From 2a7e9106185251b9100e96eea0b1c0e2d6f6e985 Mon Sep 17 00:00:00 2001
From: Nicolas Stucki <nicolas.stucki@gmail.com>
Date: Wed, 17 Feb 2021 14:36:34 +0100
Subject: [PATCH 1/3] Add add informative scope extrusion check

---
 .../tools/dotc/quoted/PickledQuotes.scala     | 36 ++++++-----
 .../dotty/tools/dotc/transform/Splicer.scala  | 13 ++--
 .../src/dotty/tools/dotc/typer/Inliner.scala  |  8 +--
 .../scala/quoted/runtime/impl/ExprImpl.scala  |  2 +-
 .../quoted/runtime/impl/QuotesImpl.scala      | 12 ++--
 .../quoted/runtime/impl/ScopeException.scala  | 31 ++++++++++
 .../quoted/runtime/impl/SpliceScope.scala     | 62 +++++++++++++++++++
 .../scala/quoted/runtime/impl/TypeImpl.scala  |  2 +-
 .../scala/quoted/staging/QuoteCompiler.scala  | 11 +++-
 tests/neg-macros/i8216/Macro_1.scala          | 12 ++++
 tests/neg-macros/i8216/Test_2.scala           |  8 +++
 .../neg-macros/scope-extrusion/Macro_1.scala  | 32 ++++++++++
 tests/neg-macros/scope-extrusion/Test_2.scala |  6 ++
 tests/run-macros/i8007/Macro_3.scala          |  4 +-
 .../quote-matcher-symantics-2/quoted_1.scala  | 18 +++---
 .../quote-matcher-symantics-3/quoted_1.scala  |  2 +-
 tests/run-staging/i3947.scala                 |  2 +-
 tests/run-staging/i3947b.scala                |  2 +-
 tests/run-staging/i3947b2.scala               |  2 +-
 tests/run-staging/i3947b3.scala               |  2 +-
 tests/run-staging/i3947c.scala                |  2 +-
 tests/run-staging/i3947d.scala                |  2 +-
 tests/run-staging/i3947d2.scala               |  2 +-
 tests/run-staging/i3947e.scala                |  2 +-
 tests/run-staging/i3947f.scala                |  2 +-
 tests/run-staging/i3947g.scala                |  2 +-
 tests/run-staging/i3947i.scala                |  2 +-
 tests/run-staging/i3947j.scala                |  2 +-
 tests/run-staging/quote-run-2.scala           |  2 +-
 .../quote-run-staged-interpreter.scala        |  2 +-
 tests/run-staging/staged-streams_1.scala      | 10 +--
 31 files changed, 229 insertions(+), 68 deletions(-)
 create mode 100644 compiler/src/scala/quoted/runtime/impl/SpliceScope.scala
 create mode 100644 tests/neg-macros/i8216/Macro_1.scala
 create mode 100644 tests/neg-macros/i8216/Test_2.scala
 create mode 100644 tests/neg-macros/scope-extrusion/Macro_1.scala
 create mode 100644 tests/neg-macros/scope-extrusion/Test_2.scala

diff --git a/compiler/src/dotty/tools/dotc/quoted/PickledQuotes.scala b/compiler/src/dotty/tools/dotc/quoted/PickledQuotes.scala
index 3e472ed93846..bc5e7cdc4dc1 100644
--- a/compiler/src/dotty/tools/dotc/quoted/PickledQuotes.scala
+++ b/compiler/src/dotty/tools/dotc/quoted/PickledQuotes.scala
@@ -42,6 +42,7 @@ object PickledQuotes {
   def quotedExprToTree[T](expr: quoted.Expr[T])(using Context): Tree = {
     val expr1 = expr.asInstanceOf[ExprImpl]
     expr1.checkScopeId(QuotesImpl.scopeId)
+    ScopeException.checkInCorrectScope(expr1.scope, SpliceScope.getCurrent, expr1.tree, "Expr")
     changeOwnerOfTree(expr1.tree, ctx.owner)
   }
 
@@ -49,6 +50,7 @@ object PickledQuotes {
   def quotedTypeToTree(tpe: quoted.Type[?])(using Context): Tree = {
     val tpe1 = tpe.asInstanceOf[TypeImpl]
     tpe1.checkScopeId(QuotesImpl.scopeId)
+    ScopeException.checkInCorrectScope(tpe1.scope, SpliceScope.getCurrent, tpe1.typeTree, "Type")
     changeOwnerOfTree(tpe1.typeTree, ctx.owner)
   }
 
@@ -73,23 +75,25 @@ object PickledQuotes {
     val evaluateHoles = new TreeMap {
       override def transform(tree: tpd.Tree)(using Context): tpd.Tree = tree match {
         case Hole(isTerm, idx, args) =>
-          val reifiedArgs = args.map { arg =>
-            if (arg.isTerm) (q: Quotes) ?=> new ExprImpl(arg, QuotesImpl.scopeId)
-            else new TypeImpl(arg, QuotesImpl.scopeId)
+          inContext(SpliceScope.contextWithNewSpliceScope(tree.sourcePos)) {
+            val reifiedArgs = args.map { arg =>
+              if (arg.isTerm) (q: Quotes) ?=> new ExprImpl(arg, QuotesImpl.scopeId, SpliceScope.getCurrent)
+              else new TypeImpl(arg, QuotesImpl.scopeId, SpliceScope.getCurrent)
+            }
+            if isTerm then
+              val quotedExpr = termHole(idx, reifiedArgs, 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)
+            else
+              // Replaces type holes generated by PickleQuotes (non-spliced types).
+              // These are types defined in a quote and used at the same level in a nested quote.
+              val quotedType = typeHole(idx, reifiedArgs)
+              PickledQuotes.quotedTypeToTree(quotedType)
           }
-          if isTerm then
-            val quotedExpr = termHole(idx, reifiedArgs, 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)
-          else
-            // Replaces type holes generated by PickleQuotes (non-spliced types).
-            // These are types defined in a quote and used at the same level in a nested quote.
-            val quotedType = typeHole(idx, reifiedArgs)
-            PickledQuotes.quotedTypeToTree(quotedType)
         case tree: Select =>
           // Retain selected members
           val qual = transform(tree.qualifier)
diff --git a/compiler/src/dotty/tools/dotc/transform/Splicer.scala b/compiler/src/dotty/tools/dotc/transform/Splicer.scala
index 66419c8c2006..864c06faa72c 100644
--- a/compiler/src/dotty/tools/dotc/transform/Splicer.scala
+++ b/compiler/src/dotty/tools/dotc/transform/Splicer.scala
@@ -39,16 +39,17 @@ object Splicer {
    *
    *  See: `Staging`
    */
-  def splice(tree: Tree, pos: SrcPos, classLoader: ClassLoader)(using Context): Tree = tree match {
+  def splice(tree: Tree, splicePos: SrcPos, spliceExpansionPos: SrcPos, classLoader: ClassLoader)(using Context): Tree = tree match {
     case Quoted(quotedTree) => quotedTree
     case _ =>
       val macroOwner = newSymbol(ctx.owner, nme.MACROkw, Macro | Synthetic, defn.AnyType, coord = tree.span)
       try
-        inContext(ctx.withOwner(macroOwner)) {
+        val sliceContext = SpliceScope.contextWithNewSpliceScope(splicePos.sourcePos).withOwner(macroOwner)
+        inContext(sliceContext) {
           val oldContextClassLoader = Thread.currentThread().getContextClassLoader
           Thread.currentThread().setContextClassLoader(classLoader)
           try {
-            val interpreter = new Interpreter(pos, classLoader)
+            val interpreter = new Interpreter(spliceExpansionPos, classLoader)
 
