Indexing of Symbolic Arrays (Arr{Num,3}) not working when a guess is provided in MTK

Specific Domains Modelling & Simulations
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1

Hello,

I have created a MWE where the indexing of symbolic arrays begins to fail when I provide an initial guess for the variables as data for MTK. If I remove the guess, the indexing works fine.
Edit, more info: if the guess is provided as a scalar this works properly.

function testsymarray()
    @variables begin
        b(t)[1:10, 1:10, 1:10], [guess = fill(0.0, 10, 10, 10), irreducible=true]
    end 

    var_tuple = (b = b,)

    eqs = Equation[]

    append!(eqs, somefunction(var_tuple))
end

function somefunction(var_tuple)
    (; b) = var_tuple

    b_first = b[1:end,1,1]

    return Symbolics.scalarize(b_first .~ 0.0)
end

testsymarray()

ERROR: ArgumentError: invalid index: i of type SymbolicUtils.BasicSymbolic{Int64}
Stacktrace:
  [1] to_index(i::SymbolicUtils.BasicSymbolic{Int64})
    @ Base ./indices.jl:315
  [2] to_index(A::Array{Float64, 3}, i::SymbolicUtils.BasicSymbolic{Int64})
    @ Base ./indices.jl:292
  [3] to_indices
    @ ./indices.jl:368 [inlined]
  [4] to_indices
    @ ./indices.jl:359 [inlined]
  [5] getindex(::Array{Float64, 3}, ::SymbolicUtils.BasicSymbolic{Int64}, ::Int64, ::Int64)
    @ Base ./abstractarray.jl:1312
  [6] (::Symbolics.var"#229#231"{…})(::SymbolicUtils.BasicSymbolic{…}, ::SymbolicUtils.BasicSymbolic{…}, ::SymbolicUtils.BasicSymbolic{…}, ::Vararg{…})
    @ Symbolics ~/.julia/packages/Symbolics/B6Z8m/src/variable.jl:39
  [7] (::Symbolics.var"#329#330"{…})(::SymbolicUtils.BasicSymbolic{…}, ::SymbolicUtils.BasicSymbolic{…}, ::Vararg{…})
    @ Symbolics ~/.julia/packages/Symbolics/B6Z8m/src/array-lib.jl:12
  [8] getindex(::SymbolicUtils.BasicSymbolic{Array{Real, 3}}, ::SymbolicUtils.BasicSymbolic{Int64}, ::Int64, ::Int64)
    @ Symbolics ~/.julia/packages/Symbolics/B6Z8m/src/array-lib.jl:86
  [9] getindex(::SymbolicUtils.BasicSymbolic{Array{Real, 3}}, ::UnitRange{Int64}, ::Int64, ::Int64)
    @ Symbolics ~/.julia/packages/Symbolics/B6Z8m/src/array-lib.jl:76
 [10] getindex(::Symbolics.Arr{Num, 3}, ::UnitRange{Int64}, ::Int64, ::Int64)
    @ Symbolics ~/.julia/packages/Symbolics/B6Z8m/src/array-lib.jl:94
2

Open an issue. By eye it looks like it works, but it requires digging in so it should go into the issue tracker.

3

Issue here: