I think this came up in a different PR or discussion somewhere, but this makes it so that decimal-integer addition works 'properly' now if the decimal precision wasn't big enough to hold the integer (now it will promote both to a larger decimal type).

Is Decimal not part of Numeric? I don't see any reason to call it out special here given that we don't do so for add/multiply/divide/subtract.

Although, to be fair, we don't currently support decimal for the rest of the math operations (trig, pow/ln, etc.) and that's more than just a casting issue so it may be sometime before we do offer support. So we might want to call out that fact.

Either way, I think we should keep this page consistent. Either decimal is part of "Numeric" everywhere or nowhere.

Fair, "Numeric" is defined up top as often including decimal. The blurb about promotion here should suffice, I think; I also added a blurb about decimal promotion to the arithmetic section.