-release 8 causes java.time.Instant to have a fictitious constructor

[Jasper-M]

Reproduction steps

scalaVersion := "2.13.8"

scalacOptions ++= List("-release", "8")

Welcome to Scala 2.13.8 (OpenJDK 64-Bit Server VM, Java 11.0.14).
Type in expressions for evaluation. Or try :help.

scala> new java.time.Instant
java.lang.NoSuchMethodError: java.time.Instant: method 'void <init>()' not found
  ... 35 elided

Problem

java.time.Instant doesn't have a default constructor but the compiler seems to think that it does.

[som-snytt]

This is for any earlier release, using ct.sym. (8 is sometimes a special version number. "Lucky 8".)

[som-snytt]

The condition for adding a ctor in ClassFileParser needs a couple of tweaks.

[som-snytt]

For some reason, there is no label for JDK 8.

[Jasper-M]

Are backports to 2.12 for stuff like this still accepted or are they frowned upon?

[som-snytt]

@Jasper-M I think they just throw you "side eye".

[SethTisue]

thanks @Jasper-M for the great catch and bug report, and thanks @som-snytt for the fix 🚀

[smarter]

Same bug in Scala 3: scala/scala3#15144