Smart (`infercase`) Dictionary Completions in Vim Without Otherwise Messing with Your `ignorecase` Settings

smartcase-dict-complete.vim

function! s:_setup_cidictcompletion()
    let g:_old_ignorecase_state=&ignorecase
    inoremap <C-X><C-K> <ESC>:let g:_old_ignorecase_state=&ignorecase<CR>:set ignorecase<CR>:set infercase<CR>a<C-X><C-K>
    " inoremap <expr> <CR> pumvisible() ? "\<C-y><ESC>:set noignorecase<CR>a" : "\<C-g>u\<CR>"
    " inoremap <expr> <C-J> pumvisible() ? "\<C-y><ESC>:set noignorecase<CR>a" : "\<C-g>u\<C-J>"
    let restore=' pumvisible() ? "\<C-y><ESC>:let &ignorecase=g:_old_ignorecase_state<CR>'
    for key in ["<CR>", "<C-J>", "<C-Y>"]
        execute "inoremap <expr> " . key . restore . 'a" : "\<C-g>u\<CR>"'
    endfor
    for key in ["<ESC>", "<C-C>"]
        execute "inoremap <expr> " . key . restore . '" : "\' . key . '"'
    endfor
endfunction
call <SID>_setup_cidictcompletion()