OT (partially): about promotion of integers

[Michael]

Machine/hardware have a explicitly defined register size and does 
know nothing about sign and data type. fastest operation is 
unsigned and fits to register size.

For example in your case, some algorithm that coded with 
chained-if-checks may come unusable because it will slow.

And about C# checked: 
http://msdn.microsoft.com/ru-ru/library/74b4xzyw.aspx
By default it is only for constants. For expressions in runtime 
it must be explicitly enabled.

I think this check must be handled by developer through library 
or compiler.