Remove 'static bound on World

Thanks to improvements in comemo, tracked types don't need to be 'static anymore. This means that the 'static bound on the `World` is now lifted and that the `Route` doesn't need to use unsafe code anymore to manage its lifetime.

Cargo.lock

@@ -369,8 +369,7 @@ checksum = "acbf1af155f9b9ef647e42cdc158db4b64a1b61f743629225fde6f3e0be2a7c7"
 [[package]]
 name = "comemo"
 version = "0.2.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1ba423e212681b51c5452a458bb24e88165f4c09857a783c802719cc46313f3f"
+source = "git+https://github.com/typst/comemo#0c141bbe47ca2d8c123fffc3f7f1ce35bb693993"
 dependencies = [
  "comemo-macros",
  "siphasher",
@@ -379,8 +378,7 @@ dependencies = [
 [[package]]
 name = "comemo-macros"
 version = "0.2.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fca5ceeb99665bad04a32fe297d1581a68685e36fb6da92a1c9b7d9693638c01"
+source = "git+https://github.com/typst/comemo#0c141bbe47ca2d8c123fffc3f7f1ce35bb693993"
 dependencies = [
  "proc-macro2",
  "quote",

Cargo.toml

@@ -36,7 +36,7 @@ bench = false
 typst-macros = { path = "macros" }
 bitflags = { version = "2", features = ["serde"] }
 bytemuck = "1"
-comemo = "0.2.2"
+comemo = { git = "https://github.com/typst/comemo" }
 ecow = "0.1"
 flate2 = "1"
 fontdb = "0.13"

cli/Cargo.toml

@@ -25,7 +25,7 @@ typst-library = { path = "../library" }
 chrono = { version = "0.4", default-features = false, features = ["clock", "std"] }
 clap = { version = "4.2.4", features = ["derive", "env"] }
 codespan-reporting = "0.11"
-comemo = "0.2.2"
+comemo = { git = "https://github.com/typst/comemo" }
 dirs = "5"
 elsa = "1.8"
 inferno = "0.11.15"

docs/Cargo.toml

@@ -13,7 +13,7 @@ bench = false
 [dependencies]
 typst = { path = ".." }
 typst-library = { path = "../library" }
-comemo = "0.2.2"
+comemo = { git = "https://github.com/typst/comemo" }
 heck = "0.4"
 include_dir = "0.7"
 once_cell = "1"

library/Cargo.toml

@@ -19,7 +19,7 @@ bench = false
 typst = { path = ".." }
 az = "1.2"
 chinese-number = { version = "0.7.2", default-features = false, features = ["number-to-chinese"] }
-comemo = "0.2.2"
+comemo = { git = "https://github.com/typst/comemo" }
 csv = "1"
 ecow = "0.1"
 hayagriva = "0.3"

library/src/layout/mod.rs

@@ -73,7 +73,7 @@ impl LayoutRoot for Content {
         #[comemo::memoize]
         fn cached(
             content: &Content,
-            world: Tracked<dyn World>,
+            world: Tracked<dyn World + '_>,
             tracer: TrackedMut<Tracer>,
             provider: TrackedMut<StabilityProvider>,
             introspector: Tracked<Introspector>,
@@ -139,7 +139,7 @@ impl Layout for Content {
         #[comemo::memoize]
         fn cached(
             content: &Content,
-            world: Tracked<dyn World>,
+            world: Tracked<dyn World + '_>,
             tracer: TrackedMut<Tracer>,
             provider: TrackedMut<StabilityProvider>,
             introspector: Tracked<Introspector>,

library/src/layout/par.rs

@@ -139,7 +139,7 @@ impl ParElem {
         #[allow(clippy::too_many_arguments)]
         fn cached(
             par: &ParElem,
-            world: Tracked<dyn World>,
+            world: Tracked<dyn World + '_>,
             tracer: TrackedMut<Tracer>,
             provider: TrackedMut<StabilityProvider>,
             introspector: Tracked<Introspector>,

