fix projecting Tangent{Complex} to Number (#535)

Author: mzgubic

Project.toml

@@ -1,6 +1,6 @@
 name = "ChainRulesCore"
 uuid = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
-version = "1.11.5"
+version = "1.11.6"
 
 [deps]
 Compat = "34da2185-b29b-5c13-b0c7-acf172513d20"

src/projection.jl

@@ -188,7 +188,7 @@ end
 
 # Tangents: we prefer to reconstruct numbers, but only safe to try when their constructor
 # understands, including a mix of Zeros & reals. Other cases, we just let through:
-(project::ProjectTo{<:Complex})(dx::Tangent{<:Complex}) = project(Complex(dx.re, dx.im))
+(project::ProjectTo{<:Number})(dx::Tangent{<:Complex}) = project(Complex(dx.re, dx.im))
 (::ProjectTo{<:Number})(dx::Tangent{<:Number}) = dx
 
 # Arrays

test/projection.jl

@@ -39,6 +39,8 @@ struct NoSuperType end
         # Tangents
         ProjectTo(1.0f0 + 2im)(Tangent{ComplexF64}(; re=1, im=NoTangent())) ===
         1.0f0 + 0.0f0im
+
+        @test 1.0 === ProjectTo(1.0)(Tangent{ComplexF64}(; re=1, im=NoTangent()))
     end
 
     @testset "Dual" begin # some weird Real subtype that we should basically leave alone