ParamSpec erases Optional when no-strict-optional is enabled #15932

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1. koogoro

   added

   bugmypy got something wrongmypy got something wrong

   topic-strict-optional

   topic-paramspecPEP 612, ParamSpec, ConcatenatePEP 612, ParamSpec, Concatenate

   on Aug 22, 2023
2. ilevkivskyi commented on Aug 22, 2023

   

   ilevkivskyi

   on Aug 22, 2023

   Member

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   This is consistent with behavior for regular TypeVars (since at least 1.0.0, but likely it is much older):

   from typing import Optional, TypeVar
   from typing import Callable
   
   def a(arg: Optional[int]) -> None: ...
   
   T = TypeVar('T')
   def b(f: Callable[[T], None]) -> Callable[[T], None]: ...
   
   reveal_type(b(a))  # Revealed type is "def (builtins.int)"

   Unions were simplified during expansion for ages, and inconsistent behavior for ParamSpec was a bug.
3. ilevkivskyi

   closed this as not plannedon Aug 22, 2023