library/src/meta/bibliography.rs

@@ -121,7 +121,7 @@ impl BibliographyElem {
 
     /// Find all bibliography keys.
     pub fn keys(
-        world: Tracked<dyn World>,
+        world: Tracked<dyn World + '_>,
         introspector: Tracked<Introspector>,
     ) -> Vec<(EcoString, Option<EcoString>)> {
         Self::find(introspector)
@@ -426,7 +426,7 @@ impl Works {
 /// Generate all citations and the whole bibliography.
 #[comemo::memoize]
 fn create(
-    world: Tracked<dyn World>,
+    world: Tracked<dyn World + '_>,
     bibliography: BibliographyElem,
     citations: Vec<CiteElem>,
 ) -> Arc<Works> {
@@ -582,7 +582,7 @@ fn create(
 /// Load bibliography entries from a path.
 #[comemo::memoize]
 fn load(
-    world: Tracked<dyn World>,
+    world: Tracked<dyn World + '_>,
     paths: &BibPaths,
 ) -> StrResult<EcoVec<hayagriva::Entry>> {
     let mut result = EcoVec::new();

library/src/meta/counter.rs

@@ -405,7 +405,7 @@ impl Counter {
     #[comemo::memoize]
     fn sequence_impl(
         &self,
-        world: Tracked<dyn World>,
+        world: Tracked<dyn World + '_>,
         tracer: TrackedMut<Tracer>,
         provider: TrackedMut<StabilityProvider>,
         introspector: Tracked<Introspector>,

library/src/meta/state.rs

@@ -320,7 +320,7 @@ impl State {
     #[comemo::memoize]
     fn sequence_impl(
         &self,
-        world: Tracked<dyn World>,
+        world: Tracked<dyn World + '_>,
         tracer: TrackedMut<Tracer>,
         provider: TrackedMut<StabilityProvider>,
         introspector: Tracked<Introspector>,

library/src/text/shaping.rs

@@ -448,8 +448,8 @@ impl Debug for ShapedText<'_> {
 }
 
 /// Holds shaping results and metadata common to all shaped segments.
-struct ShapingContext<'a> {
-    vt: &'a Vt<'a>,
+struct ShapingContext<'a, 'v> {
+    vt: &'a Vt<'v>,
     spans: &'a SpanMapper,
     glyphs: Vec<ShapedGlyph>,
     used: Vec<Font>,

library/src/visualize/image.rs

@@ -165,7 +165,7 @@ pub enum ImageFit {
 /// Load an image from a path.
 #[comemo::memoize]
 fn load(
-    world: Tracked<dyn World>,
+    world: Tracked<dyn World + '_>,
     full: &str,
     fallback_family: Option<&str>,
     alt: Option<EcoString>,

src/diag.rs

@@ -130,13 +130,13 @@ impl Display for Tracepoint {
 /// Enrich a [`SourceResult`] with a tracepoint.
 pub trait Trace<T> {
     /// Add the tracepoint to all errors that lie outside the `span`.
-    fn trace<F>(self, world: Tracked<dyn World>, make_point: F, span: Span) -> Self
+    fn trace<F>(self, world: Tracked<dyn World + '_>, make_point: F, span: Span) -> Self
     where
         F: Fn() -> Tracepoint;
 }
 
 impl<T> Trace<T> for SourceResult<T> {
-    fn trace<F>(self, world: Tracked<dyn World>, make_point: F, span: Span) -> Self
+    fn trace<F>(self, world: Tracked<dyn World + '_>, make_point: F, span: Span) -> Self
     where
         F: Fn() -> Tracepoint,
     {

src/eval/func.rs

@@ -4,7 +4,7 @@ use std::fmt::{self, Debug, Formatter};
 use std::hash::{Hash, Hasher};
 use std::sync::Arc;
 
-use comemo::{Prehashed, Track, Tracked, TrackedMut};
+use comemo::{Prehashed, Tracked, TrackedMut};
 use ecow::eco_format;
 use once_cell::sync::Lazy;
 
@@ -317,7 +317,7 @@ impl Closure {
     #[allow(clippy::too_many_arguments)]
     fn call(
         this: &Func,
-        world: Tracked<dyn World>,
+        world: Tracked<dyn World + '_>,
         route: Tracked<Route>,
         tracer: TrackedMut<Tracer>,
         provider: TrackedMut<StabilityProvider>,

src/eval/library.rs

@@ -67,7 +67,7 @@ pub struct LangItems {
     /// The keys contained in the bibliography and short descriptions of them.
     #[allow(clippy::type_complexity)]
     pub bibliography_keys: fn(
-        world: Tracked<dyn World>,
+        world: Tracked<dyn World + '_>,
         introspector: Tracked<Introspector>,
     ) -> Vec<(EcoString, Option<EcoString>)>,
     /// A section heading: `= Introduction`.

