specialize real/imag/conj for real arrays

Author: jishnub

src/fillbroadcast.jl

@@ -145,6 +145,12 @@ function broadcast_preserving_0d(f, As...)
 end
 for f in (:real, :imag, :conj)
     @eval ($f)(A::AbstractFill) = broadcast_preserving_0d($f, A)
+    @eval ($f)(A::AbstractZeros) = A
+end
+for T in (:AbstractOnes, :(AbstractFill{<:Real}))
+    @eval real(A::$T) = A
+    @eval imag(A::$T) = Zeros{eltype(A)}(axes(A))
+    @eval conj(A::$T) = A
 end
 
 ### Binary broadcasting

test/runtests.jl

@@ -1170,9 +1170,25 @@ end
     end
 
     @testset "preserve 0d" begin
-        @test real(Fill(4 + 5im)) == real(fill(4 + 5im))
-        @test imag(Fill(4 + 5im)) == imag(fill(4 + 5im))
-        @test conj(Fill(4 + 5im)) == conj(fill(4 + 5im))
+        for f in (real, imag, conj),
+            (F, A) in ((Fill(4 + 5im), fill(4 + 5im)),
+                            (Zeros{ComplexF64}(), zeros(ComplexF64)),
+                            (Zeros(), zeros()),
+                            (Ones(), ones()),
+                            (Ones{ComplexF64}(), ones(ComplexF64)),
+                            )
+            x = f(F)
+            y = f(A)
+            @test x == y
+            @test x isa FillArrays.AbstractFill
+            if F[] isa Real
+                if f === imag
+                    @test x isa Zeros
+                else
+                    @test x isa typeof(F)
+                end
+            end
+        end
     end
 end