LoadError: AssertionError: @parameters expects a tuple of expressions or an expression of a tuple

[kraqbi]

Describe the bug 🐞

Hello,
I can not use complex naming for my variables (more than a letter) in a @reaction_network if the @parameters is encased in a begin end.
It is quite an inconvenience for larger models in which I would like to use variables with explicit naming in a human-readable way.

Expected behavior

To work in all the following examples and allow larger names than a single letter.

Minimal Reproducible Example 👇

using Catalyst

mock0 = @reaction_network test0 begin # work
	@parameters begin
		a = 1 
		b = 2
		c
	end
	a, A --> B
	b, B --> A
end

mock1 = @reaction_network test1 begin #ERROR: LoadError: AssertionError: @parameters expects a tuple of expressions or an expression of a tuple (`@parameters x y z(t) v[1:3] w[1:2,1:4]` or `@parameters x y z(t) v[1:3] w[1:2,1:4] k=1.0`)
	@parameters begin
		doesnotwork = 25.0 
		b = 0 
		c = 0
	end
	a, A --> B
	b, B --> A
end


mock2 = @reaction_network test2 begin #ERROR: LoadError: AssertionError: @parameters expects a tuple of expressions or an expression of a tuple (`@parameters x y z(t) v[1:3] w[1:2,1:4]` or `@parameters x y z(t) v[1:3] w[1:2,1:4] k=1.0`)
	@parameters begin
		a = 25.0 
		b = 0 
		c = 0
	end
	doesnotwork, A --> B
	b, B --> A
end

mock3 = @reaction_network test3 begin # woek
	@parameters a = 25.0 b = 0 c = 0
	doesnotwork, A --> B
	b, B --> A
end

mock4 = @reaction_network test4 begin #ERROR: LoadError: AssertionError: @parameters expects a tuple of expressions or an expression of a tuple (`@parameters x y z(t) v[1:3] w[1:2,1:4]` or `@parameters x y z(t) v[1:3] w[1:2,1:4] k=1.0`)
	@parameters begin
		doesnotwork
		b
		c
	end
	a, A --> B
	b, B --> A
end

Error & Stacktrace ⚠️

ERROR: LoadError: AssertionError: @parameters expects a tuple of expressions or an expression of a tuple (`@parameters x y z(t) v[1:3] w[1:2,1:4]` or `@parameters x y z(t) v[1:3] w[1:2,1:4] k=1.0`)
Stacktrace:
 [1] _parse_vars(macroname::Symbol, type::Type, x::Tuple{Expr, Symbol}, transform::Function)
   @ Symbolics ~/.julia/packages/Symbolics/xD5Pj/src/variable.jl:166
 [2] var"@parameters"(__source__::LineNumberNode, __module__::Module, xs::Vararg{Any})
   @ ModelingToolkit ~/.julia/packages/ModelingToolkit/udKhl/src/parameters.jl:76
 [3] eval(m::Module, e::Any)
   @ Core ./boot.jl:489
in expression starting at <macrocall>:0

Environment (please complete the following information):

• Output of using Pkg; Pkg.status()

  [479239e8] Catalyst v15.0.8
  [a93c6f00] DataFrames v1.8.1
  [23fbe1c1] Latexify v0.16.10
  [429524aa] Optim v1.13.2
  [48d54b35] PEtab v3.10.3
  [91a5bcdd] Plots v1.41.1
  [f3b207a7] StatsPlots v0.15.8
⌃ [220ca800] StructuralIdentifiability v0.5.14

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

  [47edcb42] ADTypes v1.18.0
⌅ [c3fe647b] AbstractAlgebra v0.44.13
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  [79e6a3ab] Adapt v4.4.0
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  [fa961155] CEnum v0.5.0
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⌅ [861a8166] Combinatorics v1.0.2
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⌃ [102ac46a] MultivariatePolynomials v0.5.9
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⌅ [2edaba10] Nemo v0.49.5
⌃ [8913a72c] NonlinearSolve v4.10.0
⌅ [be0214bd] NonlinearSolveBase v1.16.1
⌃ [5959db7a] NonlinearSolveFirstOrder v1.8.0
⌃ [9a2c21bd] NonlinearSolveQuasiNewton v1.9.0
⌃ [26075421] NonlinearSolveSpectralMethods v1.4.0
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⌃ [127b3ac7] OrdinaryDiffEqNonlinearSolve v1.14.1
  [43230ef6] OrdinaryDiffEqRosenbrock v1.18.1
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  [f638f0a6] libfdk_aac_jll v2.0.4+0
  [36db933b] libinput_jll v1.28.1+0
  [b53b4c65] libpng_jll v1.6.50+0
  [f27f6e37] libvorbis_jll v1.3.8+0
  [009596ad] mtdev_jll v1.1.7+0
  [1317d2d5] oneTBB_jll v2022.0.0+1
  [1270edf5] x264_jll v10164.0.1+0
  [dfaa095f] x265_jll v4.1.0+0
  [d8fb68d0] xkbcommon_jll v1.9.2+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
  [ac6e5ff7] JuliaSyntaxHighlighting v1.12.0
  [4af54fe1] LazyArtifacts v1.11.0
  [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
  [a63ad114] Mmap 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
  [1a1011a3] SharedArrays 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
  [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
  [781609d7] GMP_jll v6.3.0+2
  [deac9b47] LibCURL_jll v8.11.1+1
  [e37daf67] LibGit2_jll v1.9.0+0
  [29816b5a] LibSSH2_jll v1.11.3+1
  [3a97d323] MPFR_jll v4.2.2+0
  [14a3606d] MozillaCACerts_jll v2025.5.20
  [4536629a] OpenBLAS_jll v0.3.29+0
  [05823500] OpenLibm_jll v0.8.7+0
  [458c3c95] OpenSSL_jll v3.5.1+0
  [efcefdf7] PCRE2_jll v10.44.0+1
  [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 v17.5.0+2

• Output of versioninfo()

Julia Version 1.12.1
Commit ba1e628ee49 (2025-10-17 13:02 UTC)
Build Info:
  Official https://julialang.org release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 20 × 13th Gen Intel(R) Core(TM) i7-13800H
  WORD_SIZE: 64
  LLVM: libLLVM-18.1.7 (ORCJIT, alderlake)
  GC: Built with stock GC
Threads: 1 default, 1 interactive, 1 GC (on 20 virtual cores)
Environment:
  JULIA_EDITOR = code
  JULIA_VSCODE_REPL = 1

Additional context

I am trying to use Catalyst with explicit naming of my variables and initial default values

[kraqbi]

It gets weirder :

mock5 = @reaction_network test5 begin #work
	@parameters begin
		doeswork = 25.0 
		b = 0 
		c = 0
	end
	doeswork, A --> B
	b, B --> A
end

So the problem might come if there are both declarated parameters and deducted ones?

[TorkelE]

Thanks for the report.

I vaguely think I remember some similar issue from quite a while ago, but I have forgotten the details. I will have a look at it and figure out what is going on, but it do seem like an authetic error. No promises when we can have a fix out.