Remove deprecated ? syntax

Scala 2.13.6 and 2.12.14 will interpret `?` as a wildcard when using the
`-Xsource:3` flag (cf scala/scala#9560)). This
means that the old kind-projector syntax will no longer work, so it
seems like a good time to remove it. This will also allow us to compile
more of the community-build with `-Xsource:3` enabled (cf
scala/scala-dev#769).

Sincet this is a breaking change, we also bump the version to
0.12.0-SNAPSHOT.

README.md

@@ -48,7 +48,6 @@ avoid defining the following identifiers:
 
  1. `Lambda` and `λ`
  2. `*`, `+*`, and `-*`
- 3. `?`, `+?`, and `-?` ([deprecated syntax](https://github.com/typelevel/kind-projector/issues/108); same meaning as the above)
  4. `Λ$`
  5. `α$`, `β$`, ...
 

src/main/scala/KindProjector.scala

@@ -51,34 +51,19 @@ class KindRewriter(plugin: Plugin, val global: Global)
     // Reserve some names
     val TypeLambda1 = newTypeName("Lambda")
     val TypeLambda2 = newTypeName("λ")
-    object InvPlaceholder  {
-      def unapply(name: TypeName): Boolean = name == newTypeName("$qmark") || name == newTypeName("$times")
-    }
-    object CoPlaceholder {
-      def unapply(name: TypeName): Boolean = name == newTypeName("$plus$qmark") || name == newTypeName("$plus$times")
-    }
-    object ContraPlaceholder {
-      def unapply(name: TypeName): Boolean = name == newTypeName("$minus$qmark") || name == newTypeName("$minus$times")
-    }
+    val InvPlaceholder = newTypeName("$times")
+    val CoPlaceholder = newTypeName("$plus$times")
+    val ContraPlaceholder = newTypeName("$minus$times")
 
-    def deprecationFor(name: TypeName): Option[(String, String)] =
-      if (name == newTypeName("$qmark")) Some("?" -> "*")
-      else if (name == newTypeName("$plus$qmark")) Some("+?" -> "+*")
-      else if (name == newTypeName("$minus$qmark")) Some("-?" -> "-*")
-      else None
-
     val TermLambda1 = TypeLambda1.toTermName
     val TermLambda2 = TypeLambda2.toTermName
 
-    class Placeholder(deprecationReporter: (String, String) => Unit) {
-      def unapply(name: TypeName): Option[Variance] = {
-        for ((used, preferred) <- deprecationFor(name)) deprecationReporter(used, preferred)
-        name match {
-          case InvPlaceholder() => Some(Invariant)
-          case CoPlaceholder() => Some(Covariant)
-          case ContraPlaceholder() => Some(Contravariant)
-          case _ => None
-        }
+    object Placeholder {
+      def unapply(name: TypeName): Option[Variance] = name match {
+        case InvPlaceholder => Some(Invariant)
+        case CoPlaceholder => Some(Covariant)
+        case ContraPlaceholder => Some(Contravariant)
+        case _ => None
       }
     }
 
@@ -255,17 +240,12 @@ class KindRewriter(plugin: Plugin, val global: Global)
       def handlePlaceholders(t: Tree, as: List[Tree]) = {
         // create a new type argument list, catching placeholders and create
         // individual identifiers for them.
-        val placeholder = new Placeholder((deprecatedName, preferredName) => {
-          val msg = "kind-projector ? placeholders are deprecated." +
-                   s" Use $preferredName instead of $deprecatedName for cross-compatibility with Scala 3"
-          global.runReporting.warning(t.pos, msg, Reporting.WarningCategory.Deprecation, t.symbol)
-        })
         val xyz = as.zipWithIndex.map {
-          case (id @ Ident(placeholder(variance)), i) =>
+          case (Ident(Placeholder(variance)), i) =>
             (Ident(newParamName(i)), Some(Right(variance)))
-          case (apl @ AppliedTypeTree(Ident(placeholder(variance)), ps), i) =>
+          case (AppliedTypeTree(Ident(Placeholder(variance)), ps), i) =>
             (Ident(newParamName(i)), Some(Left((variance, ps.map(makeComplexTypeParam)))))
-          case (xst @ ExistentialTypeTree(AppliedTypeTree(Ident(placeholder(variance)), ps), _), i) =>
+          case (ExistentialTypeTree(AppliedTypeTree(Ident(Placeholder(variance)), ps), _), i) =>
             (Ident(newParamName(i)), Some(Left((variance, ps.map(makeComplexTypeParam)))))
           case (a, i) =>
             (super.transform(a), None)

src/test/scala/test.scala

@@ -14,8 +14,8 @@ object Test {
   baz[({type L[X,Y] = Tuple3[Int, X, Y]})#L]
 
   // used to test the plugin
-  bar[Either[Int, ?]]
-  baz[Tuple3[Int, ?, ?]]
+  bar[Either[Int, *]]
+  baz[Tuple3[Int, *, *]]
   baz[Tuple3[*, Int, *]]
 
   // should not be changed by the plugin
@@ -41,8 +41,7 @@ object Test {
 
   trait Functor[F[_]]
   trait EitherT[F[_], A, B]
-  qux[Functor[?[_]]]
-  qux[EitherT[?[_], Int, Double]]
+  qux[Functor[*[_]]]
   qux[EitherT[*[_], Int, Double]]
 
   // higher higher order
@@ -54,7 +53,7 @@ object Test {
   vex[Lambda[A[B[C]] => Unit]]
 
   trait FunctorK[F[_[_]]]
-  vex[FunctorK[?[_[_]]]]
+  vex[FunctorK[*[_[_]]]]
 
   def hex[T[_[_[_[_]]]]] = ()
   hex[({type L[A[_[_[_]]]] = Unit})#L]
@@ -63,14 +62,13 @@ object Test {
   // covariant
   def mux[T[+_]] = ()
   mux[({type L[+A] = Either[A, Int]})#L]
-  mux[Either[+?, Int]]
+  mux[Either[+*, Int]]
   mux[Lambda[`+A` => Either[A, Int]]]
   mux[Lambda[+[A] => Either[A, Int]]]
 
   // contravariant
   def bux[T[-_, +_]] = ()
   bux[({type L[-A, +B] = Function2[A, Int, B]})#L]
-  bux[Function2[-?, Int, +?]]
   bux[Function2[-*, Int, +*]]
   bux[Lambda[(`-A`, `+B`) => Function2[A, Int, B]]]
   bux[Lambda[(-[A], +[B]) => Function2[A, Int, B]]]
@@ -79,9 +77,7 @@ object Test {
   trait ~>[-F[_], +G[_]]
   def tux[T[-F[_]]] = ()
   def hux[T[+G[_]]] = ()
-  tux[~>[-?[_], Option]]
   tux[~>[-*[_], Option]]
-  hux[~>[Option, +?[_]]]
   hux[~>[Option, +*[_]]]
   tux[Lambda[`-F[_]` => ~>[F, Option]]]
   hux[Lambda[`+G[_]` => ~>[Option, G]]]

version.sbt

@@ -1 +1 @@
-version in ThisBuild := "0.11.4-SNAPSHOT"
+version in ThisBuild := "0.12.0-SNAPSHOT"