             // Some parts of the macro are evaluated during the unpickling performed in quotedExprToTree
             val interpretedExpr = interpreter.interpret[Quotes => scala.quoted.Expr[Any]](tree)
@@ -74,7 +75,7 @@ object Splicer {
                |  Caused by ${ex.getClass}: ${if (ex.getMessage == null) "" else ex.getMessage}
                |    ${ex.getStackTrace.takeWhile(_.getClassName != "dotty.tools.dotc.transform.Splicer$").drop(1).mkString("\n    ")}
              """.stripMargin
-          report.error(msg, pos)
+          report.error(msg, spliceExpansionPos)
           ref(defn.Predef_undefined).withType(ErrorType(msg))
       }
   }
@@ -325,10 +326,10 @@ object Splicer {
     }
 
     private def interpretQuote(tree: Tree)(implicit env: Env): Object =
-      new ExprImpl(Inlined(EmptyTree, Nil, QuoteUtils.changeOwnerOfTree(tree, ctx.owner)).withSpan(tree.span), QuotesImpl.scopeId)
+      new ExprImpl(Inlined(EmptyTree, Nil, QuoteUtils.changeOwnerOfTree(tree, ctx.owner)).withSpan(tree.span), QuotesImpl.scopeId, SpliceScope.getCurrent)
 
     private def interpretTypeQuote(tree: Tree)(implicit env: Env): Object =
-      new TypeImpl(QuoteUtils.changeOwnerOfTree(tree, ctx.owner), QuotesImpl.scopeId)
+      new TypeImpl(QuoteUtils.changeOwnerOfTree(tree, ctx.owner), QuotesImpl.scopeId, SpliceScope.getCurrent)
 
     private def interpretLiteral(value: Any)(implicit env: Env): Object =
       value.asInstanceOf[Object]
diff --git a/compiler/src/dotty/tools/dotc/typer/Inliner.scala b/compiler/src/dotty/tools/dotc/typer/Inliner.scala
index d89ba6128274..c130c592cd81 100644
--- a/compiler/src/dotty/tools/dotc/typer/Inliner.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Inliner.scala
@@ -1303,7 +1303,7 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(using Context) {
         case res: Apply if res.symbol == defn.QuotedRuntime_exprSplice
                         && level == 0
                         && !hasInliningErrors =>
-          val expanded = expandMacro(res.args.head, tree.span)
+          val expanded = expandMacro(res.args.head, tree.srcPos)
           typedExpr(expanded) // Inline calls and constant fold code generated by the macro
         case res =>
           inlineIfNeeded(res)
@@ -1488,7 +1488,7 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(using Context) {
     }
   }
 
-  private def expandMacro(body: Tree, span: Span)(using Context) = {
+  private def expandMacro(body: Tree, splicePos: SrcPos)(using Context) = {
     assert(level == 0)
     val inlinedFrom = enclosingInlineds.last
     val dependencies = macroDependencies(body)
@@ -1503,7 +1503,7 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(using Context) {
         ctx.compilationUnit.suspend() // this throws a SuspendException
 
     val evaluatedSplice = inContext(quoted.MacroExpansion.context(inlinedFrom)) {
-      Splicer.splice(body, inlinedFrom.srcPos, MacroClassLoader.fromContext)
+      Splicer.splice(body, splicePos, inlinedFrom.srcPos, MacroClassLoader.fromContext)
     }
     val inlinedNormailizer = new TreeMap {
       override def transform(tree: tpd.Tree)(using Context): tpd.Tree = tree match {
@@ -1513,7 +1513,7 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(using Context) {
     }
     val normalizedSplice = inlinedNormailizer.transform(evaluatedSplice)
     if (normalizedSplice.isEmpty) normalizedSplice
-    else normalizedSplice.withSpan(span)
+    else normalizedSplice.withSpan(splicePos.span)
   }
 
   /** Return the set of symbols that are referred at level -1 by the tree and defined in the current run.
diff --git a/compiler/src/scala/quoted/runtime/impl/ExprImpl.scala b/compiler/src/scala/quoted/runtime/impl/ExprImpl.scala
index 6965165dc3a2..d04cb9a160f3 100644
--- a/compiler/src/scala/quoted/runtime/impl/ExprImpl.scala
+++ b/compiler/src/scala/quoted/runtime/impl/ExprImpl.scala
@@ -10,7 +10,7 @@ import dotty.tools.dotc.ast.tpd
  *
  *  May contain references to code defined outside this Expr instance.
  */
-final class ExprImpl(val tree: tpd.Tree, val scopeId: Int) extends Expr[Any] {
+final class ExprImpl(val tree: tpd.Tree, val scopeId: Int, val scope: Scope) extends Expr[Any] {
   override def equals(that: Any): Boolean = that match {
     case that: ExprImpl =>
       // Expr are wrappers around trees, therefore they are equals if their trees are equal.
diff --git a/compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala b/compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala
index 746ea78e0ba9..0e70e9ea4c75 100644
--- a/compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala
+++ b/compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala
@@ -105,7 +105,7 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
             case _ => false
         def asExpr: scala.quoted.Expr[Any] =
           if self.isExpr then
-            new ExprImpl(self, QuotesImpl.this.hashCode)
+            new ExprImpl(self, QuotesImpl.this.hashCode, SpliceScope.getCurrent)
           else self match
             case TermTypeTest(self) => throw new Exception("Expected an expression. This is a partially applied Term. Try eta-expanding the term first.")
             case _ => throw new Exception("Expected a Term but was: " + self)
@@ -372,11 +372,11 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
     given TermMethods: TermMethods with
       extension (self: Term)
         def seal: scala.quoted.Expr[Any] =
-          if self.isExpr then new ExprImpl(self, QuotesImpl.this.hashCode)
+          if self.isExpr then new ExprImpl(self, QuotesImpl.this.hashCode, SpliceScope.getCurrent)
           else throw new Exception("Cannot seal a partially applied Term. Try eta-expanding the term first.")
 
         def sealOpt: Option[scala.quoted.Expr[Any]] =
-          if self.isExpr then Some(new ExprImpl(self, QuotesImpl.this.hashCode))
+          if self.isExpr then Some(new ExprImpl(self, QuotesImpl.this.hashCode, SpliceScope.getCurrent))
           else None
 
         def tpe: TypeRepr = self.tpe
@@ -1666,7 +1666,7 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
         def seal: scala.quoted.Type[_] = self.asType
 
         def asType: scala.quoted.Type[?] =
-          new TypeImpl(Inferred(self), QuotesImpl.this.hashCode)
+          new TypeImpl(Inferred(self), QuotesImpl.this.hashCode, SpliceScope.getCurrent)
 
         def =:=(that: TypeRepr): Boolean = self =:= that
         def <:<(that: TypeRepr): Boolean = self <:< that
@@ -2877,11 +2877,11 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
 
   def unpickleExpr[T](pickled: String | List[String], typeHole: (Int, Seq[Any]) => scala.quoted.Type[?], termHole: (Int, Seq[Any], scala.quoted.Quotes) => scala.quoted.Expr[?]): scala.quoted.Expr[T] =
     val tree = PickledQuotes.unpickleTerm(pickled, typeHole, termHole)
-    new ExprImpl(tree, hash).asInstanceOf[scala.quoted.Expr[T]]
+    new ExprImpl(tree, hash, SpliceScope.getCurrent).asInstanceOf[scala.quoted.Expr[T]]
 
   def unpickleType[T <: AnyKind](pickled: String | List[String], typeHole: (Int, Seq[Any]) => scala.quoted.Type[?], termHole: (Int, Seq[Any], scala.quoted.Quotes) => scala.quoted.Expr[?]): scala.quoted.Type[T] =
     val tree = PickledQuotes.unpickleTypeTree(pickled, typeHole, termHole)
-    new TypeImpl(tree, hash).asInstanceOf[scala.quoted.Type[T]]
+    new TypeImpl(tree, hash, SpliceScope.getCurrent).asInstanceOf[scala.quoted.Type[T]]
 
   object ExprMatch extends ExprMatchModule:
     def unapply[TypeBindings <: Tuple, Tup <: Tuple](scrutinee: scala.quoted.Expr[Any])(using pattern: scala.quoted.Expr[Any]): Option[Tup] =
diff --git a/compiler/src/scala/quoted/runtime/impl/ScopeException.scala b/compiler/src/scala/quoted/runtime/impl/ScopeException.scala
index 73715ae111e5..7dc84343238e 100644
--- a/compiler/src/scala/quoted/runtime/impl/ScopeException.scala
+++ b/compiler/src/scala/quoted/runtime/impl/ScopeException.scala
@@ -1,3 +1,34 @@
 package scala.quoted.runtime.impl
 
