Add arguments value 🏓

15 files changed, 390 insertions, 304 deletions

diff --git a/src/eval/call.rs b/src/eval/call.rs
deleted file mode 100644
index 1a80e15a..00000000
--- a/src/eval/call.rs
+++ /dev/null
@@ -1,197 +0,0 @@
-use super::*;
-
-impl Eval for ExprCall {
-    type Output = Value;
-
-    fn eval(&self, ctx: &mut EvalContext) -> Self::Output {
-        let callee = self.callee.eval(ctx);
-
-        if let Value::Func(func) = callee {
-            let func = func.clone();
-            let mut args = self.args.eval(ctx);
-            let returned = func(ctx, &mut args);
-            args.finish(ctx);
-
-            return returned;
-        } else if callee != Value::Error {
-            ctx.diag(error!(
-                self.callee.span(),
-                "expected function, found {}",
-                callee.type_name(),
-            ));
-        }
-
-        Value::Error
-    }
-}
-
-impl Eval for ExprArgs {
-    type Output = Args;
-
-    fn eval(&self, ctx: &mut EvalContext) -> Self::Output {
-        let mut pos = vec![];
-        let mut named = vec![];
-
-        for arg in &self.items {
-            match arg {
-                Argument::Pos(expr) => {
-                    pos.push(expr.eval(ctx).with_span(expr.span()));
-                }
-                Argument::Named(Named { name, expr }) => {
-                    named.push((
-                        name.string.clone().with_span(name.span),
-                        expr.eval(ctx).with_span(expr.span()),
-                    ));
-                }
-            }
-        }
-
-        Args { span: self.span, pos, named }
-    }
-}
-
-/// Evaluated arguments to a function.
-#[derive(Debug)]
-pub struct Args {
-    /// The span of the whole argument list.
-    pub span: Span,
-    /// The positional arguments.
-    pub pos: SpanVec<Value>,
-    /// The named arguments.
-    pub named: Vec<(Spanned<String>, Spanned<Value>)>,
-}
-
-impl Args {
-    /// Find and remove the first convertible positional argument.
-    pub fn find<T>(&mut self, ctx: &mut EvalContext) -> Option<T>
-    where
-        T: Cast<Spanned<Value>>,
-    {
-        (0 .. self.pos.len()).find_map(move |i| try_cast(ctx, &mut self.pos, i))
-    }
-
-    /// Find and remove the first convertible positional argument, producing an
-    /// error if no match was found.
-    pub fn require<T>(&mut self, ctx: &mut EvalContext, what: &str) -> Option<T>
-    where
-        T: Cast<Spanned<Value>>,
-    {
-        let found = self.find(ctx);
-        if found.is_none() {
-            ctx.diag(error!(self.span, "missing argument: {}", what));
-        }
-        found
-    }
-
-    /// Filter out and remove all convertible positional arguments.
-    pub fn filter<'a, 'b: 'a, T>(
-        &'a mut self,
-        ctx: &'a mut EvalContext<'b>,
-    ) -> impl Iterator<Item = T> + Captures<'a> + Captures<'b>
-    where
-        T: Cast<Spanned<Value>>,
-    {
-        let mut i = 0;
-        std::iter::from_fn(move || {
-            while i < self.pos.len() {
-                if let Some(val) = try_cast(ctx, &mut self.pos, i) {
-                    return Some(val);
-                }
-                i += 1;
-            }
-            None
-        })
-    }
-
-    /// Convert and remove the value for the given named argument, producing an
-    /// error if the conversion fails.
-    pub fn get<T>(&mut self, ctx: &mut EvalContext, name: &str) -> Option<T>
-    where
-        T: Cast<Spanned<Value>>,
-    {
-        let index = self.named.iter().position(|(k, _)| k.v.as_str() == name)?;
-        let value = self.named.remove(index).1;
-        cast(ctx, value)
-    }
-
-    /// Drain all remainings arguments into an array and a dictionary.
-    pub fn drain(&mut self) -> (ValueArray, ValueDict) {
-        let array = self.pos.drain(..).map(|s| s.v).collect();
-        let dict = self.named.drain(..).map(|(k, v)| (k.v, v.v)).collect();
-        (array, dict)
-    }
-
-    /// Produce "unexpected argument" errors for all remaining arguments.
-    pub fn finish(self, ctx: &mut EvalContext) {
-        let a = self.pos.iter().map(|v| v.as_ref());
-        let b = self.named.iter().map(|(k, v)| (&v.v).with_span(k.span.join(v.span)));
-        for value in a.chain(b) {
-            if value.v != &Value::Error {
-                ctx.diag(error!(value.span, "unexpected argument"));
-            }
-        }
-    }
-}
-
-// This is a workaround because `-> impl Trait + 'a + 'b` does not work.
-//
-// See also: https://github.com/rust-lang/rust/issues/49431
-#[doc(hidden)]
-pub trait Captures<'a> {}
-impl<'a, T: ?Sized> Captures<'a> for T {}
-
-/// Cast the value into `T`, generating an error if the conversion fails.
-fn cast<T>(ctx: &mut EvalContext, value: Spanned<Value>) -> Option<T>
-where
-    T: Cast<Spanned<Value>>,
-{
-    let span = value.span;
-    match T::cast(value) {
-        CastResult::Ok(t) => Some(t),
-        CastResult::Warn(t, m) => {
-            ctx.diag(warning!(span, "{}", m));
-            Some(t)
-        }
-        CastResult::Err(value) => {
-            ctx.diag(error!(
-                span,
-                "expected {}, found {}",
-                T::TYPE_NAME,
-                value.v.type_name()
-            ));
-            None
-        }
-    }
-}
-
-/// Try to cast the value in the slot into `T`, putting it back if the
-/// conversion fails.
-fn try_cast<T>(
-    ctx: &mut EvalContext,
-    vec: &mut Vec<Spanned<Value>>,
-    i: usize,
-) -> Option<T>
-where
-    T: Cast<Spanned<Value>>,
-{
-    // Replace with error placeholder when conversion works since error values
-    // are ignored when generating "unexpected argument" errors.
-    let slot = &mut vec[i];
-    let value = std::mem::replace(slot, Spanned::zero(Value::None));
-    let span = value.span;
-    match T::cast(value) {
-        CastResult::Ok(t) => {
-            vec.remove(i);
-            Some(t)
-        }
-        CastResult::Warn(t, m) => {
-            vec.remove(i);
-            ctx.diag(warning!(span, "{}", m));
-            Some(t)
-        }
-        CastResult::Err(value) => {
-            *slot = value;
-            None
-        }
-    }
-}
diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index 2390a84f..4f0beb34 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -2,12 +2,10 @@
 
