Forward copyto! for Adjoint to adjoint! (#51650)

Author: jishnub

src/transpose.jl

@@ -210,3 +210,13 @@ function copy_similar(A::TransposeAbsMat, ::Type{T}) where {T}
     C = similar(A, T, size(A))
     transpose!(C, parent(A))
 end
+
+function Base.copyto_unaliased!(deststyle::IndexStyle, dest::AbstractMatrix, srcstyle::IndexCartesian, src::AdjOrTransAbsMat)
+    if axes(dest) == axes(src)
+        f! = inplace_adj_or_trans(src)
+        f!(dest, parent(src))
+    else
+        @invoke Base.copyto_unaliased!(deststyle::IndexStyle, dest::AbstractArray, srcstyle::IndexStyle, src::AbstractArray)
+    end
+    return dest
+end

test/adjtrans.jl

@@ -476,6 +476,16 @@ end
     @test adjoint!(b, a) === b
 end
 
+@testset "copyto! uses adjoint!/transpose!" begin
+    for T in (Float64, ComplexF64), f in (transpose, adjoint), sz in ((5,4), (5,))
+        S = rand(T, sz)
+        adjS = f(S)
+        A = similar(S')
+        copyto!(A, adjS)
+        @test A == adjS
+    end
+end
+
 @testset "aliasing with adjoint and transpose" begin
     A = collect(reshape(1:25, 5, 5)) .+ rand.().*im
     B = copy(A)