+import dotty.tools.dotc.ast.tpd.Tree
+import dotty.tools.dotc.core.Contexts._
+
 class ScopeException(msg: String) extends Exception(msg)
+
+object ScopeException:
+  def checkInCorrectScope(scope: Scope, currentScope: Scope, tree: Tree, kind: String)(using Context): Unit =
+    val yCheck = ctx.settings.Ycheck.value(using ctx).exists(x => x == "all" || x == "macros")
+    if yCheck && !scope.isOuterScopeOf(currentScope) then
+      throw new ScopeException(
+        if scope.atSameLocation(currentScope) then
+          s"""Type created in a splice, extruded from that splice and then used in a subsequent evaluation of that same splice.
+          |Splice: $scope
+          |$kind: ${tree.show}
+          |
+          |
+          |Splice stack:
+          |${scope.stack.mkString("\t", "\n\t", "\n")}
+          """.stripMargin
+        else
+          s"""Expression created in a splice was used outside of that splice.
+            |Created in: $scope
+            |Used in: $currentScope
+            |$kind: ${tree.show}
+            |
+            |
+            |Creation stack:
+            |${scope.stack.mkString("\t", "\n\t", "\n")}
+            |
+            |Use stack:
+            |${currentScope.stack.mkString("\t", "\n\t", "\n")}
+          """.stripMargin)
diff --git a/compiler/src/scala/quoted/runtime/impl/SpliceScope.scala b/compiler/src/scala/quoted/runtime/impl/SpliceScope.scala
new file mode 100644
index 000000000000..b44b1c2c5b80
--- /dev/null
+++ b/compiler/src/scala/quoted/runtime/impl/SpliceScope.scala
@@ -0,0 +1,62 @@
+package scala.quoted
+package runtime.impl
+
+import dotty.tools.dotc.core.Contexts._
+import dotty.tools.dotc.util.Property
+import dotty.tools.dotc.util.SourcePosition
+
+/** Unique identifier of the evaluation of a splice.
+ *
+ *  A nested splice gets a new Scope with the outer one as an owner.
+ *  This also applies for recursive splices.
+ */
+trait Scope {
+  /** Outer scope that was used to create the quote containing this splice.
+   *  NoScope if there is no scope
+   */
+  def outer: Scope = NoScope
+  /** Is this is a outer scope of the given scope */
+  def isOuterScopeOf(scope: Scope): Boolean =
+    this.eq(scope) || (scope.ne(NoScope) && isOuterScopeOf(scope.outer))
+  /** Stack of locations where scopes where evaluated */
+  def stack: List[String] =
+    this.toString :: (if outer.eq(NoScope) then Nil else outer.stack)
+  /** If the two scopes correspond to the same splice in source. */
+  def atSameLocation(scope: Scope): Boolean = false
+}
+
+/** Only used for outer scope of top level splice and staging `run` */
+object NoScope extends Scope:
+  override def outer: Scope = throw UnsupportedOperationException("NoScope.outer")
+
+class SpliceScope(val pos: SourcePosition, override val outer: Scope) extends Scope:
+
+  override def atSameLocation(scope: Scope): Boolean = scope match
+    case scope: SpliceScope => this.pos == scope.pos
+    case _ => false
+
+  override def toString =
+    if pos.exists then
+      s"${pos.source.toString}:${pos.startLine + 1} at column ${pos.startColumn + 1}"
+    else
+      "Unknown location"
+
+end SpliceScope
+
+
+object SpliceScope:
+
+  /** A key to be used in a context property that tracks current splices we are evaluating */
+  private val ScopeKey = new Property.Key[Scope]
+
+  def setSpliceScope(scope: Scope)(using Context): Context =
+    ctx.fresh.setProperty(ScopeKey, scope)
+
+  def contextWithNewSpliceScope(pos: SourcePosition)(using Context): Context =
+    ctx.fresh.setProperty(ScopeKey, new SpliceScope(pos, getCurrent))
+
+    /** Context with an incremented quotation level. */
+  def getCurrent(using Context): Scope =
+      ctx.property(ScopeKey).getOrElse(null)
+
+end SpliceScope
diff --git a/compiler/src/scala/quoted/runtime/impl/TypeImpl.scala b/compiler/src/scala/quoted/runtime/impl/TypeImpl.scala
index 58bb4af297aa..9add4060f1ee 100644
--- a/compiler/src/scala/quoted/runtime/impl/TypeImpl.scala
+++ b/compiler/src/scala/quoted/runtime/impl/TypeImpl.scala
@@ -4,7 +4,7 @@ package runtime.impl
 import dotty.tools.dotc.ast.tpd
 
 /** Quoted type (or kind) `T` backed by a tree */
-final class TypeImpl(val typeTree: tpd.Tree, val scopeId: Int) extends Type[?] {
+final class TypeImpl(val typeTree: tpd.Tree, val scopeId: Int, val scope: Scope) extends Type[?] {
   override def equals(that: Any): Boolean = that match {
     case that: TypeImpl => typeTree ==
       // TastyTreeExpr are wrappers around trees, therfore they are equals if their trees are equal.
diff --git a/staging/src/scala/quoted/staging/QuoteCompiler.scala b/staging/src/scala/quoted/staging/QuoteCompiler.scala
index bc0f346b37a8..9279e21f3166 100644
--- a/staging/src/scala/quoted/staging/QuoteCompiler.scala
+++ b/staging/src/scala/quoted/staging/QuoteCompiler.scala
@@ -18,10 +18,10 @@ import dotty.tools.dotc.quoted.PickledQuotes
 import dotty.tools.dotc.transform.Splicer.checkEscapedVariables
 import dotty.tools.dotc.transform.{Inlining, PickleQuotes}
 import dotty.tools.dotc.util.Spans.Span
-import dotty.tools.dotc.util.SourceFile
+import dotty.tools.dotc.util.{SourceFile, NoSourcePosition}
 import dotty.tools.io.{Path, VirtualFile}
 
-import scala.quoted.runtime.impl.QuotesImpl
+import scala.quoted.runtime.impl._
 
 import scala.annotation.tailrec
 import scala.concurrent.Promise
@@ -49,6 +49,10 @@ private class QuoteCompiler extends Compiler:
 
   def outputClassName: TypeName = "Generated$Code$From$Quoted".toTypeName
 
+  class RunScope extends Scope {
+    override def toString: String = "scala.quoted.staging"
+  }
+
   /** Frontend that receives a scala.quoted.Expr or scala.quoted.Type as input */
   class QuotedFrontend extends Phase:
     import tpd._
@@ -58,7 +62,8 @@ private class QuoteCompiler extends Compiler:
     override def runOn(units: List[CompilationUnit])(implicit ctx: Context): List[CompilationUnit] =
       units.flatMap {
         case exprUnit: ExprCompilationUnit =>
-          implicit val unitCtx: Context = ctx.fresh.setPhase(this.start).setCompilationUnit(exprUnit)
+          val ctx1 = ctx.fresh.setPhase(this.start).setCompilationUnit(exprUnit)
+          implicit val unitCtx: Context = SpliceScope.setSpliceScope(new RunScope)(using ctx1)
 
