Multiple dispatch with register_symbolic not working on v11

[mx-p9a]

Multiple dispatch for parameter structs worked in v10, but is not working in v11.
I created a very simple example where depending on the parameter struct, the density changes (as a function of time).

Minimal Reproducible Example 👇

#=
MWE: @register_symbolic with function overloading (multiple dispatch)

Demonstrates registering multiple methods of the same function with different 
type parameters, then using them in an MTK model where the concrete type is 
passed as a parameter.

Works in MTK v10, fails in v11.
=#

using ModelingToolkit
using ModelingToolkit: t_nounits as t, D_nounits as D
using Symbolics: @register_symbolic

abstract type AbstractRock end

struct SolidRock <: AbstractRock
    base_density::Float64
end

struct IceRock <: AbstractRock
    base_density::Float64
    melt_rate::Float64
end

# SolidRock: constant density
function get_density(rock::SolidRock, time)
    return rock.base_density
end

# IceRock: density decays with time (melting)
function get_density(rock::IceRock, time)
    return rock.base_density * exp(-rock.melt_rate * time)
end

# Register both methods
@register_symbolic get_density(rock::SolidRock, time)
@register_symbolic get_density(rock::IceRock, time) false

function FallingRock(input_rock::RockType; name) where {RockType <: AbstractRock}
    @parameters begin
        rock::RockType = input_rock
        volume = 1.0
        g = 9.81
    end

    @variables begin
        z(t) = 10.0  # initial height
        v(t) = 0.0   # initial velocity
        density(t)
        mass(t)
    end

    eqs = [density ~ get_density(rock, t)
           mass ~ density * volume
           D(z) ~ v
           D(v) ~ -g]

    return System(eqs, t; name)
end

solid = SolidRock(2700.0)
@mtkcompile rock1 = FallingRock(solid)
println("SolidRock model created successfully!")

ice = IceRock(900.0, 0.1)
@mtkcompile rock2 = FallingRock(ice)
println("IceRock model created successfully!")

Error & Stacktrace ⚠️

ERROR: LoadError: AssertionError: (SymbolicUtils.symtype)(rock) <: IceRock
Stacktrace:
 [1] get_density(rock::SymbolicUtils.BasicSymbolicImpl.var"typeof(BasicSymbolicImpl)"{SymReal}, time::Num)
   @ Main ~/.julia/packages/Symbolics/R0HIP/src/wrapper-types.jl:185
 [2] FallingRock(input_rock::SolidRock; name::Symbol)
   @ Main ~/code/scepter/ScepterMTK.jl/mwe_register_symbolic_overload.jl:54
 [3] top-level scope
   @ ~/.julia/packages/ModelingToolkitBase/Ylh9H/src/systems/abstractsystem.jl:2420
 [4] include(mapexpr::Function, mod::Module, _path::String)
   @ Base ./Base.jl:307
 [5] top-level scope
   @ REPL[5]:1

Not Working Environment (please complete the following information):

• Output of using Pkg; Pkg.status()

