Deprecate linearindices in favor of LinearIndices

LinearIndices is strictly more powerful than linearindices: these two functions
return arrays holding the same elements, but the former also preserves the shape
and indices of the original array.

Also improve docstrings.

NEWS.md

@@ -624,8 +624,10 @@ Library improvements
       other containers, by taking the multiplicity of the arguments into account.
       Use `unique` to get the old behavior.
 
-  * The type `LinearIndices` has been added, providing conversion from
-    cartesian indices to linear indices using the normal indexing operation. ([#24715])
+  * The `linearindices` function has been deprecated in favor of the new
+    `LinearIndices` type, which additionnally provides conversion from
+    cartesian indices to linear indices using the normal indexing operation.
+    ([#24715], [#26775]).
 
   * `IdDict{K,V}` replaces `ObjectIdDict`.  It has type parameters
     like other `AbstractDict` subtypes and its constructors mirror the
@@ -1446,4 +1448,5 @@ Command-line option changes
 [#26436]: https://github.com/JuliaLang/julia/issues/26436
 [#26442]: https://github.com/JuliaLang/julia/issues/26442
 [#26600]: https://github.com/JuliaLang/julia/issues/26600
-[#26670]: https://github.com/JuliaLang/julia/issues/26670
+[#26670]: https://github.com/JuliaLang/julia/issues/26670
+[#26775]: https://github.com/JuliaLang/julia/issues/26775

base/abstractarray.jl

@@ -96,33 +96,8 @@ indices1(iter) = OneTo(length(iter))
 unsafe_indices(A) = axes(A)
 unsafe_indices(r::AbstractRange) = (OneTo(unsafe_length(r)),) # Ranges use checked_sub for size
 
-"""
-    linearindices(A)
-
-Return a `UnitRange` specifying the valid range of indices for `A[i]`
-where `i` is an `Int`. For arrays with conventional indexing (indices
-start at 1), or any multidimensional array, this is `1:length(A)`;
-however, for one-dimensional arrays with unconventional indices, this
-is `axes(A, 1)`.
-
-Calling this function is the "safe" way to write algorithms that
-exploit linear indexing.
-
-# Examples
-```jldoctest
-julia> A = fill(1, (5,6,7));
-
-julia> b = linearindices(A);
-
-julia> extrema(b)
-(1, 210)
-```
-"""
-linearindices(A::AbstractArray) = (@_inline_meta; OneTo(_length(A)))
-linearindices(A::AbstractVector) = (@_inline_meta; indices1(A))
-
 keys(a::AbstractArray) = CartesianIndices(axes(a))
-keys(a::AbstractVector) = linearindices(a)
+keys(a::AbstractVector) = LinearIndices(a)
 
 prevind(::AbstractArray, i::Integer) = Int(i)-1
 nextind(::AbstractArray, i::Integer) = Int(i)+1
@@ -187,7 +162,7 @@ julia> lastindex(rand(3,4,5), 2)
 4
 ```
 """
-lastindex(a::AbstractArray) = (@_inline_meta; last(linearindices(a)))
+lastindex(a::AbstractArray) = (@_inline_meta; last(LinearIndices(a)))
 lastindex(a::AbstractArray, d) = (@_inline_meta; last(axes(a, d)))
 
 """
@@ -205,7 +180,7 @@ julia> firstindex(rand(3,4,5), 2)
 1
 ```
 """
-firstindex(a::AbstractArray) = (@_inline_meta; first(linearindices(a)))
+firstindex(a::AbstractArray) = (@_inline_meta; first(LinearIndices(a)))
 firstindex(a::AbstractArray, d) = (@_inline_meta; first(axes(a, d)))
 
 first(a::AbstractArray) = a[first(eachindex(a))]
@@ -321,49 +296,6 @@ function trailingsize(inds::Indices)
     prod(map(unsafe_length, inds))
 end
 
