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python_newbie98
·
Error TS2322: "could be instantiated with a different subtype of constraint 'object'" — how to fix?
Hi! I'm new to TypeScript and encountered a strange error when using generics.
I have a simple function that should take an object and return its keys. I want the function to work with any object, but preserve the return type as an array of keys of that specific object.
Here's my code:
```typescript
function getKeys(obj: T): (keyof T)[] {
return Object.keys(obj) as (keyof T)[];
}
function processObject(data: T) {
// Here I want to pass data to another function
const handler = (input: U): void => {
const keys = getKeys(input);
console.log(keys);
};
handler(data); // ERROR here!
}
```
TypeScript gives an error:
`Argument of type 'T' is not assignable to parameter of type 'U'.
'U' could be instantiated with a different subtype of constraint 'object'.`
I don't understand why this happens. Both T and U are constrained to type `object`. Why does TypeScript
