Refactor folding (#3294)

26 files changed, 303 insertions, 409 deletions

diff --git a/crates/typst-macros/src/elem.rs b/crates/typst-macros/src/elem.rs
index 722131b7..91147b8d 100644
--- a/crates/typst-macros/src/elem.rs
+++ b/crates/typst-macros/src/elem.rs
@@ -106,7 +106,9 @@ impl Elem {
     /// This includes:
     /// - Fields that are not synthesized.
     fn construct_fields(&self) -> impl Iterator<Item = &Field> + Clone {
-        self.real_fields().filter(|field| !field.synthesized)
+        self.real_fields().filter(|field| {
+            !field.synthesized && (!field.internal || field.parse.is_some())
+        })
     }
 }
 
@@ -263,11 +265,6 @@ fn parse_field(field: &syn::Field) -> Result<Field> {
         field.output = parse_quote! { <#output as #foundations::Resolve>::Output };
     }
 
-    if field.fold {
-        let output = &field.output;
-        field.output = parse_quote! { <#output as #foundations::Fold>::Output };
-    }
-
     validate_attrs(&attrs)?;
 
     Ok(field)
@@ -555,32 +552,42 @@ fn create_style_chain_access(
     let elem = &element.ident;
 
     let Field { ty, default, enum_ident, .. } = field;
-    let getter = match (field.fold, field.resolve, field.borrowed) {
-        (false, false, false) => quote! { get },
-        (false, false, true) => quote! { get_borrowed },
-        (false, true, _) => quote! { get_resolve },
-        (true, false, _) => quote! { get_fold },
-        (true, true, _) => quote! { get_resolve_fold },
+
+    let getter = match (field.fold, field.borrowed) {
+        (false, false) => quote! { get },
+        (false, true) => quote! { get_ref },
+        (true, _) => quote! { get_folded },
     };
 
-    let default = default
-        .clone()
-        .unwrap_or_else(|| parse_quote! { ::std::default::Default::default() });
-    let (init, default) = field.fold.then(|| (None, quote! { || #default })).unwrap_or_else(|| (
-        Some(quote! {
+    let mut default = match default {
+        Some(default) => quote! { #default },
+        None => quote! { ::std::default::Default::default() },
+    };
+
+    let mut init = None;
+    if field.borrowed {
+        init = Some(quote! {
             static DEFAULT: ::once_cell::sync::Lazy<#ty> = ::once_cell::sync::Lazy::new(|| #default);
-        }),
-        quote! { &DEFAULT },
-    ));
+        });
+        default = quote! { &DEFAULT };
+    }
 
-    quote! {
-        #init
+    let mut value = quote! {
         styles.#getter::<#ty>(
             <Self as #foundations::NativeElement>::elem(),
             <#elem as #foundations::Fields>::Enum::#enum_ident as u8,
             #inherent,
-            #default,
+            || #default,
         )
+    };
+
+    if field.resolve {
+        value = quote! { #foundations::Resolve::resolve(#value, styles) };
+    }
+
+    quote! {
+        #init
+        #value
     }
 }
 
@@ -995,21 +1002,18 @@ fn create_param_info(field: &Field) -> TokenStream {
         variadic,
         required,
         default,
-        fold,
         ty,
-        output,
         ..
     } = field;
     let named = !positional;
     let settable = field.settable();
-    let default_ty = if *fold { &output } else { &ty };
     let default = quote_option(&settable.then(|| {
         let default = default
             .clone()
             .unwrap_or_else(|| parse_quote! { ::std::default::Default::default() });
         quote! {
             || {
-                let typed: #default_ty = #default;
+                let typed: #ty = #default;
                 #foundations::IntoValue::into_value(typed)
             }
         }
diff --git a/crates/typst/src/foundations/auto.rs b/crates/typst/src/foundations/auto.rs
index fcd72999..05f776d1 100644
--- a/crates/typst/src/foundations/auto.rs
+++ b/crates/typst/src/foundations/auto.rs
@@ -239,14 +239,14 @@ impl<T: Resolve> Resolve for Smart<T> {
     }
 }
 
-impl<T> Fold for Smart<T>
-where
-    T: Fold,
-    T::Output: Default,
-{
-    type Output = Smart<T::Output>;
-
-    fn fold(self, outer: Self::Output) -> Self::Output {
-        self.map(|inner| inner.fold(outer.unwrap_or_default()))
+impl<T: Fold> Fold for Smart<T> {
+    fn fold(self, outer: Self) -> Self {
+        use Smart::Custom;
+        match (self, outer) {
+            (Custom(inner), Custom(outer)) => Custom(inner.fold(outer)),
+            // An explicit `auto` should be respected, thus we don't do
+            // `inner.or(outer)`.
+            (inner, _) => inner,
+        }
     }
 }
diff --git a/crates/typst/src/foundations/dict.rs b/crates/typst/src/foundations/dict.rs
index 291b8f60..da82889d 100644
--- a/crates/typst/src/foundations/dict.rs
+++ b/crates/typst/src/foundations/dict.rs
@@ -138,7 +138,6 @@ impl Dict {
         };
 
         let mut msg = String::from(match unexpected.len() {
-            0 => unreachable!(),
             1 => "unexpected key ",
             _ => "unexpected keys ",
         });
diff --git a/crates/typst/src/foundations/styles.rs b/crates/typst/src/foundations/styles.rs
index f44a320f..83279a7b 100644
--- a/crates/typst/src/foundations/styles.rs
+++ b/crates/typst/src/foundations/styles.rs
@@ -6,7 +6,6 @@ use std::{iter, mem, ptr};
 
 use comemo::Prehashed;
 use ecow::{eco_vec, EcoString, EcoVec};
-use once_cell::sync::Lazy;
 use smallvec::SmallVec;
 
 use crate::diag::{SourceResult, Trace, Tracepoint};
@@ -457,54 +456,47 @@ impl<'a> StyleChain<'a> {
         Chainable::chain(local, self)
     }
 
-    /// Cast the first value for the given property in the chain,
-    /// returning a borrowed value if possible.
-    pub fn get_borrowed<T: Clone>(
-        self,
-        func: Element,
-        id: u8,
-        inherent: Option<&'a T>,
-        default: &'static Lazy<T>,
-    ) -> &'a T {
-        self.properties::<T>(func, id, inherent)
-            .next()
-            .unwrap_or_else(|| default)
-    }
-
     /// Cast the first value for the given property in the chain.
-    pub fn get<T: Clone>(
+    pub fn get<T: Clone + 'static>(
         self,
         func: Element,
         id: u8,
         inherent: Option<&T>,
-        default: &'static Lazy<T>,
+        default: impl Fn() -> T,
     ) -> T {
-        self.get_borrowed(func, id, inherent, default).clone()
+        self.properties::<T>(func, id, inherent)
+            .next()
+            .cloned()
+            .unwrap_or_else(default)
     }
 
-    /// Cast the first value for the given property in the chain.
-    pub fn get_resolve<T: Clone + Resolve>(
+    /// Cast the first value for the given property in the chain,
+    /// returning a borrowed value.
+    pub fn get_ref<T: 'static>(
         self,
         func: Element,
         id: u8,
-        inherent: Option<&T>,
-        default: &'static Lazy<T>,
-    ) -> T::Output {
-        self.get(func, id, inherent, default).resolve(self)
+        inherent: Option<&'a T>,
+        default: impl Fn() -> &'a T,
+    ) -> &'a T {
+        self.properties::<T>(func, id, inherent)
+            .next()
+            .unwrap_or_else(default)
     }
 