           val pos = Span(0)
           val assocFile = new VirtualFile("<quote>")
diff --git a/tests/neg-macros/i8216/Macro_1.scala b/tests/neg-macros/i8216/Macro_1.scala
new file mode 100644
index 000000000000..9105abd01d28
--- /dev/null
+++ b/tests/neg-macros/i8216/Macro_1.scala
@@ -0,0 +1,12 @@
+package macros
+import scala.quoted._
+
+var saved = Option.empty[Expr[Any]]
+
+def oops(c: Expr[Any])(using Quotes) = {
+  if saved.isEmpty then
+    saved = Some(c)
+    c
+  else saved.get
+}
+inline def test(c: Any) = ${oops('c)}
diff --git a/tests/neg-macros/i8216/Test_2.scala b/tests/neg-macros/i8216/Test_2.scala
new file mode 100644
index 000000000000..523017b42edf
--- /dev/null
+++ b/tests/neg-macros/i8216/Test_2.scala
@@ -0,0 +1,8 @@
+object Test {
+  class A(x: Int) {
+    macros.test(x)
+  }
+  class B(y: String) {
+    macros.test(y) // error
+  }
+}
\ No newline at end of file
diff --git a/tests/neg-macros/scope-extrusion/Macro_1.scala b/tests/neg-macros/scope-extrusion/Macro_1.scala
new file mode 100644
index 000000000000..b3cba5477863
--- /dev/null
+++ b/tests/neg-macros/scope-extrusion/Macro_1.scala
@@ -0,0 +1,32 @@
+import quoted.*
+
+inline def test1(): Int = ${ testExtrusion1 }
+private def testExtrusion1(using Quotes): Expr[Int] =
+  var extruded: Expr[Int] = null
+  '{ (x: Int) =>
+    ${
+      extruded = '{x}
+      extruded
+    }
+  }
+  extruded
+
+inline def test2(): Int = ${ testExtrusion2 }
+private def testExtrusion2(using Quotes): Expr[Int] =
+  '{ 1 +
+    ${ var extruded: Expr[Int] = null; '{ (y: Int) => ${ extruded = '{y}; extruded } }; extruded }
+  }
+
+inline def test3(): Int = ${ testExtrusion3 }
+private def testExtrusion3(using Quotes): Expr[Int] = {
+  var extruded: Expr[Int] = null
+  for i <- 1 to 3 do
+    '{ (x: Int) =>
+      ${
+        if extruded == null then
+            extruded = '{x}
+        extruded
+      }
+    }
+  extruded
+}
diff --git a/tests/neg-macros/scope-extrusion/Test_2.scala b/tests/neg-macros/scope-extrusion/Test_2.scala
new file mode 100644
index 000000000000..29badd1dc01c
--- /dev/null
+++ b/tests/neg-macros/scope-extrusion/Test_2.scala
@@ -0,0 +1,6 @@
+
+object Test_2 {
+  test1() // error
+  test2() // error
+  test3() // error
+}
diff --git a/tests/run-macros/i8007/Macro_3.scala b/tests/run-macros/i8007/Macro_3.scala
index 8a11dccb9a20..a0e52e93b618 100644
--- a/tests/run-macros/i8007/Macro_3.scala
+++ b/tests/run-macros/i8007/Macro_3.scala
@@ -40,7 +40,7 @@ object Eq {
     ev match {
       case '{ $m: Mirror.ProductOf[T] { type MirroredElemTypes = elementTypes }} =>
         val elemInstances = summonAll[elementTypes]
-        val eqProductBody: (Expr[T], Expr[T]) => Expr[Boolean] = (x, y) => {
+        def eqProductBody(x: Expr[T], y: Expr[T])(using Quotes): Expr[Boolean] = {
           elemInstances.zipWithIndex.foldLeft(Expr(true: Boolean)) {
             case (acc, (elem, index)) =>
               val e1 = '{$x.asInstanceOf[Product].productElement(${Expr(index)})}
@@ -55,7 +55,7 @@ object Eq {
 
       case '{ $m: Mirror.SumOf[T] { type MirroredElemTypes = elementTypes }} =>
         val elemInstances = summonAll[elementTypes]
-        val eqSumBody: (Expr[T], Expr[T]) => Expr[Boolean] = (x, y) => {
+        def eqSumBody(x: Expr[T], y: Expr[T])(using Quotes): Expr[Boolean] = {
           val ordx = '{ $m.ordinal($x) }
           val ordy = '{ $m.ordinal($y) }
 
diff --git a/tests/run-macros/quote-matcher-symantics-2/quoted_1.scala b/tests/run-macros/quote-matcher-symantics-2/quoted_1.scala
index 3485f40cca37..5f53fd1a7ade 100644
--- a/tests/run-macros/quote-matcher-symantics-2/quoted_1.scala
+++ b/tests/run-macros/quote-matcher-symantics-2/quoted_1.scala
@@ -19,7 +19,7 @@ object Macros {
 
   private def impl[T: Type](sym: Symantics[T], a: Expr[DSL])(using Quotes): Expr[T] = {
 
-    def lift(e: Expr[DSL])(implicit env: Map[Int, Expr[T]]): Expr[T] = e match {
+    def lift(e: Expr[DSL])(using env: Map[Int, Expr[T]])(using Quotes): Expr[T] = e match {
 
       case '{ LitDSL(${Expr(c)}) } => sym.value(c)
 
@@ -32,7 +32,7 @@ object Macros {
       case '{ val x: DSL = $value; $bodyFn(x): DSL } =>
         UnsafeExpr.open(bodyFn) { (body1, close) =>
           val (i, nEnvVar) = freshEnvVar()
-          lift(close(body1)(nEnvVar))(env + (i -> lift(value)))
+          lift(close(body1)(nEnvVar))(using env + (i -> lift(value)))
         }
 
       case '{ envVar(${Expr(i)}) } => env(i)
@@ -43,12 +43,12 @@ object Macros {
         ???
     }
 
-    def liftFun(e: Expr[DSL => DSL])(implicit env: Map[Int, Expr[T]]): Expr[T => T] = e match {
+    def liftFun(e: Expr[DSL => DSL])(using env: Map[Int, Expr[T]])(using Quotes): Expr[T => T] = e match {
       case '{ (x: DSL) => $bodyFn(x): DSL } =>
         sym.lam((y: Expr[T]) =>
           UnsafeExpr.open(bodyFn) { (body1, close) =>
             val (i, nEnvVar) = freshEnvVar()
-            lift(close(body1)(nEnvVar))(env + (i -> y))
+            lift(close(body1)(nEnvVar))(using env + (i -> y))
           }
         )
       case _ =>
@@ -57,7 +57,7 @@ object Macros {
         ???
     }
 
-    lift(a)(Map.empty)
+    lift(a)(using Map.empty)
   }
 
 }
@@ -112,7 +112,7 @@ trait Symantics[Num] {
   def plus(x: Expr[Num], y: Expr[Num])(using Quotes): Expr[Num]
   def times(x: Expr[Num], y: Expr[Num])(using Quotes): Expr[Num]
   def app(f: Expr[Num => Num], x: Expr[Num])(using Quotes): Expr[Num]
-  def lam(body: Expr[Num] => Expr[Num])(using Quotes): Expr[Num => Num]
+  def lam(body: Quotes ?=> Expr[Num] => Expr[Num])(using Quotes): Expr[Num => Num]
 }
 
 object StringNum extends Symantics[String] {
@@ -120,7 +120,7 @@ object StringNum extends Symantics[String] {
   def plus(x: Expr[String], y: Expr[String])(using Quotes): Expr[String] = '{ s"${$x} + ${$y}" } // '{ x + " + " + y }
   def times(x: Expr[String], y: Expr[String])(using Quotes): Expr[String] = '{ s"${$x} * ${$y}" }
   def app(f: Expr[String => String], x: Expr[String])(using Quotes): Expr[String] = Expr.betaReduce('{ $f($x) })
-  def lam(body: Expr[String] => Expr[String])(using Quotes): Expr[String => String] = '{ (x: String) => ${body('x)} }
+  def lam(body: Quotes ?=> Expr[String] => Expr[String])(using Quotes): Expr[String => String] = '{ (x: String) => ${body('x)} }
 }
 
