Object literals in an assignment pattern do not get completions

[DanielRosenwasser]

As mentioned by @JsonFreeman in #3698 (comment), completion at the cursor in the following example should list a and b (and I believe with no builder allowed).

let x, y;
let z = { a: 10, b: "20" };
let k = (100, { /**/ } = z, 300);

[DanielRosenwasser]

Thanks @a-tarasyuk!