From f5f2ce48b9dc947fc9e7e567fddd4bc4da327821 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bart=C5=82omiej=20Kozak?= <b.kozak@avsystem.com>
Date: Mon, 1 Jun 2026 19:41:25 +0200
Subject: [PATCH 1/6] =?UTF-8?q?refactor(scala-3,core):=20F[=5F]=20?=
 =?UTF-8?q?=E2=86=92=20F[=3F]=20in=20applied=20positions=20(serialization)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Targeted rewrites: Array[GenCodec[?]], Array[Class[?]], List[Case[?]],
Opt[cborKey[?]], Opt[cborDiscriminator[?]], List[Field[?]],
List[CborKeyInfo[?]], Array[GenCodec.OOOFieldsObjectCodec[?]],
Array[OOOFieldsObjectCodec[?]], InputMetadata[?], BIterable[?],
Transformed[?, ?].

Kind-parameter declarations (trait PolyCodec[C[_]], abstract class
HasPolyGenCodec[C[_]], abstract class HasPolyGenObjectCodec[C[_]],
trait PolyObjectCodec[C[_]], abstract class HasPolyGenObjectCodecWithDeps[D, C[_]],
abstract class HasPolyGenCodecWithDeps[D, C[_]], trait GadtCodec[C[_]],
abstract class HasGadtCodec[C[_]], trait CborAdtPolyInstances[C[_]],
abstract class HasPolyCborCodec[C[_]]) preserved verbatim per Pitfall 3.
---
 .../commons/serialization/FieldValues.scala      |  2 +-
 .../commons/serialization/GenCodec.scala         |  4 ++--
 .../commons/serialization/InputOutput.scala      |  4 ++--
 .../serialization/cbor/CborAdtMetadata.scala     | 16 ++++++++--------
 .../commons/serialization/cbor/CborOutput.scala  |  2 +-
 .../serialization/json/JsonStringOutput.scala    |  2 +-
 .../commons/serialization/macroCodecs.scala      | 16 ++++++++--------
 .../commons/serialization/wrappers.scala         |  2 +-
 8 files changed, 24 insertions(+), 24 deletions(-)

diff --git a/core/src/main/scala/com/avsystem/commons/serialization/FieldValues.scala b/core/src/main/scala/com/avsystem/commons/serialization/FieldValues.scala
index f40b42f6a..fa5a6a69f 100644
--- a/core/src/main/scala/com/avsystem/commons/serialization/FieldValues.scala
+++ b/core/src/main/scala/com/avsystem/commons/serialization/FieldValues.scala
@@ -12,7 +12,7 @@ object FieldValues {
 }
 final class FieldValues(
   private val fieldNames: Array[String],
-  codecs: Array[GenCodec[_]],
+  codecs: Array[GenCodec[?]],
   ofWhat: OptArg[String] = OptArg.Empty,
 ) {
 
diff --git a/core/src/main/scala/com/avsystem/commons/serialization/GenCodec.scala b/core/src/main/scala/com/avsystem/commons/serialization/GenCodec.scala
index 97c3eef3b..111e866f0 100644
--- a/core/src/main/scala/com/avsystem/commons/serialization/GenCodec.scala
+++ b/core/src/main/scala/com/avsystem/commons/serialization/GenCodec.scala
@@ -331,8 +331,8 @@ object GenCodec extends RecursiveAutoCodecs with TupleGenCodecs {
     }
   }
 
-  def underlyingCodec(codec: GenCodec[_]): GenCodec[_] = codec match {
-    case tc: Transformed[_, _] => underlyingCodec(tc.wrapped)
+  def underlyingCodec(codec: GenCodec[?]): GenCodec[?] = codec match {
+    case tc: Transformed[?, ?] => underlyingCodec(tc.wrapped)
     case _ => codec
   }
 
diff --git a/core/src/main/scala/com/avsystem/commons/serialization/InputOutput.scala b/core/src/main/scala/com/avsystem/commons/serialization/InputOutput.scala
index 62c77154e..486cba737 100644
--- a/core/src/main/scala/com/avsystem/commons/serialization/InputOutput.scala
+++ b/core/src/main/scala/com/avsystem/commons/serialization/InputOutput.scala
@@ -74,7 +74,7 @@ trait Output extends Any with AcceptsCustomEvents {
     * [[com.avsystem.commons.serialization.InputMetadata InputMetadata]] identifier. If this method returns `false` then
     * this `Output` does not support this medatata type and codec should fall back to some other serialization strategy.
     */
-  def keepsMetadata(metadata: InputMetadata[_]): Boolean = false
+  def keepsMetadata(metadata: InputMetadata[?]): Boolean = false
 
