Type argument with a subset of the parameter constraint's optional keys incorrectly reported as unassignable to constraint

🔎 Search Terms

"does not satisfy the constraint" "keyof" "optional"

🕗 Version & Regression Information

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

⏯ Playground Link

https://www.typescriptlang.org/play/?#code/C4TwDgpgBAsiAq4IB54BooFUoQB7AgDsATAZygG8oBtAaSgEtCoBrCEAewDMp4BdAPwAuKAFdCLQhwDuzAL4A+KAF4sAbgCwAKG0BjADYBDUuTgBhIydRKK2qFABuh-aIgBCEXESRUGKnUZmNk4eeCgAMihSYAAnJgBzQRFxSRl5BU0tOW0gA

💻 Code

type MyType<T, U extends { [K in keyof T]?: unknown }> = U;

class MyClass<T> {
  value!: MyType<T, { [K in keyof T & string]?: unknown }>;
}

🙁 Actual behavior

The following error is reported:

Type '{ [K in keyof T & string]?: unknown; }' does not satisfy the constraint '{ [K in keyof T]?: unknown; }'.
  Type 'keyof T' is not assignable to type 'keyof T & string'.
    Type 'string | number | symbol' is not assignable to type 'keyof T & string'.
      Type 'string' is not assignable to type 'keyof T & string'.
        Type 'string' is not assignable to type 'keyof T'.
          Type 'keyof T' is not assignable to type 'string'.
            Type 'string | number | symbol' is not assignable to type 'string'.
              Type 'number' is not assignable to type 'string'.

🙂 Expected behavior

No error should be reported because due to the keys being optional, { [K in keyof T & string]?: unknown } is a subtype of { [K in keyof T]?: unknown } for all T.

Additional information about the issue

No response

Tái hiện chẩn đoán từ ví dụ TypeScript Playground được liên kết, sau đó truy vết quá trình kiểm tra ràng buộc generic cho các kiểu mapped có thuộc tính tùy chọn và intersected keyof keys. Công việc hoàn tất khi ví dụ biên dịch không có lỗi mà vẫn duy trì việc kiểm tra ràng buộc chính xác cho các trường hợp liên quan.