Introduce a whole new IdentityUnitRange

that we will encourage offset array implementations to use instead of Base.Slice

base/abstractarray.jl

@@ -505,7 +505,7 @@ checkindex(::Type{Bool}, inds::AbstractUnitRange, i) =
  throw(ArgumentError("unable to check bounds for indices of type $(typeof(i))"))
 checkindex(::Type{Bool}, inds::AbstractUnitRange, i::Real) = (first(inds) <= i) & (i <= last(inds))
 checkindex(::Type{Bool}, inds::AbstractUnitRange, ::Colon) = true
-checkindex(::Type{Bool}, inds::AbstractUnitRange, ::WholeSlice) = true
+checkindex(::Type{Bool}, inds::AbstractUnitRange, ::Slice) = true
 function checkindex(::Type{Bool}, inds::AbstractUnitRange, r::AbstractRange)
  @_propagate_inbounds_meta
  isempty(r) | (checkindex(Bool, inds, first(r)) & checkindex(Bool, inds, last(r)))
@@ -1739,7 +1739,7 @@ end
 
 nextL(L, l::Integer) = L*l
 nextL(L, r::AbstractUnitRange) = L*unsafe_length(r)
-nextL(L, r::WholeSlice) = L*unsafe_length(r.indices)
+nextL(L, r::Slice) = L*unsafe_length(r.indices)
 offsetin(i, l::Integer) = i-1
 offsetin(i, r::AbstractUnitRange) = i-first(r)
 
@@ -1901,7 +1901,7 @@ function mapslices(f, A::AbstractArray; dims)
  idx = Any[first(ind) for ind in axes(A)]
  itershape = tuple(dimsA[otherdims]...)
  for d in dims
- idx[d] = WholeSlice(axes(A, d))
+ idx[d] = Slice(axes(A, d))
  end
 
  # Apply the function to the first slice in order to determine the next steps

base/abstractarraymath.jl

@@ -120,7 +120,7 @@ julia> selectdim(A, 2, 3)
  7
 ```
 """
-@inline selectdim(A::AbstractArray, d::Integer, i) = _selectdim(A, d, i, setindex(map(WholeSlice, axes(A)), i, d))
+@inline selectdim(A::AbstractArray, d::Integer, i) = _selectdim(A, d, i, setindex(map(Slice, axes(A)), i, d))
 @noinline function _selectdim(A, d, i, idxs)
  d >= 1 || throw(ArgumentError("dimension must be ≥ 1"))
  nd = ndims(A)

base/indices.jl

@@ -298,29 +298,22 @@ _maybetail(t::Tuple) = tail(t)
 """
  Slice(indices)
 
-Represent an AbstractUnitRange of indices as a vector of the indices themselves.
+Represent an AbstractUnitRange of indices as a vector of the indices themselves,
+with special handling to signal they represent a complete slice of a dimension (:).
 
 Upon calling `to_indices`, Colons are converted to Slice objects to represent
 the indices over which the Colon spans. Slice objects are themselves unit
 ranges with the same indices as those they wrap. This means that indexing into
 Slice objects with an integer always returns that exact integer, and they
 iterate over all the wrapped indices, even supporting offset indices.
