githubmirror/julia

test/subarray.jl
1 157 строк39 KB
Yichao Yu
Fix at-views for setindex expression (#59403)
06 окт 2025, 18:15
06 окт 2025, 18:15406027e
# This file is a part of Julia. License is MIT: https://julialang.org/license

using Test, Random, LinearAlgebra

######## Utilities ###########

# Generate an array similar to A[indx1, indx2, ...], but only call
# getindex with scalar-valued indices. This will be safe even if
# `getindex` someday calls `view`.

# The "nodrop" variant does not drop any dimensions (not even trailing ones)
function Agen_nodrop(A::AbstractArray, I...)
    irep = replace_colon(A, I)
    _Agen(A, ensure_iterable(irep)...)
end

# This drops scalar dimensions
function Agen_slice(A::AbstractArray, I...)
    irep = replace_colon(A, I)
    B = _Agen(A, ensure_iterable(irep)...)
    sd = Int[]
    for i = 1:length(I)
        if isa(I[i], Real)
            push!(sd, i)
        end
    end
    dropdims(B, dims=sd)
end

_Agen(A, i1) = [A[j1] for j1 in i1]
_Agen(A, i1, i2) = [A[j1,j2] for j1 in i1, j2 in i2]
_Agen(A, i1, i2, i3) = [A[j1,j2,j3] for j1 in i1, j2 in i2, j3 in i3]
_Agen(A, i1, i2, i3, i4) = [A[j1,j2,j3,j4] for j1 in i1, j2 in i2, j3 in i3, j4 in i4]
_Agen(A, i1, i2, i3, i4, i5) = [A[j1,j2,j3,j4,j5] for j1 in i1, j2 in i2, j3 in i3, j4 in i4, j5 in i5]
_Agen(A, i1, i2, i3, i4, i5, i6) = [A[j1,j2,j3,j4,j5,j6] for j1 in i1, j2 in i2, j3 in i3, j4 in i4, j5 in i5, j6 in i6]

function replace_colon(A::AbstractArray, I)
    Iout = Vector{Any}(undef, length(I))
    I === (:,) && return (1:length(A),)
    for d = 1:length(I)
        Iout[d] = isa(I[d], Colon) ? (1:size(A,d)) : I[d]
    end
    (Iout...,)
end

ensure_iterable(::Tuple{}) = ()
ensure_iterable(t::Tuple{Union{Number, CartesianIndex}, Vararg{Any}}) = ((t[1],), ensure_iterable(Base.tail(t))...)
ensure_iterable(t::Tuple{Any, Vararg{Any}}) = (t[1], ensure_iterable(Base.tail(t))...)

index_ndims(t::Tuple) = tup2val(Base.index_ndims(t))
tup2val(::NTuple{N}) where {N} = Val(N)

# To avoid getting confused by manipulations that are implemented for SubArrays,
# it's good to copy the contents to an Array. This version protects against
# `similar` ever changing its meaning.
function copy_to_array(A::AbstractArray)
    Ac = Array{eltype(A)}(undef, size(A))
    copyto!(Ac, A)
end

# Discover the highest dimension along which the values in A are
# separated by a single increment.  If A was extracted via getindex
# from reshape(1:N, ...), this is equivalent to finding the highest
# dimension of the SubArray consistent with a single stride in the
# parent array.
function single_stride_dim(A::Array)
    ld = 0
    while ld < ndims(A)
        # Collapse all dimensions up to & including ld+1 into the first dimension
        shp = [prod(size(A)[1:ld+1])]
        for j = ld+2:ndims(A)
            push!(shp, size(A,j))
        end
        Ar = reshape(A, shp...)
        # Compute the diff along dimension 1
        if size(Ar, 1) > 1
            indices = map(d->1:size(Ar,d), [1:ndims(Ar);])
            indicesp = copy(indices); indicesp[1] = 2:size(Ar,1)
            indicesm = copy(indices); indicesm[1] = 1:size(Ar,1)-1
            dA = Ar[indicesp...] - Ar[indicesm...]
            ustride = unique(dA[:])
            if length(ustride) == 1  # is it a single stride?
                ld += 1
            else
                break
            end
        else
            ld += 1
        end
    end
    ld
end
single_stride_dim(@nospecialize(A)) = single_stride_dim(copy_to_array(A))

# Testing equality of AbstractArrays, using several different methods to access values
function test_cartesian(@nospecialize(A), @nospecialize(B))
    isgood = true
    for (IA, IB) in zip(CartesianIndices(A), CartesianIndices(B))
        @test A[IA] == B[IB]
        if A isa StridedArray
            v1 = GC.@preserve A unsafe_load(pointer(A.parent, sum((0,(strides(A) .* (IA.I .- 1))...))+Base.first_index(A)))
            @test v1 == B[IB]
        end
    end
end

function test_linear(@nospecialize(A), @nospecialize(B))
    @test length(A) == length(B)
    isgood = true
    for (iA, iB) in zip(1:length(A), 1:length(B))
        @test A[iA] == B[iB]
        if A isa StridedArray
            v1 = GC.@preserve A unsafe_load(pointer(A, iA))
            v2 = Ref(A, iA)[]
            @test v1 == v2 == B[iB]
        end
    end
end

# "mixed" means 2 indices even for N-dimensional arrays
test_mixed(::AbstractArray{T,1}, ::Array) where {T} = nothing
test_mixed(::AbstractArray{T,2}, ::Array) where {T} = nothing
test_mixed(A, B::Array) = _test_mixed(A, reshape(B, size(A)))
function _test_mixed(@nospecialize(A), @nospecialize(B))
    m = size(A, 1)
    n = size(A, 2)
    isgood = true
    for J in CartesianIndices(size(A)[2:end]), i in 1:m
        @test A[i,J] == B[i,J]
    end
    nothing
end

