Add new QUOTEHOLE to TASTy format

This is a new encoding of HOLE that differentiates between type and
term arguments of the hole.

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 =>
+            case RETURN | HOLE | QUOTEHOLE =>
               printNat(); printTrees()
             case METHODtype | POLYtype | TYPELAMBDAtype =>
               printTree()

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

@@ -666,14 +666,13 @@ class TreePickler(pickler: TastyPickler) {
               pickleTree(alias)
           }
         case Hole(_, idx, targs, args, _, tpt) =>
-          writeByte(HOLE)
+          writeByte(QUOTEHOLE)
           withLength {
             writeNat(idx)
-            pickleType(tpt.tpe, richTypes = true)
-            targs.foreach(pickleTree)
+            pickleTree(untpd.AppliedTypeTree(tpt, targs))
             args.foreach(pickleTree)
           }
-      }
+        }
       catch {
         case ex: TypeError =>
           report.error(ex.toMessage, tree.srcPos.focus)

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

@@ -1435,11 +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 =>
-              val idx = readNat()
-              val tpe = readType()
-              val args = until(end)(readTerm())
-              PickledHole(true, idx, args, TypeTree(tpe)).withType(tpe)
+            case HOLE | QUOTEHOLE =>
+              readHole(tag, end, isTerm = true)
             case _ =>
               readPathTerm()
           }
@@ -1467,13 +1464,8 @@ class TreeUnpickler(reader: TastyReader,
           val aliases = readStats(ctx.owner, end)
           val tpt = typeReader.readTpt()
           Block(aliases, tpt)
-        case HOLE =>
-          readByte()
-          val end = readEnd()
-          val idx = readNat()
-          val tpe = readType()
-          val args = until(end)(readTerm())
-          PickledHole(false, idx, args, TypeTree(tpe)).withType(tpe)
+        case HOLE | QUOTEHOLE =>
+          readHole(readByte(), readEnd(), isTerm = false)
         case _ =>
           if (isTypeTreeTag(nextByte)) readTerm()
           else {
@@ -1517,6 +1509,19 @@ 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)
+    }
+
 // ------ Setting positions ------------------------------------------------
 
     /** Pickled span for `addr`. */

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

@@ -122,7 +122,9 @@ 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
-                  HOLE           Length idx_Nat arg_Tree*                          -- Hole where a splice goes with sequence number idx, splice is applied to arguments `arg`s
+                  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
 
   CaseDef       = CASEDEF        Length pat_Term rhs_Tree guard_Tree?              -- case pat if guard => rhs
   ImplicitArg   = IMPLICITARG           arg_Term                                   -- implicit unapply argument
@@ -585,12 +587,14 @@ object TastyFormat {
   final val MATCHtpt = 191
   final val MATCHCASEtype = 192
 
-  final val HOLE = 255
+  final val QUOTEHOLE = 254
+  final val HOLE = 255 // Used from 3.0 to 3.3, repaced with QUOTEHOLE in 3.4+
 
   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 =
@@ -599,7 +603,7 @@ object TastyFormat {
     firstASTTreeTag <= tag && tag <= BOUNDED ||
     firstNatASTTreeTag <= tag && tag <= NAMEDARG ||
     firstLengthTreeTag <= tag && tag <= MATCHtpt ||
-    tag == HOLE
+    firstQuoteTag <= tag && tag <= HOLE
 
   def isParamTag(tag: Int): Boolean = tag == PARAM || tag == TYPEPARAM
 
@@ -802,6 +806,7 @@ object TastyFormat {
     case ANNOTATION => "ANNOTATION"
     case PRIVATEqualified => "PRIVATEqualified"
     case PROTECTEDqualified => "PROTECTEDqualified"
+    case QUOTEHOLE => "QUOTEHOLE"
     case HOLE => "HOLE"
   }
 
@@ -810,7 +815,7 @@ object TastyFormat {
    */
   def numRefs(tag: Int): Int = tag match {
     case VALDEF | DEFDEF | TYPEDEF | TYPEPARAM | PARAM | NAMEDARG | RETURN | BIND |
-         SELFDEF | REFINEDtype | TERMREFin | TYPEREFin | SELECTin | HOLE => 1
+         SELFDEF | REFINEDtype | TERMREFin | TYPEREFin | SELECTin | QUOTEHOLE | HOLE => 1
     case RENAMED | PARAMtype => 2
     case POLYtype | TYPELAMBDAtype | METHODtype => -1
     case _ => 0