Annoying completion result for options value

[4513ECHO]

Describe the bug
A clear and concise description of what the bug is.

vim-language-server returns annoying completion results when we trigger completion in value of options.
Even the option does not accept vim script expression (e.g. 'encoding', 'formatoptions'), LS suggests vim script variables.

To Reproduce
Steps to reproduce the behavior:

1. Start completion with leading text like set encoding=

Expected behavior

vim-language-server should return the result following context.

Screenshots

Desktop (please complete the following information):

• OS: macOS Sonoma 14.5

[Shougo]

I think it is vimlparser issue instead.

https://github.com/vim-jp/vim-vimlparser

Hm. vim-language-server parse statement directly.