Summary

Fixes #8458

When using ProjectMatrix with CrossVersion.full and Scala 2 versions like 2.13.18, the project ID incorrectly became $1$2_13_18 instead of foo2_13_18.

Root cause: The Scala 3 compiler creates synthetic intermediate vals (e.g., $1) during macro expansion. The enclosingTerm function in the macros was stopping at these synthetic symbols instead of continuing up the symbol tree to find the actual val name.

Fix: Added Flags.Synthetic check to skip compiler-generated symbols in:

• main-settings/src/main/scala/sbt/std/KeyMacro.scala
• lm-core/src/main/scala/sbt/librarymanagement/ConfigurationExtra.scala

Test

// build.sbt
val foo = projectMatrix
  .jvmPlatform(
    scalaVersions = Seq("2.13.18", "3.3.7"),
    crossVersion = CrossVersion.full
  )

Before: sbt projects shows $1$2_13_18, $1$3_3_7
After: sbt projects shows foo2_13_18, foo3_3_7

Contribution by Gittensor, see my contribution statistics at https://gittensor.io/miners/details?githubId=4217675