Enable stride/strides to work on a ReinterpretArray with complex Stri…

…ded parents. (JuliaLang#37414)

base/reinterpretarray.jl

@@ -62,7 +62,14 @@ StridedVecOrMat{T} = Union{StridedVector{T}, StridedMatrix{T}}
 # a tuple containing 1 and a cumulative product of the first N-1 sizes
 # this definition is also used for StridedReshapedArray and StridedReinterpretedArray
 # which have the same memory storage as Array
-function stride(a::Union{DenseArray,StridedReshapedArray,StridedReinterpretArray}, i::Int)
+stride(a::Union{DenseArray,StridedReshapedArray,StridedReinterpretArray}, i::Int) = _stride(a, i)
+
+function stride(a::ReinterpretArray, i::Int)
+ a.parent isa StridedArray || ArgumentError("Parent must be strided.") |> throw
+ return _stride(a, i)
+end
+
+function _stride(a, i)
  if i > ndims(a)
  return length(a)
  end
@@ -73,6 +80,10 @@ function stride(a::Union{DenseArray,StridedReshapedArray,StridedReinterpretArray
  return s
 end
 
+function strides(a::ReinterpretArray)
+ a.parent isa StridedArray || ArgumentError("Parent must be strided.") |> throw
+ size_to_strides(1, size(a)...)
+end
 strides(a::Union{DenseArray,StridedReshapedArray,StridedReinterpretArray}) = size_to_strides(1, size(a)...)
 
 function check_readable(a::ReinterpretArray{T, N, S} where N) where {T,S}

test/reinterpretarray.jl

@@ -52,6 +52,14 @@ let A = collect(reshape(1:20, 5, 4))
  @test reshape(R, :) isa StridedArray
 end
 
+# and ensure a reinterpret array containing a strided array can have strides computed
+let A = view(reinterpret(Int16, collect(reshape(UnitRange{Int64}(1, 20), 5, 4))), :, 1:2)
+ R = reinterpret(Int32, A)
+ @test strides(R) == (1, 10)
+ @test stride(R, 1) == 1
+ @test stride(R, 2) == 10
+end
+
 @testset "strides" begin
  a = rand(10)
  b = view(a,2:2:10)