-## Traits for array types ##
-
-abstract type IndexStyle end
-struct IndexLinear <: IndexStyle end
-struct IndexCartesian <: IndexStyle end
-
-"""
-    IndexStyle(A)
-    IndexStyle(typeof(A))
-
-`IndexStyle` specifies the "native indexing style" for array `A`. When
-you define a new `AbstractArray` type, you can choose to implement
-either linear indexing or cartesian indexing.  If you decide to
-implement linear indexing, then you must set this trait for your array
-type:
-
-    Base.IndexStyle(::Type{<:MyArray}) = IndexLinear()
-
-The default is `IndexCartesian()`.
-
-Julia's internal indexing machinery will automatically (and invisibly)
-convert all indexing operations into the preferred style. This allows users
-to access elements of your array using any indexing style, even when explicit
-methods have not been provided.
-
-If you define both styles of indexing for your `AbstractArray`, this
-trait can be used to select the most performant indexing style. Some
-methods check this trait on their inputs, and dispatch to different
-algorithms depending on the most efficient access pattern. In
-particular, [`eachindex`](@ref) creates an iterator whose type depends
-on the setting of this trait.
-"""
-IndexStyle(A::AbstractArray) = IndexStyle(typeof(A))
-IndexStyle(::Type{Union{}}) = IndexLinear()
-IndexStyle(::Type{<:AbstractArray}) = IndexCartesian()
-IndexStyle(::Type{<:Array}) = IndexLinear()
-IndexStyle(::Type{<:AbstractRange}) = IndexLinear()
-
-IndexStyle(A::AbstractArray, B::AbstractArray) = IndexStyle(IndexStyle(A), IndexStyle(B))
-IndexStyle(A::AbstractArray, B::AbstractArray...) = IndexStyle(IndexStyle(A), IndexStyle(B...))
-IndexStyle(::IndexLinear, ::IndexLinear) = IndexLinear()
-IndexStyle(::IndexStyle, ::IndexStyle) = IndexCartesian()
-
 ## Bounds checking ##
 
 # The overall hierarchy is
@@ -411,10 +343,11 @@ function checkbounds(::Type{Bool}, A::AbstractArray, I...)
     @_inline_meta
     checkbounds_indices(Bool, axes(A), I)
 end
+
 # Linear indexing is explicitly allowed when there is only one (non-cartesian) index
 function checkbounds(::Type{Bool}, A::AbstractArray, i)
     @_inline_meta
-    checkindex(Bool, linearindices(A), i)
+    checkindex(Bool, eachindex(IndexLinear(), A), i)
 end
 # As a special extension, allow using logical arrays that match the source array exactly
 function checkbounds(::Type{Bool}, A::AbstractArray{<:Any,N}, I::AbstractArray{Bool,N}) where N
@@ -674,7 +607,7 @@ function copyto!(dest::AbstractArray, dstart::Integer, src, sstart::Integer, n::
     n < 0 && throw(ArgumentError(string("tried to copy n=", n, " elements, but n should be nonnegative")))
     n == 0 && return dest
     dmax = dstart + n - 1
-    inds = linearindices(dest)
+    inds = LinearIndices(dest)
     if (dstart ∉ inds || dmax ∉ inds) | (sstart < 1)
         sstart < 1 && throw(ArgumentError(string("source start offset (",sstart,") is < 1")))
         throw(BoundsError(dest, dstart:dmax))
@@ -704,7 +637,7 @@ copyto!(dest::AbstractArray, src::AbstractArray) =
     copyto!(IndexStyle(dest), dest, IndexStyle(src), src)
 
 function copyto!(::IndexStyle, dest::AbstractArray, ::IndexStyle, src::AbstractArray)
-    destinds, srcinds = linearindices(dest), linearindices(src)
+    destinds, srcinds = LinearIndices(dest), LinearIndices(src)
     isempty(srcinds) || (first(srcinds) ∈ destinds && last(srcinds) ∈ destinds) ||
         throw(BoundsError(dest, srcinds))
     @inbounds for i in srcinds
@@ -714,7 +647,7 @@ function copyto!(::IndexStyle, dest::AbstractArray, ::IndexStyle, src::AbstractA
 end
 