 """
-struct Slice{T<:AbstractUnitRange, wholedim} <: AbstractUnitRange{Int}
+struct Slice{T<:AbstractUnitRange} <: AbstractUnitRange{Int}
  indices::T
 end
-Slice(r::AbstractUnitRange) = Slice{typeof(r), false}(r)
-Slice(S::Slice) = Slice{typeof(S.indices), false}(S.indices)
-Slice(S::Slice{<:Any, false}) = S
-const WholeSlice{T} = Slice{T, true}
-WholeSlice(r::AbstractUnitRange) = Slice{typeof(r), true}(r)
-WholeSlice(S::Slice) = Slice{typeof(S.indices), true}(S.indices)
-WholeSlice(S::WholeSlice) = S
-# Slices are offset and thus have offset axes, so they are their own axes... but
-# we need to strip the wholedim marker because we don't know how they'll be used
-axes(S::Slice) = (Slice(S),)
-unsafe_indices(S::Slice) = (Slice(S),)
-axes1(S::Slice) = Slice(S)
+Slice(S::Slice) = S
+axes(S::Slice) = (IdentityUnitRange(S.indices),)
+unsafe_indices(S::Slice) = (IdentityUnitRange(S.indices),)
+axes1(S::Slice) = IdentityUnitRange(S.indices)
 axes(S::Slice{<:OneTo}) = (S.indices,)
 unsafe_indices(S::Slice{<:OneTo}) = (S.indices,)
 axes1(S::Slice{<:OneTo}) = S.indices
@@ -336,6 +329,38 @@ getindex(S::Slice, i::StepRange{<:Integer}) = (@_inline_meta; @boundscheck check
 show(io::IO, r::Slice) = print(io, "Base.Slice(", r.indices, ")")
 iterate(S::Slice, s...) = iterate(S.indices, s...)
 
+
+"""
+ IdentityUnitRange(range::AbstractUnitRange)
+
+Represent an AbstractUnitRange `range` as an offset vector such that `range[i] == i`.
+
+`IdentityUnitRange`s are frequently used as axes for offset arrays.
+"""
+struct IdentityUnitRange{T<:AbstractUnitRange} <: AbstractUnitRange{Int}
+ indices::T
+end
+IdentityUnitRange(S::IdentityUnitRange) = S
+# IdentityUnitRanges are offset and thus have offset axes, so they are their own axes... but
+# we need to strip the wholedim marker because we don't know how they'll be used
+axes(S::IdentityUnitRange) = (S,)
+unsafe_indices(S::IdentityUnitRange) = (S,)
+axes1(S::IdentityUnitRange) = S
+axes(S::IdentityUnitRange{<:OneTo}) = (S.indices,)
+unsafe_indices(S::IdentityUnitRange{<:OneTo}) = (S.indices,)
+axes1(S::IdentityUnitRange{<:OneTo}) = S.indices
+
+first(S::IdentityUnitRange) = first(S.indices)
+last(S::IdentityUnitRange) = last(S.indices)
+size(S::IdentityUnitRange) = (length(S.indices),)
+length(S::IdentityUnitRange) = length(S.indices)
+unsafe_length(S::IdentityUnitRange) = unsafe_length(S.indices)
+getindex(S::IdentityUnitRange, i::Int) = (@_inline_meta; @boundscheck checkbounds(S, i); i)
+getindex(S::IdentityUnitRange, i::AbstractUnitRange{<:Integer}) = (@_inline_meta; @boundscheck checkbounds(S, i); i)
+getindex(S::IdentityUnitRange, i::StepRange{<:Integer}) = (@_inline_meta; @boundscheck checkbounds(S, i); i)
+show(io::IO, r::IdentityUnitRange) = print(io, "Base.IdentityUnitRange(", r.indices, ")")
+iterate(S::IdentityUnitRange, s...) = iterate(S.indices, s...)
+
 """
  LinearIndices(A::AbstractArray)
 

base/multidimensional.jl

@@ -573,8 +573,8 @@ _maybe_linear_logical_index(::IndexLinear, A, i) = LogicalIndex{Int}(i)
  (uncolon(inds, I), to_indices(A, _maybetail(inds), tail(I))...)
