Nested optional property existence check via Boolean() cause false possibly undefined error

[zfeher]

TypeScript Version: 2.0.3

Code
Nested optional property existence check via !! vs. Boolean()

// strictNullChecks: true

interface Address {
  country: string;
}

interface Student {
  address?: Address;
}

const student: Student = {
  address: {
    country: 'US',
  }
};

// this one works just fine, no error reported
const b1: boolean = student && !!student.address && student.address.country === 'US';

// this one reports an error for the second student.address: Object is possibly 'undefined' 
// whereas !!something should be the same as Boolean(something)
const b2: boolean = student && Boolean(student.address) && student.address.country === 'US';

Expected behavior:
"Object is possibly 'undefined' error" should not be reported when accessing student.address after the existence of address on student is verified.

Actual behavior:
"Object is possibly 'undefined' error" is reported when student.address is accessed the second time after its existence is already verified.

[kitsonk]

Related to/dupe of #9508 (in the sense of expanding guards that are recognised by CFA)