Infer type isn't contextual typed by type bounds

Bug Report

Infer type isn't contextual typed by type bounds

type Foo<T> = T extends string ? Record<T, number> : never;

type Foo2<T extends {a:string}>= T extends {a: infer A} ?  Record<A, number>:never; //error here, A should extends string already, but seems not

🔎 Search Terms

generic infer bounds

🕗 Version & Regression Information

4.2.3

⏯ Playground Link

https://www.typescriptlang.org/play?#code/C4TwDgpgBAYg9nAPAFQHxQLxWVCAPYCAOwBMBnKM4AJwEsiBzKAfigCUIBjOaklAGihEArgFsARhGroAXEIgA3KQG4AUKtCRYCAEwpcBYuSgBvAIYyqdRgF9UWHPkKkK5ufQBmUqAEEbLKHYuHj4fQREJKVQZIkUVIA

💻 Code

type Foo<T> = T extends string ? Record<T, number> : never;

type Foo2<T extends {a:string}>= T extends {a: infer A} ?  Record<A, number>:never; //error here, A should extends string already, but seems not

🙁 Actual behavior

throw error

🙂 Expected behavior

not throw error

Inizia con il TypeScript Playground collegato e l’esempio ridotto Foo2 per riprodurre l’errore. L’issue non indica alcun file sorgente né alcun test; traccia come il compilatore gestisce i vincoli di tipo inferiti, quindi verifica che l’esempio accetti Record<A, number> come previsto e aggiungi la copertura di regressione.