   /** This ugly workaround has been introduced when standard `Option` encoding changed from zero-or-one element list
     * encoding to unwrapped-or-null encoding which effectively disallowed serializing `null` and `Some(null)`. If some
@@ -168,7 +168,7 @@ trait SequentialOutput extends Any with AcceptsCustomEvents {
   /** Based on given collection's `knownSize` and [[sizePolicy]], declares the size of this output as size of this
     * collection if it is either cheap or required to do so.
     */
-  final def declareSizeOf(coll: BIterable[_]): Unit = sizePolicy match {
+  final def declareSizeOf(coll: BIterable[?]): Unit = sizePolicy match {
     case SizePolicy.Ignored =>
     case SizePolicy.Optional =>
       coll.knownSize match {
diff --git a/core/src/main/scala/com/avsystem/commons/serialization/cbor/CborAdtMetadata.scala b/core/src/main/scala/com/avsystem/commons/serialization/cbor/CborAdtMetadata.scala
index b29a238de..63a1822cc 100644
--- a/core/src/main/scala/com/avsystem/commons/serialization/cbor/CborAdtMetadata.scala
+++ b/core/src/main/scala/com/avsystem/commons/serialization/cbor/CborAdtMetadata.scala
@@ -77,7 +77,7 @@ object CborAdtMetadata extends AdtMetadataCompanion[CborAdtMetadata] {
   final class CborKeyInfo[T](
     @reifyName val sourceName: String,
     @optional @reifyAnnot val nameAnnot: Opt[name],
-    @optional @reifyAnnot val cborKey: Opt[cborKey[_]],
+    @optional @reifyAnnot val cborKey: Opt[cborKey[?]],
   ) {
     val stringKey: String = nameAnnot.fold(sourceName)(_.name)
     val rawKey: RawCbor = cborKey.fold(CborOutput.writeRawCbor(stringKey))(_.rawKey)
@@ -86,9 +86,9 @@ object CborAdtMetadata extends AdtMetadataCompanion[CborAdtMetadata] {
   @positioned(positioned.here)
   final class Union[T](
     @reifyName val sourceName: String,
-    @optional @reifyAnnot val discriminator: Opt[cborDiscriminator[_]],
+    @optional @reifyAnnot val discriminator: Opt[cborDiscriminator[?]],
     @optional @reifyAnnot val flattenAnnot: Opt[flatten],
-    @multi @adtCaseMetadata val cases: List[Case[_]],
+    @multi @adtCaseMetadata val cases: List[Case[?]],
   ) extends CborAdtMetadata[T] { union =>
     private val caseNamesKeyCodec =
       new MappingCborKeyCodec(cases.map(_.keyInfo))
@@ -106,7 +106,7 @@ object CborAdtMetadata extends AdtMetadataCompanion[CborAdtMetadata] {
             nestedCodec.caseNames,
             nestedCodec.cases,
           ) {
-            def caseDependencies: Array[GenCodec[_]] =
+            def caseDependencies: Array[GenCodec[?]] =
               (nestedCodec.caseDependencies.iterator zip union.cases.iterator).map {
                 case (caseCodec: ApplyUnapplyCodec[Any @unchecked], theCase: CborAdtMetadata.Record[Any @unchecked]) =>
                   theCase.adjustCodec(caseCodec)
@@ -137,9 +137,9 @@ object CborAdtMetadata extends AdtMetadataCompanion[CborAdtMetadata] {
             override protected def doReadCaseName(input: Input): String =
               input.readCustom(RawCbor).map(caseNamesKeyCodec.strKeys).getOrElse(super.doReadCaseName(input))
 
-            def oooDependencies: Array[GenCodec[_]] = flatCodec.oooDependencies
+            def oooDependencies: Array[GenCodec[?]] = flatCodec.oooDependencies
 
-            def caseDependencies: Array[GenCodec.OOOFieldsObjectCodec[_]] =
+            def caseDependencies: Array[GenCodec.OOOFieldsObjectCodec[?]] =
               (flatCodec.caseDependencies.iterator zip union.cases.iterator).map {
                 case (caseCodec: ApplyUnapplyCodec[Any @unchecked], theCase: CborAdtMetadata.Record[Any @unchecked]) =>
                   theCase.adjustFlatCaseCodec(caseCodec)
@@ -175,7 +175,7 @@ object CborAdtMetadata extends AdtMetadataCompanion[CborAdtMetadata] {
   @positioned(positioned.here)
   final class Record[T](
     @composite val keyInfo: CborKeyInfo[T],
-    @multi @adtParamMetadata val fields: List[Field[_]],
+    @multi @adtParamMetadata val fields: List[Field[?]],
   ) extends Case[T] {
     private val keyCodec = new MappingCborKeyCodec(fields.map(_.keyInfo))
 
@@ -223,7 +223,7 @@ object CborAdtMetadata extends AdtMetadataCompanion[CborAdtMetadata] {
     def validate(): Unit = ()
   }
 
-  private class MappingCborKeyCodec(keyInfos: List[CborKeyInfo[_]]) extends CborKeyCodec {
+  private class MappingCborKeyCodec(keyInfos: List[CborKeyInfo[?]]) extends CborKeyCodec {
     val rawKeys: Map[String, RawCbor] =
       keyInfos.mkMap(_.stringKey, _.rawKey)
     val strKeys: Map[RawCbor, String] =
diff --git a/core/src/main/scala/com/avsystem/commons/serialization/cbor/CborOutput.scala b/core/src/main/scala/com/avsystem/commons/serialization/cbor/CborOutput.scala
index 2a5c2544f..0b3458aab 100644
--- a/core/src/main/scala/com/avsystem/commons/serialization/cbor/CborOutput.scala
+++ b/core/src/main/scala/com/avsystem/commons/serialization/cbor/CborOutput.scala
@@ -172,7 +172,7 @@ class CborOutput(out: DataOutput, keyCodec: CborKeyCodec, sizePolicy: SizePolicy
         super.writeCustom(typeMarker, value)
     }
 
