Define splice hole in library

Fixes scala#17137

Author: nicolasstucki

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -848,6 +848,9 @@ class Definitions {
   @tu lazy val QuoteUnpicklerClass: ClassSymbol = requiredClass("scala.quoted.runtime.QuoteUnpickler")
     @tu lazy val QuoteUnpickler_unpickleExprV2: Symbol = QuoteUnpicklerClass.requiredMethod("unpickleExprV2")
     @tu lazy val QuoteUnpickler_unpickleTypeV2: Symbol = QuoteUnpicklerClass.requiredMethod("unpickleTypeV2")
+  @tu lazy val QuoteUnpicklerModule: Symbol = requiredModule("scala.quoted.runtime.QuoteUnpickler")
+    @tu lazy val QuoteUnpickler_exprHole : Symbol = QuoteUnpicklerModule.requiredMethod("hole")
+    @tu lazy val QuoteUnpickler_typeHole : Symbol = QuoteUnpicklerModule.requiredType("hole")
 
   @tu lazy val QuoteMatchingClass: ClassSymbol = requiredClass("scala.quoted.runtime.QuoteMatching")
     @tu lazy val QuoteMatching_ExprMatch: Symbol = QuoteMatchingClass.requiredMethod("ExprMatch")

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

@@ -334,7 +334,7 @@ class TreePickler(pickler: TastyPickler) {
         pickleName(sym.name)
         pickleParams
         tpt match {
-          case _: Template | _: Hole => pickleTree(tpt)
+          case _: Template => pickleTree(tpt)
           case _ if tpt.isType => pickleTpt(tpt)
         }
         pickleTreeUnlessEmpty(rhs)
@@ -413,7 +413,6 @@ class TreePickler(pickler: TastyPickler) {
               var ename = tree.symbol.targetName
               val selectFromQualifier =
                 name.isTypeName
-                || 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
@@ -665,13 +664,6 @@ class TreePickler(pickler: TastyPickler) {
               pickleTree(hi)
               pickleTree(alias)
           }
-        case Hole(_, idx, args, _, tpt) =>
-          writeByte(HOLE)
-          withLength {
-            writeNat(idx)
-            pickleType(tpt.tpe, richTypes = true)
-            args.foreach(pickleTree)
-          }
       }
       catch {
         case ex: TypeError =>

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

@@ -3,6 +3,7 @@ package dotty.tools.dotc.quoted
 import dotty.tools.dotc.ast.Trees._
 import dotty.tools.dotc.ast.{TreeTypeMap, tpd}
 import dotty.tools.dotc.config.Printers._
+import dotty.tools.dotc.core.Constants._
 import dotty.tools.dotc.core.Contexts._
 import dotty.tools.dotc.core.Decorators._
 import dotty.tools.dotc.core.Flags._
@@ -125,6 +126,34 @@ object PickledQuotes {
               val quotedType = evalHole.nn.apply(idx, reifyTypeHoleArgs(args))
               PickledQuotes.quotedTypeToTree(quotedType)
           }
+        case Apply(TypeApply(hole, List(idxTree, tpt, targs)), List(Typed(SeqLiteral(args, _), _))) if hole.symbol == defn.QuoteUnpickler_exprHole =>
+          inContext(SpliceScope.contextWithNewSpliceScope(tree.sourcePos)) {
+            val idx = (idxTree.tpe: @unchecked) match
+              case ConstantType(Constant(idx: Int)) => idx
+
+            def kListTypes(tp: Type): List[TypeTree] = tp match
+              case AppliedType(kCons: TypeRef, headType :: tailType :: Nil) if kCons.symbol == defn.QuoteMatching_KCons =>
+                TypeTree(headType) :: kListTypes(tailType)
+              case kNil: TypeRef if kNil.symbol == defn.QuoteMatching_KNil =>
+                Nil
+
+            val targsList = kListTypes(targs.tpe)
+            val reifiedTypeArgs = reifyTypeHoleArgs(targsList)
+            val reifiedArgs = reifyTypeHoleArgs(targsList)
+
+            val argRefs = args.map(methPart) // strip dummy arguments
+
+            val quotedExpr = (termHole: @unchecked) match
+              case ExprHole.V2(evalHole) =>
+                  evalHole.nn.apply(idx, reifiedTypeArgs ::: reifyExprHoleV2Args(argRefs), QuotesImpl())
+
+            val filled = PickledQuotes.quotedExprToTree(quotedExpr)
+
+            // We need to make sure a hole is created with the source file of the surrounding context, even if
+            // it filled with contents a different source file.
+            if filled.source == ctx.source then filled
+            else filled.cloneIn(ctx.source).withSpan(tree.span)
+          }
         case tree =>
           if tree.isDef then
             tree.symbol.annotations = tree.symbol.annotations.map {
@@ -173,7 +202,11 @@ object PickledQuotes {
                     // To keep for backwards compatibility. In some older version we missed the creation of some holes.
                     tpt
               case TypeHole.V2(types) =>
-                val Hole(_, idx, _, _, _) = tdef.rhs: @unchecked
+                val idx = tdef.rhs match
+                  case Hole(_, idx, _, _, _) => idx
+                  case rhs: TypeTree =>
+                    rhs.tpe match
+                      case AppliedType(tycon, ConstantType(Constant(idx: Int)) :: _) if tycon.typeSymbol == defn.QuoteUnpickler_typeHole => idx
                 PickledQuotes.quotedTypeToTree(types.nn.apply(idx))
             (tdef.symbol, tree.tpe)
         }.toMap

