Suggestion: perform excess property checks when spreading an inline object literal

TypeScript Version: 3.9.2

Search Terms:

Code

declare const someCondition: boolean;

type MyObject = { foo: number; bar?: number };

const a: MyObject = {
  foo: 1,
  bar: 2,
  // ✅ Error because `invalid` is an excess property
  invalid: 3,
};

const b: MyObject = {
  foo: 1,
  ...(someCondition
    ? {
        bar: 2,
        // ❌ `invalid` is an excess property, but we don't get an error here
        invalid: 3,
      }
    : {}),
};

In the example above, I only want to include specific properties when a condition is met. That's the only reason I'm using spread here.

I understand that TypeScript only performs excess property checks inside of object literals. Currently this does not include inline object literals which are being spread inside of another object literal.

In my experience this is a very common code pattern so it would be great if TypeScript handled this.

Expected behavior:

An error

Actual behavior:

No error

Playground Link:

Related Issues:

まず、提供された TypeScript 3.9.2 の例を再現し、オブジェクトリテラルの直接代入と条件付き spread のケースを比較します。spread で使用されるインラインオブジェクトリテラルに対するコンパイラの excess-property checking を調査します。spread のケースで、示されている無効なプロパティがエラーを発生させ、かつ有効な条件付き spread を壊さなければ完了です。