nvim: Enable LSP support for Haskell

With ghcide release v0.2.0 adding multi-component support this should
work more widely now. We still can have tags, so change the key binding
for jump to definition and drop key binding K for Hoogle.

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>

nvim/.config/nvim/after/ftplugin/haskell.vim

@@ -2,7 +2,6 @@
 " https://github.com/maxigit/vimrc/tree/2020/compiler
 compiler stack
 setlocal makeprg=stack\ build
-setlocal keywordprg=:Hoogle
 
 nmap <buffer> <LocalLeader>t  :AsyncDo stack exec -- hasktags -x -c .<CR>
 nmap <buffer> <LocalLeader>td :AsyncDo stack exec -- haskdogs<CR>

nvim/.config/nvim/lua/lsp.lua

@@ -6,7 +6,7 @@ local on_attach = function(_, bufnr)
   require'completion'.on_attach()
 
   local opts = { noremap=true, silent=true }
-  vim.api.nvim_buf_set_keymap(bufnr, 'n', '<C-]>', '<cmd>lua vim.lsp.buf.definition()<CR>', opts)
+  vim.api.nvim_buf_set_keymap(bufnr, 'n', 'gd', '<cmd>lua vim.lsp.buf.definition()<CR>', opts)
   vim.api.nvim_buf_set_keymap(bufnr, 'n', 'K',  '<cmd>lua vim.lsp.buf.hover()<CR>', opts)
   vim.api.nvim_buf_set_keymap(bufnr, 'n', 'gr', '<cmd>lua vim.lsp.buf.references()<CR>', opts)
   vim.api.nvim_buf_set_keymap(bufnr, 'n', 'gD', '<cmd>lua vim.lsp.util.show_line_diagnostics()<CR>', opts)
@@ -19,7 +19,7 @@ local on_attach = function(_, bufnr)
   vim.api.nvim_buf_set_keymap(bufnr, 'n', '<Leader>rn', '<cmd>lua vim.lsp.buf.rename()<CR>', opts)
 end
 
-local servers = { 'rust_analyzer' }
+local servers = { 'ghcide', 'rust_analyzer' }
 for _, lsp in ipairs(servers) do
   nvim_lsp[lsp].setup {
   on_attach = on_attach,

nvim/.config/nvim/plugin_settings.vim

@@ -82,6 +82,7 @@ let g:completion_chain_complete_list = {
   \    {'mode': '<c-n>'}
   \],
   \ 'haskell': [
+  \    {'complete_items': ['lsp']},
   \    {'mode': 'keyn'},
   \    {'mode': 'tags'},
   \    {'mode': '<c-p>'},