[3.12] Improve code examples in typing.rst (GH-105346) (#105422)

Improve code examples in `typing.rst` (GH-105346)
(cherry picked from commit 81c8132)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

Doc/library/typing.rst

@@ -2,6 +2,11 @@
 :mod:`typing` --- Support for type hints
 ========================================
 
+.. testsetup:: *
+
+   import typing
+   from typing import *
+
 .. module:: typing
    :synopsis: Support for type hints (see :pep:`484`).
 
@@ -261,19 +266,22 @@ Callable
 Frameworks expecting callback functions of specific signatures might be
 type hinted using ``Callable[[Arg1Type, Arg2Type], ReturnType]``.
 
-For example::
+For example:
+
+.. testcode::
 
    from collections.abc import Callable
 
    def feeder(get_next_item: Callable[[], str]) -> None:
-       # Body
+       ...  # Body
 
    def async_query(on_success: Callable[[int], None],
                    on_error: Callable[[int, Exception], None]) -> None:
-       # Body
+       ...  # Body
 
    async def on_update(value: str) -> None:
-       # Body
+       ...  # Body
+
    callback: Callable[[str], Awaitable[None]] = on_update
 
 It is possible to declare the return type of a callable without specifying
@@ -431,11 +439,14 @@ In this case ``MyDict`` has a single parameter, ``T``.
 
 Using a generic class without specifying type parameters assumes
 :data:`Any` for each position. In the following example, ``MyIterable`` is
-not generic but implicitly inherits from ``Iterable[Any]``::
+not generic but implicitly inherits from ``Iterable[Any]``:
+
+.. testcode::
 
    from collections.abc import Iterable
 
    class MyIterable(Iterable): # Same as Iterable[Any]
+       ...
 
 User-defined generic type aliases are also supported. Examples::
 
@@ -701,9 +712,11 @@ These can be used as types in annotations and do not support ``[]``.
    A string created by composing ``LiteralString``-typed objects
    is also acceptable as a ``LiteralString``.
 
-   Example::
+   Example:
+
+   .. testcode::
 
-      def run_query(sql: LiteralString) -> ...
+      def run_query(sql: LiteralString) -> None:
           ...
 
       def caller(arbitrary_string: str, literal_string: LiteralString) -> None:
@@ -1596,16 +1609,19 @@ without the dedicated syntax, as documented below.
           def __abs__(self) -> "Array[*Shape]": ...
           def get_shape(self) -> tuple[*Shape]: ...
 
-   Type variable tuples can be happily combined with normal type variables::
+   Type variable tuples can be happily combined with normal type variables:
 
-      DType = TypeVar('DType')
+   .. testcode::
 
       class Array[DType, *Shape]:  # This is fine
           pass
 
       class Array2[*Shape, DType]:  # This would also be fine
           pass
 
+      class Height: ...
+      class Width: ...
+
       float_array_1d: Array[float, Height] = Array()     # Totally fine
       int_array_2d: Array[int, Height, Width] = Array()  # Yup, fine too
 
@@ -1759,7 +1775,9 @@ without the dedicated syntax, as documented below.
 
    The type of type aliases created through the :keyword:`type` statement.
 
-   Example::
+   Example:
+
+   .. doctest::
 
       >>> type Alias = int
       >>> type(Alias)
@@ -1769,7 +1787,9 @@ without the dedicated syntax, as documented below.
 
    .. attribute:: __name__
 
-      The name of the type alias::
+      The name of the type alias:
+
+      .. doctest::
 
          >>> type Alias = int
          >>> Alias.__name__
@@ -2158,7 +2178,11 @@ These are not used in annotations. They are building blocks for declaring types.
           group: list[T]
 
    To create a generic ``TypedDict`` that is compatible with Python 3.11
-   or lower, inherit from :class:`Generic` explicitly::
+   or lower, inherit from :class:`Generic` explicitly:
+
+   .. testcode::
+
+      T = TypeVar("T")
 
       class Group(TypedDict, Generic[T]):
           key: T
@@ -2171,7 +2195,9 @@ These are not used in annotations. They are building blocks for declaring types.
    .. attribute:: __total__
 
       ``Point2D.__total__`` gives the value of the ``total`` argument.
-      Example::
+      Example:
+
+      .. doctest::
 
