[ty] Support extending __all__ from an imported module even when the module is not an ExprName node (#17947)

crates/ty_python_semantic/resources/mdtest/import/dunder_all.md

@@ -251,6 +251,53 @@ from ty_extensions import dunder_all_names
 reveal_type(dunder_all_names(exporter))
 ```
 
+### Augmenting list with a list or submodule `__all__` (2)
+
+The same again, but the submodule is an attribute expression rather than a name expression:
+
+`exporter/__init__.py`:
+
+```py
+```
+
+`exporter/sub.py`:
+
+```py
+__all__ = ["foo"]
+
+foo = 42
+```
+
+`exporter/sub2.py`:
+
+```py
+__all__ = ["bar"]
+
+bar = 56
+```
+
+`module.py`:
+
+```py
+import exporter.sub
+import exporter.sub2
+
+__all__ = []
+
+if True:
+    __all__.extend(exporter.sub.__all__)
+    __all__ += exporter.sub2.__all__
+```
+
+`main.py`:
+
+```py
+import module
+from ty_extensions import dunder_all_names
+
+reveal_type(dunder_all_names(module))  # revealed: tuple[Literal["bar"], Literal["foo"]]
+```
+
 ### Extending with a list or submodule `__all__`
 
 `subexporter.py`: