Merge pull request #424 from mcabbott/projectbugs

Fix two bugs in `ProjectTo`

Author: mcabbott

Project.toml

@@ -1,6 +1,6 @@
 name = "ChainRulesCore"
 uuid = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
-version = "1.1.0"
+version = "1.2.0"
 
 [deps]
 Compat = "34da2185-b29b-5c13-b0c7-acf172513d20"

src/projection.jl

@@ -179,7 +179,7 @@ end
 
 # For arrays of numbers, just store one projector:
 function ProjectTo(x::AbstractArray{T}) where {T<:Number}
-    element = ProjectTo(zero(T))
+    element = T <: Irrational ? ProjectTo{Real}() : ProjectTo(zero(T))
     if element isa ProjectTo{<:AbstractZero}
         return ProjectTo{NoTangent}() # short-circuit if all elements project to zero
     else
@@ -222,6 +222,9 @@ function (project::ProjectTo{AbstractArray})(dx::AbstractArray{S,M}) where {S,M}
     return dz
 end
 
+# Trivial case, this won't collapse Any[NoTangent(), NoTangent()] but that's OK.
+(project::ProjectTo{AbstractArray})(dx::AbstractArray{<:AbstractZero}) = NoTangent()
+
 # Row vectors aren't acceptable as gradients for 1-row matrices:
 function (project::ProjectTo{AbstractArray})(dx::LinearAlgebra.AdjOrTransAbsVec)
     return project(reshape(vec(dx), 1, :))

test/projection.jl

@@ -69,6 +69,10 @@ Base.zero(x::Dual) = Dual(zero(x.value), zero(x.partial))
         @test prow(transpose([1, 2, 3 + 4.0im])) isa Matrix  # row vectors may not pass through 
         @test prow(adjoint([1, 2, 3 + 5im])) == [1 2 3 - 5im]
         @test prow(adjoint([1, 2, 3])) isa Matrix
+
+        # some bugs
+        @test pvec3(fill(NoTangent(), 3)) === NoTangent()  #410, was an array of such
+        @test ProjectTo([pi])([1]) isa Vector{Int}  #423, was Irrational -> Bool -> NoTangent
     end
 
     @testset "Base: arrays of arrays, etc" begin
@@ -160,6 +164,9 @@ Base.zero(x::Dual) = Dual(zero(x.value), zero(x.partial))
             @test pvecmat(collect.(zs)) == zs
             @test pvecmat(collect.(zs)) isa LinearAlgebra.AdjOrTransAbsVec
         end
+
+        # issue #410
+        @test padj([NoTangent() NoTangent() NoTangent()]) === NoTangent()
     end
 
     @testset "LinearAlgebra: dense structured matrices" begin