A[] form works, but Array<A> breaks

Bug Report

🔎 Search Terms

site:github.com inurl:/microsoft/TypeScript/issues/ Array [] normalization syntactic sugar

🕗 Version & Regression Information

This works in 3.9.7, broke in 4.0.5, and remains broken in Nightly.

• This changed between versions 3.9.7 and 4.0.5

⏯ Playground Link

Playground link with relevant code

💻 Code

type R<C> = [C, ...R<C>[]] | number;      // works, as expected
type S<C> = [C, ...Array<S<C>>] | number; // fails unexpectedly - should work identically

const r: R<"add"> = ["add", 2, 1];
const s: S<"add"> = ["add", 2, 1];

🙁 Actual behavior

The A[] form in the first line works, but the otherwise-identical Array<…> form on the second line breaks with the warning Type alias 'S' circularly references itself.(2456).

🙂 Expected behavior

Both of these should work, and behave identically, as they are merely syntactic sugar for each other.

Commencez par les exemples de Playground liés et les alias de type minimaux R et S, en comparant le comportement entre TypeScript 3.9.7, 4.0.5 et Nightly. Suivez la vérification des alias de type circulaires et leur traitement de Array par rapport à T[] ; c'est terminé lorsque les deux alias récursifs équivalents se compilent sans le diagnostic de référence circulaire.