Panic when printing a Struct of Objects

[douglas-raillard-arm]

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

import polars as pl
pl.DataFrame(dict(a=[1], schema={'a': pl.Duration()}))

Log output

>>> POLARS_VERBOSE=1 python3
Python 3.11.7 (main, Dec  8 2023, 18:56:57) [GCC 9.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import polars as pl
>>> pl.DataFrame(dict(a=[1], schema={'a': pl.Duration()}))
[1]    2396717 segmentation fault (core dumped)  POLARS_VERBOSE=1 python3

Issue description

Creating the DataFrame segfaults when specifying a schema that uses pl.Duration()

Expected behavior

Something else than a segfault

Installed versions

--------Version info---------
Polars:               0.20.16
Index type:           UInt32
Platform:             Linux-5.15.0-92-generic-x86_64-with-glibc2.31
Python:               3.11.7 (main, Dec  8 2023, 18:56:57) [GCC 9.4.0]

----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:               <not installed>
matplotlib:           3.8.3
numpy:                1.26.4
openpyxl:             <not installed>
pandas:               2.2.1
pyarrow:              15.0.0
pydantic:             <not installed>
pyiceberg:            <not installed>
pyxlsb:               <not installed>
sqlalchemy:           <not installed>
xlsx2csv:             <not installed>
xlsxwriter:           <not installed>

[mcrumiller]

You are not calling pl.DataFrame correctly--you put your schema inside your dict. So what you are doing is the equivalent of:

import polars as pl

pl.DataFrame({
    "a": [1],
    "schema": {"a": pl.Duration()},
})

However, this is still a segfault which is bad. The primary issue here is actually Cannot create struct column where elements are dtypes:

import polars as pl

df = pl.DataFrame({
    "a": [pl.Int32, pl.UInt8],
})
df.select(pl.struct("a"))  # segmentation fault

[douglas-raillard-arm]

Indeed, that probably explains why no-one else had reported something similar :)

[orlp]

An even simpler reproduction:

import polars as pl

obj = object()
df = pl.DataFrame({"a": [obj]})
struct = df.select(pl.struct("a"))
print(struct) # segfault