-    /// Cast the first value for the given property in the chain.
-    pub fn get_fold<T: Clone + Fold + 'static>(
+    /// Cast the first value for the given property in the chain, taking
+    /// `Fold` implementations into account.
+    pub fn get_folded<T: Fold + Clone + 'static>(
         self,
         func: Element,
         id: u8,
         inherent: Option<&T>,
-        default: impl Fn() -> T::Output,
-    ) -> T::Output {
+        default: impl Fn() -> T,
+    ) -> T {
         fn next<T: Fold>(
             mut values: impl Iterator<Item = T>,
-            default: &impl Fn() -> T::Output,
-        ) -> T::Output {
+            default: &impl Fn() -> T,
+        ) -> T {
             values
                 .next()
                 .map(|value| value.fold(next(values, default)))
@@ -513,36 +505,6 @@ impl<'a> StyleChain<'a> {
         next(self.properties::<T>(func, id, inherent).cloned(), &default)
     }
 
-    /// Cast the first value for the given property in the chain.
-    pub fn get_resolve_fold<T>(
-        self,
-        func: Element,
-        id: u8,
-        inherent: Option<&T>,
-        default: impl Fn() -> <T::Output as Fold>::Output,
-    ) -> <T::Output as Fold>::Output
-    where
-        T: Resolve + Clone + 'static,
-        T::Output: Fold,
-    {
-        fn next<T>(
-            mut values: impl Iterator<Item = T>,
-            styles: StyleChain,
-            default: &impl Fn() -> <T::Output as Fold>::Output,
-        ) -> <T::Output as Fold>::Output
-        where
-            T: Resolve + 'static,
-            T::Output: Fold,
-        {
-            values
-                .next()
-                .map(|value| value.resolve(styles).fold(next(values, styles, default)))
-                .unwrap_or_else(default)
-        }
-
-        next(self.properties::<T>(func, id, inherent).cloned(), self, &default)
-    }
-
     /// Iterate over all style recipes in the chain.
     pub fn recipes(self) -> impl Iterator<Item = &'a Recipe> {
         self.entries().filter_map(Style::recipe)
@@ -925,38 +887,36 @@ impl<T: Resolve> Resolve for Option<T> {
 /// #rect()
 /// ```
 pub trait Fold {
-    /// The type of the folded output.
-    type Output;
-
     /// Fold this inner value with an outer folded value.
-    fn fold(self, outer: Self::Output) -> Self::Output;
+    fn fold(self, outer: Self) -> Self;
 }
 
-impl<T> Fold for Option<T>
-where
-    T: Fold,
-    T::Output: Default,
-{
-    type Output = Option<T::Output>;
+impl Fold for bool {
+    fn fold(self, _: Self) -> Self {
+        self
+    }
+}
 
-    fn fold(self, outer: Self::Output) -> Self::Output {
-        self.map(|inner| inner.fold(outer.unwrap_or_default()))
+impl<T: Fold> Fold for Option<T> {
+    fn fold(self, outer: Self) -> Self {
+        match (self, outer) {
+            (Some(inner), Some(outer)) => Some(inner.fold(outer)),
+            // An explicit `None` should be respected, thus we don't do
+            // `inner.or(outer)`.
+            (inner, _) => inner,
+        }
     }
 }
 
 impl<T> Fold for Vec<T> {
-    type Output = Vec<T>;
-
-    fn fold(mut self, outer: Self::Output) -> Self::Output {
+    fn fold(mut self, outer: Self) -> Self {
         self.extend(outer);
         self
     }
 }
 
 impl<T, const N: usize> Fold for SmallVec<[T; N]> {
-    type Output = SmallVec<[T; N]>;
-
-    fn fold(mut self, outer: Self::Output) -> Self::Output {
+    fn fold(mut self, outer: Self) -> Self {
         self.extend(outer);
         self
     }
diff --git a/crates/typst/src/layout/align.rs b/crates/typst/src/layout/align.rs
index e6b56f18..934bfa19 100644
--- a/crates/typst/src/layout/align.rs
+++ b/crates/typst/src/layout/align.rs
@@ -215,9 +215,7 @@ impl Repr for Alignment {
 }
 
 impl Fold for Alignment {
-    type Output = Self;
-
-    fn fold(self, outer: Self::Output) -> Self::Output {
+    fn fold(self, outer: Self) -> Self {
         match (self, outer) {
             (Self::H(x), Self::V(y) | Self::Both(_, y)) => Self::Both(x, y),
             (Self::V(y), Self::H(x) | Self::Both(x, _)) => Self::Both(x, y),
diff --git a/crates/typst/src/layout/axes.rs b/crates/typst/src/layout/axes.rs
index e5c47edd..82cb4aee 100644
--- a/crates/typst/src/layout/axes.rs
+++ b/crates/typst/src/layout/axes.rs
@@ -3,7 +3,7 @@ use std::fmt::{self, Debug, Formatter};
 use std::ops::{BitAnd, BitAndAssign, BitOr, BitOrAssign, Deref, Not};
 
 use crate::diag::bail;
-use crate::foundations::{array, cast, Array, Fold, Resolve, Smart, StyleChain};
+use crate::foundations::{array, cast, Array, Resolve, Smart, StyleChain};
 use crate::layout::{Abs, Dir, Length, Ratio, Rel};
 use crate::util::Get;
 
@@ -84,14 +84,6 @@ impl<T> Axes<T> {
     {
         f(&self.x) && f(&self.y)
     }
-
-    /// Filter the individual fields with a mask.
-    pub fn filter(self, mask: Axes<bool>) -> Axes<Option<T>> {
-        Axes {
-            x: if mask.x { Some(self.x) } else { None },
-            y: if mask.y { Some(self.y) } else { None },
-        }
-    }
 }
 
 impl<T: Default> Axes<T> {
@@ -198,16 +190,6 @@ cast! {
     "vertical" => Self::Y,
 }
 
-impl<T> Axes<Option<T>> {
-    /// Unwrap the individual fields.
-    pub fn unwrap_or(self, other: Axes<T>) -> Axes<T> {
-        Axes {
-            x: self.x.unwrap_or(other.x),
-            y: self.y.unwrap_or(other.y),
-        }
-    }
-}
-
 impl<T> Axes<Smart<T>> {
     /// Unwrap the individual fields.
     pub fn unwrap_or(self, other: Axes<T>) -> Axes<T> {
@@ -325,14 +307,3 @@ impl<T: Resolve> Resolve for Axes<T> {
         self.map(|v| v.resolve(styles))
     }
 }
-
-impl<T: Fold> Fold for Axes<Option<T>> {
-    type Output = Axes<T::Output>;
-
-    fn fold(self, outer: Self::Output) -> Self::Output {
-        self.zip_map(outer, |inner, outer| match inner {
-            Some(value) => value.fold(outer),
-            None => outer,
-        })
-    }
-}
diff --git a/crates/typst/src/layout/container.rs b/crates/typst/src/layout/container.rs
index 7a673a4a..c4de09fe 100644
--- a/crates/typst/src/layout/container.rs
+++ b/crates/typst/src/layout/container.rs
@@ -133,7 +133,7 @@ impl Packed<BoxElem> {
 
