If I have:

const keys = ['a', 'b', 'c'] 
const obj = {} 
for (const key of keys) {
  obj[key] = key
} 

Then the error is:

Element implicitly has an 'any' type because expression of type '"a" | "b" | "c"' can't be used to index type '{}'.
  Property 'a' does not exist on type '{}'

If I add type to it:

const keys = ['a', 'b', 'c'] as const 
type Key = typeof keys[number] 
type Obj = Record<Key, Key>
const obj: Obj = {} 
for (const key of keys) {
  obj[key] = key
} 

Then the error is:

Type '{}' is missing the following properties from type 'Obj': a, b, c

I can assert the type with

const obj: Obj = {} as Obj

But for the sake of learning, is there a way to tell TS that the final object will have type Obj without having to use type assertion?

TS Playground