vim - ft-syntax-omni is not working -

looks ft-syntax-omni has ability fill omni auto completion list syntax highlighting, couldn't work:

in vimrc, i've got:

au bufread,bufnewfile *.idc set ft=idc au bufread,bufnewfile *.idc setlocal omnifunc=syntaxcomplete#complete 

and i'm using syntax highlighting file here, highlighting works fine.

but list wasn't populated, nothing ^x^o

though didn't find definite answer implementation, fact :help ft-syntax-omni speaks about

... knowing keywords part of language.

i think limited :syntax keyword definitions. syntax/idc.vim uses :syntax match, specifies regular expression pattern. feed insert mode completion, need concrete matches (e.g. foobar), not patterns (like /f.*bar/), think either have rewrite syntax define keywords, or use means of completion, e.g. dictionary completion separate file.