         // Apply inset.
         let mut body = self.body(styles).unwrap_or_default();
-        let inset = self.inset(styles);
+        let inset = self.inset(styles).unwrap_or_default();
         if inset.iter().any(|v| !v.is_zero()) {
             body = body.padded(inset.map(|side| side.map(Length::from)));
         }
@@ -154,20 +154,24 @@ impl Packed<BoxElem> {
 
         // Prepare fill and stroke.
         let fill = self.fill(styles);
-        let stroke = self.stroke(styles).map(|s| s.map(Stroke::unwrap_or_default));
+        let stroke = self
+            .stroke(styles)
+            .unwrap_or_default()
+            .map(|s| s.map(Stroke::unwrap_or_default));
 
         // Clip the contents
         if self.clip(styles) {
-            let outset = self.outset(styles).relative_to(frame.size());
+            let outset =
+                self.outset(styles).unwrap_or_default().relative_to(frame.size());
             let size = frame.size() + outset.sum_by_axis();
-            let radius = self.radius(styles);
+            let radius = self.radius(styles).unwrap_or_default();
             frame.clip(clip_rect(size, radius, &stroke));
         }
 
         // Add fill and/or stroke.
         if fill.is_some() || stroke.iter().any(Option::is_some) {
-            let outset = self.outset(styles);
-            let radius = self.radius(styles);
+            let outset = self.outset(styles).unwrap_or_default();
+            let radius = self.radius(styles).unwrap_or_default();
             frame.fill_and_stroke(fill, stroke, outset, radius, self.span());
         }
 
@@ -350,7 +354,7 @@ impl LayoutMultiple for Packed<BlockElem> {
     ) -> SourceResult<Fragment> {
         // Apply inset.
         let mut body = self.body(styles).unwrap_or_default();
-        let inset = self.inset(styles);
+        let inset = self.inset(styles).unwrap_or_default();
         if inset.iter().any(|v| !v.is_zero()) {
             body = body.clone().padded(inset.map(|side| side.map(Length::from)));
         }
@@ -418,14 +422,18 @@ impl LayoutMultiple for Packed<BlockElem> {
 
         // Prepare fill and stroke.
         let fill = self.fill(styles);
-        let stroke = self.stroke(styles).map(|s| s.map(Stroke::unwrap_or_default));
+        let stroke = self
+            .stroke(styles)
+            .unwrap_or_default()
+            .map(|s| s.map(Stroke::unwrap_or_default));
 
         // Clip the contents
         if self.clip(styles) {
             for frame in frames.iter_mut() {
-                let outset = self.outset(styles).relative_to(frame.size());
+                let outset =
+                    self.outset(styles).unwrap_or_default().relative_to(frame.size());
                 let size = frame.size() + outset.sum_by_axis();
-                let radius = self.radius(styles);
+                let radius = self.radius(styles).unwrap_or_default();
                 frame.clip(clip_rect(size, radius, &stroke));
             }
         }
@@ -437,8 +445,8 @@ impl LayoutMultiple for Packed<BlockElem> {
                 skip = first.is_empty() && rest.iter().any(|frame| !frame.is_empty());
             }
 
-            let outset = self.outset(styles);
-            let radius = self.radius(styles);
+            let outset = self.outset(styles).unwrap_or_default();
+            let radius = self.radius(styles).unwrap_or_default();
             for frame in frames.iter_mut().skip(skip as usize) {
                 frame.fill_and_stroke(
                     fill.clone(),
diff --git a/crates/typst/src/layout/corners.rs b/crates/typst/src/layout/corners.rs
index e674b04d..85fd0503 100644
--- a/crates/typst/src/layout/corners.rs
+++ b/crates/typst/src/layout/corners.rs
@@ -80,6 +80,16 @@ impl<T> Corners<T> {
     }
 }
 
+impl<T> Corners<Option<T>> {
+    /// Unwrap-or-default the individual corners.
+    pub fn unwrap_or_default(self) -> Corners<T>
+    where
+        T: Default,
+    {
+        self.map(Option::unwrap_or_default)
+    }
+}
+
 impl<T> Get<Corner> for Corners<T> {
     type Component = T;
 
@@ -133,20 +143,21 @@ impl<T: Reflect> Reflect for Corners<Option<T>> {
     }
 }
 
-impl<T> IntoValue for Corners<T>
+impl<T> IntoValue for Corners<Option<T>>
 where
     T: PartialEq + IntoValue,
 {
     fn into_value(self) -> Value {
         if self.is_uniform() {
-            return self.top_left.into_value();
+            if let Some(top_left) = self.top_left {
+                return top_left.into_value();
+            }
         }
 
         let mut dict = Dict::new();
-        let mut handle = |key: &str, component: T| {
-            let value = component.into_value();
-            if value != Value::None {
-                dict.insert(key.into(), value);
+        let mut handle = |key: &str, component: Option<T>| {
+            if let Some(c) = component {
+                dict.insert(key.into(), c.into_value());
             }
         };
 
@@ -228,12 +239,13 @@ impl<T: Resolve> Resolve for Corners<T> {
 }
 
 impl<T: Fold> Fold for Corners<Option<T>> {
-    type Output = Corners<T::Output>;
-
-    fn fold(self, outer: Self::Output) -> Self::Output {
-        self.zip(outer).map(|(inner, outer)| match inner {
-            Some(value) => value.fold(outer),
-            None => outer,
+    fn fold(self, outer: Self) -> Self {
+        self.zip(outer).map(|(inner, outer)| match (inner, outer) {
+            (Some(inner), Some(outer)) => Some(inner.fold(outer)),
+            // Usually, folding an inner `None` with an `outer` preferres the
+            // explicit `None`. However, here `None` means unspecified and thus
+            // we want `outer`.
+            (inner, outer) => inner.or(outer),
         })
     }
 }
diff --git a/crates/typst/src/layout/grid/layout.rs b/crates/typst/src/layout/grid/layout.rs
index f9957fcb..c17bbda5 100644
--- a/crates/typst/src/layout/grid/layout.rs
+++ b/crates/typst/src/layout/grid/layout.rs
@@ -151,7 +151,7 @@ pub trait ResolvableCell {
         y: usize,
         fill: &Option<Paint>,
         align: Smart<Alignment>,
-        inset: Sides<Rel<Length>>,
+        inset: Sides<Option<Rel<Length>>>,
         styles: StyleChain,
     ) -> Cell;
 
