RSolve no longer Get'able - related to SetDelayed assignment evaluation?

[rocky]

Description

RSolve gives a Python traceback in loading with Get/Needs.

How to Reproduce and Output Given

$ mathics3 --post-mortem

Mathics3 10.0.1dev0
Running on linux CPython 3.13.12 (main, Feb  7 2026, 20:16:33) [GCC 13.3.0]
using SymPy 1.14.0, mpmath 1.3.0, numpy 2.4.2, cython 3.2.4, scipy 1.17.0, skimage 0.26.0
...
In[1]:= LoadModule["pymathics.trepan"]
Out[1]= "pymathics.trepan"
In[2]:= Get["mathics/Packages/DiscreteMath/RSolve.m", Trace->True]
Reading file: mathics/Packages/DiscreteMath/RSolve.m

2: (* :Title: RSolve *)
4: (* :Author:  Marko Petkovsek *)
...
2398: iSeriesTerm[HypergeometricPFQ[aList_, bList_, c_. z_], z_Symbol, n_] := ...
Traceback (most recent call last):
  File "mathics3", line 7, in <module>
    sys.exit(main())
             ~~~~^^
...
  File "mathics/core/rules.py", line 417, in apply_function
    result = self.function(evaluation=evaluation, **vars_noctx) or expression
             ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "mathics/builtin/specialfns/hypergeom.py", line 207, in eval
    return eval_HypergeometricPQF(a, b, z)
  File "mathics/eval/specialfns/hypergeom.py", line 108, in eval_HypergeometricPQF
    and hasattr(a[0], "is_zero")
                ~^^^
TypeError: 'Expression' object is not subscriptable
Uncaught exception. Entering post-mortem debugger...
(/src/external-vcs/github/Mathics3/mathics-core/mathics/eval/specialfns/hypergeom.py:108:21 @66): eval_HypergeometricPQF
!! 108         and hasattr(a[0], "is_zero")

(Trepan3k:pm) load trepan3k_mathics3
loaded command: "mabort"
...
(Trepan3k:pm) mbt -b
B:0 (1) HypergeometricPFQ[a_, b_, z_]

          file 'mathics/builtin/specialfns/hypergeom.py' at line 207, column 16
B:1 (39) SetDelayed[]

           file 'mathics/eval/assignments/assignment.py' at line 119, column 5
B:2 (40) SetDelayed[]

           file 'mathics/builtin/assignments/assignment.py' at line 225, column 12
B:3 (70) Get[path_String, OptionsPattern[Get]]

           file 'mathics/builtin/files_io/files.py' at line 448, column 16
	   
(Trepan3k:pm) a.elements
(<Symbol: DiscreteMath`RSolve`Private`aList>, <Expression: <Symbol: System`Blank>[]>)
(Trepan3k:pm) pe -p a.elements
tuple(aList, _)

Expected behavior

No traceback.

Additional context

RSolve didn't used to crash. Git bisect will help determine which change caused this to break.

I wonder if this related to the Hold problem in LHS evaluation?