 #[macro_use]
 mod value;
-mod call;
 mod capture;
 mod ops;
 mod scope;
 
-pub use call::*;
 pub use capture::*;
 pub use scope::*;
 pub use value::*;
@@ -344,6 +342,54 @@ impl ExprBinary {
     }
 }
 
+impl Eval for ExprCall {
+    type Output = Value;
+
+    fn eval(&self, ctx: &mut EvalContext) -> Self::Output {
+        let callee = self.callee.eval(ctx);
+
+        if let Value::Func(func) = callee {
+            let func = func.clone();
+            let mut args = self.args.eval(ctx);
+            let returned = func(ctx, &mut args);
+            args.finish(ctx);
+
+            return returned;
+        } else if callee != Value::Error {
+            ctx.diag(error!(
+                self.callee.span(),
+                "expected function, found {}",
+                callee.type_name(),
+            ));
+        }
+
+        Value::Error
+    }
+}
+
+impl Eval for ExprArgs {
+    type Output = ValueArgs;
+
+    fn eval(&self, ctx: &mut EvalContext) -> Self::Output {
+        let items = self
+            .items
+            .iter()
+            .map(|arg| match arg {
+                ExprArg::Pos(expr) => ValueArg {
+                    name: None,
+                    value: expr.eval(ctx).with_span(expr.span()),
+                },
+                ExprArg::Named(Named { name, expr }) => ValueArg {
+                    name: Some(name.string.clone().with_span(name.span)),
+                    value: expr.eval(ctx).with_span(expr.span()),
+                },
+            })
+            .collect();
+
+        ValueArgs { span: self.span, items }
+    }
+}
+
 impl Eval for ExprLet {
     type Output = Value;
 
diff --git a/src/eval/value.rs b/src/eval/value.rs
index dd1221e5..94477aa5 100644
--- a/src/eval/value.rs
+++ b/src/eval/value.rs
@@ -42,6 +42,8 @@ pub enum Value {
     Template(ValueTemplate),
     /// An executable function.
     Func(ValueFunc),
+    /// Arguments to a function.
+    Args(ValueArgs),
     /// Any object.
     Any(ValueAny),
     /// The result of invalid operations.
@@ -50,11 +52,11 @@ pub enum Value {
 
 impl Value {
     /// Create a new template value consisting of a single dynamic node.
-    pub fn template<F>(f: F) -> Self
+    pub fn template<F>(name: impl Into<String>, f: F) -> Self
     where
         F: Fn(&mut ExecContext) + 'static,
     {
-        Self::Template(vec![TemplateNode::Any(TemplateAny::new(f))])
+        Self::Template(vec![TemplateNode::Any(TemplateAny::new(name, f))])
     }
 
     /// The name of the stored value's type.
@@ -74,6 +76,7 @@ impl Value {
             Self::Dict(_) => ValueDict::TYPE_NAME,
             Self::Template(_) => ValueTemplate::TYPE_NAME,
             Self::Func(_) => ValueFunc::TYPE_NAME,
+            Self::Args(_) => ValueArgs::TYPE_NAME,
             Self::Any(v) => v.type_name(),
             Self::Error => "error",
         }
@@ -111,8 +114,9 @@ impl Pretty for Value {
             Value::Dict(v) => v.pretty(p),
             Value::Template(v) => v.pretty(p),
             Value::Func(v) => v.pretty(p),
+            Value::Args(v) => v.pretty(p),
             Value::Any(v) => v.pretty(p),
-            Value::Error => p.push_str("(error)"),
+            Value::Error => p.push_str("<error>"),
         }
     }
 }
@@ -194,16 +198,17 @@ impl Pretty for TemplateNode {
 /// A reference-counted dynamic template node (can implement custom behaviour).
 #[derive(Clone)]
 pub struct TemplateAny {
+    name: String,
     f: Rc<dyn Fn(&mut ExecContext)>,
 }
 
 impl TemplateAny {
     /// Create a new dynamic template value from a rust function or closure.
-    pub fn new<F>(f: F) -> Self
+    pub fn new<F>(name: impl Into<String>, f: F) -> Self
     where
         F: Fn(&mut ExecContext) + 'static,
     {
-        Self { f: Rc::new(f) }
+        Self { name: name.into(), f: Rc::new(f) }
     }
 }
 
@@ -224,7 +229,9 @@ impl Deref for TemplateAny {
 
 impl Pretty for TemplateAny {
     fn pretty(&self, p: &mut Printer) {
-        p.push_str("<any>");
+        p.push('<');
+        p.push_str(&self.name);
+        p.push('>');
     }
 }
 
