Ast expression macro

parser/src/lib.rs

@@ -26,3 +26,51 @@ pub fn parse<'a>(source: &'a str) -> Result<Vec<TopLevel>, ParseError<'a, Vec<To
 
     Ok(statements)
 }
+
+#[macro_export]
+macro_rules! ast_expr {
+    ($inner:tt@$item:path { $($name:ident $t:tt $val:tt $($val2:tt)?),*}) => {{
+        $(
+            let $name = $crate::_ast_t!($t $crate::_ast_ti!($inner, $val $($val2)?));
+        )*
+
+        $item { $($name,)* }
+    }};
+}
+
+#[macro_export]
+macro_rules! _ast_t {
+    (: $val:expr) => {
+        $val.get()?
+    };
+
+    (? $val:expr) => {
+        $val.or_else(|e| {
+            if let Some(recovered) = e.recovered {
+                Ok(recovered)
+            } else {
+                Err(e)
+            }
+        })
+        .get()?
+    };
+}
+
+#[macro_export]
+macro_rules! _ast_ti {
+    ($inner:ident, ! $val:ident) => {
+        $val::try_from(&mut $inner)
+    };
+
+    ($inner:ident, @ $val:ident) => {
+        $val::try_from($inner.next().unwrap())
+    };
+
+    ($inner:ident, ? ($rule:path)) => {
+        $crate::parser::listen_rule(&mut $inner, $rule)
+    };
+
+    ($inner:ident, & $val:expr) => {
+        $val
+    };
+}