Named arguments for user defined functions

2 files changed, 27 insertions, 8 deletions

diff --git a/src/syntax/expr.rs b/src/syntax/expr.rs
index cf9aff4a..9292d5b6 100644
--- a/src/syntax/expr.rs
+++ b/src/syntax/expr.rs
@@ -437,11 +437,20 @@ pub struct ClosureExpr {
     /// This only exists if you use the function syntax sugar: `let f(x) = y`.
     pub name: Option<Ident>,
     /// The parameter bindings.
-    pub params: Rc<Vec<Ident>>,
+    pub params: Vec<ClosureParam>,
     /// The body of the closure.
     pub body: Rc<Expr>,
 }
 
+/// An parameter to a closure: `x` or `draw: false`.
+#[derive(Debug, Clone, PartialEq)]
+pub enum ClosureParam {
+    /// A positional parameter.
+    Pos(Ident),
+    /// A named parameter with a default value.
+    Named(Named),
+}
+
 /// A with expression: `f with (x, y: 1)`.
 ///
 /// Applies arguments to a function.
diff --git a/src/syntax/visit.rs b/src/syntax/visit.rs
index 81cba5c7..bc9359b3 100644
--- a/src/syntax/visit.rs
+++ b/src/syntax/visit.rs
@@ -192,13 +192,6 @@ impl_visitors! {
         v.visit_args(r!(call.args));
     }
 
-    visit_closure(v, closure: ClosureExpr) {
-        for param in r!(rc: closure.params) {
-            v.visit_binding(param);
-        }
-        v.visit_expr(r!(rc: closure.body));
-    }
-
     visit_args(v, args: CallArgs) {
         for arg in r!(args.items) {
             v.visit_arg(arg);
@@ -212,6 +205,23 @@ impl_visitors! {
         }
     }
 
+    visit_closure(v, closure: ClosureExpr) {
+        for param in r!(closure.params) {
+            v.visit_param(param);
+        }
+        v.visit_expr(r!(rc: closure.body));
+    }
+
+    visit_param(v, param: ClosureParam) {
+        match param {
+            ClosureParam::Pos(binding) => v.visit_binding(binding),
+            ClosureParam::Named(named) => {
+                v.visit_binding(r!(named.name));
+                v.visit_expr(r!(named.expr));
+            }
+        }
+    }
+
     visit_with(v, with_expr: WithExpr) {
         v.visit_expr(r!(with_expr.callee));
         v.visit_args(r!(with_expr.args));