@@ -238,14 +245,14 @@ impl Debug for TemplateAny {
 #[derive(Clone)]
 pub struct ValueFunc {
     name: String,
-    f: Rc<dyn Fn(&mut EvalContext, &mut Args) -> Value>,
+    f: Rc<dyn Fn(&mut EvalContext, &mut ValueArgs) -> Value>,
 }
 
 impl ValueFunc {
     /// Create a new function value from a rust function or closure.
     pub fn new<F>(name: impl Into<String>, f: F) -> Self
     where
-        F: Fn(&mut EvalContext, &mut Args) -> Value + 'static,
+        F: Fn(&mut EvalContext, &mut ValueArgs) -> Value + 'static,
     {
         Self { name: name.into(), f: Rc::new(f) }
     }
@@ -259,7 +266,7 @@ impl PartialEq for ValueFunc {
 }
 
 impl Deref for ValueFunc {
-    type Target = dyn Fn(&mut EvalContext, &mut Args) -> Value;
+    type Target = dyn Fn(&mut EvalContext, &mut ValueArgs) -> Value;
 
     fn deref(&self) -> &Self::Target {
         self.f.as_ref()
@@ -268,7 +275,9 @@ impl Deref for ValueFunc {
 
 impl Pretty for ValueFunc {
     fn pretty(&self, p: &mut Printer) {
+        p.push('<');
         p.push_str(&self.name);
+        p.push('>');
     }
 }
 
@@ -278,6 +287,180 @@ impl Debug for ValueFunc {
     }
 }
 
+/// Evaluated arguments to a function.
+#[derive(Debug, Clone, PartialEq)]
+pub struct ValueArgs {
+    /// The span of the whole argument list.
+    pub span: Span,
+    /// The arguments.
+    pub items: Vec<ValueArg>,
+}
+
+impl ValueArgs {
+    /// Find and remove the first convertible positional argument.
+    pub fn find<T>(&mut self, ctx: &mut EvalContext) -> Option<T>
+    where
+        T: Cast<Spanned<Value>>,
+    {
+        (0 .. self.items.len()).find_map(move |i| self.try_take(ctx, i))
+    }
+
+    /// Find and remove the first convertible positional argument, producing an
+    /// error if no match was found.
+    pub fn require<T>(&mut self, ctx: &mut EvalContext, what: &str) -> Option<T>
+    where
+        T: Cast<Spanned<Value>>,
+    {
+        let found = self.find(ctx);
+        if found.is_none() {
+            ctx.diag(error!(self.span, "missing argument: {}", what));
+        }
+        found
+    }
+
+    /// Filter out and remove all convertible positional arguments.
+    pub fn filter<'a, 'b: 'a, T>(
+        &'a mut self,
+        ctx: &'a mut EvalContext<'b>,
+    ) -> impl Iterator<Item = T> + Captures<'a> + Captures<'b>
+    where
+        T: Cast<Spanned<Value>>,
+    {
+        let mut i = 0;
+        std::iter::from_fn(move || {
+            while i < self.items.len() {
+                if let Some(val) = self.try_take(ctx, i) {
+                    return Some(val);
+                }
+                i += 1;
+            }
+            None
+        })
+    }
+
+    /// Convert and remove the value for the given named argument, producing an
+    /// error if the conversion fails.
+    pub fn get<T>(&mut self, ctx: &mut EvalContext, name: &str) -> Option<T>
+    where
+        T: Cast<Spanned<Value>>,
+    {
+        let index = self
+            .items
+            .iter()
+            .position(|arg| arg.name.as_ref().map(|s| s.v.as_str()) == Some(name))?;
+
+        let value = self.items.remove(index).value;
+        self.cast(ctx, value)
+    }
+
+    /// Produce "unexpected argument" errors for all remaining arguments.
+    pub fn finish(self, ctx: &mut EvalContext) {
+        for arg in &self.items {
+            if arg.value.v != Value::Error {
+                ctx.diag(error!(arg.span(), "unexpected argument"));
+            }
+        }
+    }
+
+    /// Cast the value into `T`, generating an error if the conversion fails.
+    fn cast<T>(&self, ctx: &mut EvalContext, value: Spanned<Value>) -> Option<T>
+    where
+        T: Cast<Spanned<Value>>,
+    {
+        let span = value.span;
+        match T::cast(value) {
+            CastResult::Ok(t) => Some(t),
+            CastResult::Warn(t, m) => {
+                ctx.diag(warning!(span, "{}", m));
+                Some(t)
+            }
+            CastResult::Err(value) => {
+                ctx.diag(error!(
+                    span,
+                    "expected {}, found {}",
+                    T::TYPE_NAME,
+                    value.v.type_name()
+                ));
+                None
+            }
+        }
+    }
+
+    /// Try to take and cast a positional argument in the i'th slot into `T`,
+    /// putting it back if the conversion fails.
+    fn try_take<T>(&mut self, ctx: &mut EvalContext, i: usize) -> Option<T>
+    where
+        T: Cast<Spanned<Value>>,
+    {
+        let slot = &mut self.items[i];
+        if slot.name.is_some() {
+            return None;
+        }
+
+        let value = std::mem::replace(&mut slot.value, Spanned::zero(Value::None));
+        let span = value.span;
+        match T::cast(value) {
+            CastResult::Ok(t) => {
+                self.items.remove(i);
+                Some(t)
+            }
+            CastResult::Warn(t, m) => {
+                self.items.remove(i);
+                ctx.diag(warning!(span, "{}", m));
+                Some(t)
+            }
+            CastResult::Err(value) => {
+                slot.value = value;
+                None
+            }
+        }
+    }
+}
+
+impl Pretty for ValueArgs {
+    fn pretty(&self, p: &mut Printer) {
+        p.push('<');
+        p.join(&self.items, ", ", |item, p| item.pretty(p));
+        p.push('>');
+    }
+}
+
+// This is a workaround because `-> impl Trait + 'a + 'b` does not work.
+//
+// See also: https://github.com/rust-lang/rust/issues/49431
+#[doc(hidden)]
+pub trait Captures<'a> {}
+impl<'a, T: ?Sized> Captures<'a> for T {}
+
+/// An argument to a function call: `12` or `draw: false`.
+#[derive(Debug, Clone, PartialEq)]
+pub struct ValueArg {
+    /// The name of the argument (`None` for positional arguments).
+    pub name: Option<Spanned<String>>,
+    /// The value of the argument.
+    pub value: Spanned<Value>,
+}
+
+impl ValueArg {
+    /// The source code location.
+    pub fn span(&self) -> Span {
+        match &self.name {
+            Some(name) => name.span.join(self.value.span),
+            None => self.value.span,
+        }
+    }
+}
+
+impl Pretty for ValueArg {
+    fn pretty(&self, p: &mut Printer) {
+        if let Some(name) = &self.name {
+            p.push_str(&name.v);
+            p.push_str(": ");
+        }
+        self.value.v.pretty(p);
+    }
+}
+
 /// A wrapper around a dynamic value.
 pub struct ValueAny(Box<dyn Bounds>);
 