-  override def keepsMetadata(metadata: InputMetadata[_]): Boolean = metadata match {
+  override def keepsMetadata(metadata: InputMetadata[?]): Boolean = metadata match {
     case InitialByte | Tags => true
     case _ => super.keepsMetadata(metadata)
   }
diff --git a/core/src/main/scala/com/avsystem/commons/serialization/json/JsonStringOutput.scala b/core/src/main/scala/com/avsystem/commons/serialization/json/JsonStringOutput.scala
index bce129f4b..c3a0c7a25 100644
--- a/core/src/main/scala/com/avsystem/commons/serialization/json/JsonStringOutput.scala
+++ b/core/src/main/scala/com/avsystem/commons/serialization/json/JsonStringOutput.scala
@@ -123,7 +123,7 @@ final class JsonStringOutput(builder: JStringBuilder, options: JsonOptions = Jso
 
   def writeRawJson(json: String): Unit = builder.append(json)
 
-  override def keepsMetadata(metadata: InputMetadata[_]): Boolean =
+  override def keepsMetadata(metadata: InputMetadata[?]): Boolean =
     metadata == JsonType
 
   override def writeCustom[T](typeMarker: TypeMarker[T], value: T): Boolean =
diff --git a/core/src/main/scala/com/avsystem/commons/serialization/macroCodecs.scala b/core/src/main/scala/com/avsystem/commons/serialization/macroCodecs.scala
index 251ed0237..7a395fa95 100644
--- a/core/src/main/scala/com/avsystem/commons/serialization/macroCodecs.scala
+++ b/core/src/main/scala/com/avsystem/commons/serialization/macroCodecs.scala
@@ -24,7 +24,7 @@ abstract class ApplyUnapplyCodec[T](
 ) extends ErrorReportingCodec[T]
     with OOOFieldsObjectCodec[T] {
 
-  protected def dependencies: Array[GenCodec[_]]
+  protected def dependencies: Array[GenCodec[?]]
   protected def instantiate(fieldValues: FieldValues): T
 
   private[this] lazy val deps = dependencies
@@ -130,7 +130,7 @@ abstract class SealedHierarchyCodec[T](
   val typeRepr: String,
   val nullable: Boolean,
   val caseNames: Array[String],
-  val cases: Array[Class[_]],
+  val cases: Array[Class[?]],
 ) extends ErrorReportingCodec[T]
     with ObjectCodec[T] {
 
@@ -149,10 +149,10 @@ abstract class NestedSealedHierarchyCodec[T](
   typeRepr: String,
   nullable: Boolean,
   caseNames: Array[String],
-  cases: Array[Class[_]],
+  cases: Array[Class[?]],
 ) extends SealedHierarchyCodec[T](typeRepr, nullable, caseNames, cases) {
 
-  def caseDependencies: Array[GenCodec[_]]
+  def caseDependencies: Array[GenCodec[?]]
 
   private[this] lazy val caseDeps = caseDependencies
 
@@ -177,7 +177,7 @@ abstract class FlatSealedHierarchyCodec[T](
   typeRepr: String,
   nullable: Boolean,
   caseNames: Array[String],
-  cases: Array[Class[_]],
+  cases: Array[Class[?]],
   val oooFieldNames: Array[String],
   val caseDependentFieldNames: Set[String],
   override val caseFieldName: String,
@@ -185,8 +185,8 @@ abstract class FlatSealedHierarchyCodec[T](
   val defaultCaseTransient: Boolean,
 ) extends SealedHierarchyCodec[T](typeRepr, nullable, caseNames, cases) {
 
-  def oooDependencies: Array[GenCodec[_]]
-  def caseDependencies: Array[OOOFieldsObjectCodec[_]]
+  def oooDependencies: Array[GenCodec[?]]
+  def caseDependencies: Array[OOOFieldsObjectCodec[?]]
 
   private[this] lazy val oooDeps = oooDependencies
   private[this] lazy val caseDeps = caseDependencies
@@ -386,7 +386,7 @@ abstract class JavaBuilderBasedCodec[T, B](
 ) extends ErrorReportingCodec[T]
     with GenCodec.ObjectCodec[T] {
 
-  protected def dependencies: Array[GenCodec[_]]
+  protected def dependencies: Array[GenCodec[?]]
 
   private lazy val deps = dependencies
 
diff --git a/core/src/main/scala/com/avsystem/commons/serialization/wrappers.scala b/core/src/main/scala/com/avsystem/commons/serialization/wrappers.scala
index 7950adac7..e04abfe14 100644
--- a/core/src/main/scala/com/avsystem/commons/serialization/wrappers.scala
+++ b/core/src/main/scala/com/avsystem/commons/serialization/wrappers.scala
@@ -68,7 +68,7 @@ abstract class OutputWrapper extends Output {
   def writeList(): ListOutput = wrapped.writeList()
   def writeObject(): ObjectOutput = wrapped.writeObject()
   override def writeCustom[T](typeMarker: TypeMarker[T], value: T): Boolean = wrapped.writeCustom(typeMarker, value)
-  override def keepsMetadata(metadata: InputMetadata[_]): Boolean = wrapped.keepsMetadata(metadata)
+  override def keepsMetadata(metadata: InputMetadata[?]): Boolean = wrapped.keepsMetadata(metadata)
   override def customEvent[T](marker: CustomEventMarker[T], value: T): Boolean = wrapped.customEvent(marker, value)
   override def legacyOptionEncoding: Boolean = wrapped.legacyOptionEncoding
 }

From 87fe16597cf0cde630debb9a25586e423cbac6e1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bart=C5=82omiej=20Kozak?= <b.kozak@avsystem.com>
Date: Mon, 1 Jun 2026 19:41:57 +0200
Subject: [PATCH 2/6] =?UTF-8?q?refactor(scala-3,core):=20F[=5F]=20?=
 =?UTF-8?q?=E2=86=92=20F[=3F]=20in=20applied=20positions=20(rpc)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Targeted rewrites: Iterator[?], List[ParamMetadata[?]],
Map[String, FunctionSignature[?]], Map[String, GetterSignature[?]].

