Solution somehow corrupted with IfLifting

[mtiller-jh]

Describe the bug 🐞

Using IfLifting additional pass, I am not able to interpolate the solution beyond the first event.

Expected behavior

I should be able to interpolate the solution at all the the same time instants as I was able to when IfLifting was not being performed.

Minimal Reproducible Example 👇

using ModelingToolkit
using ModelingToolkit: t_nounits as t
using OrdinaryDiffEqDefault
using RuntimeGeneratedFunctions
RuntimeGeneratedFunctions.init(@__MODULE__)

D = Differential(t)

@component function Integrator(; name, x0=0, k=1)
    params = @parameters begin
        (x0::Float64 = x0), [description = "Initial value of the integrator state"]
        (k::Float64 = k), [description = "Gain"]
    end
    vars = @variables begin
        u(t), [input = true]
        y(t), [output = true]
        x(t), [description = "State of Integrator"]
    end
    initialization_eqs = [
        x ~ x0
    ]
    eqs = Equation[
        D(x) ~ k * u
        y ~ x
    ]
    return ODESystem(eqs, t, vars, params; systems=[], name, initialization_eqs)
end

@component function Cosine(; name, start_time=0, offset=0, amplitude=nothing, frequency=nothing, phase=nothing)
    params = @parameters begin
        (start_time::Float64 = start_time)
        (offset::Float64 = offset)
        (amplitude::Float64 = amplitude)
        (frequency::Float64 = frequency)
        (phase::Float64 = phase)
    end
    vars = @variables begin
        y(t), [output = true]
    end
    eqs = Equation[
        y~ifelse(start_time < t, offset + amplitude * cos(2 * pi * frequency * (t - start_time) + phase), offset)
    ]
    return ODESystem(eqs, t, vars, params; systems=[], name)
end

@component function CosineTest(; name)
    systems = @named begin
        integrator = Integrator()
        signal = Cosine(amplitude=1, frequency=2, start_time=0.5, offset=0.5, phase=3.14)
    end
    eqs = Equation[
        signal.y~integrator.u
    ]
    return ODESystem(eqs, t, [], []; systems, name)
end

@named model_full = CosineTest()
model = structural_simplify(model_full; additional_passes=[ModelingToolkit.IfLifting]) # Error with IfLifting
# model = structural_simplify(model_full; additional_passes=[]) # Error with IfLifting
u0 = []
prob = ODEProblem(model, u0, (0, 5))
sol = solve(prob, DefaultODEAlgorithm())
# If list the time values, they go up to 5.0, as expected
sol[:t]
# If we interpolate at 0.1 seconds...no problem
sol(0.5, idxs=model.signal.y)
# If we interpolate at 0.51 seconds...it fails saying
# "Solution interpolation cannot extrapolate past the final timepoint."
sol(0.51, idxs=model.signal.y)
# Note the start time for our Cosine wave is 0.5 seconds!

Error & Stacktrace ⚠️

ERROR: Solution interpolation cannot extrapolate past the final timepoint. Either solve on a longer timespan or use the local extrapolation from the integrator interface.
Stacktrace:
 [1] error(s::String)
   @ Base ./error.jl:35
 [2] interpolation
   @ ~/.julia/packages/SciMLBase/3fgw8/src/interpolation.jl:230 [inlined]
 [3] (::SciMLBase.ConstantInterpolation{…})(tvals::Float64, idxs::Nothing, deriv::Type, p::Nothing, continuity::Symbol)
   @ SciMLBase ~/.julia/packages/SciMLBase/3fgw8/src/interpolation.jl:91
 [4] (::ODESolution{…})(t::Float64, ::Type{…}, idxs::Num, continuity::Symbol)
   @ SciMLBase ~/.julia/packages/SciMLBase/3fgw8/src/solutions/ode_solutions.jl:290
 [5] #_#543
   @ ~/.julia/packages/SciMLBase/3fgw8/src/solutions/ode_solutions.jl:221 [inlined]
 [6] AbstractODESolution
   @ ~/.julia/packages/SciMLBase/3fgw8/src/solutions/ode_solutions.jl:216 [inlined]
 [7] top-level scope
   @ ~/tmp/IfLifting/BlockComponents/src/mwe.jl:69
Some type information was truncated. Use `show(err)` to see complete types.

