Proper error messages for shorthands

macros/src/lib.rs

@@ -56,20 +56,23 @@ fn expand(mut impl_block: syn::ItemImpl) -> Result<TokenStream2> {
             let name = property.name;
             let string = name.to_string().replace("_", "-").to_lowercase();
 
-            let alternative = if property.variadic {
+            let value = if property.variadic {
                 quote! {
-                    .or_else(|| {
-                        let list: Vec<_> = args.all().collect();
-                        (!list.is_empty()).then(|| list)
-                    })
+                    match args.named(#string)? {
+                        Some(value) => value,
+                        None => {
+                            let list: Vec<_> = args.all()?;
+                            (!list.is_empty()).then(|| list)
+                        }
+                    }
                 }
             } else if property.shorthand {
-                quote! { .or_else(|| args.find()) }
+                quote! { args.named_or_find(#string)? }
             } else {
-                quote! {}
+                quote! { args.named(#string)? }
             };
 
-            quote! { styles.set_opt(Self::#name, args.named(#string)? #alternative); }
+            quote! { styles.set_opt(Self::#name, #value); }
         });
 
         parse_quote! {

src/eval/func.rs

@@ -162,10 +162,7 @@ impl Args {
     ///
     /// Returns a `missing argument: {what}` error if no positional argument is
     /// left.
-    pub fn expect<T>(&mut self, what: &str) -> TypResult<T>
-    where
-        T: Cast<Spanned<Value>>,
-    {
+    pub fn expect<T: Cast>(&mut self, what: &str) -> TypResult<T> {
         match self.eat()? {
             Some(v) => Ok(v),
             None => bail!(self.span, "missing argument: {}", what),
@@ -173,10 +170,7 @@ impl Args {
     }
 
     /// Consume and cast the first positional argument if there is one.
-    pub fn eat<T>(&mut self) -> TypResult<Option<T>>
-    where
-        T: Cast<Spanned<Value>>,
-    {
+    pub fn eat<T: Cast>(&mut self) -> TypResult<Option<T>> {
         for (i, slot) in self.items.iter().enumerate() {
             if slot.name.is_none() {
                 let value = self.items.remove(i).value;
@@ -188,33 +182,29 @@ impl Args {
     }
 
     /// Find and consume the first castable positional argument.
-    pub fn find<T>(&mut self) -> Option<T>
-    where
-        T: Cast<Spanned<Value>>,
-    {
+    pub fn find<T: Cast>(&mut self) -> TypResult<Option<T>> {
         for (i, slot) in self.items.iter().enumerate() {
             if slot.name.is_none() && T::is(&slot.value) {
                 let value = self.items.remove(i).value;
-                return T::cast(value).ok();
+                let span = value.span;
+                return T::cast(value).at(span).map(Some);
             }
         }
-        None
+        Ok(None)
     }
 
     /// Find and consume all castable positional arguments.
-    pub fn all<T>(&mut self) -> impl Iterator<Item = T> + '_
-    where
-        T: Cast<Spanned<Value>>,
-    {
-        std::iter::from_fn(move || self.find())
+    pub fn all<T: Cast>(&mut self) -> TypResult<Vec<T>> {
+        let mut list = vec![];
+        while let Some(value) = self.find()? {
+            list.push(value);
+        }
+        Ok(list)
     }
 
     /// Cast and remove the value for the given named argument, returning an
     /// error if the conversion fails.
-    pub fn named<T>(&mut self, name: &str) -> TypResult<Option<T>>
-    where
-        T: Cast<Spanned<Value>>,
-    {
+    pub fn named<T: Cast>(&mut self, name: &str) -> TypResult<Option<T>> {
         // We don't quit once we have a match because when multiple matches
         // exist, we want to remove all of them and use the last one.
         let mut i = 0;
@@ -231,6 +221,14 @@ impl Args {
         Ok(found)
     }
 
