DEF in parameters

[aml5600]

Describe the bug 🐞

Looks like a DEF slips by when completing a system with split = true, but flatten = false.

Expected behavior

No DEF in parameters

Minimal Reproducible Example 👇

using ModelingToolkit
using ModelingToolkit: t_nounits as t, D_nounits as D

@mtkmodel SubSystem begin
    @parameters begin
        c = 1
    end
    @variables begin
        x(t)
    end
    @equations begin
        D(x) ~ c * x
    end
end

@mtkmodel System begin
    @components begin
        subsys = SubSystem()
    end
    @parameters begin
        k = 1
    end
    @variables begin
        y(t)
    end
    @equations begin
        D(y) ~ k * y + subsys.x
    end
end

@named sys = System()

sys1 = complete(sys; split = false, flatten = true)
sys2 = complete(sys; split = true, flatten = true)
sys3 = complete(sys; split = false, flatten = false)
sys4 = complete(sys; split = true, flatten = false)

parameters(sys1) # Vector{Any}[k, subsys₊c]
parameters(sys2) # Vector{Any}[k, subsys₊c]
parameters(sys3) # Vector{Any}[k, subsys₊c]
parameters(sys4) # Vector{Any}[k, DEF, subsys₊c]

Environment (please complete the following information):

• Output of using Pkg; Pkg.status()

ulia> Pkg.status()
Project ModelingToolkit v9.64.0
Status `~/workspace/ModelingToolkit.jl/Project.toml`
  [1520ce14] AbstractTrees v0.4.5
  [4fba245c] ArrayInterface v7.18.0
  [8e7c35d0] BlockArrays v1.4.0
  [861a8166] Combinatorics v1.0.2
  [38540f10] CommonSolve v0.2.4
  [34da2185] Compat v4.16.0
  [187b0558] ConstructionBase v1.5.8
  [864edb3b] DataStructures v0.18.20
  [2b5f629d] DiffEqBase v6.164.1
  [459566f4] DiffEqCallbacks v4.3.0
  [77a26b50] DiffEqNoiseProcess v5.24.1
  [b552c78f] DiffRules v1.15.1
  [31c24e10] Distributions v0.25.117
  [ffbed154] DocStringExtensions v0.9.3
  [5b8099bc] DomainSets v0.7.15
  [06fc5a27] DynamicQuantities v1.4.0
  [4e289a0a] EnumX v1.0.4
  [e2ba6199] ExprTools v0.1.10
⌅ [6b7a57c9] Expronicon v0.8.5
  [64ca27bc] FindFirstFunctions v1.4.1
  [f6369f11] ForwardDiff v0.10.38
  [069b7b12] FunctionWrappers v1.1.3
  [77dc65aa] FunctionWrappersWrappers v0.1.3
  [86223c79] Graphs v1.12.0
  [98e50ef6] JuliaFormatter v1.0.62
  [ccbc3e58] JumpProcesses v9.14.2
  [23fbe1c1] Latexify v0.16.6
  [d8e11817] MLStyle v0.4.17
  [77ba4419] NaNMath v1.1.2
  [8913a72c] NonlinearSolve v4.4.0
  [6fe1bfb0] OffsetArrays v1.15.0
  [bac558e1] OrderedCollections v1.8.0
  [aea7be01] PrecompileTools v1.2.1
  [731186ca] RecursiveArrayTools v3.29.0
  [189a3867] Reexport v1.2.2
  [7e49a35a] RuntimeGeneratedFunctions v0.5.13
  [9dfe8606] SCCNonlinearSolve v1.0.0
  [0bca4576] SciMLBase v2.74.1
  [53ae85a6] SciMLStructures v1.6.1
  [efcf1570] Setfield v1.1.1
  [727e6d20] SimpleNonlinearSolve v2.1.0
  [276daf66] SpecialFunctions v2.5.0
  [90137ffa] StaticArrays v1.9.12
  [2efcf032] SymbolicIndexingInterface v0.3.37
  [d1185830] SymbolicUtils v3.15.0
  [0c5d862f] Symbolics v6.29.1
  [5c2747f8] URIs v1.5.1
  [3a884ed6] UnPack v1.0.2
  [1986cc42] Unitful v1.22.0
  [8ba89e20] Distributed
  [b77e0a4c] InteractiveUtils
  [8f399da3] Libdl
  [37e2e46d] LinearAlgebra
  [9e88b42a] Serialization
  [2f01184e] SparseArrays v1.10.0

• Output of using Pkg; Pkg.status(; mode = PKGMODE_MANIFEST)

• Output of versioninfo()

julia> versioninfo()
Julia Version 1.10.8
Commit 4c16ff44be8 (2025-01-22 10:06 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (arm64-apple-darwin24.0.0)
  CPU: 8 × Apple M1 Pro
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, apple-m1)
Threads: 8 default, 0 interactive, 4 GC (on 6 virtual cores)
Environment:
  JULIA_EDITOR = code
  JULIA_NUM_THREADS = 8