Spreading into arrays and dictionaries

3 files changed, 115 insertions, 40 deletions

diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index 3f580178..9e5a8555 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -39,6 +39,8 @@ pub use show::*;
 pub use styles::*;
 pub use value::*;
 
+use std::collections::BTreeMap;
+
 use parking_lot::{MappedRwLockWriteGuard, RwLockWriteGuard};
 use unicode_segmentation::UnicodeSegmentation;
 
@@ -307,7 +309,21 @@ impl Eval for ArrayExpr {
     type Output = Array;
 
     fn eval(&self, ctx: &mut Context, scp: &mut Scopes) -> EvalResult<Self::Output> {
-        self.items().map(|expr| expr.eval(ctx, scp)).collect()
+        let items = self.items();
+
+        let mut vec = Vec::with_capacity(items.size_hint().0);
+        for item in items {
+            match item {
+                ArrayItem::Pos(expr) => vec.push(expr.eval(ctx, scp)?),
+                ArrayItem::Spread(expr) => match expr.eval(ctx, scp)? {
+                    Value::None => {}
+                    Value::Array(array) => vec.extend(array.into_iter()),
+                    v => bail!(expr.span(), "cannot spread {} into array", v.type_name()),
+                },
+            }
+        }
+
+        Ok(Array::from_vec(vec))
     }
 }
 
@@ -315,9 +331,26 @@ impl Eval for DictExpr {
     type Output = Dict;
 
     fn eval(&self, ctx: &mut Context, scp: &mut Scopes) -> EvalResult<Self::Output> {
-        self.items()
-            .map(|x| Ok((x.name().take(), x.expr().eval(ctx, scp)?)))
-            .collect()
+        let mut map = BTreeMap::new();
+
+        for item in self.items() {
+            match item {
+                DictItem::Named(named) => {
+                    map.insert(named.name().take(), named.expr().eval(ctx, scp)?);
+                }
+                DictItem::Spread(expr) => match expr.eval(ctx, scp)? {
+                    Value::None => {}
+                    Value::Dict(dict) => map.extend(dict.into_iter()),
+                    v => bail!(
+                        expr.span(),
+                        "cannot spread {} into dictionary",
+                        v.type_name()
+                    ),
+                },
+            }
+        }
+
+        Ok(Dict::from_map(map))
     }
 }
 
diff --git a/src/parse/mod.rs b/src/parse/mod.rs
index 28b7f81d..3bf274f2 100644
--- a/src/parse/mod.rs
+++ b/src/parse/mod.rs
@@ -516,7 +516,7 @@ fn parenthesized(p: &mut Parser, atomic: bool) -> ParseResult {
     let kind = collection(p).0;
     p.end_group();
 
-    // Leading colon makes this a (empty) dictionary.
+    // Leading colon makes this a dictionary.
     if colon {
         dict(p, marker);
         return Ok(());
@@ -556,21 +556,23 @@ enum CollectionKind {
 /// Returns the length of the collection and whether the literal contained any
 /// commas.
 fn collection(p: &mut Parser) -> (CollectionKind, usize) {
-    let mut kind = CollectionKind::Positional;
+    let mut kind = None;
     let mut items = 0;
     let mut can_group = true;
-    let mut error = false;
     let mut missing_coma: Option<Marker> = None;
 
     while !p.eof() {
         if let Ok(item_kind) = item(p) {
-            if items == 0 && item_kind == NodeKind::Named {
-                kind = CollectionKind::Named;
-                can_group = false;
-            }
-
-            if item_kind == NodeKind::Spread {
-                can_group = false;
+            match item_kind {
+                NodeKind::Spread => can_group = false,
+                NodeKind::Named if kind.is_none() => {
+                    kind = Some(CollectionKind::Named);
+                    can_group = false;
+                }
+                _ if kind.is_none() => {
+                    kind = Some(CollectionKind::Positional);
+                }
+                _ => {}
             }
 
             items += 1;
@@ -589,13 +591,15 @@ fn collection(p: &mut Parser) -> (CollectionKind, usize) {
                 missing_coma = Some(p.trivia_start());
             }
         } else {
-            error = true;
+            kind = Some(CollectionKind::Group);
         }
     }
 
-    if error || (can_group && items == 1) {
-        kind = CollectionKind::Group;
-    }
+    let kind = if can_group && items == 1 {
+        CollectionKind::Group
+    } else {
+        kind.unwrap_or(CollectionKind::Positional)
+    };
 