function test_bounds(@nospecialize(A))
    @test_throws BoundsError A[0]
    @test_throws BoundsError A[end+1]
    trailing2 = ntuple(Returns(1), max(ndims(A)-2, 0))
    trailing3 = ntuple(Returns(1), max(ndims(A)-3, 0))
    @test_throws BoundsError A[1, 0, trailing2...]
    @test_throws BoundsError A[1, end+1, trailing2...]
    @test_throws BoundsError A[1, 1, 0, trailing3...]
    @test_throws BoundsError A[1, 1, end+1, trailing3...]
    @test_throws BoundsError A[0, 1, trailing2...]
    @test_throws BoundsError A[end+1, 1, trailing2...]
    @test_throws BoundsError A[0, 1, 1, trailing3...]
    @test_throws BoundsError A[end+1, 1, 1, trailing3...]
    @test_throws BoundsError A[1, 0, 1, trailing3...]
    @test_throws BoundsError A[1, end+1, 1, trailing3...]
    @test_throws BoundsError A[1, 0]
    @test_throws BoundsError A[1, end+1]
    @test_throws BoundsError A[1, 1, 0]
    @test_throws BoundsError A[1, 1, end+1]
    @test_throws BoundsError A[0, 1]
    @test_throws BoundsError A[end+1, 1]
    @test_throws BoundsError A[0, 1, 1]
    @test_throws BoundsError A[end+1, 1, 1]
    @test_throws BoundsError A[1, 0, 1]
    @test_throws BoundsError A[1, end+1, 1]
end

function dim_break_linindex(I)
    i = 1
    while i <= length(I) && !isa(I[i], Vector{Int})
        i += 1
    end
    i - 1
end

function runsubarraytests(A::Array, I...)
    # Direct test of linear indexing inference
    C = Agen_nodrop(A, I...)
    ld = min(single_stride_dim(C), dim_break_linindex(I))
    S = view(A, I...)
    if Base.iscontiguous(S)
        @test S.stride1 == 1
    end
    test_linear(S, C)
    test_cartesian(S, C)
    test_mixed(S, C)
end

function runsubarraytests(@nospecialize(A), I...)
    # When A was created with view, we have to check bounds, since some
    # of the "residual" dimensions have size 1. It's possible that we
    # need dedicated tests for view.
    for d = 1:length(I)-1
        if !isa(I[d], Colon) && any(I[d] .> size(A,d))
            return nothing
        end
    end
    if !isa(I[end], Colon) && any(I[end] .> prod(size(A)[length(I):end]))
        return nothing
    end
    AA = copy_to_array(A)
    # Direct test of linear indexing inference
    C = Agen_nodrop(AA, I...)
    Cld = ld = min(single_stride_dim(C), dim_break_linindex(I))
    Cdim = AIindex = 0
    while Cdim <= Cld && AIindex < length(A.indices)
        AIindex += 1
        if isa(A.indices[AIindex], Real)
            ld += 1
        else
            Cdim += 1
        end
    end
    S = view(A, I...)
    test_linear(S, C)
    test_cartesian(S, C)
    test_mixed(S, C)
end

# indexN is a cartesian index, indexNN is a linear index for 2 dimensions, and indexNNN is a linear index for 3 dimensions
function runviews(SB::AbstractArray, indexN, indexNN, indexNNN)
    @assert ndims(SB) > 2
    for i3 in indexN, i2 in indexN, i1 in indexN
        runsubarraytests(SB, i1, i2, i3, ntuple(Returns(1), max(ndims(SB)-3, 0))...)
    end
    for i2 in indexN, i1 in indexN
        runsubarraytests(SB, i1, i2, ntuple(Returns(1), max(ndims(SB)-2, 0))...)
    end
    for i1 in indexNNN
        runsubarraytests(SB, i1)
    end
end

function runviews(SB::AbstractArray{T, 3} where T, indexN, indexNN, indexNNN)
    @assert ndims(SB) > 2
    for i3 in indexN, i2 in indexN, i1 in indexN
        runsubarraytests(SB, i1, i2, i3)
    end
    for i2 in indexN, i1 in indexN
        runsubarraytests(SB, i1, i2, 1)
    end
    for i1 in indexNNN
        runsubarraytests(SB, i1)
    end
end

function runviews(SB::AbstractArray{T,2}, indexN, indexNN, indexNNN) where T
    for i2 in indexN, i1 in indexN
        runsubarraytests(SB, i1, i2)
    end
    for i1 in indexNN
        runsubarraytests(SB, i1)
    end
end

function runviews(SB::AbstractArray{T,1}, indexN, indexNN, indexNNN) where T
    for i1 in indexN
        runsubarraytests(SB, i1)
    end
end

runviews(SB::AbstractArray{T,0}, indexN, indexNN, indexNNN) where {T} = nothing

######### Tests #########

testfull = Base.get_bool_env("JULIA_TESTFULL", false)

### Views from Arrays ###
index5 = (1, :, 2:5, [4,1,5], reshape([2]), view(1:5,[2 3 4 1]))  # all work with at least size 5
index25 = (3, :, 2:11, [19,9,7], reshape([10]), view(1:25,[19 15; 4 24]))
index125 = (113, :, 85:121, [99,14,103], reshape([72]), view(1:125,reshape([25,4,102,67], 1, 2, 2)))

if testfull
    let A = copy(reshape(1:5*7*11, 11, 7, 5))
        runviews(A, index5, index25, index125)
    end
end

### Views from views ###

# "outer" indices create snips that have at least size 5 along each dimension,
# with the exception of Int-slicing
oindex = (:, 6, 3:7, reshape([12]), [8,4,6,12,5,7], [3:7 1:5 2:6 4:8 5:9], reshape(2:11, 2, 5))

if testfull
    let B = copy(reshape(1:13^3, 13, 13, 13))
        @testset "full tests: ($o1,$o2,$o3)" for o3 in oindex, o2 in oindex, o1 in oindex
            viewB = view(B, o1, o2, o3)
            runviews(viewB, index5, index25, index125)
        end
    end
end

let B = copy(reshape(1:13^3, 13, 13, 13))
    @testset "spot checks: $oind" for oind in (
                 (:,:,:),
                 (:,:,6),
                 (:,6,:),
                 (6,:,:),
                 (:,3:7,:),
                 (3:7,:,:),
                 (3:7,6,:),
                 (3:7,6,0x6),
                 (13:-2:1,:,:),
                 ([8,4,6,12,5,7],:,3:7),
                 (6,CartesianIndex.(6,[8,4,6,12,5,7])),
                 (CartesianIndex(13,6),[8,4,6,12,5,7]),
                 (1,:,view(1:13,[9,12,4,13,1])),
                 (2,:,reshape(2:11,2,5)),
                 (2,:,reshape(2:2:13,2,3)),
                 (3,reshape(2:11,5,2),4),
                 (3,reshape(2:2:13,3,2),4),
                 (view(1:13,[9,12,4,13,1]),2:6,4),
                 ([1:5 2:6 3:7 4:8 5:9], :, 3),
        )
        runsubarraytests(B, oind...)
        viewB = view(B, oind...)
        runviews(viewB, index5, index25, index125)
    end
end

