Split state and scopes, less ref-counting 🔀

bench/src/bench.rs

@@ -1,14 +1,12 @@
-use std::cell::RefCell;
-use std::rc::Rc;
-
 use criterion::{criterion_group, criterion_main, Criterion};
-use fontdock::fs::{FsIndex, FsSource};
+use fontdock::fs::FsIndex;
 
 use typst::env::{Env, ResourceLoader};
 use typst::eval::{eval, State};
 use typst::export::pdf;
-use typst::font::FontLoader;
+use typst::font::FsIndexExt;
 use typst::layout::layout;
+use typst::library;
 use typst::parse::parse;
 use typst::typeset;
 
@@ -25,25 +23,24 @@ fn benchmarks(c: &mut Criterion) {
     let mut index = FsIndex::new();
     index.search_dir(FONT_DIR);
 
-    let (files, descriptors) = index.into_vecs();
+    let mut env = Env {
-    let env = Rc::new(RefCell::new(Env {
+        fonts: index.into_dynamic_loader(),
-        fonts: FontLoader::new(Box::new(FsSource::new(files)), descriptors),
         resources: ResourceLoader::new(),
-    }));
+    };
+
+    let scope = library::new();
+    let state = State::default();
 
     // Prepare intermediate results and run warm.
-    let state = State::default();
     let syntax_tree = parse(COMA).output;
-    let layout_tree = eval(&syntax_tree, Rc::clone(&env), state.clone()).output;
+    let layout_tree = eval(&syntax_tree, &mut env, &scope, state.clone()).output;
-    let frames = layout(&layout_tree, Rc::clone(&env));
+    let frames = layout(&layout_tree, &mut env);
 
     // Bench!
     bench!("parse-coma": parse(COMA));
-    bench!("eval-coma": eval(&syntax_tree, Rc::clone(&env), state.clone()));
+    bench!("eval-coma": eval(&syntax_tree, &mut env, &scope, state.clone()));
-    bench!("layout-coma": layout(&layout_tree, Rc::clone(&env)));
+    bench!("layout-coma": layout(&layout_tree, &mut env));
-    bench!("typeset-coma": typeset(COMA, Rc::clone(&env), state.clone()));
+    bench!("typeset-coma": typeset(COMA, &mut env, &scope, state.clone()));
-
-    let env = env.borrow();
     bench!("export-pdf-coma": pdf::export(&frames, &env));
 }
 

src/env.rs

@@ -1,22 +1,17 @@
 //! Environment interactions.
 
 use std::any::Any;
-use std::cell::RefCell;
 use std::collections::{hash_map::Entry, HashMap};
 use std::fmt::{self, Debug, Formatter};
 use std::fs;
 use std::io::Cursor;
 use std::path::{Path, PathBuf};
-use std::rc::Rc;
 
 use image::io::Reader as ImageReader;
 use image::{DynamicImage, GenericImageView, ImageFormat};
 
 use crate::font::FontLoader;
 
-/// A reference-counted shared environment.
-pub type SharedEnv = Rc<RefCell<Env>>;
-
 /// Encapsulates all environment dependencies (fonts, resources).
 #[derive(Debug)]
 pub struct Env {

src/eval/call.rs

@@ -8,7 +8,7 @@ impl Eval for Spanned<&ExprCall> {
         let name = &self.v.name.v;
         let span = self.v.name.span;
 
-        if let Some(value) = ctx.state.scope.get(name) {
+        if let Some(value) = ctx.scopes.get(name) {
             if let Value::Func(func) = value {
                 let func = func.clone();
                 ctx.deco(Deco::Resolved.with_span(span));
@@ -90,10 +90,10 @@ impl Args {
     }
 
     /// Filter out and remove all convertible positional arguments.
-    pub fn filter<'a, T>(
+    pub fn filter<'a, 'b: 'a, T>(
         &'a mut self,
-        ctx: &'a mut EvalContext,
+        ctx: &'a mut EvalContext<'b>,
-    ) -> impl Iterator<Item = T> + 'a
+    ) -> impl Iterator<Item = T> + Captures<'a> + Captures<'b>
     where
         T: Cast<Spanned<Value>>,
     {
@@ -130,6 +130,13 @@ impl Args {
     }
 }
 