src/eval/mod.rs

@@ -41,7 +41,7 @@ use std::collections::HashSet;
 use std::mem;
 use std::path::{Path, PathBuf};
 
-use comemo::{Track, Tracked, TrackedMut};
+use comemo::{Track, Tracked, TrackedMut, Validate};
 use ecow::{EcoString, EcoVec};
 use unicode_segmentation::UnicodeSegmentation;
 
@@ -67,7 +67,7 @@ const MAX_CALL_DEPTH: usize = 64;
 #[comemo::memoize]
 #[tracing::instrument(skip(world, route, tracer, source))]
 pub fn eval(
-    world: Tracked<dyn World>,
+    world: Tracked<dyn World + '_>,
     route: Tracked<Route>,
     tracer: TrackedMut<Tracer>,
     source: &Source,
@@ -84,7 +84,7 @@ pub fn eval(
     set_lang_items(library.items.clone());
 
     // Evaluate the module.
-    let route = unsafe { Route::insert(route, id) };
+    let route = Route::insert(route, id);
     let scopes = Scopes::new(Some(library));
     let mut provider = StabilityProvider::new();
     let introspector = Introspector::new(&[]);
@@ -117,7 +117,7 @@ pub fn eval(
 /// Everything in the output is associated with the given `span`.
 #[comemo::memoize]
 pub fn eval_string(
-    world: Tracked<dyn World>,
+    world: Tracked<dyn World + '_>,
     code: &str,
     span: Span,
 ) -> SourceResult<Value> {
@@ -164,7 +164,7 @@ pub struct Vm<'a> {
     /// The language items.
     items: LangItems,
     /// The route of source ids the VM took to reach its current location.
-    route: Tracked<'a, Route>,
+    route: Tracked<'a, Route<'a>>,
     /// The current location.
     location: SourceId,
     /// A control flow event that is currently happening.
@@ -200,7 +200,7 @@ impl<'a> Vm<'a> {
     }
 
     /// Access the underlying world.
-    pub fn world(&self) -> Tracked<'a, dyn World> {
+    pub fn world(&self) -> Tracked<'a, dyn World + 'a> {
         self.vt.world
     }
 
@@ -263,34 +263,45 @@ impl Flow {
 
 /// A route of source ids.
 #[derive(Default)]
-pub struct Route {
-    parent: Option<Tracked<'static, Self>>,
+pub struct Route<'a> {
+    // We need to override the constraint's lifetime here so that `Tracked` is
+    // covariant over the constraint. If it becomes invariant, we're in for a
+    // world of lifetime pain.
+    outer: Option<Tracked<'a, Self, <Route<'static> as Validate>::Constraint>>,
     id: Option<SourceId>,
 }
 
-impl Route {
+impl<'a> Route<'a> {
     /// Create a new route with just one entry.
     pub fn new(id: SourceId) -> Self {
-        Self { id: Some(id), parent: None }
+        Self { id: Some(id), outer: None }
     }
 
     /// Insert a new id into the route.
     ///
     /// You must guarantee that `outer` lives longer than the resulting
     /// route is ever used.
-    unsafe fn insert(outer: Tracked<Route>, id: SourceId) -> Route {
-        Route {
-            parent: Some(std::mem::transmute(outer)),
-            id: Some(id),
+    pub fn insert(outer: Tracked<'a, Self>, id: SourceId) -> Self {
+        Route { outer: Some(outer), id: Some(id) }
+    }
+
+    /// Start tracking this locator.
+    ///
+    /// In comparison to [`Track::track`], this method skips this chain link
+    /// if it does not contribute anything.
+    pub fn track(&self) -> Tracked<'_, Self> {
+        match self.outer {
+            Some(outer) if self.id.is_none() => outer,
+            _ => Track::track(self),
         }
     }
 }
 
