Fix condition for lambda abstracting in Namer

The previous condition could make a (derived) type a * type
for a little while even though it had type parameters. This
loophole caused collection/generic/MapFactory.scala and with
it compile-stdlib to fail.
Refinement for knownHK for PolyParams

pos test t2082.scala shows that knownHK can be constructed before
the binder PolyType of a PolyParam is initialized.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index 986a9c292..d3e97b492 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -2765,7 +2765,11 @@ object Types {
 
     def paramName = binder.paramNames(paramNum)
 
-    override def underlying(implicit ctx: Context): Type = binder.paramBounds(paramNum)
+    override def underlying(implicit ctx: Context): Type = {
+      val bounds = binder.paramBounds
+      if (bounds == null) NoType // this can happen if the PolyType is not initialized yet
+      else bounds(paramNum)
+    }
     // no customized hashCode/equals needed because cycle is broken in PolyType
     override def toString = s"PolyParam($paramName)"