+// This is a workaround because `-> impl Trait + 'a + 'b` does not work.
+//
+// See also: https://github.com/rust-lang/rust/issues/49431
+#[doc(hidden)]
+pub trait Captures<'a> {}
+impl<'a, T: ?Sized> Captures<'a> for T {}
+
 /// Cast the value into `T`, generating an error if the conversion fails.
 fn cast<T>(ctx: &mut EvalContext, value: Spanned<Value>) -> Option<T>
 where

src/eval/context.rs

@@ -6,7 +6,6 @@ use fontdock::FontStyle;
 use super::*;
 use crate::diag::Diag;
 use crate::diag::{Deco, Feedback, Pass};
-use crate::env::SharedEnv;
 use crate::geom::{ChildAlign, Dir, Gen, LayoutDirs, Length, Linear, Sides, Size};
 use crate::layout::{
     Expansion, Node, NodePad, NodePages, NodePar, NodeSpacing, NodeStack, NodeText, Tree,
@@ -14,9 +13,11 @@ use crate::layout::{
 
 /// The context for evaluation.
 #[derive(Debug)]
-pub struct EvalContext {
+pub struct EvalContext<'a> {
     /// The environment from which resources are gathered.
-    pub env: SharedEnv,
+    pub env: &'a mut Env,
+    /// The active scopes.
+    pub scopes: Scopes<'a>,
     /// The active evaluation state.
     pub state: State,
     /// The accumulated feedback.
@@ -34,11 +35,12 @@ pub struct EvalContext {
     inner: Vec<Node>,
 }
 
-impl EvalContext {
+impl<'a> EvalContext<'a> {
-    /// Create a new evaluation context with a base state.
+    /// Create a new evaluation context with a base state and scope.
-    pub fn new(env: SharedEnv, state: State) -> Self {
+    pub fn new(env: &'a mut Env, scope: &'a Scope, state: State) -> Self {
         Self {
             env,
+            scopes: Scopes::new(scope),
             state,
             groups: vec![],
             inner: vec![],

src/eval/mod.rs

@@ -18,17 +18,23 @@ use std::rc::Rc;
 
 use crate::color::Color;
 use crate::diag::Pass;
-use crate::env::SharedEnv;
+use crate::env::Env;
 use crate::geom::{Angle, Length, Relative, Spec};
 use crate::layout::{self, Expansion, NodeSpacing, NodeStack};
 use crate::syntax::*;
 
 /// Evaluate a syntax tree into a layout tree.
 ///
-/// The given `state` is the base state that may be updated over the course of
+/// The `state` is the base state that may be updated over the course of
-/// evaluation.
+/// evaluation. The `scope` similarly consists of the base definitions that are
-pub fn eval(tree: &Tree, env: SharedEnv, state: State) -> Pass<layout::Tree> {
+/// present from the beginning (typically, the standard library).
-    let mut ctx = EvalContext::new(env, state);
+pub fn eval(
+    tree: &Tree,
+    env: &mut Env,
+    scope: &Scope,
+    state: State,
+) -> Pass<layout::Tree> {
+    let mut ctx = EvalContext::new(env, scope, state);
     ctx.start_page_group(Softness::Hard);
     tree.eval(&mut ctx);
     ctx.end_page_group(|s| s == Softness::Hard);
@@ -118,7 +124,7 @@ impl Eval for Spanned<&NodeRaw> {
 
     fn eval(self, ctx: &mut EvalContext) -> Self::Output {
         let prev = Rc::clone(&ctx.state.font.families);
-        let families = Rc::make_mut(&mut ctx.state.font.families);
+        let families = ctx.state.font.families_mut();
         families.list.insert(0, "monospace".to_string());
         families.flatten();
 