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

@@ -33,11 +33,13 @@ import scala.annotation.constructorOnly
  *      val x1: U1 = ???
  *      val x2: U2 = ???
  *      ...
- *      {{{ 3 | x1 | contents0 | T0 }}} // hole
+ *      {{{ 3 | T0 | x1 | contents0 }}} // hole
  *      ...
- *      {{{ 4 | x2 | contents1 | T1 }}} // hole
+ *      {{{ 4 | T1 | x2 | contents1 }}} // hole
  *      ...
- *      {{{ 5 | x1, x2 | contents2 | T2 }}} // hole
+ *      {{{ 5 | T2 | x1, x2 | contents2 |  }}} // hole
+ *      ...
+ *      {{{ 6 | T2 | X0, x1 | contents2 |  }}} // hole
  *      ...
  *    }
  *    ```
@@ -50,11 +52,13 @@ import scala.annotation.constructorOnly
  *         val x1 = ???
  *         val x2 = ???
  *         ...
- *      {{{ 0 | x1 | | T0 }}} // hole
- *      ...
- *      {{{ 1 | x2 | | T1 }}} // hole
- *      ...
- *      {{{ 2 | x1, x2 | | T2 }}} // hole
+ *         hole[3, T0, KNil](x1) // hole
+ *         ...
+ *         hole[4, T1, KNil](x2) // hole
+ *         ...
+ *         hole[5, T2, KNil](x1, x2) // hole
+ *         ...
+ *         hole[6, T2, KCons[X0, KNil]](x1) // hole
  *         ...
  *       ]],
  *       typeHole = (idx: Int, args: List[Any]) => idx match {
@@ -65,6 +69,7 @@ import scala.annotation.constructorOnly
  *         case 3 => content0.apply(args(0).asInstanceOf[Expr[U1]]).apply(quotes) // beta reduced
  *         case 4 => content1.apply(args(0).asInstanceOf[Expr[U2]]).apply(quotes) // beta reduced
  *         case 5 => content2.apply(args(0).asInstanceOf[Expr[U1]], args(1).asInstanceOf[Expr[U2]]).apply(quotes) // beta reduced
+ *         case 6 => content2.apply(args(0).asInstanceOf[Type[?]], args(1).asInstanceOf[Expr[U1]]).apply(quotes) // beta reduced
  *       },
  *     )
  *    ```
@@ -126,13 +131,35 @@ class PickleQuotes extends MacroTransform {
       private val contents = List.newBuilder[Tree]
       override def transform(tree: tpd.Tree)(using Context): tpd.Tree =
         tree match
-          case tree @ Hole(isTerm, _, _, content, _) =>
+          case tree @ Hole(isTerm, idx, rawArgs, content, tpt) =>
             if !content.isEmpty then
               contents += content
             val holeType =
               if isTerm then getTermHoleType(tree.tpe) else getTypeHoleType(tree.tpe)
             val hole = cpy.Hole(tree)(content = EmptyTree, TypeTree(holeType))
-            if isTerm then Inlined(EmptyTree, Nil, hole).withSpan(tree.span) else hole
+            val args = rawArgs.filter(_.isTerm).map { arg =>
+              def fullyAppliedToDummyArgs(arg: Tree, tpe: Type): Tree =
+                tpe match
+                  case tpe: MethodType =>
+                    fullyAppliedToDummyArgs(arg.appliedToArgs(tpe.paramNames.map(_ => tpd.ref(defn.Predef_undefined))), tpe.resultType)
+                  case tpe: PolyType =>
+                    fullyAppliedToDummyArgs(arg.appliedToTypes(tpe.paramInfos.map(_.loBound)), tpe.resultType)
+                  case _ => arg
+              fullyAppliedToDummyArgs(arg, arg.tpe.widenTermRefExpr)
+            }
+            val targs = rawArgs.filter(!_.isTerm)
+            val typeArgs = tpd.hkNestedPairsTypeTree(targs).tpe
+            val holeTypeArgs = List(ConstantType(Constant(idx)), holeType, typeArgs)
+            val newHole =
+              if isTerm then
+                ref(defn.QuoteUnpickler_exprHole)
+                  .appliedToTypes(holeTypeArgs)
+                  .appliedToVarargs(args, TypeTree(defn.AnyType))
+                  .withSpan(tree.span)
+              else
+                TypeTree(AppliedType(defn.QuoteUnpickler_typeHole.typeRef, holeTypeArgs))
+                  .withSpan(tree.span)
+            if isTerm then Inlined(EmptyTree, Nil, newHole).withSpan(tree.span) else newHole
           case tree: DefTree =>
             val newAnnotations = tree.symbol.annotations.mapconserve { annot =>
               annot.derivedAnnotation(transform(annot.tree)(using ctx.withOwner(tree.symbol)))

