Refactor `#[elem]` macro (#3303)

1 files changed, 488 insertions, 608 deletions

diff --git a/crates/typst-macros/src/elem.rs b/crates/typst-macros/src/elem.rs
index 91147b8d..a3e2a007 100644
--- a/crates/typst-macros/src/elem.rs
+++ b/crates/typst-macros/src/elem.rs
@@ -1,14 +1,13 @@
 use heck::{ToKebabCase, ToShoutySnakeCase, ToUpperCamelCase};
 use proc_macro2::TokenStream;
-use quote::quote;
+use quote::{format_ident, quote};
 use syn::parse::{Parse, ParseStream};
 use syn::punctuated::Punctuated;
 use syn::{parse_quote, Ident, Result, Token};
 
 use crate::util::{
     determine_name_and_title, documentation, foundations, has_attr, kw, parse_attr,
-    parse_flag, parse_string, parse_string_array, quote_option, validate_attrs,
-    BlockWithReturn,
+    parse_flag, parse_string, parse_string_array, validate_attrs, BlockWithReturn,
 };
 
 /// Expand the `#[elem]` macro.
@@ -26,7 +25,6 @@ struct Elem {
     docs: String,
     vis: syn::Visibility,
     ident: Ident,
-    enum_ident: Ident,
     capabilities: Vec<Ident>,
     fields: Vec<Field>,
 }
@@ -43,72 +41,59 @@ impl Elem {
     fn cannot(&self, name: &str) -> bool {
         !self.can(name)
     }
+}
 
-    /// All fields.
-    ///
-    /// This includes:
-    /// - Fields that are not external and therefore present in the struct.
-    /// - Fields that are ghost fields.
+impl Elem {
+    /// All fields that are not just external.
     fn real_fields(&self) -> impl Iterator<Item = &Field> + Clone {
         self.fields.iter().filter(|field| !field.external)
     }
 
-    /// Fields that are present in the struct.
-    ///
-    /// This includes:
-    /// - Fields that are not external and therefore present in the struct.
-    /// - Fields that are not ghost fields.
-    fn present_fields(&self) -> impl Iterator<Item = &Field> + Clone {
+    /// Fields that are present in the generated struct.
+    fn struct_fields(&self) -> impl Iterator<Item = &Field> + Clone {
         self.real_fields().filter(|field| !field.ghost)
     }
 
-    /// Fields that are inherent to the element.
-    fn inherent_fields(&self) -> impl Iterator<Item = &Field> + Clone {
-        self.real_fields().filter(|field| field.inherent())
+    /// Fields that are relevant for equality.
+    ///
+    /// Synthesized fields are excluded to ensure equality before and after
+    /// synthesis.
+    fn eq_fields(&self) -> impl Iterator<Item = &Field> + Clone {
+        self.struct_fields().filter(|field| !field.synthesized)
     }
 
-    /// Fields that can be set with style rules.
-    ///
-    /// The reason why fields that are `parse` and internal are allowed
-    /// is because it's a pattern used a lot for parsing data from the
-    /// input and then storing it in a field.
+    /// Fields that show up in the documentation.
+    fn doc_fields(&self) -> impl Iterator<Item = &Field> + Clone {
+        self.fields
+            .iter()
+            .filter(|field| !field.internal && !field.synthesized)
+    }
+
+    /// Fields that are relevant for `Construct` impl.
     ///
-    /// This includes:
-    /// - Fields that are not synthesized.
-    /// - Fields that are not inherent and therefore present at all times.
-    /// - Fields that are not internal.
-    fn settable_fields(&self) -> impl Iterator<Item = &Field> + Clone {
+    /// The reason why fields that are `parse` and internal are allowed is
+    /// because it's a pattern used a lot for parsing data from the input and
+    /// then storing it in a field.
+    fn construct_fields(&self) -> impl Iterator<Item = &Field> + Clone {
         self.real_fields().filter(|field| {
-            !field.synthesized
-                && field.settable()
-                && (!field.internal || field.parse.is_some())
+            field.parse.is_some() || (!field.synthesized && !field.internal)
         })
     }
 
-    /// Fields that are visible to the user.
-    ///
-    /// This includes:
-    /// - Fields that are not internal.
-    fn visible_fields(&self) -> impl Iterator<Item = &Field> + Clone {
-        self.real_fields().filter(|field| !field.internal)
+    /// Fields that can be configured with set rules.
+    fn set_fields(&self) -> impl Iterator<Item = &Field> + Clone {
+        self.construct_fields().filter(|field| !field.inherent())
     }
 
-    /// Fields that are relevant for equality.
-    ///
-    /// This includes:
-    /// - Fields that are not synthesized (guarantees equality before and after synthesis).
-    fn eq_fields(&self) -> impl Iterator<Item = &Field> + Clone {
-        self.present_fields().filter(|field| !field.synthesized)
+    /// Fields that can be accessed from the style chain.
+    fn style_fields(&self) -> impl Iterator<Item = &Field> + Clone {
+        self.real_fields()
+            .filter(|field| !field.inherent() && !field.synthesized)
     }
 
-    /// Fields that are relevant for `Construct` impl.
-    ///
-    /// This includes:
-    /// - Fields that are not synthesized.
-    fn construct_fields(&self) -> impl Iterator<Item = &Field> + Clone {
-        self.real_fields().filter(|field| {
-            !field.synthesized && (!field.internal || field.parse.is_some())
-        })
+    /// Fields that are visible to the user.
+    fn visible_fields(&self) -> impl Iterator<Item = &Field> + Clone {
+        self.real_fields().filter(|field| !field.internal && !field.ghost)
     }
 }
 
@@ -132,9 +117,9 @@ struct Field {
     fold: bool,
     internal: bool,
     external: bool,
-    synthesized: bool,
     borrowed: bool,
     ghost: bool,
+    synthesized: bool,
     parse: Option<BlockWithReturn>,
     default: Option<syn::Expr>,
 }
@@ -142,12 +127,7 @@ struct Field {
 impl Field {
     /// Whether the field is present on every instance of the element.
     fn inherent(&self) -> bool {
-        (self.required || self.variadic) && !self.ghost
-    }
-
-    /// Whether the field can be used with set rules.
-    fn settable(&self) -> bool {
-        !self.inherent()
+        self.required || (self.synthesized && self.default.is_some())
     }
 }
 
