Mark the type of lifted definitions as inferred

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

@@ -371,11 +371,13 @@ class PostTyper extends MacroTransform with InfoTransformer { thisPhase =>
      *  clean retains annotations from such types. But for an overriding symbol the
      *  retains annotations come from the explicitly declared parent types, so should
      *  be kept.
+     *  TODO: If the overriden type is an InferredType, we should probably clean retains
+     *  from both types as well.
      */
     private def makeOverrideTypeDeclared(symbol: Symbol, tpt: Tree)(using Context): Tree =
       tpt match
         case tpt: InferredTypeTree
-        if symbol.allOverriddenSymbols.hasNext =>
+        if Feature.ccEnabled && symbol.allOverriddenSymbols.hasNext =>
           TypeTree(tpt.tpe, inferred = false).withSpan(tpt.span).withAttachmentsFrom(tpt)
         case _ =>
           tpt

compiler/src/dotty/tools/dotc/typer/EtaExpansion.scala

@@ -37,7 +37,9 @@ abstract class Lifter {
   protected def liftedFlags: FlagSet = EmptyFlags
 
   /** The tree of a lifted definition */
-  protected def liftedDef(sym: TermSymbol, rhs: Tree)(using Context): MemberDef = ValDef(sym, rhs)
+  protected def liftedDef(sym: TermSymbol, rhs: Tree)(using Context): MemberDef =
+    // Mark the type of lifted definitions as inferred
+    ValDef(sym, rhs, inferred = true)
 
   private def lift(defs: mutable.ListBuffer[Tree], expr: Tree, prefix: TermName = EmptyTermName)(using Context): Tree =
     if (noLift(expr)) expr

tests/pos/clear-retains-for-inferred-types/S1.scala

@@ -0,0 +1,7 @@
+import language.experimental.captureChecking
+
+trait MyMap[K, V]:
+  def filterNot(pred: ((K, V)) => Boolean): MyMap[K, V]^{this, pred} = ???
+
+trait MySeq[+T]:
+  def map[U](f: T => U): MySeq[U]^{this, f} = ???

tests/pos/clear-retains-for-inferred-types/S2.scala

@@ -0,0 +1,34 @@
+// i24101
+
+trait AttributeValue
+
+case class CompletedSpan(
+  name: String, // remove to make it compile
+  attributes: MyMap[String, AttributeValue],
+){
+  lazy val allAttributes: MyMap[String, AttributeValue] = attributes
+  var allAttributes2: MyMap[String, AttributeValue] = attributes
+}
+
+def Test =
+  val span: CompletedSpan = ???
+  span.copy(attributes = span.allAttributes.filterNot { _ => false })
+  span.copy(attributes = span.allAttributes2.filterNot { _ => false })
+
+// i24100
+
+trait Type
+
+type ColumnDef = ColumnDef_[Type]
+case class ColumnDef_[+T](comments: String)
+
+type TableDef = TableDef_[ColumnDef]
+case class TableDef_[+C <: ColumnDef_[?]](cols: MySeq[C])
+
+abstract class DdlGenerator:
+  // The result type is inferred here
+  def columnComments(t: TableDef) = t.cols.map(_ => "")
+
+class CassandraDdlGenerator() extends DdlGenerator:
+  // The result type should be inferred here as well
+  override def columnComments(t: TableDef) = ???