@@ -151,7 +157,7 @@ impl Eval for Spanned<&Expr> {
     fn eval(self, ctx: &mut EvalContext) -> Self::Output {
         match self.v {
             Expr::None => Value::None,
-            Expr::Ident(v) => match ctx.state.scope.get(v) {
+            Expr::Ident(v) => match ctx.scopes.get(v) {
                 Some(value) => value.clone(),
                 None => {
                     ctx.diag(error!(self.span, "unknown variable"));
@@ -179,7 +185,7 @@ impl Eval for Spanned<&Expr> {
                     Some(expr) => expr.as_ref().eval(ctx),
                     None => Value::None,
                 };
-                Rc::make_mut(&mut ctx.state.scope).set(v.pat.v.as_str(), value);
+                ctx.scopes.define(v.pat.v.as_str(), value);
                 Value::None
             }
         }

src/eval/scope.rs

@@ -1,27 +1,58 @@
 use std::collections::HashMap;
 use std::fmt::{self, Debug, Formatter};
+use std::iter;
 
 use super::Value;
 
-/// A map from identifiers to values.
+/// A hierarchy of scopes.
+#[derive(Debug, Clone, PartialEq)]
+pub struct Scopes<'a> {
+    /// The active scope.
+    top: Scope,
+    /// The stack of lower scopes.
+    scopes: Vec<Scope>,
+    /// The base scope.
+    base: &'a Scope,
+}
+
+impl<'a> Scopes<'a> {
+    /// Create a new hierarchy of scopes.
+    pub fn new(base: &'a Scope) -> Self {
+        Self { top: Scope::new(), scopes: vec![], base }
+    }
+
+    /// Look up the value of a variable in the scopes.
+    pub fn get(&self, var: &str) -> Option<&Value> {
+        iter::once(&self.top)
+            .chain(&self.scopes)
+            .chain(iter::once(self.base))
+            .find_map(|scope| scope.get(var))
+    }
+
+    /// Define a variable in the active scope.
+    pub fn define(&mut self, var: impl Into<String>, value: impl Into<Value>) {
+        self.top.set(var, value);
+    }
+}
+
+/// A map from variable names to values.
 #[derive(Default, Clone, PartialEq)]
 pub struct Scope {
     values: HashMap<String, Value>,
 }
 
 impl Scope {
-    // Create a new empty scope with a fallback function that is invoked when no
+    // Create a new empty scope.
-    // match is found.
     pub fn new() -> Self {
         Self::default()
     }
 
-    /// Return the value of the given variable.
+    /// Look up the value of a variable.
     pub fn get(&self, var: &str) -> Option<&Value> {
         self.values.get(var)
     }
 
-    /// Store the value for the given variable.
+    /// Store the value for a variable.
     pub fn set(&mut self, var: impl Into<String>, value: impl Into<Value>) {
         self.values.insert(var.into(), value.into());
     }

src/eval/state.rs

@@ -2,7 +2,6 @@ use std::rc::Rc;
 
 use fontdock::{fallback, FallbackTree, FontStretch, FontStyle, FontVariant, FontWeight};
 
-use super::Scope;
 use crate::geom::{
     Align, ChildAlign, Dir, LayoutDirs, Length, Linear, Relative, Sides, Size, Spec,
 };
@@ -12,14 +11,12 @@ use crate::paper::{Paper, PaperClass, PAPER_A4};
 /// The evaluation state.
 #[derive(Debug, Clone, PartialEq)]
 pub struct State {
-    /// The scope that contains variable definitions.
-    pub scope: Rc<Scope>,
     /// The current page state.
-    pub page: StatePage,
+    pub page: PageSettings,
     /// The current paragraph state.
-    pub par: StatePar,
+    pub par: ParSettings,
     /// The current font state.
-    pub font: StateFont,
+    pub font: FontSettings,
     /// The current directions.
     pub dirs: LayoutDirs,
     /// The current alignments.
@@ -29,10 +26,9 @@ pub struct State {
 impl Default for State {
     fn default() -> Self {
         Self {
-            scope: Rc::new(crate::library::_std()),
+            page: PageSettings::default(),
-            page: StatePage::default(),
+            par: ParSettings::default(),
-            par: StatePar::default(),
+            font: FontSettings::default(),
-            font: StateFont::default(),
             dirs: LayoutDirs::new(Dir::TTB, Dir::LTR),
             align: ChildAlign::new(Align::Start, Align::Start),
         }
@@ -41,7 +37,7 @@ impl Default for State {
 