Environment (please complete the following information):

• Output of using Pkg; Pkg.status()

Project BlockComponents v0.12.4
Status `~/tmp/IfLifting/BlockComponents/Project.toml`
  [3626b584] JuliaSimCore v0.3.0
⌅ [961ee093] ModelingToolkit v9.61.0
  [50262376] OrdinaryDiffEqDefault v1.2.0
  [aea7be01] PrecompileTools v1.2.1
  [7e49a35a] RuntimeGeneratedFunctions v0.5.13
Info Packages marked with ⌅ have new versions available but compatibility constraints restrict them from upgrading. To see why use `status --outdated`

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

julia> using Pkg; Pkg.status(; mode = PKGMODE_MANIFEST)
Project BlockComponents v0.12.4
Status `~/tmp/IfLifting/BlockComponents/Manifest.toml`
⌃ [47edcb42] ADTypes v1.12.0
  [621f4979] AbstractFFTs v1.5.0
  [1520ce14] AbstractTrees v0.4.5
  [7d9f7c33] Accessors v0.1.41
  [79e6a3ab] Adapt v4.1.1
  [66dad0bd] AliasTables v1.1.3
  [ec485272] ArnoldiMethod v0.4.0
  [4fba245c] ArrayInterface v7.18.0
  [4c555306] ArrayLayouts v1.11.0
⌃ [a9b6321e] Atomix v1.0.1
  [e2ed5e7c] Bijections v0.1.9
  [62783981] BitTwiddlingConvenienceFunctions v0.1.6
⌃ [8e7c35d0] BlockArrays v1.3.0
  [70df07ce] BracketingNonlinearSolve v1.1.0
  [fa961155] CEnum v0.5.0
  [2a0fbf3d] CPUSummary v0.2.6
  [00ebfdb7] CSTParser v3.4.3
  [7057c7e9] Cassette v0.3.14
  [082447d4] ChainRules v1.72.2
  [d360d2e6] ChainRulesCore v1.25.1
  [fb6a15b2] CloseOpenIntervals v0.1.13
  [861a8166] Combinatorics v1.0.2
  [a80b9123] CommonMark v0.8.15
  [38540f10] CommonSolve v0.2.4
  [bbf7d656] CommonSubexpressions v0.3.1
  [f70d9fcc] CommonWorldInvalidations v1.0.0
  [34da2185] Compat v4.16.0
  [b152e2b5] CompositeTypes v0.1.4
  [a33af91c] CompositionsBase v0.1.2
  [2569d6c7] ConcreteStructs v0.2.3
  [88cd18e8] ConsoleProgressMonitor v0.1.2
  [187b0558] ConstructionBase v1.5.8
  [adafc99b] CpuId v0.3.1
  [a8cc5b0e] Crayons v4.1.1
  [9a962f9c] DataAPI v1.16.0
  [a93c6f00] DataFrames v1.7.0
  [864edb3b] DataStructures v0.18.20
  [e2d170a0] DataValueInterfaces v1.0.0
⌅ [2b5f629d] DiffEqBase v6.161.0
  [459566f4] DiffEqCallbacks v4.2.2
  [77a26b50] DiffEqNoiseProcess v5.24.1
  [163ba53b] DiffResults v1.1.0
  [b552c78f] DiffRules v1.15.1
⌃ [a0c0ee7d] DifferentiationInterface v0.6.31
  [31c24e10] Distributions v0.25.117
  [ffbed154] DocStringExtensions v0.9.3
  [5b8099bc] DomainSets v0.7.15
  [7c1d4256] DynamicPolynomials v0.6.1
⌃ [06fc5a27] DynamicQuantities v0.13.2
  [4e289a0a] EnumX v1.0.4
⌃ [7da242da] Enzyme v0.13.28
  [f151be2c] EnzymeCore v0.8.8
  [e2ba6199] ExprTools v0.1.10
⌅ [6b7a57c9] Expronicon v0.8.5
  [7034ab61] FastBroadcast v0.3.5
  [9aa1b823] FastClosures v0.3.2
  [29a986be] FastLapackInterface v2.0.4
  [a4df4552] FastPower v1.1.1
