Derive Cast for enums

Cargo.lock

@@ -1269,6 +1269,7 @@ dependencies = [
 name = "typst-macros"
 version = "0.0.0"
 dependencies = [
+ "heck",
  "proc-macro2",
  "quote",
  "syn",

library/src/layout/par.rs

@@ -193,30 +193,15 @@ impl Resolve for HorizontalAlign {
 }
 
 /// How to determine line breaks in a paragraph.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash, Cast)]
 pub enum Linebreaks {
     /// Determine the line breaks in a simple first-fit style.
     Simple,
     /// Optimize the line breaks for the whole paragraph.
-    Optimized,
-}
-
-cast_from_value! {
-    Linebreaks,
-    /// Determine the line breaks in a simple first-fit style.
-    "simple" => Self::Simple,
-    /// Optimize the line breaks for the whole paragraph.
     ///
     /// Typst will try to produce more evenly filled lines of text by
     /// considering the whole paragraph when calculating line breaks.
-    "optimized" => Self::Optimized,
-}
-
-cast_to_value! {
-    v: Linebreaks => Value::from(match v {
-        Linebreaks::Simple => "simple",
-        Linebreaks::Optimized => "optimized",
-    })
+    Optimized,
 }
 
 /// A paragraph break.

library/src/math/matrix.rs

@@ -169,12 +169,22 @@ impl LayoutMath for CasesNode {
 }
 
 /// A vector / matrix delimiter.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash, Cast)]
 pub enum Delimiter {
+    /// Delimit with parentheses.
+    #[string("(")]
     Paren,
+    /// Delimit with brackets.
+    #[string("[")]
     Bracket,
+    /// Delimit with curly braces.
+    #[string("{")]
     Brace,
+    /// Delimit with vertical bars.
+    #[string("|")]
     Bar,
+    /// Delimit with double vertical bars.
+    #[string("||")]
     DoubleBar,
 }
 
@@ -202,30 +212,6 @@ impl Delimiter {
     }
 }
 
-cast_from_value! {
-    Delimiter,
-    /// Delimit with parentheses.
-    "(" => Self::Paren,
-    /// Delimit with brackets.
-    "[" => Self::Bracket,
-    /// Delimit with curly braces.
-    "{" => Self::Brace,
-    /// Delimit with vertical bars.
-    "|" => Self::Bar,
-    /// Delimit with double vertical bars.
-    "||" => Self::DoubleBar,
-}
-
-cast_to_value! {
-    v: Delimiter => Value::from(match v {
-        Delimiter::Paren => "(",
-        Delimiter::Bracket => "[",
-        Delimiter::Brace => "{",
-        Delimiter::Bar => "|",
-        Delimiter::DoubleBar => "||",
-    })
-}
-
 /// Layout the inner contents of a vector.
 fn layout_vec_body(
     ctx: &mut MathContext,

library/src/text/misc.rs

@@ -246,7 +246,7 @@ cast_from_value! {
 }
 
 /// A case transformation on text.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash, Cast)]
 pub enum Case {
     /// Everything is lowercased.
     Lower,
@@ -264,19 +264,6 @@ impl Case {
     }
 }
 
-cast_from_value! {
-    Case,
-    "lower" => Self::Lower,
-    "upper" => Self::Upper,
-}
-
-cast_to_value! {
-    v: Case => Value::from(match v {
-        Case::Lower => "lower",
-        Case::Upper => "upper",
-    })
-}
-
 /// Display text in small capitals.
 ///
 /// _Note:_ This enables the OpenType `smcp` feature for the font. Not all fonts

library/src/text/mod.rs

@@ -686,53 +686,23 @@ cast_to_value! {
 }
 
 /// Which kind of numbers / figures to select.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash, Cast)]
 pub enum NumberType {
-    /// Numbers that fit well with capital text. ("lnum")
+    /// Numbers that fit well with capital text (the OpenType `lnum`
+    /// font feature).
     Lining,
-    /// Numbers that fit well into a flow of upper- and lowercase text. ("onum")
+    /// Numbers that fit well into a flow of upper- and lowercase text (the
+    /// OpenType `onum` font feature).
     OldStyle,
 }
 
-cast_from_value! {
-    NumberType,
-    /// Numbers that fit well with capital text (the OpenType `lnum`
-    /// font feature).
-    "lining" => Self::Lining,
-    // Numbers that fit well into a flow of upper- and lowercase text (the
-    /// OpenType `onum` font feature).
-    "old-style" => Self::OldStyle,
-}
-
-cast_to_value! {
-    v: NumberType => Value::from(match v {
-        NumberType::Lining => "lining",
-        NumberType::OldStyle => "old-style",
-    })
-}
-
 /// The width of numbers / figures.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash, Cast)]
 pub enum NumberWidth {
-    /// Number widths are glyph specific. ("pnum")
-    Proportional,
-    /// All numbers are of equal width / monospaced. ("tnum")
-    Tabular,
-}
-
-cast_from_value! {
-    NumberWidth,
     /// Numbers with glyph-specific widths (the OpenType `pnum` font feature).
-    "proportional" => Self::Proportional,
+    Proportional,
     /// Numbers of equal width (the OpenType `tnum` font feature).
-    "tabular" => Self::Tabular,
-}
-
-cast_to_value! {
-    v: NumberWidth => Value::from(match v {
-        NumberWidth::Proportional => "proportional",
-        NumberWidth::Tabular => "tabular",
-    })
+    Tabular,
 }
 
