Consistently use linear indexing in copyto!(dest, src) (JuliaLang#34049)

base/multidimensional.jl

@@ -961,12 +961,23 @@ julia> y
 copyto!(dest, src)
 
 function copyto!(dest::AbstractArray{T1,N}, src::AbstractArray{T2,N}) where {T1,T2,N}
- checkbounds(dest, axes(src)...)
  src′ = unalias(dest, src)
- for I in eachindex(IndexStyle(src′,dest), src′)
- @inbounds dest[I] = src′[I]
+ # fastpath for equal axes (#34025)
+ if axes(dest) == axes(src)
+ for I in eachindex(IndexStyle(src′,dest), src′)
+ @inbounds dest[I] = src′[I]
+ end
+ # otherwise enforce linear indexing
+ else
+ isrc = eachindex(IndexLinear(), src)
+ idest = eachindex(IndexLinear(), dest)
+ ΔI = first(idest) - first(isrc)
+ checkbounds(dest, last(isrc) + ΔI)
+ for I in isrc
+ @inbounds dest[I + ΔI] = src′[I]
+ end
  end
- dest
+ return dest
 end
 
 function copyto!(dest::AbstractArray{T1,N}, Rdest::CartesianIndices{N},

test/copy.jl

@@ -212,3 +212,18 @@ end
  # Test that edges are not shared
  @test ci2.edges !== ci.edges
 end
+
+@testset "issue #34025" begin
+ s = [2 0; 0 3]
+ r = ones(Int, 3, 3)
+ @test copyto!(copy(r), s') == [2 3 1; 0 1 1; 0 1 1]
+ @test copyto!(copy(r), s) == copyto!(copy(r), s') ==
+ copyto!(copy(r)', s) == copyto!(copy(r)', s')
+ r = ones(Int, 3, 3)
+ s = [1 2 3 4]'
+ @test copyto!(r, s) == [1 4 1; 2 1 1; 3 1 1]
+ a = fill(1, 5)
+ r = Base.IdentityUnitRange(-1:1)
+ copyto!(a, r)
+ @test a[1:3] == [-1, 0, 1]
+end

test/offsetarray.jl

@@ -290,12 +290,15 @@ copyto!(a, -2, (1,2,3), 1, 2)
 
 b = 1:2 # copy between AbstractArrays
 bo = OffsetArray(1:2, (-3,))
-@test_throws BoundsError copyto!(a, b)
+copyto!(a, b) # no BoundsError, see #34049
+@test a[-3] == 1
+@test a[-2] == 2
+@test a[-1] == 2
 fill!(a, -1)
 copyto!(a, bo)
-@test a[-3] == -1
-@test a[-2] == 1
-@test a[-1] == 2
+@test a[-3] == 1
+@test a[-2] == 2
+@test a[-1] == -1
 fill!(a, -1)
 copyto!(a, -2, bo)
 @test a[-3] == -1