Fix ambiguity in BandedLazy * Mul (#376)

* Fix ambiguity in BandedLazy * Mul

* Update bandedtests.jl

Author: dlfivefifty

ext/LazyArraysBandedMatricesExt.jl

@@ -594,6 +594,7 @@ copy(M::Mul{<:AbstractInvLayout, <:BandedLazyLayouts}) = simplify(M)
 
 copy(L::Ldiv{<:BandedLazyLayouts}) = lazymaterialize(\, L.A, L.B)
 copy(L::Ldiv{<:BandedLazyLayouts,<:AbstractLazyLayout}) = lazymaterialize(\, L.A, L.B)
+copy(L::Ldiv{<:BandedLazyLayouts, ApplyLayout{typeof(*)}}) = copy(Ldiv{UnknownLayout,ApplyLayout{typeof(*)}}(L.A, L.B))
 copy(L::Ldiv{<:BandedLazyLayouts, Blay}) where Blay<:Union{AbstractStridedLayout,PaddedColumns} = copy(Ldiv{UnknownLayout,Blay}(L.A, L.B))
 
 ## The following needs more thought but for now it fixes a bug downstream.

test/bandedtests.jl

@@ -861,6 +861,9 @@ LinearAlgebra.lmul!(β::Number, A::PseudoBandedMatrix) = (lmul!(β, A.data); A)
 
         @test A \ A ≈ I
         @test A \ A isa ApplyArray
+        
+        M = ApplyArray(*, randn(n,n), b)
+        @test A \ M ≈ Matrix(A) \ M
     end
 
     @testset "copyto! broadcast view" begin