Ok(match self {
             Self::Space => Content::Space,
             Self::Parbreak => Content::Parbreak,
@@ -199,7 +181,7 @@ impl Eval for MarkupNode {
 impl Eval for StrongNode {
     type Output = Content;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         Ok(Content::show(library::text::StrongNode(
             self.body().eval(vm)?,
         )))
@@ -209,7 +191,7 @@ impl Eval for StrongNode {
 impl Eval for EmphNode {
     type Output = Content;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         Ok(Content::show(library::text::EmphNode(
             self.body().eval(vm)?,
         )))
@@ -219,7 +201,7 @@ impl Eval for EmphNode {
 impl Eval for RawNode {
     type Output = Content;
 
-    fn eval(&self, _: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, _: &mut Vm) -> TypResult<Self::Output> {
         let content = Content::show(library::text::RawNode {
             text: self.text.clone(),
             block: self.block,
@@ -234,7 +216,7 @@ impl Eval for RawNode {
 impl Eval for Spanned<MathNode> {
     type Output = Content;
 
-    fn eval(&self, _: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, _: &mut Vm) -> TypResult<Self::Output> {
         Ok(Content::show(library::math::MathNode {
             formula: self.clone().map(|math| math.formula),
             display: self.v.display,
@@ -245,7 +227,7 @@ impl Eval for Spanned<MathNode> {
 impl Eval for HeadingNode {
     type Output = Content;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         Ok(Content::show(library::structure::HeadingNode {
             body: self.body().eval(vm)?,
             level: self.level(),
@@ -256,7 +238,7 @@ impl Eval for HeadingNode {
 impl Eval for ListNode {
     type Output = Content;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         Ok(Content::Item(library::structure::ListItem {
             kind: library::structure::UNORDERED,
             number: None,
@@ -268,7 +250,7 @@ impl Eval for ListNode {
 impl Eval for EnumNode {
     type Output = Content;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         Ok(Content::Item(library::structure::ListItem {
             kind: library::structure::ORDERED,
             number: self.number(),
@@ -280,7 +262,7 @@ impl Eval for EnumNode {
 impl Eval for Expr {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let forbidden = |name| {
             error!(
                 self.span(),
@@ -321,7 +303,7 @@ impl Eval for Expr {
 impl Eval for Lit {
     type Output = Value;
 
-    fn eval(&self, _: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, _: &mut Vm) -> TypResult<Self::Output> {
         Ok(match self.kind() {
             LitKind::None => Value::None,
             LitKind::Auto => Value::Auto,
@@ -343,7 +325,7 @@ impl Eval for Lit {
 impl Eval for Ident {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         vm.scopes.get(self).cloned().at(self.span())
     }
 }
@@ -351,7 +333,7 @@ impl Eval for Ident {
 impl Eval for CodeBlock {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         vm.scopes.enter();
         let output = eval_code(vm, &mut self.exprs())?;
         vm.scopes.exit();
@@ -360,10 +342,7 @@ impl Eval for CodeBlock {
 }
 
 /// Evaluate a stream of expressions.
-fn eval_code(
-    vm: &mut Machine,
-    exprs: &mut impl Iterator<Item = Expr>,
-) -> TypResult<Value> {
+fn eval_code(vm: &mut Vm, exprs: &mut impl Iterator<Item = Expr>) -> TypResult<Value> {
     let flow = vm.flow.take();
     let mut output = Value::None;
 
@@ -415,7 +394,7 @@ fn eval_code(
 impl Eval for ContentBlock {
     type Output = Content;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         vm.scopes.enter();
         let content = self.body().eval(vm)?;
         vm.scopes.exit();
@@ -426,7 +405,7 @@ impl Eval for ContentBlock {
 impl Eval for GroupExpr {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         self.expr().eval(vm)
     }
 }
@@ -434,7 +413,7 @@ impl Eval for GroupExpr {
 impl Eval for ArrayExpr {
     type Output = Array;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let items = self.items();
 
         let mut vec = Vec::with_capacity(items.size_hint().0);
@@ -456,7 +435,7 @@ impl Eval for ArrayExpr {
 impl Eval for DictExpr {
     type Output = Dict;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let mut map = BTreeMap::new();
 
         for item in self.items() {
@@ -486,7 +465,7 @@ impl Eval for DictExpr {
 impl Eval for UnaryExpr {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let value = self.expr().eval(vm)?;
         let result = match self.op() {
             UnOp::Pos => ops::pos(value),
@@ -500,7 +479,7 @@ impl Eval for UnaryExpr {
 impl Eval for BinaryExpr {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         match self.op() {
             BinOp::Add => self.apply(vm, ops::add),
             BinOp::Sub => self.apply(vm, ops::sub),
@@ -529,7 +508,7 @@ impl BinaryExpr {
     /// Apply a basic binary operation.
     fn apply(
         &self,
-        vm: &mut Machine,
+        vm: &mut Vm,
         op: fn(Value, Value) -> StrResult<Value>,
     ) -> TypResult<Value> {
         let lhs = self.lhs().eval(vm)?;
@@ -548,7 +527,7 @@ impl BinaryExpr {
     /// Apply an assignment operation.
     fn assign(
         &self,
-        vm: &mut Machine,
+        vm: &mut Vm,
         op: fn(Value, Value) -> StrResult<Value>,
     ) -> TypResult<Value> {
         let rhs = self.rhs().eval(vm)?;
@@ -562,7 +541,7 @@ impl BinaryExpr {
 impl Eval for FieldAccess {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let object = self.object().eval(vm)?;
         let span = self.field().span();
         let field = self.field().take();
@@ -588,7 +567,7 @@ impl Eval for FieldAccess {
 impl Eval for FuncCall {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let callee = self.callee().eval(vm)?;
         let args = self.args().eval(vm)?;
 
@@ -597,7 +576,7 @@ impl Eval for FuncCall {
             Value::Dict(dict) => dict.get(&args.into_key()?).at(self.span())?.clone(),
             Value::Func(func) => {
                 let point = || Tracepoint::Call(func.name().map(ToString::to_string));
-                func.call(vm, args).trace(vm.ctx, point, self.span())?
+                func.call(vm, args).trace(vm.world, point, self.span())?
             }
 
             v => bail!(
@@ -612,7 +591,7 @@ impl Eval for FuncCall {
 impl Eval for MethodCall {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let span = self.span();
         let method = self.method();
         let point = || Tracepoint::Call(Some(method.to_string()));
@@ -621,12 +600,12 @@ impl Eval for MethodCall {
             let args = self.args().eval(vm)?;
             let mut value = self.receiver().access(vm)?;
             methods::call_mut(&mut value, &method, args, span)
-                .trace(vm.ctx, point, span)?;
+                .trace(vm.world, point, span)?;
             Value::None
         } else {
             let value = self.receiver().eval(vm)?;
             let args = self.args().eval(vm)?;
-            methods::call(vm, value, &method, args, span).trace(vm.ctx, point, span)?
+            methods::call(vm, value, &method, args, span).trace(vm.world, point, span)?
         })
     }
 }
@@ -634,7 +613,7 @@ impl Eval for MethodCall {
 impl Eval for CallArgs {
     type Output = Args;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let mut items = Vec::new();
 
         for arg in self.items() {
@@ -683,7 +662,7 @@ impl Eval for CallArgs {
 impl Eval for ClosureExpr {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         // The closure's name is defined by its let binding if there's one.
         let name = self.name().map(Ident::take);
 
@@ -730,7 +709,7 @@ impl Eval for ClosureExpr {
 impl Eval for LetExpr {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let value = match self.init() {
             Some(expr) => expr.eval(vm)?,
             None => Value::None,
@@ -743,7 +722,7 @@ impl Eval for LetExpr {
 impl Eval for SetExpr {
     type Output = StyleMap;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let target = self.target();
         let target = target.eval(vm)?.cast::<Func>().at(target.span())?;
         let args = self.args().eval(vm)?;
@@ -754,7 +733,7 @@ impl Eval for SetExpr {
 impl Eval for ShowExpr {
     type Output = Recipe;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         // Evaluate the target function.
         let pattern = self.pattern();
         let pattern = pattern.eval(vm)?.cast::<Pattern>().at(pattern.span())?;
@@ -791,7 +770,7 @@ impl Eval for ShowExpr {
 impl Eval for IfExpr {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let condition = self.condition();
         if condition.eval(vm)?.cast::<bool>().at(condition.span())? {
             self.if_body().eval(vm)
@@ -806,7 +785,7 @@ impl Eval for IfExpr {
 impl Eval for WhileExpr {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let flow = vm.flow.take();
         let mut output = Value::None;
 
@@ -838,7 +817,7 @@ impl Eval for WhileExpr {
 impl Eval for ForExpr {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let flow = vm.flow.take();
         let mut output = Value::None;
         vm.scopes.enter();
@@ -917,7 +896,7 @@ impl Eval for ForExpr {
 impl Eval for ImportExpr {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let span = self.path().span();
         let path = self.path().eval(vm)?.cast::<EcoString>().at(span)?;
         let module = import(vm, &path, span)?;
@@ -946,7 +925,7 @@ impl Eval for ImportExpr {
 impl Eval for IncludeExpr {
     type Output = Content;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let span = self.path().span();
         let path = self.path().eval(vm)?.cast::<EcoString>().at(span)?;
         let module = import(vm, &path, span)?;
@@ -955,10 +934,14 @@ impl Eval for IncludeExpr {
 }
 
 /// Process an import of a module relative to the current location.
-fn import(vm: &mut Machine, path: &str, span: Span) -> TypResult<Module> {
+fn import(vm: &mut Vm, path: &str, span: Span) -> TypResult<Module> {
     // Load the source file.
     let full = vm.locate(&path).at(span)?;
-    let id = vm.ctx.sources.load(&full).at(span)?;
+    let id = vm
+        .world
+        .resolve(&full)
+        .map_err(|err| failed_to_load("source file", &full, err))
+        .at(span)?;
 
     // Prevent cyclic importing.
     if vm.route.contains(&id) {
@@ -968,9 +951,7 @@ fn import(vm: &mut Machine, path: &str, span: Span) -> TypResult<Module> {
     // Evaluate the file.
     let route = vm.route.clone();
     let module =
-        evaluate(vm.ctx, id, route).trace(vm.ctx, || Tracepoint::Import, span)?;
-
-    vm.deps.extend(module.deps.iter().cloned());
+        evaluate(vm.world, id, route).trace(vm.world, || Tracepoint::Import, span)?;
 
     Ok(module)
 }
@@ -978,7 +959,7 @@ fn import(vm: &mut Machine, path: &str, span: Span) -> TypResult<Module> {
 impl Eval for BreakExpr {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         if vm.flow.is_none() {
             vm.flow = Some(Flow::Break(self.span()));
         }
@@ -989,7 +970,7 @@ impl Eval for BreakExpr {
 impl Eval for ContinueExpr {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         if vm.flow.is_none() {
             vm.flow = Some(Flow::Continue(self.span()));
         }
@@ -1000,7 +981,7 @@ impl Eval for ContinueExpr {
 impl Eval for ReturnExpr {
     type Output = Value;
 
-    fn eval(&self, vm: &mut Machine) -> TypResult<Self::Output> {
+    fn eval(&self, vm: &mut Vm) -> TypResult<Self::Output> {
         let value = self.body().map(|body| body.eval(vm)).transpose()?;
         if vm.flow.is_none() {
             vm.flow = Some(Flow::Return(self.span(), value));
@@ -1012,11 +993,11 @@ impl Eval for ReturnExpr {
 /// Access an expression mutably.
 pub trait Access {
     /// Access the value.
-    fn access<'a>(&self, vm: &'a mut Machine) -> TypResult<&'a mut Value>;
+    fn access<'a>(&self, vm: &'a mut Vm) -> TypResult<&'a mut Value>;
 }
 
 impl Access for Expr {
-    fn access<'a>(&self, vm: &'a mut Machine) -> TypResult<&'a mut Value> {
+    fn access<'a>(&self, vm: &'a mut Vm) -> TypResult<&'a mut Value> {
         match self {
             Expr::Ident(v) => v.access(vm),
             Expr::FieldAccess(v) => v.access(vm),
@@ -1027,13 +1008,13 @@ impl Access for Expr {
 }
 
 impl Access for Ident {
-    fn access<'a>(&self, vm: &'a mut Machine) -> TypResult<&'a mut Value> {
+    fn access<'a>(&self, vm: &'a mut Vm) -> TypResult<&'a mut Value> {
         vm.scopes.get_mut(self).at(self.span())
     }
 }
 
 impl Access for FieldAccess {
-    fn access<'a>(&self, vm: &'a mut Machine) -> TypResult<&'a mut Value> {
+    fn access<'a>(&self, vm: &'a mut Vm) -> TypResult<&'a mut Value> {
         Ok(match self.object().access(vm)? {
             Value::Dict(dict) => dict.get_mut(self.field().take().into()),
             v => bail!(
@@ -1046,7 +1027,7 @@ impl Access for FieldAccess {
 }
 
 impl Access for FuncCall {
-    fn access<'a>(&self, vm: &'a mut Machine) -> TypResult<&'a mut Value> {
+    fn access<'a>(&self, vm: &'a mut Vm) -> TypResult<&'a mut Value> {
         let args = self.args().eval(vm)?;
         Ok(match self.callee().access(vm)? {
             Value::Array(array) => array.get_mut(args.into_index()?).at(self.span())?,
diff --git a/src/eval/scope.rs b/src/eval/scope.rs
index 7c624de0..1b11e6ea 100644
--- a/src/eval/scope.rs
+++ b/src/eval/scope.rs
@@ -2,7 +2,7 @@ use std::collections::BTreeMap;
 use std::fmt::{self, Debug, Formatter};
 use std::hash::Hash;
 
-use super::{Args, Func, Machine, Node, Value};
+use super::{Args, Func, Node, Value, Vm};
 use crate::diag::{StrResult, TypResult};
 use crate::util::EcoString;
 
@@ -78,7 +78,7 @@ impl Scope {
     pub fn def_fn(
         &mut self,
         name: &'static str,
-        func: fn(&mut Machine, &mut Args) -> TypResult<Value>,
+        func: fn(&mut Vm, &mut Args) -> TypResult<Value>,
     ) {
         self.define(name, Func::from_fn(name, func));
     }
diff --git a/src/eval/machine.rs b/src/eval/vm.rs
index 9c58c659..937152cf 100644
--- a/src/eval/machine.rs
+++ b/src/eval/vm.rs
@@ -5,32 +5,24 @@ use crate::diag::{StrResult, TypError};
 use crate::source::SourceId;
 use crate::syntax::Span;
 use crate::util::PathExt;
-use crate::Context;
+use crate::World;
 
 /// A virtual machine.
-pub struct Machine<'a> {
+pub struct Vm<'w> {
     /// The core context.
-    pub ctx: &'a mut Context,
+    pub world: &'w dyn World,
     /// The route of source ids the machine took to reach its current location.
     pub route: Vec<SourceId>,
-    /// The dependencies of the current evaluation process.
-    pub deps: Vec<(SourceId, usize)>,
     /// The stack of scopes.
-    pub scopes: Scopes<'a>,
+    pub scopes: Scopes<'w>,
     /// A control flow event that is currently happening.
     pub flow: Option<Flow>,
 }
 
-impl<'a> Machine<'a> {
+impl<'w> Vm<'w> {
     /// Create a new virtual machine.
-    pub fn new(ctx: &'a mut Context, route: Vec<SourceId>, scopes: Scopes<'a>) -> Self {
-        Self {
-            ctx,
-            route,
-            deps: vec![],
-            scopes,
-            flow: None,
-        }
+    pub fn new(ctx: &'w dyn World, route: Vec<SourceId>, scopes: Scopes<'w>) -> Self {
+        Self { world: ctx, route, scopes, flow: None }
     }
 
     /// Resolve a user-entered path to be relative to the compilation
@@ -38,10 +30,10 @@ impl<'a> Machine<'a> {
     pub fn locate(&self, path: &str) -> StrResult<PathBuf> {
         if let Some(&id) = self.route.last() {
             if let Some(path) = path.strip_prefix('/') {
-                return Ok(self.ctx.config.root.join(path).normalize());
+                return Ok(self.world.config().root.join(path).normalize());
             }
 
-            if let Some(dir) = self.ctx.sources.get(id).path().parent() {
+            if let Some(dir) = self.world.source(id).path().parent() {
                 return Ok(dir.join(path).normalize());
             }
         }
diff --git a/src/export/pdf/image.rs b/src/export/pdf/image.rs
index 7886524c..f148bb7d 100644
--- a/src/export/pdf/image.rs
+++ b/src/export/pdf/image.rs
@@ -16,48 +16,40 @@ pub fn write_images(ctx: &mut PdfContext) {
         let height = image.height();
 
         // Add the primary image.
+        // TODO: Error if image could not be encoded.
         match image.decode().unwrap() {
             DecodedImage::Raster(dynamic) => {
-                if let Ok((data, filter, has_color)) =
-                    encode_image(image.format(), &dynamic)
-                {
-                    let mut image = ctx.writer.image_xobject(image_ref, &data);
-                    image.filter(filter);
-                    image.width(width as i32);
-                    image.height(height as i32);
-                    image.bits_per_component(8);
-
-                    let space = image.color_space();
-                    if has_color {
-                        space.device_rgb();
-                    } else {
-                        space.device_gray();
-                    }
-
-                    // Add a second gray-scale image containing the alpha values if
-                    // this image has an alpha channel.
-                    if dynamic.color().has_alpha() {
-                        let (alpha_data, alpha_filter) = encode_alpha(&dynamic);
-                        let mask_ref = ctx.alloc.bump();
-                        image.s_mask(mask_ref);
-                        image.finish();
-
-                        let mut mask = ctx.writer.image_xobject(mask_ref, &alpha_data);
-                        mask.filter(alpha_filter);
-                        mask.width(width as i32);
-                        mask.height(height as i32);
-                        mask.color_space().device_gray();
-                        mask.bits_per_component(8);
-                    }
+                // TODO: Error if image could not be encoded.
+                let (data, filter, has_color) =
+                    encode_image(image.format(), &dynamic).unwrap();
+
+                let mut image = ctx.writer.image_xobject(image_ref, &data);
+                image.filter(filter);
+                image.width(width as i32);
+                image.height(height as i32);
+                image.bits_per_component(8);
+
+                let space = image.color_space();
+                if has_color {
+                    space.device_rgb();
                 } else {
-                    // TODO: Warn that image could not be encoded.
-                    ctx.writer
-                        .image_xobject(image_ref, &[])
-                        .width(0)
-                        .height(0)
-                        .bits_per_component(1)
-                        .color_space()
-                        .device_gray();
+                    space.device_gray();
+                }
+
+                // Add a second gray-scale image containing the alpha values if
+                // this image has an alpha channel.
+                if dynamic.color().has_alpha() {
+                    let (alpha_data, alpha_filter) = encode_alpha(&dynamic);
+                    let mask_ref = ctx.alloc.bump();
+                    image.s_mask(mask_ref);
+                    image.finish();
+
+                    let mut mask = ctx.writer.image_xobject(mask_ref, &alpha_data);
+                    mask.filter(alpha_filter);
+                    mask.width(width as i32);
+                    mask.height(height as i32);
+                    mask.color_space().device_gray();
+                    mask.bits_per_component(8);
                 }
             }
             DecodedImage::Svg(svg) => {
diff --git a/src/export/render.rs b/src/export/render.rs
index bf735ded..3fb57ad6 100644
--- a/src/export/render.rs
+++ b/src/export/render.rs
@@ -147,8 +147,8 @@ fn render_svg_glyph(
     }
 
