Merge pull request #3883 from dotty-staging/clean-quote-implementations

 Seal quoted.Expr and quoted.Type

Author: nicolasstucki

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

@@ -7,11 +7,13 @@ import dotty.tools.dotc.core.Constants.Constant
 import dotty.tools.dotc.core.Contexts._
 import dotty.tools.dotc.core.Decorators._
 import dotty.tools.dotc.core.Flags._
-import dotty.tools.dotc.core.NameKinds
 import dotty.tools.dotc.core.StdNames._
+import dotty.tools.dotc.core.NameKinds
 import dotty.tools.dotc.core.Symbols._
 import dotty.tools.dotc.core.tasty.{TastyPickler, TastyPrinter, TastyString}
-import dotty.tools.dotc.interpreter.RawQuoted
+
+import scala.quoted.Types._
+import scala.quoted.Exprs._
 
 import scala.reflect.ClassTag
 
@@ -29,27 +31,37 @@ object PickledQuotes {
   }
 
   /** Transform the expression into its fully spliced Tree */
-  def quotedToTree(expr: quoted.Quoted)(implicit ctx: Context): Tree = expr match {
-    case expr: quoted.TastyQuoted =>
-      unpickleQuote(expr)
-    case expr: quoted.Liftable.ConstantExpr[_] =>
-      Literal(Constant(expr.value))
-    case expr: quoted.Expr.FunctionAppliedTo[_, _] =>
-      functionAppliedTo(quotedToTree(expr.f), quotedToTree(expr.x))
-    case expr: quoted.Type.TaggedPrimitive[_] =>
-      classTagToTypeTree(expr.ct)
-    case expr: RawQuoted =>
-      expr.tree
+  def quotedExprToTree(expr: quoted.Expr[_])(implicit ctx: Context): Tree = expr match {
+    case expr: TastyExpr[_] => unpickleExpr(expr)
+    case expr: ValueExpr[_] => Literal(Constant(expr.value))
+    case expr: TreeExpr[Tree] @unchecked => expr.tree
+    case expr: FunctionAppliedTo[_, _] =>
+      functionAppliedTo(quotedExprToTree(expr.f), quotedExprToTree(expr.x))
+  }
+
+  /** Transform the expression into its fully spliced TypeTree */
+  def quotedTypeToTree(expr: quoted.Type[_])(implicit ctx: Context): Tree = expr match {
+    case expr: TastyType[_] => unpickleType(expr)
+    case expr: TaggedType[_] => classTagToTypeTree(expr.ct)
+    case expr: TreeType[Tree] @unchecked => expr.tree
   }
 
-  /** Unpickle the tree contained in the TastyQuoted */
-  private def unpickleQuote(expr: quoted.TastyQuoted)(implicit ctx: Context): Tree = {
+  /** Unpickle the tree contained in the TastyExpr */
+  private def unpickleExpr(expr: TastyExpr[_])(implicit ctx: Context): Tree = {
     val tastyBytes = TastyString.unpickle(expr.tasty)
     val unpickled = unpickle(tastyBytes, expr.args)
+    unpickled match {
+      case PackageDef(_, (vdef: ValDef) :: Nil) => vdef.rhs
+    }
+  }
+
+  /** Unpickle the tree contained in the TastyType */
+  private def unpickleType(ttpe: TastyType[_])(implicit ctx: Context): Tree = {
+    val tastyBytes = TastyString.unpickle(ttpe.tasty)
+    val unpickled = unpickle(tastyBytes, ttpe.args)
     unpickled match {
       case PackageDef(_, (vdef: ValDef) :: Nil) =>
-        if (vdef.name == "$quote".toTermName) vdef.rhs
-        else vdef.rhs.asInstanceOf[TypeApply].args.head
+        vdef.rhs.asInstanceOf[TypeApply].args.head
     }
   }
 

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

@@ -20,8 +20,9 @@ import config.Printers.pickling
 import typer.Checking
 import config.Config
 import dotty.tools.dotc.core.quoted.PickledQuotes
-import dotty.tools.dotc.interpreter.RawQuoted
 import scala.quoted
+import scala.quoted.Types.TreeType
+import scala.quoted.Exprs.TreeExpr
 
