make index and EA base as non-hashable

Author: MarcoGorelli

pandas/core/arrays/base.py

@@ -1302,8 +1302,10 @@ def _reduce(self, name: str, *, skipna: bool = True, **kwargs):
         """
         raise TypeError(f"cannot perform {name} with type {self.dtype}")
 
-    def __hash__(self) -> int:
-        raise TypeError(f"unhashable type: {repr(type(self).__name__)}")
+    # https://github.com/python/typeshed/issues/2148#issuecomment-520783318
+    # Incompatible types in assignment (expression has type "None", base class
+    # "object" defined the type as "Callable[[object], int]")
+    __hash__: None  # type: ignore[assignment]
 
     # ------------------------------------------------------------------------
     # Non-Optimized Default Methods

pandas/core/indexes/base.py

@@ -4562,9 +4562,10 @@ def __contains__(self, key: Any) -> bool:
         except (OverflowError, TypeError, ValueError):
             return False
 
-    @final
-    def __hash__(self):
-        raise TypeError(f"unhashable type: {repr(type(self).__name__)}")
+    # https://github.com/python/typeshed/issues/2148#issuecomment-520783318
+    # Incompatible types in assignment (expression has type "None", base class
+    # "object" defined the type as "Callable[[object], int]")
+    __hash__: None  # type: ignore[assignment]
 
     @final
     def __setitem__(self, key, value):