Interface overriding

Question

I have two contracts. One of them inherits another. Inside the parent contract I have the interface

interface Token {
    function transfer(address to, uint256 value) external returns (bool);
}

I want to override one inside the child contract to

interface Token {
    function transfer(address to, uint256 value) external returns (bool);
    function balanceOf(address who) external view returns (uint256);
}

But compiler shows DeclarationError: Identifier already declared.

Is there a way to override an interface?

Answer 1

Any interface can be, by definition, overridden by any real function having that same ABI, but it is not permitted to have N interfaces identical for some member (which precendece in override is not easy defined by inheritance graph!)

In other word if you want to have one interface for the first function, it is not needed to repeat that function identical in a new interface: just collect the other functions required and leave the first interface as is.