let B = copy(reshape(1:13^3, 13, 13, 13))
    @testset "spot checks (other BitIntegers): $oind" for oind in (
                 (:,:,0x6),
                 (:,0x00000006,:),
                 (0x0006,:,:),
                 (:,0x00000003:0x00000007,:),
                 (0x0000000000000003:0x0000000000000007,:,:),
                 (0x0003:0x0007,0x6,:),
                 (6,UInt(3):UInt(7),3:7),
                 (Int16(3):Int16(7),Int16(6),:),
                 (CartesianIndex(0xD,0x6),UInt8[8,4,6,12,5,7]),
                 (Int8(1),:,view(1:13,[9,12,4,13,1])),
                 (view(1:13,Int16[9,12,4,13,1]),UInt8(2):UInt16(6),Int8(4)),
                 (Int8[1:5 2:6 3:7 4:8 5:9],:,UInt64(3)),
        )
        runsubarraytests(B, oind...)
        viewB = view(B, oind...)
        runviews(viewB, index5, index25, index125)
    end
end

####### "Classical" tests #######

@testset "non-trailing dimensions" begin
    A = copy(reshape(1:120, 3, 5, 8))
    sA = view(A, 2:2, 1:5, :)
    @test @inferred(strides(sA)) == (1, 3, 15)
    @test IndexStyle(sA) == IndexStyle(typeof(sA)) == IndexCartesian()
    @test parent(sA) == A
    @test parentindices(sA) == (2:2, 1:5, Base.Slice(1:8))
    @test size(sA) == (1, 5, 8)
    @test axes(sA) === (Base.OneTo(1), Base.OneTo(5), Base.OneTo(8))
    @test sA[1, 2, 1:8][:] == [5:15:120;]
    sA[2:5:end] .= -1
    @test all(sA[2:5:end] .== -1)
    @test all(A[5:15:120] .== -1)
    @test @inferred(strides(sA)) == (1,3,15)
    @test stride(sA,3) == 15
    @test stride(sA,4) == 120
    test_bounds(sA)
    sA = view(A, 1:3, 1:5, 5)
    sA[1:3,1:5] .= -2
    @test all(A[:,:,5] .== -2)
    fill!(sA, -3)
    @test all(A[:,:,5] .== -3)
    sA[:] .= 4
    @test all(A[:,:,5] .== 4)
    @test @inferred(strides(sA)) == (1,3)
    test_bounds(sA)
    sA = view(A, 1:3, 3:3, 2:5)
    @test size(sA) == (3,1,4)
    @test axes(sA) === (Base.OneTo(3), Base.OneTo(1), Base.OneTo(4))
    @test sA == A[1:3,3:3,2:5]
    @test sA[:] == A[1:3,3,2:5][:]
    test_bounds(sA)
    sA = view(A, 1:2:3, 1:3:5, 1:2:8)
    @test @inferred(strides(sA)) == (2,9,30)
    @test sA[:] == A[1:2:3, 1:3:5, 1:2:8][:]
    # issue #8807
    @test view(view([1:5;], 1:5), 1:5) == [1:5;]
    # Test with mixed types
    @test sA[:, Int16[1,2], big(2)] == [31 40; 33 42]
    test_bounds(sA)
    sA = view(A, 1:1, 1:5, [1 3; 4 2])
    @test ndims(sA) == 4
    @test axes(sA) === (Base.OneTo(1), Base.OneTo(5), Base.OneTo(2), Base.OneTo(2))
    sA = view(A, 1:2, 3, [1 3; 4 2])
    @test ndims(sA) == 3
    @test axes(sA) === (Base.OneTo(2), Base.OneTo(2), Base.OneTo(2))
    @test axes(similar(typeof(A),axes(A))) == axes(A)
    @test eltype(similar(typeof(A),axes(A))) == eltype(A)
end

@testset "logical indexing #4763" begin
    A = view([1:10;], 5:8)
    @test A[A.<7] == view(A, A.<7) == [5, 6]
    @test Base.unsafe_getindex(A, A.<7) == [5, 6]
    B = reshape(1:16, 4, 4)
    sB = view(B, 2:3, 2:3)
    @test sB[sB.>8] == view(sB, sB.>8) == [10, 11]
    @test Base.unsafe_getindex(sB, sB.>8) == [10, 11]
end

@testset "with dropped dimensions" begin
    A = copy(reshape(1:120, 3, 5, 8))
    sA = view(A, 2, :, 1:8)
    @test parent(sA) == A
    @test parentindices(sA) == (2, Base.Slice(1:5), 1:8)
    @test size(sA) == (5, 8)
    @test axes(sA) === (Base.OneTo(5), Base.OneTo(8))
    @test @inferred(strides(sA)) == (3,15)
    @test sA[2, 1:8][:] == [5:15:120;]
    @test sA[:,1] == [2:3:14;]
    @test sA[2:5:end] == [5:15:110;]
    sA[2:5:end] .= -1
    @test all(sA[2:5:end] .== -1)
    @test all(A[5:15:120] .== -1)
    test_bounds(sA)
    sA = view(A, 1:3, 1:5, 5)
    @test size(sA) == (3,5)
    @test axes(sA) === (Base.OneTo(3),Base.OneTo(5))
    @test @inferred(strides(sA)) == (1,3)
    test_bounds(sA)
    sA = view(A, 1:2:3, 3, 1:2:8)
    @test size(sA) == (2,4)
    @test axes(sA) === (Base.OneTo(2), Base.OneTo(4))
    @test @inferred(strides(sA)) == (2,30)
    @test sA[:] == A[sA.indices...][:]
    test_bounds(sA)
end

@testset "parent" begin
    a = [5:8;]
    @test parent(a) == a
    @test parentindices(a) == (1:4,)
end

@testset "issue #11289" begin
    x11289 = randn(5,5)
    @test isempty(view(x11289, Int[], :))
    @test isempty(view(x11289, [2,5], Int[]))
    @test isempty(view(x11289, Int[], 2))
end


