Stackoverflow with broadcast += between Vector and scalar*BlockedVector

[DanielVandH]

julia> using BlockArrays

julia> A = BlockedVector(1:6, [3, 2, 1]);

julia> B = zeros(6);

julia> @. B += A; # fine

julia> @. B += 1A; # broken. @. B + 1A works fine though.
ERROR: StackOverflowError:
Stacktrace:
     [1] Array
       @ .\boot.jl:477 [inlined]
     [2] Array
       @ .\boot.jl:496 [inlined]
     [3] emptymutable
       @ .\abstractarray.jl:899 [inlined]
     [4] union
       @ .\abstractset.jl:57 [inlined]
     [5] sortedunion(a::Vector{Int64}, b::FillArrays.Fill{Int64, 1, Tuple{Base.OneTo{Int64}}})
       @ BlockArrays C:\Users\danjv\.julia\packages\BlockArrays\xi4on\src\blockbroadcast.jl:34
     [6] combine_blockaxes
       @ C:\Users\danjv\.julia\packages\BlockArrays\xi4on\src\blockbroadcast.jl:37 [inlined]
     [7] axistype
       @ C:\Users\danjv\.julia\packages\BlockArrays\xi4on\src\blockbroadcast.jl:41 [inlined]
     [8] _bcs1(a::Base.OneTo{Int64}, b::BlockedOneTo{Int64, Vector{Int64}})
       @ Base.Broadcast .\broadcast.jl:555
     [9] _bcs
       @ .\broadcast.jl:549 [inlined]
    [10] broadcast_shape
       @ .\broadcast.jl:543 [inlined]
    [11] combine_axes
       @ .\broadcast.jl:524 [inlined]
    [12] _axes
       @ .\broadcast.jl:236 [inlined]
    [13] axes
       @ .\broadcast.jl:234 [inlined]
    [14] materialize!
       @ C:\Users\danjv\.julia\packages\BlockArrays\xi4on\src\blockbroadcast.jl:128 [inlined]
    [15] broadcast!(::typeof(+), ::SubArray{…}, ::SubArray{…}, ::Base.Broadcast.Broadcasted{…})
       @ Base.Broadcast .\broadcast.jl:880
    [16] _fast_blockbradcast_copyto!
       @ C:\Users\danjv\.julia\packages\BlockArrays\xi4on\src\blockbroadcast.jl:173 [inlined]
    [17] copyto!(dest::SubArray{…}, bc::Base.Broadcast.Broadcasted{…})
       @ BlockArrays C:\Users\danjv\.julia\packages\BlockArrays\xi4on\src\blockbroadcast.jl:192
    [18] materialize!
       @ C:\Users\danjv\.julia\packages\BlockArrays\xi4on\src\blockbroadcast.jl:131 [inlined]
--- the last 4 lines are repeated 7911 more times ---
 [31663] broadcast!(::typeof(+), ::SubArray{…}, ::SubArray{…}, ::Base.Broadcast.Broadcasted{…})
       @ Base.Broadcast .\broadcast.jl:880
 [31664] _fast_blockbradcast_copyto!(dest::Vector{…}, bc::Base.Broadcast.Broadcasted{…})
       @ BlockArrays C:\Users\danjv\.julia\packages\BlockArrays\xi4on\src\blockbroadcast.jl:173
 [31665] copyto!(dest::Vector{…}, bc::Base.Broadcast.Broadcasted{…})
       @ BlockArrays C:\Users\danjv\.julia\packages\BlockArrays\xi4on\src\blockbroadcast.jl:192
Some type information was truncated. Use `show(err)` to see complete types.