@@ -454,7 +637,7 @@ where
     }
 }
 
-macro_rules! impl_primitive {
+macro_rules! primitive {
     ($type:ty:
         $type_name:literal,
         $variant:path
@@ -482,28 +665,29 @@ macro_rules! impl_primitive {
     };
 }
 
-impl_primitive! { bool: "boolean", Value::Bool }
-impl_primitive! { i64: "integer", Value::Int }
-impl_primitive! {
+primitive! { bool: "boolean", Value::Bool }
+primitive! { i64: "integer", Value::Int }
+primitive! {
     f64: "float",
     Value::Float,
     Value::Int(v) => v as f64,
 }
-impl_primitive! { Length: "length", Value::Length }
-impl_primitive! { Angle: "angle", Value::Angle }
-impl_primitive! { Relative: "relative", Value::Relative }
-impl_primitive! {
+primitive! { Length: "length", Value::Length }
+primitive! { Angle: "angle", Value::Angle }
+primitive! { Relative: "relative", Value::Relative }
+primitive! {
     Linear: "linear",
     Value::Linear,
     Value::Length(v) => v.into(),
     Value::Relative(v) => v.into(),
 }
-impl_primitive! { Color: "color", Value::Color }
-impl_primitive! { String: "string", Value::Str }
-impl_primitive! { ValueArray: "array", Value::Array }
-impl_primitive! { ValueDict: "dictionary", Value::Dict }
-impl_primitive! { ValueTemplate: "template", Value::Template }
-impl_primitive! { ValueFunc: "function", Value::Func }
+primitive! { Color: "color", Value::Color }
+primitive! { String: "string", Value::Str }
+primitive! { ValueArray: "array", Value::Array }
+primitive! { ValueDict: "dictionary", Value::Dict }
+primitive! { ValueTemplate: "template", Value::Template }
+primitive! { ValueFunc: "function", Value::Func }
+primitive! { ValueArgs: "arguments", Value::Args }
 
 impl From<&str> for Value {
     fn from(v: &str) -> Self {
@@ -519,11 +703,23 @@ impl From<ValueAny> for Value {
 
 /// Make a type usable as a [`Value`].
 ///
-/// Given a type `T`, this always implements the following traits:
+/// Given a type `T`, this implements the following traits:
 /// - [`Type`] for `T`,
 /// - [`Cast<Value>`](Cast) for `T`.
+///
+/// # Example
+/// Make a type `FontFamily` that can be cast from a [`Value::Any`] variant
+/// containing a `FontFamily` or from a string.
+/// ```
+/// # use typst::typify;
+/// # enum FontFamily { Named(String) }
+/// typify! {
+///     FontFamily: "font family",
+///     Value::Str(string) => Self::Named(string.to_lowercase())
+/// }
+/// ```
 #[macro_export]
-macro_rules! impl_type {
+macro_rules! typify {
     ($type:ty:
         $type_name:literal
         $(, $pattern:pat => $out:expr)*
@@ -575,23 +771,19 @@ mod tests {
     }
 
     #[test]
-    fn test_pretty_print_simple_values() {
+    fn test_pretty_print_value() {
+        // Simple values.
         test_pretty(Value::None, "none");
         test_pretty(false, "false");
-        test_pretty(12.4, "12.4");
+        test_pretty(12, "12");
+        test_pretty(3.14, "3.14");
         test_pretty(Length::pt(5.5), "5.5pt");
         test_pretty(Angle::deg(90.0), "90.0deg");
         test_pretty(Relative::ONE / 2.0, "50.0%");
         test_pretty(Relative::new(0.3) + Length::cm(2.0), "30.0% + 2.0cm");
         test_pretty(Color::Rgba(RgbaColor::new(1, 1, 1, 0xff)), "#010101");
         test_pretty("hello", r#""hello""#);
-        test_pretty(ValueFunc::new("nil", |_, _| Value::None), "nil");
-        test_pretty(ValueAny::new(1), "1");
-        test_pretty(Value::Error, "(error)");
-    }
 
-    #[test]
-    fn test_pretty_print_collections() {
         // Array.
         test_pretty(Value::Array(vec![]), "()");
         test_pretty(vec![Value::None], "(none,)");
@@ -599,9 +791,47 @@ mod tests {
 