 object ComputeNum extends Symantics[Int] {
@@ -128,7 +128,7 @@ object ComputeNum extends Symantics[Int] {
   def plus(x: Expr[Int], y: Expr[Int])(using Quotes): Expr[Int] = '{ $x + $y }
   def times(x: Expr[Int], y: Expr[Int])(using Quotes): Expr[Int] = '{ $x * $y }
   def app(f: Expr[Int => Int], x: Expr[Int])(using Quotes): Expr[Int] = '{ $f($x) }
-  def lam(body: Expr[Int] => Expr[Int])(using Quotes): Expr[Int => Int] = '{ (x: Int) => ${body('x)} }
+  def lam(body: Quotes ?=> Expr[Int] => Expr[Int])(using Quotes): Expr[Int => Int] = '{ (x: Int) => ${body('x)} }
 }
 
 object ASTNum extends Symantics[ASTNum] {
@@ -136,7 +136,7 @@ object ASTNum extends Symantics[ASTNum] {
   def plus(x: Expr[ASTNum], y: Expr[ASTNum])(using Quotes): Expr[ASTNum] = '{ PlusAST($x, $y) }
   def times(x: Expr[ASTNum], y: Expr[ASTNum])(using Quotes): Expr[ASTNum] = '{ TimesAST($x, $y) }
   def app(f: Expr[ASTNum => ASTNum], x: Expr[ASTNum])(using Quotes): Expr[ASTNum] = '{ AppAST($f, $x) }
-  def lam(body: Expr[ASTNum] => Expr[ASTNum])(using Quotes): Expr[ASTNum => ASTNum] = '{ (x: ASTNum) => ${body('x)} }
+  def lam(body: Quotes ?=> Expr[ASTNum] => Expr[ASTNum])(using Quotes): Expr[ASTNum => ASTNum] = '{ (x: ASTNum) => ${body('x)} }
 }
 
 trait ASTNum
diff --git a/tests/run-macros/quote-matcher-symantics-3/quoted_1.scala b/tests/run-macros/quote-matcher-symantics-3/quoted_1.scala
index 1855fb10f856..5aa3a1f700ea 100644
--- a/tests/run-macros/quote-matcher-symantics-3/quoted_1.scala
+++ b/tests/run-macros/quote-matcher-symantics-3/quoted_1.scala
@@ -24,7 +24,7 @@ object Macros {
             None
     }
 
-    def lift[T: Type](e: Expr[T])(using env: Env): Expr[R[T]] = ((e: Expr[Any]) match {
+    def lift[T: Type](e: Expr[T])(using env: Env)(using Quotes): Expr[R[T]] = ((e: Expr[Any]) match {
       case Const(e: Int) => '{ $sym.int(${Expr(e)}).asInstanceOf[R[T]] }
       case Const(e: Boolean) => '{ $sym.bool(${Expr(e)}).asInstanceOf[R[T]] }
 
diff --git a/tests/run-staging/i3947.scala b/tests/run-staging/i3947.scala
index cf83bae1ccb9..4e5519b47576 100644
--- a/tests/run-staging/i3947.scala
+++ b/tests/run-staging/i3947.scala
@@ -6,7 +6,7 @@ object Test {
 
   given Compiler = Compiler.make(getClass.getClassLoader)
   def main(args: Array[String]): Unit = run {
-    def test[T: Type](clazz: java.lang.Class[T]) = {
+    def test[T: Type](clazz: java.lang.Class[T])(using Quotes) = {
       val lclazz = Expr(clazz)
       val name = '{ ($lclazz).getCanonicalName }
       println(name.show)
diff --git a/tests/run-staging/i3947b.scala b/tests/run-staging/i3947b.scala
index fb1d0f19d995..e370741af58b 100644
--- a/tests/run-staging/i3947b.scala
+++ b/tests/run-staging/i3947b.scala
@@ -7,7 +7,7 @@ object Test {
   given Compiler = Compiler.make(getClass.getClassLoader)
 
   def main(args: Array[String]): Unit = run {
-    def test[T: Type](clazz: java.lang.Class[T]) = {
+    def test[T: Type](clazz: java.lang.Class[T])(using Quotes) = {
       val lclazz = Expr(clazz)
       val name = '{ ($lclazz).getCanonicalName }
       println()
diff --git a/tests/run-staging/i3947b2.scala b/tests/run-staging/i3947b2.scala
index 33d76753b1a4..27a82641c74b 100644
--- a/tests/run-staging/i3947b2.scala
+++ b/tests/run-staging/i3947b2.scala
@@ -7,7 +7,7 @@ object Test {
   given Compiler = Compiler.make(getClass.getClassLoader)
 
   def main(args: Array[String]): Unit = run {
-    def test[T: Type](clazz: Quotes ?=> java.lang.Class[T]) = {
+    def test[T: Type](clazz: Quotes ?=> java.lang.Class[T])(using Quotes) = {
       val lclazz = Expr(clazz)
       val name = '{ ($lclazz).getCanonicalName }
       println()
diff --git a/tests/run-staging/i3947b3.scala b/tests/run-staging/i3947b3.scala
index fd9ec26d15a6..ea7cead059d3 100644
--- a/tests/run-staging/i3947b3.scala
+++ b/tests/run-staging/i3947b3.scala
@@ -7,7 +7,7 @@ object Test {
   given Compiler = Compiler.make(getClass.getClassLoader)
 
   def main(args: Array[String]): Unit = run {
-    def test[T: Type](clazz: java.lang.Class[T]) = {
+    def test[T: Type](clazz: java.lang.Class[T])(using Quotes) = {
       val lclazz = Expr(clazz)
       val name = '{ ($lclazz).getCanonicalName }
       println(name.show)
diff --git a/tests/run-staging/i3947c.scala b/tests/run-staging/i3947c.scala
index 963ff3750fbd..9cab4fe3275a 100644
--- a/tests/run-staging/i3947c.scala
+++ b/tests/run-staging/i3947c.scala
@@ -6,7 +6,7 @@ object Test {
   given Compiler = Compiler.make(getClass.getClassLoader)
 
   def main(args: Array[String]): Unit = run {
-    def test[T: Type](clazz: java.lang.Class[T]) = {
+    def test[T: Type](clazz: java.lang.Class[T])(using Quotes) = {
       val lclazz = Expr(clazz)
       val name = '{ ($lclazz).getCanonicalName }
       println(name.show)
diff --git a/tests/run-staging/i3947d.scala b/tests/run-staging/i3947d.scala
index 44c46ee169ef..5bb66e764bbb 100644
--- a/tests/run-staging/i3947d.scala
+++ b/tests/run-staging/i3947d.scala
@@ -5,7 +5,7 @@ object Test {
   given Compiler = Compiler.make(getClass.getClassLoader)
 
   def main(args: Array[String]): Unit = run {
-    def test[T: Type](clazz: java.lang.Class[T]) = {
+    def test[T: Type](clazz: java.lang.Class[T])(using Quotes) = {
       val lclazz = Expr(clazz)
       val name = '{ ($lclazz).getCanonicalName }
       println(name.show)
diff --git a/tests/run-staging/i3947d2.scala b/tests/run-staging/i3947d2.scala
index 0108893a7b78..b6d1ff971575 100644
--- a/tests/run-staging/i3947d2.scala
+++ b/tests/run-staging/i3947d2.scala
@@ -6,7 +6,7 @@ object Test {
   given Compiler = Compiler.make(getClass.getClassLoader)
 
   def main(args: Array[String]): Unit = run {
-    def test[T: Type](clazz: java.lang.Class[T]) = {
+    def test[T: Type](clazz: java.lang.Class[T])(using Quotes) = {
       val lclazz = Expr(clazz)
       val name = '{ ($lclazz).getCanonicalName }
       println(name.show)
diff --git a/tests/run-staging/i3947e.scala b/tests/run-staging/i3947e.scala
index 64f4e51dfdda..f16c5ddd8134 100644
--- a/tests/run-staging/i3947e.scala
+++ b/tests/run-staging/i3947e.scala
@@ -7,7 +7,7 @@ object Test {
 
