[ruby-core:110422] [Ruby master Feature#19071] Add Time#deconstruct, #deconstruct_keys, and #to_h

["zverok (Victor Shepelev)" <noreply@ruby-lang.org>]

Issue #19071 has been reported by zverok (Victor Shepelev).

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Feature #19071: Add Time#deconstruct, #deconstruct_keys, and #to_h
https://bugs.ruby-lang.org/issues/19071

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
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I believe that `Time` being suitable for pattern-matching is a reasonable feature with many possible usages, which will increase usability of `Time` and would be a good show case for pattern matching.

**Implementation decisions**

`Time#deconstruct`: 
* returns time components in order `[year, month, mday, hour, min, sec, subsec]`
* I believe the highest-to-lowest order is the only reasonable/guessable, and there is no point to put into the array _all_ of the time information available (e.g. zone, wday, yday)
* I am not sure (and open to discussion) about `subsec`. It seems to me the most basic sub-second unit of Time, but I might be wrong; also, it might be not that useful for array deconstruction.

Possible usage:
```ruby
case tm
in [...2022, *]
  puts "previous year"
in [2022, 1..6, *]
  puts "Q1-2"
in [2022, 7..9, *]
  puts "Q3"
in [2022, month, day, *]
  puts "Current quarter, #{day}/#{month}"
end
```

`Time#deconstruct_keys`: 
* chosen keys: `[:year, :month, :day, :yday, :wday, :hour, :min, :sec, :subsec, :dst, :zone]` 
* I am open to discussing whether we should include other subsecond units (or any whatsoever)
* It might be useful (but too loose interface) to support `mon` as a synonym for `month`?.. But might be confusing if somebody will unpack the `**rest`
* `day`, not `mday`, seems most reasonable

Possible usages:
```ruby
case t
in year: ...2022
  puts "too old"
in month: ..9
  puts "quarter 1-3"
in wday: 1..5, month:
  puts "working day in month #{month}"
end

if t in Time(wday: 3, day: ..7)
  puts "first Wednesday of the month"
end
```

`Time#to_h`:
* added on a "why not" basis :) As we already have "convert to hash" in the form of `deconstruct_keys(nil)`, having a canonic form seems harmles. Open for discussion.
* keys are the same as for `deconstruct_keys`

Pull request: https://github.com/ruby/ruby/pull/6594



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