@testset "issue #6218 - logical indexing" begin
    A = rand(2, 2, 3)
    msk = fill(true, 2, 2)
    msk[2,1] = false
    sA = view(A, :, :, 1)
    sA[msk] .= 1.0
    @test sA[msk] == fill(1, count(msk))
end

@testset "bounds checking upon construction; see #4044, #10296" begin
    @test_throws BoundsError view(1:10, 8:11)
    A = reshape(1:20, 5, 4)
    sA = view(A, 1:2, 1:3)
    @test_throws BoundsError view(sA, 1:3, 1:3)
    @test_throws BoundsError view(sA, 1:2, 1:4)
    view(sA, 1:2, 1:2)
    @test_throws BoundsError view(A, 17:23)
    view(A, 17:20)
end

@testset "Linear indexing by one multidimensional array" begin
    A = reshape(1:120, 3, 5, 8)
    sA = view(A, :, :, :)
    @test sA[[72 17; 107 117]] == [72 17; 107 117]
    @test sA[[99 38 119 14 76 81]] == [99 38 119 14 76 81]
    @test sA[[fill(1, (2, 2, 2)); fill(2, (2, 2, 2))]] == [fill(1, (2, 2, 2)); fill(2, (2, 2, 2))]
    sA = view(A, 1:2, 2:3, 3:4)
    @test sA[(1:8)'] == [34 35 37 38 49 50 52 53]
    @test sA[[1 2 4 4; 6 1 1 4]] == [34 35 38 38; 50 34 34 38]
end

@testset "fast linear indexing with AbstractUnitRange or Colon indices" begin
    @testset "getindex" begin
        @testset "1D" begin
            for a1 in Any[1:5, [1:5;]]
                b1 = @view a1[:]; # FastContiguousSubArray
                c1 = @view a1[eachindex(a1)]; # FastContiguousSubArray
                d1 = @view a1[begin:1:end]; # FastSubArray

                ax1 = eachindex(a1);
                @test b1[ax1] == c1[ax1] == d1[ax1] == a1[ax1]
                @test b1[:] == c1[:] == d1[:] == a1[:]

                # some arbitrary indices
                inds1 = 2:4
                c1 = @view a1[inds1]
                @test c1[axes(c1,1)] == c1[:] == a1[inds1]

                inds12 = Base.IdentityUnitRange(Base.OneTo(4))
                c1 = @view a1[inds12]
                @test c1[axes(c1,1)] == c1[:] == a1[inds12]

                inds2 = 3:2:5
                d1 = @view a1[inds2]
                @test d1[axes(d1,1)] == d1[:] == a1[inds2]
            end
        end

        @testset "2D" begin
            a2_ = reshape(1:25, 5, 5)
            for a2 in Any[a2_, collect(a2_)]
                b2 = @view a2[:, :]; # 2D FastContiguousSubArray
                b22 = @view a2[:]; # 1D FastContiguousSubArray
                c2 = @view a2[eachindex(a2)]; # 1D FastContiguousSubArray
                d2 = @view a2[begin:1:end]; # 1D FastSubArray

                ax2 = eachindex(a2);
                @test b2[ax2] == b22[ax2] == c2[ax2] == d2[ax2] == a2[ax2]
                @test b2[:] == b22[:] == c2[:] == d2[:] == a2[:]

                # some arbitrary indices
                inds1 = 2:4
                c2 = @view a2[inds1]
                @test c2[axes(c2,1)] == c2[:] == a2[inds1]

                inds12 = Base.IdentityUnitRange(Base.OneTo(4))
                c2 = @view a2[inds12]
                @test c2[axes(c2,1)] == c2[:] == a2[inds12]

                inds2 = 2:2:4
                d2 = @view a2[inds2];
                @test d2[axes(d2,1)] == d2[:] == a2[inds2]
            end
        end
    end
    @testset "setindex!" begin
        @testset "1D" begin
            a1 = rand(10);
            a12 = copy(a1);
            b1 = @view a1[:]; # 1D FastContiguousSubArray
            c1 = @view a1[eachindex(a1)]; # 1D FastContiguousSubArray
            d1 = @view a1[begin:1:end]; # 1D FastSubArray

            ax1 = eachindex(a1);
            @test (b1[ax1] = a12; b1) == (c1[ax1] = a12; c1) == (d1[ax1] = a12; d1) == (a1[ax1] = a12; a1)
            @test (b1[:] = a12; b1) == (c1[:] = a12; c1) == (d1[:] = a12; d1) == (a1[:] = a12; a1)

            # some arbitrary indices
            ind1 = 2:4
            c1 = a12[ind1]
            @test (c1[axes(c1,1)] = a12[ind1]; c1) == (c1[:] = a12[ind1]; c1) == a12[ind1]

            inds1 = Base.IdentityUnitRange(Base.OneTo(4))
            c1 = @view a1[inds1]
            @test (c1[eachindex(c1)] = @view(a12[inds1]); c1) == @view(a12[inds1])

            ind2 = 2:2:8
            d1 = a12[ind2]
            @test (d1[axes(d1,1)] = a12[ind2]; d1) == (d1[:] = a12[ind2]; d1) == a12[ind2]
        end

        @testset "2D" begin
            a2 = rand(10, 10);
            a22 = copy(a2);
            a2v = vec(a22);
            b2 = @view a2[:, :]; # 2D FastContiguousSubArray
            c2 = @view a2[eachindex(a2)]; # 1D FastContiguousSubArray
            d2 = @view a2[begin:1:end]; # 1D FastSubArray

            @test (b2[eachindex(b2)] = a2v; vec(b2)) == (c2[eachindex(c2)] = a2v; c2) == a2v
            @test (d2[eachindex(d2)] = a2v; d2) == a2v

            # some arbitrary indices
            inds1 = 3:9
            c2 = @view a2[inds1]
            @test (c2[eachindex(c2)] = @view(a22[inds1]); c2) == @view(a22[inds1])

            inds1 = Base.IdentityUnitRange(Base.OneTo(4))
            c2 = @view a2[inds1]
            @test (c2[eachindex(c2)] = @view(a22[inds1]); c2) == @view(a22[inds1])

            inds2 = 3:3:9
            d2 = @view a2[inds2]
            @test (d2[eachindex(d2)] = @view(a22[inds2]); d2) == @view(a22[inds2])
        end
    end
end

