Fix scala#7142: Detect scope extrusions in macros and run

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

@@ -44,7 +44,11 @@ object Splicer {
       try {
         // Some parts of the macro are evaluated during the unpickling performed in quotedExprToTree
         val interpretedExpr = interpreter.interpret[scala.quoted.QuoteContext => scala.quoted.Expr[Any]](tree)
-        interpretedExpr.fold(tree)(macroClosure => PickledQuotes.quotedExprToTree(macroClosure(QuoteContext())))
+        val interpretedTree = interpretedExpr.fold(tree)(macroClosure => PickledQuotes.quotedExprToTree(macroClosure(QuoteContext())))
+        freeVariables(interpretedTree).foreach {
+          x => ctx.error(em"$x was used outside the scope where it was defined", x.symbol.sourcePos)
+        }
+        interpretedTree
       }
       catch {
         case ex: CompilationUnit.SuspendException =>
@@ -63,6 +67,17 @@ object Splicer {
       }
   }
 
+  private def freeVariables(tree: Tree)(given ctx: Context): List[Tree] =
+    def isFreeVariable(sym: Symbol): Boolean =
+      sym.exists && !sym.is(Package) && !sym.owner.isStaticOwner && !ctx.owner.ownersIterator.contains(sym.owner)
+    new TreeAccumulator[List[Tree]] {
+      def apply(x: List[Tree], tree: Tree)(given ctx: Context): List[Tree] = tree match {
+        case tree: Ident if isFreeVariable(tree.symbol) => tree :: x
+        case _ => foldOver(x, tree)
+      }
+    }.apply(Nil, tree)
+
+
   /** Check that the Tree can be spliced. `${'{xyz}}` becomes `xyz`
     *  and for `$xyz` the tree of `xyz` is interpreted for which the
     *  resulting expression is returned as a `Tree`

tests/neg-macros/i7142/Macro_1.scala

@@ -0,0 +1,9 @@
+package macros
+import scala.quoted._
+
+def oops(given QuoteContext) = {
+  var v = '{0};
+  val q = '{ (x: Int) => ${ v = '{x}; v } } // error
+  '{$q($v)}
+}
+inline def test = ${oops}

tests/neg-macros/i7142/Test_2.scala

@@ -0,0 +1,4 @@
+
+object Test {
+  macros.test
+}

tests/neg-macros/i7142b/Macro_1.scala

@@ -0,0 +1,8 @@
+package macros
+import scala.quoted._
+import scala.util.control.NonLocalReturns._
+
+def oops(given QuoteContext): Expr[Int] =
+  returning('{ { (x: Int) => ${ throwReturn('x) }} apply 0 }) // error
+
+inline def test = ${oops}

tests/neg-macros/i7142b/Test_2.scala

@@ -0,0 +1,4 @@
+
+object Test {
+  macros.test
+}