     (kind, items)
 }
@@ -636,7 +640,6 @@ fn item(p: &mut Parser) -> ParseResult<NodeKind> {
 fn array(p: &mut Parser, marker: Marker) {
     marker.filter_children(p, |x| match x.kind() {
         NodeKind::Named => Err("expected expression, found named pair"),
-        NodeKind::Spread => Err("spreading is not allowed here"),
         _ => Ok(()),
     });
     marker.end(p, NodeKind::ArrayExpr);
@@ -647,8 +650,7 @@ fn array(p: &mut Parser, marker: Marker) {
 fn dict(p: &mut Parser, marker: Marker) {
     marker.filter_children(p, |x| match x.kind() {
         kind if kind.is_paren() => Ok(()),
-        NodeKind::Named | NodeKind::Comma | NodeKind::Colon => Ok(()),
-        NodeKind::Spread => Err("spreading is not allowed here"),
+        NodeKind::Named | NodeKind::Comma | NodeKind::Colon | NodeKind::Spread => Ok(()),
         _ => Err("expected named pair, found expression"),
     });
     marker.end(p, NodeKind::DictExpr);
diff --git a/src/syntax/ast.rs b/src/syntax/ast.rs
index 087b8d77..1318852d 100644
--- a/src/syntax/ast.rs
+++ b/src/syntax/ast.rs
@@ -447,11 +447,36 @@ node! {
 
 impl ArrayExpr {
     /// The array items.
-    pub fn items(&self) -> impl Iterator<Item = Expr> + '_ {
+    pub fn items(&self) -> impl Iterator<Item = ArrayItem> + '_ {
         self.0.children().filter_map(RedRef::cast)
     }
 }
 
+/// An item in an array expresssion.
+#[derive(Debug, Clone, PartialEq, Hash)]
+pub enum ArrayItem {
+    /// A simple value: `12`.
+    Pos(Expr),
+    /// A spreaded value: `..things`.
+    Spread(Expr),
+}
+
+impl TypedNode for ArrayItem {
+    fn from_red(node: RedRef) -> Option<Self> {
+        match node.kind() {
+            NodeKind::Spread => node.cast_first_child().map(Self::Spread),
+            _ => node.cast().map(Self::Pos),
+        }
+    }
+
+    fn as_red(&self) -> RedRef<'_> {
+        match self {
+            Self::Pos(v) => v.as_red(),
+            Self::Spread(v) => v.as_red(),
+        }
+    }
+}
+
 node! {
     /// A dictionary expression: `(thickness: 3pt, pattern: dashed)`.
     DictExpr: DictExpr
@@ -459,11 +484,37 @@ node! {
 
 impl DictExpr {
     /// The named dictionary items.
-    pub fn items(&self) -> impl Iterator<Item = Named> + '_ {
+    pub fn items(&self) -> impl Iterator<Item = DictItem> + '_ {
         self.0.children().filter_map(RedRef::cast)
     }
 }
 
+/// An item in an dictionary expresssion.
+#[derive(Debug, Clone, PartialEq, Hash)]
+pub enum DictItem {
+    /// A simple named pair: `12`.
+    Named(Named),
+    /// A spreaded value: `..things`.
+    Spread(Expr),
+}
+
+impl TypedNode for DictItem {
+    fn from_red(node: RedRef) -> Option<Self> {
+        match node.kind() {
+            NodeKind::Named => node.cast().map(Self::Named),
+            NodeKind::Spread => node.cast_first_child().map(Self::Spread),
+            _ => None,
+        }
+    }
+
+    fn as_red(&self) -> RedRef<'_> {
+        match self {
+            Self::Named(v) => v.as_red(),
+            Self::Spread(v) => v.as_red(),
+        }
+    }
+}
+
 node! {
     /// A pair of a name and an expression: `pattern: dashed`.
     Named
@@ -801,9 +852,9 @@ pub enum CallArg {
 impl TypedNode for CallArg {
     fn from_red(node: RedRef) -> Option<Self> {
         match node.kind() {
-            NodeKind::Named => node.cast().map(CallArg::Named),
-            NodeKind::Spread => node.cast_first_child().map(CallArg::Spread),
-            _ => node.cast().map(CallArg::Pos),
+            NodeKind::Named => node.cast().map(Self::Named),
+            NodeKind::Spread => node.cast_first_child().map(Self::Spread),
+            _ => node.cast().map(Self::Pos),
         }
     }
 
@@ -816,17 +867,6 @@ impl TypedNode for CallArg {
     }
 }
 
-impl CallArg {
-    /// The name of this argument.
-    pub fn span(&self) -> Span {
-        match self {
-            Self::Pos(expr) => expr.span(),
-            Self::Named(named) => named.span(),
-            Self::Spread(expr) => expr.span(),
-        }
-    }
-}
-
 node! {
     /// A closure expression: `(x, y) => z`.
     ClosureExpr: ClosureExpr
@@ -870,9 +910,9 @@ pub enum ClosureParam {
 impl TypedNode for ClosureParam {
     fn from_red(node: RedRef) -> Option<Self> {
         match node.kind() {
-            NodeKind::Ident(_) => node.cast().map(ClosureParam::Pos),
-            NodeKind::Named => node.cast().map(ClosureParam::Named),
-            NodeKind::Spread => node.cast_first_child().map(ClosureParam::Sink),
+            NodeKind::Ident(_) => node.cast().map(Self::Pos),
+            NodeKind::Named => node.cast().map(Self::Named),
+            NodeKind::Spread => node.cast_first_child().map(Self::Sink),
             _ => None,
         }
     }