pl.Enum Bug / Incorrect and Kernel crashed

[Julian-J-S]

Checks

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of Polars.

Reproducible example

for t in [
    pl.UInt8,
    pl.UInt16,
    pl.UInt32,
    pl.UInt64,
    pl.Int8,
    pl.Int16,
    pl.Int32,
    pl.Int64,
]:
    print(t)
    s = pl.Series([0, 1, 2], dtype=t).cast(pl.Enum(["a", "b", "c"]))  # This does NOT error
    try:
        # print(s.to_list())  # >>>>>>>>>>>>>>>>>> this crashes the kernel!!!!!!!!!!!!!!!!!!!!!!!!!
        print(s) # This given an Exception!
    except BaseException as e:
        print(e)

Log output

UInt8
assertion failed: i < self.len()
UInt16
assertion failed: i < self.len()
UInt32
shape: (3,)
Series: '' [enum]
[
	"a"
	"b"
	"c"
]
UInt64
shape: (3,)
Series: '' [enum]
[
	"a"
	"a"
	"b"
]
Int8
assertion failed: i < self.len()
Int16
assertion failed: i < self.len()
Int32
shape: (3,)
Series: '' [enum]
[
	"a"
	"b"
	"c"
]
Int64
shape: (3,)
Series: '' [enum]
[
	"a"
	"a"
	"b"
]

Issue description

Exception & Wrong results

converting an int other than 32bit to an pl.Enum either

• crashes when printing for 8/16 bit ints with assertion failed: i < self.len() or
• wrong result ["a", "a", "c"] instead of ["a", "b", "c"] (even worse because you might not realize this!)

Kernel Crash

converting from 8/16 bit int to Enum and then calling s.to_list() crashes the kernel

Expected behavior

• conversion should work for all integers
• conversion should be correct(!) for 64bit ints
• no kernel crash

Installed versions

--------Version info---------
Polars:               0.20.21
Index type:           UInt32
Platform:             Windows-10-10.0.19045-SP0
Python:               3.11.9 (tags/v3.11.9:de54cf5, Apr  2 2024, 10:12:12) [MSC v.1938 64 bit (AMD64)]

----Optional dependencies----
adbc_driver_manager:  <not installed>
cloudpickle:          <not installed>
connectorx:           <not installed>
deltalake:            <not installed>
fastexcel:            <not installed>
fsspec:               <not installed>
gevent:               <not installed>
hvplot:               0.9.1
matplotlib:           <not installed>
nest_asyncio:         1.5.7
numpy:                1.26.3
openpyxl:             <not installed>
pandas:               2.2.0
pyarrow:              14.0.0
pydantic:             <not installed>
pyiceberg:            <not installed>
pyxlsb:               <not installed>
sqlalchemy:           <not installed>
xlsx2csv:             <not installed>
xlsxwriter:           <not installed>

[reswqa]

Thank you for your detailed report. I'll have a look at it.