[ty] Improve and extend tests for instance attributes redeclared in subclasses (#20866)

Part of astral-sh/ty#1345

Author: AlexWaygood

crates/ty_python_semantic/resources/mdtest/attributes.md

@@ -828,6 +828,10 @@ class Base:
     redeclared_with_narrower_type: str | None
     redeclared_with_wider_type: str | None
 
+    redeclared_in_method_with_same_type: str | None
+    redeclared_in_method_with_narrower_type: str | None
+    redeclared_in_method_with_wider_type: str | None
+
     overwritten_in_subclass_body: str
     overwritten_in_subclass_method: str
 
@@ -873,6 +877,14 @@ class Intermediate(Base):
     undeclared = "intermediate"
 
     def set_attributes(self) -> None:
+        self.redeclared_in_method_with_same_type: str | None = None
+
+        # TODO: This should be an error (violates Liskov)
+        self.redeclared_in_method_with_narrower_type: str = "foo"
+
+        # TODO: This should be an error (violates Liskov)
+        self.redeclared_in_method_with_wider_type: object = object()
+
         # TODO: This should be an `invalid-assignment` error
         self.overwritten_in_subclass_method = None
 
@@ -889,18 +901,33 @@ reveal_type(Derived().attribute)  # revealed: int | None
 reveal_type(Derived.redeclared_with_same_type)  # revealed: str | None
 reveal_type(Derived().redeclared_with_same_type)  # revealed: str | None
 
-# TODO: It would probably be more consistent if these were `str | None`
+# We infer the narrower type here, despite the Liskov violation,
+# for compatibility with other type checkers (and to reflect the clear user intent)
 reveal_type(Derived.redeclared_with_narrower_type)  # revealed: str
 reveal_type(Derived().redeclared_with_narrower_type)  # revealed: str
 
-# TODO: It would probably be more consistent if these were `str | None`
+# We infer the wider type here, despite the Liskov violation,
+# for compatibility with other type checkers (and to reflect the clear user intent)
 reveal_type(Derived.redeclared_with_wider_type)  # revealed: str | int | None
 reveal_type(Derived().redeclared_with_wider_type)  # revealed: str | int | None
 
 # TODO: Both of these should be `str`
 reveal_type(Derived.overwritten_in_subclass_body)  # revealed: Unknown | None
 reveal_type(Derived().overwritten_in_subclass_body)  # revealed: Unknown | None | str
 
+reveal_type(Derived.redeclared_in_method_with_same_type)  # revealed: str | None
+reveal_type(Derived().redeclared_in_method_with_same_type)  # revealed: str | None
+
+# TODO: both of these should be `str`, despite the Liskov violation,
+# for compatibility with other type checkers (and to reflect the clear user intent)
+reveal_type(Derived.redeclared_in_method_with_narrower_type)  # revealed: str | None
+reveal_type(Derived().redeclared_in_method_with_narrower_type)  # revealed: str | None
+
+# TODO: both of these should be `object`, despite the Liskov violation,
+# for compatibility with other type checkers (and to reflect the clear user intent)
+reveal_type(Derived.redeclared_in_method_with_wider_type)  # revealed: str | None
+reveal_type(Derived().redeclared_in_method_with_wider_type)  # revealed: object
+
 reveal_type(Derived.overwritten_in_subclass_method)  # revealed: str
 reveal_type(Derived().overwritten_in_subclass_method)  # revealed: str