Use a new prefixDirect in checkKindBounds0

[joroKr21]

Analogous to typeSymbolDirect, we add prefixDirect, because prefix normalizes type aliases. But kind-checking should not normalize type aliases. This was the intention as noted by comments and typeSymbolDirect.

Fixes scala/bug#9337
Closes scala/bug#10186, closes scala/bug#9625 with regression tests (fixed by #9193)

[joroKr21]

/rebuild

[joroKr21]

/rebuild

[SethTisue]

This change seems quite logical to me, but just in case, I'd like to do a community build run: https://scala-ci.typesafe.com/job/scala-2.13.x-jdk11-integrate-community-build/2319/

[dwijnand]

Clean. LGTM.

[joroKr21]

Looks like the two projects that failed in the community build don't work on java 11:

• kamon: missing a dependency on javax.annotation
• shapeless-java-records: requires the latest and greatest from Java (records and sealed classes)

[som-snytt]

What are the parameters for scala 2 changes? "Someone who was unhappy is now happy. No one who was happy is now unhappy." Is it possible to justify any migration pain on Scala 2?

[joroKr21]

I guess "fixed in dotty" is always a good thing to strive for

[dwijnand]

I assume your question is general, not to be taken as you not being in favour of this or such changes.

Re-fixing issues fixed in Scala 3 ("backporting") as well as fast-tracking other changes present in 3, provided they're not too disruptive, are acceptable.

[SethTisue]

@joroKr21 I'm looking through all of the 2.13.5 merged PRs and trying to decide which ones should be explicitly mentioned in the 2.13.5 release notes. in your opinion, do any of your PRs (such as this one) merit calling out individually?

and/or, it's possible is to give them a collective bullet: assorted fixes to typechecking (#123, #456, #789), that kind of thing; I could include a text like that if you provide one

[joroKr21]

As far as I can remember most of my fixes for 2.13.5 targeted higher-kinded types but I will go through my merged PRs tomorrow. I'm confident they can be summarised in one entry though.

[joroKr21]

@SethTisue something like this: "Assorted fixes to typechecking higher-kinded types (that bring the status quo closer to Scala 3): #9400, #9404, #9405, #9414, #9417, #9439." I'm not sure if mentioning Scala 3 makes sense, but what I mean is that those bugs are already fixed in dotty.

[SethTisue]

I'll use that, thanks!