@@ -191,7 +171,7 @@ fn parse(stream: TokenStream, body: &syn::ItemStruct) -> Result<Elem> {
     };
 
     let fields = named.named.iter().map(parse_field).collect::<Result<Vec<_>>>()?;
-    if fields.iter().any(|field| field.ghost)
+    if fields.iter().any(|field| field.ghost && !field.internal)
         && meta.capabilities.iter().all(|capability| capability != "Construct")
     {
         bail!(body.ident, "cannot have ghost fields and have `Construct` auto generated");
@@ -207,7 +187,6 @@ fn parse(stream: TokenStream, body: &syn::ItemStruct) -> Result<Elem> {
         ident: body.ident.clone(),
         capabilities: meta.capabilities,
         fields,
-        enum_ident: Ident::new(&format!("{}Fields", body.ident), body.ident.span()),
     })
 }
 
@@ -217,7 +196,7 @@ fn parse_field(field: &syn::Field) -> Result<Field> {
     };
 
     if ident == "label" {
-        bail!(ident, "invalid field name");
+        bail!(ident, "invalid field name `label`");
     }
 
     let mut attrs = field.attrs.clone();
@@ -226,43 +205,46 @@ fn parse_field(field: &syn::Field) -> Result<Field> {
     let positional = has_attr(&mut attrs, "positional") || required;
 
     let mut field = Field {
+        ident: ident.clone(),
+        ident_in: format_ident!("{ident}_in"),
+        with_ident: format_ident!("with_{ident}"),
+        push_ident: format_ident!("push_{ident}"),
+        set_ident: format_ident!("set_{ident}"),
+        enum_ident: Ident::new(&ident.to_string().to_upper_camel_case(), ident.span()),
+        const_ident: Ident::new(&ident.to_string().to_shouty_snake_case(), ident.span()),
+        vis: field.vis.clone(),
+        ty: field.ty.clone(),
+        output: field.ty.clone(),
         name: ident.to_string().to_kebab_case(),
         docs: documentation(&attrs),
-        internal: has_attr(&mut attrs, "internal"),
-        external: has_attr(&mut attrs, "external"),
         positional,
         required,
         variadic,
-        borrowed: has_attr(&mut attrs, "borrowed"),
-        synthesized: has_attr(&mut attrs, "synthesized"),
-        fold: has_attr(&mut attrs, "fold"),
         resolve: has_attr(&mut attrs, "resolve"),
+        fold: has_attr(&mut attrs, "fold"),
+        internal: has_attr(&mut attrs, "internal"),
+        external: has_attr(&mut attrs, "external"),
+        borrowed: has_attr(&mut attrs, "borrowed"),
         ghost: has_attr(&mut attrs, "ghost"),
+        synthesized: has_attr(&mut attrs, "synthesized"),
         parse: parse_attr(&mut attrs, "parse")?.flatten(),
         default: parse_attr::<syn::Expr>(&mut attrs, "default")?.flatten(),
-        vis: field.vis.clone(),
-        ident: ident.clone(),
-        ident_in: Ident::new(&format!("{ident}_in"), ident.span()),
-        with_ident: Ident::new(&format!("with_{ident}"), ident.span()),
-        push_ident: Ident::new(&format!("push_{ident}"), ident.span()),
-        set_ident: Ident::new(&format!("set_{ident}"), ident.span()),
-        enum_ident: Ident::new(&ident.to_string().to_upper_camel_case(), ident.span()),
-        const_ident: Ident::new(&ident.to_string().to_shouty_snake_case(), ident.span()),
-        ty: field.ty.clone(),
-        output: field.ty.clone(),
     };
 
-    if field.required && (field.fold || field.resolve) {
-        bail!(ident, "required fields cannot be folded or resolved");
-    }
-
-    if field.required && !field.positional {
-        bail!(ident, "only positional fields can be required");
+    if field.required || field.variadic {
+        if !field.positional {
+            bail!(ident, "inherent fields must be positional");
+        } else if field.fold || field.resolve || field.ghost || field.synthesized {
+            bail!(
+                ident,
+                "inherent fields cannot be fold, resolve, ghost, or synthesized"
+            );
+        }
     }
 
     if field.resolve {
-        let output = &field.output;
-        field.output = parse_quote! { <#output as #foundations::Resolve>::Output };
+        let ty = &field.ty;
+        field.output = parse_quote! { <#ty as #foundations::Resolve>::Output };
     }
 
     validate_attrs(&attrs)?;
@@ -272,57 +254,41 @@ fn parse_field(field: &syn::Field) -> Result<Field> {
 
 /// Produce the element's definition.
 fn create(element: &Elem) -> Result<TokenStream> {
-    let Elem { vis, ident, docs, .. } = element;
+    // The struct itself.
+    let struct_ = create_struct(element);
+    let inherent_impl = create_inherent_impl(element);
 
-    let all = element.real_fields();
-    let present = element.present_fields();
-    let settable = all.clone().filter(|field| !field.synthesized && field.settable());
+    // The enum with the struct's fields.
+    let fields_enum = create_fields_enum(element);
 
-    // The struct itself.
-    let derive_debug = element.cannot("Debug").then(|| quote! { #[derive(Debug)] });
-    let fields = present.clone().map(create_field);
-
-    // Inherent functions.
-    let new = create_new_func(element);
-    let field_methods = all.clone().map(|field| create_field_method(element, field));
-    let field_in_methods =
-        settable.clone().map(|field| create_field_in_method(element, field));
-    let with_field_methods = present.clone().map(create_with_field_method);
-    let push_field_methods = present.clone().map(create_push_field_method);
-    let field_style_methods =
-        settable.clone().map(|field| create_set_field_method(element, field));
+    // The statics with borrowed fields' default values.
+    let default_statics = element
+        .style_fields()
+        .filter(|field| field.borrowed)
+        .map(create_default_static);
 
