Update generics reference to use PEP 695 type parameter syntax

docs/reference/generics.rst

@@ -6,6 +6,13 @@ code. These types are interesting in that they are parametrised by other types!
 A ``list[str]`` isn't just a list, it's a list of strings. Types with type
 parameters like this are called *generic types*.
 
+.. note::
+
+   Python 3.12 introduced :pep:`695`, which allows defining generics using
+   type parameter syntax (e.g., ``class Foo[T]:`` and ``def func[T](x: T) -> T:``).
+   The older ``TypeVar`` and ``Generic``-based syntax remains supported
+   for compatibility with earlier Python versions.
+
 You can define your own generic classes that take type parameters, similar to
 built-in types such as ``list[X]``. Note that such user-defined generics are a
 moderately advanced feature and you can get far without ever using them.
@@ -19,11 +26,7 @@ Here is a very simple generic class that represents a stack:
 
 .. code-block:: python
 
-   from typing import TypeVar, Generic
-
-   T = TypeVar('T')
-
-   class Stack(Generic[T]):
+   class Stack[T]:
        def __init__(self) -> None:
            # Create an empty list with items of type T
            self.items: list[T] = []
@@ -37,6 +40,17 @@ Here is a very simple generic class that represents a stack:
        def empty(self) -> bool:
            return not self.items
 
+For compatibility with older Python versions, the same class may be written as:
+
+.. code-block:: python
+
+   from typing import TypeVar, Generic
+
+   T = TypeVar('T')
+
+   class Stack(Generic[T]):
+       ...
+
 The ``Stack`` class can be used to represent a stack of any type:
 ``Stack[int]``, ``Stack[tuple[int, str]]``, etc.
 
@@ -56,7 +70,7 @@ construction of the instance will be type checked correspondingly.
 
 .. code-block:: python
 
-   class Box(Generic[T]):
+   class Box[T]:
        def __init__(self, content: T) -> None:
            self.content = content
 
@@ -96,12 +110,12 @@ can be used as a base class for another class (generic or non-generic). For exam
     data: StrDict[int, int]  # error: "StrDict" expects no type arguments, but 2 given
     data2: StrDict  # OK
 
-   # This is a user-defined generic class
-   class Receiver(Generic[T]):
-       def accept(self, value: T) -> None: ...
+    # This is a user-defined generic class
+    class Receiver(Generic[T]):
+        def accept(self, value: T) -> None: ...
 
-   # This is a generic subclass of Receiver
-   class AdvancedReceiver(Receiver[T]): ...
+    # This is a generic subclass of Receiver
+    class AdvancedReceiver(Receiver[T]): ...
 
 .. note::