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Description
It's becoming common in the ecosystem to add ChainRules rules for functions that use features that are problematic or slow for certain AD packages, like mutation, loops, or control flow. Maybe we should do this to, at least to add projections and such. JuliaDiff/ChainRules.jl#540 should probably be finished first.
We already have ChainRulesCore as an indirect dependency via DualNumbers and then SpecialFunctions, so this would not make this package heavier.