Unexpect Object is possibly 'undefined' Error when checked before.

[SyMind]

Steps

use TS 3.3 (latest)
enable all strict checks
have code such as this:

interface Props {
    foo?: {
        bar: string;
        baz: string;
    }
}

function hello({foo}: Props) {
    const isFooPresent = foo !== undefined;
    let bar = isFooPresent ? foo.bar : ''; // Object is possibly 'undefined'.
    let baz = isFooPresent ? foo.baz : ''; // Object is possibly 'undefined'.

    // but follow code is safe.
    //  let bar = foo !== undefined ? foo.bar : '';
    //  let baz = foo !== undefined ? foo.baz : '';
}

Using a const variable to store check result, an error when occur.

[MartinJohns]

And another duplicate of #12184.

use TS 3.3 (latest)

Uhh... The latest version is 4.0.2, not 3.3.