@testset "issue #11871" begin
    a = fill(1., (2,2))
    b = view(a, 1:2, 1:2)
    b[2] = 2
    @test b[2] === 2.0
end

@testset "issue #15138" begin
    a = [1,2,3]
    b = view(a, UInt(1):UInt(2))
    @test b == view(a, UInt(1):UInt(2)) == view(view(a, :), UInt(1):UInt(2)) == [1,2]
end

@testset "unsigned index" begin
    A = reshape(1:4, 2, 2)
    B = view(A, :, :)
    @test parent(B) === A
    @test parent(view(B, 0x1, :)) === parent(view(B, 0x1, :)) === A
end

@testset "issue #15168" begin
    A = rand(10)
    sA = view(copy(A), :)
    @test sA[Int16(1)] === sA[Int32(1)] === sA[Int64(1)] === A[1]
    permute!(sA, Vector{Int16}(1:10))
    @test A == sA
end

# the following segfaults with LLVM 3.8 on Windows, ref #15417
@test Array(view(view(reshape(1:13^3, 13, 13, 13), 3:7, 6:6, :), 1:2:5, :, 1:2:5)) ==
    cat([68,70,72],[406,408,410],[744,746,748]; dims=3)

@testset "@view (and replace_ref_begin_end!)" begin
    @test_throws ArgumentError(
        "Invalid use of @view macro: argument must be a reference expression A[...]."
    ) var"@view"(LineNumberNode(@__LINE__), @__MODULE__, 1)

    X = reshape(1:24,2,3,4)
    Y = 4:-1:1

    @test isa(@view(X[1:3]), SubArray)

    @test X[begin:end] == @.(@view X[begin:end]) # test compatibility of @. and @view
    @test X[begin:end-3] == @view X[begin:end-3]
    @test X[1:end,2,begin+1] == @view X[1:end,2,begin+1]
    @test X[begin,1:end-2,1] == @view X[begin,1:end-2,1]
    @test X[begin,begin+1,begin:end-2] == @view X[begin,begin+1,begin:end-2]
    @test X[begin,2,Y[2:end]] == @view X[begin,2,Y[2:end]]
    @test X[begin:end,2,Y[begin+1:end]] == @view X[begin:end,2,Y[begin+1:end]]

    u = (1,2:3)
    @test X[u...,begin+1:end] == @view X[u...,begin+1:end]
    @test X[(1,)...,(2,)...,2:end] == @view X[(1,)...,(2,)...,2:end]

    # test macro hygiene
    let size=(x,y)-> error("should not happen"), Base=nothing
        @test X[1:end,2,2] == @view X[1:end,2,2]
    end

    # test that side effects occur only once
    let foo = [X]
        @test X[2:end-1] == @view (push!(foo,X)[1])[2:end-1]
        @test foo == [X, X]
    end

    # Test as an assignment's left hand side
    let x = [1,2,3,4]
        @test Meta.@lower(@view(x[1]) = 1).head == :error
        @test Meta.@lower(@view(x[1]) += 1).head == :error
        @test Meta.@lower(@view(x[end]) = 1).head == :error
        @test Meta.@lower(@view(x[end]) += 1).head == :error
        @test Meta.@lower(@view(f(x)[end]) = 1).head == :error
        @test Meta.@lower(@view(f(x)[end]) += 1).head == :error
        @test (@view(x[1]) .+= 1) == fill(2)
        @test x == [2,2,3,4]
        @test (@view(reshape(x,2,2)[1,1]) .+= 10) == fill(12)
        @test x == [12,2,3,4]
        @test (@view(x[end]) .+= 1) == fill(5)
        @test x == [12,2,3,5]
        @test (@view(reshape(x,2,2)[end]) .+= 10) == fill(15)
        @test x == [12,2,3,15]
        @test (@view(reshape(x,2,2)[[begin],[begin,end]])::AbstractMatrix{Int} .+= [2]) == [14 5]
        @test x == [14,2,5,15]

        x = [1,2,3,4]
        @test Meta.@lower(@views(x[[1]]) = 1).head == :error
        @test Meta.@lower(@views(x[[1]]) += 1).head == :error
        @test Meta.@lower(@views(x[[end]]) = 1).head == :error
        @test Meta.@lower(@views(x[[end]]) += 1).head == :error
        @test Meta.@lower(@views(f(x)[end]) = 1).head == :error
        @test Meta.@lower(@views(f(x)[end]) += 1).head == :error
        @test (@views(x[[1]]) .+= 1) == [2]
        @test x == [2,2,3,4]
        @test (@views(reshape(x,2,2)[[1],1]) .+= 10) == [12]
        @test x == [12,2,3,4]
        @test (@views(x[[end]]) .+= 1) == [5]
        @test x == [12,2,3,5]
        @test (@views(reshape(x,2,2)[[end]]) .+= 10) == [15]
        @test x == [12,2,3,15]
        @test (@views(reshape(x,2,2)[[begin],[begin,end]])::AbstractMatrix{Int} .+= [2]) == [14 5]
        @test x == [14,2,5,15]
    end

    # test @views macro
    @views let f!(x) = x[begin:end-1] .+= x[begin+1:end].^2
        x = [1,2,3,4]
        f!(x)
        @test x == [5,11,19,4]
        @test x[1:3] isa SubArray
        @test x[2] === 11
        @test Dict((1:3) => 4)[1:3] === 4
        x[1:2] .= 0
        @test x == [0,0,19,4]
        x[1:2] .= 5:6
        @test x == [5,6,19,4]
        f!(x[3:end])
        @test x == [5,6,35,4]
        x[Y[2:3]] .= 7:8
        @test x == [5,8,7,4]
        x[(3,)..., ()...] += 3
        @test x == [5,8,10,4]
        i = Int[]
        # test that lhs expressions in update operations are evaluated only once:
        x[push!(i,4)[1]] += 5
        @test x == [5,8,10,9] && i == [4]
        x[push!(i,3)[end]] += 2
        @test x == [5,8,12,9] && i == [4,3]
        @. x[3:end] = 0       # make sure @. works with end expressions in @views
        @test x == [5,8,0,0]
        x[begin:end] .+= 1
        @test x == [6,9,1,1]
        x[[begin,2,end]] .-= [1,2,3]
        @test x == [5,7,1,-2]
        @. x[[begin,2,end]] .+= [1,2,3]
        @test x == [6,9,1,1]
    end
    @views @test isa(X[1:3], SubArray)
    @test X[begin:end] == @views X[begin:end]
    @test X[begin:end-3] == @views X[begin:end-3]
    @test X[1:end,2,begin+1] == @views X[1:end,2,begin+1]
    @test X[begin,2,1:end-2] == @views X[begin,2,1:end-2]
    @test X[begin,2,Y[2:end]] == @views X[begin,2,Y[2:end]]
    @test X[begin:end,2,Y[begin+1:end]] == @views X[begin:end,2,Y[begin+1:end]]
    @test X[u...,begin+1:end] == @views X[u...,begin+1:end]
    @test X[(1,)...,(2,)...,2:end] == @views X[(1,)...,(2,)...,2:end]

    # @views for zero dimensional arrays
    A = Array{Int, 0}(undef)
    A[] = 2
    @test (@views A[]) == 2

    # test macro hygiene
    let size=(x,y)-> error("should not happen"), Base=nothing
        @test X[1:end,2,2] == @views X[1:end,2,2]
    end
end

@testset "issue #18034: an isbits, IndexLinear view of an immutable Array" begin
    struct ImmutableTestArray{T, N} <: Base.DenseArray{T, N}
    end
    Base.size(::Union{ImmutableTestArray, Type{ImmutableTestArray}}) = (0, 0)
    Base.IndexStyle(::Union{ImmutableTestArray, Type{ImmutableTestArray}}) = Base.IndexLinear()
    a = ImmutableTestArray{Float64, 2}()
    @test Base.IndexStyle(view(a, :, :)) == Base.IndexLinear()
    @test isbits(view(a, :, :))
end

@testset "inference; issue #17351, #25321" begin
    @test @inferred(reverse(view([1 2; 3 4], :, 1), dims=1)) == [3, 1]
    s = view(reshape(1:6, 2, 3), 1:2, 1:2)
    @test @inferred(s[2,2,1]) === 4

    A = rand(5,5,5,5)
    V = view(A, 1:1 ,:, 1:3, :)
    @test @inferred(strides(V)) == (1, 5, 25, 125)
end

@testset "issue #18581: slices with OneTo axes can be linear" begin
    A18581 = rand(5, 5)
    B18581 = view(A18581, :, axes(A18581,2))
    @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)
    a = UInt48(0x00000001);
    b = UInt48(0x00000002);
    c = UInt48(0x00000003);
    arrayOfUInt48 = [a, b, c];

    @test sizeof(view(arrayOfUInt48, 1:2)) == 16

    @test sizeof(view(Diagonal(zeros(UInt8, 10)), 1:4)) == 4
    @test sizeof(view(Diagonal(zeros(UInt8, 10)), 1:3)) == 3
    @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)

    seekstart(io)
    @test write(io, view(a, 2:5, 1:4)) == 4*4*8
    seekstart(io)
    v = Matrix{UInt48}(undef, 4, 4)
    read!(io, v)
    @test v == view(a, 2:5, 1:4)

    seekstart(io)
    @test write(io, view(a, 5:-1:1, 3)) == 5*8
    seekstart(io)
    v = Vector{UInt48}(undef, 5)
    read!(io, v)
    @test v == view(a, 5:-1:1, 3)

    seekstart(io)
    @test write(io, view(a, 1:2:5, :)) == 3*5*8
    seekstart(io)
    v = Matrix{UInt48}(undef, 3, 5)
    read!(io, v)
    @test v == view(a, 1:2:5, :)
end

@testset "unaliascopy trimming; Issue #26263" begin
    A = rand(5,5,5,5)
    V = view(A, 2:5, :, 2:5, 1:2:5)
    V′ = @inferred(Base.unaliascopy(V))
    @test size(V′.parent) == size(V)
    @test V′::typeof(V) == V == A[2:5, :, 2:5, 1:2:5]
    @test @inferred(sum(V′)) ≈ sum(V) ≈ sum(A[2:5, :, 2:5, 1:2:5])
    V = view(A, Base.IdentityUnitRange(2:4), :, Base.StepRangeLen(1,1,3), 1:2:5)
    V′ = @inferred(Base.unaliascopy(V))
    @test size(V.parent) != size(V′.parent)
    @test V′ == V && V′ isa typeof(V)
    i1 = collect(CartesianIndices((2:5)))
    i2 = [CartesianIndex(), CartesianIndex()]
    i3 = collect(CartesianIndices((2:5, 1:2:5)))
    V = view(A, i1, 1:5, i2, i3)
    @test @inferred(Base.unaliascopy(V))::typeof(V) == V == A[i1, 1:5, i2, i3]
    V = view(A, i1, 1:5, i3, i2)
    @test @inferred(Base.unaliascopy(V))::typeof(V) == V == A[i1, 1:5, i3, i2]

    @testset "custom ranges" begin
        struct MyStepRange{T} <: OrdinalRange{T,T}
            r::StepRange{T,T}
        end

        for f in (:first, :last, :step, :length, :size)
            @eval Base.$f(r::MyStepRange) = $f(r.r)
        end
        Base.getindex(r::MyStepRange, i::Int) = r.r[i]

        a = rand(6)
        V = view(a, MyStepRange(2:2:4))
        @test @inferred(Base.unaliascopy(V))::typeof(V) == V

        # empty range
        V = view(a, MyStepRange(2:2:1))
        @test @inferred(Base.unaliascopy(V))::typeof(V) == V
    end
end

@testset "issue #27632" begin
    function _test_27632(A)
        for J in CartesianIndices(size(A)[2:end])
            A[1, J]
        end
        nothing
    end
    # check that this doesn't crash
    @test _test_27632(view(ones(Int64, (1, 1, 1)), 1, 1, 1)) === nothing
end

@testset "issue #37199: 1-d views with offset range indices" begin
    b = zeros(6, 3)
    b[Base.IdentityUnitRange(4:6), 2] .= 3
    @test b == [zeros(6, 1) [0,0,0,3,3,3] zeros(6,1)]
    b[4, Base.IdentityUnitRange(2:3)] .= 4
    @test b == [zeros(6,1) [0,0,0,4,3,3] [0,0,0,4,0,0]]
    b[Base.IdentityUnitRange(2:3), :] .= 5
    @test b == [zeros(1, 3); fill(5, 2, 3); [zeros(3) [4,3,3] [4,0,0]]]
    b[:, Base.IdentityUnitRange(3:3)] .= 6
    @test b == [[zeros(1, 2); fill(5, 2, 2); [zeros(3) [4,3,3]]] fill(6, 6)]