     // Parse XML.
-    let src = std::str::from_utf8(data).ok()?;
-    let document = roxmltree::Document::parse(src).ok()?;
+    let xml = std::str::from_utf8(data).ok()?;
+    let document = roxmltree::Document::parse(xml).ok()?;
     let root = document.root_element();
 
     // Parse SVG.
diff --git a/src/font/book.rs b/src/font/book.rs
index 8f19faf7..323eb84f 100644
--- a/src/font/book.rs
+++ b/src/font/book.rs
@@ -39,8 +39,8 @@ impl FontBook {
         self.infos.push(info);
     }
 
-    /// An ordered iterator over all font families this loader knows and details
-    /// about the faces that are part of them.
+    /// An ordered iterator over all font families this book knows and details
+    /// about the fonts that are part of them.
     pub fn families(
         &self,
     ) -> impl Iterator<Item = (&str, impl Iterator<Item = &FontInfo>)> + '_ {
diff --git a/src/font/mod.rs b/src/font/mod.rs
index 917fea62..2404ad32 100644
--- a/src/font/mod.rs
+++ b/src/font/mod.rs
@@ -15,7 +15,7 @@ use rex::font::MathHeader;
 use ttf_parser::{GlyphId, Tag};
 
 use crate::geom::Em;
-use crate::loading::Buffer;
+use crate::util::Buffer;
 
 /// An OpenType font.
 #[derive(Clone)]
diff --git a/src/image.rs b/src/image.rs
index c2631477..db10a162 100644
--- a/src/image.rs
+++ b/src/image.rs
@@ -2,7 +2,7 @@
 
 use std::io;
 
-use crate::loading::Buffer;
+use crate::util::Buffer;
 
 /// A raster or vector image.
 ///
diff --git a/src/lib.rs b/src/lib.rs
index c26ef809..84d91d44 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -44,117 +44,75 @@ pub mod font;
 pub mod frame;
 pub mod image;
 pub mod library;
-pub mod loading;
 pub mod model;
 pub mod parse;
 pub mod source;
 pub mod syntax;
 
-use std::path::PathBuf;
-use std::sync::Arc;
+use std::io;
+use std::path::{Path, PathBuf};
 
 use crate::diag::TypResult;
 use crate::eval::Scope;
+use crate::font::{Font, FontBook};
 use crate::frame::Frame;
-use crate::loading::Loader;
 use crate::model::StyleMap;
-use crate::source::{SourceId, SourceStore};
+use crate::source::{Source, SourceId};
+use crate::util::Buffer;
 
 /// Typeset a source file into a collection of layouted frames.
 ///
 /// Returns either a vector of frames representing individual pages or
 /// diagnostics in the form of a vector of error message with file and span
 /// information.
-pub fn typeset(ctx: &mut Context, id: SourceId) -> TypResult<Vec<Frame>> {
-    let module = eval::evaluate(ctx, id, vec![])?;
-    model::layout(ctx, &module.content)
+pub fn typeset(world: &dyn World, main: SourceId) -> TypResult<Vec<Frame>> {
+    let module = eval::evaluate(world, main, vec![])?;
+    model::layout(world, &module.content)
 }
 
-/// The core context which holds the configuration and stores.
-pub struct Context {
-    /// The loader for fonts and files.
-    pub loader: Arc<dyn Loader>,
-    /// Stores loaded source files.
-    pub sources: SourceStore,
-    /// The context's configuration.
-    config: Config,
-}
+/// The environment in which typesetting occurs.
+pub trait World {
+    /// Access the global configuration.
+    fn config(&self) -> &Config;
 
-impl Context {
-    /// Create a new context.
-    pub fn new(loader: Arc<dyn Loader>, config: Config) -> Self {
-        Self {
-            loader: Arc::clone(&loader),
-            sources: SourceStore::new(Arc::clone(&loader)),
-            config,
-        }
-    }
-}
+    /// Resolve the unique id of a source file.
+    fn resolve(&self, path: &Path) -> io::Result<SourceId>;
 
-/// Compilation configuration.
-pub struct Config {
-    /// The compilation root.
-    pub root: PathBuf,
-    /// The standard library scope.
-    pub std: Arc<Scope>,
-    /// The default styles.
-    pub styles: Arc<StyleMap>,
-}
+    /// Access a source file by id.
+    fn source(&self, id: SourceId) -> &Source;
 
-impl Config {
-    /// Create a new configuration builder.
-    pub fn builder() -> ConfigBuilder {
-        ConfigBuilder::default()
-    }
-}
+    /// Metadata about all known fonts.
+    fn book(&self) -> &FontBook;
 
-impl Default for Config {
-    fn default() -> Self {
-        Self::builder().build()
-    }
-}
+    /// Access the font with the given id.
+    fn font(&self, id: usize) -> io::Result<Font>;
 
-/// A builder for a [`Config`].
-///
-/// This struct is created by [`Config::builder`].
-#[derive(Debug, Default, Clone)]
-pub struct ConfigBuilder {
-    root: PathBuf,
-    std: Option<Arc<Scope>>,
-    styles: Option<Arc<StyleMap>>,
+    /// Access a file at a path.
+    fn file(&self, path: &Path) -> io::Result<Buffer>;
 }
 
-impl ConfigBuilder {
+/// The global configuration for typesetting.
+pub struct Config {
     /// The compilation root, relative to which absolute paths are.
     ///
     /// Default: Empty path.
-    pub fn root(&mut self, root: impl Into<PathBuf>) -> &mut Self {
-        self.root = root.into();
-        self
-    }
-
+    pub root: PathBuf,
     /// The scope containing definitions that are available everywhere.
     ///
     /// Default: Typst's standard library.
-    pub fn std(&mut self, std: impl Into<Arc<Scope>>) -> &mut Self {
-        self.std = Some(std.into());
-        self
-    }
-
+    pub std: Scope,
     /// The default properties for page size, font selection and so on.
     ///
     /// Default: Empty style map.
-    pub fn styles(&mut self, styles: impl Into<Arc<StyleMap>>) -> &mut Self {
-        self.styles = Some(styles.into());
-        self
-    }
+    pub styles: StyleMap,
+}
 
-    /// Finish building the configuration.
-    pub fn build(&self) -> Config {
-        Config {
-            root: self.root.clone(),
-            std: self.std.clone().unwrap_or_else(|| Arc::new(library::new())),
-            styles: self.styles.clone().unwrap_or_default(),
+impl Default for Config {
+    fn default() -> Self {
+        Self {
+            root: PathBuf::new(),
+            std: library::new(),
+            styles: StyleMap::new(),
         }
     }
 }
diff --git a/src/library/graphics/hide.rs b/src/library/graphics/hide.rs
index f40635a0..f2a423ce 100644
--- a/src/library/graphics/hide.rs
+++ b/src/library/graphics/hide.rs
@@ -6,7 +6,7 @@ pub struct HideNode(pub LayoutNode);
 
 #[node]
 impl HideNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::inline(Self(args.expect("body")?)))
     }
 }
@@ -14,11 +14,11 @@ impl HideNode {
 impl Layout for HideNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
-        let mut frames = self.0.layout(ctx, regions, styles)?;
+        let mut frames = self.0.layout(world, regions, styles)?;
         for frame in &mut frames {
             frame.clear();
         }
diff --git a/src/library/graphics/image.rs b/src/library/graphics/image.rs
index f8cdc4cd..1642c7b0 100644
--- a/src/library/graphics/image.rs
+++ b/src/library/graphics/image.rs
@@ -13,15 +13,14 @@ impl ImageNode {
     /// How the image should adjust itself to a given area.
     pub const FIT: ImageFit = ImageFit::Cover;
 
-    fn construct(vm: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(vm: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let Spanned { v: path, span } =
             args.expect::<Spanned<EcoString>>("path to image file")?;
 
         let full = vm.locate(&path).at(span)?;
         let ext = full.extension().and_then(OsStr::to_str).unwrap_or_default();
         let image = vm
-            .ctx
-            .loader
+            .world
             .file(&full)
             .and_then(|buffer| Image::new(buffer, ext))
             .map_err(|err| failed_to_load("image", &full, err))
@@ -39,7 +38,7 @@ impl ImageNode {
 impl Layout for ImageNode {
     fn layout(
         &self,
-        _: &mut Context,
+        _: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
diff --git a/src/library/graphics/line.rs b/src/library/graphics/line.rs
index 15c54f46..95c3a709 100644
--- a/src/library/graphics/line.rs
+++ b/src/library/graphics/line.rs
@@ -15,7 +15,7 @@ impl LineNode {
     #[property(resolve, fold)]
     pub const STROKE: RawStroke = RawStroke::default();
 
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let origin = args.named("origin")?.unwrap_or_default();
 
         let delta = match args.named::<Spec<Relative<RawLength>>>("to")? {
@@ -40,7 +40,7 @@ impl LineNode {
 impl Layout for LineNode {
     fn layout(
         &self,
-        _: &mut Context,
+        _: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
diff --git a/src/library/graphics/shape.rs b/src/library/graphics/shape.rs
index 5cc5a76d..ee5e43e8 100644
--- a/src/library/graphics/shape.rs
+++ b/src/library/graphics/shape.rs
@@ -39,7 +39,7 @@ impl<const S: ShapeKind> ShapeNode<S> {
     pub const RADIUS: Corners<Option<Relative<RawLength>>> =
         Corners::splat(Relative::zero());
 
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let size = match S {
             SQUARE => args.named::<RawLength>("size")?.map(Relative::from),
             CIRCLE => args.named::<RawLength>("radius")?.map(|r| 2.0 * Relative::from(r)),
@@ -78,7 +78,7 @@ impl<const S: ShapeKind> ShapeNode<S> {
 impl<const S: ShapeKind> Layout for ShapeNode<S> {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
@@ -93,7 +93,7 @@ impl<const S: ShapeKind> Layout for ShapeNode<S> {
             let child = child.clone().padded(inset.map(|side| side.map(RawLength::from)));
 
             let mut pod = Regions::one(regions.first, regions.base, regions.expand);
-            frames = child.layout(ctx, &pod, styles)?;
+            frames = child.layout(world, &pod, styles)?;
 
             for frame in frames.iter_mut() {
                 frame.apply_role(Role::GenericBlock);
@@ -113,7 +113,7 @@ impl<const S: ShapeKind> Layout for ShapeNode<S> {
 
                 pod.first = Size::splat(length);
                 pod.expand = Spec::splat(true);
-                frames = child.layout(ctx, &pod, styles)?;
+                frames = child.layout(world, &pod, styles)?;
             }
         } else {
             // The default size that a shape takes on if it has no child and
diff --git a/src/library/graphics/transform.rs b/src/library/graphics/transform.rs
index 48cadb1b..0a4f5b5f 100644
--- a/src/library/graphics/transform.rs
+++ b/src/library/graphics/transform.rs
@@ -12,7 +12,7 @@ pub struct MoveNode {
 
 #[node]
 impl MoveNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let dx = args.named("dx")?.unwrap_or_default();
         let dy = args.named("dy")?.unwrap_or_default();
         Ok(Content::inline(Self {
@@ -25,11 +25,11 @@ impl MoveNode {
 impl Layout for MoveNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
-        let mut frames = self.child.layout(ctx, regions, styles)?;
+        let mut frames = self.child.layout(world, regions, styles)?;
 
         let delta = self.delta.resolve(styles);
         for frame in &mut frames {
@@ -62,7 +62,7 @@ impl<const T: TransformKind> TransformNode<T> {
     #[property(resolve)]
     pub const ORIGIN: Spec<Option<RawAlign>> = Spec::default();
 
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let transform = match T {
             ROTATE => {
                 let angle = args.named_or_find("angle")?.unwrap_or_default();
@@ -86,12 +86,12 @@ impl<const T: TransformKind> TransformNode<T> {
 impl<const T: TransformKind> Layout for TransformNode<T> {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
         let origin = styles.get(Self::ORIGIN).unwrap_or(Align::CENTER_HORIZON);
-        let mut frames = self.child.layout(ctx, regions, styles)?;
+        let mut frames = self.child.layout(world, regions, styles)?;
 
         for frame in &mut frames {
             let Spec { x, y } = origin.zip(frame.size()).map(|(o, s)| o.position(s));
diff --git a/src/library/layout/align.rs b/src/library/layout/align.rs
index e7a27c04..3b1a4aaf 100644
--- a/src/library/layout/align.rs
+++ b/src/library/layout/align.rs
@@ -12,7 +12,7 @@ pub struct AlignNode {
 
 #[node]
 impl AlignNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let aligns: Spec<Option<RawAlign>> = args.find()?.unwrap_or_default();
         let body: Content = args.expect("body")?;
         Ok(match (body, aligns) {
@@ -28,7 +28,7 @@ impl AlignNode {
 impl Layout for AlignNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
@@ -43,7 +43,7 @@ impl Layout for AlignNode {
         }
 
         // Layout the child.
-        let mut frames = self.child.layout(ctx, &pod, passed.chain(&styles))?;
+        let mut frames = self.child.layout(world, &pod, passed.chain(&styles))?;
         for (region, frame) in regions.iter().zip(&mut frames) {
             // Align in the target size. The target size depends on whether we
             // should expand.
diff --git a/src/library/layout/columns.rs b/src/library/layout/columns.rs
index efc435aa..bfbbfd8d 100644
--- a/src/library/layout/columns.rs
+++ b/src/library/layout/columns.rs
@@ -17,7 +17,7 @@ impl ColumnsNode {
     #[property(resolve)]
     pub const GUTTER: Relative<RawLength> = Ratio::new(0.04).into();
 
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::block(Self {
             columns: args.expect("column count")?,
             child: args.expect("body")?,
@@ -28,14 +28,14 @@ impl ColumnsNode {
 impl Layout for ColumnsNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
         // Separating the infinite space into infinite columns does not make
         // much sense.
         if !regions.first.x.is_finite() {
-            return self.child.layout(ctx, regions, styles);
+            return self.child.layout(world, regions, styles);
         }
 
         // Determine the width of the gutter and each column.
@@ -57,7 +57,7 @@ impl Layout for ColumnsNode {
         };
 
         // Layout the children.
-        let mut frames = self.child.layout(ctx, &pod, styles)?.into_iter();
+        let mut frames = self.child.layout(world, &pod, styles)?.into_iter();
         let mut finished = vec![];
 
         let dir = styles.get(TextNode::DIR);
@@ -106,7 +106,7 @@ pub struct ColbreakNode;
 
 #[node]
 impl ColbreakNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let weak = args.named("weak")?.unwrap_or(false);
         Ok(Content::Colbreak { weak })
     }
diff --git a/src/library/layout/container.rs b/src/library/layout/container.rs
index df03ac91..66a43751 100644
--- a/src/library/layout/container.rs
+++ b/src/library/layout/container.rs
@@ -5,7 +5,7 @@ pub struct BoxNode;
 
 #[node]
 impl BoxNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let width = args.named("width")?;
         let height = args.named("height")?;
         let body: LayoutNode = args.eat()?.unwrap_or_default();
@@ -18,7 +18,7 @@ pub struct BlockNode;
 
 #[node]
 impl BlockNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::Block(args.eat()?.unwrap_or_default()))
     }
 }
diff --git a/src/library/layout/flow.rs b/src/library/layout/flow.rs
index c6d2999e..841b80aa 100644
--- a/src/library/layout/flow.rs
+++ b/src/library/layout/flow.rs
@@ -25,7 +25,7 @@ pub enum FlowChild {
 impl Layout for FlowNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
@@ -38,7 +38,7 @@ impl Layout for FlowNode {
                     layouter.layout_spacing(*kind, styles);
                 }
                 FlowChild::Node(ref node) => {
-                    layouter.layout_node(ctx, node, styles)?;
+                    layouter.layout_node(world, node, styles)?;
                 }
                 FlowChild::Colbreak => {
                     layouter.finish_region();
@@ -149,7 +149,7 @@ impl FlowLayouter {
     /// Layout a node.
     pub fn layout_node(
         &mut self,
-        ctx: &mut Context,
+        world: &dyn World,
         node: &LayoutNode,
         styles: StyleChain,
     ) -> TypResult<()> {
@@ -162,7 +162,7 @@ impl FlowLayouter {
         // aligned later.
         if let Some(placed) = node.downcast::<PlaceNode>() {
             if placed.out_of_flow() {
-                let frame = node.layout(ctx, &self.regions, styles)?.remove(0);
+                let frame = node.layout(world, &self.regions, styles)?.remove(0);
                 self.items.push(FlowItem::Placed(frame));
                 return Ok(());
             }
@@ -180,7 +180,7 @@ impl FlowLayouter {
                 .unwrap_or(Align::Top),
         );
 
-        let frames = node.layout(ctx, &self.regions, styles)?;
+        let frames = node.layout(world, &self.regions, styles)?;
         let len = frames.len();
         for (i, mut frame) in frames.into_iter().enumerate() {
             // Set the generic block role.
diff --git a/src/library/layout/grid.rs b/src/library/layout/grid.rs
index 93dbf97e..3fde9c10 100644
--- a/src/library/layout/grid.rs
+++ b/src/library/layout/grid.rs
@@ -13,7 +13,7 @@ pub struct GridNode {
 
 #[node]
 impl GridNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let columns = args.named("columns")?.unwrap_or_default();
         let rows = args.named("rows")?.unwrap_or_default();
         let base_gutter: Vec<TrackSizing> = args.named("gutter")?.unwrap_or_default();
@@ -33,13 +33,13 @@ impl GridNode {
 impl Layout for GridNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
         // Prepare grid layout by unifying content and gutter tracks.
         let layouter = GridLayouter::new(
-            ctx,
+            world,
             self.tracks.as_deref(),
             self.gutter.as_deref(),
             &self.cells,
@@ -93,7 +93,7 @@ castable! {
 /// Performs grid layout.
 pub struct GridLayouter<'a> {
     /// The core context.
-    ctx: &'a mut Context,
+    world: &'a dyn World,
     /// The grid cells.
     cells: &'a [LayoutNode],
     /// The column tracks including gutter tracks.
@@ -133,7 +133,7 @@ impl<'a> GridLayouter<'a> {
     ///
     /// This prepares grid layout by unifying content and gutter tracks.
     pub fn new(
-        ctx: &'a mut Context,
+        world: &'a dyn World,
         tracks: Spec<&[TrackSizing]>,
         gutter: Spec<&[TrackSizing]>,
         cells: &'a [LayoutNode],
@@ -187,7 +187,7 @@ impl<'a> GridLayouter<'a> {
         regions.expand = Spec::new(true, false);
 
