DiagnosticSeverity according to implementation https://github.com/Microsoft/vscode-languageserver-node instead of documentation https://github.com/Microsoft/language-server-protocol/blob/master/protocol.md;

--- a/src/Tools/VSCode/src/protocol.scala	Wed Dec 28 20:17:01 2016 +0100
+++ b/src/Tools/VSCode/src/protocol.scala	Wed Dec 28 20:33:43 2016 +0100
@@ -327,10 +327,10 @@
 
   object DiagnosticSeverity
   {
-    val Error = 1
-    val Warning = 2
-    val Information = 3
-    val Hint = 4
+    val Error = 0
+    val Warning = 1
+    val Information = 2
+    val Hint = 3
   }
 
   object PublishDiagnostics