    A = reshape(1:5*7*11, 11, 7, 5)
    inds = (1:4, 2:5, 2, :, fill(3))
    offset(x) = x
    offset(r::UnitRange) = Base.IdentityUnitRange(r)
    for i1 in inds
        for i2 in inds
            for i3 in inds
                vo = @view A[offset(i1), offset(i2), offset(i3)]
                v = @view A[i1, i2, i3]
                @test first(vo) == first(v) == first(A[i1, i2, i3])
                @test collect(A[i1, i2, i3]) == collect(vo) == collect(v)
            end
        end
    end
end

@testset "issue #29608; contiguousness" begin
    @test Base.iscontiguous(view(ones(1), 1))
    @test Base.iscontiguous(view(ones(10), 1:10))
    @test Base.iscontiguous(view(ones(10), :))
end

import InteractiveUtils
@testset "blas-enabled reshaped indices" begin
    p = rand(30)
    M = view(p, reshape(2:25, 6, 4))
    v = rand(4)
    @test M isa StridedArray
    @test M*v == copy(M)*v
    @test (InteractiveUtils.@which M*v) == (InteractiveUtils.@which copy(M)*v)
end


isdefined(Main, :InfiniteArrays) || @eval Main include("testhelpers/InfiniteArrays.jl")
using .Main.InfiniteArrays, Base64

@testset "PR #37741: non-Int sizes" begin
    r = BigInt(1):BigInt(100_000_000)^100
    v = SubArray(r, (r,))
    @test size(v) == (last(r),)

    v = SubArray(OneToInf(), (OneToInf(),))
    @test size(v) == (Infinity(),)
    @test stringmime("text/plain", v; context=(:limit => true)) == "$(Infinity())-element view(::$(OneToInf{Int}), 1:1:$(Infinity())) with eltype $Int with indices 1:1:$(Infinity()):\n  1\n  2\n  3\n  4\n  5\n  6\n  7\n  8\n  9\n 10\n  ⋮"
end

@testset "PR #39809: copy on 0-dimensional SubArray" begin
    v = [[1]]
    s = @view v[1]
    @test copy(s) == fill([1])
end

@testset "issue 40314: views of CartesianIndices" begin
    c = CartesianIndices((1:2, 1:4))
    @test (@view c[c]) === c
    for inds in Any[(1:1, 1:2), (1:1:1, 1:2)]
        c2 = @view c[inds...]
        @test c2 isa CartesianIndices{2}
        for i2 in inds[2], i1 in inds[1]
            @test c2[i1, i2] == c[i1, i2]
        end
    end
    for inds in Any[(Colon(), 1:2), (Colon(), 1:1:2)]
        c2 = @view c[inds...]
        @test c2 isa CartesianIndices{2}
        for i2 in inds[2], i1 in axes(c, 1)
            @test c2[i1, i2] == c[i1, i2]
        end
    end
end

@testset "issue #41221: view(::Vector, :, 1)" begin
    v = randn(3)
    @test @inferred(view(v,:,1)) == v
    @test parent(@inferred(view(v,:,1))) === v
    @test parent(@inferred(view(v,2:3,1,1))) === v
    @test_throws BoundsError view(v,:,2)
    @test_throws BoundsError view(v,:,1,2)

    m = randn(4,5).+im
    @test view(m, 1:2, 3, 1, 1) == m[1:2, 3]
    @test parent(view(m, 1:2, 3, 1, 1)) === m
end

@testset "issue #53209: avoid invalid elimination of singleton indices" begin
    A = randn(4,5)
    @test A[CartesianIndices(()), :, 3] == @inferred(view(A, CartesianIndices(()), :, 3))
    @test parent(@inferred(view(A, :, 3, 1, CartesianIndices(()), 1))) === A
    @test_throws BoundsError view(A, :, 3, 2, CartesianIndices(()), 1)
end

@testset "replace_in_print_matrix" begin
    struct MyIdentity <: AbstractMatrix{Bool}
        n :: Int
    end
    Base.size(M::MyIdentity) = (M.n, M.n)
    function Base.getindex(M::MyIdentity, i::Int, j::Int)
        checkbounds(M, i, j)
        i == j
    end
    function Base.replace_in_print_matrix(M::MyIdentity, i::Integer, j::Integer, s::AbstractString)
        i == j ? s : Base.replace_with_centered_mark(s)
    end
    V = view(MyIdentity(3), 1:2, 1:3)
    @test sprint(show, "text/plain", V) == "$(summary(V)):\n 1  ⋅  ⋅\n ⋅  1  ⋅"

    struct OneElVec <: AbstractVector{Bool}
        n :: Int
        ind :: Int
    end
    Base.size(M::OneElVec) = (M.n,)
    function Base.getindex(M::OneElVec, i::Int)
        checkbounds(M, i)
        i == M.ind
    end
    function Base.replace_in_print_matrix(M::OneElVec, i::Integer, j::Integer, s::AbstractString)
        i == M.ind ? s : Base.replace_with_centered_mark(s)
    end
    V = view(OneElVec(6, 2), 1:5)
    @test sprint(show, "text/plain", V) == "$(summary(V)):\n ⋅\n 1\n ⋅\n ⋅\n ⋅"

    V = view(1:2, [CartesianIndex(2)])
    @test sprint(show, "text/plain", V) == "$(summary(V)):\n 2"
end

@testset "Base.first_index for offset indices" begin
    a = Vector(1:10)
    b = view(a, Base.IdentityUnitRange(4:7))
    @test first(b) == a[Base.first_index(b)]
end

@testset "StepRangeLen of CartesianIndex-es" begin
    v = view(1:2, StepRangeLen(CartesianIndex(1,1), CartesianIndex(1,1), 0))
    @test isempty(v)
    r = StepRangeLen(CartesianIndex(1), CartesianIndex(1), 1)
    v = view(1:2, r)
    @test v == view(1:2, collect(r))
end