         // Dictionary.
         let mut dict = BTreeMap::new();
+        test_pretty(dict.clone(), "(:)");
         dict.insert("one".into(), Value::Int(1));
+        test_pretty(dict.clone(), "(one: 1)");
         dict.insert("two".into(), Value::Bool(false));
-        test_pretty(BTreeMap::new(), "(:)");
         test_pretty(dict, "(one: 1, two: false)");
+
+        // Template.
+        test_pretty(
+            vec![
+                TemplateNode::Tree {
+                    tree: Rc::new(vec![Node::Strong]),
+                    map: HashMap::new(),
+                },
+                TemplateNode::Any(TemplateAny::new("example", |_| {})),
+            ],
+            "[*<example>]",
+        );
+
+        // Function and arguments.
+        test_pretty(ValueFunc::new("nil", |_, _| Value::None), "<nil>");
+        test_pretty(
+            ValueArgs {
+                span: Span::ZERO,
+                items: vec![
+                    ValueArg {
+                        name: Some(Spanned::zero("a".into())),
+                        value: Spanned::zero(Value::Int(1)),
+                    },
+                    ValueArg {
+                        name: None,
+                        value: Spanned::zero(Value::Int(2)),
+                    },
+                ],
+            },
+            "<a: 1, 2>",
+        );
+
+        // Any.
+        test_pretty(ValueAny::new(1), "1");
+
+        // Error.
+        test_pretty(Value::Error, "<error>");
     }
 }
diff --git a/src/exec/mod.rs b/src/exec/mod.rs
index 25edcce3..c323cf49 100644
--- a/src/exec/mod.rs
+++ b/src/exec/mod.rs
@@ -59,17 +59,23 @@ pub trait ExecWith {
 impl ExecWith for Tree {
     fn exec_with(&self, ctx: &mut ExecContext, map: &ExprMap) {
         for node in self {
-            match node {
-                Node::Text(text) => ctx.push_text(text),
-                Node::Space => ctx.push_space(),
-                Node::Linebreak => ctx.apply_linebreak(),
-                Node::Parbreak => ctx.apply_parbreak(),
-                Node::Strong => ctx.state.font.strong ^= true,
-                Node::Emph => ctx.state.font.emph ^= true,
-                Node::Heading(heading) => heading.exec_with(ctx, map),
-                Node::Raw(raw) => raw.exec(ctx),
-                Node::Expr(expr) => map[&(expr as *const _)].exec(ctx),
-            }
+            node.exec_with(ctx, map);
+        }
+    }
+}
+
+impl ExecWith for Node {
+    fn exec_with(&self, ctx: &mut ExecContext, map: &ExprMap) {
+        match self {
+            Node::Text(text) => ctx.push_text(text),
+            Node::Space => ctx.push_space(),
+            Node::Linebreak => ctx.apply_linebreak(),
+            Node::Parbreak => ctx.apply_parbreak(),
+            Node::Strong => ctx.state.font.strong ^= true,
+            Node::Emph => ctx.state.font.emph ^= true,
+            Node::Heading(heading) => heading.exec_with(ctx, map),
+            Node::Raw(raw) => raw.exec(ctx),
+            Node::Expr(expr) => map[&(expr as *const _)].exec(ctx),
         }
     }
 }
diff --git a/src/library/extend.rs b/src/library/extend.rs
index e388c9c8..6396274e 100644
--- a/src/library/extend.rs
+++ b/src/library/extend.rs
@@ -7,7 +7,7 @@ use crate::prelude::*;
 ///
 /// # Return value
 /// The name of the value's type as a string.
-pub fn type_(ctx: &mut EvalContext, args: &mut Args) -> Value {
+pub fn type_(ctx: &mut EvalContext, args: &mut ValueArgs) -> Value {
     if let Some(value) = args.require::<Value>(ctx, "value") {
         value.type_name().into()
     } else {
diff --git a/src/library/insert.rs b/src/library/insert.rs
index eff54e91..4f0f6489 100644
--- a/src/library/insert.rs
+++ b/src/library/insert.rs
@@ -10,12 +10,12 @@ use crate::prelude::*;
 ///
 /// # Positional arguments
 /// - Path to image file: of type `string`.
-pub fn image(ctx: &mut EvalContext, args: &mut Args) -> Value {
+pub fn image(ctx: &mut EvalContext, args: &mut ValueArgs) -> Value {
     let path = args.require::<Spanned<String>>(ctx, "path to image file");
     let width = args.get(ctx, "width");
     let height = args.get(ctx, "height");
 
-    Value::template(move |ctx| {
+    Value::template("image", move |ctx| {
         if let Some(path) = &path {
             let loaded = ctx.env.resources.load(&path.v, ImageResource::parse);
             if let Some((res, img)) = loaded {
diff --git a/src/library/layout.rs b/src/library/layout.rs
index 44c98536..3577ee36 100644
--- a/src/library/layout.rs
+++ b/src/library/layout.rs
@@ -26,14 +26,14 @@ use crate::prelude::*;
 ///     - `top`
 ///     - `bottom`
 ///     - `center`
-pub fn align(ctx: &mut EvalContext, args: &mut Args) -> Value {
+pub fn align(ctx: &mut EvalContext, args: &mut ValueArgs) -> Value {
     let first = args.find(ctx);
     let second = args.find(ctx);
     let hor = args.get(ctx, "horizontal");
     let ver = args.get(ctx, "vertical");
     let body = args.find::<ValueTemplate>(ctx);
 
-    Value::template(move |ctx| {
+    Value::template("align", move |ctx| {
         let snapshot = ctx.state.clone();
 
         let mut had = Gen::uniform(false);
@@ -157,7 +157,7 @@ impl Switch for Alignment {
     }
 }
 
