Unsafe cast should fail

The following should fail:

```js
/** @interface */
class X {
y() {}
}

const x = /** @type {!X} */ ({});
x.y()
```

But it is happy to let this invalid cast through.

https://closure-compiler.appspot.com/home#code%3D%252F%252F%2520%253D%253DClosureCompiler%253D%253D%250A%252F%252F%2520%2540compilation_level%2520ADVANCED_OPTIMIZATIONS%250A%252F%252F%2520%2540output_file_name%2520default.js%250A%252F%252F%2520%2540formatting%2520pretty_print%250A%252F%252F%2520%253D%253D%252FClosureCompiler%253D%253D%250A%250A%250A%252F**%2520%2540interface%2520*%252F%250Aclass%2520X%2520%257B%250A%2520%2520y()%2520%257B%257D%250A%257D%250A%250Aconst%2520x%2520%253D%2520%252F**%2520%2540type%2520%257B!X%257D%2520*%252F%2520(%257B%257D)%253B%250Ax.y()%250A