# https://github.com/JuliaLang/julia/pull/53064
# `@view(A[idx]) = xxx` should raise syntax error always
@test try
    Core.eval(@__MODULE__, :(@view(A[idx]) = 2))
    false
catch err
    err isa ErrorException && startswith(err.msg, "syntax:")
end
module Issue53064
import Base: view
end
@test try
    Core.eval(Issue53064, :(@view(A[idx]) = 2))
    false
catch err
    err isa ErrorException && startswith(err.msg, "syntax:")
end

@testset "isassigned" begin
    a = Vector{BigFloat}(undef, 5)
    a[2] = 0
    for v in (view(a, 2:3), # FastContiguousSubArray
               view(a, 2:2:4), # FastSubArray
               view(a, [2:2:4;]), # SlowSubArray
            )
        @test !isassigned(v, 0) # out-of-bounds
        @test isassigned(v, 1) # inbounds and assigned
        @test !isassigned(v, 2) # inbounds but not assigned
        @test !isassigned(v, 4) # out-of-bounds
    end

    a = Array{BigFloat}(undef,3,3,3)
    a[1,1,1] = 0
    for v in (view(a, :, 1:3, 1), # FastContiguousSubArray
               view(a, 1, :, 1:2), # FastSubArray
            )
        @test !isassigned(v, 0, 0) # out-of-bounds
        @test isassigned(v, 1, 1) # inbounds and assigned
        @test !isassigned(v, 1, 2) # inbounds but not assigned
        @test !isassigned(v, 3, 3) # out-of-bounds
    end
end

@testset "aliasing checks with shared indices" begin
    indices = [1,3]
    a = rand(3)
    av = @view a[indices]
    b = rand(3)
    bv = @view b[indices]
    @test !Base.mightalias(av, bv)
    @test Base.mightalias(a, av)
    @test Base.mightalias(b, bv)
    @test Base.mightalias(indices, av)
    @test Base.mightalias(indices, bv)
    @test Base.mightalias(view(indices, :), av)
    @test Base.mightalias(view(indices, :), bv)
end

@testset "aliasing checks with disjoint arrays" begin
    A = rand(3,4,5)
    @test Base.mightalias(view(A, :, :, 1), view(A, :, :, 1))
    @test !Base.mightalias(view(A, :, :, 1), view(A, :, :, 2))

    B = reinterpret(UInt64, A)
    @test Base.mightalias(view(B, :, :, 1), view(A, :, :, 1))
    @test !Base.mightalias(view(B, :, :, 1), view(A, :, :, 2))

    C = reinterpret(UInt32, A)
    @test Base.mightalias(view(C, :, :, 1), view(A, :, :, 1))
    @test Base.mightalias(view(C, :, :, 1), view(A, :, :, 2)) # This is overly conservative
    @test Base.mightalias(@view(C[begin:2:end, :, 1]), view(A, :, :, 1))
    @test Base.mightalias(@view(C[begin:2:end, :, 1]), view(A, :, :, 2)) # This is overly conservative
end

@testset "aliasing check with reshaped subarrays" begin
    C = rand(2,1)
    V1 = @view C[1, :]
    V2 = @view C[2, :]

    @test !Base.mightalias(V1, V2)
    @test !Base.mightalias(V1, permutedims(V2))
    @test !Base.mightalias(permutedims(V1), V2)
    @test !Base.mightalias(permutedims(V1), permutedims(V2))

    @test Base.mightalias(V1, V1)
    @test Base.mightalias(V1, permutedims(V1))
    @test Base.mightalias(permutedims(V1), V1)
    @test Base.mightalias(permutedims(V1), permutedims(V1))
end


@test @views quote var"begin" + var"end" end isa Expr

@testset "@views handling of assignment" begin
    @test @macroexpand(@views x[a:b] = c) == :(x[a:b] = c)
    # Assignments should still work
    let array = [1, 2, 3, 4, 5, 6, 7, 8]
        @views array[begin:2] = [-1, -2]
        @test array == [-1, -2, 3, 4, 5, 6, 7, 8]
        @views array[7:end] = [-7, -8]
        @test array == [-1, -2, 3, 4, 5, 6, -7, -8]
        @views array[begin + 2:end - 4] = [-3, -4]
        @test array == [-1, -2, -3, -4, 5, 6, -7, -8]
        @views identity(array)[begin + 4:end - 2] = [-5, -6]
        @test array == [-1, -2, -3, -4, -5, -6, -7, -8]

        @views array[begin:2] .= 100
        @test array == [100, 100, -3, -4, -5, -6, -7, -8]
        @views array[7:end] .= 200
        @test array == [100, 100, -3, -4, -5, -6, 200, 200]
        @views array[begin + 2:end - 4] .= 300
        @test array == [100, 100, 300, 300, -5, -6, 200, 200]
        @views identity(array)[begin + 4:end - 2] .= 400
        @test array == [100, 100, 300, 300, 400, 400, 200, 200]

        @views identity(array)[begin:end] .-= 1
        @test array == [99, 99, 299, 299, 399, 399, 199, 199]

        @views identity(array)[begin:end] += [1, 2, 3, 4, 5, 6, 7, 8]
        @test array == [100, 101, 302, 303, 404, 405, 206, 207]
    end
    # Nested getindex in assignment should be transformed
    let array = [1, 2, 3, 4, 5, 6, 7, 8], array2 = [1, 2, 3, 4, 5, 6, 7, 8]
        array[begin + 1:end - 2][2] = -1
        array[begin + 1:end - 2][end] = -2
        @test array == [1, 2, 3, 4, 5, 6, 7, 8]

        @views array[begin + 1:end - 2][2] = -1
        @views array[begin + 1:end - 2][end] = -2
        @test array == [1, 2, -1, 4, 5, -2, 7, 8]

        function swap_ele(ary, i, v)
            res = ary[i]
            ary[i] = v
            return res
        end
        array2[swap_ele(array[begin:end], 1, -3):swap_ele(array[begin:end], 7, -4)] = [-1, -2, -3, -4, -5, -6, -7]
        @test array == [1, 2, -1, 4, 5, -2, 7, 8]
        @test array2 == [-1, -2, -3, -4, -5, -6, -7, 8]
        @views array2[swap_ele(array[begin:end], 1, -3):swap_ele(array[begin:end], 7, -4)] = [-10, 2, -30, 4, -50, 6, -70]
        @test array == [-3, 2, -1, 4, 5, -2, -4, 8]
        @test array2 == [-10, 2, -30, 4, -50, 6, -70, 8]
    end
end