Avoid piracy changing empty args case

Author: DanielVandH

ext/LazyArraysBandedMatricesExt.jl

@@ -428,6 +428,7 @@ isbanded(::AbstractPaddedLayout, A) = true # always treat as banded
 const HcatBandedMatrix{T,N} = Hcat{T,NTuple{N,BandedMatrix{T,Matrix{T},OneTo{Int}}}}
 const VcatBandedMatrix{T,N} = Vcat{T,2,NTuple{N,BandedMatrix{T,Matrix{T},OneTo{Int}}}}
 
+BroadcastStyle(::Type{HcatBandedMatrix{T,0}}) where {T} = LazyArrayStyle{2}() # This method is needed for e.g. Hcat(), which would otherwise get recognised as a BandedStyle, giving different behaviour before-and-after loading BandedMatrices
 BroadcastStyle(::Type{HcatBandedMatrix{T,N}}) where {T,N} = BandedStyle()
 BroadcastStyle(::Type{VcatBandedMatrix{T,N}}) where {T,N} = BandedStyle()
 

test/concattests.jl

@@ -712,23 +712,23 @@ import Base.Broadcast: BroadcastStyle
         args = LazyArrays._vcat_sub_arguments(MemoryLayout(V), V, (), 0, 1:3)
         @test args == ()
     end
-end
 
-@testset "BroadcastStyle" begin
-    args = (1:10, Accumulate(*, 1:10), BroadcastVector(exp, 1:10), BroadcastMatrix(exp, rand(10, 2)), Vcat(Accumulate(*, 1:10)', (1:10)')', [1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
-    for i in 1:6 
-        @test @inferred(LazyArrays.tuple_type_broadcastlayout(typeof(args[1:i]))) == Base.Broadcast.combine_styles(args[1:i]...)
+    @testset "BroadcastStyle" begin
+        args = (1:10, Accumulate(*, 1:10), BroadcastVector(exp, 1:10), BroadcastMatrix(exp, rand(10, 2)), Vcat(Accumulate(*, 1:10)', (1:10)')', [1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
+        for i in 1:6 
+            @test @inferred(LazyArrays.tuple_type_broadcastlayout(typeof(args[1:i]))) == Base.Broadcast.combine_styles(args[1:i]...)
+        end
+        @test @inferred(LazyArrays.tuple_type_broadcastlayout(typeof(args))) == Base.Broadcast.combine_styles(args...) == CachedArrayStyle{2}()
+        @test @inferred(LazyArrays.tuple_type_broadcastlayout(Tuple{})) == Base.Broadcast.Unknown()
+        @test BroadcastStyle(typeof(Vcat(adjoint.(args)...))) == BroadcastStyle(typeof(Vcat(transpose.(args)...))) == CachedArrayStyle{2}()
+        @test BroadcastStyle(typeof(Hcat(args...))) == CachedArrayStyle{2}()
+        
+        @test BroadcastStyle(typeof(Vcat((1:10)'))) == LazyArrayStyle{2}() # make sure we preserve Lazy even without lazy args  
+        @test BroadcastStyle(typeof(Hcat((1:10)'))) == LazyArrayStyle{2}()
+        
+        @test BroadcastStyle(typeof(Vcat())) == LazyArrayStyle{1}() 
+        @test BroadcastStyle(typeof(Hcat())) == LazyArrayStyle{2}()
     end
-    @test @inferred(LazyArrays.tuple_type_broadcastlayout(typeof(args))) == Base.Broadcast.combine_styles(args...) == CachedArrayStyle{2}()
-    @test @inferred(LazyArrays.tuple_type_broadcastlayout(Tuple{})) == Base.Broadcast.Unknown()
-    @test BroadcastStyle(typeof(Vcat(adjoint.(args)...))) == BroadcastStyle(typeof(Vcat(transpose.(args)...))) == CachedArrayStyle{2}()
-    @test BroadcastStyle(typeof(Hcat(args...))) == CachedArrayStyle{2}()
-    
-    @test BroadcastStyle(typeof(Vcat((1:10)'))) == LazyArrayStyle{2}() # make sure we preserve Lazy even without lazy args  
-    @test BroadcastStyle(typeof(Hcat((1:10)'))) == LazyArrayStyle{2}()
-    
-    @test BroadcastStyle(typeof(Vcat())) == LazyArrayStyle{1}() 
-    @test BroadcastStyle(typeof(Hcat())) == LazyArrayStyle{2}()
 end
 
 end # module

test/runtests.jl

@@ -15,6 +15,13 @@ end
 # we include this at the top-level, so that other sub-modules may reuse the module instead of having to include the file
 include("infinitearrays.jl")
 
+@testset "Avoiding unwanted behaviour from BandedMatrices extension" begin
+    # This test needs to be included before BandedMatrices is loaded 
+    @test Base.Broadcast.BroadcastStyle(typeof(Hcat())) == LazyArrayStyle{2}()
+    using BandedMatrices 
+    @test Base.Broadcast.BroadcastStyle(typeof(Hcat())) == LazyArrayStyle{2}()
+end
+
 @testset "Lazy MemoryLayout" begin
     @testset "ApplyArray" begin
         A = [1.0 2; 3 4]