TypeScript doesn't narrow out `undefined` after constructor call when callee is `any`

TypeScript doesn't seem to narrow the type of a variable correctly in cases where the constructor being called is typed as any. If the type of a variable includes undefined in its type signature, it's not narrowed out after a constructor call even though by definition (I think--correct me if I'm wrong) new fn() must always evaluate to an object if it doesn't throw first.

TypeScript Version: 3.1.3

Search Terms: constructor narrow

Code

let x: { [x: string]: any } | undefined;
x = new (Object as any)();
// AFAIK `x` can't possibly be undefined after this point
console.log(x.foo);  // error: Object is possibly 'undefined'.

Expected behavior:
No error.

Actual behavior:
Compile-time error: Object is possibly 'undefined'.

Playground Link:
http://www.typescriptlang.org/play/#src=let%20x%3A%20%7B%20%5Bx%3A%20string%5D%3A%20any%20%7D%20%7C%20undefined%3B%0D%0Ax%20%3D%20new%20(Object%20as%20any)()%3B%0D%0Aconsole.log(x.foo)%3B%0D%0A

Commencez par le repro dans TypeScript Playground et par l’affectation new (Object as any)() présentée dans l’issue. Suivez la manière dont le narrowing du flux de contrôle gère les appels de constructeur dont le callee est any, puis vérifiez que l’exemple ne signale plus Object is possibly 'undefined' sans modifier le comportement du narrowing non concerné.