Remove NTuple from unbroadcast (#661)

* remove NTuple

* spaces

Co-authored-by: Frames Catherine White <[email protected]>

Co-authored-by: Frames Catherine White <[email protected]>

Author: mcabbott

Project.toml

@@ -1,6 +1,6 @@
 name = "ChainRules"
 uuid = "082447d4-558c-5d27-93f4-14fc19e9eca2"
-version = "1.44.1"
+version = "1.44.2"
 
 [deps]
 Adapt = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"

src/rulesets/Base/broadcast.jl

@@ -328,13 +328,13 @@ end
 unbroadcast(x::Base.AbstractArrayOrBroadcasted, dx::AbstractZero) = dx
 
 function unbroadcast(x::T, dx) where {T<:Tuple{Vararg{Any,N}}} where {N}
-    val = if length(x) == length(dx)
+    val = if N == length(dx)
         dx
     else
         sum(dx; dims=2:ndims(dx))
     end
     eltype(val) <: AbstractZero && return NoTangent()
-    return ProjectTo(x)(NTuple{length(x)}(val)) # Tangent
+    return ProjectTo(x)(Tuple{Vararg{Any,N}}(val)) # Tangent
 end
 unbroadcast(x::Tuple, dx::AbstractZero) = dx
 

test/rulesets/Base/broadcast.jl

@@ -173,4 +173,8 @@ BT1 = Broadcast.BroadcastStyle(Tuple)
             test_rrule(copy∘broadcasted, complex, rand())
         end
     end
+    
+    @testset "bugs" begin
+        @test ChainRules.unbroadcast((1, 2, [3]), [4, 5, [6]]) isa Tangent   # earlier, NTuple demanded same type
+    end
 end