@@ -204,7 +204,7 @@ impl CellGrid {
         cells: &[T],
         fill: &Celled<Option<Paint>>,
         align: &Celled<Smart<Alignment>>,
-        inset: Sides<Rel<Length>>,
+        inset: Sides<Option<Rel<Length>>>,
         engine: &mut Engine,
         styles: StyleChain,
         span: Span,
diff --git a/crates/typst/src/layout/grid/mod.rs b/crates/typst/src/layout/grid/mod.rs
index 544d43a8..ee2eeecf 100644
--- a/crates/typst/src/layout/grid/mod.rs
+++ b/crates/typst/src/layout/grid/mod.rs
@@ -13,8 +13,8 @@ use crate::foundations::{
     cast, elem, scope, Array, Content, Fold, Packed, Show, Smart, StyleChain, Value,
 };
 use crate::layout::{
-    Abs, AlignElem, Alignment, Axes, Fragment, LayoutMultiple, Length, Regions, Rel,
-    Sides, Sizing,
+    AlignElem, Alignment, Axes, Fragment, LayoutMultiple, Length, Regions, Rel, Sides,
+    Sizing,
 };
 use crate::syntax::Span;
 use crate::util::NonZeroExt;
@@ -264,7 +264,6 @@ pub struct GridElem {
     /// )
     /// ```
     #[fold]
-    #[default(Sides::splat(Abs::pt(0.0).into()))]
     pub inset: Sides<Option<Rel<Length>>>,
 
     /// The contents of the grid cells.
@@ -462,7 +461,7 @@ impl ResolvableCell for Packed<GridCell> {
         y: usize,
         fill: &Option<Paint>,
         align: Smart<Alignment>,
-        inset: Sides<Rel<Length>>,
+        inset: Sides<Option<Rel<Length>>>,
         styles: StyleChain,
     ) -> Cell {
         let cell = &mut *self;
@@ -481,9 +480,8 @@ impl ResolvableCell for Packed<GridCell> {
             Smart::Auto => cell.align(styles),
         });
         cell.push_inset(Smart::Custom(
-            cell.inset(styles).map_or(inset, |inner| inner.fold(inset)).map(Some),
+            cell.inset(styles).map_or(inset, |inner| inner.fold(inset)),
         ));
-
         Cell { body: self.pack(), fill, colspan }
     }
 
diff --git a/crates/typst/src/layout/length.rs b/crates/typst/src/layout/length.rs
index 94e85248..7365ca19 100644
--- a/crates/typst/src/layout/length.rs
+++ b/crates/typst/src/layout/length.rs
@@ -5,7 +5,7 @@ use std::ops::{Add, Div, Mul, Neg};
 use ecow::{eco_format, EcoString};
 
 use crate::diag::{At, Hint, SourceResult};
-use crate::foundations::{func, scope, ty, Repr, Resolve, StyleChain, Styles};
+use crate::foundations::{func, scope, ty, Fold, Repr, Resolve, StyleChain, Styles};
 use crate::layout::{Abs, Em};
 use crate::syntax::Span;
 use crate::util::Numeric;
@@ -274,3 +274,9 @@ impl Resolve for Length {
         self.abs + self.em.resolve(styles)
     }
 }
+
+impl Fold for Length {
+    fn fold(self, _: Self) -> Self {
+        self
+    }
+}
diff --git a/crates/typst/src/layout/page.rs b/crates/typst/src/layout/page.rs
index 7e94984b..bb9097a6 100644
--- a/crates/typst/src/layout/page.rs
+++ b/crates/typst/src/layout/page.rs
@@ -549,18 +549,11 @@ impl Margin {
 }
 
 impl Fold for Margin {
-    type Output = Margin;
-
-    fn fold(self, outer: Self::Output) -> Self::Output {
-        let sides =
-            self.sides
-                .zip(outer.sides)
-                .map(|(inner, outer)| match (inner, outer) {
-                    (Some(value), Some(outer)) => Some(value.fold(outer)),
-                    _ => inner.or(outer),
-                });
-        let two_sided = self.two_sided.or(outer.two_sided);
-        Margin { sides, two_sided }
+    fn fold(self, outer: Self) -> Self {
+        Margin {
+            sides: self.sides.fold(outer.sides),
+            two_sided: self.two_sided.fold(outer.two_sided),
+        }
     }
 }
 
diff --git a/crates/typst/src/layout/rel.rs b/crates/typst/src/layout/rel.rs
index 8f937102..df58df86 100644
--- a/crates/typst/src/layout/rel.rs
+++ b/crates/typst/src/layout/rel.rs
@@ -259,19 +259,12 @@ where
     }
 }
 
-impl Fold for Rel<Abs> {
-    type Output = Self;
-
-    fn fold(self, _: Self::Output) -> Self::Output {
-        self
-    }
-}
-
-impl Fold for Rel<Length> {
-    type Output = Self;
-
-    fn fold(self, _: Self::Output) -> Self::Output {
-        self
+impl<T> Fold for Rel<T>
+where
+    T: Numeric + Fold,
+{
+    fn fold(self, outer: Self) -> Self {
+        Self { rel: self.rel, abs: self.abs.fold(outer.abs) }
     }
 }
 
diff --git a/crates/typst/src/layout/sides.rs b/crates/typst/src/layout/sides.rs
index 937919c4..bb35ffb3 100644
--- a/crates/typst/src/layout/sides.rs
+++ b/crates/typst/src/layout/sides.rs
@@ -94,6 +94,16 @@ impl<T: Add> Sides<T> {
     }
 }
 
+impl<T> Sides<Option<T>> {
+    /// Unwrap-or-default the individual sides.
+    pub fn unwrap_or_default(self) -> Sides<T>
+    where
+        T: Default,
+    {
+        self.map(Option::unwrap_or_default)
+    }
+}
+
 impl Sides<Rel<Abs>> {
     /// Evaluate the sides relative to the given `size`.
     pub fn relative_to(self, size: Size) -> Sides<Abs> {
@@ -159,20 +169,21 @@ impl<T: Reflect> Reflect for Sides<Option<T>> {
     }
 }
 
-impl<T> IntoValue for Sides<T>
+impl<T> IntoValue for Sides<Option<T>>
 where
     T: PartialEq + IntoValue,
 {
     fn into_value(self) -> Value {
         if self.is_uniform() {
-            return self.left.into_value();
+            if let Some(left) = self.left {
+                return left.into_value();
+            }
         }
 
         let mut dict = Dict::new();
-        let mut handle = |key: &str, component: T| {
-            let value = component.into_value();
-            if value != Value::None {
-                dict.insert(key.into(), value);
+        let mut handle = |key: &str, component: Option<T>| {
+            if let Some(c) = component {
+                dict.insert(key.into(), c.into_value());
             }
         };
 
@@ -233,12 +244,13 @@ impl<T: Resolve> Resolve for Sides<T> {
 }
 
 impl<T: Fold> Fold for Sides<Option<T>> {
-    type Output = Sides<T::Output>;
-
-    fn fold(self, outer: Self::Output) -> Self::Output {
-        self.zip(outer).map(|(inner, outer)| match inner {
-            Some(value) => value.fold(outer),
-            None => outer,
+    fn fold(self, outer: Self) -> Self {
+        self.zip(outer).map(|(inner, outer)| match (inner, outer) {
+            (Some(inner), Some(outer)) => Some(inner.fold(outer)),
+            // Usually, folding an inner `None` with an `outer` preferres the
+            // explicit `None`. However, here `None` means unspecified and thus
+            // we want `outer`.
+            (inner, outer) => inner.or(outer),
         })
     }
 }
diff --git a/crates/typst/src/math/cancel.rs b/crates/typst/src/math/cancel.rs
index 039ef752..695ff567 100644
--- a/crates/typst/src/math/cancel.rs
+++ b/crates/typst/src/math/cancel.rs
@@ -97,7 +97,7 @@ pub struct CancelElem {
     #[fold]
     #[default(Stroke {
         // Default stroke has 0.5pt for better visuals.
-        thickness: Smart::Custom(Abs::pt(0.5)),
+        thickness: Smart::Custom(Abs::pt(0.5).into()),
         ..Default::default()
     })]
     pub stroke: Stroke,
diff --git a/crates/typst/src/math/matrix.rs b/crates/typst/src/math/matrix.rs
index 616cc738..97b01491 100644
--- a/crates/typst/src/math/matrix.rs
+++ b/crates/typst/src/math/matrix.rs
@@ -425,11 +425,10 @@ fn layout_mat_body(
     };
 
