Fix support for TypeVar, TypeVarTupe and ParamSpec

README.rst

@@ -289,9 +289,9 @@ trade-offs to cope with legacy ASTs.
 
         type_ignore = TypeIgnore(int lineno, string tag)
 
-         type_param = TypeVar(identifier name, expr? bound)
-                    | ParamSpec(identifier name)
-                    | TypeVarTuple(identifier name)
+         type_param = TypeVar(identifier name, expr? bound, expr? default_value)
+                    | ParamSpec(identifier name, expr? default_value)
+                    | TypeVarTuple(identifier name, expr? default_value)
                     attributes (int lineno, int col_offset, int end_lineno, int end_col_offset)
     }
 

gast/ast3.py

@@ -5,6 +5,30 @@
 
 
 class Ast3ToGAst(AstToGAst):
+    if sys.version_info.minor == 12:
+
+        def visit_TypeVar(self, node):
+            new_node = gast.TypeVar(
+                self._visit(node.name),
+                self._visit(node.bound),
+                None
+            )
+            return gast.copy_location(new_node, node)
+
+        def visit_TypeVarTuple(self, node):
+            new_node = gast.TypeVarTuple(
+                self._visit(node.name),
+                None
+            )
+            return gast.copy_location(new_node, node)
+
+        def visit_ParamSpec(self, node):
+            new_node = gast.ParamSpec(
+                self._visit(node.name),
+                None
+            )
+            return gast.copy_location(new_node, node)
+
     if sys.version_info.minor < 10:
 
         def visit_alias(self, node):
@@ -265,6 +289,26 @@ def visit_ClassDef(self, node):
 
 
 class GAstToAst3(GAstToAst):
+    if sys.version_info.minor == 12:
+        def visit_TypeVar(self, node):
+            new_node = ast.TypeVar(
+                self._visit(node.name),
+                self._visit(node.bound)
+            )
+            return ast.copy_location(new_node, node)
+
+        def visit_TypeVarTuple(self, node):
+            new_node = ast.TypeVarTuple(
+                self._visit(node.name),
+            )
+            return ast.copy_location(new_node, node)
+
+        def visit_ParamSpec(self, node):
+            new_node = ast.ParamSpec(
+                self._visit(node.name),
+            )
+            return ast.copy_location(new_node, node)
+
     if sys.version_info.minor < 10:
         def visit_alias(self, node):
             new_node = ast.alias(

gast/gast.py

@@ -366,15 +366,15 @@ def _fill_field_types(Name, FieldTypes):
     ('type_ignore', ((), ('lineno', 'tag'), (TypeIgnore,))),
 
     # type_param
-    ('TypeVar', (('name', 'bound',),
+    ('TypeVar', (('name', 'bound', 'default_value'),
                  ('lineno', 'col_offset',
                   'end_lineno', 'end_col_offset'),
                  (type_param,))),
-    ('ParamSpec', (('name',),
+    ('ParamSpec', (('name', 'default_value'),
                  ('lineno', 'col_offset',
                   'end_lineno', 'end_col_offset'),
                  (type_param,))),
-    ('TypeVarTuple', (('name',),
+    ('TypeVarTuple', (('name', 'default_value'),
                  ('lineno', 'col_offset',
                   'end_lineno', 'end_col_offset'),
                  (type_param,))),
@@ -492,9 +492,9 @@ def _fill_field_types(Name, FieldTypes):
         ('MatchOr', (list[pattern],), ),
 
         # type_param
-        ('TypeVar', (str, expr | None), ),
-        ('ParamSpec', (str,), ),
-        ('TypeVarTuple', (str,), ),
+        ('TypeVar', (str, expr | None, expr | None), ),
+        ('ParamSpec', (str, expr | None), ),
+        ('TypeVarTuple', (str, expr | None), ),
     )
 
     for _name, _types in _node_types:

tests/test_py3_12.py

@@ -31,10 +31,12 @@ def test_type_alias(self):
     def test_generic_type_alias(self):
         code = "type Point[T] = tuple[T, float]"
         tree = gast.parse(code)
-        compile(gast.gast_to_ast(tree), '<test>', 'exec')
+        atree = gast.gast_to_ast(tree)
+        compile(atree, '<test>', 'exec')
         norm = ("Module(body=[TypeAlias(name=Name(id='Point', ctx=Store(), "
                 "annotation=None, type_comment=None), type_params=[TypeVar("
-                "name='T', bound=None)], value=Subscript(value=Name(id='tuple'"
+                "name='T', bound=None, default_value=None)], value=Subscript("
+                "value=Name(id='tuple'"
                 ", ctx=Load(), annotation=None, type_comment=None), "
                 "slice=Tuple(elts=[Name(id='T', ctx=Load(), annotation=None, "
                 "type_comment=None), Name(id='float', ctx=Load(), "
@@ -51,7 +53,7 @@ def test_generic_function(self):
                 "kwarg=None, defaults=[]), body=[Expr(value=Constant(value="
                 "Ellipsis, kind=None))], decorator_list=[], returns=None, "
                 "type_comment=None, type_params=[TypeVar(name='T', "
-                "bound=None)])], type_ignores=[])")
+                "bound=None, default_value=None)])], type_ignores=[])")
         self.assertEqual(dump(tree), norm)
 
     def test_generic_class(self):
@@ -60,8 +62,8 @@ def test_generic_class(self):
         compile(gast.gast_to_ast(tree), '<test>', 'exec')
         norm = ("Module(body=[ClassDef(name='foo', bases=[], keywords=[], "
                 "body=[Expr(value=Constant(value=Ellipsis, kind=None))], "
-                "decorator_list=[], type_params=[TypeVar(name='T', bound=None)"
-                "])], type_ignores=[])")
+                "decorator_list=[], type_params=[TypeVar(name='T', bound=None, "
+                "default_value=None)])], type_ignores=[])")
         self.assertEqual(dump(tree), norm)
 
 if sys.version_info < (3, 12):