Address review comments of #693

Author: DarkDimius

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

@@ -504,7 +504,7 @@ object Symbols {
     def showName(implicit ctx: Context): String = ctx.nameString(this)
     def showFullName(implicit ctx: Context): String = ctx.fullNameString(this)
 
-    override def hashCode(): PhaseId = id
+    override def hashCode() = id
   }
 
   type TermSymbol = Symbol { type ThisName = TermName }

src/dotty/tools/dotc/transform/FunctionalInterfaces.scala

@@ -64,7 +64,7 @@ class FunctionalInterfaces extends MiniPhaseTransform {
 
         if (shouldSpecialize(m)) {
           val functionSymbol = tree.tpe.widenDealias.classSymbol
-          val names = ctx.atPhase(ctx.erasurePhase.prev) {
+          val names = ctx.atPhase(ctx.erasurePhase) {
             implicit ctx => functionSymbol.typeParams.map(_.name)
           }
           val interfaceName = (functionName ++ m.paramTypes.length.toString).specializedFor(m.paramTypes ::: m.resultType :: Nil, names, Nil, Nil)