Empty KroneckerFusion constructor

Project.toml

@@ -1,7 +1,7 @@
 name = "KroneckerArrays"
 uuid = "05d0b138-81bc-4ff7-84be-08becefb1ccc"
 authors = ["ITensor developers <[email protected]> and contributors"]
-version = "0.3.5"
+version = "0.3.6"
 
 [deps]
 Adapt = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"

ext/KroneckerArraysTensorAlgebraExt/KroneckerArraysTensorAlgebraExt.jl

@@ -9,8 +9,14 @@ struct KroneckerFusion{A <: FusionStyle, B <: FusionStyle} <: FusionStyle
     a::A
     b::B
 end
+function KroneckerFusion{A, B}() where {A <: FusionStyle, B <: FusionStyle}
+    return KroneckerFusion{A, B}(A(), B())
+end
 KroneckerArrays.kroneckerfactors(style::KroneckerFusion) = (style.a, style.b)
 KroneckerArrays.kroneckerfactortypes(::Type{KroneckerFusion{A, B}}) where {A, B} = (A, B)
+function KroneckerArrays.:⊗(style1::FusionStyle, style2::FusionStyle)
+    return KroneckerFusion(style1, style2)
+end
 
 function TensorAlgebra.FusionStyle(A::Type{<:AbstractKroneckerArray})
     return KroneckerFusion(FusionStyle.(kroneckerfactortypes(A))...)

test/test_tensoralgebra.jl

@@ -1,8 +1,17 @@
-using TensorAlgebra: matricize, tensor_product_axis, trivial_axis, unmatricize
+using TensorAlgebra: FusionStyle, ReshapeFusion, matricize, tensor_product_axis,
+    trivial_axis, unmatricize
 using KroneckerArrays: ⊗, cartesianrange, kroneckerfactors, unproduct
 using Test: @test, @testset
 
 @testset "TensorAlgebraExt" begin
+    @testset "FusionStyle" begin
+        a1 = randn(2, 2, 2)
+        a2 = randn(2, 2, 2)
+        a = a1 ⊗ a2
+        @test FusionStyle(a) ≡ ReshapeFusion() ⊗ ReshapeFusion()
+        @test kroneckerfactors(FusionStyle(a)) ≡ (ReshapeFusion(), ReshapeFusion())
+        @test typeof(FusionStyle(a))() ≡ FusionStyle(a)
+    end
     @testset "tensor_product_axis" begin
         r = cartesianrange(2, 3)
         @test trivial_axis(r) ≡ cartesianrange(1, 1)