Undefined in typedef causes type mismatches to be silently ignored

Externs:

``` javascript
/** @typedef {{ sausages: (?string) }} */
var GOOD;

/** @typedef {{ sausages: (string|null|undefined) }} */
var BAD;
```

Code:

``` javascript
/** @param {GOOD} obj */
var testGood = function(obj) {};

/** @param {BAD} obj */
var testBad = function(obj) {};

testGood({bacon: "mmm"}) // correctly fails
testBad({bacon: "yuck"}) // should fail, doesn't
```

It appears changing from `?string` to `string|null|undefined` causes the entire typedef to be disregarded silently.

https://closure-compiler-debugger.appspot.com/#input0%3D%252F**%2520%2540param%2520%257BGOOD%257D%2520obj%2520*%252F%250Avar%2520testGood%2520%253D%2520function(obj)%2520%257B%257D%253B%250A%250A%252F**%2520%2540param%2520%257BBAD%257D%2520obj%2520*%252F%250Avar%2520testBad%2520%253D%2520function(obj)%2520%257B%257D%253B%250A%250AtestGood(%257Bbacon%253A%2520%2522mmm%2522%257D)%2520%252F%252F%2520correctly%2520fails%2520%250AtestBad(%257Bbacon%253A%2520%2522yuck%2522%257D)%2520%252F%252F%2520should%2520fail%252C%2520doesn't%26input1%26conformanceConfig%26externs%3D%252F**%2520%2540typedef%2520%257B%257B%2520%2520sausages%253A%2520(%253Fstring)%2520%2520%257D%257D%2520*%252F%250Avar%2520GOOD%253B%250A%250A%252F**%2520%2540typedef%2520%257B%257B%2520%2520sausages%253A%2520(string%257Cnull%257Cundefined)%2520%257D%257D%2520*%252F%250Avar%2520BAD%253B%26refasterjs-template%26CHECK_SYMBOLS%3D1%26CHECK_TYPES%3D1%26MISSING_PROPERTIES%3D1

Background:
I'm trying to make it easy for a developer to pass a clean and simple JS object literal into a method, and have Closure Compiler verify the object literal matches all expected properties, e.g.:

``` javascript
someFunc({
propA: 5,
propB: ["a", "b"]
// propC optional and missing
});
```

Hence I need to allow for undefined. I was surprised that `?` didn't mean "null or undefined", and think the only way of doing this is using `string|null|undefined` in this example.

This issue is somewhat worrying because it is easy to inadvertently disable all typechecks. Presumably this is a bug. But if this is intended for some reason, it would benefit from some warning that could be turned off, rather than silently ignoring failures.