Tighten checkBounds

Also disallow unapplied classes if bounds are first-kinded.
This broke the Child annotation which should really be kind
polymorphic. Fixed for now by making a special exception for Child.

Author: odersky

compiler/src/dotty/tools/dotc/transform/PostTyper.scala

@@ -213,7 +213,10 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
           }
         case tree: TypeApply =>
           val tree1 @ TypeApply(fn, args) = normalizeTypeArgs(tree)
-          Checking.checkBounds(args, fn.tpe.widen.asInstanceOf[PolyType])
+          if (fn.symbol != defn.ChildAnnot.primaryConstructor) {
+            // Make an exception for ChildAnnot, which should really have AnyKind bounds
+            Checking.checkBounds(args, fn.tpe.widen.asInstanceOf[PolyType])
+          }
           fn match {
             case sel: Select =>
               val args1 = transform(args)

compiler/src/dotty/tools/dotc/typer/Checking.scala

@@ -46,9 +46,14 @@ object Checking {
    */
   def checkBounds(args: List[tpd.Tree], boundss: List[TypeBounds], instantiate: (Type, List[Type]) => Type)(implicit ctx: Context): Unit = {
     (args, boundss).zipped.foreach { (arg, bound) =>
-      if (!bound.isLambdaSub && arg.tpe.isLambdaSub)
+      if (!bound.isLambdaSub && arg.tpe.hasHigherKind) {
         // see MissingTypeParameterFor
+        if (!arg.tpe.isLambdaSub) { // FIXME: Provisional, remove
+          println(i"different for checkBounds $arg vs $bound at ${ctx.phase} in ${ctx.owner.ownersIterator.toList}")
+          throw new AssertionError("")
+        }
         ctx.error(ex"missing type parameter(s) for $arg", arg.pos)
+      }
     }
     for ((arg, which, bound) <- ctx.boundsViolations(args, boundss, instantiate))
       ctx.error(

library/src/scala/annotation/internal/Child.scala

@@ -12,5 +12,6 @@ import scala.annotation.Annotation
  *  Then the class symbol `A` would carry the annotations
  *  `@Child[Bref] @Child[Cref]` where `Bref`, `Cref` are TypeRefs
  *  referring to the class symbols of `B` and `C`
+ *  TODO: This should be `Child[T <: AnyKind]`
  */
 class Child[T] extends Annotation