fix 1.0 ambiguity and Int32 error

Author: mcabbott

src/projection.jl

@@ -265,7 +265,7 @@ function ProjectTo(x::Ref)
         return ProjectTo{Ref}(; type=typeof(x), x=sub)
     end
 end
-(project::ProjectTo{Ref})(dx::Tangent) = Tangent{project.type}(; x=project.x(dx.x))
+(project::ProjectTo{Ref})(dx::Tangent{<:Ref}) = Tangent{project.type}(; x=project.x(dx.x))
 (project::ProjectTo{Ref})(dx::Ref) = Tangent{project.type}(; x=project.x(dx[]))
 # Since this works like a zero-array in broadcasting, it should also accept a number:
 (project::ProjectTo{Ref})(dx::Number) = Tangent{project.type}(; x=project.x(dx))

test/differentials/abstract_zero.jl

@@ -70,7 +70,7 @@
         @test ComplexF64(1.5, z) === Complex{Float64}(1.5, 0.0)
 
         @test convert(Bool, ZeroTangent()) === false
-        @test convert(Int64, ZeroTangent()) === 0
+        @test convert(Int64, ZeroTangent()) === Int64(0)
         @test convert(Float32, ZeroTangent()) === 0.0f0
         @test convert(ComplexF64, ZeroTangent()) === 0.0 + 0.0im
     end