Can signatures be made simpler and error messages be made better?

[zjh]

On Sunday, 13 June 2021 at 01:00:11 UTC, Elronnd wrote:
> On Saturday, 12 June 2021 at 08:58:47 UTC, zjh wrote:

See if we need the starting point of lifetime.
If you need, it is range. range relations are:` include 
(included), equal (unequal), intersect (or not)`.
If you don't care `starting point`, just care `ending 
point`.Lifetime is of `comparing` relation.