==================
Top-level fields
==================
host = String;
port = Int & > 443 default 8080;
---

(source_file
  (field_definition
    path: (field_path (identifier))
    value: (identifier))
  (field_definition
    path: (field_path (identifier))
    value: (default_expression
      base: (binary_expression
        left: (identifier)
        right: (comparison_constraint
          value: (integer)))
      fallback: (literal (integer)))))

==================
Import and function
==================
let
  schema = import "./schema.dcdl";
  mk = (cfg: schema.Service) => cfg;
in
  mk({ name = "api"; })
---

(source_file
  (let_expression
    (field_definition
      path: (field_path (identifier))
      value: (import_expression
        specifier: (string)))
    (field_definition
      path: (field_path (identifier))
      value: (function_expression
        (parameter
          name: (identifier)
          constraint: (path_expression
            object: (identifier)
            field: (identifier)))
        body: (identifier)))
    body: (call_expression
      function: (identifier)
      (object
        (field_definition
          path: (field_path (identifier))
          value: (literal (string)))))))

==================
Match and patch
==================
base // {
  summary = match env {
    "prod": "production";
    _: "other";
  };
}
---

(source_file
  (binary_expression
    left: (identifier)
    right: (object
      (field_definition
        path: (field_path (identifier))
        value: (match_expression
          scrutinee: (identifier)
          (match_arm
            pattern: (literal (string))
            body: (literal (string)))
          (match_arm
            body: (literal (string))))))))