[ruby-core:96389] [Ruby master Bug#16440] Date range inclusion behaviors are inconsistent

Issue #16440 has been updated by st0012 (Stan Lo).


To: wishdev (John Higgins)

> (and in fact on my system - the to_time option returns false instead of true).

Sorry that I accidentally tested my code in a Rails console instead of pure irb. The result for that case should be `false` on my machine as well.

Let me correct this:

```
may1 = Date.parse("2019-05-01")
may3 = Date.parse("2019-05-03")
noon_of_may3 = DateTime.parse("2019-05-03 12:00")
may31 = Date.parse("2019-05-31")

(may1..may31).include? may3 # => True
(may1..may31).include? may3.to_time # => False
(may1..may31).include? may3.to_datetime # => True
(may1..may31).include? noon_of_may3 # => False
```


To: zverok (Victor Shepelev) and  shevegen (Robert A. Heiler)

I think semantically, `cover` might be a better API for such cases. But I'm like `shevegen` don't use `cover` that often. In fact, I completely forgot about it!

However, I think my question of this issue is: 

Does a Date range represent a series of individual days between May 1st and May 31th, like `[2019-05-01 00:00:00, 2019-05-02 00:00:00..... 2019-05-31 00:00:00]` ? Or it represents a continuous time range that starts from May 1st's 00:00 to May 31th's 00:00?

If it's the first case, I can understand that `include?` doesn't return `true` for `noon_of_may3`. Because it's not at `00:00:00` of that day. But at the same time, I think it should return `true` for `(may1..may31).include? may3.to_time` as well because it's at `00:00:00` of that day.

```
may3.to_time #=> 2019-05-03 00:00:00 +0000
```

If it's the second case, we should make all 4 cases return `true` because they're all covered by the range.


What do you guys think?


----------------------------------------
Bug #16440: Date range inclusion behaviors are inconsistent
https://bugs.ruby-lang.org/issues/16440#change-83312

* Author: st0012 (Stan Lo)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.6.5p114 (2019-10-01 revision 67812) [x86_64-darwin19]
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN
----------------------------------------
It's weird that a Date range can include Time and DateTime objects that were converted from a Date object. But it can't include a newly generated DateTime object. For example:

```
may1 = Date.parse("2019-05-01")
may3 = Date.parse("2019-05-03")
noon_of_may3 = DateTime.parse("2019-05-03 12:00")
may31 = Date.parse("2019-05-31")

(may1..may31).include? may3 # => True
(may1..may31).include? may3.to_time # => True
(may1..may31).include? may3.to_datetime # => True
(may1..may31).include? noon_of_may3 # => False
```

Shouldn't the last case return `true` as well? 

Related Rails issue: https://github.com/rails/rails/issues/36175



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