ambiguity in copy with banded * diagonal (#384)

* ambiguity in copy with banded * diagonal

* Update bandedtests.jl

Author: dlfivefifty

ext/LazyArraysBandedMatricesExt.jl

@@ -647,6 +647,7 @@ simplifiable(M::Mul{<:Union{AbstractStridedLayout,DualLayout{<:AbstractStridedLa
 simplifiable(M::Mul{<:BandedLayouts, <:AbstractStridedLayout}) = Val(true)
 
 copy(L::Ldiv{ApplyBandedLayout{typeof(*)}, Lay}) where Lay = copy(Ldiv{ApplyLayout{typeof(*)},Lay}(L.A, L.B))
+copy(L::Ldiv{ApplyBandedLayout{typeof(*)}, Lay}) where Lay<:DiagonalLayout = copy(Ldiv{ApplyLayout{typeof(*)},Lay}(L.A, L.B))
 copy(L::Ldiv{ApplyBandedLayout{typeof(*)}, Lay}) where {Lay<:AbstractLazyLayout} = copy(Ldiv{ApplyLayout{typeof(*)},Lay}(L.A, L.B))
 copy(L::Ldiv{ApplyBandedLayout{typeof(*)}, Lay}) where Lay<:BroadcastBandedLayout = copy(Ldiv{ApplyLayout{typeof(*)},Lay}(L.A, L.B))
 copy(L::Ldiv{ApplyBandedLayout{typeof(*)}, Lay}) where Lay<:Union{PaddedColumns,AbstractStridedLayout} = copy(Ldiv{ApplyLayout{typeof(*)},Lay}(L.A, L.B))

test/bandedtests.jl

@@ -959,6 +959,14 @@ LinearAlgebra.lmul!(β::Number, A::PseudoBandedMatrix) = (lmul!(β, A.data); A)
         @test rowsupport(invL, 1) == 1:1 
         @test rowsupport(invL, 4) == 1:4 
     end
+
+    @testset "banded \\ diagonal (#384)" begin
+        B = brand(5,5,2,1)
+        A = ApplyArray(*, B, B)
+        D = Diagonal(1:5)
+        @test A\D ≈ (B*B)\D
+        @test D\A ≈ D\(B*B)
+    end
 end
 
 end # module