var undef_tests =
[
  // NOTE: not (yet?) supporting non-strict eq test for undefined

  // expr !== undefined
  function() {
    var x : ?string = "xxx";
    if (x !== undefined && x !== null) {
      var y : string = x;  // ok
    }
  },

  function() {
    var x : ?string = "xxx";
    if (undefined !== x && x !== null) {
      var y : string = x;  // ok
    }
  },

  function() {
    var x : {p:?string} = {p:"xxx"};
    if (x.p !== undefined && x.p !== null) {
      var y : string = x.p;  // ok
    }
  },

  function() {
    var x : {p:{q:?string}} = {p:{q:"xxx"}};
    if (x.p.q !== undefined && x.p.q !== null) {
      var y : string = x.p.q;  // ok
    }
  },

  // expr === undefined
  function() {
    var x : ?string = "xxx";
    if (x === undefined || x === null) {} else {
      var y : string = x;  // ok
    }
  },

  function() {
    var x : {p:?string} = {p:"xxx"};
    if (x.p === undefined || x.p === null) {} else {
      var y : string = x.p;  // ok
    }
  },

  function() {
    var x : {p:{q:?string}} = {p:{q:"xxx"}};
    if (x.p.q === undefined || x.p.q === null) {} else {
      var y : string = x.p.q;  // ok
    }
  },
];

// this.p op undefined
class A {
  p: ?string;

  ensure0(): string {
    if (this.p !== undefined && this.p !== null)
      return this.p;
    else
      return "";
  }

  ensure1(): string {
    if (this.p === undefined || this.p === null)
      return "";
    else
      return this.p;
  }
}