Error is not showing on comparing when interface has optional variables

[andropov-sergej]

Code

interface A {
    id?: number;
}
const a:A = {
    id: 5
};
const testA: boolean = (a === 1); //works, but why?


interface B {
    id: number;
}
const b:B = {
    id: 5
};
const testB: boolean = (b === 1); //compiler error -> expected that also on A

Expected behavior:
An error on the compare line.

Actual behavior:
No error

Playground Link:
https://www.typescriptlang.org/play/?ssl=1&ssc=1&pln=18&pc=1#code/JYOwLgpgTgZghgYwgAgILIN4Chm+cAEwH4AuZEAVwFsAjaAbiwF8sEB7EAZzGThPQC8mHHkJkArM0bsuPSN1RkabNgBsIcEMiEAKONoFCAjAEp6yAPQWA7mygBrTgBpkNCj2sALAJ5Es-0EhYRBQAIWE8fAIySloGZlYOblcScKFsSLFkSSZpJLkIblClFXVNbWQdGgNjM0sLdioAB2B1KGRoKDtkAFoAPg6ADyaIBEgCZDBPOB44VU42ZA40fyA

Related Issues:

[jcalz]

Context: relevant SO question

Search terms: weak type detection, comparison operators

Related issues:
#16047 - weak type detection PR
#17215 - comparability spec PR that I think never made it anywhere.

Looks like this behavior is intentional, at least if I can take #17215 for its word:

whether a type is considered weak has no bearing on whether two types are comparable,

[typescript-bot]

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