> For example, if Int8 = -10 and UInt16 = 5, and I’m expecting an answer of -5, then I’ll need to be more explicit to get the number I’m looking for. If I’m expecting [65531], then the implicit promotion works fine.
That depends on what you're hoping to do with the number you're looking for. If you wanted -5 as an Int16, the bit pattern would be 1111 1111 1111 1011 or 0xFFFB.
If you wanted 65531 as a UInt16, the bit pattern for that is 1111 1111 1111 1011 or 0xFFFB. You're getting the same result either way. And any values you compute from that result [that is, by arithmetic] are going to be unaffected by whether you labeled the result "Int16" or "UInt16", because that's just a label. If you labeled 0xFFFB a "Snerf", the arithmetic would still be the same.
There are only a very restricted set of places where you need to be explicit about whether you think of your variable as an Int or a UInt:
1. When you're widening it.
2. When you're doing a right shift.
3. When you're formatting it for display to a human.
That depends on what you're hoping to do with the number you're looking for. If you wanted -5 as an Int16, the bit pattern would be 1111 1111 1111 1011 or 0xFFFB.
If you wanted 65531 as a UInt16, the bit pattern for that is 1111 1111 1111 1011 or 0xFFFB. You're getting the same result either way. And any values you compute from that result [that is, by arithmetic] are going to be unaffected by whether you labeled the result "Int16" or "UInt16", because that's just a label. If you labeled 0xFFFB a "Snerf", the arithmetic would still be the same.
There are only a very restricted set of places where you need to be explicit about whether you think of your variable as an Int or a UInt:
1. When you're widening it.
2. When you're doing a right shift.
3. When you're formatting it for display to a human.