2 files changed, 17 insertions, 4 deletions
diff --git a/src/syntax/ast.rs b/src/syntax/ast.rs
index 4119802e..e492297a 100644
--- a/src/syntax/ast.rs
+++ b/src/syntax/ast.rs
@@ -1570,7 +1570,7 @@ pub enum Param {
     /// A named parameter with a default value: `draw: false`.
     Named(Named),
     /// An argument sink: `..args`.
-    Sink(Ident),
+    Sink(Option<Ident>),
 }
 
 impl AstNode for Param {
@@ -1578,7 +1578,7 @@ impl AstNode for Param {
         match node.kind() {
             SyntaxKind::Ident => node.cast().map(Self::Pos),
             SyntaxKind::Named => node.cast().map(Self::Named),
-            SyntaxKind::Spread => node.cast_first_match().map(Self::Sink),
+            SyntaxKind::Spread => Some(Self::Sink(node.cast_first_match())),
             _ => Option::None,
         }
     }
@@ -1587,7 +1587,7 @@ impl AstNode for Param {
         match self {
             Self::Pos(v) => v.as_untyped(),
             Self::Named(v) => v.as_untyped(),
-            Self::Sink(v) => v.as_untyped(),
+            Self::Sink(_) => self.as_untyped(),
         }
     }
 }
diff --git a/src/syntax/parser.rs b/src/syntax/parser.rs
index 42183f3a..7c05eebc 100644
--- a/src/syntax/parser.rs
+++ b/src/syntax/parser.rs
@@ -1069,6 +1069,7 @@ fn validate_dict(p: &mut Parser, m: Marker) {
 }
 
 fn validate_params(p: &mut Parser, m: Marker) {
+    let mut used_spread = false;
     let mut used = HashSet::new();
     for child in p.post_process(m) {
         match child.kind() {
@@ -1086,12 +1087,24 @@ fn validate_params(p: &mut Parser, m: Marker) {
             }
             SyntaxKind::Spread => {
                 let Some(within) = child.children_mut().last_mut() else { continue };
-                if within.kind() != SyntaxKind::Ident {
+                if used_spread {
+                    child.convert_to_error("only one argument sink is allowed");
+                    continue;
+                }
+                used_spread = true;
+                if within.kind() == SyntaxKind::Dots {
+                    continue;
+                } else if within.kind() != SyntaxKind::Ident {
                     within.convert_to_error(eco_format!(
                         "expected identifier, found {}",
                         within.kind().name(),
                     ));
                     child.make_erroneous();
+                    continue;
+                }
+                if !used.insert(within.text().clone()) {
+                    within.convert_to_error("duplicate parameter");
+                    child.make_erroneous();
                 }
             }
             SyntaxKind::LeftParen | SyntaxKind::RightParen | SyntaxKind::Comma => {}