     let (hline, vline, stroke) = match augment {
-        Some(v) => {
-            // need to get stroke here for ownership
-            let stroke = v.stroke_or(default_stroke);
-
-            (v.hline, v.vline, stroke)
+        Some(augment) => {
+            // We need to get stroke here for ownership.
+            let stroke = augment.stroke.unwrap_or_default().unwrap_or(default_stroke);
+            (augment.hline, augment.vline, stroke)
         }
         _ => (AugmentOffsets::default(), AugmentOffsets::default(), default_stroke),
     };
@@ -593,11 +592,19 @@ pub struct Augment<T: Numeric = Length> {
     pub stroke: Smart<Stroke<T>>,
 }
 
-impl Augment<Abs> {
-    fn stroke_or(&self, fallback: FixedStroke) -> FixedStroke {
-        match &self.stroke {
-            Smart::Custom(v) => v.clone().unwrap_or(fallback),
-            Smart::Auto => fallback,
+impl<T: Numeric + Fold> Fold for Augment<T> {
+    fn fold(self, outer: Self) -> Self {
+        Self {
+            stroke: match (self.stroke, outer.stroke) {
+                (Smart::Custom(inner), Smart::Custom(outer)) => {
+                    Smart::Custom(inner.fold(outer))
+                }
+                // Usually, folding an inner `auto` with an `outer` preferres
+                // the explicit `auto`. However, here `auto` means unspecified
+                // and thus we want `outer`.
+                (inner, outer) => inner.or(outer),
+            },
+            ..self
         }
     }
 }
@@ -614,21 +621,6 @@ impl Resolve for Augment {
     }
 }
 
-impl Fold for Augment<Abs> {
-    type Output = Augment<Abs>;
-
-    fn fold(mut self, outer: Self::Output) -> Self::Output {
-        // Special case for handling `auto` strokes in subsequent `Augment`.
-        if self.stroke.is_auto() && outer.stroke.is_custom() {
-            self.stroke = outer.stroke;
-        } else {
-            self.stroke = self.stroke.fold(outer.stroke);
-        }
-
-        self
-    }
-}
-
 cast! {
     Augment,
     self => {
@@ -637,13 +629,11 @@ cast! {
             return self.vline.0[0].into_value();
         }
 
-        let d = dict! {
-            "hline" => self.hline.into_value(),
-            "vline" => self.vline.into_value(),
-            "stroke" => self.stroke.into_value()
-        };
-
-        d.into_value()
+        dict! {
+            "hline" => self.hline,
+            "vline" => self.vline,
+            "stroke" => self.stroke,
+        }.into_value()
     },
     v: isize => Augment {
         hline: AugmentOffsets::default(),
@@ -651,15 +641,15 @@ cast! {
         stroke: Smart::Auto,
     },
     mut dict: Dict => {
-        // need the transpose for the defaults to work
-        let hline = dict.take("hline").ok().map(AugmentOffsets::from_value)
-            .transpose().unwrap_or_default().unwrap_or_default();
-        let vline = dict.take("vline").ok().map(AugmentOffsets::from_value)
-            .transpose().unwrap_or_default().unwrap_or_default();
-
-        let stroke = dict.take("stroke").ok().map(Stroke::from_value)
-            .transpose()?.map(Smart::Custom).unwrap_or(Smart::Auto);
-
+        let mut take = |key| dict.take(key).ok().map(AugmentOffsets::from_value).transpose();
+        let hline = take("hline")?.unwrap_or_default();
+        let vline = take("vline")?.unwrap_or_default();
+        let stroke = dict.take("stroke")
+            .ok()
+            .map(Stroke::from_value)
+            .transpose()?
+            .map(Smart::Custom)
+            .unwrap_or(Smart::Auto);
         Augment { hline, vline, stroke }
     },
 }
diff --git a/crates/typst/src/model/bibliography.rs b/crates/typst/src/model/bibliography.rs
index 94681fe1..6e20e98a 100644
--- a/crates/typst/src/model/bibliography.rs
+++ b/crates/typst/src/model/bibliography.rs
@@ -323,7 +323,6 @@ impl LocalName for Packed<BibliographyElem> {
 }
 
 /// A loaded bibliography.
-#[ty]
 #[derive(Clone, PartialEq)]
 pub struct Bibliography {
     map: Arc<IndexMap<PicoStr, hayagriva::Entry>>,
@@ -422,12 +421,6 @@ impl Hash for Bibliography {
     }
 }
 
-impl Repr for Bibliography {
-    fn repr(&self) -> EcoString {
-        "..".into()
-    }
-}
-
 /// Format a BibLaTeX loading error.
 fn format_biblatex_error(path: &str, src: &str, errors: Vec<BibLaTeXError>) -> EcoString {
     let Some(error) = errors.first() else {
diff --git a/crates/typst/src/model/emph.rs b/crates/typst/src/model/emph.rs
index b67643de..a4c916ed 100644
--- a/crates/typst/src/model/emph.rs
+++ b/crates/typst/src/model/emph.rs
@@ -36,6 +36,6 @@ pub struct EmphElem {
 impl Show for Packed<EmphElem> {
     #[typst_macros::time(name = "emph", span = self.span())]
     fn show(&self, _: &mut Engine, _: StyleChain) -> SourceResult<Content> {
-        Ok(self.body().clone().styled(TextElem::set_emph(ItalicToggle)))
+        Ok(self.body().clone().styled(TextElem::set_emph(ItalicToggle(true))))
     }
 }
diff --git a/crates/typst/src/model/enum.rs b/crates/typst/src/model/enum.rs
index 622501db..0c1a31c5 100644
--- a/crates/typst/src/model/enum.rs
+++ b/crates/typst/src/model/enum.rs
@@ -1,10 +1,10 @@
 use std::str::FromStr;
 
+use smallvec::{smallvec, SmallVec};
+
 use crate::diag::{bail, SourceResult};
 use crate::engine::Engine;
-use crate::foundations::{
-    cast, elem, scope, Array, Content, Fold, Packed, Smart, StyleChain,
-};
+use crate::foundations::{cast, elem, scope, Array, Content, Packed, Smart, StyleChain};
 use crate::layout::{
     Alignment, Axes, BlockElem, Cell, CellGrid, Em, Fragment, GridLayouter, HAlignment,
     LayoutMultiple, Length, Regions, Sizing, Spacing, VAlignment,
@@ -199,7 +199,7 @@ pub struct EnumElem {
     /// The numbers of parent items.
     #[internal]
     #[fold]
-    parents: Parent,
+    parents: SmallVec<[usize; 4]>,
 }
 
 #[scope]
@@ -229,6 +229,8 @@ impl LayoutMultiple for Packed<EnumElem> {
         let mut cells = vec![];
         let mut number = self.start(styles);
         let mut parents = self.parents(styles);
+        parents.reverse();
+
         let full = self.full(styles);
 
