Refactor function parsing ♻

src/func.rs

@@ -2,25 +2,31 @@
 
 /// Useful things for creating functions.
 pub mod prelude {
+    pub use async_trait::async_trait;
     pub use crate::layout::prelude::*;
+    pub use crate::layout::Commands;
     pub use crate::layout::Command::{self, *};
     pub use crate::style::*;
-    pub use crate::syntax::prelude::*;
+    pub use crate::syntax::expr::*;
-    pub use super::{expect_no_body, parse_maybe_body, OptionExt};
+    pub use crate::syntax::parsing::{
+        parse, FuncArgs, FuncBody, FuncCall, FuncHeader, ParseState,
+    };
+    pub use crate::syntax::span::{Span, SpanVec, Spanned};
+    pub use crate::syntax::tree::{DynamicNode, SyntaxNode, SyntaxTree};
+    pub use crate::syntax::value::*;
+    pub use crate::{Pass, Feedback};
+    pub use super::*;
 }
 
-use crate::syntax::parsing::{parse, ParseState};
+use prelude::*;
-use crate::syntax::span::{Span, Spanned};
-use crate::syntax::tree::SyntaxTree;
-use crate::Feedback;
 
 /// Extra methods on `Option`s used for function argument parsing.
 pub trait OptionExt<T>: Sized {
-    /// Calls `f` with `val` if this is `Some(val)`.
+    /// Call `f` with `val` if this is `Some(val)`.
     fn with(self, f: impl FnOnce(T));
 
-    /// Reports an error about a missing argument with the given name and span
+    /// Report an error about a missing argument with the given name and span if
-    /// if the option is `None`.
+    /// the option is `None`.
     fn or_missing(self, span: Span, arg: &str, f: &mut Feedback) -> Self;
 }
 
@@ -39,8 +45,19 @@ impl<T> OptionExt<T> for Option<T> {
     }
 }
 
-/// Parses a function's body if there is one or returns `None` otherwise.
+/// Generate `unexpected argument` errors for all remaining arguments.
-pub fn parse_maybe_body(
+pub fn drain_args(args: FuncArgs, f: &mut Feedback) {
+    for arg in args.pos.0 {
+        error!(@f, arg.span, "unexpected argument");
+    }
+
+    for arg in args.key.0 {
+        error!(@f, arg.span, "unexpected argument");
+    }
+}
+
+/// Parse a function's body if there is one or return `None` otherwise.
+pub fn parse_body_maybe(
     body: Option<Spanned<&str>>,
     state: &ParseState,
     f: &mut Feedback,
@@ -52,106 +69,9 @@ pub fn parse_maybe_body(
     })
 }
 
-/// Generates an error if there is function body even though none was expected.
+/// Generate an error if there is function body even though none was expected.
 pub fn expect_no_body(body: Option<Spanned<&str>>, f: &mut Feedback) {
     if let Some(body) = body {
         error!(@f, body.span, "unexpected body");
     }
 }
-
-/// Implement a custom function concisely.
-///
-/// # Examples
-/// Look at the source code of the `library` module for examples on how the
-/// macro works.
-#[macro_export]
-macro_rules! function {
-    // Entry point.
-    ($(#[$outer:meta])* $v:vis $storage:ident $name:ident $($r:tt)*) => {
-        function!(@def($name) $(#[$outer])* $v $storage $name $($r)*);
-    };
-    (@def($name:ident) $definition:item $($r:tt)*) => {
-        $definition
-        function!(@meta($name) $($r)*);
-    };
-
-    // Metadata.
-    (@meta($name:ident) type Meta = $meta:ty; $($r:tt)*) => {
-        function!(@parse($name, $meta) $($r)*);
-    };
-    (@meta($name:ident) $($r:tt)*) => {
-        function!(@parse($name, ()) $($r)*);
-    };
-
-    // Parse trait.
-    (@parse($($a:tt)*) parse(default) $($r:tt)*) => {
-        function!(@parse($($a)*) parse(_h, _b, _c, _f, _m) { Default::default() } $($r)*);
-    };
-    (@parse($($a:tt)*) parse($h:ident, $b:ident, $c:ident, $f:ident) $($r:tt)* ) => {
-        function!(@parse($($a)*) parse($h, $b, $c, $f, _metadata) $($r)*);
-    };
-    (@parse($name:ident, $meta:ty) parse(
-        $header:ident,
-        $body:ident,
-        $state:ident,
-        $feedback:ident,
-        $metadata:ident
-    ) $code:block $($r:tt)*) => {
-        impl $crate::syntax::parsing::ParseCall for $name {
-            type Meta = $meta;
-
-            fn parse(
-                #[allow(unused)] mut call: $crate::syntax::parsing::FuncCall,
-                #[allow(unused)] $state: &$crate::syntax::parsing::ParseState,
-                #[allow(unused)] $metadata: Self::Meta,
-            ) -> $crate::Pass<Self>
-            where
-                Self: Sized,
-            {
-                let mut feedback = $crate::Feedback::new();
-                #[allow(unused)] let $header = &mut call.header;
-                #[allow(unused)] let $body = call.body;
-                #[allow(unused)] let $feedback = &mut feedback;
-
-                let func = $code;
-
-                for arg in call.header.args.pos.0 {
-                    error!(@feedback, arg.span, "unexpected argument");
-                }
-
-                for arg in call.header.args.key.0 {
-                    error!(@feedback, arg.span, "unexpected argument");
-                }
-
-                $crate::Pass::new(func, feedback)
-            }
-        }
-
-        function!(@layout($name) $($r)*);
-    };
-
-    (@layout($name:ident) layout(
-        $this:ident,
-        $ctx:ident,
-        $feedback:ident
-    ) $code:block) => {
-        impl $crate::layout::Layout for $name {
-            fn layout<'a, 'b, 't>(
-                #[allow(unused)] &'a $this,
-                #[allow(unused)] mut $ctx: $crate::layout::LayoutContext<'b>,
-            ) -> $crate::DynFuture<'t, $crate::Pass<$crate::layout::Commands<'a>>>
-            where
-                'a: 't,
-                'b: 't,
-                Self: 't,
-            {
-                Box::pin(async move {
-                    let mut feedback = $crate::Feedback::new();
-                    #[allow(unused)] let $feedback = &mut feedback;
-                    let commands = $code;
-                    $crate::Pass::new(commands, feedback)
-                })
-            }
-        }
-    };
-}

