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

还没有人认领这个 Issue。

### 🔎 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

```ts
type MyType = U;

class MyClass {
value!: MyType;
}
```

### 🙁 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_

重现链接的 TypeScript Playground 示例中的诊断，然后跟踪对具有可选属性和 intersected keyof keys 的映射类型进行泛型约束检查的过程。当该示例能够无错误地编译，同时保留对相关情况的正确约束检查时，这项工作就完成了。

由索引模型根据 Issue 内容生成。