Failed to parse nextcloud config

config.php

..
'memcached_servers' => [
  ['127.0.0.1', 11211],
],
'memcached_options' => [
  \Memcached::OPT_SERIALIZER => \Memcached::SERIALIZER_IGBINARY,
],
...

error

Nov 12 20:37:49 nbg1-ceph notify_push[1054841]: Error:
Nov 12 20:37:49 nbg1-ceph notify_push[1054841]:    0: #033[91mFailed to parse config#033[0m
Nov 12 20:37:49 nbg1-ceph notify_push[1054841]:    1: #033[91mFailed to parse nextcloud config#033[0m
Nov 12 20:37:49 nbg1-ceph notify_push[1054841]:    2: #033[91mError while parsing '/config/config.php':
Nov 12 20:37:49 nbg1-ceph notify_push[1054838]:    2: #033[m#033[1m#033[38;5;12m86 | #033[m    \Memcached::OPT_SERIALIZER => \Memcached::SERIALIZER_IGBINARY,
Nov 12 20:37:49 nbg1-ceph notify_push[1054838]:    2:    #033[1m#033[38;5;12m|     #033[1m#033[38;5;9m^^ No valid token found, expected one of boolean literal, integer literal, float literal, string literal, 'null', ']', 'array' or '['
Nov 12 20:37:49 nbg1-ceph notify_push[1054841]:    2:
Nov 12 20:37:49 nbg1-ceph notify_push[1054841]:    2: #033[m#033[1m#033[38;5;12m.. |
Nov 12 20:37:49 nbg1-ceph notify_push[1054841]:    2: #033[m#033[1m#033[38;5;12m85 | #033[m  ],
Nov 12 20:37:49 nbg1-ceph notify_push[1054838]:    2: #033[m#033[1m#033[38;5;12m87 | #033[m  ],
Nov 12 20:37:49 nbg1-ceph notify_push[1054838]:    2: #033[m#033[1m#033[38;5;12m88 | #033[m);
Nov 12 20:37:49 nbg1-ceph notify_push[1054838]:    2: #033[m#033[0m

It is ok with:

'memcached_servers' =>
  array (
    0 =>
    array (
      0 => '127.0.0.1',
      1 => 11211,
    ),
  ),
'memcached_options' =>
  array (
    -1003 => 2,
  ),

Reproduce the failure with the shown config.php containing short arrays and Memcached constants, then locate the parser path that reports the error. Compare it with the expanded array form that succeeds; done means the compact configuration parses successfully and the regression is covered by a test.