UFCS-unittest.d

gistfile1.txt

auto foo(string[] sta) {
  return sta;
}

auto bar(string[] sta) {
  return sta;
}

auto h(string[] sta) {
  return sta.foo.bar;
}

unittest {
  import std.format;

  auto f = (string[] sta) => sta.foo.bar;
  auto g(string[] sta) {
    return sta.foo.bar;
  }

  assert(f(["test"]) == ["test"]);
  assert(g(["test"]) == ["test"]);
  assert(["test"].h() == ["test"]);
  assert(["test"].g == ["test"]);
  /* 
    The latest test raises error: Error: no property g for type string[]
  */
}

Link: https://forum.dlang.org/post/zkywlxmtrndlwefdtwoq@forum.dlang.org