October commit

- custom parser support and infra
- type-tagging and traits (untested)
- match expressions

examples/file-browser/main.orc

@@ -5,7 +5,7 @@ const folder_view := (path, next) => do{
   cps println $ "Contents of " ++ fs::os_print path;
   cps entries = async::block_on $ fs::read_dir path;
   cps list::enumerate entries
-    |> list::map (pass \id. pass \name. \is_dir.
+    |> list::map ((t[id, t[name, is_dir]]) =>
       println $ to_string id ++ ": " ++ fs::os_print name ++ if is_dir then "/" else ""
     )
     |> list::chain;
@@ -17,7 +17,7 @@ const folder_view := (path, next) => do{
       |> tuple::pick 0 2;
     next parent_path
   } else do {
-    cps subname, is_dir = to_uint choice
+    let t[subname, is_dir] = to_uint choice
       |> (list::get entries)
       |> option::unwrap;
     let subpath = fs::join_paths path subname;