To tweaks to derivedRefinedType for higher-kinded types.

1. The calculation of type parameters was wrong, and is fixed now.

2. The kind of bounds might need to be adjusted in the derived types.

Example: Assume

type CC[+T]
class C[T]

If we start with the HK-type CC[A] this is encoded as covariant: CC { type _$hk0 += A }. But once we substitute C for CC, the refined info bounds need to become non-variant. It used to be C {  type T += A }; now it's been corrected to be C { type T = A }.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/dotty/tools/dotc/typer/Typer.scala b/src/dotty/tools/dotc/typer/Typer.scala
index 244713496..d607d547b 100644
--- a/src/dotty/tools/dotc/typer/Typer.scala
+++ b/src/dotty/tools/dotc/typer/Typer.scala
@@ -1054,8 +1054,8 @@ class Typer extends Namer with Applications with Implicits {
         if (tree.tpe <:< pt) tree
         else if (ctx.mode is Mode.Pattern) tree // no subtype check for pattern
         else {
-          //println(s"adapt to subtype ${tree.tpe} !<:< $pt") // !!!DEBUG
-          //println(TypeComparer.explained(implicit ctx => tree.tpe <:< pt))
+          println(s"adapt to subtype ${tree.tpe} !<:< $pt") // !!!DEBUG
+          println(TypeComparer.explained(implicit ctx => tree.tpe <:< pt)) // !!!DEBUG
           adaptToSubType(wtp)
         }
     }