Generics typescript, why does this code throw an error Type ‘{}’ cannot be assigned to a type?

I can’t figure out why this code is throwing an error. – Type ‘{}’ is not assignable to type ‘Keys<T>’.

type Keys<T extends string|symbol>={
    [key in T]: string;
};
const foo = <T extends string|symbol>()=>{
    const a:Keys<T> = {}
    return a
}

Moreover, if you manually substitute the string or symbol type, no errors will be received. Just a warning that T is declared for a function but not used.

Example of working codes:

type Keys<T extends string|symbol>={
    [key in T]: string;
};
const foo = <T extends string|symbol>()=>{
    const a:Keys<string> = {}
    return a
}

type Keys<T extends string|symbol>={
    [key in T]: string;
};
const foo = <T extends string|symbol>()=>{
    const a:Keys<symbol> = {}
    return a
}

You can check the code here

I expected generic code to work fine