     // Trait implementations.
     let native_element_impl = create_native_elem_impl(element);
-    let fields_impl = create_fields_impl(element);
-    let capable_impl = create_capable_impl(element);
+    let partial_eq_impl =
+        element.cannot("PartialEq").then(|| create_partial_eq_impl(element));
     let construct_impl =
         element.cannot("Construct").then(|| create_construct_impl(element));
     let set_impl = element.cannot("Set").then(|| create_set_impl(element));
-    let partial_eq_impl =
-        element.cannot("PartialEq").then(|| create_partial_eq_impl(element));
+    let capable_impl = create_capable_impl(element);
+    let fields_impl = create_fields_impl(element);
     let repr_impl = element.cannot("Repr").then(|| create_repr_impl(element));
     let locatable_impl = element.can("Locatable").then(|| create_locatable_impl(element));
+    let into_value_impl = create_into_value_impl(element);
 
+    // We use a const block to create an anonymous scope, as to not leak any
+    // local definitions.
     Ok(quote! {
-        #[doc = #docs]
-        #derive_debug
-        #[derive(Clone, Hash)]
-        #[allow(clippy::derived_hash_with_manual_eq)]
-        #vis struct #ident {
-            #(#fields,)*
-        }
+        #struct_
 
         const _: () = {
-            impl #ident {
-                #new
-                #(#field_methods)*
-                #(#field_in_methods)*
-                #(#with_field_methods)*
-                #(#push_field_methods)*
-                #(#field_style_methods)*
-            }
-
+            #fields_enum
+            #(#default_statics)*
+            #inherent_impl
             #native_element_impl
             #fields_impl
             #capable_impl
@@ -331,183 +297,197 @@ fn create(element: &Elem) -> Result<TokenStream> {
             #partial_eq_impl
             #repr_impl
             #locatable_impl
-
-            impl #foundations::IntoValue for #ident {
-                fn into_value(self) -> #foundations::Value {
-                    #foundations::Value::Content(#foundations::Content::new(self))
-                }
-            }
+            #into_value_impl
         };
     })
 }
 
-/// Create a field declaration.
-fn create_field(field: &Field) -> TokenStream {
-    let Field {
-        ident, ty, docs, required, synthesized, default, ..
-    } = field;
+/// Create the struct definition itself.
+fn create_struct(element: &Elem) -> TokenStream {
+    let Elem { vis, ident, docs, .. } = element;
+
+    let debug = element.cannot("Debug").then(|| quote! { Debug, });
+    let fields = element.struct_fields().map(create_field);
 
-    let ty = required.then(|| quote! { #ty }).unwrap_or_else(|| {
-        if *synthesized && default.is_some() {
-            quote! { #ty }
-        } else {
-            quote! { ::std::option::Option<#ty> }
-        }
-    });
     quote! {
         #[doc = #docs]
-        #ident: #ty
+        #[derive(#debug Clone, Hash)]
+        #[allow(clippy::derived_hash_with_manual_eq)]
+        #vis struct #ident {
+            #(#fields,)*
+        }
     }
 }
 
-/// Create the `new` function for the element.
-fn create_new_func(element: &Elem) -> TokenStream {
-    let relevant = element
-        .fields
-        .iter()
-        .filter(|field| !field.external && !field.synthesized && field.inherent());
-    let params = relevant.clone().map(|Field { ident, ty, .. }| {
+/// Create a field declaration for the struct.
+fn create_field(field: &Field) -> TokenStream {
+    let Field { ident, ty, .. } = field;
+    if field.inherent() {
         quote! { #ident: #ty }
-    });
-    let required = relevant.map(|Field { ident, .. }| {
-        quote! { #ident }
-    });
-    let defaults = element
-        .fields
-        .iter()
-        .filter(|field| {
-            !field.external && !field.inherent() && !field.synthesized && !field.ghost
-        })
-        .map(|Field { ident, .. }| quote! { #ident: None });
-    let default_synthesized = element
-        .fields
-        .iter()
-        .filter(|field| !field.external && field.synthesized && !field.ghost)
-        .map(|Field { ident, default, .. }| {
-            if let Some(expr) = default {
-                quote! { #ident: #expr }
-            } else {
-                quote! { #ident: None }
-            }
-        });
+    } else {
+        quote! { #ident: ::std::option::Option<#ty> }
+    }
+}
+
+/// Creates the element's enum for field identifiers.
+fn create_fields_enum(element: &Elem) -> TokenStream {
+    let variants: Vec<_> = element.real_fields().map(|field| &field.enum_ident).collect();
+    let names: Vec<_> = element.real_fields().map(|field| &field.name).collect();
+    let consts: Vec<_> = element.real_fields().map(|field| &field.const_ident).collect();
+    let repr = (!variants.is_empty()).then(|| quote! { #[repr(u8)] });
 
     quote! {
-        /// Create a new element.
-        pub fn new(#(#params),*) -> Self {
-            Self {
-                #(#required,)*
-                #(#defaults,)*
-                #(#default_synthesized,)*
+        #[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+        #repr
+        pub enum Fields {
+            #(#variants,)*
+        }
+
+        impl Fields {
+            /// Converts the field identifier to the field name.
+            pub fn to_str(self) -> &'static str {
+                match self {
+                    #(Self::#variants => #names,)*
+                }
+            }
+        }
+
+        impl ::std::convert::TryFrom<u8> for Fields {
+            type Error = ();
+
+            fn try_from(value: u8) -> Result<Self, Self::Error> {
+                #(const #consts: u8 = Fields::#variants as u8;)*
+                match value {
+                    #(#consts => Ok(Self::#variants),)*
+                    _ => Err(()),
+                }
+            }
+        }
+
+        impl ::std::str::FromStr for Fields {
+            type Err = ();
+
+            fn from_str(s: &str) -> Result<Self, Self::Err> {
+                match s {
+                    #(#names => Ok(Self::#variants),)*
+                    _ => Err(()),
+                }
+            }
+        }
+
+        impl ::std::fmt::Display for Fields {
+            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+                f.pad(self.to_str())
             }
         }
     }
 }
 