 /// OpenType font features settings.

library/src/visualize/image.rs

@@ -113,33 +113,15 @@ impl Layout for ImageNode {
 }
 
 /// How an image should adjust itself to a given area.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash, Cast)]
 pub enum ImageFit {
-    /// The image should completely cover the area.
+    /// The image should completely cover the area. This is the default.
     Cover,
     /// The image should be fully contained in the area.
     Contain,
-    /// The image should be stretched so that it exactly fills the area.
-    Stretch,
-}
-
-cast_from_value! {
-    ImageFit,
-    /// The image should completely cover the area. This is the default.
-    "cover" => Self::Cover,
-    /// The image should be fully contained in the area.
-    "contain" => Self::Contain,
     /// The image should be stretched so that it exactly fills the area, even if
     /// this means that the image will be distorted.
-    "stretch" => Self::Stretch,
-}
-
-cast_to_value! {
-    fit: ImageFit => Value::from(match fit {
-        ImageFit::Cover => "cover",
-        ImageFit::Contain => "contain",
-        ImageFit::Stretch => "stretch",
-    })
+    Stretch,
 }
 
 /// Load an image from a path.

macros/Cargo.toml

@@ -15,3 +15,4 @@ proc-macro2 = "1"
 quote = "1"
 syn = { version = "1", features = ["full", "extra-traits"] }
 unscanny = "0.1"
+heck = "0.4"

macros/src/castable.rs

@@ -1,5 +1,67 @@
 use super::*;
 
+/// Expand the `#[derive(Cast)]` macro.
+pub fn cast(item: DeriveInput) -> Result<TokenStream> {
+    let ty = &item.ident;
+
+    let syn::Data::Enum(data) = &item.data else {
+        bail!(item, "only enums are supported");
+    };
+
+    let mut variants = vec![];
+    for variant in &data.variants {
+        if let Some((_, expr)) = &variant.discriminant {
+            bail!(expr, "explicit discriminant is not allowed");
+        }
+
+        let string = if let Some(attr) =
+            variant.attrs.iter().find(|attr| attr.path.is_ident("string"))
+        {
+            attr.parse_args::<syn::LitStr>()?.value()
+        } else {
+            kebab_case(&variant.ident)
+        };
+
+        variants.push(Variant {
+            ident: variant.ident.clone(),
+            string,
+            docs: documentation(&variant.attrs),
+        });
+    }
+
+    let strs_to_variants = variants.iter().map(|Variant { ident, string, docs }| {
+        quote! {
+            #[doc = #docs]
+            #string => Self::#ident
+        }
+    });
+
+    let variants_to_strs = variants.iter().map(|Variant { ident, string, .. }| {
+        quote! {
+            #ty::#ident => #string
+        }
+    });
+
+    Ok(quote! {
+        ::typst::eval::cast_from_value! {
+            #ty,
+            #(#strs_to_variants),*
+        }
+
+        ::typst::eval::cast_to_value! {
+            v: #ty => ::typst::eval::Value::from(match v {
+                #(#variants_to_strs),*
+            })
+        }
+    })
+}
+
+struct Variant {
+    ident: Ident,
+    string: String,
+    docs: String,
+}
+
 /// Expand the `cast_from_value!` macro.
 pub fn cast_from_value(stream: TokenStream) -> Result<TokenStream> {
     let castable: Castable = syn::parse2(stream)?;

macros/src/lib.rs

@@ -15,7 +15,7 @@ use quote::quote;
 use syn::ext::IdentExt;
 use syn::parse::{Parse, ParseStream, Parser};
 use syn::punctuated::Punctuated;
-use syn::{parse_quote, Ident, Result, Token};
+use syn::{parse_quote, DeriveInput, Ident, Result, Token};
 
 use self::util::*;
 
@@ -35,6 +35,15 @@ pub fn node(stream: BoundaryStream, item: BoundaryStream) -> BoundaryStream {
         .into()
 }
 
