Fix #5247: Support type blocks

Type block are represented with `Block` nodes where all statements
are `TypeDef`s and the expression is a `TypeTree`.

Author: nicolasstucki

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

@@ -484,8 +484,10 @@ object Trees {
 
   /** { stats; expr } */
   case class Block[-T >: Untyped] private[ast] (stats: List[Tree[T]], expr: Tree[T])
-    extends TermTree[T] {
+    extends Tree[T] {
     type ThisTree[-T >: Untyped] = Block[T]
+    override def isTerm: Boolean = expr.isTerm
+    override def isType: Boolean = expr.isType
   }
 
   /** if cond then thenp else elsep */

compiler/src/dotty/tools/dotc/config/Printers.scala

@@ -28,6 +28,7 @@ object Printers {
   val overload: Printer = noPrinter
   val patmatch: Printer = noPrinter
   val pickling: Printer = noPrinter
+  val quotePickling: Printer = noPrinter
   val plugins: Printer = noPrinter
   val simplify: Printer = noPrinter
   val subtyping: Printer = noPrinter

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

@@ -89,20 +89,20 @@ object PickledQuotes {
     if (tree.pos.exists)
       new PositionPickler(pickler, treePkl.buf.addrOfTree).picklePositions(tree :: Nil)
 
-    if (pickling ne noPrinter)
+    if (quotePickling ne noPrinter)
       println(i"**** pickling quote of \n${tree.show}")
 
     val pickled = pickler.assembleParts()
 
-    if (pickling ne noPrinter)
+    if (quotePickling ne noPrinter)
       new TastyPrinter(pickled).printContents()
 
     pickled
   }
 
   /** Unpickle TASTY bytes into it's tree */
   private def unpickle(bytes: Array[Byte], splices: Seq[Any], isType: Boolean)(implicit ctx: Context): Tree = {
-    if (pickling ne noPrinter) {
+    if (quotePickling ne noPrinter) {
       println(i"**** unpickling quote from TASTY")
       new TastyPrinter(bytes).printContents()
     }
@@ -112,7 +112,7 @@ object PickledQuotes {
     unpickler.enter(Set.empty)
     val tree = unpickler.tree
 
-    if (pickling ne noPrinter)
+    if (quotePickling ne noPrinter)
       println(i"**** unpickle quote ${tree.show}")
 
     tree

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

@@ -4,25 +4,35 @@ package core
 package tasty
 
 import Comments.CommentsContext
-import Contexts._, Symbols._, Types._, Scopes._, SymDenotations._, Names._, NameOps._
-import StdNames._, Flags._, Constants._, Annotations._
+import Contexts._
+import Symbols._
+import Types._
+import Scopes._
+import SymDenotations._
+import Names._
+import NameOps._
+import StdNames._
+import Flags._
+import Constants._
+import Annotations._
 import NameKinds._
 import typer.Checking.checkNonCyclic
 import util.Positions._
-import ast.{tpd, untpd, Trees}
+import ast.{TreeTypeMap, Trees, tpd, untpd}
 import Trees._
 import Decorators._
 import transform.SymUtils._
 import TastyBuffer._
-import scala.annotation.{tailrec, switch}
+
+import scala.annotation.{switch, tailrec}
 import scala.collection.mutable.ListBuffer
 import scala.collection.mutable
 import config.Printers.pickling
 import core.quoted.PickledQuotes
+
 import scala.quoted
 import scala.quoted.Types.TreeType
 import scala.quoted.Exprs.TastyTreeExpr
-
 import scala.annotation.internal.sharable
 
 /** Unpickler for typed trees
@@ -353,8 +363,6 @@ class TreeUnpickler(reader: TastyReader,
               readTypeRef() match {
                 case binder: LambdaType => binder.paramRefs(readNat())
               }
-            case HOLE =>
-              readHole(end, isType = true).tpe
           }
         assert(currentAddr == end, s"$start $currentAddr $end ${astTagToString(tag)}")
         result
@@ -1166,17 +1174,32 @@ class TreeUnpickler(reader: TastyReader,
       setPos(start, tree)
     }
 
-    def readTpt()(implicit ctx: Context): Tree =
-      if (nextByte == SHAREDterm) {
-        readByte()
-        forkAt(readAddr()).readTpt()
-      }
-      else if (isTypeTreeTag(nextByte)) readTerm()
-      else {
-        val start = currentAddr
-        val tp = readType()
-        if (tp.exists) setPos(start, TypeTree(tp)) else EmptyTree
+    def readTpt()(implicit ctx: Context): Tree = {
+      nextByte match {
+        case SHAREDterm =>
+          readByte()
+          forkAt(readAddr()).readTpt()
+        case BLOCK =>
+          readByte()
+          val end = readEnd()
+          val typeReader = fork
+          skipTree()
+          val aliases = readStats(ctx.owner, end)
+          val tpt = typeReader.readTpt()
+          Block(aliases, tpt)
+        case HOLE =>
+          readByte()
+          val end = readEnd()
+          readHole(end, isType = true)
+        case _ =>
+          if (isTypeTreeTag(nextByte)) readTerm()
+          else {
+            val start = currentAddr
+            val tp = readType()
+            if (tp.exists) setPos(start, TypeTree(tp)) else EmptyTree
+          }
       }
+    }
 
     def readCases(end: Addr)(implicit ctx: Context): List[CaseDef] =
       collectWhile((nextUnsharedTag == CASEDEF) && currentAddr != end) {