 
 const CI0 = Union{CartesianIndex{0}, AbstractArray{CartesianIndex{0}}}
-uncolon(inds::Tuple{}, I::Tuple{Colon, Vararg{Any}}) = WholeSlice(OneTo(1))
-uncolon(inds::Tuple, I::Tuple{Colon, Vararg{Any}}) = WholeSlice(inds[1])
+uncolon(inds::Tuple{}, I::Tuple{Colon, Vararg{Any}}) = Slice(OneTo(1))
+uncolon(inds::Tuple, I::Tuple{Colon, Vararg{Any}}) = Slice(inds[1])
 
 ### From abstractarray.jl: Internal multidimensional indexing definitions ###
 getindex(x::Number, i::CartesianIndex{0}) = x

base/reducedim.jl

@@ -4,7 +4,7 @@
 
 # for reductions that expand 0 dims to 1
 reduced_index(i::OneTo) = OneTo(1)
-reduced_index(i::Slice) = first(i):first(i)
+reduced_index(i::Union{Slice, IdentityUnitRange}) = first(i):first(i)
 reduced_index(i::AbstractUnitRange) =
  throw(ArgumentError(
 """

base/show.jl

@@ -1818,7 +1818,7 @@ dims2string(d) = isempty(d) ? "0-dimensional" :
 
 inds2string(inds) = join(map(_indsstring,inds), '×')
 _indsstring(i) = string(i)
-_indsstring(i::Slice) = string(i.indices)
+_indsstring(i::Union{IdentityUnitRange, Slice}) = string(i.indices)
 
 # anything array-like gets summarized e.g. 10-element Array{Int64,1}
 summary(io::IO, a::AbstractArray) = summary(io, a, axes(a))
@@ -1893,7 +1893,7 @@ function showarg(io::IO, v::SubArray, toplevel)
  print(io, ')')
  toplevel && print(io, " with eltype ", eltype(v))
 end
-showindices(io, ::Slice, inds...) =
+showindices(io, ::Union{Slice,IdentityUnitRange}, inds...) =
  (print(io, ", :"); showindices(io, inds...))
 showindices(io, ind1, inds...) =
  (print(io, ", ", ind1); showindices(io, inds...))

base/sort.jl

@@ -19,7 +19,6 @@ import .Base:
  sort!,
  issorted,
  sortperm,
- Slice,
  to_indices
 
 export # also exported by Base

base/subarray.jl

@@ -42,10 +42,10 @@ viewindexing() = IndexLinear()
 # Leading scalar indices simply increase the stride
 viewindexing(I::Tuple{ScalarIndex, Vararg{Any}}) = (@_inline_meta; viewindexing(tail(I)))
 # Slices may begin a section which may be followed by any number of Slices
-viewindexing(I::Tuple{WholeSlice, WholeSlice, Vararg{Any}}) = (@_inline_meta; viewindexing(tail(I)))
-# A UnitRange can follow WholeSlices, but only if all other indices are scalar
-viewindexing(I::Tuple{WholeSlice, AbstractUnitRange, Vararg{ScalarIndex}}) = IndexLinear()
-viewindexing(I::Tuple{WholeSlice, WholeSlice, Vararg{ScalarIndex}}) = IndexLinear() # disambiguate
+viewindexing(I::Tuple{Slice, Slice, Vararg{Any}}) = (@_inline_meta; viewindexing(tail(I)))
+# A UnitRange can follow Slices, but only if all other indices are scalar
+viewindexing(I::Tuple{Slice, AbstractUnitRange, Vararg{ScalarIndex}}) = IndexLinear()
+viewindexing(I::Tuple{Slice, Slice, Vararg{ScalarIndex}}) = IndexLinear() # disambiguate
 # In general, ranges are only fast if all other indices are scalar
 viewindexing(I::Tuple{AbstractRange, Vararg{ScalarIndex}}) = IndexLinear()
 # All other index combinations are slow
@@ -190,7 +190,7 @@ reindex(V, idxs::Tuple{ScalarIndex, Vararg{Any}}, subidxs::Tuple{Vararg{Any}}) =
  (@_propagate_inbounds_meta; (idxs[1], reindex(V, tail(idxs), subidxs)...))
 
 # Slices simply pass their subindices straight through
-reindex(V, idxs::Tuple{WholeSlice, Vararg{Any}}, subidxs::Tuple{Any, Vararg{Any}}) =
+reindex(V, idxs::Tuple{Slice, Vararg{Any}}, subidxs::Tuple{Any, Vararg{Any}}) =
  (@_propagate_inbounds_meta; (subidxs[1], reindex(V, tail(idxs), tail(subidxs))...))