Kind-parameter declarations (def materialize[M[_], Real],
def materializeForApi[M[_], Real], trait RpcMetadataCompanion[M[_]],
trait ApiMetadataCompanion[M[_]]) preserved verbatim per Pitfall 3.
---
 .../scala/com/avsystem/commons/rpc/AsRawReal.scala   |  2 +-
 .../com/avsystem/commons/rpc/RPCFramework.scala      |  2 +-
 .../avsystem/commons/rpc/StandardRPCFramework.scala  | 12 ++++++------
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/core/src/main/scala/com/avsystem/commons/rpc/AsRawReal.scala b/core/src/main/scala/com/avsystem/commons/rpc/AsRawReal.scala
index 760123571..b72b63fbd 100644
--- a/core/src/main/scala/com/avsystem/commons/rpc/AsRawReal.scala
+++ b/core/src/main/scala/com/avsystem/commons/rpc/AsRawReal.scala
@@ -119,7 +119,7 @@ object RpcMetadata {
   // TODO[scala3-port]: RpcMetadata.auto (Scala 2 macro def) (L)
   def auto[T]: T = ???
 
-  def nextInstance[T](it: Iterator[_], description: String): T =
+  def nextInstance[T](it: Iterator[?], description: String): T =
     if (it.hasNext) it.next().asInstanceOf[T]
     else throw new NoSuchElementException(s"typeclass instance for $description was not provided")
 }
diff --git a/core/src/main/scala/com/avsystem/commons/rpc/RPCFramework.scala b/core/src/main/scala/com/avsystem/commons/rpc/RPCFramework.scala
index 6d4b898a8..2fc4ecdc4 100644
--- a/core/src/main/scala/com/avsystem/commons/rpc/RPCFramework.scala
+++ b/core/src/main/scala/com/avsystem/commons/rpc/RPCFramework.scala
@@ -58,7 +58,7 @@ trait RPCFramework {
   trait Signature {
     @reifyName def name: String
     @multi
-    @rpcParamMetadata def paramMetadata: List[ParamMetadata[_]]
+    @rpcParamMetadata def paramMetadata: List[ParamMetadata[?]]
     @reifyAnnot
     @multi def annotations: List[MetadataAnnotation]
   }
diff --git a/core/src/main/scala/com/avsystem/commons/rpc/StandardRPCFramework.scala b/core/src/main/scala/com/avsystem/commons/rpc/StandardRPCFramework.scala
index c652f528f..c0e8720c5 100644
--- a/core/src/main/scala/com/avsystem/commons/rpc/StandardRPCFramework.scala
+++ b/core/src/main/scala/com/avsystem/commons/rpc/StandardRPCFramework.scala
@@ -16,7 +16,7 @@ trait ProcedureRPCFramework extends RPCFramework {
 
   case class ProcedureSignature(
     name: String,
-    paramMetadata: List[ParamMetadata[_]],
+    paramMetadata: List[ParamMetadata[?]],
     annotations: List[MetadataAnnotation],
   ) extends Signature
       with TypedMetadata[Unit]
@@ -34,7 +34,7 @@ trait FunctionRPCFramework extends RPCFramework {
 
   case class FunctionSignature[T](
     name: String,
-    paramMetadata: List[ParamMetadata[_]],
+    paramMetadata: List[ParamMetadata[?]],
     annotations: List[MetadataAnnotation],
     @infer resultTypeMetadata: ResultTypeMetadata[T],
   ) extends Signature
@@ -58,7 +58,7 @@ trait GetterRPCFramework extends RPCFramework {
 
   case class GetterSignature[T](
     name: String,
-    paramMetadata: List[ParamMetadata[_]],
+    paramMetadata: List[ParamMetadata[?]],
     annotations: List[MetadataAnnotation],
     @infer @checked resultMetadata: RPCMetadata.Lazy[T],
   ) extends Signature
@@ -75,8 +75,8 @@ trait StandardRPCFramework extends GetterRPCFramework with FunctionRPCFramework
     @reifyName name: String,
     @reifyAnnot @multi annotations: List[MetadataAnnotation],
     @multi @verbatim @rpcMethodMetadata procedureSignatures: Map[String, ProcedureSignature],
-    @multi @rpcMethodMetadata functionSignatures: Map[String, FunctionSignature[_]],
-    @multi @rpcMethodMetadata getterSignatures: Map[String, GetterSignature[_]],
+    @multi @rpcMethodMetadata functionSignatures: Map[String, FunctionSignature[?]],
+    @multi @rpcMethodMetadata getterSignatures: Map[String, GetterSignature[?]],
   )
   object RPCMetadata extends RpcMetadataCompanion[RPCMetadata]
 }
@@ -91,7 +91,7 @@ trait OneWayRPCFramework extends GetterRPCFramework with ProcedureRPCFramework {
     @reifyName name: String,
     @reifyAnnot @multi annotations: List[MetadataAnnotation],
     @multi @verbatim @rpcMethodMetadata procedureSignatures: Map[String, ProcedureSignature],
-    @multi @rpcMethodMetadata getterSignatures: Map[String, GetterSignature[_]],
+    @multi @rpcMethodMetadata getterSignatures: Map[String, GetterSignature[?]],
   )
   object RPCMetadata extends RpcMetadataCompanion[RPCMetadata]
 }

