Changelog for 1.20.0

[straight-shoota]

Preview: https://github.com/crystal-lang/crystal/blob/changelog/1.20.0/doc/changelogs/v1.20.md

[zw963]

(runtime) [deprecation] Soft deprecate Mutex in favor to Sync::Mutex (#16737, thanks @ysbaddaden)

Showing last frame. Use --error-trace for full trace.

In lib/splay_tree_map/src/splay_tree_map.cr:68:33

 68 | @lock = Mutex.new(protection: Mutex::Protection::Reentrant)
                                    ^---------------------------
Error: undefined constant Mutex::Protection::Reentrant

https://github.com/crystal-lang/crystal/pull/16737/changes#diff-7ee626e093ca9cff3a02c482c048f655b4247cff5fbe5aa77aa5ada42b6c7fd6L30-L34

Is this a breaking change?

[Sija]

Looks like the Mutex::Protection ended up as Sync::Type, see https://github.com/crystal-lang/crystal/blob/master/src/sync/type.cr

I'm not sure if that was an intentional change. /cc @ysbaddaden

[crysbot]

This pull request has been mentioned on Crystal Forum. There might be relevant details there:

https://forum.crystal-lang.org/t/upcoming-1-20-release/8842/1