union, intersection and overlaps? for Ranges

[CTC97]

Apologies for the earlier PR from my forked master branch.

Based on the request from @jgaskins. Behaviors below:

a = 1..5
b = 3..7
a.union(b)        # => 1..7
a.intersection(b) # => 3..5

c = 1..10
d = 1...15
c.union(d)        # => 1...15
c.intersection(d) # => 1..10

e = 1...10
f = 1..15
e.union(f)        # => 1..15
e.intersection(f) # => 1...10

g = 1..5
h = 10..20
g.union(h)        # => 0..0
g.intersection(h) # => 0..0

(1...10).union(1..10)        # => 1..10
(1...10).intersection(1..10) # => 1...10

(1...10).union(10..20) # => 1..20

(1..5).union(5..10) # => 1..10

(1...10).intersection(7..12) # => 7...10
(2..10).intersection(0..8)   # => 2..8

(1...10).overlaps?(10..11)   # => false
(1..10).overlaps?(5..9) # => true

Fixes #14487
Fixes #14488

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P.S., very excited to be making a small contribution to a lovely language.

Looking forward to review!

[jgaskins]

This looks like a great start. A couple areas of focus:

• Ranges can be nil on either end
• It would be awesome to see some tests — this functionality can be super confusing and, honestly, I wouldn't be able to tell whether any implementation was correct when all edge cases are considered

[jgaskins]

I'm not sure we can get away with hardcoding a Range(Int32, Int32) specifically. My own use case for this functionality is actually Range(Time, Time), so I'd get compile-time errors with this return value.

[CTC97]

Good catch, and thank you for the quick review!

I'll get on these changes asap! ✌️⭐

[Blacksmoke16]

Some specs would be a good idea as well 👍.

[jgaskins]

Tests and specs? In this economy?