 #[comemo::track]
-impl Route {
+impl<'a> Route<'a> {
     /// Whether the given id is part of the route.
     fn contains(&self, id: SourceId) -> bool {
-        self.id == Some(id) || self.parent.map_or(false, |parent| parent.contains(id))
+        self.id == Some(id) || self.outer.map_or(false, |outer| outer.contains(id))
     }
 }
 

src/image.rs

@@ -53,7 +53,7 @@ impl Image {
     pub fn with_fonts(
         data: Buffer,
         format: ImageFormat,
-        world: Tracked<dyn World>,
+        world: Tracked<dyn World + '_>,
         fallback_family: Option<&str>,
         alt: Option<EcoString>,
     ) -> StrResult<Self> {
@@ -240,7 +240,7 @@ fn decode_svg(data: &Buffer) -> StrResult<Arc<DecodedImage>> {
 #[comemo::memoize]
 fn decode_svg_with_fonts(
     data: &Buffer,
-    world: Tracked<dyn World>,
+    world: Tracked<dyn World + '_>,
     fallback_family: Option<&str>,
 ) -> StrResult<Arc<DecodedImage>> {
     let mut opts = usvg::Options::default();
@@ -269,7 +269,7 @@ fn decode_svg_with_fonts(
 /// Discover and load the fonts referenced by an SVG.
 fn load_svg_fonts(
     tree: &usvg::Tree,
-    world: Tracked<dyn World>,
+    world: Tracked<dyn World + '_>,
     fallback_family: Option<&str>,
 ) -> fontdb::Database {
     let mut referenced = BTreeMap::<EcoString, bool>::new();

src/lib.rs

@@ -65,7 +65,7 @@ use crate::util::Buffer;
 
 /// Compile a source file into a fully layouted document.
 #[tracing::instrument(skip(world))]
-pub fn compile(world: &(dyn World + 'static)) -> SourceResult<Document> {
+pub fn compile(world: &dyn World) -> SourceResult<Document> {
     // Evaluate the source file into a module.
     let route = Route::default();
     let mut tracer = Tracer::default();

src/model/mod.rs

@@ -14,7 +14,7 @@ pub use self::styles::*;
 
 pub use typst_macros::element;
 
-use comemo::{Constraint, Track, Tracked, TrackedMut};
+use comemo::{Track, Tracked, TrackedMut, Validate};
 
 use crate::diag::SourceResult;
 use crate::doc::Document;
@@ -25,7 +25,7 @@ use crate::World;
 #[comemo::memoize]
 #[tracing::instrument(skip(world, tracer, content))]
 pub fn typeset(
-    world: Tracked<dyn World>,
+    world: Tracked<dyn World + '_>,
     mut tracer: TrackedMut<Tracer>,
     content: &Content,
 ) -> SourceResult<Document> {
@@ -42,8 +42,8 @@ pub fn typeset(
     loop {
         tracing::info!("Layout iteration {iter}");
 
-        let constraint = Constraint::new();
         let mut provider = StabilityProvider::new();
+        let constraint = <Introspector as Validate>::Constraint::new();
         let mut vt = Vt {
             world,
             tracer: TrackedMut::reborrow_mut(&mut tracer),
@@ -56,7 +56,7 @@ pub fn typeset(
 
         introspector = Introspector::new(&document.pages);
 
-        if iter >= 5 || introspector.valid(&constraint) {
+        if iter >= 5 || introspector.validate(&constraint) {
             break;
         }
     }
@@ -69,7 +69,7 @@ pub fn typeset(
 /// Holds the state needed to [typeset] content.
 pub struct Vt<'a> {
     /// The compilation environment.
-    pub world: Tracked<'a, dyn World>,
+    pub world: Tracked<'a, dyn World + 'a>,
     /// The tracer for inspection of the values an expression produces.
     pub tracer: TrackedMut<'a, Tracer>,
     /// Provides stable identities to elements.

tests/Cargo.toml

@@ -9,7 +9,7 @@ publish = false
 [dev-dependencies]
 typst = { path = ".." }
 typst-library = { path = "../library" }
-comemo = "0.2.2"
+comemo = { git = "https://github.com/typst/comemo" }
 elsa = "1.8"
 iai = { git = "https://github.com/reknih/iai" }
 once_cell = "1"