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Sign upmypy crashes with overloads of functools.singledispatch #8356
Comments
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Same here: Trying to combine Using Python 3.7 with mypy 0.750 Python code: from datetime import datetime, date
import typing
from typing import Union
from functools import singledispatch
from typing_extensions import Literal
DateInType = Union[date, str]
@typing.overload # <---- THIS IS ***line 50*** of td.py raising mypy internal error
def date2str(t: DateInType, out_format: Literal['str']) -> str: ...
@typing.overload
def date2str(t: DateInType, out_format: Literal['date']) -> date: ...
@singledispatch
def date2str(t, out_format):
''' Converts:
- datetime.date to string (YYYY-MM-DD)
- string (YYYY-MM-DD, YYYY/MM/DD, DD-MM-YYYY, ...) to datetime.date
Second argument = 'out_format' can be 'str' or 'date'.
If specified, returns output in string (YYYY-MM-DD) ['str'] or datetime.date format ['date'].
'''
@date2str.register(date)
def _date2str_date(t, out_format='str'):
''' Input format = datetime.date.
Output format, if string = YYYY-MM-DD'''
if out_format == 'str':
return t.strftime('%Y-%m-%d')
elif isinstance(t, datetime):
return t.date()
else:
return t
@date2str.register(str)
def _date2str_str(t, out_format='date'):
''' Input format = string (YYYY-MM-DD, DD-MM-YYYY, ...)'''
dformats = ('%Y-%m-%d', '%Y/%m/%d', '%d-%m-%Y', '%d/%m/%Y', '%Y%m%d')
for i, dformat in enumerate(dformats, start=1):
try:
d = datetime.strptime(t, dformat).date()
break
except ValueError:
if i == len(dformats):
raise
if out_format == 'date':
return d
else:
return date2str(d, out_format=out_format)
dt = datetime.now()
res = date2str(dt, out_format='date')
print(res, type(res))
assert type(res) == date
res2 = date2str(dt.date(), out_format='str')
print(res2, type(res2))
assert type(res2) == str
res3 = date2str('20061005', out_format='date')
print(res3, type(res3))
assert type(res3) == datemypy traceback: Am I doing something wrong? |
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Hello, I am an open source noob and would like to try and tackle this issue. Is that possible? |
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Yes, of course! Welcome. If you get stuck, feel free to ask questions here. |
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I couldn't replicate the bug on my machine. Using Python 3.8.2 and using my forked version of mypy (v0.770 I believe), copying @jeanmonet's code yielded the following output: I also tried replicating the error using your (@hauntsaninja ) code but I admit I didn't really understand what was going on there (what does the lambda mean?) cheers |
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My repro continues to repro for me (against mypy master). Note it contains the exact command I ran. The output you copied looks like it would be the result of running the program (with the Python interpreter), which is expected to work — this is a bug in mypy, not in Python itself. Remember mypy is a static checker, it doesn't actually run your code. If you still can't get it to repro, try sharing the exact commands you're running here. I assume by lambda you mean the def function named If you need a reference for what overload does (and to understand the code better, since the mypy crash occurs while running some overload checking related code) , I recommend https://mypy.readthedocs.io/en/stable/more_types.html#function-overloading. In general, I've found the mypy docs really helpful. |
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see #2904 |
I was trying out the advice I gave in #8354, and encountered a mypy crash: