public @NotNull CompletionResult withLookupElement(@NotNull LookupElement element) {
    if (!myMatcher.prefixMatches(element)) {
      throw new AssertionError("The new element doesn't match the prefix");
    }
    return new CompletionResult(element, myMatcher, mySorter);
  }
public @NotNull CompletionResult withLookupElement(@NotNull LookupElement element)