src/layout/mod.rs

@@ -10,7 +10,9 @@ mod tree;
 /// Basic types used across the layouting engine.
 pub mod prelude {
     pub use super::primitive::*;
-    pub use super::layout;
+    pub use super::{
+        BoxLayout, layout, Layout, LayoutContext, LayoutSpace, MultiLayout,
+    };
     pub use Dir::*;
     pub use GenAlign::*;
     pub use GenAxis::*;
@@ -46,7 +48,7 @@ pub struct BoxLayout {
     pub elements: LayoutElements,
 }
 
-/// Comamnd-based layout.
+/// Command-based layouting.
 #[async_trait(?Send)]
 pub trait Layout {
     /// Create a sequence of layouting commands to execute.

src/lib.rs

@@ -48,7 +48,7 @@ use crate::style::{LayoutStyle, PageStyle, TextStyle};
 use crate::syntax::decoration::Decorations;
 use crate::syntax::parsing::{parse, ParseState};
 use crate::syntax::span::{Offset, Pos};
-use crate::syntax::tree::SyntaxTree;
+use crate::syntax::tree::{DynamicNode, SyntaxNode, SyntaxTree};
 
 /// Transforms source code into typesetted layouts.
 ///
@@ -68,7 +68,7 @@ impl Typesetter {
         Self {
             loader,
             style: LayoutStyle::default(),
-            parse_state: ParseState { scope: crate::library::std() },
+            parse_state: ParseState { scope: crate::library::_std() },
         }
     }
 
@@ -90,7 +90,6 @@ impl Typesetter {
     /// Layout a syntax tree and return the produced layout.
     pub async fn layout(&self, tree: &SyntaxTree) -> Pass<MultiLayout> {
         use crate::layout::prelude::*;
-        use crate::layout::{LayoutContext, LayoutSpace};
 
         let margins = self.style.page.margins();
         layout(
@@ -141,6 +140,11 @@ impl<T> Pass<T> {
         Self { output, feedback }
     }
 
+    /// Create a new pass with empty feedback.
+    pub fn okay(output: T) -> Self {
+        Self { output, feedback: Feedback::new() }
+    }
+
     /// Map the output type and keep the feedback data.
     pub fn map<U>(self, f: impl FnOnce(T) -> U) -> Pass<U> {
         Pass {
@@ -150,6 +154,13 @@ impl<T> Pass<T> {
     }
 }
 
+impl Pass<SyntaxNode> {
+    /// Create a new pass from an unboxed dynamic node and feedback data..
+    pub fn node<T: DynamicNode + 'static>(node: T, feedback: Feedback) -> Self {
+        Pass::new(SyntaxNode::boxed(node), feedback)
+    }
+}
+
 /// Diagnostic and semantic syntax highlighting data.
 #[derive(Debug, Default, Clone, Eq, PartialEq)]
 pub struct Feedback {

src/library/align.rs

@@ -0,0 +1,76 @@
+use super::*;
+
+/// `align`: Align content along the layouting axes.
+///
+/// # Positional arguments
+/// - At most two of `left`, `right`, `top`, `bottom`, `center`.
+///
+/// # Keyword arguments
+/// - `horizontal`: Any of `left`, `right` or `center`.
+/// - `vertical`: Any of `top`, `bottom` or `center`.
+///
+/// There may not be two alignment specifications for the same axis.
+pub fn align(call: FuncCall, state: &ParseState) -> Pass<SyntaxNode> {
+    let mut f = Feedback::new();
+    let mut args = call.header.args;
+    let node = AlignNode {
+        body: parse_body_maybe(call.body, state, &mut f),
+        aligns: args.pos.all::<Spanned<SpecAlign>>().collect(),
+        h: args.key.get::<Spanned<SpecAlign>>("horizontal", &mut f),
+        v: args.key.get::<Spanned<SpecAlign>>("vertical", &mut f),
+    };
+    drain_args(args, &mut f);
+    Pass::node(node, f)
+}
+
+#[derive(Debug, Clone, PartialEq)]
+struct AlignNode {
+    body: Option<SyntaxTree>,
+    aligns: SpanVec<SpecAlign>,
+    h: Option<Spanned<SpecAlign>>,
+    v: Option<Spanned<SpecAlign>>,
+}
+
+#[async_trait(?Send)]
+impl Layout for AlignNode {
+    async fn layout<'a>(&'a self, mut ctx: LayoutContext<'_>) -> Pass<Commands<'a>> {
+        let mut f = Feedback::new();
+
+        ctx.base = ctx.spaces[0].size;
+
+        let axes = ctx.axes;
+        let all = self.aligns.iter()
+            .map(|align| {
+                let spec = align.v.axis().unwrap_or(axes.primary.axis());
+                (spec, align)
+            })
+            .chain(self.h.iter().map(|align| (Horizontal, align)))
+            .chain(self.v.iter().map(|align| (Vertical, align)));
+
+        let mut had = [false; 2];
+        for (axis, align) in all {
+            if align.v.axis().map(|a| a != axis).unwrap_or(false) {
+                error!(
+                    @f, align.span,
+                    "invalid alignment {} for {} axis", align.v, axis,
+                );
+            } else if had[axis as usize] {
+                error!(@f, align.span, "duplicate alignment for {} axis", axis);
+            } else {
+                had[axis as usize] = true;
+                let gen_axis = axis.to_generic(ctx.axes);
+                let gen_align = align.v.to_generic(ctx.axes);
+                *ctx.align.get_mut(gen_axis) = gen_align;
+            }
+        }
+
+        Pass::new(match &self.body {
+            Some(body) => {
+                let layouted = layout(body, ctx).await;
+                f.extend(layouted.feedback);
+                vec![AddMultiple(layouted.output)]
+            }
+            None => vec![SetAlignment(ctx.align)],
+        }, f)
+    }
+}

