Make Hole a proper Tree in Trees

This is a first step into making the Hole trees Ycheckable.
To YCheck them we need an untyped version of the tree.

Author: nicolasstucki

compiler/src/dotty/tools/dotc/ast/TreeTypeMap.scala

@@ -7,7 +7,6 @@ import Types._, Contexts._, Flags._
 import Symbols._, Annotations._, Trees._, Symbols._, Constants.Constant
 import Decorators._
 import dotty.tools.dotc.transform.SymUtils._
-import core.tasty.TreePickler.Hole
 
 /** A map that applies three functions and a substitution together to a tree and
  *  makes sure they are coordinated so that the result is well-typed. The functions are

compiler/src/dotty/tools/dotc/ast/Trees.scala

@@ -16,7 +16,6 @@ import annotation.internal.sharable
 import annotation.unchecked.uncheckedVariance
 import annotation.constructorOnly
 import Decorators._
-import dotty.tools.dotc.core.tasty.TreePickler.Hole
 
 object Trees {
 
@@ -980,6 +979,15 @@ object Trees {
   def genericEmptyValDef[T >: Untyped]: ValDef[T]       = theEmptyValDef.asInstanceOf[ValDef[T]]
   def genericEmptyTree[T >: Untyped]: Thicket[T]        = theEmptyTree.asInstanceOf[Thicket[T]]
 
+  /** Tree that replaces a splice in pickled quotes.
+   *  It is only used when picking quotes (Will never be in a TASTy file).
+   */
+  case class Hole[-T >: Untyped](isTermHole: Boolean, idx: Int, args: List[Tree[T]])(implicit @constructorOnly src: SourceFile) extends Tree[T] {
+    type ThisTree[-T >: Untyped] <: Hole[T]
+    override def isTerm: Boolean = isTermHole
+    override def isType: Boolean = !isTermHole
+  }
+
   def flatten[T >: Untyped](trees: List[Tree[T]]): List[Tree[T]] = {
     def recur(buf: ListBuffer[Tree[T]], remaining: List[Tree[T]]): ListBuffer[Tree[T]] =
       remaining match {
@@ -1104,6 +1112,8 @@ object Trees {
     type Annotated = Trees.Annotated[T]
     type Thicket = Trees.Thicket[T]
 
+    type Hole = Trees.Hole[T]
+
     @sharable val EmptyTree: Thicket = genericEmptyTree
     @sharable val EmptyValDef: ValDef = genericEmptyValDef
     @sharable val ContextualEmptyTree: Thicket = new EmptyTree() // an empty tree marking a contextual closure

compiler/src/dotty/tools/dotc/ast/tpd.scala

@@ -44,7 +44,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   def Apply(fn: Tree, args: List[Tree])(using Context): Apply = fn match
     case Block(Nil, expr) =>
       Apply(expr, args)
-    case _: RefTree | _: GenericApply | _: Inlined | _: tasty.TreePickler.Hole =>
+    case _: RefTree | _: GenericApply | _: Inlined | _: Hole =>
       ta.assignType(untpd.Apply(fn, args), fn, args)
 
   def TypeApply(fn: Tree, args: List[Tree])(using Context): TypeApply = fn match

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

@@ -91,7 +91,7 @@ class PositionPickler(
           | _: Trees.PackageDef[?]
           // holes can change source files when filled, which means
           // they might lose their position
-          | _: TreePickler.Hole => true
+          | _: Trees.Hole[?] => true
       case _ => false
     }
 

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

@@ -22,21 +22,10 @@ import annotation.constructorOnly
 import collection.mutable
 import dotty.tools.tasty.TastyFormat.ASTsSection
 
-object TreePickler {
-
-  case class Hole(isTermHole: Boolean, idx: Int, args: List[tpd.Tree])(implicit @constructorOnly src: SourceFile) extends tpd.Tree {
-    override def isTerm: Boolean = isTermHole
-    override def isType: Boolean = !isTermHole
-    override def fallbackToText(printer: Printer): Text =
-      if isTermHole then s"{{{ $idx |" ~~ printer.toTextGlobal(tpe) ~~ "|" ~~ printer.toTextGlobal(args, ", ") ~~ "}}}"
-      else s"[[[ $idx |" ~~ printer.toTextGlobal(tpe) ~~ "|" ~~ printer.toTextGlobal(args, ", ") ~~ "]]]"
-  }
-}
 