-impl_type! {
+typify! {
     Alignment: "alignment",
 }
 
@@ -188,7 +188,7 @@ impl Display for Alignment {
 ///     - `rtl` (right to left)
 ///     - `ttb` (top to bottom)
 ///     - `btt` (bottom to top)
-pub fn box_(ctx: &mut EvalContext, args: &mut Args) -> Value {
+pub fn box_(ctx: &mut EvalContext, args: &mut ValueArgs) -> Value {
     let width = args.get(ctx, "width");
     let height = args.get(ctx, "height");
     let main = args.get(ctx, "main-dir");
@@ -196,7 +196,7 @@ pub fn box_(ctx: &mut EvalContext, args: &mut Args) -> Value {
     let color = args.get(ctx, "color");
     let body = args.find::<ValueTemplate>(ctx);
 
-    Value::template(move |ctx| {
+    Value::template("box", move |ctx| {
         let snapshot = ctx.state.clone();
 
         ctx.set_dirs(Gen::new(main, cross));
@@ -230,7 +230,7 @@ pub fn box_(ctx: &mut EvalContext, args: &mut Args) -> Value {
     })
 }
 
-impl_type! {
+typify! {
     Dir: "direction"
 }
 
@@ -238,7 +238,7 @@ impl_type! {
 ///
 /// # Positional arguments
 /// - Amount of spacing: of type `linear` relative to current font size.
-pub fn h(ctx: &mut EvalContext, args: &mut Args) -> Value {
+pub fn h(ctx: &mut EvalContext, args: &mut ValueArgs) -> Value {
     spacing(ctx, args, SpecAxis::Horizontal)
 }
 
@@ -246,15 +246,15 @@ pub fn h(ctx: &mut EvalContext, args: &mut Args) -> Value {
 ///
 /// # Positional arguments
 /// - Amount of spacing: of type `linear` relative to current font size.
-pub fn v(ctx: &mut EvalContext, args: &mut Args) -> Value {
+pub fn v(ctx: &mut EvalContext, args: &mut ValueArgs) -> Value {
     spacing(ctx, args, SpecAxis::Vertical)
 }
 
 /// Apply spacing along a specific axis.
-fn spacing(ctx: &mut EvalContext, args: &mut Args, axis: SpecAxis) -> Value {
+fn spacing(ctx: &mut EvalContext, args: &mut ValueArgs, axis: SpecAxis) -> Value {
     let spacing: Option<Linear> = args.require(ctx, "spacing");
 
-    Value::template(move |ctx| {
+    Value::template("spacing", move |ctx| {
         if let Some(linear) = spacing {
             let amount = linear.resolve(ctx.state.font.font_size());
             let spacing = NodeSpacing { amount, softness: Softness::Hard };
@@ -286,7 +286,7 @@ fn spacing(ctx: &mut EvalContext, args: &mut Args, axis: SpecAxis) -> Value {
 /// - Flip width and height:     `flip`, of type `bool`.
 /// - Main layouting direction:  `main-dir`, of type `direction`.
 /// - Cross layouting direction: `cross-dir`, of type `direction`.
-pub fn page(ctx: &mut EvalContext, args: &mut Args) -> Value {
+pub fn page(ctx: &mut EvalContext, args: &mut ValueArgs) -> Value {
     let paper = args.find::<Spanned<String>>(ctx).and_then(|name| {
         Paper::from_name(&name.v).or_else(|| {
             ctx.diag(error!(name.span, "invalid paper name"));
@@ -305,7 +305,7 @@ pub fn page(ctx: &mut EvalContext, args: &mut Args) -> Value {
     let cross = args.get(ctx, "cross-dir");
     let body = args.find::<ValueTemplate>(ctx);
 
-    Value::template(move |ctx| {
+    Value::template("page", move |ctx| {
         let snapshot = ctx.state.clone();
 
         if let Some(paper) = paper {
@@ -370,8 +370,8 @@ pub fn page(ctx: &mut EvalContext, args: &mut Args) -> Value {
 }
 
 /// `pagebreak`: Start a new page.
-pub fn pagebreak(_: &mut EvalContext, _: &mut Args) -> Value {
-    Value::template(move |ctx| {
+pub fn pagebreak(_: &mut EvalContext, _: &mut ValueArgs) -> Value {
+    Value::template("pagebreak", move |ctx| {
         ctx.end_page_group(|_| true);
         ctx.start_page_group(Softness::Hard);
     })
diff --git a/src/library/style.rs b/src/library/style.rs
index 23bd5298..35727515 100644
--- a/src/library/style.rs
+++ b/src/library/style.rs
@@ -54,7 +54,7 @@ use crate::prelude::*;
 ///     - `expanded`
 ///     - `extra-expanded`
 ///     - `ultra-expanded`
-pub fn font(ctx: &mut EvalContext, args: &mut Args) -> Value {
+pub fn font(ctx: &mut EvalContext, args: &mut ValueArgs) -> Value {
     let size = args.find::<Linear>(ctx);
     let list: Vec<_> = args.filter::<FontFamily>(ctx).map(|f| f.to_string()).collect();
     let style = args.get(ctx, "style");
@@ -65,7 +65,7 @@ pub fn font(ctx: &mut EvalContext, args: &mut Args) -> Value {
     let monospace = args.get(ctx, "monospace");
     let body = args.find::<ValueTemplate>(ctx);
 
-    Value::template(move |ctx| {
+    Value::template("font", move |ctx| {
         let snapshot = ctx.state.clone();
 
         if let Some(linear) = size {
@@ -145,7 +145,7 @@ impl Display for FontFamily {
     }
 }
 