src/library/boxed.rs

@@ -0,0 +1,53 @@
+use crate::length::ScaleLength;
+use super::*;
+
+/// `box`: Layouts its contents into a box.
+///
+/// # Keyword arguments
+/// - `width`: The width of the box (length of relative to parent's width).
+/// - `height`: The height of the box (length of relative to parent's height).
+pub fn boxed(call: FuncCall, state: &ParseState) -> Pass<SyntaxNode> {
+    let mut f = Feedback::new();
+    let mut args = call.header.args;
+    let node = BoxNode {
+        body: parse_body_maybe(call.body, state, &mut f).unwrap_or(SyntaxTree::new()),
+        width: args.key.get::<ScaleLength>("width", &mut f),
+        height: args.key.get::<ScaleLength>("height", &mut f),
+    };
+    drain_args(args, &mut f);
+    Pass::node(node, f)
+}
+
+#[derive(Debug, Clone, PartialEq)]
+struct BoxNode {
+    body: SyntaxTree,
+    width: Option<ScaleLength>,
+    height: Option<ScaleLength>,
+}
+
+#[async_trait(?Send)]
+impl Layout for BoxNode {
+    async fn layout<'a>(&'a self, mut ctx: LayoutContext<'_>) -> Pass<Commands<'a>> {
+        ctx.spaces.truncate(1);
+        ctx.repeat = false;
+
+        self.width.with(|v| {
+            let length = v.raw_scaled(ctx.base.x);
+            ctx.base.x = length;
+            ctx.spaces[0].size.x = length;
+            ctx.spaces[0].expansion.horizontal = true;
+        });
+
+        self.height.with(|v| {
+            let length = v.raw_scaled(ctx.base.y);
+            ctx.base.y = length;
+            ctx.spaces[0].size.y = length;
+            ctx.spaces[0].expansion.vertical = true;
+        });
+
+        layout(&self.body, ctx).await.map(|out| {
+            let layout = out.into_iter().next().unwrap();
+            vec![Add(layout)]
+        })
+    }
+}

src/library/font.rs

@@ -3,10 +3,56 @@ use fontdock::{FontStyle, FontWeight, FontWidth};
 use crate::length::ScaleLength;
 use super::*;
 
-function! {
 /// `font`: Configure the font.
+///
+/// # Positional arguments
+/// - The font size (optional, length or relative to previous font size).
+/// - A font family fallback list (optional, identifiers or strings).
+///
+/// # Keyword arguments
+/// - `style`: `normal`, `italic` or `oblique`.
+/// - `weight`: `100` - `900` or a name like `thin`.
+/// - `width`: `1` - `9` or a name like `condensed`.
+/// - Any other keyword argument whose value is a tuple of strings is a class
+///   fallback definition like:
+///   ```typst
+///   serif = ("Source Serif Pro", "Noto Serif")
+///   ```
+pub fn font(call: FuncCall, state: &ParseState) -> Pass<SyntaxNode> {
+    let mut f = Feedback::new();
+    let mut args = call.header.args;
+
+    let node = FontNode {
+        body: parse_body_maybe(call.body, state, &mut f),
+        size: args.pos.get::<ScaleLength>(),
+        style: args.key.get::<FontStyle>("style", &mut f),
+        weight: args.key.get::<FontWeight>("weight", &mut f),
+        width: args.key.get::<FontWidth>("width", &mut f),
+        list: {
+            args.pos.all::<StringLike>()
+                .map(|s| s.0.to_lowercase())
+                .collect()
+        },
+        classes: {
+            args.key.all::<Tuple>()
+                .collect::<Vec<_>>()
+                .into_iter()
+                .map(|(class, mut tuple)| {
+                    let fallback = tuple.all::<StringLike>()
+                        .map(|s| s.0.to_lowercase())
+                        .collect();
+                    (class.v.0, fallback)
+                })
+                .collect()
+        },
+    };
+
+    drain_args(args, &mut f);
+    Pass::node(node, f)
+}
+
 #[derive(Debug, Clone, PartialEq)]
-    pub struct FontFunc {
+struct FontNode {
     body: Option<SyntaxTree>,
     size: Option<ScaleLength>,
     style: Option<FontStyle>,
@@ -16,40 +62,9 @@ function! {
     classes: Vec<(String, Vec<String>)>,
 }
 
