Array parameters are not correctly scoped with ParentScope

[contradict]

This used to work in ModelingToolkit 8.65.0 but stopped in 8.66.0.

@parameters a[1:2]=[1, 2] b=4 c=1
@variables t x(t)=ParentScope(a[1]) y(t)=ParentScope(b)
D = Differential(t)
@named level0 = ODESystem([D(x)~ParentScope(a[2]),
                           D(y)~ParentScope(c)], t, [x, y], [])
level1 = ODESystem(Equation[], t, [], [a..., b, c]; name=:level1) ∘ level0
level1 = structural_simplify(level1)
prob = ODEProblem(level1, [], (0, 1))

The first signs of trouble appear here, level0₊a[1] should not exist because of ParentScope, but the initial condition for y is scoped correctly.

julia> level1 = structural_simplify(level1)
Model level1 with 2 equations
States (2):
  level0₊x(t) [defaults to level0₊a[1]]
  level0₊y(t) [defaults to b]
Parameters (4):
  a[1] [defaults to 1]
  a[2] [defaults to 2]
  b [defaults to 4]
  c [defaults to 1]
Incidence matrix:2×4 SparseArrays.SparseMatrixCSC{Num, Int64} with 2 stored entries:
 ⋅  ⋅  ×  ⋅
 ⋅  ⋅  ⋅  ×

The equations show the same pattern

julia> equations(level1)
2-element Vector{Equation}:
 Differential(t)(level0₊x(t)) ~ level0₊a[2]
 Differential(t)(level0₊y(t)) ~ c

And constructing a problem fails.

julia> prob = ODEProblem(level1, [], (0, 1))
ERROR: ArgumentError: Any[level0₊a[1]] are either missing from the variable map or missing from the system's states/parameters list.
Stacktrace:
  [1] throw_missingvars_in_sys(vars::Vector{Any})
    @ ModelingToolkit ~/.julia/packages/ModelingToolkit/dkLCE/src/utils.jl:642
  [2] promote_to_concrete(vs::Vector{Any}; tofloat::Bool, use_union::Bool)
    @ ModelingToolkit ~/.julia/packages/ModelingToolkit/dkLCE/src/utils.jl:654
  [3] varmap_to_vars(varmap::Vector{Any}, varlist::Vector{Any}; defaults::Dict{Any, Any}, check::Bool, toterm::Function, promotetoconcrete::Nothing, tofloat::Bool, use_union::Bool)
    @ ModelingToolkit ~/.julia/packages/ModelingToolkit/dkLCE/src/variables.jl:92
  [4] get_u0_p(sys::ODESystem, u0map::Vector{Any}, parammap::SciMLBase.NullParameters; use_union::Bool, tofloat::Bool, symbolic_u0::Bool)
    @ ModelingToolkit ~/.julia/packages/ModelingToolkit/dkLCE/src/systems/diffeqs/abstractodesystem.jl:700
  [5] get_u0_p
    @ ~/.julia/packages/ModelingToolkit/dkLCE/src/systems/diffeqs/abstractodesystem.jl:684 [inlined]
  [6] process_DEProblem(constructor::Type, sys::ODESystem, u0map::Vector{Any}, parammap::SciMLBase.NullParameters; implicit_dae::Bool, du0map::Nothing, version::Nothing, tgrad::Bool, jac::Bool, checkbounds::Bool, sparse::Bool, simplify::Bool, linenumbers::Bool, parallel::Symbolics.SerialForm, eval_expression::Bool, use_union::Bool, tofloat::Bool, symbolic_u0::Bool, kwargs::Base.Pairs{Symbol, Integer, Tuple{Symbol, Symbol, Symbol}, NamedTuple{(:t, :has_difference, :check_length), Tuple{Int64, Bool, Bool}}})
    @ ModelingToolkit ~/.julia/packages/ModelingToolkit/dkLCE/src/systems/diffeqs/abstractodesystem.jl:724
  [7] (ODEProblem{true, SciMLBase.AutoSpecialize})(sys::ODESystem, u0map::Vector{Any}, tspan::Tuple{Int64, Int64}, parammap::SciMLBase.NullParameters; callback::Nothing, check_length::Bool, kwargs::Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
    @ ModelingToolkit ~/.julia/packages/ModelingToolkit/dkLCE/src/systems/diffeqs/abstractodesystem.jl:834
  [8] ODEProblem
    @ ~/.julia/packages/ModelingToolkit/dkLCE/src/systems/diffeqs/abstractodesystem.jl:827 [inlined]
  [9] (ODEProblem{true, SciMLBase.AutoSpecialize})(sys::ODESystem, u0map::Vector{Any}, tspan::Tuple{Int64, Int64})
    @ ModelingToolkit ~/.julia/packages/ModelingToolkit/dkLCE/src/systems/diffeqs/abstractodesystem.jl:827
 [10] (ODEProblem{true})(::ODESystem, ::Vector{Any}, ::Vararg{Any}; kwargs::Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
    @ ModelingToolkit ~/.julia/packages/ModelingToolkit/dkLCE/src/systems/diffeqs/abstractodesystem.jl:814
 [11] (ODEProblem{true})(::ODESystem, ::Vector{Any}, ::Vararg{Any})
    @ ModelingToolkit ~/.julia/packages/ModelingToolkit/dkLCE/src/systems/diffeqs/abstractodesystem.jl:813
 [12] ODEProblem(::ODESystem, ::Vector{Any}, ::Vararg{Any}; kwargs::Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
    @ ModelingToolkit ~/.julia/packages/ModelingToolkit/dkLCE/src/systems/diffeqs/abstractodesystem.jl:810
 [13] ODEProblem(::ODESystem, ::Vector{Any}, ::Vararg{Any})
    @ ModelingToolkit ~/.julia/packages/ModelingToolkit/dkLCE/src/systems/diffeqs/abstractodesystem.jl:809
 [14] top-level scope
    @ REPL[135]:1

[ChrisRackauckas]

This is likely caused by #2247. I must've missed a case with handling array variables in the scoping recursion. I will likely take a look Saturday.

[contradict]

I did some more poking at this one, I think the problem is actually in Symbolics. By the time namespace_expr is called, the SymScope metadata is gone. This code here rebuilds the indexed array from the array and the index, but the metadata was attached to the Term and is lost.

[contradict]

@ChrisRackauckas I think I have fixed this with JuliaSymbolics/Symbolics.jl#1010 and #2352

[ChrisRackauckas]

I think the solution generally looks fine, I just want to check with @YingboMa that the metadata for a scalar arrived from an array should propagate the same one, or if we want to amend it a bit.