   def main(args: Array[String]): Unit = run {
 
-    def test[T: Type](clazz: java.lang.Class[T]) = {
+    def test[T: Type](clazz: java.lang.Class[T])(using Quotes) = {
       val lclazz = Expr(clazz)
       val name = '{ ($lclazz).getCanonicalName }
       println(name.show)
diff --git a/tests/run-staging/i3947f.scala b/tests/run-staging/i3947f.scala
index 8acbb2b9678b..174da2a121cc 100644
--- a/tests/run-staging/i3947f.scala
+++ b/tests/run-staging/i3947f.scala
@@ -7,7 +7,7 @@ object Test {
   given Compiler = Compiler.make(getClass.getClassLoader)
 
   def main(args: Array[String]): Unit = run {
-    def test[T: Type](clazz: java.lang.Class[T]) = {
+    def test[T: Type](clazz: java.lang.Class[T])(using Quotes) = {
       val lclazz = Expr(clazz)
       val name = '{ ($lclazz).getCanonicalName }
       println(name.show)
diff --git a/tests/run-staging/i3947g.scala b/tests/run-staging/i3947g.scala
index 548566213321..5f6d6275fc6e 100644
--- a/tests/run-staging/i3947g.scala
+++ b/tests/run-staging/i3947g.scala
@@ -5,7 +5,7 @@ import scala.quoted.staging.*
 object Test {
   given Compiler = Compiler.make(getClass.getClassLoader)
   def main(args: Array[String]): Unit = run {
-    def test[T: Type](clazz: java.lang.Class[T]) = {
+    def test[T: Type](clazz: java.lang.Class[T])(using Quotes) = {
       val lclazz = Expr(clazz)
       val name = '{ ($lclazz).getCanonicalName }
       println(name.show)
diff --git a/tests/run-staging/i3947i.scala b/tests/run-staging/i3947i.scala
index bc5151528de6..dd2f6f1824c0 100644
--- a/tests/run-staging/i3947i.scala
+++ b/tests/run-staging/i3947i.scala
@@ -6,7 +6,7 @@ object Test {
   given Compiler = Compiler.make(getClass.getClassLoader)
 
   def main(args: Array[String]): Unit = run {
-    def test[T: Type](clazz: java.lang.Class[T]) = {
+    def test[T: Type](clazz: java.lang.Class[T])(using Quotes) = {
       val lclazz = Expr(clazz)
       val name = '{ ($lclazz).getCanonicalName }
       println(name.show)
diff --git a/tests/run-staging/i3947j.scala b/tests/run-staging/i3947j.scala
index 19b7c4a7f77d..164b93f150f5 100644
--- a/tests/run-staging/i3947j.scala
+++ b/tests/run-staging/i3947j.scala
@@ -6,7 +6,7 @@ object Test {
   given Compiler = Compiler.make(getClass.getClassLoader)
 
   def main(args: Array[String]): Unit = run {
-    def test[T: Type](clazz: java.lang.Class[T]) = {
+    def test[T: Type](clazz: java.lang.Class[T])(using Quotes) = {
       val lclazz = Expr(clazz)
       val name = '{ ($lclazz).getCanonicalName }
       println(name.show)
diff --git a/tests/run-staging/quote-run-2.scala b/tests/run-staging/quote-run-2.scala
index 3b69514cf908..3686e37f70c9 100644
--- a/tests/run-staging/quote-run-2.scala
+++ b/tests/run-staging/quote-run-2.scala
@@ -5,7 +5,7 @@ import scala.quoted.staging.*
 object Test {
   given Compiler = Compiler.make(getClass.getClassLoader)
   def main(args: Array[String]): Unit = withQuotes {
-    def powerCode(n: Int, x: Expr[Double]): Expr[Double] =
+    def powerCode(n: Int, x: Expr[Double])(using Quotes): Expr[Double] =
       if (n == 0) '{1.0}
       else if (n == 1) x
       else if (n % 2 == 0) '{ { val y = $x * $x; ${powerCode(n / 2, 'y)} } }
diff --git a/tests/run-staging/quote-run-staged-interpreter.scala b/tests/run-staging/quote-run-staged-interpreter.scala
index 2f2d977f6d4e..3aedb4a8429e 100644
--- a/tests/run-staging/quote-run-staged-interpreter.scala
+++ b/tests/run-staging/quote-run-staged-interpreter.scala
@@ -12,7 +12,7 @@ object Test {
   import Exp.*
 
   def compile(e: Exp, env: Map[String, Expr[Int]], keepLets: Boolean)(using Quotes): Expr[Int] = {
-    def compileImpl(e: Exp, env: Map[String, Expr[Int]]): Expr[Int] = e match {
+    def compileImpl(e: Exp, env: Map[String, Expr[Int]])(using Quotes): Expr[Int] = e match {
       case Num(n) => Expr(n)
       case Plus(e1, e2) => '{${compileImpl(e1, env)} + ${compileImpl(e2, env)}}
       case Var(x) => env(x)
diff --git a/tests/run-staging/staged-streams_1.scala b/tests/run-staging/staged-streams_1.scala
index 3018f85aaf21..5315f66871ca 100644
--- a/tests/run-staging/staged-streams_1.scala
+++ b/tests/run-staging/staged-streams_1.scala
@@ -681,18 +681,18 @@ object Test {
 }
 
 sealed trait Var[T] {
-  def get(using Quotes): Expr[T]
-  def update(e: Expr[T])(using Quotes): Expr[Unit]
+  def get: Expr[T]
+  def update(e: Quotes ?=> Expr[T]): Expr[Unit]
 }
 
 object Var {
-  def apply[T: Type, U: Type](init: Expr[T])(body: Var[T] => Expr[U])(using Quotes): Expr[U] = '{
+  def apply[T: Type, U: Type](init: Expr[T])(body: Quotes ?=> Var[T] => Expr[U])(using Quotes): Expr[U] = '{
     var x = $init
     ${
       body(
         new Var[T] {
-          def get(using Quotes): Expr[T] = 'x
-          def update(e: Expr[T])(using Quotes): Expr[Unit] = '{ x = $e }
+          def get: Expr[T] = 'x
+          def update(e: Quotes ?=> Expr[T]): Expr[Unit] = '{ x = $e }
         }
       )
     }

From 6e18e45c59e55131b3e28309a5da7114a439cff4 Mon Sep 17 00:00:00 2001
From: Nicolas Stucki <nicolas.stucki@gmail.com>
Date: Fri, 26 Feb 2021 12:00:03 +0100
Subject: [PATCH 2/3] Use SpliceScope instead of ScopeId and remove it

