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fix #23107, ensure Array constructor always makes new arrays #23490

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Aug 30, 2017
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fix #23107, ensure Array constructor always makes new arrays #23490

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6 changes: 6 additions & 0 deletions base/array.jl
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Expand Up @@ -563,6 +563,12 @@ convert(::Type{Array{T,n}}, x::AbstractArray{S,n}) where {T,n,S} = copy!(Array{T

promote_rule(a::Type{Array{T,n}}, b::Type{Array{S,n}}) where {T,n,S} = el_same(promote_type(T,S), a, b)

# constructors should make copies
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@nalimilan nalimilan Aug 29, 2017 •
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Is this documented somewhere? This is something I wondered when writing CategoricalArrays contructors. Since one-argument constructors fall back to convert, by default they do not make copies. I agree it would make sense for convertnot to make a copy and for constructors to make a copy, but this should be stated clearly in the manual. Then we should review other types in Base (and in our packages) to check that this rule is followed consistently (not only for arrays).

EDIT: Sorry, I had missed the discussion at #23107. I agree with the conclusion there, so this is just a request to document this behavior instead of just silently doing it. :-)

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I'll re-do the manual entries on convert and construct as part of #15120. In progress in #23273.


if module_name(@__MODULE__) === :Base # avoid method overwrite
(::Type{T})(x::T) where {T<:Array} = copy(x)
end

## copying iterators to containers

"""
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4 changes: 4 additions & 0 deletions base/bitarray.jl
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Expand Up @@ -555,6 +555,10 @@ reinterpret(B::BitArray, dims::NTuple{N,Int}) where {N} = reshape(B, dims)

BitArray(A::AbstractArray{<:Any,N}) where {N} = convert(BitArray{N}, A)

if module_name(@__MODULE__) === :Base # avoid method overwrite
(::Type{T})(x::T) where {T<:BitArray} = copy(x)
end

"""
BitArray(itr)

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7 changes: 7 additions & 0 deletions test/arrayops.jl
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Expand Up @@ -90,6 +90,13 @@ using TestHelpers.OAs
@test ndims(a) == 5
@test a[2,1,2,2,1] == b[14]
@test a[2,2,2,2,2] == b[end]

# issue #23107
a = [1,2,3]
@test typeof(a)(a) !== a
@test Array(a) !== a
@test Array{eltype(a)}(a) !== a
@test Vector(a) !== a
end
@testset "reshaping SubArrays" begin
a = collect(reshape(1:5, 1, 5))
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5 changes: 5 additions & 0 deletions test/bitarray.jl
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Expand Up @@ -190,6 +190,11 @@ timesofar("utils")
@test Array(one(BitMatrix(2,2))) == eye(2,2)
@test_throws DimensionMismatch one(BitMatrix(2,3))
end

# constructors should copy
a = trues(3)
@test BitArray(a) !== a
@test BitArray{1}(a) !== a
end

timesofar("constructors")
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