static void addReturnTypeToStandardFunction(S sfName, S returnType) {
  S snippetID = stdFunctions_cached().get(sfName);
  if (snippetID == null) fail("Function not found: " + sfName);
  S text = addReturnTypeToMethod(loadSnippet(snippetID), returnType);
  editSnippetVerbose(snippetID, text);
}