I found that it's exactly this commit (`3418e7aa4762d93be38d9ae0414a3f31a68ae9aa`) which first causes the crash.

I will investigate.

Looking at the stack trace, and seeing the commit, I really think the crash is caused by a too complex extension:

extension NonEmptyProtocol
 where Collection: NonEmptyProtocol,
 Collection.Collection: NonEmptyProtocol,
 Collection.Collection.Collection: NonEmptyProtocol,
 Collection.Collection.Collection.Collection: NonEmptyProtocol,
 Collection.Collection.Collection.Collection.Collection: NonEmptyProtocol,
 Collection.Collection.Collection.Collection.Collection.Collection: NonEmptyProtocol,
 Collection.Collection.Collection.Collection.Collection.Collection.Collection: NonEmptyProtocol,
 Collection.Collection.Collection.Collection.Collection.Collection.Collection.Collection: NonEmptyProtocol,
 Collection.Collection.Collection.Collection.Collection.Collection.Collection.Collection.Collection: NonEmptyProtocol
 {

It's exactly the {code:swift}.tenth

I couldn't find a compiler flag to increase the RAM used by the compiler (I don't even know if it would have helped), so I simply removed the too complex extensions.

However, the issue is still there.

Comment by Dzmitry Antonenka (JIRA)

Hello @RemiBardon, seems I faced same issue related to Realm dependency with swift 5.6. I'm attaching log swift_5.6_issue copy.rtf, hope it will help with investigation

You need to increase the maximum rewrite system term length with a compiler flag, like so: -Xfrontend -requirement-machine-depth-limit=20

I can tweak the heuristic to avoid this problem.

dzmitry.antonenka (JIRA User) the issue with RealmSwift is not related to this. You need to update to the latest RealmSwift sources to get the fix.

This fixes the generic signature without passing a flag: #42017

#42017