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fix collect on stateful iterators
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Generalization of #41919
Fixes #42168
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vtjnash committed Sep 14, 2021
1 parent 4a048d3 commit 68e0813
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Showing 5 changed files with 52 additions and 34 deletions.
61 changes: 39 additions & 22 deletions base/array.jl
Original file line number Diff line number Diff line change
Expand Up @@ -643,23 +643,38 @@ 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::Union{HasLength,HasShape}) where {T} =
copyto!(_array_for(T, isz, _similar_shape(itr, isz)), itr)
function _collect(::Type{T}, itr, isz::SizeUnknown) where T
a = Vector{T}()
for x in itr
push!(a,x)
push!(a, x)
end
return a
end

# make a collection similar to `c` and appropriate for collecting `itr`
_similar_for(c::AbstractArray, ::Type{T}, itr, ::SizeUnknown) where {T} = similar(c, T, 0)
_similar_for(c::AbstractArray, ::Type{T}, itr, ::HasLength) where {T} =
similar(c, T, Int(length(itr)::Integer))
_similar_for(c::AbstractArray, ::Type{T}, itr, ::HasShape) where {T} =
similar(c, T, axes(itr))
_similar_for(c, ::Type{T}, itr, isz) where {T} = similar(c, T)
_similar_for(c, ::Type{T}, itr, isz, shp) where {T} = similar(c, T)

_similar_shape(itr, ::SizeUnknown) = nothing
_similar_shape(itr, ::HasLength) = length(itr)::Integer
_similar_shape(itr, ::HasShape) = axes(itr)

_similar_for(c::AbstractArray, ::Type{T}, itr, ::SizeUnknown, ::Nothing) where {T} =
similar(c, T, 0)
_similar_for(c::AbstractArray, ::Type{T}, itr, ::HasLength, len::Integer) where {T} =
similar(c, T, len)
_similar_for(c::AbstractArray, ::Type{T}, itr, ::HasShape, axs) where {T} =
similar(c, T, axs)

# make a collection appropriate for collecting `itr::Generator`
_array_for(::Type{T}, ::SizeUnknown, ::Nothing) where {T} = Vector{T}(undef, 0)
_array_for(::Type{T}, ::HasLength, len::Integer) where {T} = Vector{T}(undef, Int(len))
_array_for(::Type{T}, ::HasShape{N}, axs) where {T,N} = similar(Array{T,N}, axs)

# used by syntax lowering for simple typed comprehensions
_array_for(::Type{T}, itr, isz) where {T} = _array_for(T, isz, _similar_shape(itr, isz))


"""
collect(collection)
Expand Down Expand Up @@ -698,10 +713,10 @@ 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!(_similar_for(cont, eltype(itr), itr, isz, _similar_shape(itr, isz)), itr)

function _collect(cont, itr, ::HasEltype, isz::SizeUnknown)
a = _similar_for(cont, eltype(itr), itr, isz)
a = _similar_for(cont, eltype(itr), itr, isz, nothing)
for x in itr
push!(a,x)
end
Expand Down Expand Up @@ -759,24 +774,19 @@ else
end
end

_array_for(::Type{T}, itr, isz::HasLength) where {T} = _array_for(T, itr, isz, length(itr))
_array_for(::Type{T}, itr, isz::HasShape{N}) where {T,N} = _array_for(T, itr, isz, axes(itr))
_array_for(::Type{T}, itr, ::HasLength, len) where {T} = Vector{T}(undef, len)
_array_for(::Type{T}, itr, ::HasShape{N}, axs) where {T,N} = similar(Array{T,N}, axs)

function collect(itr::Generator)
isz = IteratorSize(itr.iter)
et = @default_eltype(itr)
if isa(isz, SizeUnknown)
return grow_to!(Vector{et}(), itr)
else
shape = isz isa HasLength ? length(itr) : axes(itr)
shp = _similar_shape(itr, isz)
y = iterate(itr)
if y === nothing
return _array_for(et, itr.iter, isz)
return _array_for(et, isz, shp)
end
v1, st = y
dest = _array_for(typeof(v1), itr.iter, isz, shape)
dest = _array_for(typeof(v1), isz, shp)
# The typeassert gives inference a helping hand on the element type and dimensionality
# (work-around for #28382)
et′ = et <: Type ? Type : et
Expand All @@ -786,15 +796,22 @@ function collect(itr::Generator)
end

_collect(c, itr, ::EltypeUnknown, isz::SizeUnknown) =
grow_to!(_similar_for(c, @default_eltype(itr), itr, isz), itr)
grow_to!(_similar_for(c, @default_eltype(itr), itr, isz, nothing), itr)

function _collect(c, itr, ::EltypeUnknown, isz::Union{HasLength,HasShape})
et = @default_eltype(itr)
shp = _similar_shape(itr, isz)
y = iterate(itr)
if y === nothing
return _similar_for(c, @default_eltype(itr), itr, isz)
return _similar_for(c, et, itr, isz, shp)
end
v1, st = y
collect_to_with_first!(_similar_for(c, typeof(v1), itr, isz), v1, itr, st)
dest = _similar_for(c, typeof(v1), itr, isz, shp)
# The typeassert gives inference a helping hand on the element type and dimensionality
# (work-around for #28382)
et′ = et <: Type ? Type : et
RT = dest isa AbstractArray ? AbstractArray{<:et′, ndims(dest)} : Any
collect_to_with_first!(dest, v1, itr, st)::RT
end

function collect_to_with_first!(dest::AbstractArray, v1, itr, st)
Expand Down
4 changes: 2 additions & 2 deletions base/dict.jl
Original file line number Diff line number Diff line change
Expand Up @@ -826,6 +826,6 @@ length(t::ImmutableDict) = count(Returns(true), t)
isempty(t::ImmutableDict) = !isdefined(t, :parent)
empty(::ImmutableDict, ::Type{K}, ::Type{V}) where {K, V} = ImmutableDict{K,V}()

_similar_for(c::Dict, ::Type{Pair{K,V}}, itr, isz) where {K, V} = empty(c, K, V)
_similar_for(c::AbstractDict, ::Type{T}, itr, isz) where {T} =
_similar_for(c::AbstractDict, ::Type{Pair{K,V}}, itr, isz, len) where {K, V} = empty(c, K, V)
_similar_for(c::AbstractDict, ::Type{T}, itr, isz, len) where {T} =
throw(ArgumentError("for AbstractDicts, similar requires an element type of Pair;\n if calling map, consider a comprehension instead"))
2 changes: 1 addition & 1 deletion base/set.jl
Original file line number Diff line number Diff line change
Expand Up @@ -44,7 +44,7 @@ empty(s::AbstractSet{T}, ::Type{U}=T) where {T,U} = Set{U}()
# by default, a Set is returned
emptymutable(s::AbstractSet{T}, ::Type{U}=T) where {T,U} = Set{U}()

_similar_for(c::AbstractSet, ::Type{T}, itr, isz) where {T} = empty(c, T)
_similar_for(c::AbstractSet, ::Type{T}, itr, isz, len) where {T} = empty(c, T)

function show(io::IO, s::Set)
if isempty(s)
Expand Down
8 changes: 3 additions & 5 deletions src/julia-syntax.scm
Original file line number Diff line number Diff line change
Expand Up @@ -2734,7 +2734,7 @@
(check-no-return expr)
(if (has-break-or-continue? expr)
(error "break or continue outside loop"))
(let ((result (gensy))
(let ((result (make-ssavalue))
(idx (gensy))
(oneresult (make-ssavalue))
(prod (make-ssavalue))
Expand All @@ -2758,16 +2758,14 @@
(let ((overall-itr (if (length= itrs 1) (car iv) prod)))
`(scope-block
(block
(local ,result) (local ,idx)
(local ,idx)
,.(map (lambda (v r) `(= ,v ,(caddr r))) iv itrs)
,.(if (length= itrs 1)
'()
`((= ,prod (call (top product) ,@iv))))
(= ,isz (call (top IteratorSize) ,overall-itr))
(= ,szunk (call (core isa) ,isz (top SizeUnknown)))
(if ,szunk
(= ,result (call (curly (core Array) ,ty 1) (core undef) 0))
(= ,result (call (top _array_for) ,ty ,overall-itr ,isz)))
(= ,result (call (top _array_for) ,ty ,overall-itr ,isz))
(= ,idx (call (top first) (call (top LinearIndices) ,result)))
,(construct-loops (reverse itrs) (reverse iv))
,result)))))
Expand Down
11 changes: 7 additions & 4 deletions test/iterators.jl
Original file line number Diff line number Diff line change
Expand Up @@ -293,11 +293,14 @@ let (a, b) = (1:3, [4 6;
end

# collect stateful iterator
let
itr = (i+1 for i in Base.Stateful([1,2,3]))
let itr
itr = Iterators.Stateful(Iterators.map(identity, 1:5))
@test collect(itr) == 1:5
@test collect(itr) == Int[] # Stateful do not preserve shape
itr = (i+1 for i in Base.Stateful([1, 2, 3]))
@test collect(itr) == [2, 3, 4]
A = zeros(Int, 0, 0)
itr = (i-1 for i in Base.Stateful(A))
@test collect(itr) == Int[] # Stateful do not preserve shape
itr = (i-1 for i in Base.Stateful(zeros(Int, 0, 0)))
@test collect(itr) == Int[] # Stateful do not preserve shape
end

Expand Down

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