Encode new HOLE format without adding a new tag

Author: nicolasstucki

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

@@ -131,7 +131,7 @@ class TastyPrinter(bytes: Array[Byte]) {
               printName(); printTrees()
             case REFINEDtype | TERMREFin | TYPEREFin | SELECTin =>
               printName(); printTree(); printTrees()
-            case RETURN | HOLE | QUOTEHOLE =>
+            case RETURN | HOLE =>
               printNat(); printTrees()
             case METHODtype | POLYtype | TYPELAMBDAtype =>
               printTree()

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

@@ -666,9 +666,9 @@ class TreePickler(pickler: TastyPickler) {
               pickleTree(alias)
           }
         case Hole(_, idx, targs, args, _, tpt) =>
-          writeByte(QUOTEHOLE)
+          writeByte(HOLE)
           withLength {
-            writeNat(idx)
+            writeNat(0x0100_0000 | idx)
             pickleTree(untpd.AppliedTypeTree(tpt, targs))
             args.foreach(pickleTree)
           }

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

@@ -1435,8 +1435,8 @@ class TreeUnpickler(reader: TastyReader,
               val hi = if currentAddr == end then lo else readTpt()
               val alias = if currentAddr == end then EmptyTree else readTpt()
               createNullableTypeBoundsTree(lo, hi, alias)
-            case HOLE | QUOTEHOLE =>
-              readHole(tag, end, isTerm = true)
+            case HOLE =>
+              readHole(end, isTerm = true)
             case _ =>
               readPathTerm()
           }
@@ -1464,8 +1464,9 @@ class TreeUnpickler(reader: TastyReader,
           val aliases = readStats(ctx.owner, end)
           val tpt = typeReader.readTpt()
           Block(aliases, tpt)
-        case HOLE | QUOTEHOLE =>
-          readHole(readByte(), readEnd(), isTerm = false)
+        case HOLE =>
+          readByte()
+          readHole(readEnd(), isTerm = false)
         case _ =>
           if (isTypeTreeTag(nextByte)) readTerm()
           else {
@@ -1509,18 +1510,17 @@ class TreeUnpickler(reader: TastyReader,
       owner => new LazyReader(localReader, owner, mode, source, op)
     }
 
-    def readHole(tag: Int, end: Addr, isTerm: Boolean)(using Context): Tree = tag match {
-      case QUOTEHOLE =>
-        val idx = readNat()
-        val AppliedTypeTree(tpt, targs) = readTerm(): @unchecked
-        val args = until(end)(readTerm())
-        PickledHole(isTerm, idx, targs ::: args, tpt).withType(tpt.tpe)
-      case HOLE =>
-        val idx = readNat()
-        val tpe = readType()
-        val args = until(end)(readTerm())
-        PickledHole(isTerm, idx, args, TypeTree(tpe)).withType(tpe)
-    }
+    def readHole(end: Addr, isTerm: Boolean)(using Context): Tree =
+      val idx = readNat()
+      idx >> 24 match
+        case 0 =>
+          val tpe = readType()
+          val args = until(end)(readTerm())
+          PickledHole(isTerm, idx, args, TypeTree(tpe)).withType(tpe)
+        case 1 =>
+          val AppliedTypeTree(tpt, targs) = readTerm(): @unchecked
+          val args = until(end)(readTerm())
+          PickledHole(isTerm, idx & 0x00FF_FFFF, targs ::: args, tpt).withType(tpt.tpe)
 
 // ------ Setting positions ------------------------------------------------
 

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

@@ -122,9 +122,10 @@ Standard-Section: "ASTs" TopLevelStat*
                   MATCHtpt       Length bound_Term? sel_Term CaseDef*              -- sel match { CaseDef } where `bound` is optional upper bound of all rhs
                   BYNAMEtpt             underlying_Term                            -- => underlying
                   SHAREDterm            term_ASTRef                                -- Link to previously serialized term
-                  QUOTEHOLE      Length idx_Nat tptTargs_Tree arg_Tree*            -- Splice hole with index `idx`, the type of the hole `tpt`, type arguments `targ`s and term arguments `args`s
-                                                                                      -- tptTargs=APPLIEDtpt(tpt,targ*), this is not a true type application. Reused for its structure.
-                  HOLE           Length idx_Nat tpe_Type arg_Tree*                 -- Splice hole with index `idx`, the type of the hole `tpe`, type and term arguments `args`s
+                  HOLE           Length idxVersion_Nat tpe_Type|tptTargs_Tree arg_Tree* -- Splice hole with index `idx=idxVersion & 0x00FFFFFF` and `version = idxVersion >> 24`,
+                                                                                      -- if `version == 0`: the type of the hole `tpe`, type and term arguments `args`s
+                                                                                      -- if `version == 1`: the type of the hole `tpt`, type arguments `targ`s and term arguments `args`s
+                                                                                        -- tptTargs=APPLIEDtpt(tpt,targ*), this is not a true type application. Reused for its structure.
 
   CaseDef       = CASEDEF        Length pat_Term rhs_Tree guard_Tree?              -- case pat if guard => rhs
   ImplicitArg   = IMPLICITARG           arg_Term                                   -- implicit unapply argument
@@ -587,14 +588,12 @@ object TastyFormat {
   final val MATCHtpt = 191
   final val MATCHCASEtype = 192
 
-  final val QUOTEHOLE = 254
-  final val HOLE = 255 // Used from 3.0 to 3.3, repaced with QUOTEHOLE in 3.4+
+  final val HOLE = 255
 
   final val firstNatTreeTag = SHAREDterm
   final val firstASTTreeTag = THIS
   final val firstNatASTTreeTag = IDENT
   final val firstLengthTreeTag = PACKAGE
-  final val firstQuoteTag = QUOTEHOLE
 
   /** Useful for debugging */
   def isLegalTag(tag: Int): Boolean =
@@ -603,7 +602,7 @@ object TastyFormat {
     firstASTTreeTag <= tag && tag <= BOUNDED ||
     firstNatASTTreeTag <= tag && tag <= NAMEDARG ||
     firstLengthTreeTag <= tag && tag <= MATCHtpt ||
-    firstQuoteTag <= tag && tag <= HOLE
+    tag == HOLE
 
   def isParamTag(tag: Int): Boolean = tag == PARAM || tag == TYPEPARAM
 
@@ -806,7 +805,6 @@ object TastyFormat {
     case ANNOTATION => "ANNOTATION"
     case PRIVATEqualified => "PRIVATEqualified"
     case PROTECTEDqualified => "PROTECTEDqualified"
-    case QUOTEHOLE => "QUOTEHOLE"
     case HOLE => "HOLE"
   }
 
@@ -815,7 +813,7 @@ object TastyFormat {
    */
   def numRefs(tag: Int): Int = tag match {
     case VALDEF | DEFDEF | TYPEDEF | TYPEPARAM | PARAM | NAMEDARG | RETURN | BIND |
-         SELFDEF | REFINEDtype | TERMREFin | TYPEREFin | SELECTin | QUOTEHOLE | HOLE => 1
+         SELFDEF | REFINEDtype | TERMREFin | TYPEREFin | SELECTin | HOLE => 1
     case RENAMED | PARAMtype => 2
     case POLYtype | TYPELAMBDAtype | METHODtype => -1
     case _ => 0