Infer return type from function parameter's type, based on https://dev.to/aexol/typescript-tutorial-infer-keyword-2cn This is far from satisfaction.

return.ts

let a ={
  b: {
    c:1
  }
}

type A = typeof a


type F<T> = (x:T) => (T extends ((x:any)=> infer R) ? R: never)
let f = (select) => {
  let result = select(a)

  return result
}

let b = f((x:A) => {
  return x.b
})


let f1=  (x:A) => {
  return x.b.c;
 }

type F1 = typeof f1;

let c = (f as F<F1>)(f1);