BUG: interval_range ignores type of start (regression from pandas 2.2.2)

[michaelpradel]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

import pandas as pd
import numpy as np

result = pd.interval_range(start=np.float32(0), end=2, freq=1)
print(result)

Issue Description

I'd expect the above code to produce an IntervalIndex with dtype interval[float64, right], because I'm giving a float32 as the starting value. This has been the behavior in pandas 2.2.2.

The current main branch produces the following output, though, which ignores the starting value's type:
IntervalIndex([(0, 1], (1, 2]], dtype='interval[int64, right]')

The change seems due to #57399. The PR was meant to preserve the start/end type, but actually changed the behavior so that it isn't preserved anymore in the above case.

Expected Behavior

Expected output:
IntervalIndex([(0.0, 1.0], (1.0, 2.0]], dtype='interval[float64, right]')

Installed Versions

INSTALLED VERSIONS ------------------ commit : 6dbeeb4 python : 3.10.8.final.0 python-bits : 64 OS : Linux OS-release : 6.5.0-35-generic Version : #35-Ubuntu SMP PREEMPT_DYNAMIC Fri Apr 26 11:23:57 UTC 2024 machine : x86_64 processor : byteorder : little LC_ALL : None LANG : C.UTF-8 LOCALE : en_US.UTF-8

pandas : 2.2.0rc0+28.g6dbeeb4009
numpy : 1.26.4
pytz : 2024.1
dateutil : 2.9.0.post0
setuptools : 63.2.0
pip : 24.0
Cython : 3.0.10
pytest : 8.2.0
hypothesis : 6.100.2
sphinx : 7.3.7
blosc : None
feather : None
xlsxwriter : 3.2.0
lxml.etree : 5.2.1
html5lib : 1.1
pymysql : 1.4.6
psycopg2 : 2.9.9
jinja2 : 3.1.3
IPython : 8.24.0
pandas_datareader : None
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : 4.12.3
bottleneck : 1.3.8
fastparquet : 2024.2.0
fsspec : 2024.3.1
gcsfs : 2024.3.1
matplotlib : 3.8.4
numba : 0.59.1
numexpr : 2.10.0
odfpy : None
openpyxl : 3.1.2
pyarrow : 16.0.0
pyreadstat : 1.2.7
python-calamine : None
pyxlsb : 1.0.10
s3fs : 2024.3.1
scipy : 1.13.0
sqlalchemy : 2.0.29
tables : 3.9.2
tabulate : 0.9.0
xarray : 2024.3.0
xlrd : 2.0.1
zstandard : 0.22.0
tzdata : 2024.1
qtpy : None
pyqt5 : None