contract interface F =
    entrypoint f : () => int

payable contract interface G : F =
    payable entrypoint f : () => int
    entrypoint g : () => int

payable contract interface H =
    payable entrypoint h : () => int

payable contract C : G, H =
    payable entrypoint f() = 1
    payable entrypoint g() = 2
    payable entrypoint h() = 3
