Re: Why is this not a warning?

[jmh530 via Digitalmars-d]

On Wednesday, 16 March 2016 at 16:40:49 UTC, Shachar Shemesh 
wrote:

People who are marginally familiar with integer promotion will 
not be surprised to know that the program prints "256". What is 
surprising to me is that this produced neither error nor 
warning.


Here's a simpler example:

import std.stdio : writeln;

void main() {
    ulong MAX_VAL = 256;
    long value = -500;

    writeln(value > MAX_VAL); //prints true
}

Looks like integer promotion in D follows the same rules as C: 
when the types are the same size, the signed type is converted to 
the unsigned type. Definitely could cause an issue and deserves a 
warning, as you say.

It's not like you could switch the rule to being that an unsigned 
type is converted to the signed type. You would still get errors, 
just over a different range. You could instead write something 
like:

bool compare(long a, ulong b)
{
        if (b < long.sizeof)
                return a > cast(long)b;
        else
                return cast(float)a > cast(float)b;
}