I don't understand. It sounds like you're describing the existing behavior for the existing types. But I'm asking for new types with new behavior. The rules

I don't understand. It sounds like you're describing the existing behavior for the existing types. But I'm asking for new types with new behavior. The rules could be defined behavior for these types, which is what I want. I don't want types that happen-to-trap-because-it's-UB. I want a type that traps because that's its mission. And another type that saturates. I understand the existing undefined behavior, that's not particularly interesting. What would be interesting is well-defined behavior for new types that does not interfere with however defined or undefined behavior exists for the existing types. > usually do not have separate opcodes for overflowing arithmetic operations and trapping arithmetic operations. I don't care how good or bad the codegen is. Just emit the code for the right behavior, because I'm using this type that requires this behavior.