C extends A but C does not extend A | B

🔎 Search Terms

union extends

🕗 Version & Regression Information

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

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.5.2#code/C4TwDgpgBAglC8UDeUCGAuKBGANFARpgM7ABOAlgHYDmAvlAD7JqYBMUehUJFNtA3AFgAUKEhQAQgmYYorPAGNiZKtSgCRY6AGFpKWVkZzOy3mo3DN4aAHUA9qQDWRADwAVKBAAewCJQAmRLDS2gB80m5CotZQACJ2EEQAcnbA9k7unj5+gcFMUohhEfxAA

💻 Code

type A = { a: 1, b: string} | { a: 2 , b: string};
type B = { a: 2, c: string };
type C = { a: 1 | 2, b: string };

type Works<T extends A = C> = T;
type DoesNotWork<T extends A | B = C> = T;

🙁 Actual behavior

An error tells that C does not extend A | B

🙂 Expected behavior

No error since C extends A and therefore extends A | B

Additional information about the issue

No response