function local_func() {

  var local_x = "hello";

  function local_f() { }
  function local_g() { local_x = 42; }

  local_f();
  takes_string(local_x); // ok

  local_g();
  takes_string(local_x); // error

  local_x = 42;  // shouldn't pollute linear refinement
}
Test tracking of variable types across closure calls.
@flow