-/// Create a builder pattern method for a field.
-fn create_with_field_method(field: &Field) -> TokenStream {
-    let Field {
-        vis,
-        ident,
-        with_ident,
-        name,
-        ty,
-        synthesized,
-        default,
-        ..
-    } = field;
-    let doc = format!("Set the [`{name}`](Self::{ident}) field.");
+/// Creates a static with a borrowed field's default value.
+fn create_default_static(field: &Field) -> TokenStream {
+    let Field { const_ident, default, ty, .. } = field;
 
-    let set = if field.inherent() || (*synthesized && default.is_some()) {
-        quote! { self.#ident = #ident; }
-    } else {
-        quote! { self.#ident = Some(#ident); }
+    let init = match default {
+        Some(default) => quote! { || #default },
+        None => quote! { ::std::default::Default::default },
     };
+
     quote! {
-        #[doc = #doc]
-        #vis fn #with_ident(mut self, #ident: #ty) -> Self {
-            #set
-            self
+        static #const_ident: ::once_cell::sync::Lazy<#ty> =
+            ::once_cell::sync::Lazy::new(#init);
+    }
+}
+
+/// Create the inherent implementation of the struct.
+fn create_inherent_impl(element: &Elem) -> TokenStream {
+    let Elem { ident, .. } = element;
+
+    let new_func = create_new_func(element);
+    let with_field_methods = element.struct_fields().map(create_with_field_method);
+    let push_field_methods = element.struct_fields().map(create_push_field_method);
+    let field_methods = element.struct_fields().map(create_field_method);
+    let field_in_methods = element.style_fields().map(create_field_in_method);
+    let set_field_methods = element.style_fields().map(create_set_field_method);
+
+    quote! {
+        impl #ident {
+            #new_func
+            #(#with_field_methods)*
+            #(#push_field_methods)*
+            #(#field_methods)*
+            #(#field_in_methods)*
+            #(#set_field_methods)*
         }
     }
 }
 
-/// Create a set-style method for a field.
-fn create_push_field_method(field: &Field) -> TokenStream {
-    let Field {
-        vis,
-        ident,
-        push_ident,
-        name,
-        ty,
-        synthesized,
-        default,
-        ..
-    } = field;
-    let doc = format!("Push the [`{name}`](Self::{ident}) field.");
-    let set = if (field.inherent() && !synthesized) || (*synthesized && default.is_some())
-    {
-        quote! { self.#ident = #ident; }
-    } else {
-        quote! { self.#ident = Some(#ident); }
-    };
+/// Create the `new` function for the element.
+fn create_new_func(element: &Elem) -> TokenStream {
+    let params = element
+        .struct_fields()
+        .filter(|field| field.inherent() && !field.synthesized)
+        .map(|Field { ident, ty, .. }| quote! { #ident: #ty });
+
+    let fields = element.struct_fields().map(|field| {
+        let Field { ident, default, .. } = field;
+        if field.synthesized {
+            if let Some(expr) = default {
+                quote! { #ident: #expr }
+            } else {
+                quote! { #ident: None }
+            }
+        } else if field.inherent() {
+            quote! { #ident }
+        } else {
+            quote! { #ident: None }
+        }
+    });
+
     quote! {
-        #[doc = #doc]
-        #vis fn #push_ident(&mut self, #ident: #ty) {
-            #set
+        /// Create a new instance of the element.
+        pub fn new(#(#params),*) -> Self {
+            Self { #(#fields,)* }
         }
     }
 }
 
-/// Create a setter method for a field.
-fn create_set_field_method(element: &Elem, field: &Field) -> TokenStream {
-    let elem = &element.ident;
-    let Field { vis, ident, set_ident, enum_ident, ty, name, .. } = field;
-    let doc = format!("Create a style property for the `{name}` field.");
+/// Create a builder-style setter method for a field.
+fn create_with_field_method(field: &Field) -> TokenStream {
+    let Field { vis, ident, with_ident, push_ident, name, ty, .. } = field;
+    let doc = format!("Builder-style setter for the [`{name}`](Self::{ident}) field.");
     quote! {
         #[doc = #doc]
-        #vis fn #set_ident(#ident: #ty) -> #foundations::Style {
-            #foundations::Style::Property(#foundations::Property::new(
-                <Self as #foundations::NativeElement>::elem(),
-                <#elem as #foundations::Fields>::Enum::#enum_ident as u8,
-                #ident,
-            ))
+        #vis fn #with_ident(mut self, #ident: #ty) -> Self {
+            self.#push_ident(#ident);
+            self
         }
     }
 }
 
-/// Create a style chain access method for a field.
-fn create_field_in_method(element: &Elem, field: &Field) -> TokenStream {
-    let Field { vis, ident_in, name, output, .. } = field;
-    let doc = format!("Access the `{name}` field in the given style chain.");
-    let access = create_style_chain_access(element, field, quote! { None });
+/// Create a setter method for a field.
+fn create_push_field_method(field: &Field) -> TokenStream {
+    let Field { vis, ident, push_ident, name, ty, .. } = field;
+    let doc = format!("Setter for the [`{name}`](Self::{ident}) field.");
 
-    let output = if field.borrowed {
-        quote! { &#output }
+    let expr = if field.inherent() {
+        quote! { #ident }
     } else {
-        quote! { #output }
+        quote! { Some(#ident) }
     };
 
     quote! {
         #[doc = #doc]
-        #vis fn #ident_in(styles: #foundations::StyleChain) -> #output {
-            #access
+        #vis fn #push_ident(&mut self, #ident: #ty) {
+            self.#ident = #expr;
         }
     }
 }
 
-/// Create an accessor methods for a field.
-fn create_field_method(element: &Elem, field: &Field) -> TokenStream {
-    let Field { vis, docs, ident, output, ghost, .. } = field;
+/// Create an accessor method for a field.
+fn create_field_method(field: &Field) -> TokenStream {
+    let Field { vis, docs, ident, output, .. } = field;
 
