@Nullable
    @Contract(pure = true)
    private static Return mergeReturn(@NotNull PsiVariable retVariable, @NotNull PsiVariable lhs, @NotNull PsiExpression rhs) {
      return retVariable != lhs ? null : new Return(rhs);
    }
@Nullable
    @Contract(pure = true)
    private static Return mergeReturn(@NotNull PsiVariable retVariable, @NotNull PsiVariable lhs, @NotNull PsiExpression rhs)