 /** Unpickler for typed trees
  *  @param reader          the reader from which to unpickle
@@ -296,7 +297,7 @@ class TreeUnpickler(reader: TastyReader,
             case ENUMconst =>
               ConstantType(Constant(readTermRef().termSymbol))
             case HOLE =>
-              readHole(end).tpe
+              readHole(end, isType = true).tpe
           }
         assert(currentAddr == end, s"$start $currentAddr $end ${astTagToString(tag)}")
         result
@@ -1076,7 +1077,7 @@ class TreeUnpickler(reader: TastyReader,
               val hi = if (currentAddr == end) lo else readTpt()
               TypeBoundsTree(lo, hi)
             case HOLE =>
-              readHole(end)
+              readHole(end, isType = false)
             case _ =>
               readPathTerm()
           }
@@ -1127,14 +1128,23 @@ class TreeUnpickler(reader: TastyReader,
       new LazyReader(localReader, op)
     }
 
-    def readHole(end: Addr)(implicit ctx: Context): Tree = {
+    def readHole(end: Addr, isType: Boolean)(implicit ctx: Context): Tree = {
       val idx = readNat()
       val args = until(end)(readTerm())
       val splice = splices(idx)
-      val quotedType =
-        if (args.isEmpty) splice.asInstanceOf[quoted.Quoted]
-        else splice.asInstanceOf[Seq[Any] => quoted.Quoted](args.map(RawQuoted.apply))
-      PickledQuotes.quotedToTree(quotedType)
+
+      if (isType) {
+        val quotedType =
+          if (args.isEmpty) splice.asInstanceOf[quoted.Type[_]]
+          else splice.asInstanceOf[Seq[Any] => quoted.Type[_]](args.map(tree => new TreeType(tree)))
+        PickledQuotes.quotedTypeToTree(quotedType)
+      } else {
+        val quotedExpr =
+          if (args.isEmpty) splice.asInstanceOf[quoted.Expr[_]]
+          else splice.asInstanceOf[Seq[Any] => quoted.Expr[_]](args.map(tree => new TreeExpr(tree)))
+        PickledQuotes.quotedExprToTree(quotedExpr)
+      }
+
     }
 
 // ------ Setting positions ------------------------------------------------

compiler/src/dotty/tools/dotc/interpreter/Interpreter.scala

@@ -72,7 +72,9 @@ class Interpreter(implicit ctx: Context) {
     implicit val pos: Position = tree.pos
 
     tree match {
-      case Quoted(quotedTree) => RawQuoted(quotedTree)
+      case Quoted(quotedTree) =>
+        if (tree.isTerm) new scala.quoted.Exprs.TreeExpr(quotedTree)
+        else new scala.quoted.Types.TreeType(quotedTree)
 
       case Literal(Constant(c)) => c.asInstanceOf[Object]
 

compiler/src/dotty/tools/dotc/interpreter/RawQuoted.scala

@@ -61,7 +61,7 @@ class ExprCompiler(directory: AbstractFile) extends Compiler {
         case exprUnit: ExprCompilationUnit =>
           val tree =
             if (putInClass) inClass(exprUnit.expr)
-            else PickledQuotes.quotedToTree(exprUnit.expr)
+            else PickledQuotes.quotedExprToTree(exprUnit.expr)
           val source = new SourceFile("", Seq())
           CompilationUnit.mkCompilationUnit(source, tree, forceTrees = true)
       }
@@ -80,7 +80,7 @@ class ExprCompiler(directory: AbstractFile) extends Compiler {
       cls.enter(ctx.newDefaultConstructor(cls), EmptyScope)
       val meth = ctx.newSymbol(cls, nme.apply, Method, ExprType(defn.AnyType), coord = pos).entered
 
-      val quoted = PickledQuotes.quotedToTree(expr)(ctx.withOwner(meth))
+      val quoted = PickledQuotes.quotedExprToTree(expr)(ctx.withOwner(meth))
 
       val run = DefDef(meth, quoted)
       val classTree = ClassDef(cls, DefDef(cls.primaryConstructor.asTerm), run :: Nil)