    [961ee093] ModelingToolkit v11.1.0
  [0c5d862f] Symbolics v7.2.0

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

   [47edcb42] ADTypes v1.20.0
  [6e696c72] AbstractPlutoDingetjes v1.3.2
  [1520ce14] AbstractTrees v0.4.5
  [7d9f7c33] Accessors v0.1.43
  [79e6a3ab] Adapt v4.4.0
  [ec485272] ArnoldiMethod v0.4.0
  [4fba245c] ArrayInterface v7.22.0
  [4c555306] ArrayLayouts v1.12.2
  [e2ed5e7c] Bijections v0.2.2
  [caf10ac8] BipartiteGraphs v0.1.4
  [62783981] BitTwiddlingConvenienceFunctions v0.1.6
  [8e7c35d0] BlockArrays v1.9.3
  [70df07ce] BracketingNonlinearSolve v1.6.0
  [2a0fbf3d] CPUSummary v0.2.7
  [fb6a15b2] CloseOpenIntervals v0.1.13
⌅ [861a8166] Combinatorics v1.0.2
  [38540f10] CommonSolve v0.2.4
  [bbf7d656] CommonSubexpressions v0.3.1
  [f70d9fcc] CommonWorldInvalidations v1.0.0
  [34da2185] Compat v4.18.1
  [b152e2b5] CompositeTypes v0.1.4
  [a33af91c] CompositionsBase v0.1.2
  [2569d6c7] ConcreteStructs v0.2.3
  [187b0558] ConstructionBase v1.6.0
  [adafc99b] CpuId v0.3.1
  [864edb3b] DataStructures v0.19.3
  [2b5f629d] DiffEqBase v6.192.0
  [459566f4] DiffEqCallbacks v4.10.1
  [163ba53b] DiffResults v1.1.0
  [b552c78f] DiffRules v1.15.1
  [a0c0ee7d] DifferentiationInterface v0.7.12
  [ffbed154] DocStringExtensions v0.9.5
  [5b8099bc] DomainSets v0.7.16
  [7c1d4256] DynamicPolynomials v0.6.4
  [4e289a0a] EnumX v1.0.5
  [f151be2c] EnzymeCore v0.8.17
  [e2ba6199] ExprTools v0.1.10
  [55351af7] ExproniconLite v0.10.14
  [7034ab61] FastBroadcast v0.3.5
  [9aa1b823] FastClosures v0.3.2
  [a4df4552] FastPower v1.2.0
  [1a297f60] FillArrays v1.15.0
  [64ca27bc] FindFirstFunctions v1.4.2
  [6a86dc24] FiniteDiff v2.29.0
  [f6369f11] ForwardDiff v1.3.0
  [069b7b12] FunctionWrappers v1.1.3
  [77dc65aa] FunctionWrappersWrappers v0.1.3
  [46192b85] GPUArraysCore v0.2.0
  [86223c79] Graphs v1.13.2
  [615f187c] IfElse v0.1.1
⌃ [3263718b] ImplicitDiscreteSolve v1.2.0
  [d25df0c9] Inflate v0.1.5
  [18e54dd8] IntegerMathUtils v0.1.3
  [8197267c] IntervalSets v0.7.13
  [3587e190] InverseFunctions v0.1.17
  [92d709cd] IrrationalConstants v0.2.6
  [82899510] IteratorInterfaceExtensions v1.0.0
  [692b3bcd] JLLWrappers v1.7.1
  [ae98c720] Jieko v0.2.1
  [ccbc3e58] JumpProcesses v9.19.3
  [10f19ff3] LayoutPointers v0.1.17
  [87fe0de2] LineSearch v0.1.4
  [2ab3a3ac] LogExpFunctions v0.3.29
  [e6f89c97] LoggingExtras v1.2.0
  [1914dd2f] MacroTools v0.5.16
  [d125e4d3] ManualMemory v0.1.8
  [bb5d69b7] MaybeInplace v0.1.4
  [961ee093] ModelingToolkit v11.1.0
  [7771a370] ModelingToolkitBase v1.2.0
  [6bb917b9] ModelingToolkitTearing v1.1.0
  [2e0e35c7] Moshi v0.3.7
  [46d2c3a1] MuladdMacro v0.2.4
  [102ac46a] MultivariatePolynomials v0.5.13
  [d8a4904e] MutableArithmetics v1.6.7
  [77ba4419] NaNMath v1.1.3
  [be0214bd] NonlinearSolveBase v2.5.0
  [6fe1bfb0] OffsetArrays v1.17.0
  [bac558e1] OrderedCollections v1.8.1
⌅ [bbf590c4] OrdinaryDiffEqCore v1.36.0
  [e409e4f3] PoissonRandom v0.4.7
  [f517fe37] Polyester v0.7.18
  [1d0040c9] PolyesterWeave v0.2.2
  [d236fae5] PreallocationTools v0.4.34
  [aea7be01] PrecompileTools v1.3.3
  [21216c6a] Preferences v1.5.0
  [27ebfcd6] Primes v0.5.7
  [988b38a3] ReadOnlyArrays v0.2.0
  [795d4caa] ReadOnlyDicts v1.0.0
  [3cdcf5f2] RecipesBase v1.3.4
  [731186ca] RecursiveArrayTools v3.40.0
  [189a3867] Reexport v1.2.2
  [ae029012] Requires v1.3.1
  [7e49a35a] RuntimeGeneratedFunctions v0.5.16
  [9dfe8606] SCCNonlinearSolve v1.6.0
  [94e857df] SIMDTypes v0.1.0
  [0bca4576] SciMLBase v2.128.0
  [19f34311] SciMLJacobianOperators v0.1.11
  [a6db7da4] SciMLLogging v1.7.1
  [c0aeaf25] SciMLOperators v1.14.1
  [431bcebd] SciMLPublic v1.0.0
  [53ae85a6] SciMLStructures v1.7.0
  [efcf1570] Setfield v1.1.2
  [727e6d20] SimpleNonlinearSolve v2.9.0
  [699a6c99] SimpleTraits v0.9.5
  [ce78b400] SimpleUnPack v1.1.0
  [276daf66] SpecialFunctions v2.6.1
  [64909d44] StateSelection v1.2.0
  [aedffcd0] Static v1.3.1
  [0d7ed370] StaticArrayInterface v1.8.0
  [90137ffa] StaticArrays v1.9.15
  [1e83bf80] StaticArraysCore v1.4.4
  [10745b16] Statistics v1.11.1
  [7792a7ef] StrideArraysCore v0.5.8
  [2efcf032] SymbolicIndexingInterface v0.3.46
  [19f23fe9] SymbolicLimits v0.2.4
  [d1185830] SymbolicUtils v4.9.1
  [0c5d862f] Symbolics v7.2.0
  [ed4db957] TaskLocalValues v0.1.3
  [8ea1fca8] TermInterface v2.0.0
  [8290d209] ThreadingUtilities v0.5.5
  [a759f4b9] TimerOutputs v0.5.29
  [781d530d] TruncatedStacktraces v1.4.0
  [3a884ed6] UnPack v1.0.2
  [d30d5f5c] WeakCacheSets v0.1.0
  [efe28fd5] OpenSpecFun_jll v0.5.6+0
  [0dad84c5] ArgTools v1.1.2
  [56f22d72] Artifacts v1.11.0
  [2a0f44e3] Base64 v1.11.0
  [ade2ca70] Dates v1.11.0
  [8ba89e20] Distributed v1.11.0
  [f43a241f] Downloads v1.7.0
  [7b1f6079] FileWatching v1.11.0
  [9fa8497b] Future v1.11.0
  [b77e0a4c] InteractiveUtils v1.11.0
  [ac6e5ff7] JuliaSyntaxHighlighting v1.12.0
  [b27032c2] LibCURL v0.6.4
  [76f85450] LibGit2 v1.11.0
  [8f399da3] Libdl v1.11.0
  [37e2e46d] LinearAlgebra v1.12.0
  [56ddb016] Logging v1.11.0
  [d6f4376e] Markdown v1.11.0
  [ca575930] NetworkOptions v1.3.0
  [44cfe95a] Pkg v1.12.0
  [de0858da] Printf v1.11.0
  [3fa0cd96] REPL v1.11.0
  [9a3f8284] Random v1.11.0
  [ea8e919c] SHA v0.7.0
  [9e88b42a] Serialization v1.11.0
  [6462fe0b] Sockets v1.11.0
  [2f01184e] SparseArrays v1.12.0
  [f489334b] StyledStrings v1.11.0
  [fa267f1f] TOML v1.0.3
  [a4e569a6] Tar v1.10.0
  [8dfed614] Test v1.11.0
  [cf7118a7] UUIDs v1.11.0
  [4ec0a83e] Unicode v1.11.0
  [e66e0078] CompilerSupportLibraries_jll v1.3.0+1
  [deac9b47] LibCURL_jll v8.15.0+0
  [e37daf67] LibGit2_jll v1.9.0+0
  [29816b5a] LibSSH2_jll v1.11.3+1
  [14a3606d] MozillaCACerts_jll v2025.5.20
  [4536629a] OpenBLAS_jll v0.3.29+0
  [05823500] OpenLibm_jll v0.8.7+0
  [458c3c95] OpenSSL_jll v3.5.4+0
  [bea87d4a] SuiteSparse_jll v7.8.3+2
  [83775a58] Zlib_jll v1.3.1+2
  [8e850b90] libblastrampoline_jll v5.15.0+0
  [8e850ede] nghttp2_jll v1.64.0+1
  [3f19e933] p7zip_jll v17.7.0+0