         // Horizontally align based on the given respective parameter.
@@ -263,7 +265,7 @@ impl LayoutMultiple for Packed<EnumElem> {
             cells.push(Cell::from(resolved));
             cells.push(Cell::from(Content::empty()));
             cells.push(Cell::from(
-                item.body().clone().styled(EnumElem::set_parents(Parent(number))),
+                item.body().clone().styled(EnumElem::set_parents(smallvec![number])),
             ));
             number = number.saturating_add(1);
         }
@@ -309,21 +311,3 @@ cast! {
     },
     v: Content => v.unpack::<Self>().unwrap_or_else(Self::new),
 }
-
-#[derive(Debug, Clone, Copy, PartialEq, Hash)]
-struct Parent(usize);
-
-cast! {
-    Parent,
-    self => self.0.into_value(),
-    v: usize => Self(v),
-}
-
-impl Fold for Parent {
-    type Output = Vec<usize>;
-
-    fn fold(self, mut outer: Self::Output) -> Self::Output {
-        outer.push(self.0);
-        outer
-    }
-}
diff --git a/crates/typst/src/model/list.rs b/crates/typst/src/model/list.rs
index 71a586b9..c849fa65 100644
--- a/crates/typst/src/model/list.rs
+++ b/crates/typst/src/model/list.rs
@@ -150,7 +150,7 @@ impl LayoutMultiple for Packed<ListElem> {
                 .unwrap_or_else(|| *BlockElem::below_in(styles).amount())
         };
 
-        let depth = self.depth(styles);
+        let Depth(depth) = self.depth(styles);
         let marker = self
             .marker(styles)
             .resolve(engine, depth)?
@@ -162,8 +162,9 @@ impl LayoutMultiple for Packed<ListElem> {
             cells.push(Cell::from(Content::empty()));
             cells.push(Cell::from(marker.clone()));
             cells.push(Cell::from(Content::empty()));
-            cells
-                .push(Cell::from(item.body().clone().styled(ListElem::set_depth(Depth))));
+            cells.push(Cell::from(
+                item.body().clone().styled(ListElem::set_depth(Depth(1))),
+            ));
         }
 
         let stroke = None;
@@ -235,19 +236,11 @@ cast! {
     v: Func => Self::Func(v),
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Hash)]
-struct Depth;
-
-cast! {
-    Depth,
-    self => Value::None,
-    _: Value => Self,
-}
+#[derive(Debug, Default, Clone, Copy, PartialEq, Hash)]
+struct Depth(usize);
 
 impl Fold for Depth {
-    type Output = usize;
-
-    fn fold(self, outer: Self::Output) -> Self::Output {
-        outer + 1
+    fn fold(self, outer: Self) -> Self {
+        Self(outer.0 + self.0)
     }
 }
diff --git a/crates/typst/src/model/table.rs b/crates/typst/src/model/table.rs
index ecda0527..256459c7 100644
--- a/crates/typst/src/model/table.rs
+++ b/crates/typst/src/model/table.rs
@@ -194,7 +194,7 @@ pub struct TableElem {
     /// )
     /// ```
     #[fold]
-    #[default(Sides::splat(Abs::pt(5.0).into()))]
+    #[default(Sides::splat(Some(Abs::pt(5.0).into())))]
     pub inset: Sides<Option<Rel<Length>>>,
 
     /// The contents of the table cells.
@@ -378,7 +378,7 @@ impl ResolvableCell for Packed<TableCell> {
         y: usize,
         fill: &Option<Paint>,
         align: Smart<Alignment>,
-        inset: Sides<Rel<Length>>,
+        inset: Sides<Option<Rel<Length>>>,
         styles: StyleChain,
     ) -> Cell {
         let cell = &mut *self;
@@ -397,9 +397,8 @@ impl ResolvableCell for Packed<TableCell> {
             Smart::Auto => cell.align(styles),
         });
         cell.push_inset(Smart::Custom(
-            cell.inset(styles).map_or(inset, |inner| inner.fold(inset)).map(Some),
+            cell.inset(styles).map_or(inset, |inner| inner.fold(inset)),
         ));
-
         Cell { body: self.pack(), fill, colspan }
     }
 
diff --git a/crates/typst/src/text/deco.rs b/crates/typst/src/text/deco.rs
index 3872334d..7873f97b 100644
--- a/crates/typst/src/text/deco.rs
+++ b/crates/typst/src/text/deco.rs
@@ -1,13 +1,10 @@
 use kurbo::{BezPath, Line, ParamCurve};
+use smallvec::smallvec;
 use ttf_parser::{GlyphId, OutlineBuilder};
 
-use ecow::{eco_format, EcoString};
-
 use crate::diag::SourceResult;
 use crate::engine::Engine;
-use crate::foundations::{
-    elem, ty, Content, Fold, Packed, Repr, Show, Smart, StyleChain,
-};
+use crate::foundations::{elem, Content, Packed, Show, Smart, StyleChain};
 use crate::layout::{Abs, Em, Frame, FrameItem, Length, Point, Size};
 use crate::syntax::Span;
 use crate::text::{
@@ -89,7 +86,7 @@ pub struct UnderlineElem {
 impl Show for Packed<UnderlineElem> {
     #[typst_macros::time(name = "underline", span = self.span())]
     fn show(&self, _: &mut Engine, styles: StyleChain) -> SourceResult<Content> {
-        Ok(self.body().clone().styled(TextElem::set_deco(Decoration {
+        Ok(self.body().clone().styled(TextElem::set_deco(smallvec![Decoration {
             line: DecoLine::Underline {
                 stroke: self.stroke(styles).unwrap_or_default(),
                 offset: self.offset(styles),
@@ -97,7 +94,7 @@ impl Show for Packed<UnderlineElem> {
                 background: self.background(styles),
             },
             extent: self.extent(styles),
-        })))
+        }])))
     }
 }
 
@@ -181,7 +178,7 @@ pub struct OverlineElem {
 impl Show for Packed<OverlineElem> {
     #[typst_macros::time(name = "overline", span = self.span())]
     fn show(&self, _: &mut Engine, styles: StyleChain) -> SourceResult<Content> {
-        Ok(self.body().clone().styled(TextElem::set_deco(Decoration {
+        Ok(self.body().clone().styled(TextElem::set_deco(smallvec![Decoration {
             line: DecoLine::Overline {
                 stroke: self.stroke(styles).unwrap_or_default(),
                 offset: self.offset(styles),
@@ -189,7 +186,7 @@ impl Show for Packed<OverlineElem> {
                 background: self.background(styles),
             },
             extent: self.extent(styles),
-        })))
+        }])))
     }
 }
 
@@ -258,7 +255,7 @@ pub struct StrikeElem {
 impl Show for Packed<StrikeElem> {
     #[typst_macros::time(name = "strike", span = self.span())]
     fn show(&self, _: &mut Engine, styles: StyleChain) -> SourceResult<Content> {
-        Ok(self.body().clone().styled(TextElem::set_deco(Decoration {
+        Ok(self.body().clone().styled(TextElem::set_deco(smallvec![Decoration {
             // Note that we do not support evade option for strikethrough.
             line: DecoLine::Strikethrough {
                 stroke: self.stroke(styles).unwrap_or_default(),
@@ -266,7 +263,7 @@ impl Show for Packed<StrikeElem> {
                 background: self.background(styles),
             },
             extent: self.extent(styles),
-        })))
+        }])))
     }
 }
 
