Argument of type 'number' | 'string' is not assignable to overloaded function accepting 'number' or 'string

[osi-oswald]

TypeScript Version:

1.8.10

Code

declare function overload(param: number);
declare function overload(param: string);

let bar: number | string;
overload(bar); // Argument of type 'number' | 'string' is not assignable to parameter of type 'string'

Expected behavior:
Since the function 'overload' either accepts a 'number' or a 'string', the compiler should not complain.

Actual behavior:
The compiler complains with: "Argument of type 'number' | 'string' is not assignable to parameter of type 'string'".

Workaround:
Of course I could always rewrite the declaration of 'overload' as:

declare function overload(param: number | string);

But usually these declarations are from external *.d.ts files which I do not want to touch if I don't have to.

[yortus]

Looks like a duplicate of #1805

[osi-oswald]

You are absolutely right regarding the duplicate