Julia: Sparse matrix allows for duplicate entries

[mirestrepo]

The representation of sparse matrices allow for duplicates. This seems prone to errors, for instance computing the number of non-zeros entries would be incorrect.

Since this is not allowed in full matrices, does it make any sense to have this be the behavior for sparse matrices?

julia> a = spzeros(2, 3)
2×3 SparseMatrixCSC{Float64,Int64} with 0 stored entries

julia> a[[1,1,1,1,1,1],2]=1
1

julia> a
2×3 SparseMatrixCSC{Float64,Int64} with 6 stored entries:
  [1, 2]  =  1.0
  [1, 2]  =  1.0
  [1, 2]  =  1.0
  [1, 2]  =  1.0
  [1, 2]  =  1.0
  [1, 2]  =  1.0

[Sacha0]

Looks like a bug in setindex!?