[BUG] undefined constant Crystal::Scheduler - with Crystal v1.16.3 and -Dexecution_context

[crimson-knight]

Describe the bug
After adding the shard to my shard.yml file and installing the dependencies, when I try to compile I get this error:

In lib/nbchannel/src/nbchannel.cr:57:9

 57 | Crystal::Scheduler.reschedule
      ^-----------------
Error: undefined constant Crystal::Scheduler

Expected behavior
The shard to be added to the shard.yml file and the code should compile and run as usual with the instrumentation added in.

Versions(please complete the following information):

• OS: MacOS 14.7.6
• Crystal: 1.16.3 with -Dpreview_mt -Dexecution_context flags

[miry]

I believe this issue is caused by a conflict between the standard Crystal::Scheduler implementation and the custom one provided by execution_context.

The shard replaces the regular Crystal::Scheduler implementation in stdlib with new ones.

From the code, it looks like nbchannel.cr depends on the standard Crystal::Scheduler.

UPDATE: I found that execution context was merged to standard, but it is still experimental: https://crystal-lang.org/api/1.16.3/Fiber/ExecutionContext.html

[miry]

In my first impression the nbchannel.cr was a modified version of Channel. It means need to update the code to the latest https://github.com/crystal-lang/crystal/blob/3f369d2c721e9462d9f6126cb0bcd4c6992f0225/src/channel.cr#L144

If it just to replace Crystal::Scheduler.reschedule with Fiber.suspend, but need to check other cases.

I can look to this later this week.

Reference:

• crystal-lang/crystal@a23f0fb
• Add Fiber.suspend crystal-lang/crystal#14560
• https://github.com/crystal-lang/crystal/blob/3f369d2c721e9462d9f6126cb0bcd4c6992f0225/src/channel.cr#L144