Opt out the problematic StatsBase-like weighted mean(::AbstractVector, ::AbstractVector)

Author: oxinabox

src/rulesets/Statistics/statistics.jl

@@ -31,6 +31,18 @@ function rrule(
     return y_sum / n, mean_pullback_f
 end
 
+# Similar to https://github.com/JuliaDiff/ChainRules.jl/issues/522
+# The rule above assumes `f` is callable. Arrays are not, this came up when taking 
+# the mean arrays with weights in StatsBase
+@opt_out ChainRulesCore.rrule(
+    config::RuleConfig{>:HasReverseMode},
+    ::typeof(mean),
+    x::AbstractArray,
+    wt::AbstractArray{<:Union{Real,Complex,AbstractArray}};
+    dims=:
+)
+
+
 #####
 ##### variance
 #####

test/rulesets/Statistics/statistics.jl

@@ -28,6 +28,13 @@
         test_rrule(mean, abs, [-2.0 4.0; 5.0 1.9]; fkwargs=(;dims=2))
         test_rrule(mean, sqrt, rand(ComplexF64, 3, 4); fkwargs=(;dims=(1,)))
     end
+
+    @testset "Regression Test against StatsBase-like Weighted Mean" begin
+        @eval struct DummyWeights <: AbstractVector{Float64}  # DummyType that looks like StatsBase's Weights types
+        end
+        # This should return nothing as we have no rule for this. (we opted opt)
+        @test nothing == rrule(ChainRulesTestUtils.TestConfig(), mean, [1.0, 2.0], DummyWeights())
+    end
 end
 
 @testset "variation: $var" for var in (std, var)