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Throw an error when collecting from iterators with inconsistent length #29458

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Throw an error when collecting from iterators with inconsistent length #29458

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3f4a404
Throw an error when collecting from iterators with inconsistent length
nalimilan Oct 1, 2018
e811fa6
Review fixes
nalimilan Oct 5, 2018
c7b6896
Use _copy_impl! instead of custom function
nalimilan Oct 5, 2018
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13 changes: 11 additions & 2 deletions base/abstractarray.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -640,7 +640,9 @@ emptymutable(itr, ::Type{U}) where {U} = Vector{U}()

## from general iterable to any array

function copyto!(dest::AbstractArray, src)
copyto!(dest::AbstractArray, src) = _copyto_impl!(dest, src, true)

function _copyto_impl!(dest::AbstractArray, src, allowshorter::Bool)
destiter = eachindex(dest)
y = iterate(destiter)
for x in src
Expand All @@ -649,6 +651,9 @@ function copyto!(dest::AbstractArray, src)
dest[y[1]] = x
y = iterate(destiter, y[2])
end
if !allowshorter && y !== nothing
throw(ArgumentError(string("source has fewer elements than destination")))
end
return dest
end

Expand Down Expand Up @@ -720,8 +725,12 @@ end
## copy between abstract arrays - generally more efficient
## since a single index variable can be used.

copyto!(dest::AbstractArray, src::AbstractArray) =
function _copyto_impl!(dest::AbstractArray, src::AbstractArray, allowshorter::Bool)
if !allowshorter && length(src) < length(dest)
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This check and the one below is actually not needed for this PR since we already allocate an array of the correct length, and the AbstractArray interface relies on the fact that the length is correctly declared. But I added these for consistency, so that the allowshorter argument (which needs to be accepted) isn't a no-op. I can drop it and add a comment explaining that if you want.

throw(ArgumentError("source has fewer elements than destination"))
end
copyto!(IndexStyle(dest), dest, IndexStyle(src), src)
end

function copyto!(::IndexStyle, dest::AbstractArray, ::IndexStyle, src::AbstractArray)
destinds, srcinds = LinearIndices(dest), LinearIndices(src)
Expand Down
23 changes: 19 additions & 4 deletions base/array.jl
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Expand Up @@ -274,7 +274,12 @@ function copyto!(dest::Array{T}, doffs::Integer, src::Array{T}, soffs::Integer,
unsafe_copyto!(dest, doffs, src, soffs, n)
end

copyto!(dest::Array{T}, src::Array{T}) where {T} = copyto!(dest, 1, src, 1, length(src))
function _copyto_impl!(dest::Array{T}, src::Array{T}, allowshorter::Bool) where {T}
if !allowshorter && length(src) < length(dest)
throw(ArgumentError("source has fewer elements than destination"))
end
copyto!(dest, 1, src, 1, length(src))
end

# N.B: The generic definition in multidimensional.jl covers, this, this is just here
# for bootstrapping purposes.
Expand Down Expand Up @@ -517,8 +522,10 @@ julia> collect(Float64, 1:2:5)
"""
collect(::Type{T}, itr) where {T} = _collect(T, itr, IteratorSize(itr))

_collect(::Type{T}, itr, isz::HasLength) where {T} = copyto!(Vector{T}(undef, Int(length(itr)::Integer)), itr)
_collect(::Type{T}, itr, isz::HasShape) where {T} = copyto!(similar(Array{T}, axes(itr)), itr)
_collect(::Type{T}, itr, isz::HasLength) where {T} =
_copyto_impl!(Vector{T}(undef, Int(length(itr)::Integer)), itr, false)
_collect(::Type{T}, itr, isz::HasShape) where {T} =
_copyto_impl!(similar(Array{T}, axes(itr)), itr, false)
function _collect(::Type{T}, itr, isz::SizeUnknown) where T
a = Vector{T}()
for x in itr
Expand Down Expand Up @@ -561,7 +568,7 @@ collect(A::AbstractArray) = _collect_indices(axes(A), A)
collect_similar(cont, itr) = _collect(cont, itr, IteratorEltype(itr), IteratorSize(itr))

