Avoid accidental creation of hk types

- Swap subtype tests

  Previous order could create constraints where hk type parameters
  got a * bound. (this is now caught in an assert).
- Make underlyingClassRef work for hk types under new scheme.
- Ensure that toAvoid does not creat hk from * types
- Let getClass return a * type

  We will be pickier than before. An unapplied type such as
  `java.lang.Class` will always be an hk type. Hence, the type
  of getClass has to be appleid to [_] to make it a * type.

1 files changed, 7 insertions, 4 deletions

diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index 2fa4f94c1..ab5c795e3 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -875,13 +875,16 @@ object Types {
         if (tp.symbol.isClass) tp
         else if (tp.symbol.isAliasType) tp.underlying.underlyingClassRef(refinementOK)
         else NoType
-      case tp: AnnotatedType => tp.underlying.underlyingClassRef(refinementOK)
+      case tp: AnnotatedType =>
+        tp.underlying.underlyingClassRef(refinementOK)
       case tp: RefinedType =>
         def isParamName = tp.classSymbol.typeParams.exists(_.name == tp.refinedName)
-        if (refinementOK || isParamName) tp.underlying.underlyingClassRef(refinementOK)
+        if (refinementOK || tp.isTypeParam || isParamName) tp.underlying.underlyingClassRef(refinementOK)
         else NoType
-      case tp: RecType if refinementOK => tp.parent
-      case _ => NoType
+      case tp: RecType =>
+        tp.underlying.underlyingClassRef(refinementOK)
+      case _ =>
+        NoType
     }
 
     /** The iterator of underlying types as long as type is a TypeProxy.