+    /// Same as named, but with fallback to find.
+    pub fn named_or_find<T: Cast>(&mut self, name: &str) -> TypResult<Option<T>> {
+        match self.named(name)? {
+            Some(value) => Ok(Some(value)),
+            None => self.find(),
+        }
+    }
+
     /// Take out all arguments into a new instance.
     pub fn take(&mut self) -> Self {
         Self {

src/eval/value.rs

@@ -284,7 +284,7 @@ pub trait Type {
 }
 
 /// Cast from a value to a specific type.
-pub trait Cast<V>: Sized {
+pub trait Cast<V = Spanned<Value>>: Sized {
     /// Check whether the value is castable to `Self`.
     fn is(value: &V) -> bool;
 
@@ -415,7 +415,7 @@ impl Cast<Value> for Value {
     }
 }
 
-impl<T> Cast<Spanned<Value>> for T
+impl<T> Cast for T
 where
     T: Cast<Value>,
 {
@@ -428,7 +428,7 @@ where
     }
 }
 
-impl<T> Cast<Spanned<Value>> for Spanned<T>
+impl<T> Cast for Spanned<T>
 where
     T: Cast<Value>,
 {

src/library/align.rs

@@ -15,7 +15,7 @@ pub struct AlignNode {
 #[class]
 impl AlignNode {
     fn construct(_: &mut EvalContext, args: &mut Args) -> TypResult<Template> {
-        let aligns: Spec<_> = args.find().unwrap_or_default();
+        let aligns: Spec<_> = args.find()?.unwrap_or_default();
         let body: LayoutNode = args.expect("body")?;
         Ok(Template::block(body.aligned(aligns)))
     }

src/library/container.rs

@@ -10,7 +10,7 @@ impl BoxNode {
     fn construct(_: &mut EvalContext, args: &mut Args) -> TypResult<Template> {
         let width = args.named("width")?;
         let height = args.named("height")?;
-        let body: LayoutNode = args.find().unwrap_or_default();
+        let body: LayoutNode = args.find()?.unwrap_or_default();
         Ok(Template::inline(body.sized(Spec::new(width, height))))
     }
 }
@@ -21,6 +21,6 @@ pub struct BlockNode;
 #[class]
 impl BlockNode {
     fn construct(_: &mut EvalContext, args: &mut Args) -> TypResult<Template> {
-        Ok(Template::Block(args.find().unwrap_or_default()))
+        Ok(Template::Block(args.find()?.unwrap_or_default()))
     }
 }

src/library/grid.rs

@@ -27,7 +27,7 @@ impl GridNode {
                 column_gutter.unwrap_or_else(|| base_gutter.clone()),
                 row_gutter.unwrap_or(base_gutter),
             ),
-            children: args.all().collect(),
+            children: args.all()?,
         }))
     }
 }

src/library/link.rs

@@ -23,7 +23,7 @@ impl LinkNode {
 
     fn construct(_: &mut EvalContext, args: &mut Args) -> TypResult<Template> {
         let url = args.expect::<EcoString>("url")?;
-        let body = args.find().unwrap_or_else(|| {
+        let body = args.find()?.unwrap_or_else(|| {
             let mut text = url.as_str();
             for prefix in ["mailto:", "tel:"] {
                 text = text.trim_start_matches(prefix);

src/library/list.rs

@@ -21,7 +21,8 @@ impl<L: ListLabel> ListNode<L> {
 
     fn construct(_: &mut EvalContext, args: &mut Args) -> TypResult<Template> {
         Ok(args
-            .all()
+            .all()?
+            .into_iter()
             .enumerate()
             .map(|(i, child)| Template::show(Self { label: L::new(1 + i), child }))
             .sum())

src/library/pad.rs

@@ -14,7 +14,7 @@ pub struct PadNode {
 #[class]
 impl PadNode {
     fn construct(_: &mut EvalContext, args: &mut Args) -> TypResult<Template> {
-        let all = args.find();
+        let all = args.find()?;
         let left = args.named("left")?;
         let top = args.named("top")?;
         let right = args.named("right")?;

src/library/page.rs

@@ -36,7 +36,7 @@ impl PageNode {
     }
 
     fn set(args: &mut Args, styles: &mut StyleMap) -> TypResult<()> {
-        if let Some(paper) = args.named::<Paper>("paper")?.or_else(|| args.find()) {
+        if let Some(paper) = args.named_or_find::<Paper>("paper")? {
             styles.set(Self::WIDTH, Smart::Custom(paper.width()));
             styles.set(Self::HEIGHT, Smart::Custom(paper.height()));
         }