• Output of versioninfo()

Julia Version 1.12.2
Commit ca9b6662be4 (2025-11-20 16:25 UTC)
Build Info:
  Official https://julialang.org release
Platform Info:
  OS: macOS (arm64-apple-darwin24.0.0)
  CPU: 12 × Apple M2 Max
  WORD_SIZE: 64
  LLVM: libLLVM-18.1.7 (ORCJIT, apple-m2)
  GC: Built with stock GC
Threads: 1 default, 1 interactive, 1 GC (on 8 virtual cores)
Environment:
  JULIA_PKG_USE_CLI_GIT = true

Working Environment (please complete the following information):

• Output of using Pkg; Pkg.status()

⌃ [961ee093] ModelingToolkit v10.31.2
⌅ [0c5d862f] Symbolics v6.58.0

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

  [47edcb42] ADTypes v1.20.0
  [1520ce14] AbstractTrees v0.4.5
  [7d9f7c33] Accessors v0.1.43
  [79e6a3ab] Adapt v4.4.0
  [66dad0bd] AliasTables v1.1.3
  [ec485272] ArnoldiMethod v0.4.0
  [4fba245c] ArrayInterface v7.22.0
  [4c555306] ArrayLayouts v1.12.2
  [e2ed5e7c] Bijections v0.2.2
  [62783981] BitTwiddlingConvenienceFunctions v0.1.6
  [8e7c35d0] BlockArrays v1.9.3
  [70df07ce] BracketingNonlinearSolve v1.6.0
  [2a0fbf3d] CPUSummary v0.2.7
  [d360d2e6] ChainRulesCore v1.26.0
  [fb6a15b2] CloseOpenIntervals v0.1.13
⌅ [861a8166] Combinatorics v1.0.2
  [a80b9123] CommonMark v0.9.1
  [38540f10] CommonSolve v0.2.4
  [bbf7d656] CommonSubexpressions v0.3.1
  [f70d9fcc] CommonWorldInvalidations v1.0.0
  [34da2185] Compat v4.18.1
  [b152e2b5] CompositeTypes v0.1.4
  [a33af91c] CompositionsBase v0.1.2
  [2569d6c7] ConcreteStructs v0.2.3
  [187b0558] ConstructionBase v1.6.0
  [adafc99b] CpuId v0.3.1
  [9a962f9c] DataAPI v1.16.0
  [864edb3b] DataStructures v0.19.3
  [2b5f629d] DiffEqBase v6.192.0
  [459566f4] DiffEqCallbacks v4.10.1
  [77a26b50] DiffEqNoiseProcess v5.24.1
  [163ba53b] DiffResults v1.1.0
  [b552c78f] DiffRules v1.15.1
  [a0c0ee7d] DifferentiationInterface v0.7.12
  [8d63f2c5] DispatchDoctor v0.4.26
  [31c24e10] Distributions v0.25.122
  [ffbed154] DocStringExtensions v0.9.5
  [5b8099bc] DomainSets v0.7.16
  [7c1d4256] DynamicPolynomials v0.6.4
  [06fc5a27] DynamicQuantities v1.10.0
  [4e289a0a] EnumX v1.0.5
  [f151be2c] EnzymeCore v0.8.17
  [e2ba6199] ExprTools v0.1.10
  [55351af7] ExproniconLite v0.10.14
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  [9aa1b823] FastClosures v0.3.2
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  [64ca27bc] FindFirstFunctions v1.4.2
  [6a86dc24] FiniteDiff v2.29.0
  [1fa38f19] Format v1.3.7
  [f6369f11] ForwardDiff v1.3.0
  [069b7b12] FunctionWrappers v1.1.3
  [77dc65aa] FunctionWrappersWrappers v0.1.3
