truncate_neg() fails on LaurentSeriesRing(QQ) when valuation is positive

[user202729]

sage: S.<t> = LaurentSeriesRing(QQ)
sage: (t^-2+t^-1+1+t+t^2).truncate_neg(-1)
t^-1 + 1 + t + t^2
sage: (t^-2+t^-1+1+t+t^2).truncate_neg(1)
t + t^2
sage: (t+t^2).truncate_neg(-1)
---------------------------------------------------------------------------
OverflowError                             Traceback (most recent call last)
Cell In[40], line 1
----> 1 (t+t**Integer(2)).truncate_neg(-Integer(1))

File laurent_series_ring_element.pyx:1085, in sage.rings.laurent_series_ring_element.LaurentSeries.t
runcate_neg()

File power_series_poly.pyx:614, in sage.rings.power_series_poly.PowerSeries_poly.__rshift__()

File polynomial_rational_flint.pyx:827, in sage.rings.polynomial.polynomial_rational_flint.Polynomia
l_rational_flint.__rshift__()

OverflowError: can't convert negative value to unsigned long


sage: (t+t^2).truncate_neg(1)
t + t^2

[tscrim]

The problem is that truncate_neg is starting from a point less than the valuation (in which case, it should just return the original series).

[5iri]

Hi!

What exactly is left to be done here?

[tscrim]

The optimization noted in #39711.