code: public static MemberExistsResult constructorExists(JavacNode node) {
  		node = upToTypeNode(node);
  		
  		if (node != null && node.get() instanceof JCClassDecl) {
  			for (JCTree def : ((JCClassDecl)node.get()).defs) {
  				if (def instanceof JCMethodDecl) {
  					JCMethodDecl md = (JCMethodDecl) def;
  					if (md.name.contentEquals("<init>")) {
  						if ((md.mods.flags & Flags.GENERATEDCONSTR) != 0) continue;
  						if (isTolerate(node, md)) continue;
  						return getGeneratedBy(def) == null ? MemberExistsResult.EXISTS_BY_USER : MemberExistsResult.EXISTS_BY_LOMBOK;
  					}
  				}
  			}
  		}
  		
  		return MemberExistsResult.NOT_EXISTS;
  	}
docs: Checks if there is a (non-default) constructor. In case of multiple constructors (overloading), only
  the first constructor decides if EXISTS_BY_USER or EXISTS_BY_LOMBOK is returned.
  
  @param node Any node that represents the Type (JCClassDecl) to look in, or any child node thereof.