ensure ArrayContext is not hashable

Author: alexfikl

arraycontext/context.py

@@ -286,6 +286,9 @@ def _get_fake_numpy_namespace(self) -> Any:
         from .fake_numpy import BaseFakeNumpyNamespace
         return BaseFakeNumpyNamespace(self)
 
+    def __hash__(self) -> int:
+        raise TypeError(f"unhashable type: '{type(self).__name__}'")
+
     @abstractmethod
     def empty(self,
               shape: Union[int, Tuple[int, ...]],