定义返回类型与其第一个参数相同的函数的正确方法是什么

Question

What I want is simple, I want a function return a type the same as its parameter. I've tried the below code but it's wrong.

type IF = <T>(name: T) => T

let f: IF = (name: string) => {
    return name + ''
}

However, below code works but it's not my wanted

type IF = <T>(name: T) => T

let f: IF = (name) => {
    return name
}

Answer 1

Looks like you've misplaced <T> The code below works

type IF<T> = (name: T) => T

let f: IF<string> = (name: string) => {
    return name + ''
}