diff --git a/autoload/lsc/complete.vim b/autoload/lsc/complete.vim
index f5cac8bb..81466dcb 100644
--- a/autoload/lsc/complete.vim
+++ b/autoload/lsc/complete.vim
@@ -100,22 +100,28 @@ function! s:startCompletion() abort
   let s:completion_id += 1
   let s:completion_canceled = v:false
   call s:MarkCompleting(&filetype)
-  let data = {'old_pos': getcurpos(),
-      \ 'completion_id': s:completion_id,
-      \ 'filetype': &filetype}
-  function data.trigger(completion)
-    call s:MarkNotCompleting(self.filetype)
-    if s:isCompletionValid(self.old_pos, self.completion_id)
+  let old_pos = getcurpos()
+  let completion_id = s:completion_id
+  let filetype = &filetype
+  function! OnComplete(completion) closure abort
+    let completions = s:CompletionItems(a:completion)
+    call s:MarkNotCompleting(filetype)
+    if s:isCompletionValid(old_pos, completion_id)
       if (g:lsc_enable_autocomplete)
-        call s:SuggestCompletions(a:completion)
+        call s:SuggestCompletions(completions)
       else
-        let b:lsc_completion = a:completion
+        let b:lsc_completion = completions
       endif
     else
       let b:lsc_is_completing = v:false
     endif
   endfunction
-  call s:SearchCompletions(data.trigger)
+  call lsc#file#flushChanges()
+  let params = { 'textDocument': {'uri': lsc#util#documentUri()},
+      \ 'position': {'line': line('.') - 1, 'character': col('.') - 1}
+      \ }
+  call lsc#server#call(&filetype, 'textDocument/completion', params,
+      \ funcref('OnComplete'))
 endfunction
 
 function! s:SuggestCompletions(completion) abort
@@ -170,7 +176,7 @@ endfunction
 function! s:FindSuggestions(base, completion) abort
   let items = copy(a:completion.items)
   if len(a:base) == 0 | return items | endif
-  return filter(items, '<SID>MatchSuggestion(a:base, v:val)')
+  return filter(items, {_, item -> s:MatchSuggestion(a:base, item)})
 endfunction
 
 function! s:MatchSuggestion(base, suggestion) abort
@@ -179,17 +185,6 @@ function! s:MatchSuggestion(base, suggestion) abort
   return word =~? a:base
 endfunction
 
-" Flush file contents and call the server to request completions for the current
-" cursor position.
-function! s:SearchCompletions(onFound) abort
-  call lsc#file#flushChanges()
-  let params = { 'textDocument': {'uri': lsc#util#documentUri()},
-      \ 'position': {'line': line('.') - 1, 'character': col('.') - 1}
-      \ }
-  call lsc#server#call(&filetype, 'textDocument/completion', params,
-      \ lsc#util#compose(a:onFound, function('<SID>CompletionItems')))
-endfunction
-
 " Normalize LSP completion suggestions to the format used by vim.
 "
 " Returns a dict with:
@@ -205,7 +200,7 @@ function! s:CompletionItems(completion_result) abort
   else
     let completion_items = a:completion_result.items
   endif
-  call map(completion_items, 's:CompletionItem(v:val)')
+  call map(completion_items, {_, item -> s:CompletionItem(item)})
   let completion = {'items' : completion_items}
   for item in completion_items
     if has_key(item, 'start_col')
diff --git a/autoload/lsc/diagnostics.vim b/autoload/lsc/diagnostics.vim
index aae9dada..b01aedad 100644
--- a/autoload/lsc/diagnostics.vim
+++ b/autoload/lsc/diagnostics.vim
@@ -14,7 +14,7 @@ endif
 
 " Converts between an LSP diagnostic and the internal representation used for
 " highlighting.
-function! lsc#diagnostics#convert(diagnostic) abort
+function! s:Convert(diagnostic) abort
   let line = a:diagnostic.range.start.line + 1
   let character = a:diagnostic.range.start.character + 1
   " TODO won't work for multiline error
@@ -81,7 +81,7 @@ function! s:DiagnosticsVersion(file_path) abort
 endfunction
 
 function! lsc#diagnostics#setForFile(file_path, diagnostics) abort
-  call map(a:diagnostics, 'lsc#diagnostics#convert(v:val)')
+  call map(a:diagnostics, {_, diagnostic -> s:Convert(diagnostic)})
   let diagnostics_by_line = {}
   for diagnostic in a:diagnostics
     if !has_key(diagnostics_by_line, diagnostic.range[0])
diff --git a/autoload/lsc/reference.vim b/autoload/lsc/reference.vim
index 16c0f17b..f60c2244 100644
--- a/autoload/lsc/reference.vim
+++ b/autoload/lsc/reference.vim
@@ -1,10 +1,10 @@
 function! lsc#reference#goToDefinition() abort
   call lsc#file#flushChanges()
   let s:goto_definition_id += 1
-  let data = {'old_pos': getcurpos(),
-      \ 'goto_definition_id': s:goto_definition_id}
-  function data.trigger(result) abort
-    if !s:isGoToValid(self.old_pos, self.goto_definition_id)
+  let old_pos = getcurpos()
+  let goto_definition_id = s:goto_definition_id
+  function! Jump(result) closure abort
+    if !s:isGoToValid(old_pos, goto_definition_id)
       echom 'GoToDefinition skipped'
       return
     endif
@@ -23,7 +23,7 @@ function! lsc#reference#goToDefinition() abort
     call s:goTo(file, line, character)
   endfunction
   call lsc#server#call(&filetype, 'textDocument/definition',
-      \ s:TextDocumentPositionParams(), data.trigger)
+      \ s:TextDocumentPositionParams(), function('Jump'))
 endfunction
 
