objects with all optional properties should not be able to contain other properties

[kevinbarabash]

interface Options {
   foo?: boolean;
   bar?: boolean;
}

var options: Options;
options = { foobar: true };  // should raise a compiler error but doesn't

As soon as one of the options is not optional then we get the expected behaviour.

interface Options {
   foo: boolean;
   bar?: boolean;
}

var options: Options;
options = { foobar: true };  // raises a compiler error

[RyanCavanaugh]

See #391

[kevinbarabash]

thanks