 function copyto!(::IndexStyle, dest::AbstractArray, ::IndexCartesian, src::AbstractArray)
-    destinds, srcinds = linearindices(dest), linearindices(src)
+    destinds, srcinds = LinearIndices(dest), LinearIndices(src)
     isempty(srcinds) || (first(srcinds) ∈ destinds && last(srcinds) ∈ destinds) ||
         throw(BoundsError(dest, srcinds))
     i = 0
@@ -725,11 +658,11 @@ function copyto!(::IndexStyle, dest::AbstractArray, ::IndexCartesian, src::Abstr
 end
 
 function copyto!(dest::AbstractArray, dstart::Integer, src::AbstractArray)
-    copyto!(dest, dstart, src, first(linearindices(src)), _length(src))
+    copyto!(dest, dstart, src, first(LinearIndices(src)), _length(src))
 end
 
 function copyto!(dest::AbstractArray, dstart::Integer, src::AbstractArray, sstart::Integer)
-    srcinds = linearindices(src)
+    srcinds = LinearIndices(src)
     sstart ∈ srcinds || throw(BoundsError(src, sstart))
     copyto!(dest, dstart, src, sstart, last(srcinds)-sstart+1)
 end
@@ -739,7 +672,7 @@ function copyto!(dest::AbstractArray, dstart::Integer,
                n::Integer)
     n == 0 && return dest
     n < 0 && throw(ArgumentError(string("tried to copy n=", n, " elements, but n should be nonnegative")))
-    destinds, srcinds = linearindices(dest), linearindices(src)
+    destinds, srcinds = LinearIndices(dest), LinearIndices(src)
     (dstart ∈ destinds && dstart+n-1 ∈ destinds) || throw(BoundsError(dest, dstart:dstart+n-1))
     (sstart ∈ srcinds  && sstart+n-1 ∈ srcinds)  || throw(BoundsError(src,  sstart:sstart+n-1))
     @inbounds for i = 0:(n-1)
@@ -868,11 +801,13 @@ function eachindex(A::AbstractArray, B::AbstractArray...)
     @_inline_meta
     eachindex(IndexStyle(A,B...), A, B...)
 end
-eachindex(::IndexLinear, A::AbstractArray) = linearindices(A)
+eachindex(::IndexLinear, A::AbstractArray) = (@_inline_meta; OneTo(_length(A)))
+eachindex(::IndexLinear, A::AbstractVector) = (@_inline_meta; indices1(A))
 function eachindex(::IndexLinear, A::AbstractArray, B::AbstractArray...)
     @_inline_meta
-    indsA = linearindices(A)
-    _all_match_first(linearindices, indsA, B...) || throw_eachindex_mismatch(IndexLinear(), A, B...)
+    indsA = eachindex(IndexLinear(), A)
+    _all_match_first(X->eachindex(IndexLinear(), X), indsA, B...) ||
+        throw_eachindex_mismatch(IndexLinear(), A, B...)
     indsA
 end
 function _all_match_first(f::F, inds, A, B...) where F<:Function
@@ -911,7 +846,7 @@ end
 pointer(x::AbstractArray{T}) where {T} = unsafe_convert(Ptr{T}, x)
 function pointer(x::AbstractArray{T}, i::Integer) where T
     @_inline_meta
-    unsafe_convert(Ptr{T}, x) + (i - first(linearindices(x)))*elsize(x)
+    unsafe_convert(Ptr{T}, x) + (i - first(LinearIndices(x)))*elsize(x)
 end
 
