Commit 2025-06-07 00:12 71d36ec4
View on Github →fix: restore the NonUnitalCommRing (Fin n) instance (#25531)
#synth NonUnitalCommRing (Fin n) was made to fail uncecessarily in #25476;
it doesn't imply NatCast so is not relevant to the goal of that PR.
Also restores the CommMonoid and HasDistribNeg and NeZero 1 instances.