 
 # Re-index into parent vectors with one subindex
@@ -229,7 +229,7 @@ function getindex(V::FastSubArray, i::Int)
  r
 end
 # We can avoid a multiplication if the first parent index is a Colon or AbstractUnitRange
-FastContiguousSubArray{T,N,P,I<:Tuple{Union{WholeSlice, AbstractUnitRange}, Vararg{Any}}} = SubArray{T,N,P,I,true}
+FastContiguousSubArray{T,N,P,I<:Tuple{Union{Slice, AbstractUnitRange}, Vararg{Any}}} = SubArray{T,N,P,I,true}
 function getindex(V::FastContiguousSubArray, i::Int)
  @_inline_meta
  @boundscheck checkbounds(V, i)
@@ -266,7 +266,7 @@ strides(V::SubArray) = substrides(V.parent, V.indices)
 substrides(parent, I::Tuple) = substrides(parent, strides(parent), I)
 substrides(parent, strds::Tuple{}, ::Tuple{}) = ()
 substrides(parent, strds::NTuple{N,Int}, I::Tuple{ScalarIndex, Vararg{Any}}) where N = (substrides(parent, tail(strds), tail(I))...,)
-substrides(parent, strds::NTuple{N,Int}, I::Tuple{WholeSlice, Vararg{Any}}) where N = (first(strds), substrides(parent, tail(strds), tail(I))...)
+substrides(parent, strds::NTuple{N,Int}, I::Tuple{Slice, Vararg{Any}}) where N = (first(strds), substrides(parent, tail(strds), tail(I))...)
 substrides(parent, strds::NTuple{N,Int}, I::Tuple{AbstractRange, Vararg{Any}}) where N = (first(strds)*step(I[1]), substrides(parent, tail(strds), tail(I))...)
 substrides(parent, strds, I::Tuple{Any, Vararg{Any}}) = throw(ArgumentError("strides is invalid for SubArrays with indices of type $(typeof(I[1]))"))
 
@@ -278,7 +278,7 @@ compute_stride1(s, inds, I::Tuple{}) = s
 compute_stride1(s, inds, I::Tuple{ScalarIndex, Vararg{Any}}) =
  (@_inline_meta; compute_stride1(s*unsafe_length(inds[1]), tail(inds), tail(I)))
 compute_stride1(s, inds, I::Tuple{AbstractRange, Vararg{Any}}) = s*step(I[1])
-compute_stride1(s, inds, I::Tuple{WholeSlice, Vararg{Any}}) = s
+compute_stride1(s, inds, I::Tuple{Slice, Vararg{Any}}) = s
 compute_stride1(s, inds, I::Tuple{Any, Vararg{Any}}) = throw(ArgumentError("invalid strided index type $(typeof(I[1]))"))
 
 elsize(::Type{<:SubArray{<:Any,<:Any,P}}) where {P} = elsize(P)
@@ -305,7 +305,7 @@ compute_offset1(parent::AbstractVector, stride1::Integer, I::Tuple{AbstractRange
