Impl Wrapping*
traits from num-traits
#425
Merged
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Until now we have used traits defined in this crate, primarily because many of these traits are predicates that return
bool
and in constant-time code we want those to returnChoice
/CtOption
.Wrapping*
is an example of the sort of trait we'd want to incorporate unchanged, and there are potentially others, so this addsnum-traits
as a hard dependency (previously our only hard dependency wassubtle
). Note thatnum-traits
itself has no transitive dependencies (or rather, they're optional but not enabled).The
Wrapping*
traits have bounds on the corresponding op traits being impl'd withSelf
operands e.g.WrappingAdd: Add<Self, Output = Self>
so this PR also adds impls of those traits.We've previously avoided these as in
std
they panic on overflow/underflow in debug builds and silently wrap in release builds. This PR always panics.This required some changes to the
Mul
impls which were conditional onConcatMixed
and implicitly widened. To accomodate impls which are always available and require no bounds (in order to allow us to implWideningMul
), and renames the following:Uint::mul
->Uint::widening_mul
Uint::mul_wide
->Uint::widening_mul_split
TODO:
WrappingNeg
WrappingShl
WrappingShr
cc @xuganyu96