Move scala2Mode test from isStable to isRealizable

This prepares the way for using isRealizable in different contexts.

Author: odersky

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

@@ -522,9 +522,7 @@ object SymDenotations {
     final def isStable(implicit ctx: Context) = {
       val isUnstable =
         (this is UnstableValue) ||
-          is(Lazy, butNot = Module) &&
-          !(info.isRealizable || ctx.scala2Mode) &&
-          !hasAnnotation(defn.UncheckedStableAnnot)
+          is(Lazy, butNot = Module) && !info.isRealizable && !hasAnnotation(defn.UncheckedStableAnnot)
       (this is Stable) || isType || {
         if (isUnstable) false
         else { setFlag(Stable); true }

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

@@ -138,10 +138,12 @@ object Types {
           case tp: AndOrType => isConcrete(tp.tp1) && isConcrete(tp.tp2)
           case _ => false
         }
-        isConcrete(tp) && tp.abstractTypeMembers.forall { m =>
+        isConcrete(tp) &&
+        tp.abstractTypeMembers.forall { m =>
           val bounds = m.info.bounds
           bounds.lo <:< bounds.hi
-        }
+        } ||
+        ctx.scala2Mode
     }
 
     /** Does this type refer exactly to class symbol `sym`, instead of to a subclass of `sym`?