fix: make _DependencyChainError._message abstract for ty 0.0.87

modern_di/exceptions/registration.py

@@ -1,5 +1,6 @@
 """Errors reporting declaration mistakes, detected at declaration time or by ``validate()``."""
 
+import abc
 import enum
 import typing
 
@@ -199,7 +200,6 @@ class _DependencyChainError(RegistrationError):
     """
 
     _chain_headline: typing.ClassVar[str]
-    _message: typing.Callable[[], str]
 
     __slots__ = ("dependency_chain", "parameter_name", "provider")
 
@@ -215,6 +215,9 @@ def __init__(
         self.dependency_chain = dependency_chain
         super().__init__(self._message())
 
+    @abc.abstractmethod
+    def _message(self) -> str: ...
+
     @property
     def dependency_provider(self) -> "AbstractProvider[typing.Any]":
         """The dependency as declared: the type the parameter is annotated with."""

tests/test_resolver_compiler.py

@@ -883,7 +883,8 @@ def test_compile_resolver_rejects_an_unknown_provider_type() -> None:
     """
 
     class _Unsupported(AbstractProvider[int]):
-        __module__ = "modern_di.providers.unsupported"  # an internal type, which may subclass
+        # an internal type, which may subclass
+        __module__ = "modern_di.providers.unsupported"  # ty: ignore[invalid-mutable-override]
         __slots__ = ()
 
     with pytest.raises(TypeError, match="no compiled resolver for provider type _Unsupported"):