 function! s:TextDocumentPositionParams() abort
@@ -41,7 +41,7 @@ function! lsc#reference#findReferences() abort
 endfunction
 
 function! s:setQuickFixReferences(results) abort
-  call map(a:results, 's:QuickFixItem(v:val)')
+  call map(a:results, {_, ref -> s:QuickFixItem(ref)})
   call sort(a:results, 'lsc#util#compareQuickFixItems')
   call setqflist(a:results)
   copen
diff --git a/autoload/lsc/server.vim b/autoload/lsc/server.vim
index e93d79fb..67d166de 100644
--- a/autoload/lsc/server.vim
+++ b/autoload/lsc/server.vim
@@ -88,8 +88,7 @@ function! s:RunCommand(command) abort
   let channel = job_getchannel(job)
   let ch_id = ch_info(channel)['id']
   let s:channel_buffers[ch_id] = ''
-  let data = {'command': a:command, 'channel': channel}
-  function data.onInitialize(params) abort
+  function! OnInitialize(params) closure abort
     " TODO: Check capabilities?
     if has_key(a:params, 'capabilities')
       let capabilities = a:params['capabilities']
@@ -98,18 +97,18 @@ function! s:RunCommand(command) abort
         if has_key(completion_provider, 'triggerCharacters')
           let trigger_characters = completion_provider['triggerCharacters']
           for filetype in keys(g:lsc_server_commands)
-            if g:lsc_server_commands[filetype] != self.command | continue | endif
+            if g:lsc_server_commands[filetype] != a:command | continue | endif
             call lsc#complete#setTriggers(filetype, trigger_characters)
           endfor
         endif
       endif
     endif
-    call add(s:initialized_servers, self.command)
-    if has_key(s:buffered_calls, self.command)
-      for buffered_call in s:buffered_calls[self.command]
-        call ch_sendraw(self.channel, buffered_call)
+    call add(s:initialized_servers, a:command)
+    if has_key(s:buffered_calls, a:command)
+      for buffered_call in s:buffered_calls[a:command]
+        call ch_sendraw(channel, buffered_call)
       endfor
-      unlet s:buffered_calls[self.command]
+      unlet s:buffered_calls[a:command]
     endif
   endfunction
   if exists('g:lsc_trace_level') &&
@@ -124,7 +123,7 @@ function! s:RunCommand(command) abort
       \ 'trace': trace_level
       \}
   call lsc#server#call(&filetype, 'initialize',
-      \ params, data.onInitialize, v:true)
+      \ params, function('OnInitialize'), v:true)
   return v:true
 endfunction
 
diff --git a/autoload/lsc/util.vim b/autoload/lsc/util.vim
index bc8e546c..78f3a0e9 100644
--- a/autoload/lsc/util.vim
+++ b/autoload/lsc/util.vim
@@ -18,22 +18,6 @@ function! lsc#util#documentPath(uri) abort
   return substitute(a:uri, '^file://', '', 'v')
 endfunction
 
-" Returns a funcref which is the result of first calling `inner` and then using
-" the result as the argument to `outer`. `inner` may take any number of
-" arguments, but `outer` must  take a single argument.
-"
-" For examples lsc#util#compose(g, f) returns a function (args) => g(f(args)).
-function! lsc#util#compose(outer, inner) abort
-  let data = {'funcs': [a:outer, a:inner]}
-  function data.composed(...) abort
-    let Outer = self['funcs'][0]
-    let Inner = self['funcs'][1]
-    let result = call(Inner, a:000)
-    return call(Outer, [result])
-  endfunction
-  return data.composed
-endfunction
-
 function! lsc#util#error(message) abort
   echohl Error
   echom '[lsc] '.a:message
@@ -111,7 +95,7 @@ endfunction
 function! s:createOrJumpToPreview(line_count) abort
   let want_height = min([a:line_count, &previewheight])
   let windows = range(1, winnr('$'))
-  call filter(windows, 'getwinvar(v:val, "&previewwindow") == 1')
+  call filter(windows, {_, win -> getwinvar(win, "&previewwindow") == 1})
   if len(windows) > 0
     execute string(windows[0]).' wincmd W'
     edit __lsc_preview__