Simplify abstracted

As @smarter noted, makes no sense to use a boolean parameter here.
We got there by refactoring blindness.

Author: odersky

src/dotty/tools/dotc/typer/Namer.scala

@@ -934,11 +934,10 @@ class Namer { typer: Typer =>
   }
 
   def typeDefSig(tdef: TypeDef, sym: Symbol, tparamSyms: List[TypeSymbol])(implicit ctx: Context): Type = {
-    def abstracted(tp: Type, canAbstract: Boolean): Type =
-      if (tparamSyms.nonEmpty && canAbstract) tp.LambdaAbstract(tparamSyms)
-      else tp
+    def abstracted(tp: Type): Type =
+      if (tparamSyms.nonEmpty) tp.LambdaAbstract(tparamSyms) else tp
 
-    val dummyInfo = abstracted(TypeBounds.empty, canAbstract = true)
+    val dummyInfo = abstracted(TypeBounds.empty)
     sym.info = dummyInfo
       // Temporarily set info of defined type T to ` >: Nothing <: Any.
       // This is done to avoid cyclic reference errors for F-bounds.
@@ -952,7 +951,8 @@ class Namer { typer: Typer =>
       // inspects a TypeRef's info, instead of simply dealiasing alias types.
 
     val isDerived = tdef.rhs.isInstanceOf[untpd.DerivedTypeTree]
-    val rhsType = abstracted(typedAheadType(tdef.rhs).tpe, canAbstract = !isDerived)
+    val rhsBodyType = typedAheadType(tdef.rhs).tpe
+    val rhsType = if (isDerived) rhsBodyType else abstracted(rhsBodyType)
     val unsafeInfo = rhsType match {
       case bounds: TypeBounds => bounds
       case alias => TypeAlias(alias, if (sym is Local) sym.variance else 0)