[BUG] Broadcasting assignments are not working

[lkdvos]

MWE:

using SparseArraysBase
a = SparseArraysBase.SparseArrayDOK{Float64}(2,2)
a[1] = 1

julia> a
2×2 SparseMatrixDOK{Float64, typeof(SparseArraysBase.default_getunstoredindex)}:
 1.0  ⋅
  ⋅   ⋅

julia> a .*= 2
2×2 SparseMatrixDOK{Float64, typeof(SparseArraysBase.default_getunstoredindex)}:
 0.0  ⋅
  ⋅   ⋅

[mtfishman]

Reminder to simplify the code introduced in #18 once this is fixed.

[mtfishman]

It looks like the offending line is this one:

SparseArraysBase.jl/src/abstractsparsearrayinterface.jl

Line 275 in a57e030

@interface interface zero!(a_dest)

We have to zero out the destination if it has values that won't get overwritten when mapping over the stored values of the source arrays, but that obviously goes wrong if the destination is aliased with one or more of the sources.

We'll have to add some unaliasing logic like in Base.Broadcast.