Revert TastyFormat changes

Instead use a hack to convert the Into flag into the $into annotation for pickling.
This means we can merge the scheme without waiting for the next minor version.

When the scheme is stabilized we should revert this commit again to get the cleaner
treatment where the Into fag maps to the INTO tag.

Author: odersky

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

@@ -852,6 +852,9 @@ class TreePickler(pickler: TastyPickler, attributes: Attributes) {
     if (flags.is(ParamAccessor) && sym.isTerm && !sym.isSetter)
       flags = flags &~ ParamAccessor // we only generate a tag for parameter setters
     pickleFlags(flags, sym.isTerm)
+    if flags.is(Into) then
+      // Temporary measure until we can change TastyFormat to include an INTO tag
+      pickleAnnotation(sym, mdef, Annotation(defn.SilentIntoAnnot, util.Spans.NoSpan))
     val annots = sym.annotations.foreach(pickleAnnotation(sym, mdef, _))
   }
 
@@ -905,7 +908,6 @@ class TreePickler(pickler: TastyPickler, attributes: Attributes) {
       if (flags.is(Contravariant)) writeModTag(CONTRAVARIANT)
       if (flags.is(Opaque)) writeModTag(OPAQUE)
       if (flags.is(Open)) writeModTag(OPEN)
-      if (flags.is(Into)) writeModTag(INTO)
     }
   }
 

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

@@ -667,7 +667,11 @@ class TreeUnpickler(reader: TastyReader,
         }
       val annotOwner =
         if sym.owner.isClass then newLocalDummy(sym.owner) else sym.owner
-      val annots = annotFns.map(_(annotOwner))
+      var annots = annotFns.map(_(annotOwner))
+      if annots.exists(_.symbol == defn.SilentIntoAnnot) then
+        // Temporary measure until we can change TastyFormat to include an INTO tag
+        sym.setFlag(Into)
+        annots = annots.filterNot(_.symbol == defn.SilentIntoAnnot)
       sym.annotations = annots
       if sym.isOpaqueAlias then sym.setFlag(Deferred)
       val isScala2MacroDefinedInScala3 = flags.is(Macro, butNot = Inline) && flags.is(Erased)
@@ -758,7 +762,6 @@ class TreeUnpickler(reader: TastyReader,
           case TRANSPARENT => addFlag(Transparent)
           case INFIX => addFlag(Infix)
           case TRACKED => addFlag(Tracked)
-          case INTO => addFlag(Into)
           case PRIVATEqualified =>
             readByte()
             privateWithin = readWithin

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

@@ -229,7 +229,6 @@ Standard-Section: "ASTs" TopLevelStat*
                   OPEN                                                             -- an open class
                   INVISIBLE                                                        -- invisible during typechecking, except when resolving from TASTy
                   TRACKED                                                          -- a tracked class parameter / a dependent class
-                  INTO                                                             -- a trait or class declared with `into`
                   Annotation
 
   Variance      = STABLE                                                           -- invariant
@@ -512,7 +511,6 @@ object TastyFormat {
   final val EMPTYCLAUSE = 45
   final val SPLITCLAUSE = 46
   final val TRACKED = 47
-  final val INTO = 48
 
   // Tree Cat. 2:    tag Nat
   final val firstNatTreeTag = SHAREDterm
@@ -705,8 +703,7 @@ object TastyFormat {
        | ANNOTATION
        | PRIVATEqualified
        | PROTECTEDqualified
-       | TRACKED
-       | INTO => true
+       | TRACKED => true
     case _ => false
   }
 
@@ -766,8 +763,6 @@ object TastyFormat {
     case PARAMsetter => "PARAMsetter"
     case EXPORTED => "EXPORTED"
     case OPEN => "OPEN"
-    case INTO => "INTO"
-    case TRACKED => "TRACKED"
     case INVISIBLE => "INVISIBLE"
     case PARAMalias => "PARAMalias"
     case EMPTYCLAUSE => "EMPTYCLAUSE"