pythongh-109341: Fix crash on compiling invalid AST including TypeAlias

Lib/test/test_compile.py

@@ -478,6 +478,26 @@ def test_compile_ast(self):
         ast.body = [_ast.BoolOp()]
         self.assertRaises(TypeError, compile, ast, '<ast>', 'exec')
 
+    def test_compile_invalid_typealias(self):
+        # gh-109341
+        m = ast.Module(
+            body=[
+                ast.TypeAlias(
+                    name=ast.Subscript(
+                        value=ast.Name(id="foo", ctx=ast.Load()),
+                        slice=ast.Constant(value="x"),
+                        ctx=ast.Store(),
+                    ),
+                    type_params=[],
+                    value=ast.Name(id="Callable", ctx=ast.Load()),
+                )
+            ],
+            type_ignores=[],
+        )
+
+        with self.assertRaises(SyntaxError):
+            compile(ast.fix_missing_locations(m), "<file>", "exec")
+
     def test_dict_evaluation_order(self):
         i = 0
 

Misc/NEWS.d/next/Core and Builtins/2023-09-12-15-45-49.gh-issue-109341.4V5bkm.rst

@@ -0,0 +1 @@
+Fix crash when compiling an invalid AST involving a :class:`ast.TypeAlias`.

Python/symtable.c

@@ -1581,7 +1581,12 @@ symtable_visit_stmt(struct symtable *st, stmt_ty s)
     }
     case TypeAlias_kind: {
         VISIT(st, expr, s->v.TypeAlias.name);
-        assert(s->v.TypeAlias.name->kind == Name_kind);
+        // This is only possible for a manually created AST
+        if (s->v.TypeAlias.name->kind != Name_kind) {
+            PyErr_SetString(PyExc_SyntaxError,
+                            "Type alias name must be a simple name");
+            VISIT_QUIT(st, 0);
+        }
         PyObject *name = s->v.TypeAlias.name->v.Name.id;
         int is_in_class = st->st_cur->ste_type == ClassBlock;
         int is_generic = asdl_seq_LEN(s->v.TypeAlias.type_params) > 0;