Fix ReinterpretArray's definition of strides to be inline with ArrayInterface's meaning

Author: chriselrod

src/stridelayout.jl

@@ -443,6 +443,27 @@ function strides(x)
         return Base.strides(x)
     end
 end
+@inline bmap(f::F, t::Tuple{}, x::Number) where {F} = ()
+@inline bmap(f::F, t::Tuple{T}, x::Number) where {F, T} = (f(first(t),x), )
+@inline bmap(f::F, t::Tuple, x::Number) where {F} = (f(first(t),x), bmap(f, Base.tail(t), x)...)
+if VERSION ≥ v"1.6.0-DEV.1581"
+  @inline @inline function strides(A::Base.ReinterpretArray{R, N, T, B, true}) where {R,N,T,B}
+    P = strides(parent(A))
+    if sizeof(R) == sizeof(T)
+      P
+    elseif sizeof(R) > sizeof(T)
+      x = Base.tail(P)
+      fx = first(x)
+      if fx isa Int
+        (One(), bmap(Base.sdiv_int, Base.tail(x), fx)...)
+      else
+        (One(), bmap(÷, Base.tail(x), fx)...)
+      end
+    else
+      (One(), bmap(*, P, StaticInt(sizeof(T)) ÷ StaticInt(sizeof(R)))...)
+    end
+  end
+end
 #@inline strides(A) = _strides(A, Base.strides(A), contiguous_axis(A))
 
 strides(::AbstractRange) = (One(),)

test/runtests.jl

@@ -647,6 +647,16 @@ end
         @test @inferred(ArrayInterface.dense_dims(view(Sr2,:,2))) === (True(),)
         @test @inferred(ArrayInterface.dense_dims(view(Sr2,:,2:3))) === (True(),True())
         @test @inferred(ArrayInterface.dense_dims(view(Sr2,2:3,:))) === (True(),False())
+
+        Ar2c = reinterpret(reshape, Complex{Float64}, view(rand(2, 5, 7), :, 2:4, 3:5));
+        @test @inferred(ArrayInterface.strides(Ar2c)) === (StaticInt(1), 5)
+
+        Ac2r = reinterpret(reshape, Float64, view(rand(ComplexF64, 5, 7), 2:4, 3:6));
+        @test @inferred(ArrayInterface.strides(Ac2r)) === (StaticInt(1), StaticInt(2), 10)
+      
+        Ac2t = reinterpret(reshape, Tuple{Float64,Float64}, view(rand(ComplexF64, 5, 7), 2:4, 3:6));
+        @test @inferred(ArrayInterface.strides(Ac2t)) === (StaticInt(1), 5)
+
     end
 end