Indexing over zero-length lists or arrays fails #174
Description
using ComponentArrays
a = ComponentVector(;a=1, b=2)
julia> a[()]
ERROR: MethodError: reducing over an empty collection is not allowed; consider supplying `init` to the reducer
Stacktrace:
[1] reduce_empty(op::Base.BottomRF{typeof(vcat)}, #unused#::Type{Union{}})
@ Base ./reduce.jl:355
[2] reduce_empty_iter(op::Base.BottomRF{typeof(vcat)}, itr::Tuple{}, #unused#::Base.HasEltype)
@ Base ./reduce.jl:379
[3] reduce_empty_iter(op::Base.BottomRF{typeof(vcat)}, itr::Tuple{})
@ Base ./reduce.jl:378
[4] foldl_impl(op::Base.BottomRF{typeof(vcat)}, nt::Base._InitialValue, itr::Tuple{})
@ Base ./reduce.jl:49
[5] mapfoldl_impl(f::typeof(identity), op::typeof(vcat), nt::Base._InitialValue, itr::Tuple{})
@ Base ./reduce.jl:44
[6] mapfoldl(f::Function, op::Function, itr::Tuple{}; init::Base._InitialValue)
@ Base ./reduce.jl:170
[7] mapfoldl
@ ./reduce.jl:170 [inlined]
[8] #mapreduce#263
@ ./reduce.jl:302 [inlined]
[9] mapreduce
@ ./reduce.jl:302 [inlined]
[10] #reduce#265
@ ./reduce.jl:483 [inlined]
[11] reduce(op::Function, itr::Tuple{})
@ Base ./reduce.jl:483
[12] getindex(ax::Axis{(a = 1, b = 2)}, syms::Tuple{})
@ ComponentArrays ~/.julia/packages/ComponentArrays/YyD7i/src/axis.jl:173
[13] _broadcast_getindex_evalf
@ ./broadcast.jl:670 [inlined]
[14] _broadcast_getindex
@ ./broadcast.jl:643 [inlined]
[15] (::Base.Broadcast.var"#29#30"{Base.Broadcast.Broadcasted{Base.Broadcast.Style{Tuple}, Nothing, typeof(getindex), Tuple{Tuple{Axis{(a = 1, b = 2)}}, Base.Broadcast.Broadcasted{Base.Broadcast.Style{Tuple}, Nothing, typeof(ComponentArrays.getval), Tuple{Tuple{DataType}}}}}})(k::Int64)
@ Base.Broadcast ./broadcast.jl:1075
[16] ntuple
@ ./ntuple.jl:48 [inlined]
[17] copy
@ ./broadcast.jl:1075 [inlined]
[18] materialize(bc::Base.Broadcast.Broadcasted{Base.Broadcast.Style{Tuple}, Nothing, typeof(getindex), Tuple{Tuple{Axis{(a = 1, b = 2)}}, Base.Broadcast.Broadcasted{Base.Broadcast.Style{Tuple}, Nothing, typeof(ComponentArrays.getval), Tuple{Tuple{DataType}}}}})
@ Base.Broadcast ./broadcast.jl:860
[19] #s15#55
@ ~/.julia/packages/ComponentArrays/YyD7i/src/array_interface.jl:122 [inlined]
[20] var"#s15#55"(::Any, index_fun::Any, x::Any, idx::Any)
@ ComponentArrays ./none:0
[21] (::Core.GeneratedFunctionStub)(::Any, ::Vararg{Any})
@ Core ./boot.jl:582
[22] getindex
@ ~/.julia/packages/ComponentArrays/YyD7i/src/array_interface.jl:105 [inlined]
[23] getindex(x::ComponentVector{Int64, Vector{Int64}, Tuple{Axis{(a = 1, b = 2)}}}, idx::Tuple{})
@ ComponentArrays ~/.julia/packages/ComponentArrays/YyD7i/src/array_interface.jl:104
[24] top-level scope
@ REPL[9]:1
julia> a[Vector{Symbol}()]
ERROR: MethodError: reducing over an empty collection is not allowed; consider supplying `init` to the reducer
Stacktrace:
[1] reduce_empty(op::Base.BottomRF{typeof(vcat)}, #unused#::Type{Union{}})
@ Base ./reduce.jl:355
[2] reduce_empty_iter(op::Base.BottomRF{typeof(vcat)}, itr::Tuple{}, #unused#::Base.HasEltype)
@ Base ./reduce.jl:379
[3] reduce_empty_iter(op::Base.BottomRF{typeof(vcat)}, itr::Tuple{})