 ## Approach:
@@ -2025,7 +1960,7 @@ end
 @inline ith_all(i, as) = (as[1][i], ith_all(i, tail(as))...)
 
 function map_n!(f::F, dest::AbstractArray, As) where F
-    for i = linearindices(As[1])
+    for i = LinearIndices(As[1])
         dest[i] = f(ith_all(i, As)...)
     end
     return dest

base/array.jl

@@ -567,7 +567,7 @@ function _collect(c, itr, ::EltypeUnknown, isz::Union{HasLength,HasShape})
 end
 
 function collect_to_with_first!(dest::AbstractArray, v1, itr, st)
-    i1 = first(linearindices(dest))
+    i1 = first(LinearIndices(dest))
     dest[i1] = v1
     return collect_to!(dest, itr, i1+1, st)
 end
@@ -1385,15 +1385,15 @@ julia> reverse(A, 3, 5)
  3
 ```
 """
-function reverse(A::AbstractVector, s=first(linearindices(A)), n=last(linearindices(A)))
+function reverse(A::AbstractVector, s=first(LinearIndices(A)), n=last(LinearIndices(A)))
     B = similar(A)
-    for i = first(linearindices(A)):s-1
+    for i = first(LinearIndices(A)):s-1
         B[i] = A[i]
     end
     for i = s:n
         B[i] = A[n+s-i]
     end
-    for i = n+1:last(linearindices(A))
+    for i = n+1:last(LinearIndices(A))
         B[i] = A[i]
     end
     return B
@@ -1403,7 +1403,7 @@ end
 reverse(A::Vector) = invoke(reverse, Tuple{AbstractVector}, A)
 
 function reverseind(a::AbstractVector, i::Integer)
-    li = linearindices(a)
+    li = LinearIndices(a)
     first(li) + last(li) - i
 end
 
@@ -1433,8 +1433,8 @@ julia> A
  1
 ```
 """
-function reverse!(v::AbstractVector, s=first(linearindices(v)), n=last(linearindices(v)))
-    liv = linearindices(v)
+function reverse!(v::AbstractVector, s=first(LinearIndices(v)), n=last(LinearIndices(v)))
+    liv = LinearIndices(v)
     if n <= s  # empty case; ok
     elseif !(first(liv) ≤ s ≤ last(liv))
         throw(BoundsError(v, s))

base/broadcast.jl

@@ -3,7 +3,7 @@
 module Broadcast
 
 using .Base.Cartesian
-using .Base: Indices, OneTo, linearindices, tail, to_shape,
+using .Base: Indices, OneTo, tail, to_shape,
             _msk_end, unsafe_bitgetindex, bitcache_chunks, bitcache_size, dumpbitcache,
             isoperator, promote_typejoin, unalias
 import .Base: broadcast, broadcast!

base/deprecated.jl

@@ -1580,6 +1580,8 @@ function search(buf::IOBuffer, delim::UInt8)
     return Int(q-p+1)
 end
 
+@deprecate linearindices(x::AbstractArray) LinearIndices(x)
+
 # PR #26647
 # The `keep` argument in `split` and `rpslit` has been renamed to `keepempty`.
 # To remove this deprecation, remove the `keep` argument from the function signatures as well as

base/errorshow.jl

@@ -553,7 +553,7 @@ function is_default_method(m::Method)
 end
 
 @noinline function throw_eachindex_mismatch(::IndexLinear, A...)
-    throw(DimensionMismatch("all inputs to eachindex must have the same indices, got $(join(linearindices.(A), ", ", " and "))"))
+    throw(DimensionMismatch("all inputs to eachindex must have the same indices, got $(join(LinearIndices.(A), ", ", " and "))"))
 end
 @noinline function throw_eachindex_mismatch(::IndexCartesian, A...)
     throw(DimensionMismatch("all inputs to eachindex must have the same axes, got $(join(axes.(A), ", ", " and "))"))

base/essentials.jl

@@ -535,7 +535,6 @@ next(v::SimpleVector,i) = (v[i],i+1)
 done(v::SimpleVector,i) = (length(v) < i)
 isempty(v::SimpleVector) = (length(v) == 0)
 axes(v::SimpleVector) = (OneTo(length(v)),)
-linearindices(v::SimpleVector) = axes(v, 1)
 axes(v::SimpleVector, d) = d <= 1 ? axes(v)[d] : OneTo(1)
 
 function ==(v1::SimpleVector, v2::SimpleVector)

base/exports.jl

@@ -392,7 +392,6 @@ export
     isperm,
     issorted,
     last,
-    linearindices,
     mapslices,
     max,
     maximum!,