         Self {
-            ctx,
+            world,
             cells,
             cols,
             rows,
@@ -301,7 +301,7 @@ impl<'a> GridLayouter<'a> {
                             v.resolve(self.styles).relative_to(self.regions.base.y);
                     }
 
-                    let frame = node.layout(self.ctx, &pod, self.styles)?.remove(0);
+                    let frame = node.layout(self.world, &pod, self.styles)?.remove(0);
                     resolved.set_max(frame.width());
                 }
             }
@@ -371,7 +371,7 @@ impl<'a> GridLayouter<'a> {
                 }
 
                 let mut sizes = node
-                    .layout(self.ctx, &pod, self.styles)?
+                    .layout(self.world, &pod, self.styles)?
                     .into_iter()
                     .map(|frame| frame.height());
 
@@ -460,7 +460,7 @@ impl<'a> GridLayouter<'a> {
                     .select(self.regions.base, size);
 
                 let pod = Regions::one(size, base, Spec::splat(true));
-                let frame = node.layout(self.ctx, &pod, self.styles)?.remove(0);
+                let frame = node.layout(self.world, &pod, self.styles)?.remove(0);
                 match frame.role() {
                     Some(Role::ListLabel | Role::ListItemBody) => {
                         output.apply_role(Role::ListItem)
@@ -508,7 +508,7 @@ impl<'a> GridLayouter<'a> {
                 }
 
                 // Push the layouted frames into the individual output frames.
-                let frames = node.layout(self.ctx, &pod, self.styles)?;
+                let frames = node.layout(self.world, &pod, self.styles)?;
                 for (output, frame) in outputs.iter_mut().zip(frames) {
                     match frame.role() {
                         Some(Role::ListLabel | Role::ListItemBody) => {
diff --git a/src/library/layout/pad.rs b/src/library/layout/pad.rs
index 9d91c641..72235ccd 100644
--- a/src/library/layout/pad.rs
+++ b/src/library/layout/pad.rs
@@ -11,7 +11,7 @@ pub struct PadNode {
 
 #[node]
 impl PadNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let all = args.named("rest")?.or(args.find()?);
         let x = args.named("x")?;
         let y = args.named("y")?;
@@ -28,14 +28,14 @@ impl PadNode {
 impl Layout for PadNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
         // Layout child into padded regions.
         let padding = self.padding.resolve(styles);
         let pod = regions.map(|size| shrink(size, padding));
-        let mut frames = self.child.layout(ctx, &pod, styles)?;
+        let mut frames = self.child.layout(world, &pod, styles)?;
 
         for frame in &mut frames {
             // Apply the padding inversely such that the grown size padded
diff --git a/src/library/layout/page.rs b/src/library/layout/page.rs
index afcc4855..6e43c4ef 100644
--- a/src/library/layout/page.rs
+++ b/src/library/layout/page.rs
@@ -41,7 +41,7 @@ impl PageNode {
     #[property(referenced)]
     pub const FOREGROUND: Marginal = Marginal::None;
 
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::Page(Self(args.expect("body")?)))
     }
 
@@ -57,7 +57,7 @@ impl PageNode {
     /// Layout the page run into a sequence of frames, one per page.
     pub fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         mut page: usize,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
@@ -97,7 +97,7 @@ impl PageNode {
 
         // Layout the child.
         let regions = Regions::repeat(size, size, size.map(Length::is_finite));
-        let mut frames = child.layout(ctx, &regions, styles)?;
+        let mut frames = child.layout(world, &regions, styles)?;
 
         let header = styles.get(Self::HEADER);
         let footer = styles.get(Self::FOOTER);
@@ -126,9 +126,9 @@ impl PageNode {
                 (Role::Foreground, foreground, Point::zero(), size),
                 (Role::Background, background, Point::zero(), size),
             ] {
-                if let Some(content) = marginal.resolve(ctx, page)? {
+                if let Some(content) = marginal.resolve(world, page)? {
                     let pod = Regions::one(area, area, Spec::splat(true));
-                    let mut sub = content.layout(ctx, &pod, styles)?.remove(0);
+                    let mut sub = content.layout(world, &pod, styles)?.remove(0);
                     sub.apply_role(role);
 
                     if role == Role::Background {
@@ -159,7 +159,7 @@ pub struct PagebreakNode;
 
 #[node]
 impl PagebreakNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let weak = args.named("weak")?.unwrap_or(false);
         Ok(Content::Pagebreak { weak })
     }
@@ -178,13 +178,13 @@ pub enum Marginal {
 
 impl Marginal {
     /// Resolve the marginal based on the page number.
-    pub fn resolve(&self, ctx: &mut Context, page: usize) -> TypResult<Option<Content>> {
+    pub fn resolve(&self, world: &dyn World, page: usize) -> TypResult<Option<Content>> {
         Ok(match self {
             Self::None => None,
             Self::Content(content) => Some(content.clone()),
             Self::Func(func, span) => {
                 let args = Args::new(*span, [Value::Int(page as i64)]);
-                Some(func.call_detached(ctx, args)?.display())
+                Some(func.call_detached(world, args)?.display())
             }
         })
     }
diff --git a/src/library/layout/place.rs b/src/library/layout/place.rs
index 4c6d0062..bb3aac2d 100644
--- a/src/library/layout/place.rs
+++ b/src/library/layout/place.rs
@@ -7,7 +7,7 @@ pub struct PlaceNode(pub LayoutNode);
 
 #[node]
 impl PlaceNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let aligns = args.find()?.unwrap_or(Spec::with_x(Some(RawAlign::Start)));
         let dx = args.named("dx")?.unwrap_or_default();
         let dy = args.named("dy")?.unwrap_or_default();
@@ -21,7 +21,7 @@ impl PlaceNode {
 impl Layout for PlaceNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
@@ -35,7 +35,7 @@ impl Layout for PlaceNode {
             Regions::one(regions.base, regions.base, expand)
         };
 
-        let mut frames = self.0.layout(ctx, &pod, styles)?;
+        let mut frames = self.0.layout(world, &pod, styles)?;
 
         // If expansion is off, zero all sizes so that we don't take up any
         // space in our parent. Otherwise, respect the expand settings.
diff --git a/src/library/layout/spacing.rs b/src/library/layout/spacing.rs
index da4a96b6..e435e60c 100644
--- a/src/library/layout/spacing.rs
+++ b/src/library/layout/spacing.rs
@@ -8,7 +8,7 @@ pub struct HNode;
 
 #[node]
 impl HNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let amount = args.expect("spacing")?;
         let weak = args.named("weak")?.unwrap_or(false);
         Ok(Content::Horizontal { amount, weak })
@@ -20,7 +20,7 @@ pub struct VNode;
 
 #[node]
 impl VNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let amount = args.expect("spacing")?;
         let weak = args.named("weak")?.unwrap_or(false);
         Ok(Content::Vertical { amount, weak, generated: false })
diff --git a/src/library/layout/stack.rs b/src/library/layout/stack.rs
index d8dc0e1a..d07dc35e 100644
--- a/src/library/layout/stack.rs
+++ b/src/library/layout/stack.rs
@@ -15,7 +15,7 @@ pub struct StackNode {
 
 #[node]
 impl StackNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::block(Self {
             dir: args.named("dir")?.unwrap_or(Dir::TTB),
             spacing: args.named("spacing")?,
@@ -27,7 +27,7 @@ impl StackNode {
 impl Layout for StackNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
@@ -47,7 +47,7 @@ impl Layout for StackNode {
                         layouter.layout_spacing(kind);
                     }
 
-                    layouter.layout_node(ctx, node, styles)?;
+                    layouter.layout_node(world, node, styles)?;
                     deferred = self.spacing;
                 }
             }
@@ -168,7 +168,7 @@ impl<'a> StackLayouter<'a> {
     /// Layout an arbitrary node.
     pub fn layout_node(
         &mut self,
-        ctx: &mut Context,
+        world: &dyn World,
         node: &LayoutNode,
         styles: StyleChain,
     ) -> TypResult<()> {
@@ -193,7 +193,7 @@ impl<'a> StackLayouter<'a> {
                 self.dir.start().into()
             });
 
-        let frames = node.layout(ctx, &self.regions, styles)?;
+        let frames = node.layout(world, &self.regions, styles)?;
         let len = frames.len();
         for (i, mut frame) in frames.into_iter().enumerate() {
             // Set the generic block role.
diff --git a/src/library/math/mod.rs b/src/library/math/mod.rs
index 81593c4f..ed98ab1c 100644
--- a/src/library/math/mod.rs
+++ b/src/library/math/mod.rs
@@ -28,7 +28,7 @@ impl MathNode {
     #[property(resolve, shorthand(around))]
     pub const BELOW: Option<BlockSpacing> = Some(Ratio::one().into());
 
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::show(Self {
             formula: args.expect("formula")?,
             display: args.named("display")?.unwrap_or(false),
@@ -48,7 +48,7 @@ impl Show for MathNode {
         }
     }
 
-    fn realize(&self, _: &mut Context, styles: StyleChain) -> TypResult<Content> {
+    fn realize(&self, _: &dyn World, styles: StyleChain) -> TypResult<Content> {
         let node = self::rex::RexNode {
             tex: self.formula.clone(),
             display: self.display,
@@ -64,7 +64,7 @@ impl Show for MathNode {
 
     fn finalize(
         &self,
-        _: &mut Context,
+        _: &dyn World,
         styles: StyleChain,
         mut realized: Content,
     ) -> TypResult<Content> {
diff --git a/src/library/math/rex.rs b/src/library/math/rex.rs
index 0116b4b2..7bfdeb7a 100644
--- a/src/library/math/rex.rs
+++ b/src/library/math/rex.rs
@@ -22,17 +22,16 @@ pub struct RexNode {
 impl Layout for RexNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         _: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
         // Load the font.
         let span = self.tex.span;
-        let font = ctx
-            .loader
+        let font = world
             .book()
             .select(self.family.as_str(), variant(styles))
-            .and_then(|id| ctx.loader.font(id).ok())
+            .and_then(|id| world.font(id).ok())
             .ok_or("failed to find math font")
             .at(span)?;
 
diff --git a/src/library/prelude.rs b/src/library/prelude.rs
index 8bd3b815..a69d9791 100644
--- a/src/library/prelude.rs
+++ b/src/library/prelude.rs
@@ -12,16 +12,15 @@ pub use crate::diag::{
     failed_to_load, with_alternative, At, Error, StrResult, TypError, TypResult,
 };
 pub use crate::eval::{
-    Arg, Args, Array, Cast, Dict, Dynamic, Func, Machine, Node, RawAlign, RawLength,
-    RawStroke, Scope, Smart, Value,
+    Arg, Args, Array, Cast, Dict, Dynamic, Func, Node, RawAlign, RawLength, RawStroke,
+    Scope, Smart, Value, Vm,
 };
 pub use crate::frame::*;
 pub use crate::geom::*;
-pub use crate::loading::Loader;
 pub use crate::model::{
     Content, Fold, Key, Layout, LayoutNode, Regions, Resolve, Selector, Show, ShowNode,
     StyleChain, StyleMap, StyleVec,
 };
 pub use crate::syntax::{Span, Spanned};
 pub use crate::util::EcoString;
-pub use crate::Context;
+pub use crate::World;
diff --git a/src/library/structure/doc.rs b/src/library/structure/doc.rs
index 80472e24..cabdb4dc 100644
--- a/src/library/structure/doc.rs
+++ b/src/library/structure/doc.rs
@@ -7,11 +7,11 @@ pub struct DocNode(pub StyleVec<PageNode>);
 
 impl DocNode {
     /// Layout the document into a sequence of frames, one per page.
-    pub fn layout(&self, ctx: &mut Context, styles: StyleChain) -> TypResult<Vec<Frame>> {
+    pub fn layout(&self, world: &dyn World, styles: StyleChain) -> TypResult<Vec<Frame>> {
         let mut frames = vec![];
         for (page, map) in self.0.iter() {
             let number = 1 + frames.len();
-            frames.extend(page.layout(ctx, number, map.chain(&styles))?);
+            frames.extend(page.layout(world, number, map.chain(&styles))?);
         }
         Ok(frames)
     }
diff --git a/src/library/structure/heading.rs b/src/library/structure/heading.rs
index 24054f81..c177481f 100644
--- a/src/library/structure/heading.rs
+++ b/src/library/structure/heading.rs
@@ -60,7 +60,7 @@ impl HeadingNode {
     /// Whether the heading is numbered.
     pub const NUMBERED: bool = true;
 
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::show(Self {
             body: args.expect("body")?,
             level: args.named("level")?.unwrap_or(NonZeroUsize::new(1).unwrap()),
@@ -82,19 +82,19 @@ impl Show for HeadingNode {
         }
     }
 
-    fn realize(&self, _: &mut Context, _: StyleChain) -> TypResult<Content> {
+    fn realize(&self, _: &dyn World, _: StyleChain) -> TypResult<Content> {
         Ok(Content::block(self.body.clone()))
     }
 
     fn finalize(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         styles: StyleChain,
         mut realized: Content,
     ) -> TypResult<Content> {
         macro_rules! resolve {
             ($key:expr) => {
-                styles.get($key).resolve(ctx, self.level)?
+                styles.get($key).resolve(world, self.level)?
             };
         }
 
@@ -149,13 +149,13 @@ pub enum Leveled<T> {
 
 impl<T: Cast + Clone> Leveled<T> {
     /// Resolve the value based on the level.
-    pub fn resolve(&self, ctx: &mut Context, level: NonZeroUsize) -> TypResult<T> {
+    pub fn resolve(&self, world: &dyn World, level: NonZeroUsize) -> TypResult<T> {
         Ok(match self {
             Self::Value(value) => value.clone(),
             Self::Mapping(mapping) => mapping(level),
             Self::Func(func, span) => {
                 let args = Args::new(*span, [Value::Int(level.get() as i64)]);
-                func.call_detached(ctx, args)?.cast().at(*span)?
+                func.call_detached(world, args)?.cast().at(*span)?
             }
         })
     }
diff --git a/src/library/structure/list.rs b/src/library/structure/list.rs
index c4167cf9..e9365cd6 100644
--- a/src/library/structure/list.rs
+++ b/src/library/structure/list.rs
@@ -56,7 +56,7 @@ impl<const L: ListKind> ListNode<L> {
     #[property(resolve)]
     pub const SPACING: BlockSpacing = Ratio::one().into();
 
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::show(Self {
             start: args.named("start")?.unwrap_or(1),
             tight: args.named("tight")?.unwrap_or(true),
@@ -100,7 +100,7 @@ impl<const L: ListKind> Show for ListNode<L> {
         }
     }
 
-    fn realize(&self, ctx: &mut Context, styles: StyleChain) -> TypResult<Content> {
+    fn realize(&self, world: &dyn World, styles: StyleChain) -> TypResult<Content> {
         let mut cells = vec![];
         let mut number = self.start;
 
@@ -112,7 +112,7 @@ impl<const L: ListKind> Show for ListNode<L> {
             cells.push(LayoutNode::default());
             cells.push(
                 label
-                    .resolve(ctx, L, number)?
+                    .resolve(world, L, number)?
                     .styled_with_map(map.clone())
                     .role(Role::ListLabel)
                     .pack(),
@@ -145,7 +145,7 @@ impl<const L: ListKind> Show for ListNode<L> {
 
     fn finalize(
         &self,
-        _: &mut Context,
+        _: &dyn World,
         styles: StyleChain,
         realized: Content,
     ) -> TypResult<Content> {
@@ -208,7 +208,7 @@ impl Label {
     /// Resolve the value based on the level.
     pub fn resolve(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         kind: ListKind,
         number: usize,
     ) -> TypResult<Content> {
@@ -225,7 +225,7 @@ impl Label {
             Self::Content(content) => content.clone(),
             Self::Func(func, span) => {
                 let args = Args::new(*span, [Value::Int(number as i64)]);
-                func.call_detached(ctx, args)?.display()
+                func.call_detached(world, args)?.display()
             }
         })
     }
diff --git a/src/library/structure/reference.rs b/src/library/structure/reference.rs
index 0eeb4bf5..22dbec01 100644
--- a/src/library/structure/reference.rs
+++ b/src/library/structure/reference.rs
@@ -6,7 +6,7 @@ pub struct RefNode(pub EcoString);
 
 #[node(showable)]
 impl RefNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::show(Self(args.expect("label")?)))
     }
 }
@@ -22,7 +22,7 @@ impl Show for RefNode {
         }
     }
 
-    fn realize(&self, _: &mut Context, _: StyleChain) -> TypResult<Content> {
+    fn realize(&self, _: &dyn World, _: StyleChain) -> TypResult<Content> {
         Ok(Content::Text(format_eco!("@{}", self.0)))
     }
 }
diff --git a/src/library/structure/table.rs b/src/library/structure/table.rs
index 0f74fc96..08fa5386 100644
--- a/src/library/structure/table.rs
+++ b/src/library/structure/table.rs
@@ -30,7 +30,7 @@ impl TableNode {
     #[property(resolve, shorthand(around))]
     pub const BELOW: Option<BlockSpacing> = Some(Ratio::one().into());
 
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let columns = args.named("columns")?.unwrap_or_default();
         let rows = args.named("rows")?.unwrap_or_default();
         let base_gutter: Vec<TrackSizing> = args.named("gutter")?.unwrap_or_default();
@@ -72,7 +72,7 @@ impl Show for TableNode {
         }
     }
 
-    fn realize(&self, ctx: &mut Context, styles: StyleChain) -> TypResult<Content> {
+    fn realize(&self, world: &dyn World, styles: StyleChain) -> TypResult<Content> {
         let fill = styles.get(Self::FILL);
         let stroke = styles.get(Self::STROKE).map(RawStroke::unwrap_or_default);
         let padding = styles.get(Self::PADDING);
@@ -92,7 +92,7 @@ impl Show for TableNode {
 
                 let x = i % cols;
                 let y = i / cols;
-                if let Some(fill) = fill.resolve(ctx, x, y)? {
+                if let Some(fill) = fill.resolve(world, x, y)? {
                     child = child.filled(fill);
                 }
 
