Fix haskell layer

autoload/SpaceVim/layers/lang/haskell.vim

@@ -4,19 +4,13 @@ function! SpaceVim#layers#lang#haskell#plugins() abort
         \ ['pbrisbin/vim-syntax-shakespeare', { 'on_ft': 'haskell' }],
         \ ]
 
-  if !s:use_lsp
+  if SpaceVim#layers#lsp#check_filetype('haskell')
     call add(plugins, ['eagletmt/neco-ghc', { 'on_ft': 'haskell' }])
   endif
 
   return plugins
 endfunction
 
-let s:use_lsp = 0
-
-function! SpaceVim#layers#lang#haskell#set_variable(var) abort
-  let s:use_lsp = get(a:var, 'use_lsp', 0) && has('nvim') && executable('hie')
-endfunction
-
 function! SpaceVim#layers#lang#haskell#config() abort
   let g:haskellmode_completion_ghc = 0
 
@@ -26,7 +20,7 @@ function! SpaceVim#layers#lang#haskell#config() abort
   call SpaceVim#mapping#space#regesit_lang_mappings('haskell',
         \ funcref('s:on_ft'))
 
-  if s:use_lsp
+  if SpaceVim#layers#lsp#check_filetype('haskell')
     call SpaceVim#mapping#gd#add('haskell',
           \ function('SpaceVim#lsp#go_to_def'))
     call SpaceVim#lsp#reg_server('haskell', ['hie', '--lsp'])
@@ -35,14 +29,14 @@ function! SpaceVim#layers#lang#haskell#config() abort
   augroup SpaceVim_lang_haskell
     autocmd!
 
-    if !s:use_lsp
+  if SpaceVim#layers#lsp#check_filetype('haskell')
       autocmd FileType haskell setlocal omnifunc=necoghc#omnifunc
     endif
   augroup END
 endfunction
 
 function! s:on_ft() abort
-  if s:use_lsp
+  if SpaceVim#layers#lsp#check_filetype('haskell')
     nnoremap <silent><buffer> K :call SpaceVim#lsp#show_doc()<CR>
 
     call SpaceVim#mapping#space#langSPC('nnoremap', ['l', 'd'],

autoload/SpaceVim/layers/lsp.vim

@@ -69,6 +69,7 @@ let s:enabled_fts = []
 
 let s:lsp_servers = {
       \ 'javascript' : ['javascript-typescript-stdio'],
+      \ 'haskell' : ['hie', '--lsp'],
       \ }
 
 function! SpaceVim#layers#lsp#set_variable(var) abort

docs/layers/lang/haskell.md

@@ -27,4 +27,5 @@ To use this configuration layer, add `call SpaceVim#layers#load('lang#haskell')`
 - syntax checking
 - goto definition
 - refernce finder
+- language server protocol (need lsp layer) 
 

docs/layers/language-server-protocol.md

@@ -44,6 +44,7 @@ default language server commands:
 | language     | server command                    |
 | ------------ | --------------------------------- |
 | `javascript` | `['javascript-typescript-stdio']` |
+| `haskell`    | `['hie', '--lsp']`                |
 
 To override the server command, you may need to use `override_cmd` option: