`MethodError` — `eval_AST` Not Implemented for `BaseModelicaString`

[AnHeuermann]

Describe the bug 🐞

The evaluator has no method for BaseModelicaString AST nodes. This occurs when a string value appears in a structural context during model evaluation (e.g., string-typed parameters or modifiers).

Failing models from the MSL:

Model	BM Parse Log
Modelica.Electrical.Batteries.Examples.BatteryDischargeCharge	log
Modelica.Electrical.Batteries.Examples.SuperCapDischargeCharge	log
Modelica.Electrical.Analog.Examples.GenerationOfFMUs	log

---

Expected behavior

Parse the models.

Minimal Reproducible Example 👇

Without MRE, we would only be able to help you to a limited extent, and attention to the issue would be limited. to know more about MRE refer to wikipedia and stackoverflow.

//! base 0.1.0
package 'StringParameter'
  model 'StringParameter'
    parameter String 'label' = "my_label" "A string parameter";
    Real 'x';
  equation
    'x' = 1.0;
  end 'StringParameter';
end 'StringParameter';

julia> parsed_model = BaseModelica.parse_basemodelica("StringParameter.bmo")

Error & Stacktrace ⚠️

ERROR: MethodError: no method matching eval_AST(::BaseModelica.BaseModelicaString)
The function `eval_AST` exists, but no method is defined for this combination of argument types.

Closest candidates are:
  eval_AST(::BaseModelica.BaseModelicaModel)
   @ BaseModelica ~/.julia/packages/BaseModelica/jc9Ua/src/evaluator.jl:245
  eval_AST(::BaseModelica.BaseModelicaAnnotation)
   @ BaseModelica ~/.julia/packages/BaseModelica/jc9Ua/src/evaluator.jl:81
  eval_AST(::BaseModelica.BaseModelicaFunctionArgs)
   @ BaseModelica ~/.julia/packages/BaseModelica/jc9Ua/src/evaluator.jl:404
  ...

Stacktrace:
 [1] eval_AST(model::BaseModelica.BaseModelicaModel)
   @ BaseModelica ~/.julia/packages/BaseModelica/jc9Ua/src/evaluator.jl:301
 [2] eval_AST(package::BaseModelica.BaseModelicaPackage)
   @ BaseModelica ~/.julia/packages/BaseModelica/jc9Ua/src/evaluator.jl:401
 [3] baseModelica_to_ModelingToolkit
   @ ~/.julia/packages/BaseModelica/jc9Ua/src/evaluator.jl:442 [inlined]
 [4] parse_basemodelica(filename::String; parser::Symbol)
   @ BaseModelica ~/.julia/packages/BaseModelica/jc9Ua/src/BaseModelica.jl:43
 [5] parse_basemodelica(filename::String)
   @ BaseModelica ~/.julia/packages/BaseModelica/jc9Ua/src/BaseModelica.jl:35
 [6] top-level scope
   @ REPL[7]:1

Environment (please complete the following information):

• Output of using Pkg; Pkg.status()

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

• Output of versioninfo()

Julia Version 1.12.5
Commit 5fe89b8ddc1 (2026-02-09 16:05 UTC)
Build Info:
  Official https://julialang.org release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 28 × 13th Gen Intel(R) Core(TM) i7-13850HX
  WORD_SIZE: 64
  LLVM: libLLVM-18.1.7 (ORCJIT, alderlake)
  GC: Built with stock GC
Threads: 1 default, 1 interactive, 1 GC (on 28 virtual cores)

Additional context

Add any other context about the problem here.