src/library/place.rs

@@ -10,7 +10,7 @@ pub struct PlaceNode(pub LayoutNode);
 #[class]
 impl PlaceNode {
     fn construct(_: &mut EvalContext, args: &mut Args) -> TypResult<Template> {
-        let aligns = args.find().unwrap_or(Spec::with_x(Some(Align::Left)));
+        let aligns = args.find()?.unwrap_or(Spec::with_x(Some(Align::Left)));
         let tx = args.named("dx")?.unwrap_or_default();
         let ty = args.named("dy")?.unwrap_or_default();
         let body: LayoutNode = args.expect("body")?;

src/library/shape.rs

@@ -45,7 +45,7 @@ impl<S: ShapeKind> ShapeNode<S> {
         };
 
         Ok(Template::inline(
-            ShapeNode { kind: S::default(), child: args.find() }
+            ShapeNode { kind: S::default(), child: args.find()? }
                 .pack()
                 .sized(Spec::new(width, height)),
         ))

src/library/stack.rs

@@ -20,7 +20,7 @@ impl StackNode {
         Ok(Template::block(Self {
             dir: args.named("dir")?.unwrap_or(Dir::TTB),
             spacing: args.named("spacing")?,
-            children: args.all().collect(),
+            children: args.all()?,
         }))
     }
 }

src/library/table.rs

@@ -39,7 +39,7 @@ impl TableNode {
                 column_gutter.unwrap_or_else(|| base_gutter.clone()),
                 row_gutter.unwrap_or(base_gutter),
             ),
-            children: args.all().collect(),
+            children: args.all()?,
         }))
     }
 

src/library/transform.rs

@@ -78,9 +78,7 @@ pub struct Rotate(pub Angle);
 
 impl TransformKind for Rotate {
     fn construct(args: &mut Args) -> TypResult<Self> {
-        Ok(Self(
-            args.named("angle")?.or_else(|| args.find()).unwrap_or_default(),
-        ))
+        Ok(Self(args.named_or_find("angle")?.unwrap_or_default()))
     }
 
     fn matrix(&self) -> Transform {
@@ -94,7 +92,7 @@ pub struct Scale(pub Relative, pub Relative);
 
 impl TransformKind for Scale {
     fn construct(args: &mut Args) -> TypResult<Self> {
-        let all = args.find();
+        let all = args.find()?;
         let sx = args.named("x")?.or(all).unwrap_or(Relative::one());
         let sy = args.named("y")?.or(all).unwrap_or(Relative::one());
         Ok(Self(sx, sy))

src/library/utility.rs

@@ -31,7 +31,7 @@ pub fn join(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
     let sep = args.named::<Value>("sep")?.unwrap_or(Value::None);
 
     let mut result = Value::None;
-    let mut iter = args.all::<Value>();
+    let mut iter = args.all::<Value>()?.into_iter();
 
     if let Some(first) = iter.next() {
         result = first;
@@ -88,7 +88,7 @@ pub fn str(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
 /// Create an RGB(A) color.
 pub fn rgb(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
     Ok(Value::from(
-        if let Some(string) = args.find::<Spanned<EcoString>>() {
+        if let Some(string) = args.find::<Spanned<EcoString>>()? {
             match RgbaColor::from_str(&string.v) {
                 Ok(color) => color,
                 Err(_) => bail!(string.span, "invalid hex string"),
@@ -208,7 +208,7 @@ pub fn modulo(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
 /// Find the minimum or maximum of a sequence of values.
 fn minmax(args: &mut Args, goal: Ordering) -> TypResult<Value> {
     let mut extremum = args.expect::<Value>("value")?;
-    for Spanned { v, span } in args.all::<Spanned<Value>>() {
+    for Spanned { v, span } in args.all::<Spanned<Value>>()? {
         match v.partial_cmp(&extremum) {
             Some(ordering) => {
                 if ordering == goal {