From e8e4d2e98118b89aa845a05b94cbdcf594992499 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bart=C5=82omiej=20Kozak?= <b.kozak@avsystem.com>
Date: Mon, 1 Jun 2026 19:42:45 +0200
Subject: [PATCH 3/6] =?UTF-8?q?refactor(scala-3,core):=20F[=5F]=20?=
 =?UTF-8?q?=E2=86=92=20F[=3F]=20in=20applied=20positions=20(misc=20+=20di)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Targeted rewrites: GenKeyCodec[TypeString[?]], GenCodec[TypeString[?]],
GenKeyCodec[JavaClassName[?]], GenCodec[JavaClassName[?]], Entry[K, ?]*,
Component[?], AtomicReference[?], MHashMap[Component[?], ...],
MHashSet[Component[?]], AtomicReference[Future[?]].

Kind-parameter declarations (class TypedMap[K[_]], case class Entry[K[_], T],
def pairToEntry[K[_], T], def empty[K[_]], def apply[K[_]],
trait GenCodecMapping[K[_]], def typedMapCodec[K[_]],
def instancesFor[TC[_], T], case class SelfInstance[C[_]],
def materialize[C[_]], trait AdtMetadataCompanion[M[_]],
trait MetadataCompanion[M[_]], type MColBuilder[Elem, +Col[_]],
trait TupleDerivation[C[_]]) preserved verbatim per Pitfall 3.
---
 .../com/avsystem/commons/di/Component.scala   | 26 +++++++++----------
 .../com/avsystem/commons/di/Components.scala  |  2 +-
 .../avsystem/commons/misc/TypeString.scala    | 16 ++++++------
 .../com/avsystem/commons/misc/TypedMap.scala  |  2 +-
 4 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/core/src/main/scala/com/avsystem/commons/di/Component.scala b/core/src/main/scala/com/avsystem/commons/di/Component.scala
index 0551161ea..9a3b8b7de 100644
--- a/core/src/main/scala/com/avsystem/commons/di/Component.scala
+++ b/core/src/main/scala/com/avsystem/commons/di/Component.scala
@@ -8,10 +8,10 @@ import java.util.concurrent.atomic.AtomicReference
 import scala.annotation.compileTimeOnly
 import scala.annotation.unchecked.uncheckedVariance
 
-case class ComponentInitializationException(component: Component[_], cause: Throwable)
+case class ComponentInitializationException(component: Component[?], cause: Throwable)
   extends Exception(s"failed to initialize component ${component.info}", cause)
 
-case class DependencyCycleException(cyclePath: List[Component[_]])
+case class DependencyCycleException(cyclePath: List[Component[?]])
   extends Exception(
     s"component dependency cycle detected:\n${cyclePath.iterator.map(_.info).map("  " + _).mkString(" ->\n")}"
   )
@@ -46,7 +46,7 @@ object ComponentInfo {
   */
 final class Component[+T](
   val info: ComponentInfo,
-  deps: => IndexedSeq[Component[_]],
+  deps: => IndexedSeq[Component[?]],
   creator: IndexedSeq[Any] => ExecutionContext => Future[T],
   destroyer: DestroyFunction[T] = Component.emptyDestroy,
   cachedStorage: Opt[AtomicReference[Future[T]]] = Opt.Empty,
@@ -61,18 +61,18 @@ final class Component[+T](
   /** Returns dependencies of this component extracted from the component definition. You can use this to inspect the
     * dependency graph without initializing any components.
     */
-  lazy val dependencies: IndexedSeq[Component[_]] = deps
+  lazy val dependencies: IndexedSeq[Component[?]] = deps
 
   private[this] val storage: AtomicReference[Future[T]] =
     cachedStorage.getOrElse(new AtomicReference)
 
-  private def sameStorage(otherStorage: AtomicReference[_]): Boolean =
+  private def sameStorage(otherStorage: AtomicReference[?]): Boolean =
     storage eq otherStorage
 
   // equality based on storage identity is important for cycle detection with cached components
   override def hashCode(): Int = storage.hashCode()
   override def equals(obj: Any): Boolean = obj match {
-    case c: Component[_] => c.sameStorage(storage)
+    case c: Component[?] => c.sameStorage(storage)
     case _ => false
   }
 
@@ -106,7 +106,7 @@ final class Component[+T](
 
   /** Forces a dependency on another component or components.
     */
-  def dependsOn(moreDeps: Component[_]*): Component[T] =
+  def dependsOn(moreDeps: Component[?]*): Component[T] =
     new Component(info, deps ++ moreDeps, creator, destroyer, cachedStorage)
 
   /** Specifies an asynchronous function that will be used to destroy this component, i.e. free up any resources that
@@ -189,7 +189,7 @@ object Component {
   def async[T](definition: => T): ExecutionContext => Future[T] =
     implicit ctx => Future(definition)
 
