Handling bounded wildcard types.

2 files changed, 26 insertions, 8 deletions

diff --git a/src/dotty/tools/dotc/core/TypeComparer.scala b/src/dotty/tools/dotc/core/TypeComparer.scala
index 479793326..ecd8ec0c4 100644
--- a/src/dotty/tools/dotc/core/TypeComparer.scala
+++ b/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -123,30 +123,40 @@ class TypeComparer(implicit val ctx: Context) extends DotClass {
           case _ =>
             secondTry(tp1, tp2)
         }
-      case WildcardType | ErrorType =>
-        true
-      case tp2: TypeVar =>
-        firstTry(tp1, tp2.thisInstance)
       case tp2: PolyParam =>
         constraint(tp2) match {
           case TypeBounds(lo, _) => isSubType(tp1, lo) || addConstraint(tp2, TypeBounds.lower(tp1))
           case _ => secondTry(tp1, tp2)
         }
+      case tp2: TypeVar =>
+        firstTry(tp1, tp2.thisInstance)
+      case tp2: WildcardType =>
+        tp2.optBounds match {
+          case TypeBounds(_, hi) => isSubType(tp1, hi)
+          case NoType => true
+        }
+      case ErrorType =>
+        true
       case _ =>
         secondTry(tp1, tp2)
     }
   }
 
   def secondTry(tp1: Type, tp2: Type): Boolean = tp1 match {
-    case WildcardType | ErrorType =>
-      true
-    case tp1: TypeVar =>
-      secondTry(tp1.thisInstance, tp2)
     case tp1: PolyParam =>
       constraint(tp1) match {
         case TypeBounds(_, hi) => isSubType(hi, tp2) || addConstraint(tp1, TypeBounds.upper(tp2))
         case _ => thirdTry(tp1, tp2)
       }
+    case tp1: TypeVar =>
+      secondTry(tp1.thisInstance, tp2)
+    case tp1: WildcardType =>
+      tp1.optBounds match {
+        case TypeBounds(lo, _) => isSubType(lo, tp2)
+        case _ => true
+      }
+    case ErrorType =>
+      true
     case _ =>
       thirdTry(tp1, tp2)
   }
diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index e66d86a40..f2b86242d 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -1796,6 +1796,8 @@ object Types {
 
   /** Wildcard type, possibly with bounds */
   abstract case class WildcardType(optBounds: Type) extends CachedGroundType {
+    def derivedWildcardType(optBounds: Type)(implicit ctx: Context) =
+      if (optBounds eq this.optBounds) this else WildcardType(optBounds.asInstanceOf[TypeBounds])
     override def computeHash = doHash(optBounds)
   }
 
@@ -1891,6 +1893,9 @@ object Types {
       case tp @ TypeVar(_) =>
         apply(tp.thisInstance)
 
+      case tp @ WildcardType =>
+        tp.derivedWildcardType(mapOver(tp.optBounds))
+
       case _ =>
         tp
     }
@@ -1989,6 +1994,9 @@ object Types {
       case tp: TypeVar =>
         foldOver(x, tp.thisInstance)
 
+      case tp: WildcardType =>
+        foldOver(x, tp.optBounds)
+
       case _ => x
     }
   }