Typescript's type inference, why can't the type of data be inferred?

Question

According to what I thought, data can infer the type of {list: string[] } and then use data.list , but it doesn't seem to work, and it will give an error when using it. Is there something wrong with where my code is written?

full code

const get = <T, C>(url: string, clearFn: (data: T) => C): Promise<C | null> =>
  new Promise((resolve) => {
    axios
      .get(url)
      .then((result) => {
        resolve(clearFn(result.data.data))
      })
      .catch(() => {
        resolve(null)
      })
  })

function getQuestionList<T = { list: string[] }, C = { list: number[] }>(): Promise<C | null> {
  return get<T, C>('acb/abc', (data): any => {
    console.log(data.list)
    return { list: [1, 2] }
  })
}

Answer 1

You are defining the default value of your generics not what it extends !

T = { list: string[] } becomes T extends { list: string[] }.

Full function :

function getQuestionList<T extends { list: string[] }, C extends { list: number[] }>(): Promise<C | null> {
  return get<T, C>('acb/abc', (data): any => {
    console.log(data.list)
    return { list: [1, 2] }
  })
}