I like to use 128 bit numbers, I’ve already used them some times with the Nightly. But they increase the complexity of the compiler, and there are many reasons for keeping a compiler as simple as possible.
So, is it a good idea to remove the 128 bit numbers from Rustc, and add to the language the features needed to allow library-level code to implement 128 bit numbers as good and as efficient as the built-in ones?
To do this I guess you need better ways to specify error messages, empty compiler-blessed traits to specify your U128 + operation to be commutative, perhaps more operator overloading, etc. This stuff hopefully adds less complexity to the compiler compared to adding i128/u128 support, and allows other people to write other kind of efficient number-like things in library code.