Can a payable function be internal?

Question

I have the following setup of two internal and external functions. Is such a setup correct?

address public addr;

function addValue() external payable {
   _addValue(msg.value);
}

function _addValue(uint256 value) internal payable {
   addr.send(value);
}

Answer 1

No internal and private function can't be declared as payable

you will get a compiler error

TypeError: "internal" and "private" functions cannot be payable

The idea of having payable modifier is "to permission or prevent intentional and accidental value transfers" and using it twice first in external/public function and then again in internal function which is called by that function does not make sense :)

but you can use msg.value inside the internal function so something like this

    function addValue() external payable {
       _addValue();
    }
    
    function _addValue() internal {
       payable(addr).transfer(msg.value);
    }