-    parse(header, body, state, f) {
+#[async_trait(?Send)]
-        let size = header.args.pos.get::<ScaleLength>();
+impl Layout for FontNode {
-        let style = header.args.key.get::<FontStyle>("style", f);
+    async fn layout<'a>(&'a self, ctx: LayoutContext<'_>) -> Pass<Commands<'a>> {
-        let weight = header.args.key.get::<FontWeight>("weight", f);
-        let width = header.args.key.get::<FontWidth>("width", f);
-
-        let list = header.args.pos.all::<StringLike>()
-            .map(|s| s.0.to_lowercase())
-            .collect();
-
-        let classes = header.args.key
-            .all::<Tuple>()
-            .collect::<Vec<_>>()
-            .into_iter()
-            .map(|(class, mut tuple)| {
-                let fallback = tuple.all::<StringLike>()
-                    .map(|s| s.0.to_lowercase())
-                    .collect();
-                (class.v.0, fallback)
-            })
-            .collect();
-
-        Self {
-            body: parse_maybe_body(body, state, f),
-            size,
-            style,
-            weight,
-            width,
-            list,
-            classes,
-        }
-    }
-
-    layout(self, ctx, f) {
         let mut text = ctx.style.text.clone();
 
         self.size.with(|s| match s {
@@ -76,13 +91,13 @@ function! {
 
         text.fallback.flatten();
 
-        match &self.body {
+        Pass::okay(match &self.body {
             Some(tree) => vec![
                 SetTextStyle(text),
                 LayoutSyntaxTree(tree),
                 SetTextStyle(ctx.style.text.clone()),
             ],
             None => vec![SetTextStyle(text)],
-        }
+        })
     }
 }

src/library/layout.rs

@@ -1,104 +0,0 @@
-use crate::length::ScaleLength;
-use super::*;
-
-function! {
-    /// `box`: Layouts content into a box.
-    #[derive(Debug, Clone, PartialEq)]
-    pub struct BoxFunc {
-        body: SyntaxTree,
-        width: Option<ScaleLength>,
-        height: Option<ScaleLength>,
-    }
-
-    parse(header, body, state, f) {
-        Self {
-            body: parse_maybe_body(body, state, f).unwrap_or(SyntaxTree::new()),
-            width: header.args.key.get::<ScaleLength>("width", f),
-            height: header.args.key.get::<ScaleLength>("height", f),
-        }
-    }
-
-    layout(self, ctx, f) {
-        ctx.spaces.truncate(1);
-        ctx.repeat = false;
-
-        self.width.with(|v| {
-            let length = v.raw_scaled(ctx.base.x);
-            ctx.base.x = length;
-            ctx.spaces[0].size.x = length;
-            ctx.spaces[0].expansion.horizontal = true;
-        });
-
-        self.height.with(|v| {
-            let length = v.raw_scaled(ctx.base.y);
-            ctx.base.y = length;
-            ctx.spaces[0].size.y = length;
-            ctx.spaces[0].expansion.vertical = true;
-        });
-
-        let layouted = layout(&self.body, ctx).await;
-        let layout = layouted.output.into_iter().next().unwrap();
-        f.extend(layouted.feedback);
-
-        vec![Add(layout)]
-    }
-}
-
-function! {
-    /// `align`: Aligns content along the layouting axes.
-    #[derive(Debug, Clone, PartialEq)]
-    pub struct AlignFunc {
-        body: Option<SyntaxTree>,
-        aligns: SpanVec<SpecAlign>,
-        h: Option<Spanned<SpecAlign>>,
-        v: Option<Spanned<SpecAlign>>,
-    }
-
-    parse(header, body, state, f) {
-        Self {
-            body: parse_maybe_body(body, state, f),
-            aligns: header.args.pos.all::<Spanned<SpecAlign>>().collect(),
-            h: header.args.key.get::<Spanned<SpecAlign>>("horizontal", f),
-            v: header.args.key.get::<Spanned<SpecAlign>>("vertical", f),
-        }
-    }
-
-    layout(self, ctx, f) {
-        ctx.base = ctx.spaces[0].size;
-
-        let axes = ctx.axes;
-        let all = self.aligns.iter()
-            .map(|align| {
-                let spec = align.v.axis().unwrap_or(axes.primary.axis());
-                (spec, align)
-            })
-            .chain(self.h.iter().map(|align| (Horizontal, align)))
-            .chain(self.v.iter().map(|align| (Vertical, align)));
-
-        let mut had = [false; 2];
-        for (axis, align) in all {
-            if align.v.axis().map(|a| a != axis).unwrap_or(false) {
-                error!(
-                    @f, align.span,
-                    "invalid alignment {} for {} axis", align.v, axis,
-                );
-            } else if had[axis as usize] {
-                error!(@f, align.span, "duplicate alignment for {} axis", axis);
-            } else {
-                had[axis as usize] = true;
-                let gen_axis = axis.to_generic(ctx.axes);
-                let gen_align = align.v.to_generic(ctx.axes);
-                *ctx.align.get_mut(gen_axis) = gen_align;
-            }
-        }
-
-        match &self.body {
-            Some(body) => {
-                let layouted = layout(body, ctx).await;
-                f.extend(layouted.feedback);
-                vec![AddMultiple(layouted.output)]
-            }
-            None => vec![SetAlignment(ctx.align)],
-        }
-    }
-}

src/library/mod.rs

@@ -1,54 +1,34 @@
 //! The standard library.
 
