Vector of parameters in PDE system @parameters DU[1:2] fail to discretize

[dmetivie]

Describe the bug 🐞
When using a vector of parameters @parameters DU[1:2]::Float64, the discretize function of a PDE problem fails with a mysterious error message. The same problem with 2 distinct parameters @parameters D, U works.
Is the syntax wrong? I did not find documentation for this case except in this FAQ . Maybe it is a problem from ModelingToolkit (I suspect other issues with remake and @parameters).

Expected behavior

The same problem with 2 distinct parameters @parameters D, U works. The syntax with vector should work.

Minimal Reproducible Example 👇

using ModelingToolkit: Interval
using ModelingToolkit
using DifferentialEquations
using MethodOfLines
# Variables
@independent_variables x,t
@variables c(..)
∂t = Differential(t)
∂²x = Differential(x)^2
∂x = Differential(x)
# Space and time domains
L = 3.0
T = 3.0
dom = [x ∈ Interval(0, L), t ∈ Interval(0, T)]
# Initial and boundary conditions
bcs = [
    c(0, t) ~ 1.0,
    c(x, 0) ~ 0.0,
]
# Parameters
@parameters DU[1:2]::Float64
# PDE
eqn = ∂t(c(x, t)) ~ DU[1] * ∂²x(c(x, t)) - DU[2] * ∂x(c(x, t))
# Define PDE system
@named sys = PDESystem(eqn,
    bcs,
    dom,
    [x, t],
    [c(x, t)],
    DU;
    defaults=Dict(DU => [0.1, 1.2])
)

# Define ODE problem
prob = discretize(sys,
    MOLFiniteDifference([x => 0.05],
        t,
        advection_scheme=scheme = UpwindScheme(2)
    )
)

Error & Stacktrace ⚠️

ERROR: MethodError: Cannot `convert` an object of type 
  Vector{Int64} to an object of type
  AbstractRange
The function `convert` exists, but no method is defined for this combination of argument types.

Closest candidates are:
  convert(::Type{T}, ::T) where T
   @ Base Base.jl:126
  convert(::Type{SL}, ::FillArrays.AbstractFill{T, 1} where T) where SL<:AbstractRange
   @ FillArrays C:\Users\metivier\.julia\packages\FillArrays\lVl4c\src\FillArrays.jl:567
  convert(::Type{T}, ::AbstractRange) where T<:AbstractRange
   @ Base range.jl:269
  ...

Stacktrace:
 [1] setindex!(h::Dict{…}, v0::Vector{…}, key::SymbolicUtils.BasicSymbolic{…})
   @ Base .\dict.jl:355
 [2] getindex(x::Symbolics.ArrayOp{Vector{Real}}, idx::Vector{Int64})
   @ Symbolics C:\Users\metivier\.julia\packages\Symbolics\YbNrd\src\array-lib.jl:67
 [3] getindex(x::Symbolics.Arr{Num, 1}, idx::Vector{Int64})
   @ Symbolics C:\Users\metivier\.julia\packages\Symbolics\YbNrd\src\array-lib.jl:94
 [4] ODESystem(deqs::Vector{…}, iv::Num, dvs::Vector{…}, ps::Symbolics.Arr{…}; controls::Vector{…}, observed::Vector{…}, systems::Vector{…}, tspan::Nothing, name::Symbol, description::String, default_u0::Dict{…}, default_p::Dict{…}, defaults::Dict{…}, guesses::Dict{…}, initializesystem::Nothing, initialization_eqs::Vector{…}, schedule::Nothing, connector_type::Nothing, preface::Nothing, continuous_events::Nothing, discrete_events::Nothing, parameter_dependencies::Vector{…}, checks::Bool, metadata::MethodOfLines.MOLMetadata{…}, gui_metadata::Nothing, is_dde::Nothing, tstops::Vector{…})
   @ ModelingToolkit C:\Users\metivier\.julia\packages\ModelingToolkit\ompZE\src\systems\diffeqs\odesystem.jl:273
 [5] generate_system(disc_state::PDEBase.EquationState, s::MethodOfLines.DiscreteSpace{…}, u0::Vector{…}, tspan::Tuple{…}, metadata::MethodOfLines.MOLMetadata{…}, disc::MOLFiniteDifference{…})
   @ PDEBase C:\Users\metivier\.julia\packages\PDEBase\VVGPP\src\discretization_state.jl:40
 [6] symbolic_discretize(pdesys::PDESystem, discretization::MOLFiniteDifference{…})
   @ PDEBase C:\Users\metivier\.julia\packages\PDEBase\VVGPP\src\symbolic_discretize.jl:89
 [7] discretize(pdesys::PDESystem, discretization::MOLFiniteDifference{…}; analytic::Nothing, kwargs::@Kwargs{})
   @ PDEBase C:\Users\metivier\.julia\packages\PDEBase\VVGPP\src\discretization_state.jl:57
 [8] discretize(pdesys::PDESystem, discretization::MOLFiniteDifference{…})
   @ PDEBase C:\Users\metivier\.julia\packages\PDEBase\VVGPP\src\discretization_state.jl:54
 [9] top-level scope
   @ c:\Users\metivier\Dropbox\PC (2)\Documents\GitLab\thesis_yoann_cartier\Code\inverse\mwe_yoann_diffeqestim_heat_eqt_mtk.jl:36
Some type information was truncated. Use `show(err)` to see complete types.

Environment (please complete the following information):

• Output of using Pkg; Pkg.status()

  [0c46a032] DifferentialEquations v7.15.0
  [94925ecb] MethodOfLines v0.11.7
  [961ee093] ModelingToolkit v9.53.0