@ Base ./reduce.jl:378
[4] foldl_impl(op::Base.BottomRF{typeof(vcat)}, nt::Base._InitialValue, itr::Tuple{})
@ Base ./reduce.jl:49
[5] mapfoldl_impl(f::typeof(identity), op::typeof(vcat), nt::Base._InitialValue, itr::Tuple{})
@ Base ./reduce.jl:44
[6] mapfoldl(f::Function, op::Function, itr::Tuple{}; init::Base._InitialValue)
@ Base ./reduce.jl:170
[7] mapfoldl
@ ./reduce.jl:170 [inlined]
[8] #mapreduce#263
@ ./reduce.jl:302 [inlined]
[9] mapreduce
@ ./reduce.jl:302 [inlined]
[10] #reduce#265
@ ./reduce.jl:483 [inlined]
[11] reduce(op::Function, itr::Tuple{})
@ Base ./reduce.jl:483
[12] getindex(ax::Axis{(a = 1, b = 2)}, syms::Tuple{})
@ ComponentArrays ~/.julia/packages/ComponentArrays/YyD7i/src/axis.jl:173
[13] _broadcast_getindex_evalf
@ ./broadcast.jl:670 [inlined]
[14] _broadcast_getindex
@ ./broadcast.jl:643 [inlined]
[15] (::Base.Broadcast.var"#29#30"{Base.Broadcast.Broadcasted{Base.Broadcast.Style{Tuple}, Nothing, typeof(getindex), Tuple{Tuple{Axis{(a = 1, b = 2)}}, Base.Broadcast.Broadcasted{Base.Broadcast.Style{Tuple}, Nothing, typeof(ComponentArrays.getval), Tuple{Tuple{DataType}}}}}})(k::Int64)
@ Base.Broadcast ./broadcast.jl:1075
[16] ntuple
@ ./ntuple.jl:48 [inlined]
[17] copy
@ ./broadcast.jl:1075 [inlined]
[18] materialize(bc::Base.Broadcast.Broadcasted{Base.Broadcast.Style{Tuple}, Nothing, typeof(getindex), Tuple{Tuple{Axis{(a = 1, b = 2)}}, Base.Broadcast.Broadcasted{Base.Broadcast.Style{Tuple}, Nothing, typeof(ComponentArrays.getval), Tuple{Tuple{DataType}}}}})
@ Base.Broadcast ./broadcast.jl:860
[19] #s15#55
@ ~/.julia/packages/ComponentArrays/YyD7i/src/array_interface.jl:122 [inlined]
[20] var"#s15#55"(::Any, index_fun::Any, x::Any, idx::Any)
@ ComponentArrays ./none:0
[21] (::Core.GeneratedFunctionStub)(::Any, ::Vararg{Any})
@ Core ./boot.jl:582
[22] getindex
@ ~/.julia/packages/ComponentArrays/YyD7i/src/array_interface.jl:105 [inlined]
[23] getindex(x::ComponentVector{Int64, Vector{Int64}, Tuple{Axis{(a = 1, b = 2)}}}, idx::Vector{Symbol})
@ ComponentArrays ~/.julia/packages/ComponentArrays/YyD7i/src/array_interface.jl:104
[24] top-level scope
@ REPL[11]:1
julia> a[[]]
ERROR: TypeError: in Type, in parameter, expected Type, got a value of type Vector{Any}
Stacktrace:
[1] Val(x::Vector{Any})
@ Base ./essentials.jl:714
[2] toval
@ ~/.julia/packages/ComponentArrays/YyD7i/src/utils.jl:6 [inlined]
[3] _broadcast_getindex_evalf
@ ./broadcast.jl:670 [inlined]
[4] _broadcast_getindex
@ ./broadcast.jl:643 [inlined]
[5] #29
@ ./broadcast.jl:1075 [inlined]
[6] ntuple
@ ./ntuple.jl:48 [inlined]
[7] copy
@ ./broadcast.jl:1075 [inlined]
[8] materialize
@ ./broadcast.jl:860 [inlined]
[9] getindex(x::ComponentVector{Int64, Vector{Int64}, Tuple{Axis{(a = 1, b = 2)}}}, idx::Vector{Any})
@ ComponentArrays ~/.julia/packages/ComponentArrays/YyD7i/src/array_interface.jl:104
[10] top-level scope
@ REPL[10]:1The first two can be fixed by changing reduce(vcat, inds) to vcat(inds) here. But then there is type instability in that a normal vector is returned back (related to #173).