 /// Defines page properties.
 #[derive(Debug, Copy, Clone, PartialEq)]
-pub struct StatePage {
+pub struct PageSettings {
     /// The class of this page.
     pub class: PaperClass,
     /// The width and height of the page.
@@ -53,7 +49,7 @@ pub struct StatePage {
     pub margins: Sides<Option<Linear>>,
 }
 
-impl StatePage {
+impl PageSettings {
     /// The default page style for the given paper.
     pub fn new(paper: Paper) -> Self {
         Self {
@@ -76,7 +72,7 @@ impl StatePage {
     }
 }
 
-impl Default for StatePage {
+impl Default for PageSettings {
     fn default() -> Self {
         Self::new(PAPER_A4)
     }
@@ -84,7 +80,7 @@ impl Default for StatePage {
 
 /// Defines paragraph properties.
 #[derive(Debug, Copy, Clone, PartialEq)]
-pub struct StatePar {
+pub struct ParSettings {
     /// The spacing between words (dependent on scaled font size).
     pub word_spacing: Linear,
     /// The spacing between lines (dependent on scaled font size).
@@ -93,7 +89,7 @@ pub struct StatePar {
     pub par_spacing: Linear,
 }
 
-impl Default for StatePar {
+impl Default for ParSettings {
     fn default() -> Self {
         Self {
             word_spacing: Relative::new(0.25).into(),
@@ -105,7 +101,7 @@ impl Default for StatePar {
 
 /// Defines font properties.
 #[derive(Debug, Clone, PartialEq)]
-pub struct StateFont {
+pub struct FontSettings {
     /// A tree of font family names and generic class names.
     pub families: Rc<FallbackTree>,
     /// The selected font variant.
@@ -122,14 +118,19 @@ pub struct StateFont {
     pub emph: bool,
 }
 
-impl StateFont {
+impl FontSettings {
+    /// Access the `families` mutably.
+    pub fn families_mut(&mut self) -> &mut FallbackTree {
+        Rc::make_mut(&mut self.families)
+    }
+
     /// The absolute font size.
     pub fn font_size(&self) -> Length {
         self.scale.resolve(self.size)
     }
 }
 
-impl Default for StateFont {
+impl Default for FontSettings {
     fn default() -> Self {
         Self {
             /// The default tree of font fallbacks.

src/font.rs

@@ -3,6 +3,9 @@
 use fontdock::{ContainsChar, FaceFromVec, FontSource};
 use ttf_parser::Face;
 
+#[cfg(feature = "fs")]
+use fontdock::fs::{FsIndex, FsSource};
+
 /// A font loader that is backed by a dynamic source.
 pub type FontLoader = fontdock::FontLoader<Box<dyn FontSource<Face = FaceBuf>>>;
 
@@ -47,3 +50,18 @@ impl ContainsChar for FaceBuf {
         self.get().glyph_index(c).is_some()
     }
 }
+
+#[cfg(feature = "fs")]
+pub trait FsIndexExt {
+    /// Create a font loader backed by a boxed [`FsSource`] which serves all
+    /// indexed font faces.
+    fn into_dynamic_loader(self) -> FontLoader;
+}
+
+#[cfg(feature = "fs")]
+impl FsIndexExt for FsIndex {
+    fn into_dynamic_loader(self) -> FontLoader {
+        let (files, descriptors) = self.into_vecs();
+        FontLoader::new(Box::new(FsSource::new(files)), descriptors)
+    }
+}

src/layout/mod.rs

@@ -8,7 +8,7 @@ mod spacing;
 mod stack;
 mod text;
 
