[Backport maintenance/3.0.x] Fix undefined-variable etc for Python 3.12 generic type syntax

doc/whatsnew/fragments/9193.false_positive

@@ -0,0 +1,4 @@
+Fix false positives for ``undefined-variable`` and ``unused-argument`` for
+classes and functions using Python 3.12 generic type syntax.
+
+Closes #9193

pylint/checkers/variables.py

@@ -1738,6 +1738,9 @@ def _should_node_be_skipped(
         elif consumer.scope_type == "function" and self._defined_in_function_definition(
             node, consumer.node
         ):
+            if any(node.name == param.name.name for param in consumer.node.type_params):
+                return False
+
             # If the name node is used as a function default argument's value or as
             # a decorator, then start from the parent frame of the function instead
             # of the function frame - and thus open an inner class scope
@@ -2262,10 +2265,13 @@ def _is_variable_violation(
                     isinstance(defframe, nodes.FunctionDef)
                     and frame is defframe
                     and defframe.parent_of(node)
-                    and stmt is not defstmt
+                    and (
+                        defnode in defframe.type_params
+                        # Single statement function, with the statement on the
+                        # same line as the function definition
+                        or stmt is not defstmt
+                    )
                 ):
-                    # Single statement function, with the statement on the
-                    # same line as the function definition
                     maybe_before_assign = False
                 elif (
                     isinstance(defstmt, NODES_WITH_VALUE_ATTR)

tests/functional/u/undefined/undefined_variable_py312.py

@@ -0,0 +1,7 @@
+# pylint: disable=missing-function-docstring,missing-module-docstring,missing-class-docstring,too-few-public-methods
+
+def f[T](a: T) -> T:
+    print(a)
+
+class ChildClass[T, *Ts, **P]:
+    ...

tests/functional/u/undefined/undefined_variable_py312.rc

@@ -0,0 +1,2 @@
+[testoptions]
+min_pyver=3.12