library/src/scala/quoted/runtime/QuoteUnpickler.scala

@@ -1,5 +1,6 @@
 package scala.quoted.runtime
 
+import scala.annotation.compileTimeOnly
 import scala.quoted.{Quotes, Expr, Type}
 
 /** Part of the Quotes interface that needs to be implemented by the compiler but is not visible to users */
@@ -32,3 +33,10 @@ trait QuoteUnpickler:
    *  Generated for code compiled with Scala 3.2.0+
    */
   def unpickleTypeV2[T <: AnyKind](pickled: String | List[String], types: Null | Seq[Type[?]]): scala.quoted.Type[T]
+
+object QuoteUnpickler:
+  @compileTimeOnly("Illegal reference to `scala.quoted.runtime.Expr.hole`")
+  def hole[Idx <: Int, T, TArgs](args: Any*): T = ???
+
+  @compileTimeOnly("Illegal reference to `scala.quoted.runtime.Expr.hole`")
+  type hole[Idx <: Int, T, TArgs] <: T

project/MiMaFilters.scala

@@ -17,6 +17,8 @@ object MiMaFilters {
     ProblemFilters.exclude[MissingClassProblem]("scala.util.boundary$Break"),
     ProblemFilters.exclude[MissingClassProblem]("scala.util.boundary$Label"),
     ProblemFilters.exclude[MissingClassProblem]("scala.quoted.runtime.QuoteMatching$"),
+    ProblemFilters.exclude[MissingClassProblem]("scala.quoted.runtime.QuoteUnpickler$"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.quoted.runtime.QuoteUnpickler.hole"),
 
     // Scala.js only: new runtime support class in 3.2.3; not available to users
     ProblemFilters.exclude[MissingClassProblem]("scala.scalajs.runtime.AnonFunctionXXL"),

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

@@ -122,7 +122,7 @@ 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 tpe_Type arg_Tree*                 -- Splice hole with index `idx`, the type of the hole `tpe`, type and term arguments of the hole `arg`s
+                  HOLE           Length idx_Nat tpe_Type arg_Tree*                 -- Splice hole with index `idx`, the type of the hole `tpe`, type and term arguments of the hole `arg`s (only used in 3.0-3.3)
 
 
   CaseDef       = CASEDEF        Length pat_Term rhs_Tree guard_Tree?              -- case pat if guard => rhs