-impl_type! {
+typify! {
     FontFamilies: "font family or array of font families",
     Value::Str(string) => Self(vec![FontFamily::Named(string.to_lowercase())]),
     Value::Array(values) => Self(values
@@ -156,16 +156,16 @@ impl_type! {
     #(family: FontFamily) => Self(vec![family]),
 }
 
-impl_type! {
+typify! {
     FontFamily: "font family",
     Value::Str(string) => Self::Named(string.to_lowercase())
 }
 
-impl_type! {
+typify! {
     FontStyle: "font style"
 }
 
-impl_type! {
+typify! {
     FontWeight: "font weight",
     Value::Int(number) => {
         let [min, max] = [Self::THIN, Self::BLACK];
@@ -180,7 +180,7 @@ impl_type! {
     },
 }
 
-impl_type! {
+typify! {
     FontStretch: "font stretch"
 }
 
@@ -191,7 +191,7 @@ impl_type! {
 /// - Green component: of type `float`, between 0.0 and 1.0.
 /// - Blue component:  of type `float`, between 0.0 and 1.0.
 /// - Alpha component: optional, of type `float`, between 0.0 and 1.0.
-pub fn rgb(ctx: &mut EvalContext, args: &mut Args) -> Value {
+pub fn rgb(ctx: &mut EvalContext, args: &mut ValueArgs) -> Value {
     let r = args.require(ctx, "red component");
     let g = args.require(ctx, "green component");
     let b = args.require(ctx, "blue component");
diff --git a/src/parse/collection.rs b/src/parse/collection.rs
index 162a8bd5..7ffc4539 100644
--- a/src/parse/collection.rs
+++ b/src/parse/collection.rs
@@ -51,29 +51,29 @@ fn collection<T: Collection>(p: &mut Parser, mut collection: T) -> T {
 }
 
 /// Parse an expression or a named pair.
-fn argument(p: &mut Parser) -> Option<Argument> {
+fn argument(p: &mut Parser) -> Option<ExprArg> {
     let first = expr(p)?;
     if p.eat_if(Token::Colon) {
         if let Expr::Ident(name) = first {
-            Some(Argument::Named(Named { name, expr: expr(p)? }))
+            Some(ExprArg::Named(Named { name, expr: expr(p)? }))
         } else {
             p.diag(error!(first.span(), "expected identifier"));
             expr(p);
             None
         }
     } else {
-        Some(Argument::Pos(first))
+        Some(ExprArg::Pos(first))
     }
 }
 
 /// Abstraction for comma-separated list of expression / named pairs.
 trait Collection {
-    fn push_arg(&mut self, p: &mut Parser, arg: Argument);
+    fn push_arg(&mut self, p: &mut Parser, arg: ExprArg);
     fn push_comma(&mut self) {}
 }
 
-impl Collection for Vec<Argument> {
-    fn push_arg(&mut self, _: &mut Parser, arg: Argument) {
+impl Collection for Vec<ExprArg> {
+    fn push_arg(&mut self, _: &mut Parser, arg: ExprArg) {
         self.push(arg);
     }
 }
@@ -99,23 +99,23 @@ impl State {
 }
 
 impl Collection for State {
-    fn push_arg(&mut self, p: &mut Parser, arg: Argument) {
+    fn push_arg(&mut self, p: &mut Parser, arg: ExprArg) {
         match self {
             Self::Unknown => match arg {
-                Argument::Pos(expr) => *self = Self::Expr(expr),
-                Argument::Named(named) => *self = Self::Dict(vec![named]),
+                ExprArg::Pos(expr) => *self = Self::Expr(expr),
+                ExprArg::Named(named) => *self = Self::Dict(vec![named]),
             },
             Self::Expr(prev) => match arg {
-                Argument::Pos(expr) => *self = Self::Array(vec![take(prev), expr]),
-                Argument::Named(_) => diag(p, arg),
+                ExprArg::Pos(expr) => *self = Self::Array(vec![take(prev), expr]),
+                ExprArg::Named(_) => diag(p, arg),
             },
             Self::Array(array) => match arg {
-                Argument::Pos(expr) => array.push(expr),
-                Argument::Named(_) => diag(p, arg),
+                ExprArg::Pos(expr) => array.push(expr),
+                ExprArg::Named(_) => diag(p, arg),
             },
             Self::Dict(dict) => match arg {
-                Argument::Pos(_) => diag(p, arg),
-                Argument::Named(named) => dict.push(named),
+                ExprArg::Pos(_) => diag(p, arg),
+                ExprArg::Named(named) => dict.push(named),
             },
         }
     }
@@ -135,9 +135,9 @@ fn take(expr: &mut Expr) -> Expr {
     )
 }
 
-fn diag(p: &mut Parser, arg: Argument) {
+fn diag(p: &mut Parser, arg: ExprArg) {
     p.diag(error!(arg.span(), "{}", match arg {
-        Argument::Pos(_) => "expected named pair, found expression",
-        Argument::Named(_) => "expected expression, found named pair",
+        ExprArg::Pos(_) => "expected named pair, found expression",
+        ExprArg::Named(_) => "expected expression, found named pair",
     }));
 }
diff --git a/src/parse/mod.rs b/src/parse/mod.rs
index 2c34d7b8..e7e25a1d 100644
--- a/src/parse/mod.rs
+++ b/src/parse/mod.rs
@@ -198,11 +198,11 @@ fn bracket_call(p: &mut Parser) -> Option<Expr> {
     let mut inner = inner?;
     if let Some(body) = body {
         inner.span.expand(body.span());
-        inner.args.items.push(Argument::Pos(body));
+        inner.args.items.push(ExprArg::Pos(body));
     }
 