+mod align;
+mod boxed;
 mod font;
-mod layout;
 mod page;
 mod spacing;
+mod val;
 
+pub use align::*;
+pub use boxed::*;
 pub use font::*;
-pub use layout::*;
 pub use page::*;
 pub use spacing::*;
+pub use val::*;
 
 use crate::func::prelude::*;
 use crate::syntax::scope::Scope;
 
 /// Create a scope with all standard library functions.
-pub fn std() -> Scope {
+pub fn _std() -> Scope {
-    let mut std = Scope::new::<ValFunc>();
+    let mut std = Scope::new(Box::new(val));
 
-    std.add::<ValFunc>("val");
+    std.insert("val", Box::new(val));
-    std.add::<FontFunc>("font");
+    std.insert("font", Box::new(font));
-    std.add::<PageFunc>("page");
+    std.insert("page", Box::new(page));
-    std.add::<AlignFunc>("align");
+    std.insert("align", Box::new(align));
-    std.add::<BoxFunc>("box");
+    std.insert("box", Box::new(boxed));
-    std.add::<PageBreakFunc>("pagebreak");
+    std.insert("pagebreak", Box::new(pagebreak));
-    std.add_with_meta::<SpacingFunc>("h", Horizontal);
+    std.insert("h", Box::new(h));
-    std.add_with_meta::<SpacingFunc>("v", Vertical);
+    std.insert("v", Box::new(v));
 
     std
 }
-
-function! {
-    /// `val`: Ignores all arguments and layouts the body flatly.
-    ///
-    /// This is also the fallback function, which is used when a function name
-    /// could not be resolved.
-    #[derive(Debug, Clone, PartialEq)]
-    pub struct ValFunc {
-        body: Option<SyntaxTree>,
-    }
-
-    parse(header, body, state, f) {
-        header.args.pos.0.clear();
-        header.args.key.0.clear();
-        Self { body: parse_maybe_body(body, state, f), }
-    }
-
-    layout(self, ctx, f) {
-        match &self.body {
-            Some(tree) => vec![LayoutSyntaxTree(tree)],
-            None => vec![],
-        }
-    }
-}

src/library/page.rs

@@ -2,10 +2,41 @@ use crate::length::{Length, ScaleLength};
 use crate::paper::{Paper, PaperClass};
 use super::*;
 
-function! {
 /// `page`: Configure pages.
+///
+/// # Positional arguments
+/// - The name of a paper, e.g. `a4` (optional).
+///
+/// # Keyword arguments
+/// - `width`: The width of pages (length).
+/// - `height`: The height of pages (length).
+/// - `margins`: The margins for all sides (length or relative to side lengths).
+/// - `left`: The left margin (length or relative to width).
+/// - `right`: The right margin (length or relative to width).
+/// - `top`: The top margin (length or relative to height).
+/// - `bottom`: The bottom margin (length or relative to height).
+/// - `flip`: Flips custom or paper-defined width and height (boolean).
+pub fn page(call: FuncCall, _: &ParseState) -> Pass<SyntaxNode> {
+    let mut f = Feedback::new();
+    let mut args = call.header.args;
+    expect_no_body(call.body, &mut f);
+    let node = PageNode {
+        paper: args.pos.get::<Paper>(),
+        width: args.key.get::<Length>("width", &mut f),
+        height: args.key.get::<Length>("height", &mut f),
+        margins: args.key.get::<ScaleLength>("margins", &mut f),
+        left: args.key.get::<ScaleLength>("left", &mut f),
+        right: args.key.get::<ScaleLength>("right", &mut f),
+        top: args.key.get::<ScaleLength>("top", &mut f),
+        bottom: args.key.get::<ScaleLength>("bottom", &mut f),
+        flip: args.key.get::<bool>("flip", &mut f).unwrap_or(false),
+    };
+    drain_args(args, &mut f);
+    Pass::node(node, f)
+}
+
 #[derive(Debug, Clone, PartialEq)]
-    pub struct PageFunc {
+struct PageNode {
     paper: Option<Paper>,
     width: Option<Length>,
     height: Option<Length>,
@@ -17,22 +48,9 @@ function! {
     flip: bool,
 }
 
-    parse(header, body, state, f) {
+#[async_trait(?Send)]
-        expect_no_body(body, f);
+impl Layout for PageNode {
-        Self {
+    async fn layout<'a>(&'a self, ctx: LayoutContext<'_>) -> Pass<Commands<'a>> {
-            paper: header.args.pos.get::<Paper>(),
-            width: header.args.key.get::<Length>("width", f),
-            height: header.args.key.get::<Length>("height", f),
-            margins: header.args.key.get::<ScaleLength>("margins", f),
-            left: header.args.key.get::<ScaleLength>("left", f),
-            right: header.args.key.get::<ScaleLength>("right", f),
-            top: header.args.key.get::<ScaleLength>("top", f),
-            bottom: header.args.key.get::<ScaleLength>("bottom", f),
-            flip: header.args.key.get::<bool>("flip", f).unwrap_or(false),
-        }
-    }
-
-    layout(self, ctx, f) {
         let mut style = ctx.style.page;
 
         if let Some(paper) = self.paper {
@@ -54,15 +72,23 @@ function! {
             style.size.swap();
         }
 
