Question

I have a code:

static short Sum(short a, short b)
        {
            return a + b;
        }

And it does not compile, saynig cannot convert ‘int’ to ‘short’. I am maybe really tired today but I cannot see the issue!

Answer 1

And it does not compile, saynig cannot convert ‘int’ to ‘short’. I am maybe really tired today but I cannot see the issue!

It’s just the way the language is defined. The + operator on integer types is defined for:

static uint op +(uint x, uint y)
static int op +(int x, int y)
static ulong op +(ulong x, ulong y)
static long op +(long x, long y)

Operands are promoted as required.

Now as for the reasons why it’s defined that way – I don’t know, to be honest. I don’t buy the argument of “because it could overflow” – that would suggest that byte + byte should be defined to return short, and that int + int should return long, neither of which is true.

I’ve heard somewhere that it could be performance related, but I wouldn’t like to say for sure. (Perhaps processors typically only provide integer operations on 32 and 64 bit integers?)

Either way, it doesn’t really matter why it’s the case – it’s just the rules of the language.

Note that the compound assignment operators have an implicit conversion back to the relevant type, so you can write:

short x = 10;
short y = 20;
x += y;