-    let inherent = if *ghost {
-        quote! { None }
-    } else {
-        quote! { self.#ident.as_ref() }
-    };
-
-    if (field.inherent() && !field.synthesized)
-        || (field.synthesized && field.default.is_some())
-    {
+    if field.inherent() {
         quote! {
             #[doc = #docs]
             #vis fn #ident(&self) -> &#output {
@@ -522,36 +502,66 @@ fn create_field_method(element: &Elem, field: &Field) -> TokenStream {
                 self.#ident.as_ref().unwrap()
             }
         }
-    } else if field.borrowed {
-        let access = create_style_chain_access(element, field, inherent);
+    } else {
+        let sig = if field.borrowed {
+            quote! { <'a>(&'a self, styles: #foundations::StyleChain<'a>) -> &'a #output }
+        } else {
+            quote! { (&self, styles: #foundations::StyleChain) -> #output }
+        };
 
-        quote! {
-            #[doc = #docs]
-            #vis fn #ident<'a>(&'a self, styles: #foundations::StyleChain<'a>) -> &'a #output {
-                #access
-            }
+        let mut value = create_style_chain_access(field, quote! { self.#ident.as_ref() });
+        if field.resolve {
+            value = quote! { #foundations::Resolve::resolve(#value, styles) };
         }
-    } else {
-        let access = create_style_chain_access(element, field, inherent);
 
         quote! {
             #[doc = #docs]
-            #vis fn #ident(&self, styles: #foundations::StyleChain) -> #output {
-                #access
+            #vis fn #ident #sig {
+                #value
             }
         }
     }
 }
 
-/// Create a style chain access method for a field.
-fn create_style_chain_access(
-    element: &Elem,
-    field: &Field,
-    inherent: TokenStream,
-) -> TokenStream {
-    let elem = &element.ident;
+/// Create a style accessor method for a field.
+fn create_field_in_method(field: &Field) -> TokenStream {
+    let Field { vis, ident_in, name, output, .. } = field;
+    let doc = format!("Access the `{name}` field in the given style chain.");
 
-    let Field { ty, default, enum_ident, .. } = field;
+    let ref_ = field.borrowed.then(|| quote! { & });
+
+    let mut value = create_style_chain_access(field, quote! { None });
+    if field.resolve {
+        value = quote! { #foundations::Resolve::resolve(#value, styles) };
+    }
+
+    quote! {
+        #[doc = #doc]
+        #vis fn #ident_in(styles: #foundations::StyleChain) -> #ref_ #output {
+            #value
+        }
+    }
+}
+
+/// Create a style setter method for a field.
+fn create_set_field_method(field: &Field) -> TokenStream {
+    let Field { vis, ident, set_ident, enum_ident, ty, name, .. } = field;
+    let doc = format!("Create a style property for the `{name}` field.");
+
+    quote! {
+        #[doc = #doc]
+        #vis fn #set_ident(#ident: #ty) -> #foundations::Property {
+            #foundations::Property::new::<Self, _>(
+                Fields::#enum_ident as u8,
+                #ident,
+            )
+        }
+    }
+}
+
+/// Create a style chain access method for a field.
+fn create_style_chain_access(field: &Field, inherent: TokenStream) -> TokenStream {
+    let Field { ty, default, enum_ident, const_ident, .. } = field;
 
     let getter = match (field.fold, field.borrowed) {
         (false, false) => quote! { get },
@@ -559,47 +569,34 @@ fn create_style_chain_access(
         (true, _) => quote! { get_folded },
     };
 
-    let mut default = match default {
-        Some(default) => quote! { #default },
-        None => quote! { ::std::default::Default::default() },
+    let default = if field.borrowed {
+        quote! { || &#const_ident }
+    } else {
+        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);
-        });
-        default = quote! { &DEFAULT };
-    }
-
-    let mut value = quote! {
+    quote! {
         styles.#getter::<#ty>(
             <Self as #foundations::NativeElement>::elem(),
-            <#elem as #foundations::Fields>::Enum::#enum_ident as u8,
+            Fields::#enum_ident as u8,
             #inherent,
-            || #default,
+            #default,
         )
-    };
-
-    if field.resolve {
-        value = quote! { #foundations::Resolve::resolve(#value, styles) };
-    }
-
-    quote! {
-        #init
-        #value
     }
 }
 
-/// Creates the element's `Pack` implementation.
+/// Creates the element's `NativeElement` implementation.
 fn create_native_elem_impl(element: &Elem) -> TokenStream {
     let Elem { name, ident, title, scope, keywords, docs, .. } = element;
 
-    let params = element
-        .fields
-        .iter()
-        .filter(|field| !field.internal && !field.synthesized)
-        .map(create_param_info);
+    let local_name = if element.can("LocalName") {
+        quote! { Some(<#foundations::Packed<#ident> as ::typst::text::LocalName>::local_name) }
+    } else {
+        quote! { None }
+    };
 
     let scope = if *scope {
         quote! { <#ident as #foundations::NativeScope>::scope() }
@@ -607,11 +604,7 @@ fn create_native_elem_impl(element: &Elem) -> TokenStream {
         quote! { #foundations::Scope::new() }
     };
 
-    let local_name = if element.can("LocalName") {
-        quote! { Some(<#foundations::Packed<#ident> as ::typst::text::LocalName>::local_name) }
-    } else {
-        quote! { None }
-    };
+    let params = element.doc_fields().map(create_param_info);
 
     let data = quote! {
         #foundations::NativeElementData {
@@ -622,12 +615,8 @@ fn create_native_elem_impl(element: &Elem) -> TokenStream {
             construct: <#ident as #foundations::Construct>::construct,
             set: <#ident as #foundations::Set>::set,
             vtable:  <#ident as #foundations::Capable>::vtable,
-            field_id: |name|
-                <<#ident as #foundations::Fields>::Enum as ::std::str::FromStr>
-                    ::from_str(name).ok().map(|id| id as u8),
-            field_name: |id|
-                <<#ident as #foundations::Fields>::Enum as ::std::convert::TryFrom<u8>>
-                    ::try_from(id).ok().map(<#ident as #foundations::Fields>::Enum::to_str),
+            field_id: |name| name.parse().ok().map(|id: Fields| id as u8),
+            field_name: |id| id.try_into().ok().map(Fields::to_str),
             local_name: #local_name,
             scope: #foundations::Lazy::new(|| #scope),
             params: #foundations::Lazy::new(|| ::std::vec![#(#params),*])
@@ -644,201 +633,65 @@ fn create_native_elem_impl(element: &Elem) -> TokenStream {
     }
 }
 
