fix elsize and write for SubArrays of Arrays (#36739)

Author: JeffBezanson

base/io.jl

@@ -676,7 +676,7 @@ function write(s::IO, a::SubArray{T,N,<:Array}) where {T,N}
     if !isbitstype(T) || !isa(a, StridedArray)
         return invoke(write, Tuple{IO, AbstractArray}, s, a)
     end
-    elsz = sizeof(T)
+    elsz = elsize(a)
     colsz = size(a,1) * elsz
     GC.@preserve a if stride(a,1) != 1
         for idxs in CartesianIndices(size(a))

base/subarray.jl

@@ -67,6 +67,8 @@ similar(V::SubArray, T::Type, dims::Dims) = similar(V.parent, T, dims)
 sizeof(V::SubArray) = length(V) * sizeof(eltype(V))
 sizeof(V::SubArray{<:Any,<:Any,<:Array}) = length(V) * elsize(V.parent)
 
+elsize(::Type{<:SubArray{<:Any,<:Any,P}}) where {P<:Array} = elsize(P)
+
 copy(V::SubArray) = V.parent[V.indices...]
 
 parent(V::SubArray) = V.parent

test/subarray.jl

@@ -585,16 +585,16 @@ end
     @test IndexStyle(B18581) === IndexLinear()
 end
 
+primitive type UInt48 48 end
+UInt48(x::UInt64) = Core.Intrinsics.trunc_int(UInt48, x)
+UInt48(x::UInt32) = Core.Intrinsics.zext_int(UInt48, x)
+
 @testset "sizeof" begin
     @test sizeof(view(zeros(UInt8, 10), 1:4)) == 4
     @test sizeof(view(zeros(UInt8, 10), 1:3)) == 3
     @test sizeof(view(zeros(Float64, 10, 10), 1:3, 2:6)) == 120
 
     # Test non-power of 2 types (Issue #35884)
-    primitive type UInt48 48 end
-    UInt48(x::UInt64) = Core.Intrinsics.trunc_int(UInt48, x)
-    UInt48(x::UInt32) = Core.Intrinsics.zext_int(UInt48, x)
-
     a = UInt48(0x00000001);
     b = UInt48(0x00000002);
     c = UInt48(0x00000003);
@@ -607,6 +607,15 @@ end
     @test sizeof(view(Diagonal(zeros(Float64, 10)), 1:3, 2:6)) == 120
 end
 
+@testset "write" begin
+    io = IOBuffer()
+    a = UInt48[ UInt48(UInt32(i+j)) for i = 1:5, j = 1:5 ]
+    @test write(io, view(a, :, 2)) == 40
+    seekstart(io)
+    v = Vector{UInt48}(undef, 5)
+    read!(io, v)
+    @test v == view(a, :, 2)
+end
 
 @testset "unaliascopy trimming; Issue #26263" begin
     A = rand(5,5,5,5)