 # linear indexing always starts with 1.
 compute_offset1(parent, stride1::Integer, I::Tuple) =
  (@_inline_meta; compute_offset1(parent, stride1, find_extended_dims(1, I...), find_extended_inds(I...), I))
-compute_offset1(parent, stride1::Integer, dims::Tuple{Int}, inds::Tuple{Slice}, I::Tuple) =
+compute_offset1(parent, stride1::Integer, dims::Tuple{Int}, inds::Tuple{Union{Slice, IdentityUnitRange}}, I::Tuple) =
  (@_inline_meta; compute_linindex(parent, I) - stride1*first(axes(parent, dims[1]))) # index-preserving case
 compute_offset1(parent, stride1::Integer, dims, inds, I::Tuple) =
  (@_inline_meta; compute_linindex(parent, I) - stride1) # linear indexing starts with 1

stdlib/LinearAlgebra/test/adjtrans.jl

@@ -489,7 +489,7 @@ using .Main.OffsetArrays
 
 @testset "offset axes" begin
  s = Base.Slice(-3:3)'
- @test axes(s) === (Base.OneTo(1), Base.Slice(-3:3))
+ @test axes(s) === (Base.OneTo(1), Base.IdentityUnitRange(-3:3))
  @test collect(LinearIndices(s)) == reshape(1:7, 1, 7)
  @test collect(CartesianIndices(s)) == reshape([CartesianIndex(1,i) for i = -3:3], 1, 7)
  @test s[1] == -3

stdlib/SparseArrays/src/sparsematrix.jl

@@ -42,7 +42,7 @@ size(S::SparseMatrixCSC) = (S.m, S.n)
 # underlying SparseMatrixCSC
 const SparseMatrixCSCView{Tv,Ti} =
  SubArray{Tv,2,SparseMatrixCSC{Tv,Ti},
- Tuple{Base.Slice{Base.OneTo{Int},true},I}} where {I<:AbstractUnitRange}
+ Tuple{Base.Slice{Base.OneTo{Int}},I}} where {I<:AbstractUnitRange}
 const SparseMatrixCSCUnion{Tv,Ti} = Union{SparseMatrixCSC{Tv,Ti}, SparseMatrixCSCView{Tv,Ti}}
 
 getcolptr(S::SparseMatrixCSC) = S.colptr

stdlib/SparseArrays/src/sparsevector.jl

@@ -32,7 +32,7 @@ SparseVector(n::Integer, nzind::Vector{Ti}, nzval::Vector{Tv}) where {Tv,Ti} =
 
 # Define an alias for a view of a whole column of a SparseMatrixCSC. Many methods can be written for the
 # union of such a view and a SparseVector so we define an alias for such a union as well
-const SparseColumnView{T} = SubArray{T,1,<:SparseMatrixCSC,Tuple{Base.Slice{Base.OneTo{Int},true},Int},false}
+const SparseColumnView{T} = SubArray{T,1,<:SparseMatrixCSC,Tuple{Base.Slice{Base.OneTo{Int}},Int},false}
 const SparseVectorUnion{T} = Union{SparseVector{T}, SparseColumnView{T}}
 
 ### Basic properties

test/arrayops.jl

@@ -1729,7 +1729,7 @@ end
  @test a[1,2] == 7
  @test 2*CartesianIndex{3}(1,2,3) == CartesianIndex{3}(2,4,6)
 
- R = CartesianIndices(map(Base.Slice, (2:5, 3:5)))
+ R = CartesianIndices(map(Base.IdentityUnitRange, (2:5, 3:5)))
  @test eltype(R) <: CartesianIndex{2}
  @test eltype(typeof(R)) <: CartesianIndex{2}
  @test eltype(CartesianIndices{2}) <: CartesianIndex{2}

test/offsetarray.jl

