Keep hole types in TASTy

Author: nicolasstucki

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

@@ -26,7 +26,7 @@ object TreePickler {
     override def isTerm: Boolean = isTermHole
     override def isType: Boolean = !isTermHole
     override def fallbackToText(printer: Printer): Text =
-      s"[[$idx|" ~~ printer.toTextGlobal(args, ", ") ~~ "]]"
+      s"[[$idx|" ~~ printer.toTextGlobal(tpe) ~~ "|" ~~ printer.toTextGlobal(args, ", ") ~~ "]]"
   }
 }
 
@@ -603,6 +603,7 @@ class TreePickler(pickler: TastyPickler) {
           writeByte(HOLE)
           withLength {
             writeNat(idx)
+            pickleType(tree.tpe, richTypes = true)
             args.foreach(pickleTree)
           }
       }

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

@@ -1301,6 +1301,7 @@ class TreeUnpickler(reader: TastyReader,
 
     def readHole(end: Addr, isType: Boolean)(implicit ctx: Context): Tree = {
       val idx = readNat()
+      val tpe = readType()
       val args = until(end)(readTerm())
       val splice = splices(idx)
       def wrap(arg: Tree) =

compiler/src/dotty/tools/dotc/transform/ReifyQuotes.scala

@@ -331,7 +331,23 @@ class ReifyQuotes extends MacroTransform {
      */
     private def makeHole(isTermHole: Boolean, body: Tree, splices: List[Tree], tpe: Type)(implicit ctx: Context): Hole = {
       val idx = embedded.addTree(body, NoSymbol)
-      Hole(isTermHole, idx, splices).withType(tpe).asInstanceOf[Hole]
+      val holeType = getHoleType(tpe)
+      Hole(isTermHole, idx, splices).withType(holeType).asInstanceOf[Hole]
+    }
+
+    private def getHoleType(using ctx: Context) = new TypeMap() {
+      override def apply(tp: Type): Type = tp match
+        case tp: TypeRef if tp.typeSymbol.isSplice =>
+          apply(tp.dealias)
+        case tp @ TypeRef(pre, _) if pre == NoPrefix || pre.termSymbol.isLocal =>
+          val hiBound = tp.typeSymbol.info match
+            case info @ ClassInfo(_, _, classParents, _, _) => classParents.reduce(_ & _)
+            case info => info.hiBound
+          apply(hiBound)
+        case tp @ TermRef(NoPrefix, _) =>
+          apply(tp.widenTermRefExpr)
+        case tp =>
+          mapOver(tp)
     }
 
     override def transform(tree: Tree)(implicit ctx: Context): Tree =