type consistency with boolean comparisons

[A60AB5450353F40E]

bool b, bool a;

a == b should compile to OP_NUMEQUAL (rather than OP_EQUAL) a != b should compile to OP_NUMNOTEQUAL (rather than OP_EQUAL OP_NOT)

[mr-zwets]

thanks for opening this issue!

In the first case I don't see why it would matter to use OP_NUMEQUAL rather than OP_EQUAL (they are functionally the same in this case so what is the benefit of making the breaking change?)

the second case would indeed save one opcode 👍 I quickly confirmed the compiler behavior on the playground

Making breaking changes to the compiler is only something we want to do very infrequently

[mr-zwets]

I stand corrected that both are functionally the same

OP_NUMEQUAL matters for cases like positive and negative zero, which are equal numerically but not when doing OP_EQUAL I think the only way to get to negative zero is to use int(0x80) which could happen I guess

[mr-zwets]

require(bool(int(0x80)) == false);

compiles to OP_0 OP_EQUALVERIFY which would return false

so

int negativeZero = int(0x80);
bool falsyBool = bool(negativeZero);
require(falsyBool == false); // this will fail because of OP_EQUALVERIFY instead of OP_NUMEQUAL 

edit: this can also be done with bool's directly

contract Example() {
    function transfer(bool test) {
        if(test == false){
            require(tx.outputs.length == 2);
        } else {
            require(tx.outputs.length == 1); // negative zero would end up in this case
        }
    }
}

[rkalis]

Let's get back to this after we've resolved type casting quirks.