@@ -110,7 +110,7 @@ impl Show for TableNode {
 
     fn finalize(
         &self,
-        _: &mut Context,
+        _: &dyn World,
         styles: StyleChain,
         realized: Content,
     ) -> TypResult<Content> {
@@ -129,12 +129,12 @@ pub enum Celled<T> {
 
 impl<T: Cast + Clone> Celled<T> {
     /// Resolve the value based on the cell position.
-    pub fn resolve(&self, ctx: &mut Context, x: usize, y: usize) -> TypResult<T> {
+    pub fn resolve(&self, world: &dyn World, x: usize, y: usize) -> TypResult<T> {
         Ok(match self {
             Self::Value(value) => value.clone(),
             Self::Func(func, span) => {
                 let args = Args::new(*span, [Value::Int(x as i64), Value::Int(y as i64)]);
-                func.call_detached(ctx, args)?.cast().at(*span)?
+                func.call_detached(world, args)?.cast().at(*span)?
             }
         })
     }
diff --git a/src/library/text/deco.rs b/src/library/text/deco.rs
index 8295f1a2..c58148b4 100644
--- a/src/library/text/deco.rs
+++ b/src/library/text/deco.rs
@@ -34,7 +34,7 @@ impl<const L: DecoLine> DecoNode<L> {
     /// with the glyphs. Does not apply to strikethrough.
     pub const EVADE: bool = true;
 
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::show(Self(args.expect("body")?)))
     }
 }
@@ -48,7 +48,7 @@ impl<const L: DecoLine> Show for DecoNode<L> {
         dict! { "body" => Value::Content(self.0.clone()) }
     }
 
-    fn realize(&self, _: &mut Context, styles: StyleChain) -> TypResult<Content> {
+    fn realize(&self, _: &dyn World, styles: StyleChain) -> TypResult<Content> {
         Ok(self.0.clone().styled(TextNode::DECO, Decoration {
             line: L,
             stroke: styles.get(Self::STROKE).unwrap_or_default(),
diff --git a/src/library/text/link.rs b/src/library/text/link.rs
index c4898eb0..7d5c3109 100644
--- a/src/library/text/link.rs
+++ b/src/library/text/link.rs
@@ -18,7 +18,7 @@ impl LinkNode {
     /// Whether to underline the link.
     pub const UNDERLINE: Smart<bool> = Smart::Auto;
 
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::show({
             let dest = args.expect::<Destination>("destination")?;
             let body = match dest {
@@ -64,7 +64,7 @@ impl Show for LinkNode {
         }
     }
 
-    fn realize(&self, _: &mut Context, _: StyleChain) -> TypResult<Content> {
+    fn realize(&self, _: &dyn World, _: StyleChain) -> TypResult<Content> {
         Ok(self.body.clone().unwrap_or_else(|| match &self.dest {
             Destination::Url(url) => {
                 let mut text = url.as_str();
@@ -80,7 +80,7 @@ impl Show for LinkNode {
 
     fn finalize(
         &self,
-        _: &mut Context,
+        _: &dyn World,
         styles: StyleChain,
         mut realized: Content,
     ) -> TypResult<Content> {
diff --git a/src/library/text/mod.rs b/src/library/text/mod.rs
index 35780186..be586874 100644
--- a/src/library/text/mod.rs
+++ b/src/library/text/mod.rs
@@ -128,7 +128,7 @@ impl TextNode {
     #[property(skip, fold)]
     pub const DECO: Decoration = vec![];
 
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         // The text constructor is special: It doesn't create a text node.
         // Instead, it leaves the passed argument structurally unchanged, but
         // styles all text in it.
@@ -422,12 +422,12 @@ impl Fold for Vec<(Tag, u32)> {
 }
 
 /// Convert a string or content to lowercase.
-pub fn lower(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn lower(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     case(Case::Lower, args)
 }
 
 /// Convert a string or content to uppercase.
-pub fn upper(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn upper(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     case(Case::Upper, args)
 }
 
@@ -461,7 +461,7 @@ impl Case {
 }
 
 /// Display text in small capitals.
-pub fn smallcaps(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn smallcaps(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     let body: Content = args.expect("content")?;
     Ok(Value::Content(body.styled(TextNode::SMALLCAPS, true)))
 }
@@ -493,7 +493,7 @@ pub struct StrongNode(pub Content);
 
 #[node(showable)]
 impl StrongNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::show(Self(args.expect("body")?)))
     }
 }
@@ -507,7 +507,7 @@ impl Show for StrongNode {
         dict! { "body" => Value::Content(self.0.clone()) }
     }
 
-    fn realize(&self, _: &mut Context, _: StyleChain) -> TypResult<Content> {
+    fn realize(&self, _: &dyn World, _: StyleChain) -> TypResult<Content> {
         Ok(self.0.clone().styled(TextNode::BOLD, Toggle))
     }
 }
@@ -518,7 +518,7 @@ pub struct EmphNode(pub Content);
 
 #[node(showable)]
 impl EmphNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::show(Self(args.expect("body")?)))
     }
 }
@@ -532,7 +532,7 @@ impl Show for EmphNode {
         dict! { "body" => Value::Content(self.0.clone()) }
     }
 
-    fn realize(&self, _: &mut Context, _: StyleChain) -> TypResult<Content> {
+    fn realize(&self, _: &dyn World, _: StyleChain) -> TypResult<Content> {
         Ok(self.0.clone().styled(TextNode::ITALIC, Toggle))
     }
 }
diff --git a/src/library/text/par.rs b/src/library/text/par.rs
index 8309bcc8..e8282ef1 100644
--- a/src/library/text/par.rs
+++ b/src/library/text/par.rs
@@ -49,7 +49,7 @@ impl ParNode {
     #[property(resolve)]
     pub const LINEBREAKS: Smart<Linebreaks> = Smart::Auto;
 
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         // The paragraph constructor is special: It doesn't create a paragraph
         // node. Instead, it just ensures that the passed content lives is in a
         // separate paragraph and styles it.
@@ -64,7 +64,7 @@ impl ParNode {
 impl Layout for ParNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
@@ -74,13 +74,13 @@ impl Layout for ParNode {
         // Perform BiDi analysis and then prepare paragraph layout by building a
         // representation on which we can do line breaking without layouting
         // each and every line from scratch.
-        let p = prepare(ctx, self, &text, segments, regions, styles)?;
+        let p = prepare(world, self, &text, segments, regions, styles)?;
 
         // Break the paragraph into lines.
-        let lines = linebreak(&p, ctx.loader.as_ref(), regions.first.x);
+        let lines = linebreak(&p, world, regions.first.x);
 
         // Stack the lines into one frame per region.
-        stack(&p, ctx, &lines, regions)
+        stack(&p, world, &lines, regions)
     }
 }
 
@@ -170,7 +170,7 @@ pub struct ParbreakNode;
 
 #[node]
 impl ParbreakNode {
-    fn construct(_: &mut Machine, _: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, _: &mut Args) -> TypResult<Content> {
         Ok(Content::Parbreak)
     }
 }
@@ -180,7 +180,7 @@ pub struct LinebreakNode;
 
 #[node]
 impl LinebreakNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         let justified = args.named("justified")?.unwrap_or(false);
         Ok(Content::Linebreak { justified })
     }
@@ -496,7 +496,7 @@ fn collect<'a>(
 /// Prepare paragraph layout by shaping the whole paragraph and layouting all
 /// contained inline-level nodes.
 fn prepare<'a>(
-    ctx: &mut Context,
+    world: &dyn World,
     par: &'a ParNode,
     text: &'a str,
     segments: Vec<(Segment<'a>, StyleChain<'a>)>,
@@ -517,13 +517,7 @@ fn prepare<'a>(
         let end = cursor + segment.len();
         match segment {
             Segment::Text(_) => {
-                shape_range(
-                    &mut items,
-                    ctx.loader.as_ref(),
-                    &bidi,
-                    cursor .. end,
-                    styles,
-                );
+                shape_range(&mut items, world, &bidi, cursor .. end, styles);
             }
             Segment::Spacing(spacing) => match spacing {
                 Spacing::Relative(v) => {
@@ -540,7 +534,7 @@ fn prepare<'a>(
                 } else {
                     let size = Size::new(regions.first.x, regions.base.y);
                     let pod = Regions::one(size, regions.base, Spec::splat(false));
-                    let mut frame = node.layout(ctx, &pod, styles)?.remove(0);
+                    let mut frame = node.layout(world, &pod, styles)?.remove(0);
                     frame.translate(Point::with_y(styles.get(TextNode::BASELINE)));
                     frame.apply_role(Role::GenericInline);
                     items.push(Item::Frame(frame));
@@ -567,14 +561,14 @@ fn prepare<'a>(
 /// items for them.
 fn shape_range<'a>(
     items: &mut Vec<Item<'a>>,
-    loader: &dyn Loader,
+    world: &dyn World,
     bidi: &BidiInfo<'a>,
     range: Range,
     styles: StyleChain<'a>,
 ) {
     let mut process = |text, level: Level| {
         let dir = if level.is_ltr() { Dir::LTR } else { Dir::RTL };
-        let shaped = shape(loader, text, styles, dir);
+        let shaped = shape(world, text, styles, dir);
         items.push(Item::Text(shaped));
     };
 
@@ -633,12 +627,12 @@ fn shared_get<'a, K: Key<'a>>(
 /// Find suitable linebreaks.
 fn linebreak<'a>(
     p: &'a Preparation<'a>,
-    loader: &dyn Loader,
+    world: &dyn World,
     width: Length,
 ) -> Vec<Line<'a>> {
     match p.styles.get(ParNode::LINEBREAKS) {
-        Linebreaks::Simple => linebreak_simple(p, loader, width),
-        Linebreaks::Optimized => linebreak_optimized(p, loader, width),
+        Linebreaks::Simple => linebreak_simple(p, world, width),
+        Linebreaks::Optimized => linebreak_optimized(p, world, width),
     }
 }
 
@@ -647,7 +641,7 @@ fn linebreak<'a>(
 /// very unbalanced line, but is fast and simple.
 fn linebreak_simple<'a>(
     p: &'a Preparation<'a>,
-    loader: &dyn Loader,
+    world: &dyn World,
     width: Length,
 ) -> Vec<Line<'a>> {
     let mut lines = vec![];
@@ -656,7 +650,7 @@ fn linebreak_simple<'a>(
 
     for (end, mandatory, hyphen) in breakpoints(p) {
         // Compute the line and its size.
-        let mut attempt = line(p, loader, start .. end, mandatory, hyphen);
+        let mut attempt = line(p, world, start .. end, mandatory, hyphen);
 
         // If the line doesn't fit anymore, we push the last fitting attempt
         // into the stack and rebuild the line from the attempt's end. The
@@ -665,7 +659,7 @@ fn linebreak_simple<'a>(
             if let Some((last_attempt, last_end)) = last.take() {
                 lines.push(last_attempt);
                 start = last_end;
-                attempt = line(p, loader, start .. end, mandatory, hyphen);
+                attempt = line(p, world, start .. end, mandatory, hyphen);
             }
         }
 
@@ -707,7 +701,7 @@ fn linebreak_simple<'a>(
 /// text.
 fn linebreak_optimized<'a>(
     p: &'a Preparation<'a>,
-    loader: &dyn Loader,
+    world: &dyn World,
     width: Length,
 ) -> Vec<Line<'a>> {
     /// The cost of a line or paragraph layout.
@@ -732,7 +726,7 @@ fn linebreak_optimized<'a>(
     let mut table = vec![Entry {
         pred: 0,
         total: 0.0,
-        line: line(p, loader, 0 .. 0, false, false),
+        line: line(p, world, 0 .. 0, false, false),
     }];
 
     let em = p.styles.get(TextNode::SIZE);
@@ -746,7 +740,7 @@ fn linebreak_optimized<'a>(
         for (i, pred) in table.iter_mut().enumerate().skip(active) {
             // Layout the line.
             let start = pred.line.end;
-            let attempt = line(p, loader, start .. end, mandatory, hyphen);
+            let attempt = line(p, world, start .. end, mandatory, hyphen);
 
             // Determine how much the line's spaces would need to be stretched
             // to make it the desired width.
@@ -920,7 +914,7 @@ impl Breakpoints<'_> {
 /// Create a line which spans the given range.
 fn line<'a>(
     p: &'a Preparation,
-    loader: &dyn Loader,
+    world: &dyn World,
     mut range: Range,
     mandatory: bool,
     hyphen: bool,
@@ -975,9 +969,9 @@ fn line<'a>(
         if hyphen || start + shaped.text.len() > range.end {
             if hyphen || start < range.end || before.is_empty() {
                 let shifted = start - base .. range.end - base;
-                let mut reshaped = shaped.reshape(loader, shifted);
+                let mut reshaped = shaped.reshape(world, shifted);
                 if hyphen || shy {
-                    reshaped.push_hyphen(loader);
+                    reshaped.push_hyphen(world);
                 }
                 width += reshaped.width;
                 last = Some(Item::Text(reshaped));
@@ -998,7 +992,7 @@ fn line<'a>(
         if range.start + shaped.text.len() > end {
             if range.start < end {
                 let shifted = range.start - base .. end - base;
-                let reshaped = shaped.reshape(loader, shifted);
+                let reshaped = shaped.reshape(world, shifted);
                 width += reshaped.width;
                 first = Some(Item::Text(reshaped));
             }
@@ -1028,7 +1022,7 @@ fn line<'a>(
 /// Combine layouted lines into one frame per region.
 fn stack(
     p: &Preparation,
-    ctx: &mut Context,
+    world: &dyn World,
     lines: &[Line],
     regions: &Regions,
 ) -> TypResult<Vec<Frame>> {
@@ -1048,7 +1042,7 @@ fn stack(
 
     // Stack the lines into one frame per region.
     for line in lines {
-        let frame = commit(p, ctx, line, &regions, width)?;
+        let frame = commit(p, world, line, &regions, width)?;
         let height = frame.size().y;
 
         while !regions.first.y.fits(height) && !regions.in_last() {
@@ -1078,7 +1072,7 @@ fn stack(
 /// Commit to a line and build its frame.
 fn commit(
     p: &Preparation,
-    ctx: &mut Context,
+    world: &dyn World,
     line: &Line,
     regions: &Regions,
     width: Length,
@@ -1149,7 +1143,7 @@ fn commit(
                 offset += v.share(fr, remaining);
             }
             Item::Text(shaped) => {
-                let frame = shaped.build(ctx.loader.as_ref(), justification);
+                let frame = shaped.build(world, justification);
                 push(&mut offset, frame);
             }
             Item::Frame(frame) => {
@@ -1160,7 +1154,7 @@ fn commit(
                 let fill = Fraction::one().share(fr, remaining);
                 let size = Size::new(fill, regions.base.y);
                 let pod = Regions::one(size, regions.base, Spec::new(false, false));
-                let frame = node.layout(ctx, &pod, *styles)?.remove(0);
+                let frame = node.layout(world, &pod, *styles)?.remove(0);
                 let width = frame.width();
                 let count = (fill / width).floor();
                 let remaining = fill % width;
diff --git a/src/library/text/raw.rs b/src/library/text/raw.rs
index a2a57fa1..c729fa40 100644
--- a/src/library/text/raw.rs
+++ b/src/library/text/raw.rs
@@ -35,7 +35,7 @@ impl RawNode {
     #[property(resolve, shorthand(around))]
     pub const BELOW: Option<BlockSpacing> = Some(Ratio::one().into());
 
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::show(Self {
             text: args.expect("text")?,
             block: args.named("block")?.unwrap_or(false),
@@ -59,7 +59,7 @@ impl Show for RawNode {
         }
     }
 
-    fn realize(&self, _: &mut Context, styles: StyleChain) -> TypResult<Content> {
+    fn realize(&self, _: &dyn World, styles: StyleChain) -> TypResult<Content> {
         let lang = styles.get(Self::LANG).as_ref().map(|s| s.to_lowercase());
         let foreground = THEME
             .settings
@@ -111,7 +111,7 @@ impl Show for RawNode {
 
     fn finalize(
         &self,
-        _: &mut Context,
+        _: &dyn World,
         styles: StyleChain,
         mut realized: Content,
     ) -> TypResult<Content> {
diff --git a/src/library/text/repeat.rs b/src/library/text/repeat.rs
index aca281fc..c2a0de70 100644
--- a/src/library/text/repeat.rs
+++ b/src/library/text/repeat.rs
@@ -6,7 +6,7 @@ pub struct RepeatNode(pub LayoutNode);
 
 #[node]
 impl RepeatNode {
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::inline(Self(args.expect("body")?)))
     }
 }
@@ -14,11 +14,11 @@ impl RepeatNode {
 impl Layout for RepeatNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
         // The actual repeating happens directly in the paragraph.
-        self.0.layout(ctx, regions, styles)
+        self.0.layout(world, regions, styles)
     }
 }
diff --git a/src/library/text/shaping.rs b/src/library/text/shaping.rs
index 3d905c99..6e505702 100644
--- a/src/library/text/shaping.rs
+++ b/src/library/text/shaping.rs
@@ -80,8 +80,8 @@ impl<'a> ShapedText<'a> {
     ///
     /// The `justification` defines how much extra advance width each
     /// [justifiable glyph](ShapedGlyph::is_justifiable) will get.
-    pub fn build(&self, loader: &dyn Loader, justification: Length) -> Frame {
-        let (top, bottom) = self.measure(loader);
+    pub fn build(&self, world: &dyn World, justification: Length) -> Frame {
+        let (top, bottom) = self.measure(world);
         let size = Size::new(self.width, top + bottom);
 
         let mut offset = Length::zero();
@@ -144,7 +144,7 @@ impl<'a> ShapedText<'a> {
     }
 
     /// Measure the top and bottom extent of this text.
-    fn measure(&self, loader: &dyn Loader) -> (Length, Length) {
+    fn measure(&self, world: &dyn World) -> (Length, Length) {
         let mut top = Length::zero();
         let mut bottom = Length::zero();
 
@@ -162,10 +162,10 @@ impl<'a> ShapedText<'a> {
             // When there are no glyphs, we just use the vertical metrics of the
             // first available font.
             for family in families(self.styles) {
-                if let Some(font) = loader
+                if let Some(font) = world
                     .book()
                     .select(family, self.variant)
-                    .and_then(|id| loader.font(id).ok())
+                    .and_then(|id| world.font(id).ok())
                 {
                     expand(&font);
                     break;
@@ -199,7 +199,7 @@ impl<'a> ShapedText<'a> {
     /// shaping process if possible.
     pub fn reshape(
         &'a self,
-        loader: &dyn Loader,
+        world: &dyn World,
         text_range: Range<usize>,
     ) -> ShapedText<'a> {
         if let Some(glyphs) = self.slice_safe_to_break(text_range.clone()) {
@@ -213,17 +213,17 @@ impl<'a> ShapedText<'a> {
                 glyphs: Cow::Borrowed(glyphs),
             }
         } else {
-            shape(loader, &self.text[text_range], self.styles, self.dir)
+            shape(world, &self.text[text_range], self.styles, self.dir)
         }
     }
 
