Add (row/col)support for inv(Triangular) (#334)

* row/colsupport

* Dropped an import

* bump

Author: DanielVandH

src/linalg/inv.jl

@@ -184,4 +184,17 @@ getindex(L::ApplyMatrix{<:Any,typeof(/)}, k::Integer, ::Colon) = permutedims(L.a
 getindex(L::ApplyMatrix{<:Any,typeof(/)}, k::Integer, j::Integer) = L[k,:][j]
 
 
-inv_layout(::LazyLayouts, _, A) = ApplyArray(inv, A)
+inv_layout(::LazyLayouts, _, A) = ApplyArray(inv, A)
+
+### 
+# row/colsupport triangular
+###
+function colsupport(lay::AbstractInvLayout{<:TriangularLayout}, A, j)
+    B, = arguments(lay, A)
+    return colsupport(B, j)
+end 
+
+function rowsupport(lay::AbstractInvLayout{<:TriangularLayout}, A, k)
+    B, = arguments(lay, A)
+    return rowsupport(B, k)
+end

test/ldivtests.jl

@@ -1,6 +1,7 @@
 module LdivRdivTests
 
-using LazyArrays, LinearAlgebra, FillArrays, Test
+using LazyArrays, LinearAlgebra, FillArrays, Test, ArrayLayouts 
+import ArrayLayouts: rowsupport, colsupport
 import LazyArrays: InvMatrix, ApplyBroadcastStyle, LdivStyle, Applied, LazyLayout, simplifiable
 import Base.Broadcast: materialize
 
@@ -180,4 +181,20 @@ end
     @test Z \ Y ≈ [-2.0 1.0; 1.5 -0.5]
 end
 
+@testset "Issue #329" begin
+    for op in (UpperTriangular, UnitUpperTriangular)
+        A = UpperTriangular(ApplyArray(inv, rand(5, 5)))
+        B = inv(A)
+        @test colsupport.(Ref(B), 1:5) == Base.OneTo.(1:5)
+        @test rowsupport.(Ref(B), 1:5) == range.(1:5, 5)
+    end 
+
+    for op in (LowerTriangular, UnitLowerTriangular)
+        A = LowerTriangular(ApplyArray(inv, rand(15, 15)))
+        B = inv(A)
+        @test colsupport.(Ref(B), 1:15) == range.(1:15, 15)
+        @test rowsupport.(Ref(B), 1:15) == Base.OneTo.(1:15)
+    end
+end
+
 end # module