Merge pull request #2068 from dotty-staging/fix-#2064

Fix #2064: Avoid illegal types in OrDominator

1 files changed, 7 insertions, 8 deletions

diff --git a/compiler/src/dotty/tools/dotc/core/Types.scala b/compiler/src/dotty/tools/dotc/core/Types.scala
index 546473b68..b8f81f1bb 100644
--- a/compiler/src/dotty/tools/dotc/core/Types.scala
+++ b/compiler/src/dotty/tools/dotc/core/Types.scala
@@ -1274,10 +1274,14 @@ object Types {
     def underlying(implicit ctx: Context): Type
 
     /** The closest supertype of this type. This is the same as `underlying`,
-     *  except for TypeRefs where the upper bound is returned, and HKApplys,
-     *  where the upper bound of the constructor is re-applied to the arguments.
+     *  except that
+     *    - instead of a TyperBounds type it returns its upper bound, and
+     *    - for HKApplys it returns the upper bound of the constructor re-applied to the arguments.
      */
-    def superType(implicit ctx: Context): Type = underlying
+    def superType(implicit ctx: Context): Type = underlying match {
+      case TypeBounds(_, hi) => hi
+      case st => st
+    }
   }
 
   // Every type has to inherit one of the following four abstract type classes.,
@@ -1766,11 +1770,6 @@ object Types {
     type ThisType = TypeRef
 
     override def underlying(implicit ctx: Context): Type = info
-
-    override def superType(implicit ctx: Context): Type = info match {
-      case TypeBounds(_, hi) => hi
-      case _ => info
-    }
   }
 
   final class TermRefWithSignature(prefix: Type, name: TermName, override val sig: Signature) extends TermRef(prefix, name) {