Improves edit.py and its forms (#648)

* Improves edit.py and its forms

* Adds tests

tests/typecheck/views/generic/test_edit.yml

@@ -10,6 +10,8 @@
                 """Ensure that form can have type AuthenticationForm."""
                 form.get_user()
                 return HttpResponseRedirect(self.get_success_url())
+
+
 -   case: dispatch_http_response
     main: |
         from django.http import HttpResponse
@@ -19,6 +21,8 @@
             def dispatch(self, request, *args, **kwargs) -> HttpResponse:
                 response: HttpResponse
                 return response
+
+
 -   case: dispatch_streaming_http_response
     main: |
         from django.http import StreamingHttpResponse
@@ -28,3 +32,32 @@
             def dispatch(self, request, *args, **kwargs) -> StreamingHttpResponse:
                 response: StreamingHttpResponse
                 return response
+
+
+-   case: generic_form_views
+    main: |
+        from django.views.generic.edit import CreateView, UpdateView
+        from django import forms
+        from myapp.models import Article
+
+        class ArticleModelForm(forms.ModelForm[Article]):
+            class Meta:
+                model = Article
+
+        class MyCreateView(CreateView[Article, ArticleModelForm]):
+            def some(self) -> None:
+                reveal_type(self.get_form_class())  # N: Revealed type is "Type[main.ArticleModelForm*]"
+
+        class MyUpdateView(UpdateView[Article, ArticleModelForm]):
+            def some(self) -> None:
+                reveal_type(self.get_form_class()) # N: Revealed type is "Type[main.ArticleModelForm*]"
+    installed_apps:
+        - myapp
+    files:
+        -   path: myapp/__init__.py
+        -   path: myapp/models.py
+            content: |
+                from django.db import models
+
+                class Article(models.Model):
+                    pass