fix two bugs

Author: mcabbott

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
@@ -199,7 +199,11 @@ function ProjectTo(xs::AbstractArray)
 end
 
 function (project::ProjectTo{AbstractArray})(dx::AbstractArray{S,M}) where {S,M}
-    # First deal with shape. The rule is that we reshape to add or remove trivial dimensions
+    # Trivial case:
+    if all(el -> el isa AbstractZero, dx)
+        return NoTangent()
+    end
+    # Now deal with shape. The rule is that we reshape to add or remove trivial dimensions
     # like dx = ones(4,1), where x = ones(4), but throw an error on dx = ones(1,4) etc.
     dy = if axes(dx) == project.axes
         dx

test/projection.jl

@@ -69,6 +69,11 @@ 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 pvec3(Any[NoTangent(), NoTangent(), NoTangent()]) === NoTangent()
+        @test ProjectTo([pi])([1]) isa Vector{Int} #423, was Irrational -> Bool -> NoTangent
     end
 
     @testset "Base: arrays of arrays, etc" begin