fix last spelling mistake by Ctrl-Q; press repeatedly to cycle through suggestions; proceed to penultimate mistake after a one-second timeout

spell-correct-cycle.vim

" Fix last spelling mistake by Ctrl-Q;
" press repeatedly to cycle through suggestions;
" proceed to penultimate mistake after a one-second timeout.

inoremap <silent><expr> <c-q>      &l:spell ? "<c-g>u<c-o>:<c-u>call FixLastSpellingError()<cr><c-g>u"      : "<c-q>"

function! s:FixLastSpellingError(count) abort
  let l:pos = getpos('.')[1:3]
  let l:len0 = len(getline('.'))

  execute 'normal!' '[s' .. a:count .. 'z='

  let l:len1  = len(getline('.'))
  let l:offset = l:len1 - l:len0
  let l:pos[1] = max([l:pos[1] + l:offset, 0])
  call cursor(l:pos)
endfunction

function! s:SpellTimerCB(timer) abort
  let s:spell_count = 0
  let s:spell_timer = 0
  let &l:undolevels = get(b:, 'undolevels', &g:undolevels)
  unlet! b:undolevels
endfunction
call s:SpellTimerCB(0)

function! FixLastSpellingErrorTimed() abort
  " restart timeout
  if s:spell_timer != 0
    call timer_stop(s:spell_timer)
    undo
    normal! g``
  else
    let b:undolevels = &l:undolevels
    let &l:undolevels = 1
  endif
  let s:spell_timer = timer_start(1000, function('s:SpellTimerCB'))
  " Bump counter and apply suggestion
  let s:spell_count += 1
  call s:FixLastSpellingError(s:spell_count)
endfunction