  [46192b85] GPUArraysCore v0.2.0
  [c27321d9] Glob v1.4.0
  [86223c79] Graphs v1.13.2
  [34004b35] HypergeometricFunctions v0.3.28
  [615f187c] IfElse v0.1.1
  [3263718b] ImplicitDiscreteSolve v1.3.0
  [d25df0c9] Inflate v0.1.5
  [18e54dd8] IntegerMathUtils v0.1.3
  [8197267c] IntervalSets v0.7.13
  [3587e190] InverseFunctions v0.1.17
  [92d709cd] IrrationalConstants v0.2.6
  [82899510] IteratorInterfaceExtensions v1.0.0
  [692b3bcd] JLLWrappers v1.7.1
  [ae98c720] Jieko v0.2.1
  [98e50ef6] JuliaFormatter v2.2.0
⌅ [70703baa] JuliaSyntax v0.4.10
  [ccbc3e58] JumpProcesses v9.19.3
  [b964fa9f] LaTeXStrings v1.4.0
  [23fbe1c1] Latexify v0.16.10
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  [87fe0de2] LineSearch v0.1.4
  [d3d80556] LineSearches v7.5.1
  [2ab3a3ac] LogExpFunctions v0.3.29
  [e6f89c97] LoggingExtras v1.2.0
  [d8e11817] MLStyle v0.4.17
  [1914dd2f] MacroTools v0.5.16
  [d125e4d3] ManualMemory v0.1.8
  [bb5d69b7] MaybeInplace v0.1.4
  [e1d29d7a] Missings v1.2.0
⌃ [961ee093] ModelingToolkit v10.31.2
  [2e0e35c7] Moshi v0.3.7
  [46d2c3a1] MuladdMacro v0.2.4
  [102ac46a] MultivariatePolynomials v0.5.13
  [d8a4904e] MutableArithmetics v1.6.7
  [d41bc354] NLSolversBase v7.10.0
  [77ba4419] NaNMath v1.1.3
  [be0214bd] NonlinearSolveBase v2.5.0
  [6fe1bfb0] OffsetArrays v1.17.0
  [429524aa] Optim v1.13.3
  [bac558e1] OrderedCollections v1.8.1
  [bbf590c4] OrdinaryDiffEqCore v2.0.0
  [90014a1f] PDMats v0.11.36
  [e409e4f3] PoissonRandom v0.4.7
  [f517fe37] Polyester v0.7.18
  [1d0040c9] PolyesterWeave v0.2.2
  [85a6dd25] PositiveFactorizations v0.2.4
  [d236fae5] PreallocationTools v0.4.34
  [aea7be01] PrecompileTools v1.3.3
  [21216c6a] Preferences v1.5.0
  [27ebfcd6] Primes v0.5.7
  [43287f4e] PtrArrays v1.3.0
  [1fd47b50] QuadGK v2.11.2
  [74087812] Random123 v1.7.1
  [e6cf234a] RandomNumbers v1.6.0
  [3cdcf5f2] RecipesBase v1.3.4
  [731186ca] RecursiveArrayTools v3.40.0
  [189a3867] Reexport v1.2.2
  [ae029012] Requires v1.3.1
  [ae5879a3] ResettableStacks v1.1.1
  [79098fc4] Rmath v0.9.0
  [7e49a35a] RuntimeGeneratedFunctions v0.5.16
  [9dfe8606] SCCNonlinearSolve v1.6.0
  [94e857df] SIMDTypes v0.1.0
  [0bca4576] SciMLBase v2.128.0
  [19f34311] SciMLJacobianOperators v0.1.11
  [a6db7da4] SciMLLogging v1.7.1
  [c0aeaf25] SciMLOperators v1.14.1
  [431bcebd] SciMLPublic v1.0.0
  [53ae85a6] SciMLStructures v1.7.0
  [efcf1570] Setfield v1.1.2
  [727e6d20] SimpleNonlinearSolve v2.9.0
  [699a6c99] SimpleTraits v0.9.5
  [a2af1166] SortingAlgorithms v1.2.2