     /// Push a hyphen to end of the text.
-    pub fn push_hyphen(&mut self, loader: &dyn Loader) {
+    pub fn push_hyphen(&mut self, world: &dyn World) {
         families(self.styles).find_map(|family| {
-            let font = loader
+            let font = world
                 .book()
                 .select(family, self.variant)
-                .and_then(|id| loader.font(id).ok())?;
+                .and_then(|id| world.font(id).ok())?;
             let ttf = font.ttf();
             let glyph_id = ttf.glyph_index('-')?;
             let x_advance = font.to_em(ttf.glyph_hor_advance(glyph_id)?);
@@ -306,7 +306,7 @@ impl Debug for ShapedText<'_> {
 
 /// Holds shaping results and metadata common to all shaped segments.
 struct ShapingContext<'a> {
-    loader: &'a dyn Loader,
+    world: &'a dyn World,
     glyphs: Vec<ShapedGlyph>,
     used: Vec<Font>,
     styles: StyleChain<'a>,
@@ -319,7 +319,7 @@ struct ShapingContext<'a> {
 
 /// Shape text into [`ShapedText`].
 pub fn shape<'a>(
-    loader: &dyn Loader,
+    world: &dyn World,
     text: &'a str,
     styles: StyleChain<'a>,
     dir: Dir,
@@ -327,7 +327,7 @@ pub fn shape<'a>(
     let size = styles.get(TextNode::SIZE);
 
     let mut ctx = ShapingContext {
-        loader,
+        world,
         size,
         glyphs: vec![],
         used: vec![],
@@ -368,10 +368,10 @@ fn shape_segment<'a>(
     }
 
     // Find the next available family.
-    let book = ctx.loader.book();
+    let book = ctx.world.book();
     let mut selection = families.find_map(|family| {
         book.select(family, ctx.variant)
-            .and_then(|id| ctx.loader.font(id).ok())
+            .and_then(|id| ctx.world.font(id).ok())
             .filter(|font| !ctx.used.contains(font))
     });
 
@@ -380,7 +380,7 @@ fn shape_segment<'a>(
         let first = ctx.used.first().map(Font::info);
         selection = book
             .select_fallback(first, ctx.variant, text)
-            .and_then(|id| ctx.loader.font(id).ok())
+            .and_then(|id| ctx.world.font(id).ok())
             .filter(|font| !ctx.used.contains(font));
     }
 
diff --git a/src/library/text/shift.rs b/src/library/text/shift.rs
index 75b2a579..5da36da1 100644
--- a/src/library/text/shift.rs
+++ b/src/library/text/shift.rs
@@ -28,7 +28,7 @@ impl<const S: ScriptKind> ShiftNode<S> {
     /// The font size for synthetic sub- and superscripts.
     pub const SIZE: TextSize = TextSize(Em::new(0.6).into());
 
-    fn construct(_: &mut Machine, args: &mut Args) -> TypResult<Content> {
+    fn construct(_: &mut Vm, args: &mut Args) -> TypResult<Content> {
         Ok(Content::show(Self(args.expect("body")?)))
     }
 }
@@ -42,11 +42,11 @@ impl<const S: ScriptKind> Show for ShiftNode<S> {
         dict! { "body" => Value::Content(self.0.clone()) }
     }
 
-    fn realize(&self, ctx: &mut Context, styles: StyleChain) -> TypResult<Content> {
+    fn realize(&self, world: &dyn World, styles: StyleChain) -> TypResult<Content> {
         let mut transformed = None;
         if styles.get(Self::TYPOGRAPHIC) {
             if let Some(text) = search_text(&self.0, S) {
-                if is_shapable(ctx.loader.as_ref(), &text, styles) {
+                if is_shapable(world, &text, styles) {
                     transformed = Some(Content::Text(text));
                 }
             }
@@ -91,12 +91,12 @@ fn search_text(content: &Content, mode: ScriptKind) -> Option<EcoString> {
 
 /// Checks whether the first retrievable family contains all code points of the
 /// given string.
-fn is_shapable(loader: &dyn Loader, text: &str, styles: StyleChain) -> bool {
-    let book = loader.book();
+fn is_shapable(world: &dyn World, text: &str, styles: StyleChain) -> bool {
     for family in styles.get(TextNode::FAMILY).iter() {
-        if let Some(font) = book
+        if let Some(font) = world
+            .book()
             .select(family.as_str(), variant(styles))
-            .and_then(|id| loader.font(id).ok())
+            .and_then(|id| world.font(id).ok())
         {
             return text.chars().all(|c| font.ttf().glyph_index(c).is_some());
         }
diff --git a/src/library/utility/color.rs b/src/library/utility/color.rs
index 7c6ed873..a7d55d1c 100644
--- a/src/library/utility/color.rs
+++ b/src/library/utility/color.rs
@@ -3,13 +3,13 @@ use std::str::FromStr;
 use crate::library::prelude::*;
 
 /// Create a grayscale color.
-pub fn luma(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn luma(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     let Component(luma) = args.expect("gray component")?;
     Ok(Value::Color(LumaColor::new(luma).into()))
 }
 
 /// Create an RGB(A) color.
-pub fn rgb(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn rgb(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     Ok(Value::Color(
         if let Some(string) = args.find::<Spanned<EcoString>>()? {
             match RgbaColor::from_str(&string.v) {
@@ -27,7 +27,7 @@ pub fn rgb(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
 }
 
 /// Create a CMYK color.
-pub fn cmyk(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn cmyk(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     let RatioComponent(c) = args.expect("cyan component")?;
     let RatioComponent(m) = args.expect("magenta component")?;
     let RatioComponent(y) = args.expect("yellow component")?;
diff --git a/src/library/utility/data.rs b/src/library/utility/data.rs
index f9e970dc..59f3d351 100644
--- a/src/library/utility/data.rs
+++ b/src/library/utility/data.rs
@@ -1,13 +1,13 @@
 use crate::library::prelude::*;
 
 /// Read structured data from a CSV file.
-pub fn csv(vm: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn csv(vm: &mut Vm, args: &mut Args) -> TypResult<Value> {
     let Spanned { v: path, span } =
         args.expect::<Spanned<EcoString>>("path to csv file")?;
 
     let path = vm.locate(&path).at(span)?;
     let try_load = || -> io::Result<Value> {
-        let data = vm.ctx.loader.file(&path)?;
+        let data = vm.world.file(&path)?;
 
         let mut builder = csv::ReaderBuilder::new();
         builder.has_headers(false);
diff --git a/src/library/utility/math.rs b/src/library/utility/math.rs
index f68cc1bf..47648282 100644
--- a/src/library/utility/math.rs
+++ b/src/library/utility/math.rs
@@ -3,7 +3,7 @@ use std::cmp::Ordering;
 use crate::library::prelude::*;
 
 /// Convert a value to an integer.
-pub fn int(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn int(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     let Spanned { v, span } = args.expect("value")?;
     Ok(Value::Int(match v {
         Value::Bool(v) => v as i64,
@@ -18,7 +18,7 @@ pub fn int(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
 }
 
 /// Convert a value to a float.
-pub fn float(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn float(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     let Spanned { v, span } = args.expect("value")?;
     Ok(Value::Float(match v {
         Value::Int(v) => v as f64,
@@ -32,7 +32,7 @@ pub fn float(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
 }
 
 /// The absolute value of a numeric value.
-pub fn abs(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn abs(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     let Spanned { v, span } = args.expect("numeric value")?;
     Ok(match v {
         Value::Int(v) => Value::Int(v.abs()),
@@ -48,12 +48,12 @@ pub fn abs(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
 }
 
 /// The minimum of a sequence of values.
-pub fn min(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn min(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     minmax(args, Ordering::Less)
 }
 
 /// The maximum of a sequence of values.
-pub fn max(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn max(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     minmax(args, Ordering::Greater)
 }
 
@@ -79,17 +79,17 @@ fn minmax(args: &mut Args, goal: Ordering) -> TypResult<Value> {
 }
 
 /// Whether an integer is even.
-pub fn even(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn even(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     Ok(Value::Bool(args.expect::<i64>("integer")? % 2 == 0))
 }
 
 /// Whether an integer is odd.
-pub fn odd(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn odd(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     Ok(Value::Bool(args.expect::<i64>("integer")? % 2 != 0))
 }
 
 /// The modulo of two numbers.
-pub fn mod_(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn mod_(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     let Spanned { v: v1, span: span1 } = args.expect("integer or float")?;
     let Spanned { v: v2, span: span2 } = args.expect("integer or float")?;
 
@@ -119,7 +119,7 @@ pub fn mod_(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
 }
 
 /// Create a sequence of numbers.
-pub fn range(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn range(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     let first = args.expect::<i64>("end")?;
     let (start, end) = match args.eat::<i64>()? {
         Some(second) => (first, second),
diff --git a/src/library/utility/mod.rs b/src/library/utility/mod.rs
index bc7c6f25..40a107ba 100644
--- a/src/library/utility/mod.rs
+++ b/src/library/utility/mod.rs
@@ -10,17 +10,17 @@ pub use data::*;
 pub use math::*;
 pub use string::*;
 
-use crate::eval::{Eval, Machine, Scopes};
+use crate::eval::{Eval, Scopes, Vm};
 use crate::library::prelude::*;
 use crate::source::Source;
 
 /// The name of a value's type.
-pub fn type_(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn type_(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     Ok(args.expect::<Value>("value")?.type_name().into())
 }
 
 /// Ensure that a condition is fulfilled.
-pub fn assert(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn assert(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     let Spanned { v, span } = args.expect::<Spanned<bool>>("condition")?;
     if !v {
         bail!(span, "assertion failed");
@@ -29,19 +29,18 @@ pub fn assert(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
 }
 
 /// Evaluate a string as Typst markup.
-pub fn eval(vm: &mut Machine, args: &mut Args) -> TypResult<Value> {
-    let Spanned { v: src, span } = args.expect::<Spanned<String>>("source")?;
+pub fn eval(vm: &mut Vm, args: &mut Args) -> TypResult<Value> {
+    let Spanned { v: text, span } = args.expect::<Spanned<String>>("source")?;
 
     // Parse the source and set a synthetic span for all nodes.
-    let source = Source::synthesized(src, span);
+    let source = Source::synthesized(text, span);
     let ast = source.ast()?;
 
     // Evaluate the source.
-    let std = vm.ctx.config.std.clone();
-    let scopes = Scopes::new(Some(&std));
-    let mut sub = Machine::new(vm.ctx, vec![], scopes);
+    let std = &vm.world.config().std;
+    let scopes = Scopes::new(Some(std));
+    let mut sub = Vm::new(vm.world, vec![], scopes);
     let result = ast.eval(&mut sub);
-    assert!(vm.deps.is_empty());
 
     // Handle control flow.
     if let Some(flow) = sub.flow {
diff --git a/src/library/utility/string.rs b/src/library/utility/string.rs
index 972b44d7..d825d84b 100644
--- a/src/library/utility/string.rs
+++ b/src/library/utility/string.rs
@@ -2,12 +2,12 @@ use crate::eval::Regex;
 use crate::library::prelude::*;
 
 /// The string representation of a value.
-pub fn repr(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn repr(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     Ok(args.expect::<Value>("value")?.repr().into())
 }
 
 /// Convert a value to a string.
-pub fn str(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn str(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     let Spanned { v, span } = args.expect("value")?;
     Ok(Value::Str(match v {
         Value::Int(v) => format_str!("{}", v),
@@ -18,29 +18,29 @@ pub fn str(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
 }
 
 /// Create blind text.
-pub fn lorem(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn lorem(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     let words: usize = args.expect("number of words")?;
     Ok(Value::Str(lipsum::lipsum(words).into()))
 }
 
 /// Create a regular expression.
-pub fn regex(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn regex(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     let Spanned { v, span } = args.expect::<Spanned<EcoString>>("regular expression")?;
     Ok(Regex::new(&v).at(span)?.into())
 }
 
 /// Converts an integer into one or multiple letters.
-pub fn letter(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn letter(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     numbered(Numbering::Letter, args)
 }
 
 /// Converts an integer into a roman numeral.
-pub fn roman(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn roman(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     numbered(Numbering::Roman, args)
 }
 
 /// Convert a number into a symbol.
-pub fn symbol(_: &mut Machine, args: &mut Args) -> TypResult<Value> {
+pub fn symbol(_: &mut Vm, args: &mut Args) -> TypResult<Value> {
     numbered(Numbering::Symbol, args)
 }
 
diff --git a/src/loading.rs b/src/loading.rs
deleted file mode 100644
index 9a32d025..00000000
--- a/src/loading.rs
+++ /dev/null
@@ -1,239 +0,0 @@
-//! Resource loading.
-
-use std::fmt::{self, Debug, Formatter};
-use std::io;
-use std::ops::Deref;
-use std::path::Path;
-use std::sync::Arc;
-
-use crate::font::{Font, FontBook};
-use crate::util::Prehashed;
-
-/// A hash that identifies a file.
-///
-/// Such a hash can be [resolved](Loader::resolve) from a path.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
-pub struct FileHash(pub u64);
-
-/// Loads resources from a local or remote source.
-pub trait Loader {
-    /// Metadata about all known fonts.
-    fn book(&self) -> &FontBook;
-
-    /// Access the font with the given id.
-    fn font(&self, id: usize) -> io::Result<Font>;
-
-    /// Resolve a hash that is the same for this and all other paths pointing to
-    /// the same file.
-    fn resolve(&self, path: &Path) -> io::Result<FileHash>;
-
-    /// Load a file from a path.
-    fn file(&self, path: &Path) -> io::Result<Buffer>;
-}
-
-/// A shared buffer that is cheap to clone.
-#[derive(Clone, Hash, Eq, PartialEq)]
-pub struct Buffer(Prehashed<Arc<Vec<u8>>>);
-
-impl Buffer {
-    /// Return a view into the buffer.
-    pub fn as_slice(&self) -> &[u8] {
-        self
-    }
-
-    /// Return a copy of the buffer as a vector.
-    pub fn to_vec(&self) -> Vec<u8> {
-        self.0.to_vec()
-    }
-}
-
-impl From<&[u8]> for Buffer {
-    fn from(slice: &[u8]) -> Self {
-        Self(Prehashed::new(Arc::new(slice.to_vec())))
-    }
-}
-
-impl From<Vec<u8>> for Buffer {
-    fn from(vec: Vec<u8>) -> Self {
-        Self(Prehashed::new(Arc::new(vec)))
-    }
-}
-
-impl From<Arc<Vec<u8>>> for Buffer {
-    fn from(arc: Arc<Vec<u8>>) -> Self {
-        Self(Prehashed::new(arc))
-    }
-}
-
-impl Deref for Buffer {
-    type Target = [u8];
-
-    fn deref(&self) -> &Self::Target {
-        &self.0
-    }
-}
-
-impl AsRef<[u8]> for Buffer {
-    fn as_ref(&self) -> &[u8] {
-        self
-    }
-}
-
-impl Debug for Buffer {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        f.pad("Buffer(..)")
-    }
-}
-
-#[cfg(feature = "fs")]
-pub use fs::*;
-
-#[cfg(feature = "fs")]
-mod fs {
-    use std::fs::{self, File};
-    use std::io;
-    use std::path::{Path, PathBuf};
-
-    use memmap2::Mmap;
-    use same_file::Handle;
-    use walkdir::WalkDir;
-
-    use super::{Buffer, FileHash, Loader};
-    use crate::font::{Font, FontBook, FontInfo};
-
-    /// Loads fonts and files from the local file system.
-    ///
-    /// _This is only available when the `system` feature is enabled._
-    pub struct FsLoader {
-        book: FontBook,
-        paths: Vec<(PathBuf, u32)>,
-    }
-
-    impl FsLoader {
-        /// Create a new system loader.
-        pub fn new() -> Self {
-            Self { book: FontBook::new(), paths: vec![] }
-        }
-
-        /// Builder-style variant of [`search_path`](Self::search_path).
-        pub fn with_path(mut self, dir: impl AsRef<Path>) -> Self {
-            self.search_path(dir);
-            self
-        }
-
-        /// Search for all fonts at a path.
-        ///
-        /// If the path is a directory, all contained fonts will be searched for
-        /// recursively.
-        pub fn search_path(&mut self, path: impl AsRef<Path>) {
-            let walk = WalkDir::new(path)
-                .follow_links(true)
-                .sort_by(|a, b| a.file_name().cmp(b.file_name()))
-                .into_iter()
-                .filter_map(|e| e.ok());
-
-            for entry in walk {
-                let path = entry.path();
-                if let Some(ext) = path.extension().and_then(|s| s.to_str()) {
-                    if matches!(
-                        ext,
-                        "ttf" | "otf" | "TTF" | "OTF" | "ttc" | "otc" | "TTC" | "OTC",
-                    ) {
-                        self.search_file(path);
-                    }
-                }
-            }
-        }
-
-        /// Index the fonts in the file at the given path.
-        ///
-        /// The file may form a font collection and contain multiple fonts,
-        /// which will then all be indexed.
-        fn search_file(&mut self, path: impl AsRef<Path>) {
-            let path = path.as_ref();
-            let path = path.strip_prefix(".").unwrap_or(path);
-            if let Ok(file) = File::open(path) {
-                if let Ok(mmap) = unsafe { Mmap::map(&file) } {
-                    for (i, info) in FontInfo::from_data(&mmap).enumerate() {
-                        self.book.push(info);
-                        self.paths.push((path.into(), i as u32));
-                    }
-                }
-            }
-        }
-
-        /// Builder-style variant of [`search_system`](Self::search_system).
-        pub fn with_system(mut self) -> Self {
-            self.search_system();
-            self
-        }
-
-        /// Search for fonts in the operating system's font directories.
-        pub fn search_system(&mut self) {
-            self.search_system_impl();
-        }
-
-        #[cfg(all(unix, not(target_os = "macos")))]
-        fn search_system_impl(&mut self) {
-            self.search_path("/usr/share/fonts");
-            self.search_path("/usr/local/share/fonts");
-
-            if let Some(dir) = dirs::font_dir() {
-                self.search_path(dir);
-            }
-        }
-
-        #[cfg(target_os = "macos")]
-        fn search_system_impl(&mut self) {
-            self.search_path("/Library/Fonts");
-            self.search_path("/Network/Library/Fonts");
-            self.search_path("/System/Library/Fonts");
-
-            if let Some(dir) = dirs::font_dir() {
-                self.search_path(dir);
-            }
-        }
-
-        #[cfg(windows)]
-        fn search_system_impl(&mut self) {
-            let windir =
-                std::env::var("WINDIR").unwrap_or_else(|_| "C:\\Windows".to_string());
-
-            self.search_path(Path::new(&windir).join("Fonts"));
-
-            if let Some(roaming) = dirs::config_dir() {
-                self.search_path(roaming.join("Microsoft\\Windows\\Fonts"));
-            }
-
-            if let Some(local) = dirs::cache_dir() {
-                self.search_path(local.join("Microsoft\\Windows\\Fonts"));
-            }
-        }
-    }
-
-    impl Loader for FsLoader {
-        fn book(&self) -> &FontBook {
-            &self.book
-        }
-
-        fn font(&self, id: usize) -> io::Result<Font> {
-            let (path, index) = &self.paths[id];
-            let data = self.file(path)?;
-            Font::new(data, *index).ok_or_else(|| io::ErrorKind::InvalidData.into())
-        }
-
-        fn resolve(&self, path: &Path) -> io::Result<FileHash> {
-            let meta = fs::metadata(path)?;
-            if meta.is_file() {
-                let handle = Handle::from_path(path)?;
-                Ok(FileHash(fxhash::hash64(&handle)))
-            } else {
-                Err(io::ErrorKind::NotFound.into())
-            }
-        }
-
-        fn file(&self, path: &Path) -> io::Result<Buffer> {
-            Ok(fs::read(path)?.into())
-        }
-    }
-}
diff --git a/src/main.rs b/src/main.rs
index 8d6a669a..e5af0d8b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,22 +1,32 @@
-use std::fs;
+use std::cell::RefCell;
+use std::collections::{hash_map::Entry, HashMap};
+use std::fs::{self, File};
+use std::hash::Hash;
 use std::io::{self, Write};
 use std::path::{Path, PathBuf};
 use std::process;
-use std::sync::Arc;
 
 use codespan_reporting::diagnostic::{Diagnostic, Label};
 use codespan_reporting::term::{self, termcolor};
+use elsa::FrozenVec;
+use memmap2::Mmap;
+use once_cell::unsync::OnceCell;
 use pico_args::Arguments;
-use same_file::is_same_file;
+use same_file::{is_same_file, Handle};
+use siphasher::sip128::{Hasher128, SipHasher};
 use termcolor::{ColorChoice, StandardStream, WriteColor};
+use walkdir::WalkDir;
 