          >>> from typing import TypedDict
          >>> class Point2D(TypedDict): pass
@@ -2201,7 +2227,9 @@ These are not used in annotations. They are building blocks for declaring types.
       non-required keys in the same ``TypedDict`` . This is done by declaring a
       ``TypedDict`` with one value for the ``total`` argument and then
       inheriting from it in another ``TypedDict`` with a different value for
-      ``total``::
+      ``total``:
+
+      .. doctest::
 
          >>> class Point2D(TypedDict, total=False):
          ...     x: int
@@ -2860,12 +2888,12 @@ Functions and decorators
    decorated object performs runtime "magic" that
    transforms a class, giving it :func:`dataclasses.dataclass`-like behaviors.
 
-   Example usage with a decorator function::
+   Example usage with a decorator function:
 
-      T = TypeVar("T")
+   .. testcode::
 
       @dataclass_transform()
-      def create_model(cls: type[T]) -> type[T]:
+      def create_model[T](cls: type[T]) -> type[T]:
           ...
           return cls
 
@@ -2969,7 +2997,9 @@ Functions and decorators
    runtime but should be ignored by a type checker.  At runtime, calling
    a ``@overload``-decorated function directly will raise
    :exc:`NotImplementedError`. An example of overload that gives a more
-   precise type than can be expressed using a union or a type variable::
+   precise type than can be expressed using a union or a type variable:
+
+   .. testcode::
 
       @overload
       def process(response: None) -> None:
@@ -2981,7 +3011,7 @@ Functions and decorators
       def process(response: bytes) -> str:
           ...
       def process(response):
-          <actual implementation>
+          ...  # actual implementation goes here
 
    See :pep:`484` for more details and comparison with other typing semantics.
 
@@ -3073,10 +3103,13 @@ Functions and decorators
    This helps prevent bugs that may occur when a base class is changed without
    an equivalent change to a child class.
 
-   For example::
+   For example:
+
+   .. testcode::
 
       class Base:
-           def log_status(self)
+          def log_status(self) -> None:
+              ...
 
       class Sub(Base):
           @override
@@ -3135,14 +3168,16 @@ Introspection helpers
 
    The function recursively replaces all ``Annotated[T, ...]`` with ``T``,
    unless ``include_extras`` is set to ``True`` (see :class:`Annotated` for
-   more information). For example::
+   more information). For example:
+
+   .. testcode::
 
        class Student(NamedTuple):
            name: Annotated[str, 'some marker']
 
-       get_type_hints(Student) == {'name': str}
-       get_type_hints(Student, include_extras=False) == {'name': str}
-       get_type_hints(Student, include_extras=True) == {
+       assert get_type_hints(Student) == {'name': str}
+       assert get_type_hints(Student, include_extras=False) == {'name': str}
+       assert get_type_hints(Student, include_extras=True) == {
            'name': Annotated[str, 'some marker']
        }
 
@@ -3169,7 +3204,9 @@ Introspection helpers
    If ``X`` is an instance of :class:`ParamSpecArgs` or :class:`ParamSpecKwargs`,
    return the underlying :class:`ParamSpec`.
    Return ``None`` for unsupported objects.
-   Examples::
+   Examples:
+
+   .. testcode::
 
       assert get_origin(str) is None
       assert get_origin(Dict[str, int]) is dict
@@ -3188,7 +3225,9 @@ Introspection helpers
    generic type, the order of ``(Y, Z, ...)`` may be different from the order
    of the original arguments ``[Y, Z, ...]`` due to type caching.
    Return ``()`` for unsupported objects.
-   Examples::
+   Examples:
+
+   .. testcode::
 
       assert get_args(int) == ()
       assert get_args(Dict[int, str]) == (int, str)
@@ -3200,14 +3239,20 @@ Introspection helpers
 
    Check if a type is a :class:`TypedDict`.
 
-   For example::
+   For example:
+
+   .. testcode::
 
       class Film(TypedDict):
           title: str
           year: int
 
-      is_typeddict(Film)  # => True
-      is_typeddict(list | str)  # => False
+      assert is_typeddict(Film)
+      assert not is_typeddict(list | str)
+
+      # TypedDict is a factory for creating typed dicts,
+      # not a typed dict itself
+      assert not is_typeddict(TypedDict)
 
    .. versionadded:: 3.10