bpo-35879: Fix type comment leaks (GH-11728)

* Fix leak for # type: ignore
* Fix the type comment leak

Parser/parsetok.c

@@ -330,6 +330,7 @@ parsetok(struct tok_state *tok, grammar *g, int start, perrdetail *err_ret,
         }
 
         if (type == TYPE_IGNORE) {
+            PyObject_FREE(str);
             if (!growable_int_array_add(&type_ignores, tok->lineno)) {
                 err_ret->error = E_NOMEM;
                 break;

Python/ast.c

@@ -699,11 +699,16 @@ ast_error(struct compiling *c, const node *n, const char *errmsg, ...)
 */
 
 static string
-new_type_comment(const char *s)
+new_type_comment(const char *s, struct compiling *c)
 {
-  return PyUnicode_DecodeUTF8(s, strlen(s), NULL);
+    PyObject *res = PyUnicode_DecodeUTF8(s, strlen(s), NULL);
+    if (PyArena_AddPyObject(c->c_arena, res) < 0) {
+        Py_DECREF(res);
+        return NULL;
+    }
+    return res;
 }
-#define NEW_TYPE_COMMENT(n) new_type_comment(STR(n))
+#define NEW_TYPE_COMMENT(n) new_type_comment(STR(n), c)
 
 static int
 num_stmts(const node *n)