text: //// [assignFromBooleanInterface2.ts]
  interface Boolean {
      doStuff(): string;
  }
  
  interface NotBoolean {
      doStuff(): string;
  }
  
  var x = true;
  var a: Boolean;
  var b: NotBoolean;
  
  a = x;
  a = b;
  
  b = a;
  b = x;
  
  x = a; // expected error
  x = b; // expected error
  
  
  
  //// [assignFromBooleanInterface2.js]
  var x = true;
  var a;
  var b;
  a = x;
  a = b;
  b = a;
  b = x;
  x = a; // expected error
  x = b; // expected error
  