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

@@ -39,7 +39,9 @@ class TreeCleaner extends tpd.TreeMap {
         }
         expr1 match {
           case Block(stats3, expr3) => Block(flatStats ::: stats3, expr3)
-          case expr3 => Block(flatStats, expr3)
+          case expr3 =>
+            if (flatStats.isEmpty) expr3
+            else Block(flatStats, expr3)
         }
       case tree1: TypeTree => TypeTree(tree1.tpe.subst(aliasesSyms, aliasesTypes))
       case tree1: Ident => aliases.get(tree1.symbol).getOrElse(tree1)

compiler/src/dotty/tools/dotc/tastyreflect/TypeOrBoundsTreesOpsImpl.scala

@@ -120,6 +120,13 @@ trait TypeOrBoundsTreesOpsImpl extends scala.tasty.reflect.TypeOrBoundsTreeOps w
         case _ => None
       }
     }
+
+    object Block extends BlockExtractor {
+      def unapply(x: TypeTree)(implicit ctx: Context): Option[(List[TypeDef], TypeTree)] = x match {
+        case x: tpd.Block => Some((x.stats.map { case alias: TypeDef => alias }, x.expr))
+        case _ => None
+      }
+    }
   }
 
   // ----- TypeBoundsTrees ------------------------------------------------

library/src/scala/tasty/reflect/TypeOrBoundsTreeOps.scala

@@ -91,6 +91,11 @@ trait TypeOrBoundsTreeOps extends TastyCore {
     abstract class BindExtractor{
       def unapply(typeOrBoundsTree: TypeOrBoundsTree)(implicit ctx: Context): Option[(String, TypeBoundsTree)]
     }
+
+    val Block: BlockExtractor
+    abstract class BlockExtractor{
+      def unapply(typeOrBoundsTree: TypeOrBoundsTree)(implicit ctx: Context): Option[(List[TypeDef], TypeTree)]
+    }
   }
 
   // ----- TypeBoundsTrees ------------------------------------------------

library/src/scala/tasty/util/ShowExtractors.scala

@@ -116,9 +116,11 @@ class ShowExtractors[T <: Tasty with Singleton](tasty0: T) extends Show[T](tasty
       case TypeTree.Annotated(arg, annot) =>
         this += "TypeTree.Annotated(" += arg += ", " += annot += ")"
       case TypeTree.TypeLambdaTree(tparams, body) =>
-        this += "LambdaTypeTree(" ++= tparams += ", " += body += ")"
+        this += "TypeTree.LambdaTypeTree(" ++= tparams += ", " += body += ")"
       case TypeTree.Bind(name, bounds) =>
-        this += "Bind(" += name += ", " += bounds += ")"
+        this += "TypeTree.Bind(" += name += ", " += bounds += ")"
+      case TypeTree.Block(aliases, tpt) =>
+        this += "TypeTree.Block(" ++= aliases += ", " += tpt += ")"
       case TypeBoundsTree(lo, hi) =>
         this += "TypeBoundsTree(" += lo += ", " += hi += ")"
       case SyntheticBounds() =>

library/src/scala/tasty/util/ShowSourceCode.scala

@@ -816,6 +816,12 @@ class ShowSourceCode[T <: Tasty with Singleton](tasty0: T) extends Show[T](tasty
       case TypeTree.Bind(name, _) =>
         this += highlightTypeDef(name, color)
 
+      case TypeTree.Block(aliases, tpt) =>
+        inBlock {
+          printTrees(aliases, lineBreak())
+          printTypeTree(tpt)
+        }
+
       case _ =>
         throw new MatchError(tree.show)
 

tests/run-with-compiler/i5247.check

@@ -0,0 +1 @@
+null.asInstanceOf[lang.Object]

tests/run-with-compiler/i5247.scala

@@ -0,0 +1,11 @@
+import scala.quoted._
+object Test {
+  def main(args: Array[String]): Unit = {
+    implicit val toolbox: scala.quoted.Toolbox = scala.quoted.Toolbox.make
+    println(foo[Object].show)
+  }
+  def foo[H : Type]: Expr[H] = {
+    val t = '[H]
+    '{ null.asInstanceOf[~t] }
+  }
+}

tests/run-with-compiler/quote-owners-2.check

@@ -2,7 +2,7 @@
 {
   def ff: scala.Int = {
     val a: immutable.List[scala.Int] = {
-      type T = immutable.List[scala.Int]
+      type T = scala.List[scala.Int]
       val b: T = scala.Nil.::[scala.Int](3)
       (b: collection.immutable.List[scala.Int])
     }