  [1a297f60] FillArrays v1.13.0
  [64ca27bc] FindFirstFunctions v1.4.1
⌃ [6a86dc24] FiniteDiff v2.26.2
  [1fa38f19] Format v1.3.7
  [f6369f11] ForwardDiff v0.10.38
  [f62d2435] FunctionProperties v0.1.2
  [069b7b12] FunctionWrappers v1.1.3
  [77dc65aa] FunctionWrappersWrappers v0.1.3
  [d9f16b24] Functors v0.5.2
⌃ [0c68f7d7] GPUArrays v11.2.1
  [46192b85] GPUArraysCore v0.2.0
⌃ [61eb1bfa] GPUCompiler v1.1.0
  [c27321d9] Glob v1.3.1
  [86223c79] Graphs v1.12.0
  [076d061b] HashArrayMappedTries v0.2.0
  [3e5b6fbb] HostCPUFeatures v0.1.17
  [34004b35] HypergeometricFunctions v0.3.27
  [7869d1d1] IRTools v0.4.14
  [615f187c] IfElse v0.1.1
  [d25df0c9] Inflate v0.1.5
  [842dd82b] InlineStrings v1.4.2
  [18e54dd8] IntegerMathUtils v0.1.2
  [8197267c] IntervalSets v0.7.10
  [3587e190] InverseFunctions v0.1.17
  [41ab1584] InvertedIndices v1.3.1
⌃ [92d709cd] IrrationalConstants v0.2.2
  [82899510] IteratorInterfaceExtensions v1.0.0
  [692b3bcd] JLLWrappers v1.7.0
  [682c06a0] JSON v0.21.4
  [0f8b85d8] JSON3 v1.14.1
  [7d188eb4] JSONSchema v1.4.1
  [98e50ef6] JuliaFormatter v1.0.62
  [9c9cc66b] JuliaSimBase v2.1.1
  [3626b584] JuliaSimCore v0.3.0
⌃ [ccbc3e58] JumpProcesses v9.14.1
  [ef3ab10e] KLU v0.6.0
⌃ [63c18a36] KernelAbstractions v0.9.31
  [ba0b0d4f] Krylov v0.9.9
  [5be7bae1] LBFGSB v0.4.1
  [929cbde3] LLVM v9.2.0
  [b964fa9f] LaTeXStrings v1.4.0
⌃ [23fbe1c1] Latexify v0.16.5
  [10f19ff3] LayoutPointers v0.1.17
⌃ [5078a376] LazyArrays v2.3.2
  [1d6d02ad] LeftChildRightSiblingTrees v0.2.0
  [87fe0de2] LineSearch v0.1.4
  [d3d80556] LineSearches v7.3.0
⌅ [7ed4a6bd] LinearSolve v2.38.0
  [2ab3a3ac] LogExpFunctions v0.3.29
  [e6f89c97] LoggingExtras v1.1.0
  [bdcacae8] LoopVectorization v0.12.171
  [d8e11817] MLStyle v0.4.17
  [1914dd2f] MacroTools v0.5.15
  [d125e4d3] ManualMemory v0.1.8
  [bb5d69b7] MaybeInplace v0.1.4
  [e1d29d7a] Missings v1.2.0
⌅ [961ee093] ModelingToolkit v9.61.0
  [46d2c3a1] MuladdMacro v0.2.4
  [102ac46a] MultivariatePolynomials v0.5.7
⌃ [d8a4904e] MutableArithmetics v1.6.2
  [d41bc354] NLSolversBase v7.8.3
  [872c559c] NNlib v0.9.27
⌃ [77ba4419] NaNMath v1.1.1
⌃ [8913a72c] NonlinearSolve v4.3.0
⌃ [be0214bd] NonlinearSolveBase v1.4.0
⌃ [5959db7a] NonlinearSolveFirstOrder v1.2.0
⌃ [9a2c21bd] NonlinearSolveQuasiNewton v1.1.0
  [26075421] NonlinearSolveSpectralMethods v1.1.0
  [d8793406] ObjectFile v0.4.3
  [6fe1bfb0] OffsetArrays v1.15.0
  [429524aa] Optim v1.11.0
  [3bd65402] Optimisers v0.4.4
⌅ [7f7a1694] Optimization v4.1.0
  [bca83a33] OptimizationBase v2.4.0
⌃ [bac558e1] OrderedCollections v1.7.0
  [6ad6398a] OrdinaryDiffEqBDF v1.2.0
⌅ [bbf590c4] OrdinaryDiffEqCore v1.15.0
  [50262376] OrdinaryDiffEqDefault v1.2.0
