[ts]typescript中的类型推导

type MyReadonly2<T, K extends keyof T = keyof T> = {
  readonly [Key in K]: T[Key]
} & {
  [Key in Exclude<keyof T, K>]: T[Key]
}


/* _____________ 测试用例 _____________ */
import { Alike, Expect } from '@type-challenges/utils'

type cases = [
  Expect<Alike<MyReadonly2<Todo1>, Readonly<Todo1>>>,
  Expect<Alike<MyReadonly2<Todo1, 'title' | 'description'>, Expected>>,
  Expect<Alike<MyReadonly2<Todo2, 'title' | 'description'>, Expected>>,
]

interface Todo1 {
  title: string
  description?: string
  completed: boolean
}

interface Todo2 {
  readonly title: string
  description?: string
  completed: boolean
}

interface Expected {
  readonly title: string
  readonly description?: string
  completed: boolean
}

K extends keyof T = keyof T 中的= keyof T语句有什么作用，我对这个=的用法不太理解，在这里是可以直接用来指定K的类型吗？

这段代码是在这里看到的