@@ -328,14 +325,14 @@ pub struct HighlightElem {
 impl Show for Packed<HighlightElem> {
     #[typst_macros::time(name = "highlight", span = self.span())]
     fn show(&self, _: &mut Engine, styles: StyleChain) -> SourceResult<Content> {
-        Ok(self.body().clone().styled(TextElem::set_deco(Decoration {
+        Ok(self.body().clone().styled(TextElem::set_deco(smallvec![Decoration {
             line: DecoLine::Highlight {
                 fill: self.fill(styles),
                 top_edge: self.top_edge(styles),
                 bottom_edge: self.bottom_edge(styles),
             },
             extent: self.extent(styles),
-        })))
+        }])))
     }
 }
 
@@ -343,28 +340,12 @@ impl Show for Packed<HighlightElem> {
 ///
 /// Can be positioned over, under, or on top of text, or highlight the text with
 /// a background.
-#[ty]
 #[derive(Debug, Clone, Eq, PartialEq, Hash)]
 pub struct Decoration {
     line: DecoLine,
     extent: Abs,
 }
 
-impl Fold for Decoration {
-    type Output = Vec<Self>;
-
-    fn fold(self, mut outer: Self::Output) -> Self::Output {
-        outer.insert(0, self);
-        outer
-    }
-}
-
-impl Repr for Decoration {
-    fn repr(&self) -> EcoString {
-        eco_format!("{self:?}")
-    }
-}
-
 /// A kind of decorative line.
 #[derive(Debug, Clone, Eq, PartialEq, Hash)]
 enum DecoLine {
diff --git a/crates/typst/src/text/mod.rs b/crates/typst/src/text/mod.rs
index 23a685d8..eab01066 100644
--- a/crates/typst/src/text/mod.rs
+++ b/crates/typst/src/text/mod.rs
@@ -32,6 +32,7 @@ use std::fmt::{self, Debug, Formatter};
 
 use ecow::{eco_format, EcoString};
 use rustybuzz::{Feature, Tag};
+use smallvec::SmallVec;
 use ttf_parser::Rect;
 
 use crate::diag::{bail, SourceResult, StrResult};
@@ -39,8 +40,9 @@ use crate::engine::Engine;
 use crate::foundations::Packed;
 use crate::foundations::{
     cast, category, elem, Args, Array, Cast, Category, Construct, Content, Dict, Fold,
-    NativeElement, Never, PlainText, Repr, Resolve, Scope, Set, Smart, StyleChain, Value,
+    NativeElement, Never, PlainText, Repr, Resolve, Scope, Set, Smart, StyleChain,
 };
+use crate::layout::Em;
 use crate::layout::{Abs, Axis, Dir, Length, Rel};
 use crate::model::ParElem;
 use crate::syntax::Spanned;
@@ -214,7 +216,8 @@ pub struct TextElem {
     /// ```
     #[parse(args.named_or_find("size")?)]
     #[fold]
-    #[default(Abs::pt(11.0))]
+    #[default(TextSize(Abs::pt(11.0).into()))]
+    #[resolve]
     #[ghost]
     pub size: TextSize,
 
@@ -628,7 +631,7 @@ pub struct TextElem {
     /// Whether the font style should be inverted.
     #[internal]
     #[fold]
-    #[default(false)]
+    #[default(ItalicToggle(false))]
     #[ghost]
     pub emph: ItalicToggle,
 
@@ -636,7 +639,7 @@ pub struct TextElem {
     #[internal]
     #[fold]
     #[ghost]
-    pub deco: Decoration,
+    pub deco: SmallVec<[Decoration; 1]>,
 
     /// A case transformation that should be applied to the text.
     #[internal]
@@ -763,12 +766,12 @@ pub(crate) fn variant(styles: StyleChain) -> FontVariant {
         TextElem::stretch_in(styles),
     );
 
-    let delta = TextElem::delta_in(styles);
+    let WeightDelta(delta) = TextElem::delta_in(styles);
     variant.weight = variant
         .weight
         .thicken(delta.clamp(i16::MIN as i64, i16::MAX as i64) as i16);
 
-    if TextElem::emph_in(styles) {
+    if TextElem::emph_in(styles).0 {
         variant.style = match variant.style {
             FontStyle::Normal => FontStyle::Italic,
             FontStyle::Italic => FontStyle::Normal,
@@ -784,10 +787,20 @@ pub(crate) fn variant(styles: StyleChain) -> FontVariant {
 pub struct TextSize(pub Length);
 
 impl Fold for TextSize {
+    fn fold(self, outer: Self) -> Self {
+        // Multiply the two linear functions.
+        Self(Length {
+            em: Em::new(self.0.em.get() * outer.0.em.get()),
+            abs: self.0.em.get() * outer.0.abs + self.0.abs,
+        })
+    }
+}
+
+impl Resolve for TextSize {
     type Output = Abs;
 
-    fn fold(self, outer: Self::Output) -> Self::Output {
-        self.0.em.at(outer) + self.0.abs
+    fn resolve(self, styles: StyleChain) -> Self::Output {
+        self.0.resolve(styles)
     }
 }
 
@@ -1056,11 +1069,8 @@ cast! {
 }
 
 impl Fold for FontFeatures {
-    type Output = Self;
-
-    fn fold(mut self, outer: Self::Output) -> Self::Output {
-        self.0.extend(outer.0);
-        self
+    fn fold(self, outer: Self) -> Self {
+        Self(self.0.fold(outer.0))
     }
 }
 
@@ -1133,36 +1143,20 @@ pub(crate) fn features(styles: StyleChain) -> Vec<Feature> {
 
 /// A toggle that turns on and off alternatingly if folded.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
-pub struct ItalicToggle;
-
-cast! {
-    ItalicToggle,
-    self => Value::None,
-    _: Value => Self,
-}
+pub struct ItalicToggle(pub bool);
 
 impl Fold for ItalicToggle {
-    type Output = bool;
-
-    fn fold(self, outer: Self::Output) -> Self::Output {
-        !outer
+    fn fold(self, outer: Self) -> Self {
+        Self(self.0 ^ outer.0)
     }
 }
 
 /// A delta that is summed up when folded.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+#[derive(Debug, Default, Copy, Clone, Eq, PartialEq, Hash)]
 pub struct WeightDelta(pub i64);
 