---
 .../tools/dotc/quoted/PickledQuotes.scala     |  6 ++---
 .../dotty/tools/dotc/transform/Splicer.scala  |  4 +--
 .../scala/quoted/runtime/impl/ExprImpl.scala  | 11 +++-----
 .../quoted/runtime/impl/QuotesImpl.scala      | 27 +++++--------------
 .../quoted/runtime/impl/ScopeException.scala  |  3 +++
 .../quoted/runtime/impl/SpliceScope.scala     |  6 ++++-
 .../scala/quoted/runtime/impl/TypeImpl.scala  | 18 +++----------
 7 files changed, 26 insertions(+), 49 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/quoted/PickledQuotes.scala b/compiler/src/dotty/tools/dotc/quoted/PickledQuotes.scala
index bc5e7cdc4dc1..fd118eb43bb5 100644
--- a/compiler/src/dotty/tools/dotc/quoted/PickledQuotes.scala
+++ b/compiler/src/dotty/tools/dotc/quoted/PickledQuotes.scala
@@ -41,7 +41,6 @@ object PickledQuotes {
   /** Transform the expression into its fully spliced Tree */
   def quotedExprToTree[T](expr: quoted.Expr[T])(using Context): Tree = {
     val expr1 = expr.asInstanceOf[ExprImpl]
-    expr1.checkScopeId(QuotesImpl.scopeId)
     ScopeException.checkInCorrectScope(expr1.scope, SpliceScope.getCurrent, expr1.tree, "Expr")
     changeOwnerOfTree(expr1.tree, ctx.owner)
   }
@@ -49,7 +48,6 @@ object PickledQuotes {
   /** Transform the expression into its fully spliced TypeTree */
   def quotedTypeToTree(tpe: quoted.Type[?])(using Context): Tree = {
     val tpe1 = tpe.asInstanceOf[TypeImpl]
-    tpe1.checkScopeId(QuotesImpl.scopeId)
     ScopeException.checkInCorrectScope(tpe1.scope, SpliceScope.getCurrent, tpe1.typeTree, "Type")
     changeOwnerOfTree(tpe1.typeTree, ctx.owner)
   }
@@ -77,8 +75,8 @@ object PickledQuotes {
         case Hole(isTerm, idx, args) =>
           inContext(SpliceScope.contextWithNewSpliceScope(tree.sourcePos)) {
             val reifiedArgs = args.map { arg =>
-              if (arg.isTerm) (q: Quotes) ?=> new ExprImpl(arg, QuotesImpl.scopeId, SpliceScope.getCurrent)
-              else new TypeImpl(arg, QuotesImpl.scopeId, SpliceScope.getCurrent)
+              if (arg.isTerm) (q: Quotes) ?=> new ExprImpl(arg, SpliceScope.getCurrent)
+              else new TypeImpl(arg, SpliceScope.getCurrent)
             }
             if isTerm then
               val quotedExpr = termHole(idx, reifiedArgs, QuotesImpl())
diff --git a/compiler/src/dotty/tools/dotc/transform/Splicer.scala b/compiler/src/dotty/tools/dotc/transform/Splicer.scala
index 864c06faa72c..4acc0e5e38ed 100644
--- a/compiler/src/dotty/tools/dotc/transform/Splicer.scala
+++ b/compiler/src/dotty/tools/dotc/transform/Splicer.scala
@@ -326,10 +326,10 @@ object Splicer {
     }
 
     private def interpretQuote(tree: Tree)(implicit env: Env): Object =
-      new ExprImpl(Inlined(EmptyTree, Nil, QuoteUtils.changeOwnerOfTree(tree, ctx.owner)).withSpan(tree.span), QuotesImpl.scopeId, SpliceScope.getCurrent)
+      new ExprImpl(Inlined(EmptyTree, Nil, QuoteUtils.changeOwnerOfTree(tree, ctx.owner)).withSpan(tree.span), SpliceScope.getCurrent)
 
     private def interpretTypeQuote(tree: Tree)(implicit env: Env): Object =
-      new TypeImpl(QuoteUtils.changeOwnerOfTree(tree, ctx.owner), QuotesImpl.scopeId, SpliceScope.getCurrent)
+      new TypeImpl(QuoteUtils.changeOwnerOfTree(tree, ctx.owner), SpliceScope.getCurrent)
 
     private def interpretLiteral(value: Any)(implicit env: Env): Object =
       value.asInstanceOf[Object]
diff --git a/compiler/src/scala/quoted/runtime/impl/ExprImpl.scala b/compiler/src/scala/quoted/runtime/impl/ExprImpl.scala
index d04cb9a160f3..ffd12b2e89b0 100644
--- a/compiler/src/scala/quoted/runtime/impl/ExprImpl.scala
+++ b/compiler/src/scala/quoted/runtime/impl/ExprImpl.scala
@@ -10,19 +10,14 @@ import dotty.tools.dotc.ast.tpd
  *
  *  May contain references to code defined outside this Expr instance.
  */
-final class ExprImpl(val tree: tpd.Tree, val scopeId: Int, val scope: Scope) extends Expr[Any] {
+final class ExprImpl(val tree: tpd.Tree, val scope: Scope) extends Expr[Any] {
   override def equals(that: Any): Boolean = that match {
     case that: ExprImpl =>
       // Expr are wrappers around trees, therefore they are equals if their trees are equal.
-      // All scopeId should be equal unless two different runs of the compiler created the trees.
-      tree == that.tree && scopeId == that.scopeId
+      // All scope should be equal unless two different runs of the compiler created the trees.
+      tree == that.tree && scope == that.scope
     case _ => false
   }
 
-  def checkScopeId(expectedScopeId: Int): Unit =
-    if expectedScopeId != scopeId then
-      throw new ScopeException("Cannot call `scala.quoted.staging.run(...)` within a macro or another `run(...)`")
-
-  override def hashCode: Int = tree.hashCode
   override def toString: String = "'{ ... }"
 }
diff --git a/compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala b/compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala
index 0e70e9ea4c75..528cd762bb73 100644
--- a/compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala
+++ b/compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala
@@ -23,8 +23,6 @@ import scala.reflect.TypeTest
 
 object QuotesImpl {
 
-  type ScopeId = Int
-
   def apply()(using Context): Quotes =
     new QuotesImpl
 
@@ -34,11 +32,6 @@ object QuotesImpl {
     if ctx.settings.color.value == "always" then TreeAnsiCode.show(tree)
     else TreeCode.show(tree)
 
-  // TODO Explore more fine grained scope ids.
-  //      This id can only differentiate scope extrusion from one compiler instance to another.
-  def scopeId(using Context): ScopeId =
-    ctx.outersIterator.toList.last.hashCode()
-
 }
 
 class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler, QuoteMatching:
@@ -81,10 +74,7 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
     end CompilationInfo
 
     extension (expr: Expr[Any])
-      def asTerm: Term =
-        val exprImpl = expr.asInstanceOf[ExprImpl]
-        exprImpl.checkScopeId(QuotesImpl.this.hashCode)
-        exprImpl.tree
+      def asTerm: Term = expr.asInstanceOf[ExprImpl].tree
     end extension
 
     type Tree = tpd.Tree
@@ -105,7 +95,7 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
             case _ => false
         def asExpr: scala.quoted.Expr[Any] =
           if self.isExpr then
-            new ExprImpl(self, QuotesImpl.this.hashCode, SpliceScope.getCurrent)
+            new ExprImpl(self, SpliceScope.getCurrent)
           else self match
             case TermTypeTest(self) => throw new Exception("Expected an expression. This is a partially applied Term. Try eta-expanding the term first.")
             case _ => throw new Exception("Expected a Term but was: " + self)
@@ -372,11 +362,11 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
     given TermMethods: TermMethods with
       extension (self: Term)
         def seal: scala.quoted.Expr[Any] =
-          if self.isExpr then new ExprImpl(self, QuotesImpl.this.hashCode, SpliceScope.getCurrent)
+          if self.isExpr then new ExprImpl(self, SpliceScope.getCurrent)
           else throw new Exception("Cannot seal a partially applied Term. Try eta-expanding the term first.")
 
