Tighten condition to preserve denotation in IntegrateMap (#23060)

Should fix #23056. I haven't been able to understand exactly what is
going on there yet, but the problem seems to arise in a situation where
the denotation should be reloaded during `integrate` and is not. This PR
makes sure that we keep the previous denotation for `NamedType` _only_
if its prefix is a `ParamRef` bound to the `LambdaType` we are
integrating over.

Author: mbovel

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -3858,8 +3858,12 @@ object Types extends TypeUtils {
 
       override final def derivedSelect(tp: NamedType, pre: Type): Type =
         if tp.prefix eq pre then tp
-        else if tp.symbol.exists then NamedType(pre, tp.name, tp.denot.asSeenFrom(pre))
-        else NamedType(pre, tp.name)
+        else
+          pre match
+            case ref: ParamRef if (ref.binder eq self) && tp.symbol.exists =>
+              NamedType(pre, tp.name, tp.denot.asSeenFrom(pre))
+            case _ =>
+              tp.derivedSelect(pre)
 
     final def derivedLambdaType(paramNames: List[ThisName] = this.paramNames,
                           paramInfos: List[PInfo] = this.paramInfos,

tests/pos/23056.scala

@@ -0,0 +1,18 @@
+def Test = {
+  val ops: CompileOps[Option, Option, Any]  = ???
+  ops.to(List).map(_.reverse) // error
+}
+
+trait CompileOps[F[_], G[_], O]:
+  def to(collector: Collector[O]): G[collector.Out]
+trait Collector[-A] {
+  type Out
+}
+
+object Collector:
+  type Aux[A, X] = Collector[A] { type Out = X }
+
+  given [A, C[_]]: Conversion[
+    scala.collection.IterableFactory[C],
+    Collector.Aux[A, C[A]]
+  ] = ???