Re-skolem type prefixes post-unpickling

Author: dwijnand

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -395,9 +395,10 @@ class TreeUnpickler(reader: TastyReader,
             case TYPEREFin =>
               val name = readName().toTypeName
               val prefix = readType()
+              def pre = if TypeOps.isLegalPrefix(prefix) then prefix else QualSkolemType(prefix)
               val space = readType()
               space.decl(name) match {
-                case symd: SymDenotation if prefix.isArgPrefixOf(symd.symbol) => TypeRef(prefix, symd.symbol)
+                case symd: SymDenotation if prefix.isArgPrefixOf(symd.symbol) => TypeRef(pre, symd.symbol)
                 case _ => TypeRef(prefix, name, space.decl(name).asSeenFrom(prefix))
               }
             case REFINEDtype =>

compiler/src/dotty/tools/dotc/inlines/Inliner.scala

@@ -768,6 +768,7 @@ class Inliner(val call: tpd.Tree)(using Context):
     override def typedSelect(tree: untpd.Select, pt: Type)(using Context): Tree = {
       val locked = ctx.typerState.ownedVars
       val qual1 = typed(tree.qualifier, shallowSelectionProto(tree.name, pt, this, tree.nameSpan))
+      selectionType(tree, qual1) // side-effect
       val resNoReduce = untpd.cpy.Select(tree)(qual1, tree.name).withType(tree.typeOpt)
       val reducedProjection = reducer.reduceProjection(resNoReduce)
       if reducedProjection.isType then

tests/pos/i22070/macro.scala

@@ -0,0 +1,18 @@
+trait Featureful[T]:
+  def toFeatures(value: T): IArray[Float]
+
+object Featureful:
+  inline def derived[T](using scala.deriving.Mirror.Of[T]) = ${ derivedImpl[T] }
+
+  import scala.quoted.*
+  private def derivedImpl[T: Type](using Quotes): Expr[Featureful[T]] =
+    import quotes.reflect.*
+    '{
+      new Featureful[T]:
+        def toFeatures(value: T) =
+          val feats   = IArray.empty[Featureful[?]]
+          val product = value.asInstanceOf[Product]
+          product.productIterator.zipWithIndex.foreach: (any, idx) =>
+            feats(idx).toFeatures(any.asInstanceOf)
+          IArray.empty
+    }

tests/pos/i22070/usage.scala

@@ -0,0 +1 @@
+case class Breaks(x: Boolean, y: Boolean) derives Featureful