SI-4043 Share code in etaExpand and inferPolyAlternatives

Part II, remove the old implementation.

Author: retronym

src/compiler/scala/tools/nsc/typechecker/Infer.scala

@@ -1446,11 +1446,7 @@ trait Infer extends Checkable {
           log(s"Attaching AntiPolyType-carrying overloaded type to $sym")
           // Multiple alternatives which are within bounds; spin up an
           // overloaded type which carries an "AntiPolyType" as a prefix.
-          val tparams = newAsSeenFromMap(pre, hd.owner) mapOver hd.typeParams
-          val bounds  = tparams map (_.tpeHK) // see e.g., #1236
-          val tpe     = PolyType(tparams, OverloadedType(AntiPolyType(pre, bounds), alts))
-          val tpe1 = typeFunAnonSeenFrom(pre, hd, hd.typeParams, (bounds: List[Type]) => OverloadedType(AntiPolyType(pre, bounds), alts))
-          assert(tpe.matches(tpe1) && tpe1.matches(tpe1))
+          val tpe = typeFunAnonSeenFrom(pre, hd, hd.typeParams, (bounds: List[Type]) => OverloadedType(AntiPolyType(pre, bounds), alts))
           finish(sym setInfo tpe, tpe)
       }
       matchingLength.alternatives match {

src/reflect/scala/reflect/internal/Types.scala

@@ -2182,15 +2182,7 @@ trait Types
       val tpars = initializedTypeParams
       if (tpars.isEmpty) this
       else {
-        val map = newAsSeenFromMap(pre, sym.owner)
-        val tpars1 = map.mapOver(tpars)
-        val tp = if (tpars eq tpars1)
-          typeFunAnon(tpars, copyTypeRef(this, pre, sym, tpars map (_.tpeHK)))
-        else
-          typeFunAnon(tpars1, copyTypeRef(this, pre, sym, tpars map (_.tpeHK.substSym(tpars, tpars1))))
-        val tp1 = typeFunAnonSeenFrom(pre, sym, tpars, bounds => copyTypeRef(this, pre, sym, bounds))
-        assert(tp.matches(tp) && tp1.matches(tp1))
-        tp
+        typeFunAnonSeenFrom(pre, sym, tpars, bounds => copyTypeRef(this, pre, sym, bounds))
       } // todo: also beta-reduce?
     }