-use typst::diag::{Error, StrResult};
-use typst::font::FontVariant;
+use typst::diag::{failed_to_load, Error, StrResult};
+use typst::font::{Font, FontBook, FontInfo, FontVariant};
 use typst::library::text::THEME;
-use typst::loading::{FsLoader, Loader};
 use typst::parse::TokenMode;
-use typst::source::SourceStore;
-use typst::{Config, Context};
+use typst::source::{Source, SourceId};
+use typst::util::Buffer;
+use typst::{Config, World};
+
+type CodespanResult<T> = Result<T, CodespanError>;
+type CodespanError = codespan_reporting::files::Error;
 
 /// What to do.
 enum Command {
@@ -191,25 +201,20 @@ fn dispatch(command: Command) -> StrResult<()> {
 
 /// Execute a typesetting command.
 fn typeset(command: TypesetCommand) -> StrResult<()> {
-    let mut config = Config::builder();
+    let mut world = SystemWorld::new();
     if let Some(root) = &command.root {
-        config.root(root);
+        world.config.root = root.clone();
     } else if let Some(dir) = command.input.parent() {
-        config.root(dir);
+        world.config.root = dir.into();
     }
 
-    // Create a loader for fonts and files.
-    let loader = FsLoader::new().with_system();
-
-    // Create the context which holds loaded source files, fonts, images and
-    // cached artifacts.
-    let mut ctx = Context::new(Arc::new(loader), config.build());
-
-    // Load the source file.
-    let id = ctx.sources.load(&command.input)?;
+    // Create the world that serves sources, fonts and files.
+    let id = world
+        .resolve(&command.input)
+        .map_err(|err| failed_to_load("source file", &command.input, err))?;
 
     // Typeset.
-    match typst::typeset(&mut ctx, id) {
+    match typst::typeset(&world, id) {
         // Export the PDF.
         Ok(frames) => {
             let buffer = typst::export::pdf(&frames);
@@ -218,7 +223,7 @@ fn typeset(command: TypesetCommand) -> StrResult<()> {
 
         // Print diagnostics.
         Err(errors) => {
-            print_diagnostics(&ctx.sources, *errors)
+            print_diagnostics(&world, *errors)
                 .map_err(|_| "failed to print diagnostics")?;
         }
     }
@@ -228,7 +233,7 @@ fn typeset(command: TypesetCommand) -> StrResult<()> {
 
 /// Print diagnostic messages to the terminal.
 fn print_diagnostics(
-    sources: &SourceStore,
+    world: &SystemWorld,
     errors: Vec<Error>,
 ) -> Result<(), codespan_reporting::files::Error> {
     let mut w = StandardStream::stderr(ColorChoice::Always);
@@ -236,21 +241,24 @@ fn print_diagnostics(
 
     for error in errors {
         // The main diagnostic.
-        let range = sources.range(error.span);
+        let range = world.source(error.span.source()).range(error.span);
         let diag = Diagnostic::error()
             .with_message(error.message)
             .with_labels(vec![Label::primary(error.span.source(), range)]);
 
-        term::emit(&mut w, &config, sources, &diag)?;
+        term::emit(&mut w, &config, world, &diag)?;
 
         // Stacktrace-like helper diagnostics.
         for point in error.trace {
             let message = point.v.to_string();
             let help = Diagnostic::help().with_message(message).with_labels(vec![
-                Label::primary(point.span.source(), sources.range(point.span)),
+                Label::primary(
+                    point.span.source(),
+                    world.source(point.span.source()).range(point.span),
+                ),
             ]);
 
-            term::emit(&mut w, &config, sources, &help)?;
+            term::emit(&mut w, &config, world, &help)?;
         }
     }
 
@@ -259,8 +267,8 @@ fn print_diagnostics(
 
 /// Execute a highlighting command.
 fn highlight(command: HighlightCommand) -> StrResult<()> {
-    let input = std::fs::read_to_string(&command.input)
-        .map_err(|_| "failed to load source file")?;
+    let input =
+        fs::read_to_string(&command.input).map_err(|_| "failed to load source file")?;
 
     let html = typst::syntax::highlight_html(&input, TokenMode::Markup, &THEME);
     fs::write(&command.output, html).map_err(|_| "failed to write HTML file")?;
@@ -270,8 +278,8 @@ fn highlight(command: HighlightCommand) -> StrResult<()> {
 
 /// Execute a font listing command.
 fn fonts(command: FontsCommand) -> StrResult<()> {
-    let loader = FsLoader::new().with_system();
-    for (name, infos) in loader.book().families() {
+    let world = SystemWorld::new();
+    for (name, infos) in world.book().families() {
         println!("{name}");
         if command.variants {
             for info in infos {
@@ -283,3 +291,234 @@ fn fonts(command: FontsCommand) -> StrResult<()> {
 
     Ok(())
 }
+
+/// A world that provides access to the operating system.
+struct SystemWorld {
+    config: Config,
+    sources: FrozenVec<Box<Source>>,
+    nav: RefCell<HashMap<PathHash, SourceId>>,
+    book: FontBook,
+    fonts: Vec<FontSlot>,
+    files: RefCell<HashMap<PathHash, Buffer>>,
+}
+
+struct FontSlot {
+    path: PathBuf,
+    index: u32,
+    font: OnceCell<Option<Font>>,
+}
+
+impl SystemWorld {
+    fn new() -> Self {
+        let mut world = Self {
+            config: Config::default(),
+            book: FontBook::new(),
+            sources: FrozenVec::new(),
+            nav: RefCell::new(HashMap::new()),
+            fonts: vec![],
+            files: RefCell::new(HashMap::new()),
+        };
+        world.search_system();
+        world
+    }
+}
+
+impl World for SystemWorld {
+    fn config(&self) -> &Config {
+        &self.config
+    }
+
+    fn resolve(&self, path: &Path) -> io::Result<SourceId> {
+        let hash = PathHash::new(path)?;
+        if let Some(&id) = self.nav.borrow().get(&hash) {
+            return Ok(id);
+        }
+
+        let data = fs::read(path)?;
+        let text = String::from_utf8(data).map_err(|_| {
+            io::Error::new(io::ErrorKind::InvalidData, "file is not valid utf-8")
+        })?;
+
+        let id = SourceId::from_raw(self.sources.len() as u16);
+        let source = Source::new(id, path, text);
+        self.sources.push(Box::new(source));
+        self.nav.borrow_mut().insert(hash, id);
+
+        Ok(id)
+    }
+
+    fn source(&self, id: SourceId) -> &Source {
+        &self.sources[id.into_raw() as usize]
+    }
+
+    fn book(&self) -> &FontBook {
+        &self.book
+    }
+
+    fn font(&self, id: usize) -> io::Result<Font> {
+        let slot = &self.fonts[id];
+        slot.font
+            .get_or_init(|| {
+                let data = self.file(&slot.path).ok()?;
+                Font::new(data, slot.index)
+            })
+            .clone()
+            .ok_or_else(|| io::ErrorKind::InvalidData.into())
+    }
+
+    fn file(&self, path: &Path) -> io::Result<Buffer> {
+        let hash = PathHash::new(path)?;
+        Ok(match self.files.borrow_mut().entry(hash) {
+            Entry::Occupied(entry) => entry.get().clone(),
+            Entry::Vacant(entry) => entry.insert(fs::read(path)?.into()).clone(),
+        })
+    }
+}
+
+/// A hash that is the same for all paths pointing to the same file.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+struct PathHash(u128);
+
+impl PathHash {
+    fn new(path: &Path) -> io::Result<Self> {
+        let file = File::open(path)?;
+        if file.metadata()?.is_file() {
+            let handle = Handle::from_file(file)?;
+            let mut state = SipHasher::new();
+            handle.hash(&mut state);
+            Ok(Self(state.finish128().as_u128()))
+        } else {
+            Err(io::ErrorKind::NotFound.into())
+        }
+    }
+}
+
+impl SystemWorld {
+    /// Search for fonts in the linux system font directories.
+    #[cfg(all(unix, not(target_os = "macos")))]
+    fn search_system(&mut self) {
+        self.search_dir("/usr/share/fonts");
+        self.search_dir("/usr/local/share/fonts");
+
+        if let Some(dir) = dirs::font_dir() {
+            self.search_dir(dir);
+        }
+    }
+
+    /// Search for fonts in the macOS system font directories.
+    #[cfg(target_os = "macos")]
+    fn search_system(&mut self) {
+        self.search_dir("/Library/Fonts");
+        self.search_dir("/Network/Library/Fonts");
+        self.search_dir("/System/Library/Fonts");
+
+        if let Some(dir) = dirs::font_dir() {
+            self.search_dir(dir);
+        }
+    }
+
+    /// Search for fonts in the Windows system font directories.
+    #[cfg(windows)]
+    fn search_system(&mut self) {
+        let windir =
+            std::env::var("WINDIR").unwrap_or_else(|_| "C:\\Windows".to_string());
+
+        self.search_dir(Path::new(&windir).join("Fonts"));
+
+        if let Some(roaming) = dirs::config_dir() {
+            self.search_dir(roaming.join("Microsoft\\Windows\\Fonts"));
+        }
+
+        if let Some(local) = dirs::cache_dir() {
+            self.search_dir(local.join("Microsoft\\Windows\\Fonts"));
+        }
+    }
+
+    /// Search for all fonts in a directory.
+    /// recursively.
+    fn search_dir(&mut self, path: impl AsRef<Path>) {
+        for entry in WalkDir::new(path)
+            .follow_links(true)
+            .sort_by(|a, b| a.file_name().cmp(b.file_name()))
+            .into_iter()
+            .filter_map(|e| e.ok())
+        {
+            let path = entry.path();
+            if matches!(
+                path.extension().and_then(|s| s.to_str()),
+                Some("ttf" | "otf" | "TTF" | "OTF" | "ttc" | "otc" | "TTC" | "OTC"),
+            ) {
+                self.search_file(path);
+            }
+        }
+    }
+
+    /// Index the fonts in the file at the given path.
+    fn search_file(&mut self, path: impl AsRef<Path>) {
+        let path = path.as_ref();
+        if let Ok(file) = File::open(path) {
+            if let Ok(mmap) = unsafe { Mmap::map(&file) } {
+                for (i, info) in FontInfo::from_data(&mmap).enumerate() {
+                    self.book.push(info);
+                    self.fonts.push(FontSlot {
+                        path: path.into(),
+                        index: i as u32,
+                        font: OnceCell::new(),
+                    });
+                }
+            }
+        }
+    }
+}
+
+impl<'a> codespan_reporting::files::Files<'a> for SystemWorld {
+    type FileId = SourceId;
+    type Name = std::path::Display<'a>;
+    type Source = &'a str;
+
+    fn name(&'a self, id: SourceId) -> CodespanResult<Self::Name> {
+        Ok(World::source(self, id).path().display())
+    }
+
+    fn source(&'a self, id: SourceId) -> CodespanResult<Self::Source> {
+        Ok(World::source(self, id).text())
+    }
+
+    fn line_index(&'a self, id: SourceId, given: usize) -> CodespanResult<usize> {
+        let source = World::source(self, id);
+        source
+            .byte_to_line(given)
+            .ok_or_else(|| CodespanError::IndexTooLarge {
+                given,
+                max: source.len_bytes(),
+            })
+    }
+
+    fn line_range(
+        &'a self,
+        id: SourceId,
+        given: usize,
+    ) -> CodespanResult<std::ops::Range<usize>> {
+        let source = World::source(self, id);
+        source
+            .line_to_range(given)
+            .ok_or_else(|| CodespanError::LineTooLarge { given, max: source.len_lines() })
+    }
+
+    fn column_number(
+        &'a self,
+        id: SourceId,
+        _: usize,
+        given: usize,
+    ) -> CodespanResult<usize> {
+        let source = World::source(self, id);
+        source.byte_to_column(given).ok_or_else(|| {
+            let max = source.len_bytes();
+            if given <= max {
+                CodespanError::InvalidCharBoundary { given }
+            } else {
+                CodespanError::IndexTooLarge { given, max }
+            }
+        })
+    }
+}
diff --git a/src/model/content.rs b/src/model/content.rs
index ae86e279..8076eff9 100644
--- a/src/model/content.rs
+++ b/src/model/content.rs
@@ -18,20 +18,20 @@ use crate::library::text::{
     DecoNode, EmphNode, ParChild, ParNode, StrongNode, UNDERLINE,
 };
 use crate::util::EcoString;
+use crate::World;
 
 /// Layout content into a collection of pages.
 ///
 /// Relayouts until all pinned locations are converged.
-pub fn layout(ctx: &mut Context, content: &Content) -> TypResult<Vec<Frame>> {
-    let copy = ctx.config.styles.clone();
-    let styles = StyleChain::with_root(&copy);
+pub fn layout(world: &dyn World, content: &Content) -> TypResult<Vec<Frame>> {
+    let styles = StyleChain::with_root(&world.config().styles);
     let scratch = Scratch::default();
 
-    let mut builder = Builder::new(ctx, &scratch, true);
+    let mut builder = Builder::new(world, &scratch, true);
     builder.accept(content, styles)?;
 
     let (doc, shared) = builder.into_doc(styles)?;
-    doc.layout(ctx, shared)
+    doc.layout(world, shared)
 }
 
 /// Composable representation of styled content.
@@ -232,15 +232,15 @@ impl Content {
 impl Layout for Content {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
         let scratch = Scratch::default();
-        let mut builder = Builder::new(ctx, &scratch, false);
+        let mut builder = Builder::new(world, &scratch, false);
         builder.accept(self, styles)?;
         let (flow, shared) = builder.into_flow(styles)?;
-        flow.layout(ctx, regions, shared)
+        flow.layout(world, regions, shared)
     }
 
     fn pack(self) -> LayoutNode {
@@ -330,9 +330,9 @@ impl Sum for Content {
 }
 
 /// Builds a document or a flow node from content.
-struct Builder<'a, 'ctx> {
+struct Builder<'a, 'w> {
     /// The core context.
-    ctx: &'ctx mut Context,
+    world: &'w dyn World,
     /// Scratch arenas for building.
     scratch: &'a Scratch<'a>,
     /// The current document building state.
@@ -354,10 +354,10 @@ struct Scratch<'a> {
     templates: Arena<Content>,
 }
 
-impl<'a, 'ctx> Builder<'a, 'ctx> {
-    fn new(ctx: &'ctx mut Context, scratch: &'a Scratch<'a>, top: bool) -> Self {
+impl<'a, 'w> Builder<'a, 'w> {
+    fn new(world: &'w dyn World, scratch: &'a Scratch<'a>, top: bool) -> Self {
         Self {
-            ctx,
+            world,
             scratch,
             doc: top.then(|| DocBuilder::default()),
             flow: FlowBuilder::default(),
@@ -388,7 +388,7 @@ impl<'a, 'ctx> Builder<'a, 'ctx> {
         match content {
             Content::Empty => return Ok(()),
             Content::Text(text) => {
-                if let Some(realized) = styles.apply(self.ctx, Target::Text(text))? {
+                if let Some(realized) = styles.apply(self.world, Target::Text(text))? {
                     let stored = self.scratch.templates.alloc(realized);
                     return self.accept(stored, styles);
                 }
@@ -431,7 +431,7 @@ impl<'a, 'ctx> Builder<'a, 'ctx> {
     }
 
     fn show(&mut self, node: &ShowNode, styles: StyleChain<'a>) -> TypResult<()> {
-        if let Some(mut realized) = styles.apply(self.ctx, Target::Node(node))? {
+        if let Some(mut realized) = styles.apply(self.world, Target::Node(node))? {
             let mut map = StyleMap::new();
             let barrier = Barrier::new(node.id());
             map.push(StyleEntry::Barrier(barrier));
diff --git a/src/model/layout.rs b/src/model/layout.rs
index d712a178..911cb4d5 100644
--- a/src/model/layout.rs
+++ b/src/model/layout.rs
@@ -15,7 +15,7 @@ use crate::geom::{
 use crate::library::graphics::MoveNode;
 use crate::library::layout::{AlignNode, PadNode};
 use crate::util::Prehashed;
-use crate::Context;
+use crate::World;
 
 /// A node that can be layouted into a sequence of regions.
 ///
@@ -24,7 +24,7 @@ pub trait Layout: 'static {
     /// Layout this node into the given regions, producing frames.
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>>;
@@ -216,14 +216,14 @@ impl LayoutNode {
 impl Layout for LayoutNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
         let barrier = StyleEntry::Barrier(Barrier::new(self.id()));
         let styles = barrier.chain(&styles);
 
