Rename Red Knot (#17820)

crates/ty_python_semantic/resources/mdtest/generics/builtins.md

@@ -0,0 +1,35 @@
+# Generic builtins
+
+## Variadic keyword arguments with a custom `dict`
+
+When we define `dict` in a custom typeshed, we must take care to define it as a generic class in the
+same way as in the real typeshed.
+
+```toml
+[environment]
+typeshed = "/typeshed"
+```
+
+`/typeshed/stdlib/builtins.pyi`:
+
+```pyi
+class object: ...
+class int: ...
+class dict[K, V, Extra]: ...
+```
+
+`/typeshed/stdlib/typing_extensions.pyi`:
+
+```pyi
+def reveal_type(obj, /): ...
+```
+
+If we don't, then we won't be able to infer the types of variadic keyword arguments correctly.
+
+```py
+def f(**kwargs):
+    reveal_type(kwargs)  # revealed: Unknown
+
+def g(**kwargs: int):
+    reveal_type(kwargs)  # revealed: Unknown
+```