Add infrastructure for pickling/unpickling with holes and splices

Author: odersky

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

@@ -20,7 +20,7 @@ object DottyUnpickler {
   class TreeSectionUnpickler(posUnpickler: Option[PositionUnpickler])
   extends SectionUnpickler[TreeUnpickler]("ASTs") {
     def unpickle(reader: TastyReader, nameAtRef: NameTable) =
-      new TreeUnpickler(reader, nameAtRef, posUnpickler)
+      new TreeUnpickler(reader, nameAtRef, posUnpickler, Seq.empty)
   }
 
   class PositionsSectionUnpickler extends SectionUnpickler[PositionUnpickler]("Positions") {

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

@@ -0,0 +1,14 @@
+package dotty.tools
+package dotc
+package core
+package tasty
+
+import ast.Trees._
+
+object Splicing {
+  import ast.tpd._
+
+  type Splice = AnyRef /* tpd.Tree | tpd.Tree => tpd.Tree */
+
+  case class Hole(args: List[Tree]) extends TermTree
+}

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

@@ -109,6 +109,7 @@ Standard-Section: "ASTs" TopLevelStat*
                   BYNAMEtpt             underlying_Term
                   EMPTYTREE
                   SHARED                term_ASTRef
+                  HOLE           Length idx_Nat arg_Tree*
   Application   = APPLY          Length fn_Term arg_Term*
 
                   TYPEAPPLY      Length fn_Term arg_Type*
@@ -396,6 +397,7 @@ object TastyFormat {
   final val ANNOTATION = 173
   final val TERMREFin = 174
   final val TYPEREFin = 175
+  final val HOLE = 255
 
   final val firstSimpleTreeTag = UNITconst
   final val firstNatTreeTag = SHARED
@@ -555,6 +557,7 @@ object TastyFormat {
     case SUPERtype => "SUPERtype"
     case TERMREFin => "TERMREFin"
     case TYPEREFin => "TYPEREFin"
+
     case REFINEDtype => "REFINEDtype"
     case REFINEDtpt => "REFINEDtpt"
     case APPLIEDtype => "APPLIEDtype"
@@ -576,14 +579,15 @@ object TastyFormat {
     case ANNOTATION => "ANNOTATION"
     case PRIVATEqualified => "PRIVATEqualified"
     case PROTECTEDqualified => "PROTECTEDqualified"
+    case HOLE => "HOLE"
   }
 
   /** @return If non-negative, the number of leading references (represented as nats) of a length/trees entry.
    *          If negative, minus the number of leading non-reference trees.
    */
   def numRefs(tag: Int) = tag match {
     case VALDEF | DEFDEF | TYPEDEF | TYPEPARAM | PARAM | NAMEDARG | RETURN | BIND |
-         SELFDEF | REFINEDtype | TERMREFin | TYPEREFin => 1
+         SELFDEF | REFINEDtype | TERMREFin | TYPEREFin | HOLE => 1
     case RENAMED | PARAMtype => 2
     case POLYtype | METHODtype | TYPELAMBDAtype => -1
     case _ => 0

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

@@ -14,6 +14,7 @@ import StdNames.nme
 import TastyBuffer._
 import TypeApplications._
 import transform.SymUtils._
+import Splicing.Hole
 import config.Config
 
 class TreePickler(pickler: TastyPickler) {
@@ -27,6 +28,8 @@ class TreePickler(pickler: TastyPickler) {
   private val forwardSymRefs = Symbols.newMutableSymbolMap[List[Addr]]
   private val pickledTypes = new java.util.IdentityHashMap[Type, Any] // Value type is really Addr, but that's not compatible with null
 
+  private var holeCount = 0
+
   private def withLength(op: => Unit) = {
     val lengthAddr = reserveRef(relative = true)
     op
@@ -542,6 +545,13 @@ class TreePickler(pickler: TastyPickler) {
         case TypeBoundsTree(lo, hi) =>
           writeByte(TYPEBOUNDStpt)
           withLength { pickleTree(lo); pickleTree(hi) }
+        case Hole(args) =>
+          writeByte(HOLE)
+          withLength {
+            writeNat(holeCount)
+            holeCount += 1
+            args.foreach(pickleTree)
+          }
       }
       catch {
         case ex: AssertionError =>

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

@@ -11,6 +11,7 @@ import util.Positions._
 import ast.{tpd, Trees, untpd}
 import Trees._
 import Decorators._
+import Splicing.Splice
 import transform.SymUtils._
 import TastyUnpickler._, TastyBuffer._
 import scala.annotation.{tailrec, switch}
@@ -25,7 +26,10 @@ import config.Config
  *  @param tastyName       the nametable
  *  @param posUNpicklerOpt the unpickler for positions, if it exists
  */
-class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpicklerOpt: Option[PositionUnpickler]) {
+class TreeUnpickler(reader: TastyReader,
+                    nameAtRef: NameRef => TermName,
+                    posUnpicklerOpt: Option[PositionUnpickler],
+                    splices: Seq[Splice]) {
   import TastyFormat._
   import TreeUnpickler._
   import tpd._
@@ -1031,6 +1035,10 @@ class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpi
               LambdaTypeTree(tparams, body)
             case TYPEBOUNDStpt =>
               TypeBoundsTree(readTpt(), readTpt())
+            case HOLE =>
+              val idx = readNat()
+              val args = until(end)(readTerm())
+              (splices(idx) /: args)(_.asInstanceOf[Tree => Tree](_)).asInstanceOf[Tree]
             case _ =>
               readPathTerm()
           }