-        let mut frames = self.0.layout(ctx, regions, styles)?;
+        let mut frames = self.0.layout(world, regions, styles)?;
         if let Some(role) = styles.role() {
             for frame in &mut frames {
                 frame.apply_role(role);
@@ -285,7 +285,7 @@ struct EmptyNode;
 impl Layout for EmptyNode {
     fn layout(
         &self,
-        _: &mut Context,
+        _: &dyn World,
         regions: &Regions,
         _: StyleChain,
     ) -> TypResult<Vec<Frame>> {
@@ -307,7 +307,7 @@ struct SizedNode {
 impl Layout for SizedNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
@@ -331,7 +331,7 @@ impl Layout for SizedNode {
         };
 
         // Layout the child.
-        let mut frames = self.child.layout(ctx, &pod, styles)?;
+        let mut frames = self.child.layout(world, &pod, styles)?;
 
         // Ensure frame size matches regions size if expansion is on.
         let frame = &mut frames[0];
@@ -354,11 +354,11 @@ struct FillNode {
 impl Layout for FillNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
-        let mut frames = self.child.layout(ctx, regions, styles)?;
+        let mut frames = self.child.layout(world, regions, styles)?;
         for frame in &mut frames {
             let shape = Geometry::Rect(frame.size()).filled(self.fill);
             frame.prepend(Point::zero(), Element::Shape(shape));
@@ -379,11 +379,11 @@ struct StrokeNode {
 impl Layout for StrokeNode {
     fn layout(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Frame>> {
-        let mut frames = self.child.layout(ctx, regions, styles)?;
+        let mut frames = self.child.layout(world, regions, styles)?;
         for frame in &mut frames {
             let shape = Geometry::Rect(frame.size()).stroked(self.stroke);
             frame.prepend(Point::zero(), Element::Shape(shape));
diff --git a/src/model/recipe.rs b/src/model/recipe.rs
index 6261e704..f5ca2cb9 100644
--- a/src/model/recipe.rs
+++ b/src/model/recipe.rs
@@ -5,7 +5,7 @@ use crate::diag::TypResult;
 use crate::eval::{Args, Func, Regex, Value};
 use crate::library::structure::{EnumNode, ListNode};
 use crate::syntax::Spanned;
-use crate::Context;
+use crate::World;
 
 /// A show rule recipe.
 #[derive(Clone, PartialEq, Hash)]
@@ -29,7 +29,7 @@ impl Recipe {
     /// Try to apply the recipe to the target.
     pub fn apply(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         styles: StyleChain,
         sel: Selector,
         target: Target,
@@ -37,7 +37,7 @@ impl Recipe {
         let content = match (target, &self.pattern) {
             (Target::Node(node), &Pattern::Node(id)) if node.id() == id => {
                 let node = node.unguard(sel);
-                self.call(ctx, || {
+                self.call(world, || {
                     let dict = node.encode(styles);
                     Value::Content(Content::Show(node, Some(dict)))
                 })?
@@ -53,7 +53,7 @@ impl Recipe {
                         result.push(Content::Text(text[cursor .. start].into()));
                     }
 
-                    result.push(self.call(ctx, || Value::Str(mat.as_str().into()))?);
+                    result.push(self.call(world, || Value::Str(mat.as_str().into()))?);
                     cursor = mat.end();
                 }
 
@@ -75,7 +75,7 @@ impl Recipe {
     }
 
     /// Call the recipe function, with the argument if desired.
-    fn call<F>(&self, ctx: &mut Context, arg: F) -> TypResult<Content>
+    fn call<F>(&self, world: &dyn World, arg: F) -> TypResult<Content>
     where
         F: FnOnce() -> Value,
     {
@@ -85,7 +85,7 @@ impl Recipe {
             Args::new(self.func.span, [arg()])
         };
 
-        Ok(self.func.v.call_detached(ctx, args)?.display())
+        Ok(self.func.v.call_detached(world, args)?.display())
     }
 
     /// What kind of structure the property interrupts.
diff --git a/src/model/show.rs b/src/model/show.rs
index ac73cb76..e8d27977 100644
--- a/src/model/show.rs
+++ b/src/model/show.rs
@@ -6,7 +6,7 @@ use super::{Content, NodeId, Selector, StyleChain};
 use crate::diag::TypResult;
 use crate::eval::Dict;
 use crate::util::Prehashed;
-use crate::Context;
+use crate::World;
 
 /// A node that can be realized given some styles.
 pub trait Show: 'static {
@@ -18,7 +18,7 @@ pub trait Show: 'static {
 
     /// The base recipe for this node that is executed if there is no
     /// user-defined show rule.
-    fn realize(&self, ctx: &mut Context, styles: StyleChain) -> TypResult<Content>;
+    fn realize(&self, world: &dyn World, styles: StyleChain) -> TypResult<Content>;
 
     /// Finalize this node given the realization of a base or user recipe. Use
     /// this for effects that should work even in the face of a user-defined
@@ -30,7 +30,7 @@ pub trait Show: 'static {
     #[allow(unused_variables)]
     fn finalize(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         styles: StyleChain,
         realized: Content,
     ) -> TypResult<Content> {
@@ -74,17 +74,17 @@ impl Show for ShowNode {
         self.0.encode(styles)
     }
 
-    fn realize(&self, ctx: &mut Context, styles: StyleChain) -> TypResult<Content> {
-        self.0.realize(ctx, styles)
+    fn realize(&self, world: &dyn World, styles: StyleChain) -> TypResult<Content> {
+        self.0.realize(world, styles)
     }
 
     fn finalize(
         &self,
-        ctx: &mut Context,
+        world: &dyn World,
         styles: StyleChain,
         realized: Content,
     ) -> TypResult<Content> {
-        self.0.finalize(ctx, styles, realized)
+        self.0.finalize(world, styles, realized)
     }
 
     fn pack(self) -> ShowNode {
diff --git a/src/model/styles.rs b/src/model/styles.rs
index eab33402..53ef926c 100644
--- a/src/model/styles.rs
+++ b/src/model/styles.rs
@@ -8,7 +8,7 @@ use crate::diag::TypResult;
 use crate::frame::Role;
 use crate::library::text::{FontFamily, TextNode};
 use crate::util::ReadableTypeId;
-use crate::Context;
+use crate::World;
 
 /// A map of style properties.
 #[derive(Default, Clone, PartialEq, Hash)]
@@ -277,7 +277,7 @@ impl<'a> StyleChain<'a> {
     }
 
     /// Apply show recipes in this style chain to a target.
-    pub fn apply(self, ctx: &mut Context, target: Target) -> TypResult<Option<Content>> {
+    pub fn apply(self, world: &dyn World, target: Target) -> TypResult<Option<Content>> {
         // Find out how many recipes there any and whether any of their patterns
         // match.
         let mut n = 0;
@@ -296,7 +296,9 @@ impl<'a> StyleChain<'a> {
                     let sel = Selector::Nth(n);
                     if self.guarded(sel) {
                         guarded = true;
-                    } else if let Some(content) = recipe.apply(ctx, self, sel, target)? {
+                    } else if let Some(content) =
+                        recipe.apply(world, self, sel, target)?
+                    {
                         realized = Some(content);
                         break;
                     }
@@ -312,7 +314,7 @@ impl<'a> StyleChain<'a> {
                 if self.guarded(sel) {
                     guarded = true;
                 } else {
-                    let content = node.unguard(sel).realize(ctx, self)?;
+                    let content = node.unguard(sel).realize(world, self)?;
                     realized = Some(content.styled_with_entry(StyleEntry::Guard(sel)));
                 }
             }
@@ -320,7 +322,7 @@ impl<'a> StyleChain<'a> {
             // Finalize only if guarding didn't stop any recipe.
             if !guarded {
                 if let Some(content) = realized {
-                    realized = Some(node.finalize(ctx, self, content)?);
+                    realized = Some(node.finalize(world, self, content)?);
                 }
             }
         }
diff --git a/src/parse/incremental.rs b/src/parse/incremental.rs
index 60f780b4..9272dcfc 100644
--- a/src/parse/incremental.rs
+++ b/src/parse/incremental.rs
@@ -15,21 +15,21 @@ use super::{
 /// Returns the range in the new source that was ultimately reparsed.
 pub fn reparse(
     root: &mut SyntaxNode,
-    src: &str,
+    text: &str,
     replaced: Range<usize>,
     replacement_len: usize,
 ) -> Range<usize> {
     if let SyntaxNode::Inner(inner) = root {
-        let change = Change { src, replaced, replacement_len };
+        let change = Change { text, replaced, replacement_len };
         if let Some(range) = try_reparse(&change, Arc::make_mut(inner), 0, true, true) {
             return range;
         }
     }
 
     let id = root.span().source();
-    *root = parse(src);
+    *root = parse(text);
     root.numberize(id, Span::FULL).unwrap();
-    0 .. src.len()
+    0 .. text.len()
 }
 
 /// Try to reparse inside the given node.
@@ -228,27 +228,27 @@ fn replace(
     let newborn_span = superseded_span.start .. newborn_end;
 
     let mut prefix = "";
-    for (i, c) in change.src[.. newborn_span.start].char_indices().rev() {
+    for (i, c) in change.text[.. newborn_span.start].char_indices().rev() {
         if is_newline(c) {
             break;
         }
-        prefix = &change.src[i .. newborn_span.start];
+        prefix = &change.text[i .. newborn_span.start];
     }
 
     let (newborns, terminated, amount) = match mode {
         ReparseMode::Code => reparse_code_block(
             &prefix,
-            &change.src[newborn_span.start ..],
+            &change.text[newborn_span.start ..],
             newborn_span.len(),
         ),
         ReparseMode::Content => reparse_content_block(
             &prefix,
-            &change.src[newborn_span.start ..],
+            &change.text[newborn_span.start ..],
             newborn_span.len(),
         ),
         ReparseMode::MarkupElements { at_start, min_indent } => reparse_markup_elements(
             &prefix,
-            &change.src[newborn_span.start ..],
+            &change.text[newborn_span.start ..],
             newborn_span.len(),
             differential,
             &node.children().as_slice()[superseded_start ..],
@@ -272,7 +272,7 @@ fn replace(
 /// A description of a change.
 struct Change<'a> {
     /// The new source code, with the change applied.
-    src: &'a str,
+    text: &'a str,
     /// Which range in the old source file was changed.
     replaced: Range<usize>,
     /// How many characters replaced the text in `replaced`.
@@ -396,7 +396,7 @@ mod tests {
     fn test(prev: &str, range: Range<usize>, with: &str, goal: Range<usize>) {
         let mut source = Source::detached(prev);
         let range = source.edit(range, with);
-        check(source.src(), source.root(), &parse(source.src()));
+        check(source.text(), source.root(), &parse(source.text()));
         assert_eq!(range, goal);
     }
 
diff --git a/src/parse/mod.rs b/src/parse/mod.rs
index 0737d4ca..a8dee7f3 100644
--- a/src/parse/mod.rs
+++ b/src/parse/mod.rs
@@ -16,15 +16,15 @@ use crate::syntax::{NodeKind, SpanPos, SyntaxNode};
 use crate::util::EcoString;
 
 /// Parse a source file.
-pub fn parse(src: &str) -> SyntaxNode {
-    let mut p = Parser::new(src, TokenMode::Markup);
+pub fn parse(text: &str) -> SyntaxNode {
+    let mut p = Parser::new(text, TokenMode::Markup);
     markup(&mut p, true);
     p.finish().into_iter().next().unwrap()
 }
 
 /// Parse code directly, only used for syntax highlighting.
-pub fn parse_code(src: &str) -> Vec<SyntaxNode> {
-    let mut p = Parser::new(src, TokenMode::Code);
+pub fn parse_code(text: &str) -> Vec<SyntaxNode> {
+    let mut p = Parser::new(text, TokenMode::Code);
     code(&mut p);
     p.finish()
 }
@@ -34,10 +34,10 @@ pub fn parse_code(src: &str) -> Vec<SyntaxNode> {
 /// Returns `Some` if all of the input was consumed.
 fn reparse_code_block(
     prefix: &str,
-    src: &str,
+    text: &str,
     end_pos: usize,
 ) -> Option<(Vec<SyntaxNode>, bool, usize)> {
-    let mut p = Parser::with_prefix(prefix, src, TokenMode::Code);
+    let mut p = Parser::with_prefix(prefix, text, TokenMode::Code);
     if !p.at(NodeKind::LeftBrace) {
         return None;
     }
@@ -58,10 +58,10 @@ fn reparse_code_block(
 /// Returns `Some` if all of the input was consumed.
 fn reparse_content_block(
     prefix: &str,
-    src: &str,
+    text: &str,
     end_pos: usize,
 ) -> Option<(Vec<SyntaxNode>, bool, usize)> {
-    let mut p = Parser::with_prefix(prefix, src, TokenMode::Code);
+    let mut p = Parser::with_prefix(prefix, text, TokenMode::Code);
     if !p.at(NodeKind::LeftBracket) {
         return None;
     }
@@ -82,14 +82,14 @@ fn reparse_content_block(
 /// Returns `Some` if all of the input was consumed.
 fn reparse_markup_elements(
     prefix: &str,
-    src: &str,
+    text: &str,
     end_pos: usize,
     differential: isize,
     reference: &[SyntaxNode],
     mut at_start: bool,
     min_indent: usize,
 ) -> Option<(Vec<SyntaxNode>, bool, usize)> {
-    let mut p = Parser::with_prefix(prefix, src, TokenMode::Markup);
+    let mut p = Parser::with_prefix(prefix, text, TokenMode::Markup);
 
     let mut node: Option<&SyntaxNode> = None;
     let mut iter = reference.iter();
@@ -996,12 +996,12 @@ mod tests {
     use std::fmt::Debug;
 
     #[track_caller]
-    pub fn check<T>(src: &str, found: T, expected: T)
+    pub fn check<T>(text: &str, found: T, expected: T)
     where
         T: Debug + PartialEq,
     {
         if found != expected {
-            println!("source:   {src:?}");
+            println!("source:   {text:?}");
             println!("expected: {expected:#?}");
             println!("found:    {found:#?}");
             panic!("test failed");
diff --git a/src/parse/parser.rs b/src/parse/parser.rs
index 685f1e69..90b6e610 100644
--- a/src/parse/parser.rs
+++ b/src/parse/parser.rs
@@ -30,15 +30,15 @@ pub struct Parser<'s> {
 
 impl<'s> Parser<'s> {
     /// Create a new parser for the source string.
-    pub fn new(src: &'s str, mode: TokenMode) -> Self {
-        Self::with_prefix("", src, mode)
+    pub fn new(text: &'s str, mode: TokenMode) -> Self {
+        Self::with_prefix("", text, mode)
     }
 
     /// Create a new parser for the source string that is prefixed by some text
     /// that does not need to be parsed but taken into account for column
     /// calculation.
-    pub fn with_prefix(prefix: &str, src: &'s str, mode: TokenMode) -> Self {
-        let mut tokens = Tokens::with_prefix(prefix, src, mode);
+    pub fn with_prefix(prefix: &str, text: &'s str, mode: TokenMode) -> Self {
+        let mut tokens = Tokens::with_prefix(prefix, text, mode);
         let current = tokens.next();
         Self {
             tokens,
diff --git a/src/parse/resolve.rs b/src/parse/resolve.rs
index 6fab9f21..bce2da3c 100644
--- a/src/parse/resolve.rs
+++ b/src/parse/resolve.rs
@@ -23,7 +23,7 @@ pub fn resolve_string(string: &str) -> EcoString {
             Some('r') => out.push('\r'),
             Some('t') => out.push('\t'),
             Some('u') if s.eat_if('{') => {
-                // TODO: Feedback if closing brace is missing.
+                // TODO: Error if closing brace is missing.
                 let sequence = s.eat_while(char::is_ascii_hexdigit);
                 let _terminated = s.eat_if('}');
 
@@ -33,7 +33,7 @@ pub fn resolve_string(string: &str) -> EcoString {
                 }
             }
 
-            // TODO: Feedback about invalid escape sequence.
+            // TODO: Error for invalid escape sequence.
             _ => out.push_str(s.from(start)),
         }
     }
diff --git a/src/parse/tokens.rs b/src/parse/tokens.rs
index 67d413fd..84a63ba1 100644
--- a/src/parse/tokens.rs
+++ b/src/parse/tokens.rs
@@ -34,16 +34,16 @@ pub enum TokenMode {
 impl<'s> Tokens<'s> {
     /// Create a new token iterator with the given mode.
     #[inline]
-    pub fn new(src: &'s str, mode: TokenMode) -> Self {
-        Self::with_prefix("", src, mode)
+    pub fn new(text: &'s str, mode: TokenMode) -> Self {
+        Self::with_prefix("", text, mode)
     }
 
     /// Create a new token iterator with the given mode and a prefix to offset
     /// column calculations.
     #[inline]
-    pub fn with_prefix(prefix: &str, src: &'s str, mode: TokenMode) -> Self {
+    pub fn with_prefix(prefix: &str, text: &'s str, mode: TokenMode) -> Self {
         Self {
-            s: Scanner::new(src),
+            s: Scanner::new(text),
             mode,
             terminated: true,
             column_offset: column(prefix, prefix.len(), 0),
@@ -770,9 +770,9 @@ mod tests {
             t!(Markup $($tts)*);
             t!(Code $($tts)*);
         };
-        ($mode:ident $([$blocks:literal])?: $src:expr => $($token:expr),*) => {{
+        ($mode:ident $([$blocks:literal])?: $text:expr => $($token:expr),*) => {{
             // Test without suffix.
-            t!(@$mode: $src => $($token),*);
+            t!(@$mode: $text => $($token),*);
 
             // Suffixes described by four-tuples of:
             //
@@ -810,21 +810,21 @@ mod tests {
 
             // Test with each applicable suffix.
             for &(block, mode, suffix, ref token) in suffixes {
-                let src = $src;
+                let text = $text;
                 #[allow(unused_variables)]
                 let blocks = BLOCKS;
                 $(let blocks = $blocks;)?
                 assert!(!blocks.contains(|c| !BLOCKS.contains(c)));
                 if (mode.is_none() || mode == Some($mode)) && blocks.contains(block) {
-                    t!(@$mode: format!("{}{}", src, suffix) => $($token,)* token);
+                    t!(@$mode: format!("{}{}", text, suffix) => $($token,)* token);
                 }
             }
         }};
-        (@$mode:ident: $src:expr => $($token:expr),*) => {{
-            let src = $src;
-            let found = Tokens::new(&src, $mode).collect::<Vec<_>>();
+        (@$mode:ident: $text:expr => $($token:expr),*) => {{
+            let text = $text;
+            let found = Tokens::new(&text, $mode).collect::<Vec<_>>();
             let expected = vec![$($token.clone()),*];
-            check(&src, found, expected);
+            check(&text, found, expected);
         }};
     }
 
diff --git a/src/source.rs b/src/source.rs
index 24d830ad..c3648e11 100644
--- a/src/source.rs
+++ b/src/source.rs
@@ -1,158 +1,16 @@
 //! Source file management.
 
