Scala compiler updates

build.sbt

@@ -104,7 +104,7 @@ val settings = Seq(
       "-Wconf:msg=discarding unmoored doc comment:s", // silence errors when scaladoc cannot comprehend nested vals
       "-Wconf:msg=Could not find any member to link for:s", // since errors when scaladoc cannot link to stdlib types or nested types
       "-Wconf:msg=Variable .+ undefined in comment for:s", // silence errors when there we're showing a buggy Expr in scaladoc comment
-      "-Wconf:msg=a type was inferred to be kind-polymorphic `Nothing` to conform to:s", // silence warn that appeared after updating to Scala 2.13.18
+      "-Wconf:msg=a type was inferred to be kind-polymorphic `Nothing` to conform to:s", // silence warn that appeared after updating to Scala 3.9.0
       "-Wunused:patvars",
       "-Xfatal-warnings",
       "-Xlint:adapted-args",

project/BuildVersions.scala

@@ -9,7 +9,7 @@ import sbt.librarymanagement.CrossVersion
 
 object versions {
   // Versions we are publishing for.
-  val scala213 = "2.13.18"
+  val scala213 = "3.9.0"
   val scala3 = "3.9.0"
   // For chimney-sandwich-test-cases-3 ONLY: sbt forbids Scala 2.13 subprojects from depending on Scala 3.8+
   // subprojects (sbt-8728), and 2.13's -Ytasty-reader tops out below TASTy 28.8 - see the module for details.

scripts/test-snippets.scala

@@ -45,7 +45,7 @@ class ChimneyExtendedRunner(runner: Runner)(
     mkDocsCfg: MkDocsConfig
 ) extends Runner {
 
-  private val defaultScalaVersion = "2.13.18"
+  private val defaultScalaVersion = "3.9.0"
 
   private val replacePatterns = (mkDocsCfg.extra + (raw"chimney_version\(\)" -> chimneyVersion)).map { case (k, v) =>
     (raw"\{\{\s*" + k + raw"\s*\}\}") -> v