Open 0xhtml opened 5 months ago
Repeat the union type hint on Ham
, instead of using an overrided type (int) implied from the default value alone, and mypy passes it:
class Spam:
var: int | str
class Ham(Spam):
var: int | str = 10
class Eggs(Ham):
var = "abc"
Bug Report
Defining a variable with a type union or optional, etc. and then setting the variable in an extending class overwrites the type of the variable to the narrower type used in the assignment. E.g.
int | str
toint
. If the class is extended again, the type of the variable is the narrower type and can't be broadened again by a simple assignment or changed to another type compatible with the original base class.To Reproduce
The following code results in an incompatible types in assignment error in the
Eggs
class:Expected Behavior
I would expect the explicitly set type of the base class
Spam
to be inherited by the first extending classHam
and that an assignment doesn't change the general type of the variable. So that the second extending class can still setvar
to a str.Just like the following code is valid:
Actual Behavior
The assignment in
Ham
sets the type ofvar
toint
and the classEggs
can't setvar
to"abc"
of typestr
.mypy output:
a.py:8: error: Incompatible types in assignment (expression has type "str", base class "Ham" defined the type as "int") [assignment]
Your Environment
mypy 1.10.0 (compiled: yes)
Python 3.12.3 (main, Apr 23 2024, 09:16:07) [GCC 13.2.1 20240417] on linux