swift

d0a49add - [region-isolation] Make "unknown pattern error" always an error.

[region-isolation] Make "unknown pattern error" always an error. This shows an actual issue with the compiler where semantically we should crash. Rather than crashing (due to the broken invariants), we emit this error so that the user gets a nice error message at the problem place and can work around it instead of just getting a mysterious crash. Previously, we were making this a warning in swift 5 mode... but given the issues, it makes sense to emit an error diagnostic so we get the feedback and the user cannot ship the code. rdar://131482934 (cherry picked from commit b63781f7ba7796a8ad20b79c56f1ad961eac6286)