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

@@ -6,8 +6,8 @@ import dotty.tools.dotc.core.Constants._
 import dotty.tools.dotc.printing.RefinedPrinter
 
 import scala.quoted.Expr
-import scala.quoted.Liftable.ConstantExpr
 import scala.runtime.BoxedUnit
+import scala.quoted.Exprs.ValueExpr
 import scala.runtime.quoted._
 
 /** Default runners for quoted expressions */
@@ -31,20 +31,20 @@ object Runners {
         case _ => None
       }
       expr match {
-        case expr: ConstantExpr[T] => Some(expr.value)
+        case expr: ValueExpr[T] => Some(expr.value)
         case _ => new QuoteDriver().withTree(expr, (tree, _) => toConstantOpt(tree), Settings.run())
       }
     }
 
   }
 
   def run[T](expr: Expr[T], settings: Settings[Run]): T = expr match {
-    case expr: ConstantExpr[T] => expr.value
+    case expr: ValueExpr[T] => expr.value
     case _ => new QuoteDriver().run(expr, settings)
   }
 
   def show[T](expr: Expr[T], settings: Settings[Show]): String = expr match {
-    case expr: ConstantExpr[T] =>
+    case expr: ValueExpr[T] =>
       implicit val ctx = new QuoteDriver().initCtx
       if (settings.compilerArgs.contains("-color:never"))
         ctx.settings.color.update("never")

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

@@ -24,7 +24,7 @@ object Splicer {
   /** Splice the Tree for a Quoted expression which is constructed via a reflective call to the given method */
   private def reflectiveSplice(tree: Tree)(implicit ctx: Context): Tree = {
     val interpreter = new Interpreter
-    interpreter.interpretTree[scala.quoted.Expr[_]](tree).map(PickledQuotes.quotedToTree(_)).getOrElse(tree)
+    interpreter.interpretTree[scala.quoted.Expr[_]](tree).map(PickledQuotes.quotedExprToTree).getOrElse(tree)
   }
 
 }

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

@@ -1294,4 +1294,16 @@ class ErrorMessagesTests extends ErrorMessagesTest {
       val JavaSymbolIsNotAValue(symbol) = messages.head
       assertEquals(symbol.show, "package p")
     }
+
+  @Test def i3187 =
+    checkMessagesAfter("genBCode") {
+      """
+        |package scala
+        |object collection
+      """.stripMargin
+    }.expect { (itcx, messages) =>
+      implicit val ctx: Context = itcx
+
+      assert(ctx.reporter.hasErrors)
+    }
 }

compiler/test/dotty/tools/dotc/reporting/ErrorMessagesTests.scala

@@ -445,7 +445,7 @@ to be executed at a later stage. To run that code, there is another method
 in class `Expr` called `run`. Note that `~` and `run` both map from `Expr[T]`
 to `T` but only `~` is subject to the PCP, whereas `run` is just a normal method.
 
-    abstract class Expr[T] {
+    sealed abstract class Expr[T] {
       def unary_~: T
       def run(implicit runner: Runner[T]): T       // run staged code
       def show(implicit runner: Runner[T]): String // show staged code

docs/docs/reference/principled-meta-programming.md

@@ -1,8 +1,9 @@
 package scala.quoted
 
 import scala.runtime.quoted.Runner
+import scala.runtime.quoted.Unpickler.Pickled
 
-abstract class Expr[T] extends Quoted {
+sealed abstract class Expr[T] {
   final def unary_~ : T = throw new Error("~ should have been compiled away")
   final def run(implicit runner: Runner[T]): T = runner.run(this)
   final def show(implicit runner: Runner[T]): String = runner.show(this)
@@ -13,8 +14,34 @@ object Expr {
     ev.toExpr(x)
 
   implicit class AsFunction[T, U](private val f: Expr[T => U]) extends AnyVal {
-    def apply(x: Expr[T]): Expr[U] = new FunctionAppliedTo[T, U](f, x)
+    def apply(x: Expr[T]): Expr[U] = new Exprs.FunctionAppliedTo[T, U](f, x)
   }
 
