@Nullable
  static PsiType commonType(@NotNull ExtractableExpressionPart part1, @NotNull ExtractableExpressionPart part2) {
    return commonType(part1.myType, part2.myType);
  }
@Nullable
  static PsiType commonType(@NotNull ExtractableExpressionPart part1, @NotNull ExtractableExpressionPart part2)