-        vec![SetPageStyle(style)]
+        Pass::okay(vec![SetPageStyle(style)])
     }
 }
 
-function! {
 /// `pagebreak`: Ends the current page.
-    #[derive(Debug, Default, Clone, PartialEq)]
+pub fn pagebreak(call: FuncCall, _: &ParseState) -> Pass<SyntaxNode> {
-    pub struct PageBreakFunc;
+    let mut f = Feedback::new();
-
+    drain_args(call.header.args, &mut f);
-    parse(default)
+    Pass::node(PageBreakNode, f)
-    layout(self, ctx, f) { vec![BreakPage] }
+}
+
+#[derive(Debug, Default, Clone, PartialEq)]
+struct PageBreakNode;
+
+#[async_trait(?Send)]
+impl Layout for PageBreakNode {
+    async fn layout<'a>(&'a self, _: LayoutContext<'_>) -> Pass<Commands<'a>> {
+        Pass::okay(vec![BreakPage])
+    }
 }

src/library/spacing.rs

@@ -2,31 +2,49 @@ use crate::layout::SpacingKind;
 use crate::length::ScaleLength;
 use super::*;
 
-function! {
+/// `h`: Add horizontal spacing.
-    /// `h` and `v`: Add horizontal or vertical spacing.
+///
+/// # Positional arguments
+/// - The spacing (length or relative to font size).
+pub fn h(call: FuncCall, _: &ParseState) -> Pass<SyntaxNode> {
+    spacing(call, Horizontal)
+}
+
+/// `v`: Add vertical spacing.
+///
+/// # Positional arguments
+/// - The spacing (length or relative to font size).
+pub fn v(call: FuncCall, _: &ParseState) -> Pass<SyntaxNode> {
+    spacing(call, Vertical)
+}
+
+fn spacing(call: FuncCall, axis: SpecAxis) -> Pass<SyntaxNode> {
+    let mut f = Feedback::new();
+    let mut args = call.header.args;
+    expect_no_body(call.body, &mut f);
+    let node = SpacingNode {
+        spacing: args.pos.expect::<ScaleLength>(&mut f)
+            .map(|s| (axis, s))
+            .or_missing(call.header.name.span, "spacing", &mut f),
+    };
+    drain_args(args, &mut f);
+    Pass::node(node, f)
+}
+
 #[derive(Debug, Clone, PartialEq)]
-    pub struct SpacingFunc {
+struct SpacingNode {
     spacing: Option<(SpecAxis, ScaleLength)>,
 }
 
-    type Meta = SpecAxis;
+#[async_trait(?Send)]
-
+impl Layout for SpacingNode {
-    parse(header, body, state, f, meta) {
+    async fn layout<'a>(&'a self, ctx: LayoutContext<'_>) -> Pass<Commands<'a>> {
-        expect_no_body(body, f);
+        Pass::okay(if let Some((axis, spacing)) = self.spacing {
-        Self {
-            spacing: header.args.pos.expect::<ScaleLength>(f)
-                .map(|s| (meta, s))
-                .or_missing(header.name.span, "spacing", f),
-        }
-    }
-
-    layout(self, ctx, f) {
-        if let Some((axis, spacing)) = self.spacing {
             let axis = axis.to_generic(ctx.axes);
             let spacing = spacing.raw_scaled(ctx.style.text.font_size());
             vec![AddSpacing(spacing, SpacingKind::Hard, axis)]
         } else {
             vec![]
-        }
+        })
     }
 }

src/library/val.rs

@@ -0,0 +1,28 @@
+use super::*;
+
+/// `val`: Ignores all arguments and layouts its body flatly.
+///
+/// This is also the fallback function, which is used when a function name
+/// cannot be resolved.
+pub fn val(call: FuncCall, state: &ParseState) -> Pass<SyntaxNode> {
+    let mut f = Feedback::new();
+    let node = ValNode {
+        body: parse_body_maybe(call.body, state, &mut f),
+    };
+    Pass::node(node, f)
+}
+
+#[derive(Debug, Clone, PartialEq)]
+struct ValNode {
+    body: Option<SyntaxTree>,
+}
+
+#[async_trait(?Send)]
+impl Layout for ValNode {
+    async fn layout<'a>(&'a self, _: LayoutContext<'_>) -> Pass<Commands<'a>> {
+        Pass::okay(match &self.body {
+            Some(tree) => vec![LayoutSyntaxTree(tree)],
+            None => vec![],
+        })
+    }
+}

src/syntax/mod.rs

@@ -12,11 +12,3 @@ pub mod span;
 pub mod tokens;
 pub mod tree;
 pub mod value;
-
-/// Basic types used around the syntax side.
-pub mod prelude {
-    pub use super::expr::*;
-    pub use super::span::{Span, SpanVec, Spanned};
-    pub use super::tree::{DynamicNode, SyntaxNode, SyntaxTree};
-    pub use super::value::*;
-}

src/syntax/parsing.rs

@@ -8,36 +8,16 @@ use super::expr::*;
 use super::scope::Scope;
 use super::span::{Pos, Span, Spanned};
 use super::tokens::{is_newline_char, Token, TokenMode, Tokens};
-use super::tree::{DynamicNode, SyntaxNode, SyntaxTree};
+use super::tree::{SyntaxNode, SyntaxTree};
 