  [276daf66] SpecialFunctions v2.6.1
  [aedffcd0] Static v1.3.1
  [0d7ed370] StaticArrayInterface v1.8.0
  [90137ffa] StaticArrays v1.9.15
  [1e83bf80] StaticArraysCore v1.4.4
  [10745b16] Statistics v1.11.1
  [82ae8749] StatsAPI v1.8.0
  [2913bbd2] StatsBase v0.34.9
  [4c63d2b9] StatsFuns v1.5.2
  [7792a7ef] StrideArraysCore v0.5.8
  [2efcf032] SymbolicIndexingInterface v0.3.46
⌃ [19f23fe9] SymbolicLimits v0.2.3
⌅ [d1185830] SymbolicUtils v3.32.0
⌅ [0c5d862f] Symbolics v6.58.0
  [ed4db957] TaskLocalValues v0.1.3
  [8ea1fca8] TermInterface v2.0.0
  [1c621080] TestItems v1.0.0
  [8290d209] ThreadingUtilities v0.5.5
  [a759f4b9] TimerOutputs v0.5.29
  [410a4b4d] Tricks v0.1.13
  [781d530d] TruncatedStacktraces v1.4.0
  [5c2747f8] URIs v1.6.1
  [3a884ed6] UnPack v1.0.2
  [1986cc42] Unitful v1.27.0
  [a7c27f48] Unityper v0.1.6
  [61579ee1] Ghostscript_jll v9.55.1+0
  [aacddb02] JpegTurbo_jll v3.1.4+0
  [efe28fd5] OpenSpecFun_jll v0.5.6+0
  [f50d1b31] Rmath_jll v0.5.1+0
  [56f22d72] Artifacts v1.11.0
  [2a0f44e3] Base64 v1.11.0
  [ade2ca70] Dates v1.11.0
  [8ba89e20] Distributed v1.11.0
  [9fa8497b] Future v1.11.0
  [b77e0a4c] InteractiveUtils v1.11.0
  [ac6e5ff7] JuliaSyntaxHighlighting v1.12.0
  [8f399da3] Libdl v1.11.0
  [37e2e46d] LinearAlgebra v1.12.0
  [56ddb016] Logging v1.11.0
  [d6f4376e] Markdown v1.11.0
  [de0858da] Printf v1.11.0
  [9a3f8284] Random v1.11.0
  [ea8e919c] SHA v0.7.0
  [9e88b42a] Serialization v1.11.0
  [6462fe0b] Sockets v1.11.0
  [2f01184e] SparseArrays v1.12.0
  [f489334b] StyledStrings v1.11.0
  [4607b0f0] SuiteSparse
  [fa267f1f] TOML v1.0.3
  [8dfed614] Test v1.11.0
  [cf7118a7] UUIDs v1.11.0
  [4ec0a83e] Unicode v1.11.0
  [e66e0078] CompilerSupportLibraries_jll v1.3.0+1
  [4536629a] OpenBLAS_jll v0.3.29+0
  [05823500] OpenLibm_jll v0.8.7+0
  [bea87d4a] SuiteSparse_jll v7.8.3+2
  [83775a58] Zlib_jll v1.3.1+2
  [8e850b90] libblastrampoline_jll v5.15.0+0

• Output of versioninfo()

Julia Version 1.12.2
Commit ca9b6662be4 (2025-11-20 16:25 UTC)
Build Info:
  Official https://julialang.org release
Platform Info:
  OS: macOS (arm64-apple-darwin24.0.0)
  CPU: 12 × Apple M2 Max
  WORD_SIZE: 64
  LLVM: libLLVM-18.1.7 (ORCJIT, apple-m2)
  GC: Built with stock GC
Threads: 1 default, 1 interactive, 1 GC (on 8 virtual cores)
Environment:
  JULIA_PKG_USE_CLI_GIT = true

Additional context

It doesn't seem like the Symbolics functionality around multiple dispatch has changed in Symbolics v7.

I'm also open to other syntax around this.