Merge pull request #110 from scala/backport-lts-3.3-21945

Backport "Fix scala#20471: owners of top-level symbols in cached quoted code being incorrect" to 3.3 LTS

Author: tgodzik

Diff for: compiler/src/dotty/tools/dotc/quoted/PickledQuotes.scala

@@ -240,7 +240,9 @@ object PickledQuotes {
         treeOwner(tree) match
           case Some(owner) =>
             // Copy the cached tree to make sure the all definitions are unique.
-            TreeTypeMap(oldOwners = List(owner), newOwners = List(owner)).apply(tree)
+            val treeCpy = TreeTypeMap(oldOwners = List(owner), newOwners = List(owner)).apply(tree)
+            // Then replace the symbol owner with the one pointed by the quote context.
+            treeCpy.changeNonLocalOwners(ctx.owner)
           case _ =>
             tree
 

Diff for: tests/pos-macros/i20471/Macro_1.scala

@@ -0,0 +1,63 @@
+import scala.annotation.experimental
+import scala.quoted.*
+import scala.annotation.tailrec
+
+object FlatMap {
+  @experimental inline def derived[F[_]]: FlatMap[F] = MacroFlatMap.derive
+}
+trait FlatMap[F[_]]{
+  def tailRecM[A, B](a: A)(f: A => F[Either[A, B]]): F[B]
+}
+
+@experimental
+object MacroFlatMap:
+
+  inline def derive[F[_]]: FlatMap[F] = ${ flatMap }
+
+  def flatMap[F[_]: Type](using Quotes): Expr[FlatMap[F]] = '{
+    new FlatMap[F]:
+      def tailRecM[A, B](a: A)(f: A => F[Either[A, B]]): F[B] =
+        ${ deriveTailRecM('{ a }, '{ f }) }
+  }
+
+  def deriveTailRecM[F[_]: Type, A: Type, B: Type](
+      a: Expr[A],
+      f: Expr[A => F[Either[A, B]]]
+  )(using q: Quotes): Expr[F[B]] =
+    import quotes.reflect.*
+
+    val body: PartialFunction[(Symbol, TypeRepr), Term] = {
+        case (method, tpe) => {
+          given q2: Quotes = method.asQuotes
+          '{
+            def step(x: A): B = ???
+            ???
+          }.asTerm
+        }
+      }
+
+    val term = '{ $f($a) }.asTerm
+    val name = Symbol.freshName("$anon")
+    val parents = List(TypeTree.of[Object], TypeTree.of[F[B]])
+
+    extension (sym: Symbol) def overridableMembers: List[Symbol] =
+      val member1 = sym.methodMember("abstractEffect")(0)
+      val member2 = sym.methodMember("concreteEffect")(0)
+      def meth(member: Symbol) = Symbol.newMethod(sym, member.name, This(sym).tpe.memberType(member), Flags.Override, Symbol.noSymbol)
+      List(meth(member1), meth(member2))
+
+    val cls = Symbol.newClass(Symbol.spliceOwner, name, parents.map(_.tpe), _.overridableMembers, None)
+
+    def transformDef(method: DefDef)(argss: List[List[Tree]]): Option[Term] =
+      val sym = method.symbol
+      Some(body.apply((sym, method.returnTpt.tpe)))
+
+    val members = cls.declarations
+      .filterNot(_.isClassConstructor)
+      .map: sym =>
+        sym.tree match
+          case method: DefDef => DefDef(sym, transformDef(method))
+          case _ => report.errorAndAbort(s"Not supported: $sym in ${sym.owner}")
+
+    val newCls = New(TypeIdent(cls)).select(cls.primaryConstructor).appliedToNone
+    Block(ClassDef(cls, parents, members) :: Nil, newCls).asExprOf[F[B]]

Diff for: tests/pos-macros/i20471/Main_2.scala

@@ -0,0 +1,7 @@
+import scala.annotation.experimental
+
+@experimental
+object autoFlatMapTests:
+  trait TestAlgebra[T] derives FlatMap:
+    def abstractEffect(a: String): T
+    def concreteEffect(a: String): T = abstractEffect(a + " concreteEffect")