-fn create_fields_impl(element: &Elem) -> TokenStream {
-    let Elem { ident, enum_ident, .. } = element;
-
-    let fields_enum = create_fields_enum(element);
+/// Creates a parameter info for a field.
+fn create_param_info(field: &Field) -> TokenStream {
+    let Field {
+        name,
+        docs,
+        positional,
+        variadic,
+        required,
+        default,
+        ty,
+        ..
+    } = field;
 
-    // Fields that can be checked using the `has` method.
-    let field_has_matches = element.visible_fields().map(|field| {
-        let elem = &element.ident;
-        let name = &field.enum_ident;
-        let field_ident = &field.ident;
+    let named = !positional;
+    let settable = !field.inherent();
 
-        if field.ghost {
-            quote! {
-                <#elem as #foundations::Fields>::Enum::#name => false,
-            }
-        } else if field.inherent() || (field.synthesized && field.default.is_some()) {
-            quote! {
-                <#elem as #foundations::Fields>::Enum::#name => true,
-            }
-        } else {
-            quote! {
-                <#elem as #foundations::Fields>::Enum::#name => self.#field_ident.is_some(),
-            }
+    let default = if settable {
+        let default = default
+            .clone()
+            .unwrap_or_else(|| parse_quote! { ::std::default::Default::default() });
+        quote! {
+            Some(|| <#ty as #foundations::IntoValue>::into_value(#default))
         }
-    });
-
-    // Creation of the fields dictionary for inherent fields.
-    let field_dict = element
-        .inherent_fields()
-        .filter(|field| !field.internal)
-        .clone()
-        .map(|field| {
-            let name = &field.name;
-            let field_ident = &field.ident;
-            let field_call = quote! { ::ecow::EcoString::from(#name).into() };
-            quote! {
-                fields.insert(
-                    #field_call,
-                    #foundations::IntoValue::into_value(self.#field_ident.clone())
-                );
-            }
-        });
-
-    // Creation of the fields dictionary for optional fields.
-    let field_opt_dict = element
-        .visible_fields()
-        .filter(|field| !field.inherent() && !field.ghost)
-        .clone()
-        .map(|field| {
-            let name = &field.name;
-            let field_ident = &field.ident;
-            let field_call = quote! { ::ecow::EcoString::from(#name).into() };
-            if field.synthesized && field.default.is_some() {
-                quote! {
-                    fields.insert(
-                        #field_call,
-                        #foundations::IntoValue::into_value(self.#field_ident.clone())
-                    );
-                }
-            } else {
-                quote! {
-                    if let Some(value) = &self.#field_ident {
-                        fields.insert(
-                            #field_call,
-                            #foundations::IntoValue::into_value(value.clone())
-                        );
-                    }
-                }
-            }
-        });
-
-    // Fields that can be accessed using the `field` method.
-    let field_matches = element.visible_fields().map(|field| {
-        let elem = &element.ident;
-        let name = &field.enum_ident;
-        let field_ident = &field.ident;
+    } else {
+        quote! { None }
+    };
 
-        if field.ghost {
-            quote! {
-                <#elem as #foundations::Fields>::Enum::#name => None,
-            }
-        } else if field.inherent() || (field.synthesized && field.default.is_some()) {
-            quote! {
-                <#elem as #foundations::Fields>::Enum::#name => Some(
-                    #foundations::IntoValue::into_value(self.#field_ident.clone())
-                ),
-            }
-        } else {
-            quote! {
-                <#elem as #foundations::Fields>::Enum::#name => {
-                    self.#field_ident.clone().map(#foundations::IntoValue::into_value)
-                }
-            }
-        }
-    });
+    let ty = if *variadic {
+        quote! { <#ty as #foundations::Container>::Inner }
+    } else {
+        quote! { #ty }
+    };
 
     quote! {
-        #fields_enum
-
-        impl #foundations::Fields for #ident {
-            type Enum = #enum_ident;
-
-            fn has(&self, id: u8) -> bool {
-                let Ok(id) = <#ident as #foundations::Fields>::Enum::try_from(id) else {
-                    return false;
-                };
-
-                match id {
-                    #(#field_has_matches)*
-                    _ => false,
-                }
-            }
-
-            fn field(&self, id: u8) -> Option<#foundations::Value> {
-                let id = <#ident as #foundations::Fields>::Enum::try_from(id).ok()?;
-                match id {
-                    #(#field_matches)*
-                    _ => None,
-                }
-            }
-
-            fn fields(&self) -> #foundations::Dict {
-                let mut fields = #foundations::Dict::new();
-                #(#field_dict)*
-                #(#field_opt_dict)*
-                fields
-            }
+        #foundations::ParamInfo {
+            name: #name,
+            docs: #docs,
+            input: <#ty as #foundations::Reflect>::input(),
+            default: #default,
+            positional: #positional,
+            named: #named,
+            variadic: #variadic,
+            required: #required,
+            settable: #settable,
         }
     }
 }
 
-/// Creates the element's enum for field identifiers.
-fn create_fields_enum(element: &Elem) -> TokenStream {
-    let Elem { enum_ident, .. } = element;
-
-    let fields = element.real_fields().collect::<Vec<_>>();
-    let field_names = fields.iter().map(|Field { name, .. }| name).collect::<Vec<_>>();
-    let field_consts = fields
-        .iter()
-        .map(|Field { const_ident, .. }| const_ident)
-        .collect::<Vec<_>>();
-
-    let field_variants = fields
-        .iter()
-        .map(|Field { enum_ident, .. }| enum_ident)
-        .collect::<Vec<_>>();
-
-    let definitions = fields.iter().map(|Field { enum_ident, .. }| {
-        quote! { #enum_ident }
-    });
-
-    let enum_repr = (!fields.is_empty()).then(|| quote! { #[repr(u8)] });
+/// Creates the element's `PartialEq` implementation.
+fn create_partial_eq_impl(element: &Elem) -> TokenStream {
+    let ident = &element.ident;
+    let empty = element.eq_fields().next().is_none().then(|| quote! { true });
+    let fields = element.eq_fields().map(|field| &field.ident);
 