     while let Some(mut top) = outer.pop() {
-        top.args.items.push(Argument::Pos(Expr::Call(inner)));
+        top.args.items.push(ExprArg::Pos(Expr::Call(inner)));
         inner = top;
     }
 
diff --git a/src/prelude.rs b/src/prelude.rs
index 6bab80e6..3f5bcab7 100644
--- a/src/prelude.rs
+++ b/src/prelude.rs
@@ -3,7 +3,7 @@
 pub use crate::diag::{Feedback, Pass};
 #[doc(no_inline)]
 pub use crate::eval::{
-    Args, CastResult, Eval, EvalContext, TemplateAny, TemplateNode, Value, ValueAny,
+    CastResult, Eval, EvalContext, TemplateAny, TemplateNode, Value, ValueAny, ValueArgs,
     ValueArray, ValueDict, ValueTemplate,
 };
 #[doc(no_inline)]
@@ -13,4 +13,4 @@ pub use crate::geom::*;
 pub use crate::layout::Node;
 #[doc(no_inline)]
 pub use crate::syntax::{Span, Spanned, WithSpan};
-pub use crate::{error, impl_type, warning};
+pub use crate::{error, typify, warning};
diff --git a/src/pretty.rs b/src/pretty.rs
index 0123e9a7..e01955cd 100644
--- a/src/pretty.rs
+++ b/src/pretty.rs
@@ -105,7 +105,7 @@ impl Pretty for str {
     }
 }
 
-macro_rules! impl_pretty_display {
+macro_rules! pretty_display {
     ($($type:ty),* $(,)?) => {
         $(impl Pretty for $type {
             fn pretty(&self, p: &mut Printer) {
@@ -115,7 +115,7 @@ macro_rules! impl_pretty_display {
     };
 }
 
-impl_pretty_display! {
+pretty_display! {
     bool,
     Length,
     Angle,
diff --git a/src/syntax/expr.rs b/src/syntax/expr.rs
index f431ba8d..8a11ebc4 100644
--- a/src/syntax/expr.rs
+++ b/src/syntax/expr.rs
@@ -531,7 +531,7 @@ impl ExprCall {
         // Function name.
         self.callee.pretty(p);
 
-        let mut write_args = |items: &[Argument]| {
+        let mut write_args = |items: &[ExprArg]| {
             if !items.is_empty() {
                 p.push(' ');
                 p.join(items, ", ", |item, p| item.pretty(p));
@@ -542,7 +542,7 @@ impl ExprCall {
             // This can written as a chain.
             //
             // Example: Transforms "#[v][[f]]" => "#[v | f]".
-            [head @ .., Argument::Pos(Expr::Call(call))] => {
+            [head @ .., ExprArg::Pos(Expr::Call(call))] => {
                 write_args(head);
                 call.pretty_bracketed(p, true);
             }
@@ -550,7 +550,7 @@ impl ExprCall {
             // This can be written with a body.
             //
             // Example: Transforms "#[v [Hi]]" => "#[v][Hi]".
-            [head @ .., Argument::Pos(Expr::Template(template))] => {
+            [head @ .., ExprArg::Pos(Expr::Template(template))] => {
                 write_args(head);
                 p.push(']');
                 template.pretty(p);
@@ -573,7 +573,7 @@ pub struct ExprArgs {
     /// The source code location.
     pub span: Span,
     /// The positional and named arguments.
-    pub items: Vec<Argument>,
+    pub items: Vec<ExprArg>,
 }
 
 impl Pretty for ExprArgs {
@@ -584,14 +584,14 @@ impl Pretty for ExprArgs {
 
 /// An argument to a function call: `12` or `draw: false`.
 #[derive(Debug, Clone, PartialEq)]
-pub enum Argument {
-    /// A positional arguments.
+pub enum ExprArg {
+    /// A positional argument.
     Pos(Expr),
     /// A named argument.
     Named(Named),
 }
 
-impl Argument {
+impl ExprArg {
     /// The source code location.
     pub fn span(&self) -> Span {
         match self {
@@ -601,7 +601,7 @@ impl Argument {
     }
 }
 
-impl Pretty for Argument {
+impl Pretty for ExprArg {
     fn pretty(&self, p: &mut Printer) {
         match self {
             Self::Pos(expr) => expr.pretty(p),
diff --git a/src/syntax/node.rs b/src/syntax/node.rs
index fe9767a1..246790f6 100644
--- a/src/syntax/node.rs
+++ b/src/syntax/node.rs
@@ -31,6 +31,7 @@ impl Pretty for Node {
             Self::Space => p.push(' '),
             Self::Linebreak => p.push_str(r"\"),
             Self::Parbreak => p.push_str("\n\n"),
+            // TODO: Handle escaping.
             Self::Text(text) => p.push_str(&text),
             Self::Heading(heading) => heading.pretty(p),
             Self::Raw(raw) => raw.pretty(p),
diff --git a/src/syntax/visit.rs b/src/syntax/visit.rs
index 70159d2d..2d3c683f 100644
--- a/src/syntax/visit.rs
+++ b/src/syntax/visit.rs
@@ -111,10 +111,10 @@ visit! {
         }
     }
 
-    fn visit_arg(v, node: &Argument) {
+    fn visit_arg(v, node: &ExprArg) {
         match node {
-            Argument::Pos(expr) => v.visit_expr(&expr),
-            Argument::Named(named) => v.visit_expr(&named.expr),
+            ExprArg::Pos(expr) => v.visit_expr(&expr),
+            ExprArg::Named(named) => v.visit_expr(&named.expr),
         }
     }