dropstored! had one job

[Sacha0]

Tracker for #20488 (comment). dropstored! appears broken:

julia> foo = sprand(4, 4, 0.5)
4×4 sparse matrix with 10 Float64 stored entries:
  [2, 1]  =  0.986522
  [1, 2]  =  0.331456
  [2, 2]  =  0.181261
  [4, 2]  =  0.545928
  [1, 3]  =  0.864019
  [2, 3]  =  0.48957
  [3, 3]  =  0.575748
  [4, 3]  =  0.509864
  [1, 4]  =  0.368723
  [3, 4]  =  0.332495

julia> Base.SparseArrays.dropstored!(foo, 2, 1)
4×4 sparse matrix with 9 Float64 stored entries:Error showing value of type SparseMatrixCSC{Float64,Int64}:
ERROR: BoundsError: attempt to access 9-element Array{Int64,1} at index [0]
Stacktrace:
 [1] show(::IOContext{Base.Terminals.TTYTerminal}, ::SparseMatrixCSC{Float64,Int64}) at ./sparse/sparsematrix.jl:147
 [2] show(::IOContext{Base.Terminals.TTYTerminal}, ::MIME{Symbol("text/plain")}, ::SparseMatrixCSC{Float64,Int64}) at ./sparse/sparsematrix.jl:122
 [3] display(::Base.REPL.REPLDisplay{Base.REPL.LineEditREPL}, ::MIME{Symbol("text/plain")}, ::SparseMatrixCSC{Float64,Int64}) at ./REPL.jl:122
 [4] display(::Base.REPL.REPLDisplay{Base.REPL.LineEditREPL}, ::SparseMatrixCSC{Float64,Int64}) at ./REPL.jl:125
 [5] display(::SparseMatrixCSC{Float64,Int64}) at ./multimedia.jl:194

julia> foo.colptr
5-element Array{Int64,1}:
  0
  1
  4
  8
 10

Best!

[KristofferC]

diff --git a/base/sparse/sparsematrix.jl b/base/sparse/sparsematrix.jl
index 21720ab..fb6e0c5 100644
--- a/base/sparse/sparsematrix.jl
+++ b/base/sparse/sparsematrix.jl
@@ -2788,7 +2788,7 @@ function dropstored!(A::SparseMatrixCSC, i::Integer, j::Integer)
         # Entry A[i,j] is stored. Drop and return.
         deleteat!(A.rowval, searchk)
         deleteat!(A.nzval, searchk)
-        @simd for m in j:(A.n + 1)
+        @simd for m in (j+1):(A.n + 1)
             @inbounds A.colptr[m] -= 1
         end
     end

?