get back scala 2.12 (#280)

.github/workflows/scala.yml

@@ -13,8 +13,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        # FIXME Use stable scala version
-        scala: [2.13.12, 3.3.0]
+        scala: [2.12.19, 2.13.12, 3.3.0]
 
     steps:
       - uses: actions/checkout@v3

.gitignore

@@ -7,6 +7,7 @@
 /test-output
 /project/target
 /project/project
+metals.sbt
 .cache
 .history
 .lib
@@ -25,5 +26,6 @@ gpg.sbt
 modules/**/target
 */jmh-result.json
 
+.vscode
 .metals
 .bloop

build.sbt

@@ -1,3 +1,4 @@
+lazy val scala212 = "2.12.19"
 lazy val scala213 = "2.13.12"
 /* FIXME
 Return to use a stable version when 'scala.quoted.Quotes.reflectModuleSymbol.newClass'
@@ -66,7 +67,7 @@ def crossScalaSettings = {
     }
 
   Seq(
-    crossScalaVersions := Seq(scala213, scala3),
+    crossScalaVersions := Seq(scala212, scala213, scala3),
     Compile / unmanagedSourceDirectories ++= addDirsByScalaVersion("src/main").value,
     Test / unmanagedSourceDirectories ++= addDirsByScalaVersion("src/test").value
   )
@@ -89,12 +90,10 @@ lazy val tethys = project.in(file("."))
 
 lazy val modules = file("modules")
 
-def addScalaCompiler(scalaVersion: String): Seq[ModuleID] =
+def addScalaReflect(scalaVersion: String): Seq[ModuleID] =
   CrossVersion.partialVersion(scalaVersion) match {
-    case Some((2, y)) if y >= 13 =>
-      Seq("org.scala-lang" % "scala-compiler" % scalaVersion % Provided)
-    case Some((3, _)) =>
-      Seq("org.scala-lang" %% "scala3-compiler" % scalaVersion % Provided)
+    case Some((2, y)) =>
+      Seq("org.scala-lang" % "scala-reflect" % scalaVersion)
     case _ => Seq.empty
   }
 
@@ -104,7 +103,7 @@ lazy val core = project.in(modules / "core")
   .settings(testSettings)
   .settings(
     name := "tethys-core",
-    libraryDependencies ++= addScalaCompiler(scalaVersion.value)
+    libraryDependencies ++= addScalaReflect(scalaVersion.value)
   )
 
 lazy val `macro-derivation` = project.in(modules / "macro-derivation")
@@ -113,7 +112,7 @@ lazy val `macro-derivation` = project.in(modules / "macro-derivation")
   .settings(testSettings)
   .settings(
     name := "tethys-derivation",
-    libraryDependencies ++= addScalaCompiler(scalaVersion.value)
+    libraryDependencies ++= addScalaReflect(scalaVersion.value)
   )
   .dependsOn(core)
 
@@ -190,13 +189,12 @@ lazy val enumeratum = project.in(modules / "enumeratum")
   .settings(crossScalaSettings)
   .settings(commonSettings)
   .settings(testSettings)
-  .settings(crossScalaVersions := Seq(scala213))
   .settings(
     name := "tethys-enumeratum",
     libraryDependencies ++= {
       CrossVersion.partialVersion(scalaVersion.value) match {
-        case Some((2, y)) if y >= 13 =>
-          Seq("com.beachape" %% "enumeratum" % "1.7.2")
+        case Some((2, y)) =>
+          Seq("com.beachape" %% "enumeratum" % "1.7.3")
         case _ => Seq.empty
       }
     }

modules/core/src/main/scala-2.12/tethys/compat/CollectionBuilder.scala

@@ -0,0 +1,20 @@
+package tethys.compat
+
+import scala.collection.generic.CanBuildFrom
+import scala.collection.mutable
+import scala.language.higherKinds
+
+trait CollectionBuilder[A, C] {
+  def newBuilder: mutable.Builder[A, C]
+}
+
+object CollectionBuilder {
+  implicit def seqCBFBuilder[A, C[_]](implicit cbf: CanBuildFrom[Nothing, A, C[A]]): CollectionBuilder[A, C[A]] = new CollectionBuilder[A, C[A]] {
+    override def newBuilder: mutable.Builder[A, C[A]] = cbf()
+  }
+
+  implicit def mapCBFBuilder[K, V, M[_, _]](implicit cbf: CanBuildFrom[Nothing, (K, V), M[K, V]]): CollectionBuilder[(K, V), M[K, V]] =
+    new CollectionBuilder[(K, V), M[K, V]] {
+      override def newBuilder: mutable.Builder[(K, V), M[K, V]] = cbf()
+    }
+}