-  final class FunctionAppliedTo[T, U] private[Expr](val f: Expr[T => U], val x: Expr[T]) extends Expr[U]
+}
+
+/** All implementations of Expr[T].
+ *  These should never be used directly.
+ */
+object Exprs {
+  /** An Expr backed by a pickled TASTY tree */
+  final class TastyExpr[T](val tasty: Pickled, val args: Seq[Any]) extends Expr[T] {
+    override def toString(): String = s"Expr(<pickled>)"
+  }
+
+  /** An Expr backed by a value.
+   *  Values can only be of type Boolean, Byte, Short, Char, Int, Long, Float, Double, Unit, String or Null.
+   */
+  final class ValueExpr[T](val value: T) extends Expr[T] {
+    override def toString: String = s"Expr($value)"
+  }
+
+  /** An Expr backed by a tree. Only the current compiler trees are allowed. */
+  final class TreeExpr[Tree](val tree: Tree) extends quoted.Expr[Any] {
+    override def toString: String = s"Expr(<raw>)"
+  }
+
+  /** An Expr representing `'{(~f).apply(~x)}` but it is beta-reduced when the closure is known */
+  final class FunctionAppliedTo[T, U](val f: Expr[T => U], val x: Expr[T]) extends Expr[U] {
+    override def toString: String = s"Expr($f <applied to> $x)"
+  }
 }

library/src/scala/quoted/Expr.scala

@@ -1,5 +1,7 @@
 package scala.quoted
 
+import scala.quoted.Exprs.ValueExpr
+
 /** A typeclass for types that can be turned to `quoted.Expr[T]`
  *  without going through an explicit `'(...)` operation.
  */
@@ -18,19 +20,15 @@ object Liftable {
     def toExpr(implicit liftable: Liftable[T]): Expr[T] = liftable.toExpr(x)
   }
 
-  final class ConstantExpr[T] private[Liftable](val value: T) extends Expr[T] {
-    override def toString: String = s"Expr($value)"
-  }
-
-  implicit def UnitIsLiftable: Liftable[Unit] = (x: Unit) => new ConstantExpr(x)
-  implicit def BooleanIsLiftable: Liftable[Boolean] = (x: Boolean) => new ConstantExpr(x)
-  implicit def ByteLiftable: Liftable[Byte] = (x: Byte) => new ConstantExpr(x)
-  implicit def CharIsLiftable: Liftable[Char] = (x: Char) => new ConstantExpr(x)
-  implicit def ShortIsLiftable: Liftable[Short] = (x: Short) => new ConstantExpr(x)
-  implicit def IntIsLiftable: Liftable[Int] = (x: Int) => new ConstantExpr(x)
-  implicit def LongIsLiftable: Liftable[Long] = (x: Long) => new ConstantExpr(x)
-  implicit def FloatIsLiftable: Liftable[Float] = (x: Float) => new ConstantExpr(x)
-  implicit def DoubleIsLiftable: Liftable[Double] = (x: Double) => new ConstantExpr(x)
+  implicit def UnitIsLiftable: Liftable[Unit] = (x: Unit) => new ValueExpr(x)
+  implicit def BooleanIsLiftable: Liftable[Boolean] = (x: Boolean) => new ValueExpr(x)
+  implicit def ByteLiftable: Liftable[Byte] = (x: Byte) => new ValueExpr(x)
+  implicit def CharIsLiftable: Liftable[Char] = (x: Char) => new ValueExpr(x)
+  implicit def ShortIsLiftable: Liftable[Short] = (x: Short) => new ValueExpr(x)
+  implicit def IntIsLiftable: Liftable[Int] = (x: Int) => new ValueExpr(x)
+  implicit def LongIsLiftable: Liftable[Long] = (x: Long) => new ValueExpr(x)
+  implicit def FloatIsLiftable: Liftable[Float] = (x: Float) => new ValueExpr(x)
+  implicit def DoubleIsLiftable: Liftable[Double] = (x: Double) => new ValueExpr(x)
 
-  implicit def StringIsLiftable: Liftable[String] = (x: String) => new ConstantExpr(x)
+  implicit def StringIsLiftable: Liftable[String] = (x: String) => new ValueExpr(x)
 }