-use crate::env::{ResourceId, SharedEnv};
+use crate::env::{Env, ResourceId};
 use crate::geom::*;
 use crate::shaping::Shaped;
 
@@ -21,7 +21,7 @@ pub use stack::*;
 pub use text::*;
 
 /// Layout a tree into a collection of frames.
-pub fn layout(tree: &Tree, env: SharedEnv) -> Vec<Frame> {
+pub fn layout(tree: &Tree, env: &mut Env) -> Vec<Frame> {
     tree.layout(&mut LayoutContext { env })
 }
 
@@ -65,10 +65,10 @@ pub trait Layout {
 }
 
 /// The context for layouting.
-#[derive(Debug, Clone)]
+#[derive(Debug)]
-pub struct LayoutContext {
+pub struct LayoutContext<'a> {
     /// The environment from which fonts are gathered.
-    pub env: SharedEnv,
+    pub env: &'a mut Env,
 }
 
 /// A collection of areas to layout into.

src/layout/text.rs

@@ -25,13 +25,12 @@ pub struct NodeText {
 
 impl Layout for NodeText {
     fn layout(&self, ctx: &mut LayoutContext, _: &Areas) -> Layouted {
-        let mut env = ctx.env.borrow_mut();
         Layouted::Frame(
             shaping::shape(
                 &self.text,
                 self.dir,
                 self.font_size,
-                &mut env.fonts,
+                &mut ctx.env.fonts,
                 &self.families,
                 self.variant,
             ),

src/lib.rs

@@ -42,18 +42,21 @@ pub mod pretty;
 pub mod shaping;
 pub mod syntax;
 
-use std::rc::Rc;
-
 use crate::diag::{Feedback, Pass};
-use crate::env::SharedEnv;
+use crate::env::Env;
-use crate::eval::State;
+use crate::eval::{Scope, State};
 use crate::layout::Frame;
 
 /// Process _Typst_ source code directly into a collection of frames.
-pub fn typeset(src: &str, env: SharedEnv, state: State) -> Pass<Vec<Frame>> {
+pub fn typeset(
+    src: &str,
+    env: &mut Env,
+    scope: &Scope,
+    state: State,
+) -> Pass<Vec<Frame>> {
     let Pass { output: syntax_tree, feedback: f1 } = parse::parse(src);
     let Pass { output: layout_tree, feedback: f2 } =
-        eval::eval(&syntax_tree, Rc::clone(&env), state);
+        eval::eval(&syntax_tree, env, scope, state);
     let frames = layout::layout(&layout_tree, env);
     Pass::new(frames, Feedback::join(f1, f2))
 }

src/library/insert.rs

@@ -16,12 +16,9 @@ pub fn image(ctx: &mut EvalContext, args: &mut Args) -> Value {
     let height = args.get(ctx, "height");
 
     if let Some(path) = path {
-        let mut env = ctx.env.borrow_mut();
+        let loaded = ctx.env.resources.load(path.v, ImageResource::parse);
-        let loaded = env.resources.load(path.v, ImageResource::parse);
-
         if let Some((res, img)) = loaded {
             let dimensions = img.buf.dimensions();
-            drop(env);
             ctx.push(NodeImage {
                 res,
                 dimensions,
@@ -30,7 +27,6 @@ pub fn image(ctx: &mut EvalContext, args: &mut Args) -> Value {
                 align: ctx.state.align,
             });
         } else {
-            drop(env);
             ctx.diag(error!(path.span, "failed to load image"));
         }
     }

src/library/mod.rs

@@ -1,4 +1,7 @@
 //! The standard library.
+//!
+//! Call [`new`] to obtain a [`Scope`] containing all standard library
+//! definitions.
 
