Eliminate ABSOVERRIDE from TASTY

Replace by ABSTRACT and OVERRIDE. No need to expose the representation detail
that they are a single flag.

Author: odersky

src/dotty/tools/dotc/core/tasty/TastyFormat.scala

@@ -157,7 +157,6 @@ Standard-Section: "ASTs" TopLevelStat*
                   LAZY
                   OVERRIDE
                   INLINE                // macro
-                  ABSOVERRIDE                     // abstract override
                   STATIC                            // mapped to static Java member
                   OBJECT                            // an object or its class
                   TRAIT                 // a trait
@@ -238,22 +237,21 @@ object TastyFormat {
   final val LAZY = 14
   final val OVERRIDE = 15
   final val INLINE = 16
-  final val ABSOVERRIDE = 17
-  final val STATIC = 18
-  final val OBJECT = 19
-  final val TRAIT = 20
-  final val LOCAL = 21
-  final val SYNTHETIC = 22
-  final val ARTIFACT = 23
-  final val MUTABLE = 24
-  final val LABEL = 25
-  final val FIELDaccessor = 26
-  final val CASEaccessor = 27
-  final val COVARIANT = 28
-  final val CONTRAVARIANT = 29
-  final val SCALA2X = 30
-  final val DEFAULTparameterized = 31
-  final val INSUPERCALL = 32
+  final val STATIC = 17
+  final val OBJECT = 18
+  final val TRAIT = 19
+  final val LOCAL = 20
+  final val SYNTHETIC = 21
+  final val ARTIFACT = 22
+  final val MUTABLE = 23
+  final val LABEL = 24
+  final val FIELDaccessor = 25
+  final val CASEaccessor = 26
+  final val COVARIANT = 27
+  final val CONTRAVARIANT = 28
+  final val SCALA2X = 29
+  final val DEFAULTparameterized = 30
+  final val INSUPERCALL = 31
 
   final val SHARED = 64
   final val TERMREFdirect = 65
@@ -349,7 +347,6 @@ object TastyFormat {
        | LAZY
        | OVERRIDE
        | INLINE
-       | ABSOVERRIDE
        | STATIC
        | OBJECT
        | TRAIT
@@ -397,7 +394,6 @@ object TastyFormat {
     case LAZY => "LAZY"
     case OVERRIDE => "OVERRIDE"
     case INLINE => "INLINE"
-    case ABSOVERRIDE => "ABSOVERRIDE"
     case STATIC => "STATIC"
     case OBJECT => "OBJECT"
     case TRAIT => "TRAIT"

src/dotty/tools/dotc/core/tasty/TreePickler.scala

@@ -522,7 +522,7 @@ class TreePickler(pickler: TastyPickler) {
       if (sym.isTerm) {
         if (flags is Implicit) writeByte(IMPLICIT)
         if ((flags is Lazy) && !(sym is Module)) writeByte(LAZY)
-        if (flags is AbsOverride) writeByte(ABSOVERRIDE)
+        if (flags is AbsOverride) { writeByte(ABSTRACT); writeByte(OVERRIDE) }
         if (flags is Mutable) writeByte(MUTABLE)
         if (flags is Accessor) writeByte(FIELDaccessor)
         if (flags is CaseAccessor) writeByte(CASEaccessor)

src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -427,7 +427,12 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table) {
           case PRIVATE => addFlag(Private)
           case INTERNAL => ??? // addFlag(Internal)
           case PROTECTED => addFlag(Protected)
-          case ABSTRACT => addFlag(Abstract)
+          case ABSTRACT =>
+            readByte()
+            nextByte match {
+              case OVERRIDE => addFlag(AbsOverride)
+              case _ => flags |= Abstract
+            }
           case FINAL => addFlag(Final)
           case SEALED => addFlag(Sealed)
           case CASE => addFlag(Case)