==================
Immediately-invoked block closure (IIFE) is a function_expression callee
==================

void main() {
  var x = (){ return 1; }();
}

---

(program
  (function_declaration
    (function_signature
      (void_type)
      (identifier)
      (formal_parameter_list))
    (function_body
      (block
        (local_variable_declaration
          (initialized_variable_definition
            (inferred_type)
            (identifier)
            (function_expression
              (formal_parameter_list)
              (function_expression_body
                (block
                  (return_statement
                    (decimal_integer_literal)))))
            (selector
              (argument_part
                (arguments)))))))))