 mod extend;
 mod insert;
@@ -15,8 +18,8 @@ use fontdock::{FontStretch, FontStyle, FontWeight};
 use crate::eval::{Scope, ValueAny, ValueFunc};
 use crate::geom::Dir;
 
-/// The scope containing the standard library.
+/// Construct a scope containing all standard library definitions.
-pub fn _std() -> Scope {
+pub fn new() -> Scope {
     let mut std = Scope::new();
     macro_rules! set {
         (func: $name:expr, $func:expr) => {

src/library/style.rs

@@ -1,5 +1,4 @@
 use std::fmt::{self, Display, Formatter};
-use std::rc::Rc;
 
 use fontdock::{FontStretch, FontStyle, FontWeight};
 
@@ -69,7 +68,7 @@ pub fn font(ctx: &mut EvalContext, args: &mut Args) -> Value {
 
     let list: Vec<_> = args.filter::<FontFamily>(ctx).map(|f| f.to_string()).collect();
     if !list.is_empty() {
-        let families = Rc::make_mut(&mut ctx.state.font.families);
+        let families = ctx.state.font.families_mut();
         families.list = list;
         families.flatten();
     }
@@ -89,7 +88,7 @@ pub fn font(ctx: &mut EvalContext, args: &mut Args) -> Value {
     for variant in FontFamily::VARIANTS {
         if let Some(FontFamilies(list)) = args.get(ctx, variant.as_str()) {
             let strings = list.into_iter().map(|f| f.to_string()).collect();
-            let families = Rc::make_mut(&mut ctx.state.font.families);
+            let families = ctx.state.font.families_mut();
             families.update_class_list(variant.to_string(), strings);
             families.flatten();
         }

src/main.rs

@@ -1,16 +1,15 @@
-use std::cell::RefCell;
 use std::fs;
 use std::path::{Path, PathBuf};
-use std::rc::Rc;
 
 use anyhow::{anyhow, bail, Context};
-use fontdock::fs::{FsIndex, FsSource};
+use fontdock::fs::FsIndex;
 
 use typst::diag::{Feedback, Pass};
 use typst::env::{Env, ResourceLoader};
 use typst::eval::State;
 use typst::export::pdf;
-use typst::font::FontLoader;
+use typst::font::FsIndexExt;
+use typst::library;
 use typst::parse::LineMap;
 use typst::typeset;
 
@@ -41,17 +40,18 @@ fn main() -> anyhow::Result<()> {
     index.search_dir("fonts");
     index.search_system();
 
-    let (files, descriptors) = index.into_vecs();
+    let mut env = Env {
-    let env = Rc::new(RefCell::new(Env {
+        fonts: index.into_dynamic_loader(),
-        fonts: FontLoader::new(Box::new(FsSource::new(files)), descriptors),
         resources: ResourceLoader::new(),
-    }));
+    };
 
+    let scope = library::new();
     let state = State::default();
+
     let Pass {
         output: frames,
         feedback: Feedback { mut diags, .. },
-    } = typeset(&src, Rc::clone(&env), state);
+    } = typeset(&src, &mut env, &scope, state);
 
     if !diags.is_empty() {
         diags.sort();
@@ -72,7 +72,7 @@ fn main() -> anyhow::Result<()> {
         }
     }
 
-    let pdf_data = pdf::export(&frames, &env.borrow());
+    let pdf_data = pdf::export(&frames, &env);
     fs::write(&dest_path, pdf_data).context("Failed to write PDF file.")?;
 
     Ok(())

tests/typeset.rs

@@ -1,11 +1,9 @@
-use std::cell::RefCell;
 use std::env;
 use std::ffi::OsStr;
 use std::fs;
 use std::path::Path;
-use std::rc::Rc;
 