         def sealOpt: Option[scala.quoted.Expr[Any]] =
-          if self.isExpr then Some(new ExprImpl(self, QuotesImpl.this.hashCode, SpliceScope.getCurrent))
+          if self.isExpr then Some(new ExprImpl(self, SpliceScope.getCurrent))
           else None
 
         def tpe: TypeRepr = self.tpe
@@ -1666,7 +1656,7 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
         def seal: scala.quoted.Type[_] = self.asType
 
         def asType: scala.quoted.Type[?] =
-          new TypeImpl(Inferred(self), QuotesImpl.this.hashCode, SpliceScope.getCurrent)
+          new TypeImpl(Inferred(self), SpliceScope.getCurrent)
 
         def =:=(that: TypeRepr): Boolean = self =:= that
         def <:<(that: TypeRepr): Boolean = self <:< that
@@ -2877,11 +2867,11 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
 
   def unpickleExpr[T](pickled: String | List[String], typeHole: (Int, Seq[Any]) => scala.quoted.Type[?], termHole: (Int, Seq[Any], scala.quoted.Quotes) => scala.quoted.Expr[?]): scala.quoted.Expr[T] =
     val tree = PickledQuotes.unpickleTerm(pickled, typeHole, termHole)
-    new ExprImpl(tree, hash, SpliceScope.getCurrent).asInstanceOf[scala.quoted.Expr[T]]
+    new ExprImpl(tree, SpliceScope.getCurrent).asInstanceOf[scala.quoted.Expr[T]]
 
   def unpickleType[T <: AnyKind](pickled: String | List[String], typeHole: (Int, Seq[Any]) => scala.quoted.Type[?], termHole: (Int, Seq[Any], scala.quoted.Quotes) => scala.quoted.Expr[?]): scala.quoted.Type[T] =
     val tree = PickledQuotes.unpickleTypeTree(pickled, typeHole, termHole)
-    new TypeImpl(tree, hash, SpliceScope.getCurrent).asInstanceOf[scala.quoted.Type[T]]
+    new TypeImpl(tree, SpliceScope.getCurrent).asInstanceOf[scala.quoted.Type[T]]
 
   object ExprMatch extends ExprMatchModule:
     def unapply[TypeBindings <: Tuple, Tup <: Tuple](scrutinee: scala.quoted.Expr[Any])(using pattern: scala.quoted.Expr[Any]): Option[Tup] =
@@ -2948,7 +2938,4 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
     }
   }
 
-  private[this] val hash = QuotesImpl.scopeId(using ctx)
-  override def hashCode: Int = hash
-
 end QuotesImpl
diff --git a/compiler/src/scala/quoted/runtime/impl/ScopeException.scala b/compiler/src/scala/quoted/runtime/impl/ScopeException.scala
index 7dc84343238e..c0507495cbc2 100644
--- a/compiler/src/scala/quoted/runtime/impl/ScopeException.scala
+++ b/compiler/src/scala/quoted/runtime/impl/ScopeException.scala
@@ -7,6 +7,9 @@ class ScopeException(msg: String) extends Exception(msg)
 
 object ScopeException:
   def checkInCorrectScope(scope: Scope, currentScope: Scope, tree: Tree, kind: String)(using Context): Unit =
+    if scope.root != currentScope.root then
+      throw new ScopeException(s"Cannot use $kind oustide of the macro splice `$${...}` or the scala.quoted.staging.run(...)` where it was defined")
+
     val yCheck = ctx.settings.Ycheck.value(using ctx).exists(x => x == "all" || x == "macros")
     if yCheck && !scope.isOuterScopeOf(currentScope) then
       throw new ScopeException(
diff --git a/compiler/src/scala/quoted/runtime/impl/SpliceScope.scala b/compiler/src/scala/quoted/runtime/impl/SpliceScope.scala
index b44b1c2c5b80..6ba8e97a2c71 100644
--- a/compiler/src/scala/quoted/runtime/impl/SpliceScope.scala
+++ b/compiler/src/scala/quoted/runtime/impl/SpliceScope.scala
@@ -18,6 +18,9 @@ trait Scope {
   /** Is this is a outer scope of the given scope */
   def isOuterScopeOf(scope: Scope): Boolean =
     this.eq(scope) || (scope.ne(NoScope) && isOuterScopeOf(scope.outer))
+  /** Scope of he top level splice or staging `run` */
+  def root: Scope =
+    if outer.eq(NoScope) then this else outer.root
   /** Stack of locations where scopes where evaluated */
   def stack: List[String] =
     this.toString :: (if outer.eq(NoScope) then Nil else outer.stack)
@@ -27,6 +30,7 @@ trait Scope {
 
 /** Only used for outer scope of top level splice and staging `run` */
 object NoScope extends Scope:
+  override def root: Scope = this
   override def outer: Scope = throw UnsupportedOperationException("NoScope.outer")
 
 class SpliceScope(val pos: SourcePosition, override val outer: Scope) extends Scope:
@@ -57,6 +61,6 @@ object SpliceScope:
 
     /** Context with an incremented quotation level. */
   def getCurrent(using Context): Scope =
-      ctx.property(ScopeKey).getOrElse(null)
+      ctx.property(ScopeKey).getOrElse(NoScope)
 
 end SpliceScope
diff --git a/compiler/src/scala/quoted/runtime/impl/TypeImpl.scala b/compiler/src/scala/quoted/runtime/impl/TypeImpl.scala
index 9add4060f1ee..51df479e4663 100644
--- a/compiler/src/scala/quoted/runtime/impl/TypeImpl.scala
+++ b/compiler/src/scala/quoted/runtime/impl/TypeImpl.scala
@@ -4,24 +4,14 @@ package runtime.impl
 import dotty.tools.dotc.ast.tpd
 
 /** Quoted type (or kind) `T` backed by a tree */
-final class TypeImpl(val typeTree: tpd.Tree, val scopeId: Int, val scope: Scope) extends Type[?] {
+final class TypeImpl(val typeTree: tpd.Tree, val scope: Scope) extends Type[?] {
   override def equals(that: Any): Boolean = that match {
     case that: TypeImpl => typeTree ==
-      // TastyTreeExpr are wrappers around trees, therfore they are equals if their trees are equal.
-      // All scopeId should be equal unless two different runs of the compiler created the trees.
-      that.typeTree && scopeId == that.scopeId
+      // TastyTreeExpr are wrappers around trees, therefore they are equals if their trees are equal.
+      // All scope should be equal unless two different runs of the compiler created the trees.
+      that.typeTree && scope == that.scope
     case _ => false
   }
 
-  /** View this expression `q.Type[T]` as a `TypeTree` */
-  def unseal(using q: Quotes): q.reflect.TypeTree =
-    checkScopeId(q.hashCode)
-    typeTree.asInstanceOf[q.reflect.TypeTree]
-
-  def checkScopeId(expectedScopeId: Int): Unit =
-    if expectedScopeId != scopeId then
-      throw new ScopeException("Cannot call `scala.quoted.staging.run(...)` within a macro or another `run(...)`")
-
-  override def hashCode: Int = typeTree.hashCode
   override def toString: String = "Type.of[...]"
 }

From 7e2e6d31030bba0b3f2fd526eef4733375283bf7 Mon Sep 17 00:00:00 2001
From: Nicolas Stucki <nicolas.stucki@gmail.com>
Date: Mon, 1 Mar 2021 14:27:58 +0100
Subject: [PATCH 3/3] Apply suggestions from code review

Co-authored-by: Fengyun Liu <liu@fengy.me>
---
 compiler/src/scala/quoted/runtime/impl/SpliceScope.scala | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/compiler/src/scala/quoted/runtime/impl/SpliceScope.scala b/compiler/src/scala/quoted/runtime/impl/SpliceScope.scala
index 6ba8e97a2c71..797b38be2743 100644
--- a/compiler/src/scala/quoted/runtime/impl/SpliceScope.scala
+++ b/compiler/src/scala/quoted/runtime/impl/SpliceScope.scala
@@ -5,20 +5,20 @@ import dotty.tools.dotc.core.Contexts._
 import dotty.tools.dotc.util.Property
 import dotty.tools.dotc.util.SourcePosition
 
-/** Unique identifier of the evaluation of a splice.
+/** A scope uniquely identifies the context for evaluating a splice
  *
- *  A nested splice gets a new Scope with the outer one as an owner.
+ *  A nested splice gets a new scope with the enclosing scope as its `outer`.
  *  This also applies for recursive splices.
  */
 trait Scope {
   /** Outer scope that was used to create the quote containing this splice.
-   *  NoScope if there is no scope
+   *  NoScope otherwise.
    */
   def outer: Scope = NoScope
   /** Is this is a outer scope of the given scope */
   def isOuterScopeOf(scope: Scope): Boolean =
     this.eq(scope) || (scope.ne(NoScope) && isOuterScopeOf(scope.outer))
-  /** Scope of he top level splice or staging `run` */
+  /** Scope of the top level splice or staging `run` */
   def root: Scope =
     if outer.eq(NoScope) then this else outer.root
   /** Stack of locations where scopes where evaluated */