-  def validateAll(components: Seq[Component[_]]): Unit =
+  def validateAll(components: Seq[Component[?]]): Unit =
     GraphUtils.dfs(components)(
       _.dependencies.toList,
       onCycle = (node, stack) => {
@@ -203,9 +203,9 @@ object Component {
     * ensured that a component is only destroyed after all components that depend on it are destroyed (reverse
     * initialization order). Independent components are destroyed in parallel, using given `ExecutionContext`.
     */
-  def destroyAll(components: Seq[Component[_]])(implicit ec: ExecutionContext): Future[Unit] = {
-    val reverseGraph = new MHashMap[Component[_], MListBuffer[Component[_]]]
-    val terminals = new MHashSet[Component[_]]
+  def destroyAll(components: Seq[Component[?]])(implicit ec: ExecutionContext): Future[Unit] = {
+    val reverseGraph = new MHashMap[Component[?], MListBuffer[Component[?]]]
+    val terminals = new MHashSet[Component[?]]
     GraphUtils.dfs(components)(
       _.dependencies.toList,
       onEnter = { (c, _) =>
@@ -218,9 +218,9 @@ object Component {
           terminals += c
       },
     )
-    val destroyFutures = new MHashMap[Component[_], Future[Unit]]
+    val destroyFutures = new MHashMap[Component[?], Future[Unit]]
 
-    def doDestroy(c: Component[_]): Future[Unit] =
+    def doDestroy(c: Component[?]): Future[Unit] =
       destroyFutures.getOrElseUpdate(c, Future.traverse(reverseGraph(c))(doDestroy).flatMap(_ => c.doDestroy))
 
     Future.traverse(reverseGraph.keys)(doDestroy).toUnit
diff --git a/core/src/main/scala/com/avsystem/commons/di/Components.scala b/core/src/main/scala/com/avsystem/commons/di/Components.scala
index d635108b9..c4bfb0d89 100644
--- a/core/src/main/scala/com/avsystem/commons/di/Components.scala
+++ b/core/src/main/scala/com/avsystem/commons/di/Components.scala
@@ -29,7 +29,7 @@ trait Components extends ComponentsLowPrio {
   protected def asyncSingleton[T](definition: ExecutionContext => Future[T])(implicit sourceInfo: SourceInfo)
     : Component[T] = ???
 
-  private lazy val singletonsCache = new ConcurrentHashMap[ComponentInfo, AtomicReference[Future[_]]]
+  private lazy val singletonsCache = new ConcurrentHashMap[ComponentInfo, AtomicReference[Future[?]]]
 
   protected def cached[T](component: Component[T], freshInfo: ComponentInfo): Component[T] = {
     val cacheStorage =
diff --git a/core/src/main/scala/com/avsystem/commons/misc/TypeString.scala b/core/src/main/scala/com/avsystem/commons/misc/TypeString.scala
index a4de4ac93..e872f1841 100644
--- a/core/src/main/scala/com/avsystem/commons/misc/TypeString.scala
+++ b/core/src/main/scala/com/avsystem/commons/misc/TypeString.scala
@@ -31,11 +31,11 @@ object TypeString {
   // TODO[scala3-port]: TypeString.materialize (Scala 2 macro def) (L)
   implicit def materialize[T]: TypeString[T] = ???
 
-  implicit val keyCodec: GenKeyCodec[TypeString[_]] =
-    GenKeyCodec.create[TypeString[_]](new TypeString(_), _.value)
+  implicit val keyCodec: GenKeyCodec[TypeString[?]] =
+    GenKeyCodec.create[TypeString[?]](new TypeString(_), _.value)
 
-  implicit val codec: GenCodec[TypeString[_]] =
-    GenCodec.nonNullSimple[TypeString[_]](i => new TypeString(i.readString()), (o, ts) => o.writeString(ts.value))
+  implicit val codec: GenCodec[TypeString[?]] =
+    GenCodec.nonNullSimple[TypeString[?]](i => new TypeString(i.readString()), (o, ts) => o.writeString(ts.value))
 }
 
 /** Typeclass that contains JVM fully qualified class name corresponding to given type. `JavaClassName.of[T]` is always
@@ -80,11 +80,11 @@ object JavaClassName extends JavaClassNameLowPrio {
     new JavaClassName("[" + elementName)
   }
 
-  implicit val keyCodec: GenKeyCodec[JavaClassName[_]] =
-    GenKeyCodec.create[JavaClassName[_]](new JavaClassName(_), _.value)
+  implicit val keyCodec: GenKeyCodec[JavaClassName[?]] =
+    GenKeyCodec.create[JavaClassName[?]](new JavaClassName(_), _.value)
 
-  implicit val codec: GenCodec[JavaClassName[_]] =
-    GenCodec.nonNullSimple[JavaClassName[_]](i => new JavaClassName(i.readString()), (o, ts) => o.writeString(ts.value))
+  implicit val codec: GenCodec[JavaClassName[?]] =
+    GenCodec.nonNullSimple[JavaClassName[?]](i => new JavaClassName(i.readString()), (o, ts) => o.writeString(ts.value))
 }
 trait JavaClassNameLowPrio { this: JavaClassName.type =>
   // TODO[scala3-port]: JavaClassName.materialize (Scala 2 macro def) (L)
diff --git a/core/src/main/scala/com/avsystem/commons/misc/TypedMap.scala b/core/src/main/scala/com/avsystem/commons/misc/TypedMap.scala
index f34d3fed6..248d58d31 100644
--- a/core/src/main/scala/com/avsystem/commons/misc/TypedMap.scala
+++ b/core/src/main/scala/com/avsystem/commons/misc/TypedMap.scala
@@ -78,7 +78,7 @@ object TypedMap {
   def empty[K[_]]: TypedMap[K] =
     new TypedMap[K](Map.empty)
 