     quote! {
-        #[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
-        #enum_repr
-        pub enum #enum_ident {
-            #(#definitions,)*
-        }
-
-        impl #enum_ident {
-            /// Converts this field identifier to the field name.
-            pub fn to_str(self) -> &'static str {
-                match self {
-                    #(Self::#field_variants => #field_names,)*
-                }
-            }
-        }
-
-        impl ::std::convert::TryFrom<u8> for #enum_ident {
-            type Error = ();
-
-            fn try_from(value: u8) -> Result<Self, Self::Error> {
-                #(const #field_consts: u8 = #enum_ident::#field_variants as u8;)*
-                match value {
-                    #(#field_consts => Ok(Self::#field_variants),)*
-                    _ => Err(()),
-                }
-            }
-        }
-
-        impl ::std::fmt::Display for #enum_ident {
-            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
-                f.pad(self.to_str())
-            }
-        }
-
-        impl ::std::str::FromStr for #enum_ident {
-            type Err = ();
-
-            fn from_str(s: &str) -> Result<Self, Self::Err> {
-                match s {
-                    #(#field_names => Ok(Self::#field_variants),)*
-                    _ => Err(()),
-                }
+        impl PartialEq for #ident {
+            fn eq(&self, other: &Self) -> bool {
+                #empty
+                #(self.#fields == other.#fields)&&*
             }
         }
     }
@@ -847,7 +700,7 @@ fn create_fields_enum(element: &Elem) -> TokenStream {
 /// Creates the element's `Construct` implementation.
 fn create_construct_impl(element: &Elem) -> TokenStream {
     let ident = &element.ident;
-    let pre = element.construct_fields().map(|field| {
+    let setup = element.construct_fields().map(|field| {
         let (prefix, value) = create_field_parser(field);
         let ident = &field.ident;
         quote! {
@@ -856,24 +709,18 @@ fn create_construct_impl(element: &Elem) -> TokenStream {
         }
     });
 
-    let handlers =
-        element
-            .construct_fields()
-            .filter(|field| field.settable())
-            .map(|field| {
-                let push_ident = &field.push_ident;
-                let ident = &field.ident;
-                quote! {
-                    if let Some(value) = #ident {
-                        element.#push_ident(value);
-                    }
-                }
-            });
-
-    let defaults = element
-        .construct_fields()
-        .filter(|field| !field.settable())
-        .map(|field| &field.ident);
+    let fields = element.struct_fields().map(|field| {
+        let Field { ident, default, .. } = field;
+        if field.synthesized {
+            if let Some(expr) = default {
+                quote! { #ident: #expr }
+            } else {
+                quote! { #ident: None }
+            }
+        } else {
+            quote! { #ident }
+        }
+    });
 
     quote! {
         impl #foundations::Construct for #ident {
@@ -881,13 +728,8 @@ fn create_construct_impl(element: &Elem) -> TokenStream {
                 engine: &mut ::typst::engine::Engine,
                 args: &mut #foundations::Args,
             ) -> ::typst::diag::SourceResult<#foundations::Content> {
-                #(#pre)*
-
-                let mut element = Self::new(#(#defaults),*);
-
-                #(#handlers)*
-
-                Ok(#foundations::Content::new(element))
+                #(#setup)*
+                Ok(#foundations::Content::new(Self { #(#fields),* }))
             }
         }
     }
@@ -896,7 +738,7 @@ fn create_construct_impl(element: &Elem) -> TokenStream {
 /// Creates the element's `Set` implementation.
 fn create_set_impl(element: &Elem) -> TokenStream {
     let ident = &element.ident;
-    let handlers = element.settable_fields().map(|field| {
+    let handlers = element.set_fields().map(|field| {
         let set_ident = &field.set_ident;
         let (prefix, value) = create_field_parser(field);
         quote! {
@@ -921,55 +763,38 @@ fn create_set_impl(element: &Elem) -> TokenStream {
     }
 }
 
-/// Creates the element's `Locatable` implementation.
-fn create_locatable_impl(element: &Elem) -> TokenStream {
-    let ident = &element.ident;
-    quote! { impl ::typst::introspection::Locatable for #foundations::Packed<#ident> {} }
-}
-
-/// Creates the element's `PartialEq` implementation.
-fn create_partial_eq_impl(element: &Elem) -> TokenStream {
-    let ident = &element.ident;
-    let all = element.eq_fields().map(|field| &field.ident).collect::<Vec<_>>();
-
-    let empty = all.is_empty().then(|| quote! { true });
-    quote! {
-        impl PartialEq for #ident {
-            fn eq(&self, other: &Self) -> bool {
-                #empty
-                #(self.#all == other.#all)&&*
-            }
-        }
+/// Create argument parsing code for a field.
+fn create_field_parser(field: &Field) -> (TokenStream, TokenStream) {
+    if let Some(BlockWithReturn { prefix, expr }) = &field.parse {
+        return (quote! { #(#prefix);* }, quote! { #expr });
     }
-}
 
-/// Creates the element's `Repr` implementation.
-fn create_repr_impl(element: &Elem) -> TokenStream {
-    let ident = &element.ident;
-    let repr_format = format!("{}{{}}", element.name);
-    quote! {
-        impl #foundations::Repr for #ident {
-            fn repr(&self) -> ::ecow::EcoString {
-                let fields = #foundations::Fields::fields(self).into_iter()
-                    .map(|(name, value)| ::ecow::eco_format!("{}: {}", name, value.repr()))
-                    .collect::<Vec<_>>();
-                ::ecow::eco_format!(#repr_format, #foundations::repr::pretty_array_like(&fields, false))
-            }
-        }
-    }
+    let name = &field.name;
+    let value = if field.variadic {
+        quote! { args.all()? }
+    } else if field.required {
+        quote! { args.expect(#name)? }
+    } else if field.positional {
+        quote! { args.find()? }
+    } else {
+        quote! { args.named(#name)? }
+    };
+
+    (quote! {}, value)
 }
 
