String (PsiTreeChangeEvent event, PsiTreeChangeEventImpl.PsiEventType code) { PsiElement parent = event.getParent(); PsiElement oldChild = event.getOldChild(); if (oldChild == null) oldChild = event.getChild(); PsiElement newChild = event.getNewChild(); return code + ":" + (parent == null ? null : parent.getNode().getElementType()) + "/" + (oldChild == null ? null : oldChild.getNode().getElementType()) + "->" + (newChild == null ? null : newChild.getNode().getElementType()) + ";"; }