Use nvim-notify for showing messages

autoload/buf_utils.vim

@@ -11,7 +11,11 @@ function! buf_utils#GoToBuffer(count, direction) abort
   endif
   " Check the validity of buffer number.
   if index(s:GetBufNums(), a:count) == -1
-    call utils#Log('Invalid bufnr: ' . a:count, 'error')
+    " Using `lua vim.notify('invalid bufnr: ' .. a:count)` won't work, because
+    " we are essentially mixing Lua and vim script. We need to make sure that
+    " args inside vim.notify() are valid vim values. The conversion from vim
+    " value to lua value will be done by Nvim. See also https://github.com/neovim/neovim/pull/11338.
+    call v:lua.vim.notify('Invalid bufnr: ' . a:count, 'error', {'title': 'nvim-config'})
     return
   endif
 

autoload/utils.vim

@@ -145,25 +145,3 @@ function! utils#Get_titlestr() abort
 
   return l:title_str
 endfunction
-
-" Log a message using certain highlight group
-function! utils#Log(msg, ...) abort
-  let l:hi = ''
-  if len(a:000) == 1
-    if a:1 ==? 'info'
-      let l:hi = 'Normal'
-    elseif a:1 ==? 'warning'
-      let l:hi = 'WarningMsg'
-    elseif a:1 ==? 'error'
-      let l:hi = 'ErrorMsg'
-    else
-      echoerr 'Unsupported log level:' a:1
-    endif
-  else
-    let l:hi = 'Normal'
-  endif
-
-  execute 'echohl' l:hi
-  unsilent echomsg a:msg
-  echohl None
-endfunction