-  def apply[K[_]](entries: Entry[K, _]*): TypedMap[K] = {
+  def apply[K[_]](entries: Entry[K, ?]*): TypedMap[K] = {
     val raw = Map.newBuilder[K[Any], Any]
     entries.foreach(e => raw += e.pair.asInstanceOf[(K[Any], Any)])
     new TypedMap[K](raw.result())

From 45b83ecb806be1c93396f738351aa4fc53c25e14 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bart=C5=82omiej=20Kozak?= <b.kozak@avsystem.com>
Date: Mon, 1 Jun 2026 19:43:53 +0200
Subject: [PATCH 4/6] =?UTF-8?q?refactor(scala-3,mongo):=20F[=5F]=20?=
 =?UTF-8?q?=E2=86=92=20F[=3F]=20in=20applied=20positions=20(sweep)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Translated from origin/master@848b8e9e (mongo subset).

Targeted rewrites: InputMetadata[?], MongoQueryOperator[?], MongoFilter[?],
List[Case[?]], Map[Class[?], Case[?]], Map[Class[?], UnionFormat[?]],
MHashMap[Class[?], (SealedParent[?], MListBuffer[Case[?]])],
List[SealedParent[?]], Opt[Field[?]], List[Field[?]],
Map[String, Field[?]], MongoCollection[?].

Kind-parameter declarations (final case class TypedMapFormat[K[_]],
implicit def typedMapFormat[K[_]], implicit class typedMapFormatOps[K[_]],
trait MongoPolyAdtInstances[D[_]], abstract class
AbstractMongoPolyDataCompanion[Implicits, D[_]], abstract class
MongoPolyDataCompanion[D[_]], implicit class TypedMapRefOps[E, K[_]],
trait MongoFormatMapping[K[_]]) preserved verbatim per Pitfall 3.
---
 .../commons/mongo/BsonInputOutput.scala       |  2 +-
 .../mongo/typed/FilterDocBuilder.scala        |  4 +--
 .../commons/mongo/typed/MongoFormat.scala     | 28 +++++++++----------
 .../mongo/typed/TypedMongoCollection.scala    |  8 +++---
 4 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/BsonInputOutput.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/BsonInputOutput.scala
index b1122e958..ec14ad994 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/BsonInputOutput.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/BsonInputOutput.scala
@@ -111,7 +111,7 @@ trait BsonOutput extends Any with OutputAndSimpleOutput {
       case Opt.Empty => writeBinary(BsonOutput.bigDecimalBytes(bigDecimal))
     }
 
-  override def keepsMetadata(metadata: InputMetadata[_]): Boolean =
+  override def keepsMetadata(metadata: InputMetadata[?]): Boolean =
     BsonTypeMetadata == metadata
 
   override def writeCustom[T](typeMarker: TypeMarker[T], value: T): Boolean =
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/FilterDocBuilder.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/FilterDocBuilder.scala
index b987dd4db..a841795e3 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/FilterDocBuilder.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/FilterDocBuilder.scala
@@ -36,7 +36,7 @@ private final class FilterDocBuilder(prefixPath: Opt[String], filterDocs: BsonAr
       addImpliedFilters(prefix)
   }
 
-  private def addOperator(op: MongoQueryOperator[_]): Unit = {
+  private def addOperator(op: MongoQueryOperator[?]): Unit = {
     val path = prefixPath.getOrElse(
       throw new IllegalArgumentException(
         "cannot add MongoOperatorsFilter to toplevel filter document without prefix path"
@@ -62,7 +62,7 @@ private final class FilterDocBuilder(prefixPath: Opt[String], filterDocs: BsonAr
     loop(0)
   }
 
-  def addFilter(filter: MongoFilter[_]): Unit = filter match {
+  def addFilter(filter: MongoFilter[?]): Unit = filter match {
     case Empty() =>
 
     case And(filters) =>
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoFormat.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoFormat.scala
index 97b9c499f..a612967fc 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoFormat.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoFormat.scala
@@ -175,14 +175,14 @@ object MongoAdtFormat extends AdtMetadataCompanion[MongoAdtFormat] {
     @infer val codec: GenObjectCodec[T],
     @infer val dataClassTag: ClassTag[T],
     @reifyAnnot val flattenAnnot: flatten,
-    @multi @adtCaseMetadata val cases: List[Case[_]],
+    @multi @adtCaseMetadata val cases: List[Case[?]],
   ) extends MongoAdtFormat[T] {
 
-    lazy val casesByClass: Map[Class[_], Case[_]] =
+    lazy val casesByClass: Map[Class[?], Case[?]] =
       cases.toMapBy(_.classTag.runtimeClass)
 
-    lazy val subUnionsByClass: Map[Class[_], UnionFormat[_]] = {
-      val casesPerClass = new MHashMap[Class[_], (SealedParent[_], MListBuffer[Case[_]])]
+    lazy val subUnionsByClass: Map[Class[?], UnionFormat[?]] = {
+      val casesPerClass = new MHashMap[Class[?], (SealedParent[?], MListBuffer[Case[?]])]
       for {
         cse <- cases
         subUnion <- cse.sealedParents
@@ -206,7 +206,7 @@ object MongoAdtFormat extends AdtMetadataCompanion[MongoAdtFormat] {
     }
 
