Merge pull request #4576 from dotty-staging/disable-macro-quote-run

Do not allow running Expr that came as macro arguments

Author: nicolasstucki

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

@@ -23,19 +23,6 @@ object PickledQuotes {
 
   /** Pickle the tree of the quoted.Expr */
   def pickleExpr(tree: Tree)(implicit ctx: Context): scala.quoted.Expr[Any] = {
-    // Check that there are no free variables
-    new TreeTraverser {
-      private val definedHere = scala.collection.mutable.Set.empty[Symbol]
-      def traverse(tree: tpd.Tree)(implicit ctx: Context): Unit = tree match {
-        case tree: Ident if tree.symbol.exists && !definedHere(tree.symbol) =>
-          throw new scala.quoted.FreeVariableError(tree.name.toString)
-        case tree: DefTree =>
-          definedHere += tree.symbol
-          traverseChildren(tree)
-        case _ =>
-          traverseChildren(tree)
-      }
-    }.traverse(tree)
     val pickled = pickleQuote(tree)
     scala.runtime.quoted.Unpickler.unpickleExpr(pickled, Nil)
   }
@@ -64,7 +51,7 @@ object PickledQuotes {
         case value: Class[_] => ref(defn.Predef_classOf).appliedToType(classToType(value))
         case value => Literal(Constant(value))
       }
-    case expr: TreeExpr[Tree] @unchecked => expr.tree
+    case expr: TastyTreeExpr[Tree] @unchecked => expr.tree
     case expr: FunctionAppliedTo[_, _] =>
       functionAppliedTo(quotedExprToTree(expr.f), quotedExprToTree(expr.x))
   }

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

@@ -22,7 +22,7 @@ import config.Config
 import core.quoted.PickledQuotes
 import scala.quoted
 import scala.quoted.Types.TreeType
-import scala.quoted.Exprs.TreeExpr
+import scala.quoted.Exprs.TastyTreeExpr
 
 /** Unpickler for typed trees
  *  @param reader          the reader from which to unpickle
@@ -1150,7 +1150,7 @@ class TreeUnpickler(reader: TastyReader,
       val args = until(end)(readTerm())
       val splice = splices(idx)
       def wrap(arg: Tree) =
-        if (arg.isTerm) new TreeExpr(arg, PickledQuotes.pickleExpr(arg))
+        if (arg.isTerm) new TastyTreeExpr(arg)
         else new TreeType(arg)
       val reifiedArgs = args.map(wrap)
       if (isType) {

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

@@ -6,7 +6,7 @@ import dotty.tools.dotc.printing.RefinedPrinter
 
 import scala.quoted.Expr
 import scala.runtime.BoxedUnit
-import scala.quoted.Exprs.{LiftedExpr, TreeExpr}
+import scala.quoted.Exprs.{LiftedExpr, TastyTreeExpr}
 import scala.runtime.quoted._
 
 /** Default runners for quoted expressions */
@@ -24,8 +24,8 @@ object Toolbox {
     def run(expr: Expr[T]): T = expr match {
       case expr: LiftedExpr[T] =>
         expr.value
-      case expr: TreeExpr[Tree] @unchecked =>
-        new QuoteDriver().run(expr.pickled, runSettings)
+      case expr: TastyTreeExpr[Tree] @unchecked =>
+        throw new Exception("Cannot call `Expr.run` on an `Expr` that comes from an inline macro argument.")
       case _ =>
         new QuoteDriver().run(expr, runSettings)
     }

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

@@ -68,7 +68,7 @@ object Splicer {
             assert(!tp.hasAnnotation(defn.InlineParamAnnot))
             // Replace argument by its binding
             val arg1 = bindMap.getOrElse(arg, arg)
-            new scala.quoted.Exprs.TreeExpr(arg1, PickledQuotes.pickleExpr(arg1))
+            new scala.quoted.Exprs.TastyTreeExpr(arg1)
         }
         args1 ::: liftArgs(tp.resType, args.tail)
       case tp: PolyType =>

library/src/scala/quoted/Expr.scala

@@ -33,7 +33,7 @@ object Expr {
 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>)"
+    override def toString: String = s"Expr(<pickled tasty>)"
   }
 
   /** An Expr backed by a lifted value.
@@ -48,11 +48,10 @@ object Exprs {
    *  These expressions are used for arguments of inline macros. They contain and actual tree
    *  from the program that is being expanded by the macro.
    *
-   *  May contain references to code defined outside this Expr instance.
+   *  May contain references to code defined outside this TastyTreeExpr instance.
    */
-  final class TreeExpr[Tree](val tree: Tree, pickle: => Expr[_]) extends quoted.Expr[Any] {
-    def pickled[T]: Expr[T] = pickle.asInstanceOf[Expr[T]]
-    override def toString: String = s"Expr(<raw>)"
+  final class TastyTreeExpr[Tree](val tree: Tree) extends quoted.Expr[Any] {
+    override def toString: String = s"Expr(<tasty tree>)"
   }
 
   /** An Expr representing `'{(~f).apply(~x)}` but it is beta-reduced when the closure is known */

library/src/scala/quoted/FreeVariableError.scala

@@ -1,10 +1,10 @@
 import Macros._
 object Test {
   def main(args: Array[String]): Unit = {
-    println(foo(1))
-    println(foo(1  + 3))
+    println(foo(1)) // error
+    println(foo(1  + 3)) // error
     val x = 3
-    println(foo {
+    println(foo { // error
       val x = 5
       x
     })