⌃ [4302a76b] OrdinaryDiffEqDifferentiation v1.3.0
⌃ [127b3ac7] OrdinaryDiffEqNonlinearSolve v1.3.0
⌃ [43230ef6] OrdinaryDiffEqRosenbrock v1.4.0
  [2d112036] OrdinaryDiffEqSDIRK v1.2.0
  [b1df2697] OrdinaryDiffEqTsit5 v1.1.0
  [79d7bb75] OrdinaryDiffEqVerner v1.1.1
  [90014a1f] PDMats v0.11.32
  [65ce6f38] PackageExtensionCompat v1.0.2
  [d96e819e] Parameters v0.12.3
  [69de0a69] Parsers v2.8.1
  [e409e4f3] PoissonRandom v0.4.4
  [f517fe37] Polyester v0.7.16
  [1d0040c9] PolyesterWeave v0.2.2
  [2dfb63ee] PooledArrays v1.4.3
  [85a6dd25] PositiveFactorizations v0.2.4
⌃ [d236fae5] PreallocationTools v0.4.24
  [aea7be01] PrecompileTools v1.2.1
  [21216c6a] Preferences v1.4.3
  [08abe8d2] PrettyTables v2.4.0
  [27ebfcd6] Primes v0.5.6
  [33c8b6b6] ProgressLogging v0.1.4
  [92933f4c] ProgressMeter v1.10.2
  [43287f4e] PtrArrays v1.3.0
⌃ [1fd47b50] QuadGK v2.11.1
  [74087812] Random123 v1.7.0
  [e6cf234a] RandomNumbers v1.6.0
  [c1ae055f] RealDot v0.1.0
  [3cdcf5f2] RecipesBase v1.3.4
⌃ [731186ca] RecursiveArrayTools v3.27.4
  [f2c3362d] RecursiveFactorization v0.2.23
  [189a3867] Reexport v1.2.2
  [05181044] RelocatableFolders v1.0.1
  [ae029012] Requires v1.3.0
  [ae5879a3] ResettableStacks v1.1.1
  [37e2e3b7] ReverseDiff v1.15.3
  [79098fc4] Rmath v0.8.0
  [7e49a35a] RuntimeGeneratedFunctions v0.5.13
  [9dfe8606] SCCNonlinearSolve v1.0.0
  [94e857df] SIMDTypes v0.1.0
  [476501e8] SLEEFPirates v0.6.43
⌃ [0bca4576] SciMLBase v2.72.0
  [19f34311] SciMLJacobianOperators v0.1.1
  [c0aeaf25] SciMLOperators v0.3.12
⌅ [1ed8b502] SciMLSensitivity v7.72.0
  [53ae85a6] SciMLStructures v1.6.1
  [7e506255] ScopedValues v1.3.0
  [6c6a2e73] Scratch v1.2.1
  [91c51154] SentinelArrays v1.4.8
  [efcf1570] Setfield v1.1.1
  [727e6d20] SimpleNonlinearSolve v2.1.0
  [699a6c99] SimpleTraits v0.9.4
  [ce78b400] SimpleUnPack v1.1.0
  [a2af1166] SortingAlgorithms v1.2.1
⌃ [9f842d2f] SparseConnectivityTracer v0.6.9
  [47a9eef4] SparseDiffTools v2.23.1
  [dc90abb0] SparseInverseSubset v0.1.2
⌃ [0a514795] SparseMatrixColorings v0.4.11
  [e56a9233] Sparspak v0.3.9
  [276daf66] SpecialFunctions v2.5.0
  [aedffcd0] Static v1.1.1
  [0d7ed370] StaticArrayInterface v1.8.0
⌃ [90137ffa] StaticArrays v1.9.10
  [1e83bf80] StaticArraysCore v1.4.3
  [10745b16] Statistics v1.11.1
  [82ae8749] StatsAPI v1.7.0
  [2913bbd2] StatsBase v0.34.4
  [4c63d2b9] StatsFuns v1.3.2
  [7792a7ef] StrideArraysCore v0.5.7
⌃ [892a3eda] StringManipulation v0.4.0
⌃ [09ab397b] StructArrays v0.6.21
  [53d494c1] StructIO v0.3.1
  [856f2bd8] StructTypes v1.11.0
  [2efcf032] SymbolicIndexingInterface v0.3.37
  [19f23fe9] SymbolicLimits v0.2.2
⌅ [d1185830] SymbolicUtils v3.11.0
⌅ [0c5d862f] Symbolics v6.24.0
  [3783bdb8] TableTraits v1.0.1
