Fix of Fix of t1236: higher-kinded

Fix of d6df293. It turned out the original commit
was faulty in that iterator.flatten did not typecheck. The problem is fixed in this
commit and flatten is added to the collections test.

Author: odersky

src/dotty/tools/dotc/core/TypeComparer.scala

@@ -649,13 +649,13 @@ class TypeComparer(initctx: Context) extends DotClass {
         val base = tp1.narrow
         tparams.map(base.memberInfo)
       }
-    val hkArgs = tp2.argInfos
-    hk.println(s"isSubTypeHK: args1 = $args1, hkargs = $hkArgs")
-    val boundsOK = (args1 corresponds hkArgs)(isSubType)
+    val hkBounds = tp2.argInfos.map(_.asInstanceOf[TypeBounds])
+    val boundsOK = (hkBounds corresponds args1)(_ contains _)
     val variancesOK =
       argInfos1.nonEmpty || (tparams corresponds tp2.typeSymbol.name.hkVariances) { (tparam, v) =>
         v == 0 || tparam.variance == v
       }
+    hk.println(s"isSubTypeHK: args1 = $args1, hk-bounds = $hkBounds $boundsOK $variancesOK")
     boundsOK && variancesOK
   }
 

src/dotty/tools/dotc/core/Types.scala

@@ -1926,7 +1926,10 @@ object Types {
       if (lo eq tp) this
       else TypeAlias(tp, variance)
 
-    def contains(tp: Type)(implicit ctx: Context) = lo <:< tp && tp <:< hi
+    def contains(tp: Type)(implicit ctx: Context) = tp match {
+      case tp: TypeBounds => lo <:< tp.lo && tp.hi <:< hi
+      case _ => lo <:< tp && tp <:< hi
+    }
 
     def & (that: TypeBounds)(implicit ctx: Context): TypeBounds = {
       val v = this commonVariance that

tests/pos/collections.scala

@@ -1,10 +1,10 @@
 import scala.collection.generic.CanBuildFrom
 
 object collections {
-  
+
   val arr = Array("a", "b")
   val aa = arr ++ arr
- 
+
   List(1, 2, 3) map (x => 2)
 
   val s = Set(1, 2, 3)
@@ -18,16 +18,19 @@ object collections {
   val ints3: List[Int] = ints2
   val f = (x: Int) => x + 1
   val ints4: List[Int] = List(1, 2, 3, 5)
-    
+
   val ys = ints3 map (x => x + 1)
   val zs = ys filter (y => y != 0)
-  
+
   val chrs = "abc"
-    
+
   def do2(x: Int, y: Char) = ()
-  
+
   chrs foreach println
-  
+
   (ints2, chrs).zipped foreach do2
 
-}
+  val xs = List(List(1), List(2), List(3)).iterator
+  println(xs.flatten)
+
+}