@@ -81,7 +81,7 @@ for i = 1:9 @test A_3_3[i] == i end
 @test_throws BoundsError A[CartesianIndex(1,1)]
 @test_throws BoundsError S[CartesianIndex(1,1)]
 @test eachindex(A) == 1:4
-@test eachindex(S) == CartesianIndices(axes(S)) == CartesianIndices(map(Base.Slice, (0:1,3:4)))
+@test eachindex(S) == CartesianIndices(axes(S)) == CartesianIndices(map(Base.IdentityUnitRange, (0:1,3:4)))
 
 # LinearIndices
 # issue 27986
@@ -122,13 +122,13 @@ S = view(A, :, 3)
 @test S[0] == 1
 @test S[1] == 2
 @test_throws BoundsError S[2]
-@test axes(S) === (Base.Slice(0:1),)
+@test axes(S) === (Base.IdentityUnitRange(0:1),)
 S = view(A, 0, :)
 @test S == OffsetArray([1,3], (A.offsets[2],))
 @test S[3] == 1
 @test S[4] == 3
 @test_throws BoundsError S[1]
-@test axes(S) === (Base.Slice(3:4),)
+@test axes(S) === (Base.IdentityUnitRange(3:4),)
 S = view(A, 0:0, 4)
 @test S == [3]
 @test S[1] == 3
@@ -147,17 +147,17 @@ S = view(A, :, :)
 @test S[0,4] == S[3] == 3
 @test S[1,4] == S[4] == 4
 @test_throws BoundsError S[1,1]
-@test axes(S) === Base.Slice.((0:1, 3:4))
+@test axes(S) === Base.IdentityUnitRange.((0:1, 3:4))
 # https://github.com/JuliaArrays/OffsetArrays.jl/issues/27
 g = OffsetArray(Vector(-2:3), (-3,))
 gv = view(g, -1:2)
 @test axes(gv, 1) === Base.OneTo(4)
 @test collect(gv) == -1:2
 gv = view(g, OffsetArray(-1:2, (-2,)))
-@test axes(gv, 1) === Base.Slice(-1:2)
+@test axes(gv, 1) === Base.IdentityUnitRange(-1:2)
 @test collect(gv) == -1:2
 gv = view(g, OffsetArray(-1:2, (-1,)))
-@test axes(gv, 1) === Base.Slice(0:3)
+@test axes(gv, 1) === Base.IdentityUnitRange(0:3)
 @test collect(gv) == -1:2
 
 # iteration
@@ -234,26 +234,26 @@ B = similar(A, (3,4))
 @test axes(B) === (Base.OneTo(3), Base.OneTo(4))
 B = similar(A, (-3:3,1:4))
 @test isa(B, OffsetArray{Int,2})
-@test axes(B) === Base.Slice.((-3:3, 1:4))
+@test axes(B) === Base.IdentityUnitRange.((-3:3, 1:4))
 B = similar(parent(A), (-3:3,1:4))
 @test isa(B, OffsetArray{Int,2})
-@test axes(B) === Base.Slice.((-3:3, 1:4))
+@test axes(B) === Base.IdentityUnitRange.((-3:3, 1:4))
 
 # Indexing with OffsetArray indices
 i1 = OffsetArray([2,1], (-5,))
 i1 = OffsetArray([2,1], -5)
 b = A0[i1, 1]
-@test axes(b) === (Base.Slice(-4:-3),)
+@test axes(b) === (Base.IdentityUnitRange(-4:-3),)
 @test b[-4] == 2
 @test b[-3] == 1
 b = A0[1,i1]
-@test axes(b) === (Base.Slice(-4:-3),)
+@test axes(b) === (Base.IdentityUnitRange(-4:-3),)
 @test b[-4] == 3
 @test b[-3] == 1
 v = view(A0, i1, 1)
-@test axes(v) === (Base.Slice(-4:-3),)
+@test axes(v) === (Base.IdentityUnitRange(-4:-3),)
 v = view(A0, 1:1, i1)
-@test axes(v) === (Base.OneTo(1), Base.Slice(-4:-3))
+@test axes(v) === (Base.OneTo(1), Base.IdentityUnitRange(-4:-3))
 