  [bd369af6] Tables v1.12.0
  [8ea1fca8] TermInterface v2.0.0
  [5d786b92] TerminalLoggers v0.1.7
  [8290d209] ThreadingUtilities v0.5.2
  [a759f4b9] TimerOutputs v0.5.26
  [0796e94c] Tokenize v0.5.29
  [9f7883ad] Tracker v0.2.37
  [d5829a12] TriangularSolve v0.2.1
  [410a4b4d] Tricks v0.1.10
  [781d530d] TruncatedStacktraces v1.4.0
  [5c2747f8] URIs v1.5.1
  [3a884ed6] UnPack v1.0.2
  [1986cc42] Unitful v1.22.0
  [a7c27f48] Unityper v0.1.6
  [013be700] UnsafeAtomics v0.3.0
  [3d5dd08c] VectorizationBase v0.21.71
  [19fa3120] VertexSafeGraphs v0.2.0
  [897b6980] WeakValueDicts v0.1.0
⌅ [e88e6eb3] Zygote v0.6.75
  [700de1a5] ZygoteRules v0.2.7
  [7cc45869] Enzyme_jll v0.0.172+0
  [1d5cc7b8] IntelOpenMP_jll v2025.0.4+0
  [dad2f222] LLVMExtra_jll v0.0.35+0
  [81d17ec3] L_BFGS_B_jll v3.0.1+0
  [856f044c] MKL_jll v2025.0.1+1
  [efe28fd5] OpenSpecFun_jll v0.5.6+0
  [f50d1b31] Rmath_jll v0.5.1+0
  [1317d2d5] oneTBB_jll v2021.12.0+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 v1.6.0
  [7b1f6079] FileWatching v1.11.0
  [9fa8497b] Future v1.11.0
  [b77e0a4c] InteractiveUtils v1.11.0
  [4af54fe1] LazyArtifacts v1.11.0
  [b27032c2] LibCURL v0.6.4
  [76f85450] LibGit2 v1.11.0
  [8f399da3] Libdl v1.11.0
  [37e2e46d] LinearAlgebra v1.11.0
  [56ddb016] Logging v1.11.0
  [d6f4376e] Markdown v1.11.0
  [a63ad114] Mmap v1.11.0
  [ca575930] NetworkOptions v1.2.0
  [44cfe95a] Pkg v1.11.0
  [de0858da] Printf v1.11.0
  [9a3f8284] Random v1.11.0
  [ea8e919c] SHA v0.7.0
  [9e88b42a] Serialization v1.11.0
  [1a1011a3] SharedArrays v1.11.0
  [6462fe0b] Sockets v1.11.0
  [2f01184e] SparseArrays v1.11.0
  [4607b0f0] SuiteSparse
  [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 v1.1.1+0
  [deac9b47] LibCURL_jll v8.6.0+0
  [e37daf67] LibGit2_jll v1.7.2+0
  [29816b5a] LibSSH2_jll v1.11.0+1
  [c8ffd9c3] MbedTLS_jll v2.28.6+0
  [14a3606d] MozillaCACerts_jll v2023.12.12
  [4536629a] OpenBLAS_jll v0.3.27+1
  [05823500] OpenLibm_jll v0.8.1+2
  [bea87d4a] SuiteSparse_jll v7.7.0+0
  [83775a58] Zlib_jll v1.2.13+1
  [8e850b90] libblastrampoline_jll v5.11.0+0
  [8e850ede] nghttp2_jll v1.59.0+0
  [3f19e933] p7zip_jll v17.4.0+2
Info Packages marked with ⌃ and ⌅ have new versions available. Those with ⌃ may be upgradable, but those with ⌅ are restricted by compatibility constraints from upgrading. To see why use `status --outdated -m`

• Output of versioninfo()

Julia Version 1.11.3
Commit d63adeda50d (2025-01-21 19:42 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-16.0.6 (ORCJIT, apple-m2)
Threads: 1 default, 0 interactive, 1 GC (on 8 virtual cores)
Environment:
  JULIA_PKG_SERVER = internal.juliahub.com
  JULIA_PKG_USE_CLI_GIT = true
  JULIA_EDITOR = code
  JULIA_NUM_THREADS =