 /// Creates the element's casting vtable.
 fn create_capable_impl(element: &Elem) -> TokenStream {
     // Forbidden capabilities (i.e capabilities that are not object safe).
     const FORBIDDEN: &[&str] =
-        &["Construct", "PartialEq", "Hash", "LocalName", "Repr", "Debug"];
+        &["Debug", "PartialEq", "Hash", "Construct", "Set", "Repr", "LocalName"];
 
     let ident = &element.ident;
     let relevant = element
         .capabilities
         .iter()
         .filter(|&ident| !FORBIDDEN.contains(&(&ident.to_string() as &str)));
+
     let checks = relevant.map(|capability| {
         quote! {
             if capability == ::std::any::TypeId::of::<dyn #capability>() {
@@ -993,67 +818,122 @@ fn create_capable_impl(element: &Elem) -> TokenStream {
     }
 }
 
-/// Creates a parameter info for a field.
-fn create_param_info(field: &Field) -> TokenStream {
-    let Field {
-        name,
-        docs,
-        positional,
-        variadic,
-        required,
-        default,
-        ty,
-        ..
-    } = field;
-    let named = !positional;
-    let settable = field.settable();
-    let default = quote_option(&settable.then(|| {
-        let default = default
-            .clone()
-            .unwrap_or_else(|| parse_quote! { ::std::default::Default::default() });
-        quote! {
-            || {
-                let typed: #ty = #default;
-                #foundations::IntoValue::into_value(typed)
+/// Creates the element's `Fields` implementation.
+fn create_fields_impl(element: &Elem) -> TokenStream {
+    let into_value = quote! { #foundations::IntoValue::into_value };
+
+    // Fields that can be checked using the `has` method.
+    let has_arms = element.visible_fields().map(|field| {
+        let Field { enum_ident, ident, .. } = field;
+
+        let expr = if field.inherent() {
+            quote! { true }
+        } else {
+            quote! { self.#ident.is_some() }
+        };
+
+        quote! { Fields::#enum_ident => #expr }
+    });
+
+    // Fields that can be accessed using the `field` method.
+    let field_arms = element.visible_fields().map(|field| {
+        let Field { enum_ident, ident, .. } = field;
+
+        let expr = if field.inherent() {
+            quote! { Some(#into_value(self.#ident.clone())) }
+        } else {
+            quote! { self.#ident.clone().map(#into_value) }
+        };
+
+        quote! { Fields::#enum_ident => #expr }
+    });
+
+    // Creation of the `fields` dictionary for inherent fields.
+    let field_inserts = element.visible_fields().map(|field| {
+        let Field { ident, name, .. } = field;
+        let string = quote! { #name.into() };
+
+        if field.inherent() {
+            quote! {
+                fields.insert( #string, #into_value(self.#ident.clone()));
+            }
+        } else {
+            quote! {
+                if let Some(value) = &self.#ident {
+                    fields.insert(#string, #into_value(value.clone()));
+                }
             }
         }
-    }));
-    let ty = if *variadic {
-        quote! { <#ty as #foundations::Container>::Inner }
-    } else {
-        quote! { #ty }
-    };
+    });
+
+    let Elem { ident, .. } = element;
+
     quote! {
-        #foundations::ParamInfo {
-            name: #name,
-            docs: #docs,
-            input: <#ty as #foundations::Reflect>::input(),
-            default: #default,
-            positional: #positional,
-            named: #named,
-            variadic: #variadic,
-            required: #required,
-            settable: #settable,
+        impl #foundations::Fields for #ident {
+            type Enum = Fields;
+
+            fn has(&self, id: u8) -> bool {
+                let Ok(id) = <#ident as #foundations::Fields>::Enum::try_from(id) else {
+                    return false;
+                };
+
+                match id {
+                    #(#has_arms,)*
+                    _ => false,
+                }
+            }
+
+            fn field(&self, id: u8) -> Option<#foundations::Value> {
+                let id = <#ident as #foundations::Fields>::Enum::try_from(id).ok()?;
+                match id {
+                    #(#field_arms,)*
+                    _ => None,
+                }
+            }
+
+            fn fields(&self) -> #foundations::Dict {
+                let mut fields = #foundations::Dict::new();
+                #(#field_inserts)*
+                fields
+            }
         }
     }
 }
 
-/// Create argument parsing code for a field.
-fn create_field_parser(field: &Field) -> (TokenStream, TokenStream) {
-    if let Some(BlockWithReturn { prefix, expr }) = &field.parse {
-        return (quote! { #(#prefix);* }, quote! { #expr });
+/// Creates the element's `Repr` implementation.
+fn create_repr_impl(element: &Elem) -> TokenStream {
+    let ident = &element.ident;
+    let repr_format = format!("{}{{}}", element.name);
+    quote! {
+        impl #foundations::Repr for #ident {
+            fn repr(&self) -> ::ecow::EcoString {
+                let fields = #foundations::Fields::fields(self)
+                    .into_iter()
+                    .map(|(name, value)| ::ecow::eco_format!("{}: {}", name, value.repr()))
+                    .collect::<Vec<_>>();
+                ::ecow::eco_format!(
+                    #repr_format,
+                    #foundations::repr::pretty_array_like(&fields, false),
+                )
+            }
+        }
     }
+}
 
-    let name = &field.name;
-    let value = if field.variadic {
-        quote! { args.all()? }
-    } else if field.required {
-        quote! { args.expect(#name)? }
-    } else if field.positional {
-        quote! { args.find()? }
-    } else {
-        quote! { args.named(#name)? }
-    };
+/// Creates the element's `Locatable` implementation.
+fn create_locatable_impl(element: &Elem) -> TokenStream {
+    let ident = &element.ident;
+    quote! { impl ::typst::introspection::Locatable for #foundations::Packed<#ident> {} }
+}
 
-    (quote! {}, value)
+/// Creates the element's `IntoValue` implementation.
+fn create_into_value_impl(element: &Elem) -> TokenStream {
+    let Elem { ident, .. } = element;
+    quote! {
+        impl #foundations::IntoValue for #ident {
+            fn into_value(self) -> #foundations::Value {
+                #foundations::Value::Content(#foundations::Content::new(self))
+            }
+        }
+    }
 }