Added support for eliminating type parameters from TypeDefs.

(1) New scheme for higher-kinded types that deals also with F-bounds.
(2) Type parameters in type aliases are eliminated in most cases by expressing
     as unparameterized aliases of some refinement type. We will issue an error where
     this is not possible.

1 files changed, 11 insertions, 1 deletions

diff --git a/src/dotty/tools/dotc/typer/Namer.scala b/src/dotty/tools/dotc/typer/Namer.scala
index 7308d3aa6..18a26e0cf 100644
--- a/src/dotty/tools/dotc/typer/Namer.scala
+++ b/src/dotty/tools/dotc/typer/Namer.scala
@@ -284,7 +284,17 @@ class Namer { typer: Typer =>
 
   def typeDefSig(tdef: TypeDef, sym: Symbol)(implicit ctx: Context): Type = {
     completeParams(tdef.tparams)
-    ???
+    val tparamSyms = tdef.tparams map symbolOfTree
+    val rhsType = typedAhead(tdef.rhs, Mode.Type).tpe
+
+    rhsType match {
+      case bounds: TypeBounds =>
+        if (tparamSyms.nonEmpty) bounds.higherKinded(tparamSyms)
+        else rhsType
+      case _ =>
+        if (tparamSyms.nonEmpty) rhsType.LambdaAbstract(tparamSyms)(ctx.error(_, _))
+        else TypeBounds(rhsType, rhsType)
+    }
   }
 
   /** The type signature of a ClassDef with given symbol */