Drop OBJECTDEF from TastyFormat

It was not supported yet by pickler and unpickler. In fact it would be quite
awkward to support it since in the pickling format a symbol reference is the
address of the definition tree node. So if there is only a single OBJECTDEF
node, we get an ambiguity between object and its module class. This makes
tree unpickling much harder.

So I believe it is better to expose the object encoding into a lazy val
and a class definition. That also explains where OBJECTNAMEs are bound.

Author: odersky

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

@@ -57,7 +57,6 @@ Standard-Section: "ASTs" TopLevelStat*
   Stat          = Term
                   ValOrDefDef
                   TYPEDEF        Length NameRef (type_Term | Template) Modifier*   -- modifiers type name (= type | bounds)  |  moifiers class name template
-                  OBJECTDEF      Length NameRef Template Modifier*                 -- modifiers object name template
                   IMPORT         Length [IMPLIED] qual_Term Selector*              -- import implied? qual selectors
   ValOrDefDef   = VALDEF         Length NameRef type_Term rhs_Term? Modifier*      -- modifiers val name : type (= rhs)?
                   DEFDEF         Length NameRef TypeParam* Params* returnType_Term rhs_Term?
@@ -430,7 +429,6 @@ object TastyFormat {
   final val ANNOTATION = 173
   final val TERMREFin = 174
   final val TYPEREFin = 175
-  final val OBJECTDEF = 176
 
   final val METHODtype = 180
   final val ERASEDMETHODtype = 181
@@ -593,7 +591,6 @@ object TastyFormat {
     case VALDEF => "VALDEF"
     case DEFDEF => "DEFDEF"
     case TYPEDEF => "TYPEDEF"
-    case OBJECTDEF => "OBJECTDEF"
     case IMPORT => "IMPORT"
     case TYPEPARAM => "TYPEPARAM"
     case PARAMS => "PARAMS"
@@ -669,7 +666,7 @@ object TastyFormat {
    *          If negative, minus the number of leading non-reference trees.
    */
   def numRefs(tag: Int): Int = tag match {
-    case VALDEF | DEFDEF | TYPEDEF | OBJECTDEF | TYPEPARAM | PARAM | NAMEDARG | RETURN | BIND |
+    case VALDEF | DEFDEF | TYPEDEF | TYPEPARAM | PARAM | NAMEDARG | RETURN | BIND |
          SELFDEF | REFINEDtype | TERMREFin | TYPEREFin | HOLE => 1
     case RENAMED | PARAMtype => 2
     case POLYtype | TYPELAMBDAtype |

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

@@ -78,15 +78,15 @@ class TastyPrinter(bytes: Array[Byte])(implicit ctx: Context) {
           tag match {
             case RENAMED =>
               printName(); printName()
-            case VALDEF | DEFDEF | TYPEDEF | OBJECTDEF | TYPEPARAM | PARAM | NAMEDARG | BIND =>
+            case VALDEF | DEFDEF | TYPEDEF | TYPEPARAM | PARAM | NAMEDARG | BIND =>
               printName(); printTrees()
             case REFINEDtype | TERMREFin | TYPEREFin =>
               printName(); printTree(); printTrees()
             case RETURN | HOLE =>
               printNat(); printTrees()
             case METHODtype | ERASEDMETHODtype |
-                 CONTEXTUALMETHODtype | ERASEDCONTEXTUALMETHODtype |
-                 IMPLICITMETHODtype | POLYtype | TYPELAMBDAtype =>
+                 GIVENMETHODtype | ERASEDGIVENMETHODtype | IMPLICITMETHODtype |
+                 POLYtype | TYPELAMBDAtype =>
               printTree()
               until(end) { printName(); printTree() }
             case PARAMtype =>