Too strict typechecking in Pike 8.0

[Stephen R. van den Berg]

Pike v8.0 release 31 running Hilfe v3.5 (Incremental Pike Frontend)

(<"1">)->any;

Compiler Warning: 1: Indexing on illegal type.
Compiler Warning: 1: Got : multiset(string(49..49)).
Compiler Warning: 1: Index : string(97..121).

This piece of code is from Roxen 6.0 base_server/roxen.pike
around line 7455:

" if ((user || (user = authmethod->authenticate(id, userdb_module)))\n"
" && ((%[0]s->any && sizeof(user->groups())) ||\n"
" sizeof(mkmultiset(user->groups())&%[0]s)))",

And it is triggered by a sole "allow group=1" security rule for some
filesystem module.
I presume this needs to be fixed in Pike, as opposed to in Roxen.