-use fontdock::fs::{FsIndex, FsSource};
+use fontdock::fs::FsIndex;
 use image::{GenericImageView, Rgba};
 use tiny_skia::{
     Canvas, Color, ColorU8, FillRule, FilterQuality, Paint, PathBuilder, Pattern, Pixmap,
@@ -15,12 +13,13 @@ use ttf_parser::OutlineBuilder;
 use walkdir::WalkDir;
 
 use typst::diag::{Diag, Feedback, Level, Pass};
-use typst::env::{Env, ImageResource, ResourceLoader, SharedEnv};
+use typst::env::{Env, ImageResource, ResourceLoader};
 use typst::eval::{Args, EvalContext, Scope, State, Value, ValueFunc};
 use typst::export::pdf;
-use typst::font::FontLoader;
+use typst::font::FsIndexExt;
 use typst::geom::{Length, Point, Sides, Size, Spec};
 use typst::layout::{Element, Expansion, Frame, Image};
+use typst::library;
 use typst::parse::{LineMap, Scanner};
 use typst::pretty::{Pretty, Printer};
 use typst::shaping::Shaped;
@@ -61,11 +60,10 @@ fn main() {
     let mut index = FsIndex::new();
     index.search_dir(FONT_DIR);
 
-    let (files, descriptors) = index.into_vecs();
+    let mut env = Env {
-    let env = Rc::new(RefCell::new(Env {
+        fonts: index.into_dynamic_loader(),
-        fonts: FontLoader::new(Box::new(FsSource::new(files)), descriptors),
         resources: ResourceLoader::new(),
-    }));
+    };
 
     let playground = Path::new("playground.typ");
     if playground.exists() && filtered.is_empty() {
@@ -74,7 +72,7 @@ fn main() {
             Path::new("playground.png"),
             Path::new("playground.pdf"),
             None,
-            &env,
+            &mut env,
         );
     }
 
@@ -84,7 +82,7 @@ fn main() {
         let png_path = Path::new(PNG_DIR).join(&relative).with_extension("png");
         let pdf_path = Path::new(PDF_DIR).join(&relative).with_extension("pdf");
         let ref_path = Path::new(REF_DIR).join(&relative).with_extension("png");
-        ok &= test(&src_path, &png_path, &pdf_path, Some(&ref_path), &env);
+        ok &= test(&src_path, &png_path, &pdf_path, Some(&ref_path), &mut env);
     }
 
     if !ok {
@@ -127,7 +125,7 @@ fn test(
     png_path: &Path,
     pdf_path: &Path,
     ref_path: Option<&Path>,
-    env: &SharedEnv,
+    env: &mut Env,
 ) -> bool {
     let name = src_path.strip_prefix(TYP_DIR).unwrap_or(src_path);
     println!("Testing {}", name.display());
@@ -143,7 +141,6 @@ fn test(
         frames.extend(part_frames);
     }
 
-    let env = env.borrow();
     if !frames.is_empty() {
         let pdf_data = pdf::export(&frames, &env);
         fs::create_dir_all(&pdf_path.parent().unwrap()).unwrap();
@@ -173,23 +170,24 @@ fn test(
     ok
 }
 
-fn test_part(i: usize, src: &str, env: &SharedEnv) -> (bool, Vec<Frame>) {
+fn test_part(i: usize, src: &str, env: &mut Env) -> (bool, Vec<Frame>) {
     let map = LineMap::new(src);
     let (compare_ref, ref_diags) = parse_metadata(src, &map);
 
-    let mut state = State::default();
+    let mut scope = library::new();
+    register_helpers(&mut scope);
 
     // We want to have "unbounded" pages, so we allow them to be infinitely
     // large and fit them to match their content.
+    let mut state = State::default();
     state.page.size = Size::new(Length::pt(120.0), Length::raw(f64::INFINITY));
     state.page.expand = Spec::new(Expansion::Fill, Expansion::Fit);
     state.page.margins = Sides::uniform(Some(Length::pt(10.0).into()));
-    register_helpers(Rc::make_mut(&mut state.scope));
 
     let Pass {
         output: mut frames,
         feedback: Feedback { mut diags, .. },
-    } = typeset(&src, Rc::clone(env), state);
+    } = typeset(&src, env, &scope, state);
 
     if !compare_ref {
         frames.clear();