@non_differentiable _denom (#687)

* non_differentiable _denom

* Update Project.toml

* ∇getindex(::AbstractZero) paths

* non_differentiable foreach(f, ())

* also fix summary

Project.toml

@@ -1,6 +1,6 @@
 name = "ChainRules"
 uuid = "082447d4-558c-5d27-93f4-14fc19e9eca2"
-version = "1.46.0"
+version = "1.46.1"
 
 [deps]
 Adapt = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"

src/rulesets/Base/indexing.jl

@@ -61,10 +61,9 @@ function frule((_, ẋ), ::typeof(getindex), x::AbstractArray, inds...)
 end
 
 function rrule(::typeof(getindex), x::AbstractArray, inds...)
-    function getindex_pullback(dy)
-        nots = map(Returns(NoTangent()), inds)
-        return (NoTangent(), thunked_∇getindex(x, dy, inds...), nots...)
-    end
+    nots = map(Returns(NoTangent()), inds)
+    getindex_pullback(dy) = (NoTangent(), thunked_∇getindex(x, dy, inds...), nots...)
+    getindex_pullback(z::AbstractZero) = (NoTangent(), z, nots...)
     return x[inds...], getindex_pullback
 end
 
@@ -90,6 +89,7 @@ function ∇getindex(x::AbstractArray, dy, inds...)
     ∇getindex!(dx, dy, plain_inds...)
     return ProjectTo(x)(dx)  # since we have x, may as well do this inside, not in rules
 end
+∇getindex(x::AbstractArray, z::AbstractZero, inds...) = z
 
 """
     _setindex_zero(x, dy, inds...)
@@ -191,10 +191,9 @@ function frule((_, ẋ), ::typeof(view), x::AbstractArray, inds...)
 end
 
 function rrule(::typeof(view), x::AbstractArray, inds...)
-    function view_pullback(dy)
-        nots = map(Returns(NoTangent()), inds)
-        return (NoTangent(), thunked_∇getindex(x, dy, inds...), nots...)
-    end
+    nots = map(Returns(NoTangent()), inds)
+    view_pullback(dy) = (NoTangent(), thunked_∇getindex(x, dy, inds...), nots...)
+    view_pullback(z::AbstractZero) = (NoTangent(), z, nots...)
     return view(x, inds...), view_pullback
 end
 

src/rulesets/Base/nondiff.jl

@@ -189,6 +189,7 @@
 @non_differentiable floatmax(::Any)
 @non_differentiable floatmin(::Any)
 @non_differentiable flush(::Any)
+@non_differentiable foreach(::Any, ::Tuple{})
 
 @non_differentiable gensym(::Symbol)
 @non_differentiable gensym(::String...)
@@ -422,6 +423,7 @@ end
 @non_differentiable supertype(::Any)
 @non_differentiable Symbol(::Any...)
 @non_differentiable symlink(::AbstractString, ::AbstractString)
+@non_differentiable summary(::Any)
 
 @non_differentiable take!(::Base.GenericIOBuffer)
 @non_differentiable take!(::IOStream)
@@ -472,6 +474,7 @@ elseif isdefined(Base, :cumulative_compile_time_ns)
 end
 @non_differentiable Base.time_print(::Any...)
 @non_differentiable Base.OneTo(::Any...)
+@non_differentiable Base.array_summary(::Any)
 
 @non_differentiable Broadcast.combine_styles(::Any...)
 @non_differentiable Broadcast.result_style(::Any)

src/rulesets/Statistics/statistics.jl

@@ -6,6 +6,8 @@ _denom(x, dims) = size(x, dims)
 _denom(x, dims::Colon) = length(x)
 _denom(x, dims::Union{Tuple, AbstractArray}) = mapreduce(i->size(x, i), Base.mul_prod, unique(dims), init=1)
 
+@non_differentiable _denom(::Any, ::Any)  # else Zygote tries to AD unique(::Tuple)
+
 function rrule(::typeof(mean), x::AbstractArray{<:Union{Real,Complex,AbstractArray}}; dims=:)
     y_sum, sum_pullback = rrule(sum, x; dims)
     n = _denom(x, dims)