Check that the quotes represented as trees did not escape

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

@@ -46,7 +46,10 @@ object PickledQuotes {
         case value: Class[_] => ref(defn.Predef_classOf).appliedToType(classToType(value))
         case value => Literal(Constant(value))
       }
-    case expr: TastyTreeExpr[Tree] @unchecked => healOwner(expr.tree)
+    case expr: TastyTreeExpr[Tree] @unchecked =>
+      if (contextId != expr.ctxId)
+        throw new scala.quoted.QuoteError("Scope extrusion!")
+      healOwner(expr.tree)
     case expr: FunctionAppliedTo[_, _] =>
       functionAppliedTo(quotedExprToTree(expr.f), quotedExprToTree(expr.x))
   }
@@ -187,4 +190,12 @@ object PickledQuotes {
       case _ => tree
     }
   }
+
+  /** Id of the current compilation (macros) or Expr[_] run */
+  def contextId(implicit ctx: Context): Int = {
+    def root(ctx: Context): Context =
+      if (ctx.outer != NoContext) root(ctx.outer) else ctx
+    root(ctx).hashCode
+  }
+
 }

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

@@ -1230,7 +1230,7 @@ class TreeUnpickler(reader: TastyReader,
       val args = until(end)(readTerm())
       val splice = splices(idx)
       def wrap(arg: Tree) =
-        if (arg.isTerm) new TastyTreeExpr(arg)
+        if (arg.isTerm) new TastyTreeExpr(arg, PickledQuotes.contextId)
         else new TreeType(arg)
       val reifiedArgs = args.map(wrap)
       if (isType) {

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

@@ -19,7 +19,7 @@ trait QuotedOpsImpl extends scala.tasty.reflect.QuotedOps with CoreImpl {
 
     def reify[T: scala.quoted.Type](implicit ctx: Context): scala.quoted.Expr[T] = {
       typecheck(ctx)
-      new scala.quoted.Exprs.TastyTreeExpr(term).asInstanceOf[scala.quoted.Expr[T]]
+      new scala.quoted.Exprs.TastyTreeExpr(term, PickledQuotes.contextId).asInstanceOf[scala.quoted.Expr[T]]
     }
 
     private def typecheck[T: scala.quoted.Type](ctx: Context): Unit = {

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

@@ -95,7 +95,7 @@ object Splicer {
     }
 
     protected def interpretQuote(tree: Tree)(implicit env: Env): Object =
-      new scala.quoted.Exprs.TastyTreeExpr(tree)
+      new scala.quoted.Exprs.TastyTreeExpr(tree, PickledQuotes.contextId)
 
     protected def interpretTypeQuote(tree: Tree)(implicit env: Env): Object =
       new scala.quoted.Types.TreeType(tree)

library/src/scala/quoted/Expr.scala

@@ -49,7 +49,7 @@ object Exprs {
    *
    *  May contain references to code defined outside this TastyTreeExpr instance.
    */
-  final class TastyTreeExpr[Tree](val tree: Tree) extends quoted.Expr[Any] {
+  final class TastyTreeExpr[Tree](val tree: Tree, val ctxId: Int) extends quoted.Expr[Any] {
     override def toString: String = s"Expr(<tasty tree>)"
   }