Fix use of accessibleFrom when finding default arg getters

Author: dwijnand

compiler/src/dotty/tools/dotc/typer/Applications.scala

@@ -272,7 +272,7 @@ object Applications {
     else
       def selectGetter(qual: Tree): Tree =
         val getterDenot = qual.tpe.member(getterName)
-          .accessibleFrom(qual.tpe.widenIfUnstable) // to reset Local
+          .accessibleFrom(qual.tpe.widenIfUnstable, superAccess = true) // to reset Local
         if (getterDenot.exists) qual.select(TermRef(qual.tpe, getterName, getterDenot))
         else EmptyTree
       if !meth.isClassConstructor then

tests/pos/i16814.scala

@@ -0,0 +1,2 @@
+class Foo protected (foo: Int = 0) { }
+class Bar extends Foo