_collect(cont, itr, ::HasEltype, isz::Union{HasLength,HasShape}) =
copyto!(_similar_for(cont, eltype(itr), itr, isz), itr)
_copyto_impl!(_similar_for(cont, eltype(itr), itr, isz), itr, false)

function _collect(cont, itr, ::HasEltype, isz::SizeUnknown)
a = _similar_for(cont, eltype(itr), itr, isz)
Expand Down Expand Up @@ -618,6 +625,9 @@ function collect(itr::Generator)
else
y = iterate(itr)
if y === nothing
if isa(isz, Union{HasLength, HasShape}) && length(itr) != 0
throw(ArgumentError("iterator returned fewer elements than its declared length"))
end
return _array_for(et, itr.iter, isz)
end
v1, st = y
Expand Down Expand Up @@ -667,6 +677,11 @@ function collect_to!(dest::AbstractArray{T}, itr, offs, st) where T
return collect_to!(new, itr, i+1, st)
end
end
lastidx = lastindex(dest)
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This should actually be last(LinearIndices(dest)). Will fix in the next round of reviews.

i-1 < lastidx &&
throw(ArgumentError("iterator returned fewer elements than its declared length"))
i-1 > lastidx &&
throw(ArgumentError("iterator returned more elements than its declared length"))
return dest
end

Expand Down
6 changes: 5 additions & 1 deletion base/multidimensional.jl
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Expand Up @@ -815,8 +815,12 @@ julia> y
"""
copyto!(dest, src)

function copyto!(dest::AbstractArray{T,N}, src::AbstractArray{T,N}) where {T,N}
function _copyto_impl!(dest::AbstractArray{T,N}, src::AbstractArray{T,N},
allowshorter::Bool) where {T,N}
checkbounds(dest, axes(src)...)
if !allowshorter && length(src) < length(dest)
throw(ArgumentError("source has fewer elements than destination"))
end
src′ = unalias(dest, src)
for I in eachindex(IndexStyle(src′,dest), src′)
@inbounds dest[I] = src′[I]
Expand Down
25 changes: 25 additions & 0 deletions test/arrayops.jl
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Expand Up @@ -2524,3 +2524,28 @@ Base.view(::T25958, args...) = args
@test t[end,end,1] == @view(t[end,end,1]) == @views t[end,end,1]
@test t[end,end,end] == @view(t[end,end,end]) == @views t[end,end,end]
end

# Iterator with declared length too large
struct InvalidIter1 end
Base.length(::InvalidIter1) = 2
Base.iterate(::InvalidIter1, i=1) = i > 1 ? nothing : (i, (i + 1))
# Iterator with declared length too small
struct InvalidIter2 end
Base.length(::InvalidIter2) = 2
Base.iterate(::InvalidIter2, i=1) = i > 3 ? nothing : (i, (i + 1))
@testset "collect on iterator with incorrect length" begin
@test_throws ArgumentError collect(InvalidIter1())
@test_throws ArgumentError collect(Any, InvalidIter1())
@test_throws ArgumentError collect(Int, InvalidIter1())
@test_throws ArgumentError [x for x in InvalidIter1()]
# Should also throw ArgumentError
@test_broken length(Int[x for x in InvalidIter1()]) != 2

@test_throws ArgumentError collect(InvalidIter2())
@test_throws ArgumentError collect(Any, InvalidIter2())
@test_throws ArgumentError collect(Int, InvalidIter2())
# These cases cannot be tested without writing to invalid memory
# unless the function checked bounds on each iteration (#29458)
# @test_throws ErrorException [x for x in InvalidIter2()]
# @test_broken length(Int[x for x in InvalidIter2()]) != 2
end