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.

[environment]
typeshed = "/typeshed"

/typeshed/stdlib/builtins.pyi:

class object: ...
class int: ...
class dict[K, V, Extra]: ...

/typeshed/stdlib/typing_extensions.pyi:

def reveal_type(obj, /): ...

If we don't, then we won't be able to infer the types of variadic keyword arguments correctly.

def f(**kwargs):
    reveal_type(kwargs)  # revealed: Unknown

def g(**kwargs: int):
    reveal_type(kwargs)  # revealed: Unknown