reshape(::AbstractZero) (#490)

* reshape Zero

* tweak

Author: mcabbott

Project.toml

@@ -1,6 +1,6 @@
 name = "ChainRulesCore"
 uuid = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
-version = "1.7.3"
+version = "1.8.0"
 
 [deps]
 Compat = "34da2185-b29b-5c13-b0c7-acf172513d20"

src/tangent_types/abstract_zero.jl

@@ -34,6 +34,7 @@ Base.getindex(z::AbstractZero, k) = z
 
 Base.view(z::AbstractZero, ind...) = z
 Base.sum(z::AbstractZero; dims=:) = z
+Base.reshape(z::AbstractZero, size...) = z
 
 """
     ZeroTangent() <: AbstractZero

test/tangent_types/abstract_zero.jl

@@ -10,6 +10,9 @@
 
         @test sum(ZeroTangent()) == ZeroTangent()
         @test sum(NoTangent(); dims=2) == NoTangent()
+
+        @test reshape(NoTangent(), (1, :)) === NoTangent()
+        @test reshape(ZeroTangent(), 2, 3, 4, 5) === ZeroTangent()
     end
 
     @testset "ZeroTangent" begin