[BUG] Strange behavior when cchar is a special character
- If you launch vim the following way:
vim -u NONE --cmd 'set nocompatible conceallevel=2' --cmd $'syn keyword Ctest cchar=\t conceal abc' -c $'normal! aabc\n'
then you will see only two empty lines on the terminal. If you then
press j and k, then you will first see ``abc'' on the first line
and then ``a''. Nothing is higlighted with Concealed highlight group.
The same thing will happen if you replace ``\t'' with ``\n'', ``\r'',
``\C-t'' (Control+T, ``\x14'', looks like that escape is not working
in bash) and other ``\C-*''.
I think that ``:syn'' command should throw an error on this characters
instead of trying to use them in some way.