Build: Drop Scala 2.12 support

This was proposed more than a year ago, and nobody objected.
See #132

project/Versions.scala

@@ -1,14 +1,12 @@
 object Versions {
 
-  val Scala_2_12 = "2.12.17"
-
   val Scala_2_13 = "2.13.12"
 
   val Scala_3 = "3.3.1"
 
   // -- Dependencies --
 
-  val Airstream = "17.0.0-M6"
+  val Airstream = "17.0.0-M3-SNAPSHOT"
 
   val Ew = "0.2.0"
 

src/main/scala/com/raquo/laminar/receivers/ChildrenReceiver.scala

@@ -47,8 +47,7 @@ object ChildrenReceiver {
 
     /** Example usage: children(node1, node2) <-- signalOfBoolean */
     def apply(nodes: ChildNode.Base*): LockedChildrenReceiver = {
-      // #TODO[Scala 2.12] - toList is only needed because in Scala 2.12 varargs are (non-immutable) Seq
-      new LockedChildrenReceiver(nodes.toList)
+      new LockedChildrenReceiver(nodes)
     }
 
     /** Example usage: children(component1, component2) <-- signalOfBoolean */
@@ -57,8 +56,7 @@ object ChildrenReceiver {
     )(
       implicit renderable: RenderableNode[Component]
     ): LockedChildrenReceiver = {
-      // #TODO[Scala 2.12] - toList is only needed because in Scala 2.12 varargs are (non-immutable) Seq
-      new LockedChildrenReceiver(renderable.asNodeSeq(components.toList))
+      new LockedChildrenReceiver(renderable.asNodeSeq(components))
     }
   }
 }

src/test/scala/com/raquo/laminar/SyntaxSpec.scala

@@ -216,7 +216,7 @@ class SyntaxSpec extends UnitSpec {
     ))
 
     el.amend(
-      onMountUnmountCallback[Div]( // @Note "Div" type param is required only in scala 2.12
+      onMountUnmountCallback(
         mount = c => {
           val proof: MountContext[Div] = c
           ()
@@ -264,7 +264,7 @@ class SyntaxSpec extends UnitSpec {
     )
 
     el.amend(
-      onMountInsert[Div](_ => div()) // @Note "Div" type param is required only in scala 2.12
+      onMountInsert(_ => div())
     )
 
     el.amend(
@@ -279,17 +279,17 @@ class SyntaxSpec extends UnitSpec {
     )
 
     el.amend(
-      onMountBind(_ => observable --> ((num: Int) => noop(num * 5))),
-      onMountBind(_ => signal --> ((num: Int) => noop(num * 5))),
-      onMountBind(_ => stream --> ((num: Int) => noop(num * 5)))
+      onMountBind(_ => observable --> ((num: Int) => num * 5)),
+      onMountBind(_ => signal --> ((num: Int) => num * 5)),
+      onMountBind(_ => stream --> ((num: Int) => num * 5))
     )
 
     el.amend(
-      onMountBind[Div](_.thisNode.events(onClick).map(_ => 1) --> (num => noop(num * 5))) // @Note "Div" type param is required only in scala 2.12
+      onMountBind(_.thisNode.events(onClick).map(_ => 1) --> (num => num * 5))
     )
 
     el.amend(
-      onMountBind[Div](_ => stream --> bus.writer) // @Note "Div" type param is required only in scala 2.12
+      onMountBind(_ => stream --> bus.writer)
     )
 
     mount(el)

website/blog/2023-12-04-laminar-v17.0.0.md

@@ -210,6 +210,8 @@ See [Airstream#115](https://github.com/raquo/Airstream/issues/115) and [Laminar#
 
 **Migration** should be obvious where not specified.
 
+* Drop support for Scala 2.12
+  * [The RFC](https://github.com/raquo/Laminar/issues/132) has been up for more than a year, and nobody has spoken in favor of keeping support.
 * Internal structure refactor:
   * Rename `trait Airstream` -> `AirstreamAliases`
   * Move `trait Implicits` to api package