"Unexpected "$smarty.block.parent"" in default modifier.

[AnrDaemon]

{block "content"}{$content|default:$smarty.block.parent}{/block}

emits

PHP Fatal error:  Uncaught  --> Smarty Compiler: Syntax error in template "file:legacy-page.tpl"  on line 10
"{block "content"}{$content|default:$smarty.block.parent}{/block}"  - Unexpected "$smarty.block.parent" <-- 
  thrown in …/sysplugins/smarty_internal_templatecompilerbase.php on line 10

There's a simple workaround, however

{block "content"}{$content|default:{$smarty.block.parent}}{/block}

but I'm not sure the original behavior is desired.

[uwetews]

Never considered that $smarty.block.parent could be used as |default: value.
I will change hat ASAP

[AnrDaemon]

Shouldn't any variable reference be acceptable as parameter value?
I've seen similar behavior with cache_id parameters of '{include}' blocks.

[AnrDaemon]

And to clarify the original use case, I have the following structure:

parent.tpl

{block "content"}<div>error message</div>{/block}

child.tpl

{block "content"}{$content|default:$smarty.block.parent}{/block}

[uwetews]

This is now fixed in the master branch.

Can you explain the behavior with cache_id parameters of '{include}' blocks you have mentioned.

[AnrDaemon]

First time I started to port my current project forward, I've tried to dynamically assign cache ids to various includes (mainly various menu blocks), but failed because it would crash on anything but a plain variable.
I'm unable to reproduce it now, and it was so long ago that it may have been fixed already.
If it would resurface anywhere, I will file a new issue.