PolynomialError when I try to call classify_ode

[satels]

from sympy import Function, Symbol, classify_ode, Eq, E
x = Symbol('x')
y = Function('y')
eq = Eq(-E**x*y(x).diff().diff() + y(x).diff(), 0)
classify_ode(eq)

THERE IS ERROR

eq = Eq(-E**x*y(x).diff().diff() + y(x).diff(), 0)
eq
Eq(-exp(x)*Derivative(y(x), (x, 2)) + Derivative(y(x), x), 0)

The error:

Traceback (most recent call last):
  File "/home/satels/workenv/krcore/lib/python3.9/site-packages/sympy/polys/polyutils.py", line 211, in _parallel_dict_from_expr_if_gens
    monom[indices[base]] = exp
KeyError: exp(x)
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/usr/lib/python3.9/code.py", line 90, in runcode
    exec(code, self.locals)
  File "<input>", line 1, in <module>
  File "/home/satels/workenv/krcore/lib/python3.9/site-packages/sympy/solvers/ode/ode.py", line 1033, in classify_ode
    if solver.matches():
  File "/home/satels/workenv/krcore/lib/python3.9/site-packages/sympy/solvers/ode/single.py", line 289, in matches
    self._matched = self._matches()
  File "/home/satels/workenv/krcore/lib/python3.9/site-packages/sympy/solvers/ode/single.py", line 2092, in _matches
    d = equivalence_hypergeometric(A, B, func)
  File "/home/satels/workenv/krcore/lib/python3.9/site-packages/sympy/solvers/ode/hypergeometric.py", line 116, in equivalence_hypergeometric
    sing_point.append(list(roots(arg, x).keys())[0])
  File "/home/satels/workenv/krcore/lib/python3.9/site-packages/sympy/polys/polyroots.py", line 886, in roots
    F = Poly(f, *gens, **flags)
  File "/home/satels/workenv/krcore/lib/python3.9/site-packages/sympy/polys/polytools.py", line 181, in __new__
    return cls._from_expr(rep, opt)
  File "/home/satels/workenv/krcore/lib/python3.9/site-packages/sympy/polys/polytools.py", line 310, in _from_expr
    rep, opt = _dict_from_expr(rep, opt)
  File "/home/satels/workenv/krcore/lib/python3.9/site-packages/sympy/polys/polyutils.py", line 368, in _dict_from_expr
    rep, gens = _dict_from_expr_if_gens(expr, opt)
  File "/home/satels/workenv/krcore/lib/python3.9/site-packages/sympy/polys/polyutils.py", line 307, in _dict_from_expr_if_gens
    (poly,), gens = _parallel_dict_from_expr_if_gens((expr,), opt)
  File "/home/satels/workenv/krcore/lib/python3.9/site-packages/sympy/polys/polyutils.py", line 216, in _parallel_dict_from_expr_if_gens
    raise PolynomialError("%s contains an element of "
sympy.polys.polyerrors.PolynomialError: exp(2*x) contains an element of the set of generators.

[oscarbenjamin]

Maybe something like this is needed:

diff --git a/sympy/solvers/ode/hypergeometric.py b/sympy/solvers/ode/hypergeometric.py
index b159053048..e0c42482b4 100644
--- a/sympy/solvers/ode/hypergeometric.py
+++ b/sympy/solvers/ode/hypergeometric.py
@@ -50,6 +50,8 @@ def match_2nd_hypergeometric(eq, func):
             n, d = eq.as_numer_denom()
             eq = expand(n)
             r = collect(eq, [func.diff(x, 2), func.diff(x), func]).match(deq)
+            if not all(val.is_polynomial() for val in r.values()):
+                return []
 
     if r and r[a3]!=0:
         A = cancel(r[b3]/r[a3])

I'm not sure exactly what the restrictions are for the 2nd hypergeometric method. I guess the coefficients should be required to be polynomial in the dependent variable.