-cast! {
-    WeightDelta,
-    self => self.0.into_value(),
-    v: i64 => Self(v),
-}
-
 impl Fold for WeightDelta {
-    type Output = i64;
-
-    fn fold(self, outer: Self::Output) -> Self::Output {
-        outer + self.0
+    fn fold(self, outer: Self) -> Self {
+        Self(outer.0 + self.0)
     }
 }
diff --git a/crates/typst/src/text/raw.rs b/crates/typst/src/text/raw.rs
index b032f666..28fcf891 100644
--- a/crates/typst/src/text/raw.rs
+++ b/crates/typst/src/text/raw.rs
@@ -658,11 +658,8 @@ cast! {
 }
 
 impl Fold for SyntaxPaths {
-    type Output = Self;
-
-    fn fold(mut self, outer: Self::Output) -> Self::Output {
-        self.0.extend(outer.0);
-        self
+    fn fold(self, outer: Self) -> Self {
+        Self(self.0.fold(outer.0))
     }
 }
 
diff --git a/crates/typst/src/visualize/shape.rs b/crates/typst/src/visualize/shape.rs
index 89de3398..de1eac16 100644
--- a/crates/typst/src/visualize/shape.rs
+++ b/crates/typst/src/visualize/shape.rs
@@ -114,7 +114,7 @@ pub struct RectElem {
     /// See the [box's documentation]($box.outset) for more details.
     #[resolve]
     #[fold]
-    #[default(Sides::splat(Abs::pt(5.0).into()))]
+    #[default(Sides::splat(Some(Abs::pt(5.0).into())))]
     pub inset: Sides<Option<Rel<Length>>>,
 
     /// How much to expand the rectangle's size without affecting the layout.
@@ -219,7 +219,7 @@ pub struct SquareElem {
     /// [box's documentation]($box.inset) for more details.
     #[resolve]
     #[fold]
-    #[default(Sides::splat(Abs::pt(5.0).into()))]
+    #[default(Sides::splat(Some(Abs::pt(5.0).into())))]
     pub inset: Sides<Option<Rel<Length>>>,
 
     /// How much to expand the square's size without affecting the layout. See
@@ -298,7 +298,7 @@ pub struct EllipseElem {
     /// [box's documentation]($box.inset) for more details.
     #[resolve]
     #[fold]
-    #[default(Sides::splat(Abs::pt(5.0).into()))]
+    #[default(Sides::splat(Some(Abs::pt(5.0).into())))]
     pub inset: Sides<Option<Rel<Length>>>,
 
     /// How much to expand the ellipse's size without affecting the layout. See
@@ -331,10 +331,10 @@ impl LayoutSingle for Packed<EllipseElem> {
             &self.body(styles),
             Axes::new(self.width(styles), self.height(styles)),
             self.fill(styles),
-            self.stroke(styles).map(Sides::splat),
+            self.stroke(styles).map(|s| Sides::splat(Some(s))),
             self.inset(styles),
             self.outset(styles),
-            Corners::splat(Rel::zero()),
+            Corners::splat(None),
             self.span(),
         )
     }
@@ -403,7 +403,7 @@ pub struct CircleElem {
     /// [box's documentation]($box.inset) for more details.
     #[resolve]
     #[fold]
-    #[default(Sides::splat(Abs::pt(5.0).into()))]
+    #[default(Sides::splat(Some(Abs::pt(5.0).into())))]
     pub inset: Sides<Option<Rel<Length>>>,
 
     /// How much to expand the circle's size without affecting the layout. See
@@ -434,10 +434,10 @@ impl LayoutSingle for Packed<CircleElem> {
             &self.body(styles),
             Axes::new(self.width(styles), self.height(styles)),
             self.fill(styles),
-            self.stroke(styles).map(Sides::splat),
+            self.stroke(styles).map(|s| Sides::splat(Some(s))),
             self.inset(styles),
             self.outset(styles),
-            Corners::splat(Rel::zero()),
+            Corners::splat(None),
             self.span(),
         )
     }
@@ -453,18 +453,21 @@ fn layout(
     body: &Option<Content>,
     sizing: Axes<Smart<Rel<Length>>>,
     fill: Option<Paint>,
-    stroke: Smart<Sides<Option<Stroke<Abs>>>>,
-    mut inset: Sides<Rel<Abs>>,
-    outset: Sides<Rel<Abs>>,
-    radius: Corners<Rel<Abs>>,
+    stroke: Smart<Sides<Option<Option<Stroke<Abs>>>>>,
+    inset: Sides<Option<Rel<Abs>>>,
+    outset: Sides<Option<Rel<Abs>>>,
+    radius: Corners<Option<Rel<Abs>>>,
     span: Span,
 ) -> SourceResult<Frame> {
     let resolved = sizing
         .zip_map(regions.base(), |s, r| s.map(|v| v.resolve(styles).relative_to(r)));
 
     let mut frame;
+    let mut inset = inset.unwrap_or_default();
+
     if let Some(child) = body {
         let region = resolved.unwrap_or(regions.base());
+
         if kind.is_round() {
             inset = inset.map(|side| side + Ratio::new(0.5 - SQRT_2 / 4.0));
         }
@@ -507,19 +510,27 @@ fn layout(
     let stroke = match stroke {
         Smart::Auto if fill.is_none() => Sides::splat(Some(FixedStroke::default())),
         Smart::Auto => Sides::splat(None),
-        Smart::Custom(strokes) => strokes.map(|s| s.map(Stroke::unwrap_or_default)),
+        Smart::Custom(strokes) => {
+            strokes.unwrap_or_default().map(|s| s.map(Stroke::unwrap_or_default))
+        }
     };
 
     // Add fill and/or stroke.
     if fill.is_some() || stroke.iter().any(Option::is_some) {
         if kind.is_round() {
-            let outset = outset.relative_to(frame.size());
+            let outset = outset.unwrap_or_default().relative_to(frame.size());
             let size = frame.size() + outset.sum_by_axis();
             let pos = Point::new(-outset.left, -outset.top);
             let shape = ellipse(size, fill, stroke.left);
             frame.prepend(pos, FrameItem::Shape(shape, span));
         } else {
-            frame.fill_and_stroke(fill, stroke, outset, radius, span);
+            frame.fill_and_stroke(
+                fill,
+                stroke,
+                outset.unwrap_or_default(),
+                radius.unwrap_or_default(),
+                span,
+            );
         }
     }
 
diff --git a/crates/typst/src/visualize/stroke.rs b/crates/typst/src/visualize/stroke.rs
index 1d43a7b3..d060ad09 100644
--- a/crates/typst/src/visualize/stroke.rs
+++ b/crates/typst/src/visualize/stroke.rs
@@ -330,6 +330,19 @@ impl<T: Numeric + Repr> Repr for Stroke<T> {
     }
 }
 
+impl<T: Numeric + Fold> Fold for Stroke<T> {
+    fn fold(self, outer: Self) -> Self {
+        Self {
+            paint: self.paint.or(outer.paint),
+            thickness: self.thickness.or(outer.thickness),
+            cap: self.cap.or(outer.cap),
+            join: self.join.or(outer.join),
+            dash: self.dash.or(outer.dash),
+            miter_limit: self.miter_limit.or(outer.miter_limit),
+        }
+    }
+}
+
 impl Resolve for Stroke {
     type Output = Stroke<Abs>;
 
@@ -345,21 +358,6 @@ impl Resolve for Stroke {
     }
 }
 
-impl Fold for Stroke<Abs> {
-    type Output = Self;
-
-    fn fold(self, outer: Self::Output) -> Self::Output {
-        Self {
-            paint: self.paint.or(outer.paint),
-            thickness: self.thickness.or(outer.thickness),
-            cap: self.cap.or(outer.cap),
-            join: self.join.or(outer.join),
-            dash: self.dash.or(outer.dash),
-            miter_limit: self.miter_limit.or(outer.miter_limit),
-        }
-    }
-}
-
 cast! {
     type Stroke,
     thickness: Length => Self {