 /// A function which parses a function call into a dynamic node.
-pub type CallParser = dyn Fn(FuncCall, &ParseState) -> Pass<Box<dyn DynamicNode>>;
+pub type CallParser = dyn Fn(FuncCall, &ParseState) -> Pass<SyntaxNode>;
-
-/// Parse a function call.
-pub trait ParseCall {
-    /// Metadata whose value is passed to `parse`. This allows a single function
-    /// to do different things depending on the value that needs to be given
-    /// when inserting the function into a scope.
-    ///
-    /// For example, the functions `h` and `v` are built on the same type.
-    type Meta: Clone;
-
-    /// Parse the function call.
-    fn parse(
-        call: FuncCall,
-        state: &ParseState,
-        metadata: Self::Meta,
-    ) -> Pass<Self>
-    where
-        Self: Sized;
-}
 
 /// An invocation of a function.
 #[derive(Debug, Clone, PartialEq)]
 pub struct FuncCall<'s> {
     pub header: FuncHeader,
-    /// The body as a raw string containing what's inside of the brackets.
+    pub body: FuncBody<'s>,
-    pub body: Option<Spanned<&'s str>>,
 }
 
 /// The parsed header of a function (everything in the first set of brackets).
@@ -47,6 +27,10 @@ pub struct FuncHeader {
     pub args: FuncArgs,
 }
 
+/// The body of a function as a raw spanned string containing what's inside of
+/// the brackets.
+pub type FuncBody<'s> = Option<Spanned<&'s str>>;
+
 /// The positional and keyword arguments passed to a function.
 #[derive(Debug, Default, Clone, PartialEq)]
 pub struct FuncArgs {
@@ -215,7 +199,7 @@ impl<'s> FuncParser<'s> {
         let call = FuncCall { header, body: self.body };
         let parsed = parser(call, self.state);
         self.feedback.extend(parsed.feedback);
-        Pass::new(SyntaxNode::Dyn(parsed.output), self.feedback)
+        Pass::new(parsed.output, self.feedback)
     }
 
     fn parse_func_header(&mut self) -> Option<FuncHeader> {
@@ -678,7 +662,7 @@ fn unescape_raw(raw: &str) -> Vec<String> {
 mod tests {
     use crate::length::Length;
     use crate::syntax::span::SpanVec;
-    use crate::syntax::test::{check, DebugFn};
+    use crate::syntax::test::{check, debug_func, DebugNode};
     use super::*;
 
     use Decoration::*;
@@ -697,11 +681,11 @@ mod tests {
         };
 
         ($source:expr => [$($tree:tt)*], [$($diagnostics:tt)*] $(, [$($decos:tt)*])? $(,)?) => {
-            let mut scope = Scope::new::<DebugFn>();
+            let mut scope = Scope::new(Box::new(debug_func));
-            scope.add::<DebugFn>("f");
+            scope.insert("f", Box::new(debug_func));
-            scope.add::<DebugFn>("n");
+            scope.insert("n", Box::new(debug_func));
-            scope.add::<DebugFn>("box");
+            scope.insert("box", Box::new(debug_func));
-            scope.add::<DebugFn>("val");
+            scope.insert("val", Box::new(debug_func));
 
             let state = ParseState { scope };
             let pass = parse($source, Pos::ZERO, &state);
@@ -798,13 +782,13 @@ mod tests {
                     value: Z($value),
                 })));)*)?
             )?
-            SyntaxNode::Dyn(Box::new(DebugFn {
+            SyntaxNode::boxed(DebugNode {
                 header: FuncHeader {
                     name: span_item!($name).map(|s| Ident(s.to_string())),
                     args,
                 },
                 body: func!(@body $($($body)*)?),
-            }))
+            })
         }};
         (@body [$($body:tt)*]) => { Some(span_vec![$($body)*].0) };
         (@body) => { None };

src/syntax/scope.rs

@@ -3,8 +3,7 @@
 use std::collections::HashMap;
 use std::fmt::{self, Debug, Formatter};
 
-use super::parsing::{CallParser, ParseCall};
+use super::parsing::CallParser;
-use super::tree::DynamicNode;
 
 /// A map from identifiers to function parsers.
 pub struct Scope {
@@ -15,31 +14,16 @@ pub struct Scope {
 impl Scope {
     /// Create a new empty scope with a fallback parser that is invoked when no
     /// match is found.
-    pub fn new<F>() -> Self
+    pub fn new(fallback: Box<CallParser>) -> Self {
-    where
-        F: ParseCall<Meta = ()> + DynamicNode + 'static
-    {
         Self {
             parsers: HashMap::new(),
-            fallback: make_parser::<F>(()),
+            fallback,
         }
     }
 
     /// Associate the given function name with a dynamic node type.
-    pub fn add<F>(&mut self, name: &str)
+    pub fn insert(&mut self, name: impl Into<String>, parser: Box<CallParser>) {
-    where
+        self.parsers.insert(name.into(), parser);
-        F: ParseCall<Meta = ()> + DynamicNode + 'static
-    {
-        self.add_with_meta::<F>(name, ());
-    }
-
-    /// Add a dynamic node type with additional metadata that is passed to the
-    /// parser.
-    pub fn add_with_meta<F>(&mut self, name: &str, metadata: <F as ParseCall>::Meta)
-    where
-        F: ParseCall + DynamicNode + 'static
-    {
-        self.parsers.insert(name.to_string(), make_parser::<F>(metadata));
     }
 