 class TreePickler(pickler: TastyPickler) {
   val buf: TreeBuffer = new TreeBuffer
   pickler.newSection(ASTsSection, buf)
-  import TreePickler._
   import buf._
   import pickler.nameBuffer.nameIndex
   import tpd._
@@ -411,7 +400,7 @@ class TreePickler(pickler: TastyPickler) {
               var ename = tree.symbol.targetName
               val selectFromQualifier =
                 name.isTypeName
-                || qual.isInstanceOf[TreePickler.Hole] // holes have no symbol
+                || qual.isInstanceOf[Hole] // holes have no symbol
                 || sig == Signature.NotAMethod // no overload resolution necessary
                 || !tree.denot.symbol.exists // polymorphic function type
                 || tree.denot.asSingleDenotation.isRefinedMethod // refined methods have no defining class symbol

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

@@ -1290,7 +1290,7 @@ class TreeUnpickler(reader: TastyReader,
               val idx = readNat()
               val tpe = readType()
               val args = until(end)(readTerm())
-              TreePickler.Hole(true, idx, args).withType(tpe)
+              Hole(true, idx, args).withType(tpe)
             case _ =>
               readPathTerm()
           }
@@ -1326,7 +1326,7 @@ class TreeUnpickler(reader: TastyReader,
           val idx = readNat()
           val tpe = readType()
           val args = until(end)(readTerm())
-          TreePickler.Hole(false, idx, args).withType(tpe)
+          Hole(false, idx, args).withType(tpe)
         case _ =>
           if (isTypeTreeTag(nextByte)) readTerm()
           else {

compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -699,6 +699,10 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
         "Thicket {" ~~ toTextGlobal(trees, "\n") ~~ "}"
       case MacroTree(call) =>
         keywordStr("macro ") ~ toTextGlobal(call)
+      case Hole(isTermHole, idx, args) =>
+        val (prefix, postfix) = if isTermHole then ("{{{ ", " }}}") else ("[[[ ", " ]]]")
+        val argsText = toTextGlobal(args, ", ")
+        prefix ~~ idx.toString ~~ "|" ~~ argsText ~~ postfix
       case _ =>
         tree.fallbackToText(this)
     }

compiler/src/dotty/tools/dotc/quoted/PickledQuotes.scala

@@ -11,7 +11,6 @@ import dotty.tools.dotc.core.NameKinds
 import dotty.tools.dotc.core.Mode
 import dotty.tools.dotc.core.Symbols._
 import dotty.tools.dotc.core.Types._
-import dotty.tools.dotc.core.tasty.TreePickler.Hole
 import dotty.tools.dotc.core.tasty.{ PositionPickler, TastyPickler, TastyPrinter }
 import dotty.tools.dotc.core.tasty.DottyUnpickler
 import dotty.tools.dotc.core.tasty.TreeUnpickler.UnpickleMode

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

@@ -11,7 +11,6 @@ import Constants._
 import ast.Trees._
 import ast.{TreeTypeMap, untpd}
 import util.Spans._
-import tasty.TreePickler.Hole
 import SymUtils._
 import NameKinds._
 import dotty.tools.dotc.ast.tpd

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

@@ -11,7 +11,6 @@ import Constants._
 import ast.Trees._
 import ast.{TreeTypeMap, untpd}
 import util.Spans._
-import tasty.TreePickler.Hole
 import SymUtils._
 import NameKinds._
 import dotty.tools.dotc.ast.tpd

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

@@ -12,7 +12,6 @@ import dotty.tools.dotc.core.NameKinds._
 import dotty.tools.dotc.core.StagingContext._
 import dotty.tools.dotc.core.StdNames._
 import dotty.tools.dotc.core.Symbols._
-import dotty.tools.dotc.core.tasty.TreePickler.Hole
 import dotty.tools.dotc.core.Types._
 import dotty.tools.dotc.quoted._
 import dotty.tools.dotc.util.{SourceFile, SrcPos}

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

@@ -13,7 +13,6 @@ import dotty.tools.dotc.core.Contexts._
 import dotty.tools.dotc.core.StagingContext._
 import dotty.tools.dotc.core.StdNames._
 import dotty.tools.dotc.core.Symbols._
-import dotty.tools.dotc.core.tasty.TreePickler.Hole
 import dotty.tools.dotc.quoted._
 import dotty.tools.dotc.util.Spans._
 import dotty.tools.dotc.util.Property