function! s:map ()
 map <buffer> <Return> <Cmd>exe 'wincmd p \|' line('.') 'cc'<CR>
endfunction

function! s:unmap ()
 unmap <buffer> <Return>
endfunction

function! s:list ()
  return expand('<amatch>')[0] == 'l' ? getloclist(0) : getqflist()
endfunction

autocmd! QuickFixCmdPost * if !empty(s:list()) | wincmd p | endif
autocmd! BufWinEnter * if &buftype == 'quickfix' | call s:map() | endif
autocmd! BufWinLeave * if &buftype == 'quickfix' | call s:unmap() | endif