QuerySet.annotate improvements (#398)

* QuerySet.annotate returns self-type. Attribute access falls back to Any.

- QuerySets that have an annotated model do not report errors during .filter() when called with invalid fields.
- QuerySets that have an annotated model return ordinary dict rather than TypedDict for .values()
- QuerySets that have an annotated model return Any rather than typed Tuple for .values_list()

* Fix .annotate so it reuses existing annotated types. Fixes error in typechecking Django testsuite.

* Fix self-typecheck error

* Fix flake8

* Fix case of .values/.values_list before .annotate.

* Extra ignores for Django 2.2 tests (false positives due to tests assuming QuerySet.first() won't return None)

Fix mypy self-check.

* More tests + more precise typing in case annotate called before values_list.

Cleanup tests.

* Test and fix annotate in combination with values/values_list with no params.

* Remove line that does nothing :)

* Formatting fixes

* Address code review

* Fix quoting in tests after mypy changed things

* Use Final

* Use typing_extensions.Final

* Fixes after ValuesQuerySet -> _ValuesQuerySet refactor. Still not passing tests yet.

* Fix inheritance of _ValuesQuerySet and remove unneeded type ignores.

This allows the test
"annotate_values_or_values_list_before_or_after_annotate_broadens_type"
to pass.

* Make it possible to annotate user code with "annotated models", using PEP 583 Annotated type.

* Add docs

* Make QuerySet[_T] an external alias to _QuerySet[_T, _T].

This currently has the drawback that error messages display the internal type _QuerySet, with both type arguments.

See also discussion on #661 and #608.

Fixes #635: QuerySet methods on Managers (like .all()) now return QuerySets rather than Managers.

Address code review by @sobolevn.

* Support passing TypedDicts to WithAnnotations

* Add an example of an error to README regarding WithAnnotations + TypedDict.

* Fix runtime behavior of ValuesQuerySet alias (you can't extend Any, for example).

Fix some edge case with from_queryset after QuerySet changed to be an
alias to _QuerySet. Can't make a minimal test case as this only occurred
on a large internal codebase.

* Fix issue when using from_queryset in some cases when having an argument with a type annotation on the QuerySet.

The mypy docstring on anal_type says not to call defer() after it.

mypy_django_plugin/transformers/managers.py

@@ -19,6 +19,16 @@ def create_new_manager_class_from_from_queryset_method(ctx: DynamicClassDefConte
         return
 
     assert isinstance(base_manager_info, TypeInfo)
+
+    passed_queryset = ctx.call.args[0]
+    assert isinstance(passed_queryset, NameExpr)
+
+    derived_queryset_fullname = passed_queryset.fullname
+    if derived_queryset_fullname is None:
+        # In some cases, due to the way the semantic analyzer works, only passed_queryset.name is available.
+        # But it should be analyzed again, so this isn't a problem.
+        return
+
     new_manager_info = semanal_api.basic_new_typeinfo(
         ctx.name, basetype_or_fallback=Instance(base_manager_info, [AnyType(TypeOfAny.unannotated)]), line=ctx.call.line
     )
@@ -28,11 +38,6 @@ def create_new_manager_class_from_from_queryset_method(ctx: DynamicClassDefConte
 
     current_module = semanal_api.cur_mod_node
     current_module.names[ctx.name] = SymbolTableNode(GDEF, new_manager_info, plugin_generated=True)
-    passed_queryset = ctx.call.args[0]
-    assert isinstance(passed_queryset, NameExpr)
-
-    derived_queryset_fullname = passed_queryset.fullname
-    assert derived_queryset_fullname is not None
 
     sym = semanal_api.lookup_fully_qualified_or_none(derived_queryset_fullname)
     assert sym is not None