1 files changed, 125 insertions, 0 deletions
diff --git a/src/syntax/func.rs b/src/syntax/func.rs
new file mode 100644
index 00000000..5b1ce6e8
--- /dev/null
+++ b/src/syntax/func.rs
@@ -0,0 +1,125 @@
+use super::*;
+
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct FuncHeader {
+    pub name: Spanned<Ident>,
+    pub args: FuncArgs,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct FuncArgs {
+    pub pos: Tuple,
+    pub key: Object,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum Arg {
+    Pos(Spanned<Expression>),
+    Key(Pair),
+}
+
+impl Arg {
+    /// The span or the value or combined span of key and value.
+    pub fn span(&self) -> Span {
+        match self {
+            Arg::Pos(item) => item.span,
+            Arg::Key(Pair { key, value }) => Span::merge(key.span, value.span),
+        }
+    }
+}
+
+impl FuncArgs {
+    pub fn new() -> FuncArgs {
+        FuncArgs {
+            pos: Tuple::new(),
+            key: Object::new(),
+        }
+    }
+
+    /// Add an argument.
+    pub fn add(&mut self, arg: Arg) {
+        match arg {
+            Arg::Pos(item) => self.add_pos(item),
+            Arg::Key(pair) => self.add_key_pair(pair),
+        }
+    }
+
+    /// Add a positional argument.
+    pub fn add_pos(&mut self, item: Spanned<Expression>) {
+        self.pos.add(item);
+    }
+
+    /// Add a keyword argument.
+    pub fn add_key(&mut self, key: Spanned<Ident>, value: Spanned<Expression>) {
+        self.key.add(key, value);
+    }
+
+    /// Add a keyword argument from an existing pair.
+    pub fn add_key_pair(&mut self, pair: Pair) {
+        self.key.add_pair(pair);
+    }
+
+    // /// Force-extract the first positional argument.
+    // pub fn get_pos<E: ExpressionKind>(&mut self) -> ParseResult<E> {
+    //     expect(self.get_pos_opt())
+    // }
+
+    // /// Extract the first positional argument.
+    // pub fn get_pos_opt<E: ExpressionKind>(&mut self) -> ParseResult<Option<E>> {
+    //     Ok(if !self.positional.items.is_empty() {
+    //         let spanned = self.positional.items.remove(0);
+    //         Some(E::from_expr(spanned)?)
+    //     } else {
+    //         None
+    //     })
+    // }
+
+    // /// Force-extract a keyword argument.
+    // pub fn get_key<E: ExpressionKind>(&mut self, name: &str) -> ParseResult<E> {
+    //     expect(self.get_key_opt(name))
+    // }
+
+    // /// Extract a keyword argument.
+    // pub fn get_key_opt<E: ExpressionKind>(&mut self, name: &str) -> ParseResult<Option<E>> {
+    //     self.keyword.pairs.iter()
+    //         .position(|p| p.key.v.0 == name)
+    //         .map(|index| {
+    //             let value = self.keyword.pairs.swap_remove(index).value;
+    //             E::from_expr(value)
+    //         })
+    //         .transpose()
+    // }
+
+    // /// Iterator over positional arguments.
+    // pub fn iter_pos(&mut self) -> std::vec::IntoIter<Spanned<Expression>> {
+    //     let tuple = std::mem::replace(&mut self.positional, Tuple::new());
+    //     tuple.items.into_iter()
+    // }
+
+    // /// Iterator over all keyword arguments.
+    // pub fn iter_keys(&mut self) -> std::vec::IntoIter<Pair> {
+    //     let object = std::mem::replace(&mut self.keyword, Object::new());
+    //     object.pairs.into_iter()
+    // }
+
+    // /// Clear the argument lists.
+    // pub fn clear(&mut self) {
+    //     self.positional.items.clear();
+    //     self.keyword.pairs.clear();
+    // }
+
+    // /// Whether both the positional and keyword argument lists are empty.
+    // pub fn is_empty(&self) -> bool {
+    //     self.positional.items.is_empty() && self.keyword.pairs.is_empty()
+    // }
+}
+
+// /// Extract the option expression kind from the option or return an error.
+// fn expect<E: ExpressionKind>(opt: ParseResult<Option<E>>) -> ParseResult<E> {
+//     match opt {
+//         Ok(Some(spanned)) => Ok(spanned),
+//         Ok(None) => error!("expected {}", E::NAME),
+//         Err(e) => Err(e),
+//     }
+// }