-use std::collections::HashMap;
-use std::io;
 use std::ops::Range;
 use std::path::{Path, PathBuf};
-use std::sync::Arc;
 
 use unscanny::Scanner;
 
-use crate::diag::{failed_to_load, StrResult, TypResult};
-use crate::loading::{FileHash, Loader};
+use crate::diag::TypResult;
 use crate::parse::{is_newline, parse, reparse};
 use crate::syntax::ast::Markup;
 use crate::syntax::{Span, SyntaxNode};
 use crate::util::{PathExt, StrExt};
 
-#[cfg(feature = "codespan-reporting")]
-use codespan_reporting::files::{self, Files};
-
-/// A unique identifier for a loaded source file.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
-pub struct SourceId(u16);
-
-impl SourceId {
-    /// Create a new source id for a file that is not part of a store.
-    pub const fn detached() -> Self {
-        Self(u16::MAX)
-    }
-
-    /// Create a source id from the raw underlying value.
-    ///
-    /// This should only be called with values returned by
-    /// [`into_raw`](Self::into_raw).
-    pub const fn from_raw(v: u16) -> Self {
-        Self(v)
-    }
-
-    /// Convert into the raw underlying value.
-    pub const fn into_raw(self) -> u16 {
-        self.0
-    }
-}
-
-/// Storage for loaded source files.
-pub struct SourceStore {
-    loader: Arc<dyn Loader>,
-    files: HashMap<FileHash, SourceId>,
-    sources: Vec<Source>,
-}
-
-impl SourceStore {
-    /// Create a new, empty source store.
-    pub fn new(loader: Arc<dyn Loader>) -> Self {
-        Self {
-            loader,
-            files: HashMap::new(),
-            sources: vec![],
-        }
-    }
-
-    /// Get a reference to a loaded source file.
-    ///
-    /// This panics if no source file with this `id` exists. This function
-    /// should only be called with ids returned by this store's
-    /// [`load()`](Self::load) and [`provide()`](Self::provide) methods.
-    #[track_caller]
-    pub fn get(&self, id: SourceId) -> &Source {
-        &self.sources[id.0 as usize]
-    }
-
-    /// Load a source file from a path relative to the compilation environment's
-    /// root.
-    ///
-    /// If there already exists a source file for this path, it is
-    /// [replaced](Source::replace).
-    pub fn load(&mut self, path: &Path) -> StrResult<SourceId> {
-        let mut try_load = || -> io::Result<SourceId> {
-            let hash = self.loader.resolve(path)?;
-            if let Some(&id) = self.files.get(&hash) {
-                return Ok(id);
-            }
-
-            let data = self.loader.file(path)?;
-            let src = String::from_utf8(data.to_vec()).map_err(|_| {
-                io::Error::new(io::ErrorKind::InvalidData, "file is not valid utf-8")
-            })?;
-
-            Ok(self.provide(path, src))
-        };
-
-        try_load().map_err(|err| failed_to_load("source file", path, err))
-    }
-
-    /// Directly provide a source file.
-    ///
-    /// The `path` does not need to be [resolvable](Loader::resolve) through the
-    /// `loader`. If it is though, imports that resolve to the same file hash
-    /// will use the inserted file instead of going through [`Loader::file`].
-    ///
-    /// If the path is resolvable and points to an existing source file, it is
-    /// [replaced](Source::replace).
-    pub fn provide(&mut self, path: impl AsRef<Path>, src: String) -> SourceId {
-        let path = path.as_ref();
-        let hash = self.loader.resolve(path).ok();
-
-        // Check for existing file and replace if one exists.
-        if let Some(&id) = hash.and_then(|hash| self.files.get(&hash)) {
-            self.replace(id, src);
-            return id;
-        }
-
-        // No existing file yet, so we allocate a new id.
-        let id = SourceId(self.sources.len() as u16);
-        self.sources.push(Source::new(id, path, src));
-
-        // Register in file map if the path was known to the loader.
-        if let Some(hash) = hash {
-            self.files.insert(hash, id);
-        }
-
-        id
-    }
-
-    /// Fully [replace](Source::replace) the source text of a file.
-    ///
-    /// This panics if no source file with this `id` exists.
-    #[track_caller]
-    pub fn replace(&mut self, id: SourceId, src: String) {
-        self.sources[id.0 as usize].replace(src)
-    }
-
-    /// [Edit](Source::edit) a source file by replacing the given range.
-    ///
-    /// This panics if no source file with this `id` exists or if the `replace`
-    /// range is out of bounds.
-    #[track_caller]
-    pub fn edit(
-        &mut self,
-        id: SourceId,
-        replace: Range<usize>,
-        with: &str,
-    ) -> Range<usize> {
-        self.sources[id.0 as usize].edit(replace, with)
-    }
-
-    /// Map a span that points into a [file](Source::range) stored in this
-    /// source store to a byte range.
-    ///
-    /// Panics if the span does not point into this source store.
-    pub fn range(&self, span: Span) -> Range<usize> {
-        self.get(span.source()).range(span)
-    }
-}
-
 /// A single source file.
 ///
 /// _Note_: All line and column indices start at zero, just like byte indices.
@@ -160,7 +18,7 @@ impl SourceStore {
 pub struct Source {
     id: SourceId,
     path: PathBuf,
-    src: String,
+    text: String,
     lines: Vec<Line>,
     root: SyntaxNode,
     rev: usize,
@@ -168,32 +26,32 @@ pub struct Source {
 
 impl Source {
     /// Create a new source file.
-    pub fn new(id: SourceId, path: &Path, src: String) -> Self {
+    pub fn new(id: SourceId, path: &Path, text: String) -> Self {
         let lines = std::iter::once(Line { byte_idx: 0, utf16_idx: 0 })
-            .chain(lines(0, 0, &src))
+            .chain(lines(0, 0, &text))
             .collect();
 
-        let mut root = parse(&src);
+        let mut root = parse(&text);
         root.numberize(id, Span::FULL).unwrap();
 
         Self {
             id,
             path: path.normalize(),
             root,
-            src,
+            text,
             lines,
             rev: 0,
         }
     }
 
     /// Create a source file without a real id and path, usually for testing.
-    pub fn detached(src: impl Into<String>) -> Self {
-        Self::new(SourceId::detached(), Path::new(""), src.into())
+    pub fn detached(text: impl Into<String>) -> Self {
+        Self::new(SourceId::detached(), Path::new(""), text.into())
     }
 
     /// Create a source file with the same synthetic span for all nodes.
-    pub fn synthesized(src: impl Into<String>, span: Span) -> Self {
-        let mut file = Self::detached(src);
+    pub fn synthesized(text: impl Into<String>, span: Span) -> Self {
+        let mut file = Self::detached(text);
         file.root.synthesize(span);
         file.id = span.source();
         file
@@ -225,8 +83,8 @@ impl Source {
     }
 
     /// The whole source as a string slice.
-    pub fn src(&self) -> &str {
-        &self.src
+    pub fn text(&self) -> &str {
+        &self.text
     }
 
     /// The revision number of the file.
@@ -239,15 +97,15 @@ impl Source {
 
     /// Slice out the part of the source code enclosed by the range.
     pub fn get(&self, range: Range<usize>) -> Option<&str> {
-        self.src.get(range)
+        self.text.get(range)
     }
 
     /// Fully replace the source text and increase the revision number.
-    pub fn replace(&mut self, src: String) {
-        self.src = src;
+    pub fn replace(&mut self, text: String) {
+        self.text = text;
         self.lines = vec![Line { byte_idx: 0, utf16_idx: 0 }];
-        self.lines.extend(lines(0, 0, &self.src));
-        self.root = parse(&self.src);
+        self.lines.extend(lines(0, 0, &self.text));
+        self.root = parse(&self.text);
         self.root.numberize(self.id(), Span::FULL).unwrap();
         self.rev = self.rev.wrapping_add(1);
     }
@@ -263,34 +121,34 @@ impl Source {
 
         let start_byte = replace.start;
         let start_utf16 = self.byte_to_utf16(replace.start).unwrap();
-        self.src.replace_range(replace.clone(), with);
+        self.text.replace_range(replace.clone(), with);
 
         // Remove invalidated line starts.
         let line = self.byte_to_line(start_byte).unwrap();
         self.lines.truncate(line + 1);
 
         // Handle adjoining of \r and \n.
-        if self.src[.. start_byte].ends_with('\r') && with.starts_with('\n') {
+        if self.text[.. start_byte].ends_with('\r') && with.starts_with('\n') {
             self.lines.pop();
         }
 
         // Recalculate the line starts after the edit.
         self.lines
-            .extend(lines(start_byte, start_utf16, &self.src[start_byte ..]));
+            .extend(lines(start_byte, start_utf16, &self.text[start_byte ..]));
 
         // Incrementally reparse the replaced range.
-        reparse(&mut self.root, &self.src, replace, with.len())
+        reparse(&mut self.root, &self.text, replace, with.len())
     }
 
     /// Get the length of the file in UTF-8 encoded bytes.
     pub fn len_bytes(&self) -> usize {
-        self.src.len()
+        self.text.len()
     }
 
     /// Get the length of the file in UTF-16 code units.
     pub fn len_utf16(&self) -> usize {
         let last = self.lines.last().unwrap();
-        last.utf16_idx + self.src[last.byte_idx ..].len_utf16()
+        last.utf16_idx + self.text[last.byte_idx ..].len_utf16()
     }
 
     /// Get the length of the file in lines.
@@ -311,13 +169,13 @@ impl Source {
     pub fn byte_to_utf16(&self, byte_idx: usize) -> Option<usize> {
         let line_idx = self.byte_to_line(byte_idx)?;
         let line = self.lines.get(line_idx)?;
-        let head = self.src.get(line.byte_idx .. byte_idx)?;
+        let head = self.text.get(line.byte_idx .. byte_idx)?;
         Some(line.utf16_idx + head.len_utf16())
     }
 
     /// Return the index of the line that contains the given byte index.
     pub fn byte_to_line(&self, byte_idx: usize) -> Option<usize> {
-        (byte_idx <= self.src.len()).then(|| {
+        (byte_idx <= self.text.len()).then(|| {
             match self.lines.binary_search_by_key(&byte_idx, |line| line.byte_idx) {
                 Ok(i) => i,
                 Err(i) => i - 1,
@@ -346,14 +204,14 @@ impl Source {
         )?;
 
         let mut k = line.utf16_idx;
-        for (i, c) in self.src[line.byte_idx ..].char_indices() {
+        for (i, c) in self.text[line.byte_idx ..].char_indices() {
             if k >= utf16_idx {
                 return Some(line.byte_idx + i);
             }
             k += c.len_utf16();
         }
 
-        (k == utf16_idx).then(|| self.src.len())
+        (k == utf16_idx).then(|| self.text.len())
     }
 
 
@@ -365,7 +223,7 @@ impl Source {
     /// Return the range which encloses the given line.
     pub fn line_to_range(&self, line_idx: usize) -> Option<Range<usize>> {
         let start = self.line_to_byte(line_idx)?;
-        let end = self.line_to_byte(line_idx + 1).unwrap_or(self.src.len());
+        let end = self.line_to_byte(line_idx + 1).unwrap_or(self.text.len());
         Some(start .. end)
     }
 
@@ -388,6 +246,30 @@ impl Source {
     }
 }
 
+/// A unique identifier for a loaded source file.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+pub struct SourceId(u16);
+
+impl SourceId {
+    /// Create a new source id for a file that is not part of a store.
+    pub const fn detached() -> Self {
+        Self(u16::MAX)
+    }
+
+    /// Create a source id from the raw underlying value.
+    ///
+    /// This should only be called with values returned by
+    /// [`into_raw`](Self::into_raw).
+    pub const fn from_raw(v: u16) -> Self {
+        Self(v)
+    }
+
+    /// Convert into the raw underlying value.
+    pub const fn into_raw(self) -> u16 {
+        self.0
+    }
+}
+
 /// Metadata about a line.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 struct Line {
@@ -401,9 +283,9 @@ struct Line {
 fn lines(
     byte_offset: usize,
     utf16_offset: usize,
-    string: &str,
+    text: &str,
 ) -> impl Iterator<Item = Line> + '_ {
-    let mut s = Scanner::new(string);
+    let mut s = Scanner::new(text);
     let mut utf16_idx = utf16_offset;
 
     std::iter::from_fn(move || {
@@ -427,56 +309,6 @@ fn lines(
     })
 }
 
-#[cfg(feature = "codespan-reporting")]
-impl<'a> Files<'a> for SourceStore {
-    type FileId = SourceId;
-    type Name = std::path::Display<'a>;
-    type Source = &'a str;
-
-    fn name(&'a self, id: SourceId) -> Result<Self::Name, files::Error> {
-        Ok(self.get(id).path().display())
-    }
-
-    fn source(&'a self, id: SourceId) -> Result<Self::Source, files::Error> {
-        Ok(self.get(id).src())
-    }
-
-    fn line_index(&'a self, id: SourceId, given: usize) -> Result<usize, files::Error> {
-        let source = self.get(id);
-        source
-            .byte_to_line(given)
-            .ok_or_else(|| files::Error::IndexTooLarge { given, max: source.len_bytes() })
-    }
-
-    fn line_range(
-        &'a self,
-        id: SourceId,
-        given: usize,
-    ) -> Result<std::ops::Range<usize>, files::Error> {
-        let source = self.get(id);
-        source
-            .line_to_range(given)
-            .ok_or_else(|| files::Error::LineTooLarge { given, max: source.len_lines() })
-    }
-
-    fn column_number(
-        &'a self,
-        id: SourceId,
-        _: usize,
-        given: usize,
-    ) -> Result<usize, files::Error> {
-        let source = self.get(id);
-        source.byte_to_column(given).ok_or_else(|| {
-            let max = source.len_bytes();
-            if given <= max {
-                files::Error::InvalidCharBoundary { given }
-            } else {
-                files::Error::IndexTooLarge { given, max }
-            }
-        })
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -563,7 +395,7 @@ mod tests {
             let mut source = Source::detached(prev);
             let result = Source::detached(after);
             source.edit(range, with);
-            assert_eq!(source.src, result.src);
+            assert_eq!(source.text, result.text);
             assert_eq!(source.root, result.root);
             assert_eq!(source.lines, result.lines);
         }
diff --git a/src/syntax/highlight.rs b/src/syntax/highlight.rs
index 6470e4fb..7f5ee083 100644
--- a/src/syntax/highlight.rs
+++ b/src/syntax/highlight.rs
@@ -384,10 +384,10 @@ mod tests {
         use Category::*;
 
         #[track_caller]
-        fn test(src: &str, goal: &[(Range<usize>, Category)]) {
+        fn test(text: &str, goal: &[(Range<usize>, Category)]) {
             let mut vec = vec![];
-            let source = Source::detached(src);
-            let full = 0 .. src.len();
+            let source = Source::detached(text);
+            let full = 0 .. text.len();
             highlight_node(source.root(), full, &mut |range, category| {
                 vec.push((range, category));
             });
diff --git a/src/syntax/mod.rs b/src/syntax/mod.rs
index eb070a04..c2b06efe 100644
--- a/src/syntax/mod.rs
+++ b/src/syntax/mod.rs
@@ -980,7 +980,7 @@ impl NodeKind {
             Self::LineComment => "line comment",
             Self::BlockComment => "block comment",
             Self::Error(_, _) => "parse error",
-            Self::Unknown(src) => match src.as_str() {
+            Self::Unknown(text) => match text.as_str() {
                 "*/" => "end of block comment",
                 _ => "invalid token",
             },
@@ -1107,7 +1107,7 @@ impl Hash for NodeKind {
             Self::LineComment => {}
             Self::BlockComment => {}
             Self::Error(pos, msg) => (pos, msg).hash(state),
-            Self::Unknown(src) => src.hash(state),
+            Self::Unknown(text) => text.hash(state),
         }
     }
 }
diff --git a/src/syntax/span.rs b/src/syntax/span.rs
index 3f66efa7..4eae4124 100644
--- a/src/syntax/span.rs
+++ b/src/syntax/span.rs
@@ -42,8 +42,8 @@ impl<T: Debug> Debug for Spanned<T> {
 /// A unique identifier for a syntax node.
 ///
 /// This is used throughout the compiler to track which source section an error
-/// or element stems from. Can be [mapped back](crate::source::SourceStore::range)
-/// to a source id + byte range for user facing display.
+/// or element stems from. Can be [mapped back](crate::source::Source::range)
+/// to a byte range for user facing display.
 ///
 /// Span ids are ordered in the tree to enable quickly finding the node with
 /// some id:
diff --git a/src/util/buffer.rs b/src/util/buffer.rs
new file mode 100644
index 00000000..daee86f9
--- /dev/null
+++ b/src/util/buffer.rs
@@ -0,0 +1,59 @@
+use std::fmt::{self, Debug, Formatter};
+use std::ops::Deref;
+use std::sync::Arc;
+
+use super::Prehashed;
+
+/// A shared buffer that is cheap to clone and hash.
+#[derive(Clone, Hash, Eq, PartialEq)]
+pub struct Buffer(Prehashed<Arc<Vec<u8>>>);
+
+impl Buffer {
+    /// Return a view into the buffer.
+    pub fn as_slice(&self) -> &[u8] {
+        self
+    }
+
+    /// Return a copy of the buffer as a vector.
+    pub fn to_vec(&self) -> Vec<u8> {
+        self.0.to_vec()
+    }
+}
+
+impl From<&[u8]> for Buffer {
+    fn from(slice: &[u8]) -> Self {
+        Self(Prehashed::new(Arc::new(slice.to_vec())))
+    }
+}
+
+impl From<Vec<u8>> for Buffer {
+    fn from(vec: Vec<u8>) -> Self {
+        Self(Prehashed::new(Arc::new(vec)))
+    }
+}
+
+impl From<Arc<Vec<u8>>> for Buffer {
+    fn from(arc: Arc<Vec<u8>>) -> Self {
+        Self(Prehashed::new(arc))
+    }
+}
+
+impl Deref for Buffer {
+    type Target = [u8];
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl AsRef<[u8]> for Buffer {
+    fn as_ref(&self) -> &[u8] {
+        self
+    }
+}
+
+impl Debug for Buffer {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        f.pad("Buffer(..)")
+    }
+}
diff --git a/src/util/mod.rs b/src/util/mod.rs
index e0ba312f..4a48b1d3 100644
--- a/src/util/mod.rs
+++ b/src/util/mod.rs
@@ -2,8 +2,10 @@
 
 #[macro_use]
 mod eco;
+mod buffer;
 mod hash;
 
+pub use buffer::Buffer;
 pub use eco::EcoString;
 pub use hash::Prehashed;