+/// Implement `Cast` for an enum.
+#[proc_macro_derive(Cast, attributes(string))]
+pub fn cast(item: BoundaryStream) -> BoundaryStream {
+    let item = syn::parse_macro_input!(item as DeriveInput);
+    castable::cast(item)
+        .unwrap_or_else(|err| err.to_compile_error())
+        .into()
+}
+
 /// Implement `Cast` and optionally `Type` for a type.
 #[proc_macro]
 pub fn cast_from_value(stream: BoundaryStream) -> BoundaryStream {

macros/src/util.rs

@@ -1,3 +1,5 @@
+use heck::ToKebabCase;
+
 use super::*;
 
 /// Return an error at the given item.
@@ -55,7 +57,7 @@ pub fn validate_attrs(attrs: &[syn::Attribute]) -> Result<()> {
 
 /// Convert an identifier to a kebab-case string.
 pub fn kebab_case(name: &Ident) -> String {
-    name.to_string().to_lowercase().replace('_', "-")
+    name.to_string().to_kebab_case()
 }
 
 /// Extract documentation comments from an attribute list.

src/eval/cast.rs

@@ -1,4 +1,4 @@
-pub use typst_macros::{cast_from_value, cast_to_value};
+pub use typst_macros::{cast_from_value, cast_to_value, Cast};
 
 use std::num::{NonZeroI64, NonZeroUsize};
 use std::ops::Add;

src/font/mod.rs

@@ -12,7 +12,7 @@ use std::sync::Arc;
 
 use ttf_parser::GlyphId;
 
-use crate::eval::{cast_from_value, cast_to_value, Value};
+use crate::eval::Cast;
 use crate::geom::Em;
 use crate::util::Buffer;
 
@@ -231,12 +231,9 @@ pub struct LineMetrics {
 }
 
 /// Identifies a vertical metric of a font.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash, Cast)]
 pub enum VerticalFontMetric {
-    /// The typographic ascender.
-    ///
-    /// Corresponds to the typographic ascender from the `OS/2` table if present
-    /// and falls back to the ascender from the `hhea` table otherwise.
+    /// The font's ascender, which typically exceeds the height of all glyphs.
     Ascender,
     /// The approximate height of uppercase letters.
     CapHeight,
@@ -244,33 +241,6 @@ pub enum VerticalFontMetric {
     XHeight,
     /// The baseline on which the letters rest.
     Baseline,
-    /// The typographic descender.
-    ///
-    /// Corresponds to the typographic descender from the `OS/2` table if
-    /// present and falls back to the descender from the `hhea` table otherwise.
+    /// The font's ascender, which typically exceeds the depth of all glyphs.
     Descender,
 }
-
-cast_from_value! {
-    VerticalFontMetric,
-    /// The font's ascender, which typically exceeds the height of all glyphs.
-    "ascender" => Self::Ascender,
-    /// The approximate height of uppercase letters.
-    "cap-height" => Self::CapHeight,
-    /// The approximate height of non-ascending lowercase letters.
-    "x-height" => Self::XHeight,
-    /// The baseline on which the letters rest.
-    "baseline" => Self::Baseline,
-    /// The font's ascender, which typically exceeds the depth of all glyphs.
-    "descender" => Self::Descender,
-}
-
-cast_to_value! {
-    v: VerticalFontMetric => Value::from(match v {
-        VerticalFontMetric::Ascender => "ascender",
-        VerticalFontMetric::CapHeight => "cap-height",
-        VerticalFontMetric::XHeight => "x-height",
-        VerticalFontMetric::Baseline => "baseline" ,
-        VerticalFontMetric::Descender => "descender",
-    })
-}

src/font/variant.rs

@@ -2,7 +2,7 @@ use std::fmt::{self, Debug, Formatter};
 
 use serde::{Deserialize, Serialize};
 
-use crate::eval::{cast_from_value, cast_to_value, Value};
+use crate::eval::{cast_from_value, cast_to_value, Cast, Value};
 use crate::geom::Ratio;
 
 /// Properties that distinguish a font from other fonts in the same family.
@@ -32,7 +32,7 @@ impl Debug for FontVariant {
 
 /// The style of a font.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
-#[derive(Serialize, Deserialize)]
+#[derive(Serialize, Deserialize, Cast)]
 #[serde(rename_all = "kebab-case")]
 pub enum FontStyle {
     /// The default, typically upright style.
@@ -62,24 +62,6 @@ impl Default for FontStyle {
     }
 }
 
-cast_from_value! {
-    FontStyle,
-    /// The default, typically upright style.
-    "normal" => Self::Normal,
-    /// A cursive style with custom letterform.
-    "italic" => Self::Italic,
-    /// Just a slanted version of the normal style.
-    "oblique" => Self::Oblique,
-}
-
-cast_to_value! {
-    v: FontStyle => Value::from(match v {
-        FontStyle::Normal => "normal",
-        FontStyle::Italic => "italic",
-        FontStyle::Oblique => "oblique",
-    })
-}
-
 /// The weight of a font.
 #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
 #[derive(Serialize, Deserialize)]