BUG: pd.Series fails to cast datetime series containing only NaT to timedelta type

[Casper-Guo]

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Reproducible Example

import pandas as pd

example = pd.Series(
    pd.Series([pd.NaT], dtype="datetime64[ns]"), dtype="timedelta64[ns]"
)
print(example.dtype)

Issue Description

The above snipper outputs datetime64[ns], which is against the documented behavior for pd.Series:

dtype : str, numpy.dtype, or ExtensionDtype, optional
Data type for the output Series.

Reference theOehrly/Fast-F1#674

Expected Behavior

Expect the output series example to have timedelta64[ns] data type. Or for the snippet to emit an error or warning indicating this conversion is not available.

Installed Versions

INSTALLED VERSIONS

commit : 0691c5c
python : 3.12.4
python-bits : 64
OS : Linux
OS-release : 5.15.167.4-microsoft-standard-WSL2
Version : #1 SMP Tue Nov 5 00:21:55 UTC 2024
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : C.UTF-8
LOCALE : C.UTF-8

pandas : 2.2.3
numpy : 2.0.1
pytz : 2024.1
dateutil : 2.9.0.post0
pip : 24.2
Cython : None
sphinx : None
IPython : 8.26.0
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : 4.12.3
blosc : None
bottleneck : None
dataframe-api-compat : None
fastparquet : None
fsspec : None
html5lib : None
hypothesis : None
gcsfs : None
jinja2 : 3.1.5
lxml.etree : None
matplotlib : 3.9.2
numba : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
psycopg2 : None
pymysql : None
pyarrow : None
pyreadstat : None
pytest : 8.3.3
python-calamine : None
pyxlsb : None
s3fs : None
scipy : 1.14.0
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlsxwriter : None
zstandard : None
tzdata : 2024.1
qtpy : None
pyqt5 : None

[jbrockmendel]

I’d expect this to raise