Type is not checked when using object spread and computed property of type `number`

Bug Report

🔎 Search Terms

spread computed property number reduce

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about _________

⏯ Playground Link

Playground link with relevant code

💻 Code

declare const id: number;

type Acc = { [key: string]: number };
declare const acc: Acc;

// Expected error, but got none. ❌
const acc2: Acc = {
    ...acc,
    [id]: 'invalid',
};

If we change the type of the computed property id from number to string, it works as expected (we get an error).

declare const id: string;

type Acc = { [key: string]: number };
declare const acc: Acc;

// Expected error, and got none. ✅
const acc2: Acc = {
    ...acc,
    [id]: 'invalid',
};

Alternatively, if we remove the spread of acc it works as expected:

declare const id: number;

type Acc = { [key: string]: number };
// declare const acc: Acc;

// Expected error, and got none. ✅
const acc2: Acc = {
    [id]: 'invalid',
};

My workaround for now is to convert the type before it's used as a computed property:

declare const id: number;

type Acc = { [key: string]: number };
declare const acc: Acc;

// Expected error, and got none. ✅
const acc2: Acc = {
    ...acc,
    [id.toString()]: 'invalid',
};

🙁 Actual behavior

See code comments above.

🙂 Expected behavior

See code comments above.

Inizia con la riproduzione collegata in TypeScript Playground e confronta i casi usando una proprietà calcolata numerica rispetto a una di tipo string, con e senza l’object spread. Traccia il comportamento del type-checking per il literal dell’oggetto e verifica che il caso della proprietà numerica segnali un errore, mentre gli altri esempi mantengano il comportamento previsto.