     /// Return the parser with the given name if there is one.
@@ -58,13 +42,3 @@ impl Debug for Scope {
         f.debug_set().entries(self.parsers.keys()).finish()
     }
 }
-
-fn make_parser<F>(metadata: <F as ParseCall>::Meta) -> Box<CallParser>
-where
-    F: ParseCall + DynamicNode + 'static,
-{
-    Box::new(move |f, s| {
-        F::parse(f, s, metadata.clone())
-            .map(|tree| Box::new(tree) as Box<dyn DynamicNode>)
-    })
-}

src/syntax/test.rs

@@ -1,6 +1,6 @@
 use std::fmt::Debug;
 
-use crate::func::parse_maybe_body;
+use crate::func::prelude::*;
 use super::decoration::Decoration;
 use super::expr::{Expr, Ident, NamedTuple, Object, Pair, Tuple};
 use super::parsing::{FuncArg, FuncArgs, FuncHeader};
@@ -58,28 +58,28 @@ macro_rules! span_item {
     };
 }
 
-function! {
+pub fn debug_func(call: FuncCall, state: &ParseState) -> Pass<SyntaxNode> {
-    /// Most functions in the tests are parsed into the debug function for easy
+    let mut f = Feedback::new();
-    /// inspection of arguments and body.
+    let node = DebugNode {
+        header: call.header,
+        body: parse_body_maybe(call.body, state, &mut f),
+    };
+    Pass::node(node, f)
+}
+
 #[derive(Debug, Clone, PartialEq)]
-    pub struct DebugFn {
+pub struct DebugNode {
     pub header: FuncHeader,
     pub body: Option<SyntaxTree>,
 }
 
-    parse(header, body, state, f) {
+#[async_trait(?Send)]
-        let cloned = header.clone();
+impl Layout for DebugNode {
-        header.args.pos.0.clear();
+    async fn layout<'a>(&'a self, _: LayoutContext<'_>) -> Pass<Commands<'a>> {
-        header.args.key.0.clear();
+        unimplemented!()
-        Self {
-            header: cloned,
-            body: parse_maybe_body(body, state, f),
     }
 }
 
-    layout(self, ctx, f) { vec![] }
-}
-
 /// Compares elements by only looking at values and ignoring spans.
 pub trait SpanlessEq<Rhs = Self> {
     fn spanless_eq(&self, other: &Rhs) -> bool;
@@ -87,8 +87,8 @@ pub trait SpanlessEq<Rhs = Self> {
 
 impl SpanlessEq for SyntaxNode {
     fn spanless_eq(&self, other: &Self) -> bool {
-        fn downcast<'a>(func: &'a (dyn DynamicNode + 'static)) -> &'a DebugFn {
+        fn downcast<'a>(func: &'a (dyn DynamicNode + 'static)) -> &'a DebugNode {
-            func.downcast::<DebugFn>().expect("not a debug fn")
+            func.downcast::<DebugNode>().expect("not a debug node")
         }
 
         match (self, other) {
@@ -101,7 +101,7 @@ impl SpanlessEq for SyntaxNode {
     }
 }
 
-impl SpanlessEq for DebugFn {
+impl SpanlessEq for DebugNode {
     fn spanless_eq(&self, other: &Self) -> bool {
         self.header.spanless_eq(&other.header)
             && self.body.spanless_eq(&other.body)

src/syntax/tree.rs

@@ -31,6 +31,13 @@ pub enum SyntaxNode {
     Dyn(Box<dyn DynamicNode>),
 }
 
+impl SyntaxNode {
+    /// Create a `Dyn` variant from an unboxed dynamic node.
+    pub fn boxed<T: DynamicNode + 'static>(node: T) -> SyntaxNode {
+        SyntaxNode::Dyn(Box::new(node))
+    }
+}
+
 impl PartialEq for SyntaxNode {
     fn eq(&self, other: &SyntaxNode) -> bool {
         use SyntaxNode::*;
@@ -65,10 +72,7 @@ pub trait DynamicNode: Debug + Layout {
 
 impl dyn DynamicNode {
     /// Downcast this dynamic node to a concrete node.
-    pub fn downcast<T>(&self) -> Option<&T>
+    pub fn downcast<T: DynamicNode + 'static>(&self) -> Option<&T> {
-    where
-        T: DynamicNode + 'static,
-    {
         self.as_any().downcast_ref::<T>()
     }
 }

src/syntax/value.rs

@@ -2,7 +2,7 @@
 
 use fontdock::{FontStyle, FontWeight, FontWidth};
 
-use crate::layout::prelude::*;
+use crate::layout::{Dir, SpecAlign};
 use crate::length::{Length, ScaleLength};
 use crate::paper::Paper;
 use crate::Feedback;
@@ -103,10 +103,10 @@ macro_rules! ident_value {
 }
 
 ident_value!(Dir, "direction", |s| match s {
-    "ltr" => Some(LTR),
+    "ltr" => Some(Self::LTR),
-    "rtl" => Some(RTL),
+    "rtl" => Some(Self::RTL),
-    "ttb" => Some(TTB),
+    "ttb" => Some(Self::TTB),
-    "btt" => Some(BTT),
+    "btt" => Some(Self::BTT),
     _ => None,
 });