Fix owner of spices in class statements

Fixes #18358

Author: nicolasstucki

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

@@ -125,6 +125,18 @@ object PickledQuotes {
               val quotedType = evalHole.nn.apply(idx, reifyTypeHoleArgs(args))
               PickledQuotes.quotedTypeToTree(quotedType)
           }
+        case tree @ Template(constr, parents, self, _) if tree.derived.isEmpty =>
+          // Set local dummy as owner when we transform class statements
+          val constr1 = transformSub(constr)
+          val parents1 = transform(tree.parents)
+          val self1 = transformSub(self)
+          val stats1 = flatten(tree.body.mapConserve {
+            case stat: DefTree => transform(stat)
+            case stat =>
+              val localDummy = tree.tpe.termSymbol
+              transform(stat)(using ctx.withOwner(localDummy))
+          })
+          cpy.Template(tree)(constr1, parents1, Nil, self1, stats1)
         case tree =>
           if tree.isDef then
             tree.symbol.annotations = tree.symbol.annotations.map {

tests/pos-macros/i18358/Macro_1.scala

@@ -0,0 +1,4 @@
+import scala.quoted.*
+inline def generateCode: Unit = ${ testLocalDummyOwner }
+def testLocalDummyOwner(using Quotes): Expr[Unit] = '{ trait E { $valInBlock } }
+def valInBlock(using Quotes): Expr[Unit] = '{ val x: Int = 2; () }

tests/pos-macros/i18358/Test_2.scala

@@ -0,0 +1 @@
+def test = generateCode