 # copyto! and fill!
 a = OffsetArray{Int}(undef, (-3:-1,))
@@ -340,7 +340,7 @@ a = OffsetArray(a0, (-1,2,3,4,5))
 v = OffsetArray(v0, (-3,))
 @test lastindex(v) == 1
 @test v ≈ v
-@test axes(v') === (Base.OneTo(1),Base.Slice(-2:1))
+@test axes(v') === (Base.OneTo(1),Base.IdentityUnitRange(-2:1))
 @test parent(v) == collect(v)
 rv = reverse(v)
 @test axes(rv) == axes(v)
@@ -356,7 +356,7 @@ A = OffsetArray(rand(4,4), (-3,5))
 @test lastindex(A, 1) == 1
 @test lastindex(A, 2) == 9
 @test A ≈ A
-@test axes(A') === Base.Slice.((6:9, -2:1))
+@test axes(A') === Base.IdentityUnitRange.((6:9, -2:1))
 @test parent(copy(A')) == copy(parent(A)')
 @test collect(A) == parent(A)
 @test maximum(A) == maximum(parent(A))

test/reinterpretarray.jl

@@ -136,7 +136,7 @@ let a = [0.1 0.2; 0.3 0.4], at = reshape([(i,i+1) for i = 1:2:8], 2, 2)
  @test r[1,2] === reinterpret(Int64, v[1,2])
  @test r[0,3] === reinterpret(Int64, v[0,3])
  @test r[1,3] === reinterpret(Int64, v[1,3])
- @test_throws ArgumentError("cannot reinterpret a `Float64` array to `UInt32` when the first axis is Base.Slice(0:1). Try reshaping first.") reinterpret(UInt32, v)
+ @test_throws ArgumentError("cannot reinterpret a `Float64` array to `UInt32` when the first axis is Base.IdentityUnitRange(0:1). Try reshaping first.") reinterpret(UInt32, v)
  v = OffsetArray(a, (0, 1))
  r = reinterpret(UInt32, v)
  axsv = axes(v)
@@ -155,7 +155,7 @@ let a = [0.1 0.2; 0.3 0.4], at = reshape([(i,i+1) for i = 1:2:8], 2, 2)
  offsetvt = (-2, 4)
  vt = OffsetArray(at, offsetvt)
  istr = string(Int)
- @test_throws ArgumentError("cannot reinterpret a `Tuple{$istr,$istr}` array to `$istr` when the first axis is Base.Slice(-1:0). Try reshaping first.") reinterpret(Int, vt)
+ @test_throws ArgumentError("cannot reinterpret a `Tuple{$istr,$istr}` array to `$istr` when the first axis is Base.IdentityUnitRange(-1:0). Try reshaping first.") reinterpret(Int, vt)
  vt = reshape(vt, 1:1, axes(vt)...)
  r = reinterpret(Int, vt)
  @test r == OffsetArray(reshape(1:8, 2, 2, 2), (0, offsetvt...))

test/testhelpers/OffsetArrays.jl

@@ -39,13 +39,13 @@ Base.eachindex(::IndexLinear, A::OffsetVector) = axes(A, 1)
 # Implementations of indices and axes1. Since bounds-checking is
 # performance-critical and relies on indices, these are usually worth
 # optimizing thoroughly.
-@inline Base.axes(A::OffsetArray, d) = 1 <= d <= length(A.offsets) ? Base.Slice(axes(parent(A))[d] .+ A.offsets[d]) : Base.Slice(1:1)
+@inline Base.axes(A::OffsetArray, d) = 1 <= d <= length(A.offsets) ? Base.IdentityUnitRange(axes(parent(A))[d] .+ A.offsets[d]) : Base.IdentityUnitRange(1:1)
 @inline Base.axes(A::OffsetArray) = _indices(axes(parent(A)), A.offsets) # would rather use ntuple, but see #15276
-@inline _indices(inds, offsets) = (Base.Slice(inds[1] .+ offsets[1]), _indices(tail(inds), tail(offsets))...)
+@inline _indices(inds, offsets) = (Base.IdentityUnitRange(inds[1] .+ offsets[1]), _indices(tail(inds), tail(offsets))...)
 _indices(::Tuple{}, ::Tuple{}) = ()
-Base.axes1(A::OffsetArray{T,0}) where {T} = Base.Slice(1:1) # we only need to specialize this one
+Base.axes1(A::OffsetArray{T,0}) where {T} = Base.IdentityUnitRange(1:1) # we only need to specialize this one
 
-const OffsetAxis = Union{Integer, UnitRange, Base.Slice{<:UnitRange}, Base.OneTo}
+const OffsetAxis = Union{Integer, UnitRange, Base.IdentityUnitRange{<:UnitRange}, Base.OneTo}
 function Base.similar(A::OffsetArray, T::Type, dims::Dims)
  B = similar(parent(A), T, dims)
 end