structNullChecks doesn't detect undefined members of a class

[e98cuenc]

TypeScript Version: 2.0.0

Code

    class FooBar {
        bar: string;

        foo() {
            console.log(this.bar.length); // at runtime: Cannot read property 'length' of undefined
        }
    }

    new FooBar().foo();

Expected behavior:

tsc should fail because bar can be undefined after the construction of FooBar.

Actual behavior:

tsc compiles and you get an error at runtime.

[yortus]

Duplicate of #8476