     def fieldRefFor[E, T0](prefix: MongoRef[E, T], scalaFieldName: String): MongoPropertyRef[E, T0] = {
-      @tailrec def loop(cases: List[Case[_]], rawName: Opt[String]): Unit = cases match {
+      @tailrec def loop(cases: List[Case[?]], rawName: Opt[String]): Unit = cases match {
         case cse :: tail =>
           val field = cse
             .getField(scalaFieldName)
@@ -228,7 +228,7 @@ object MongoAdtFormat extends AdtMetadataCompanion[MongoAdtFormat] {
     }
 
     private def subtypeInfo[T0](subclass: Class[T0]): (List[String], MongoAdtFormat[T0]) = {
-      def asAdtFormat[C](cse: Case[_], codec: GenObjectCodec[_]): MongoAdtFormat[C] =
+      def asAdtFormat[C](cse: Case[?], codec: GenObjectCodec[?]): MongoAdtFormat[C] =
         cse.asInstanceOf[Case[C]].asAdtFormat(codec.asInstanceOf[GenObjectCodec[C]])
 
       casesByClass
@@ -282,9 +282,9 @@ object MongoAdtFormat extends AdtMetadataCompanion[MongoAdtFormat] {
   sealed trait Case[T] extends TypedMetadata[T] {
     def info: GenCaseInfo[T]
     def classTag: ClassTag[T]
-    def sealedParents: List[SealedParent[_]]
+    def sealedParents: List[SealedParent[?]]
 
-    def getField(scalaFieldName: String): Opt[Field[_]]
+    def getField(scalaFieldName: String): Opt[Field[?]]
     def fieldRefFor[E, T0](prefix: MongoRef[E, T], scalaFieldName: String): MongoPropertyRef[E, T0]
 
     def asAdtFormat(codec: GenObjectCodec[T]): MongoAdtFormat[T]
@@ -294,8 +294,8 @@ object MongoAdtFormat extends AdtMetadataCompanion[MongoAdtFormat] {
   final class RecordCase[T](
     @composite val info: GenCaseInfo[T],
     @infer val classTag: ClassTag[T],
-    @multi @adtParamMetadata val fields: List[Field[_]],
-    @multi @adtCaseSealedParentMetadata val sealedParents: List[SealedParent[_]],
+    @multi @adtParamMetadata val fields: List[Field[?]],
+    @multi @adtCaseSealedParentMetadata val sealedParents: List[SealedParent[?]],
   ) extends Case[T] {
     def asAdtFormat(codec: GenObjectCodec[T]): MongoAdtFormat[T] =
       new RecordFormat(this, codec)
@@ -303,10 +303,10 @@ object MongoAdtFormat extends AdtMetadataCompanion[MongoAdtFormat] {
     def transparentWrapper: Boolean =
       info.transparent && fields.size == 1
 
-    lazy val fieldsByScalaName: Map[String, Field[_]] =
+    lazy val fieldsByScalaName: Map[String, Field[?]] =
       fields.toMapBy(_.info.sourceName)
 
-    def getField(scalaFieldName: String): Opt[Field[_]] =
+    def getField(scalaFieldName: String): Opt[Field[?]] =
       fieldsByScalaName.getOpt(scalaFieldName)
 
     def fieldRefFor[E, T0](prefix: MongoRef[E, T], scalaFieldName: String): MongoPropertyRef[E, T0] = {
@@ -326,14 +326,14 @@ object MongoAdtFormat extends AdtMetadataCompanion[MongoAdtFormat] {
   final class SingletonCase[T](
     @composite val info: GenCaseInfo[T],
     @infer val classTag: ClassTag[T],
-    @multi @adtCaseSealedParentMetadata val sealedParents: List[SealedParent[_]],
+    @multi @adtCaseSealedParentMetadata val sealedParents: List[SealedParent[?]],
     @infer @checked val value: scala.ValueOf[T],
   ) extends Case[T] {
     def asAdtFormat(codec: GenObjectCodec[T]): MongoAdtFormat[T] =
       new SingletonFormat(this, codec)
 
     // TODO: @generated
-    def getField(scalaFieldName: String): Opt[Field[_]] = Opt.Empty
+    def getField(scalaFieldName: String): Opt[Field[?]] = Opt.Empty
 
     def fieldRefFor[E, T0](prefix: MongoRef[E, T], scalaFieldName: String): MongoPropertyRef[E, T0] =
       throw new NoSuchElementException(s"Field $scalaFieldName not found")
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/TypedMongoCollection.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/TypedMongoCollection.scala
index df5e6c24a..e8065c52a 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/TypedMongoCollection.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/TypedMongoCollection.scala
@@ -24,7 +24,7 @@ class TypedMongoCollection[E <: BaseMongoEntity] private (
     with TypedMongoUtils {
 
   def this(
-    rawCollection: MongoCollection[_],
+    rawCollection: MongoCollection[?],
     clientSession: OptArg[TypedClientSession] = OptArg.Empty,
   )(implicit meta: MongoEntityMeta[E]
   ) = this(
@@ -384,16 +384,16 @@ class TypedMongoCollection[E <: BaseMongoEntity] private (
     )
   }
 
-  @bincompat private[typed] def this(rawCollection: MongoCollection[_], format: MongoAdtFormat[E]) =
+  @bincompat private[typed] def this(rawCollection: MongoCollection[?], format: MongoAdtFormat[E]) =
     this(rawCollection)(MongoEntityMeta.bincompatMeta(format))
 
-  @bincompat private[typed] def this(rawCollection: MongoCollection[_], meta: MongoEntityMeta[E]) =
+  @bincompat private[typed] def this(rawCollection: MongoCollection[?], meta: MongoEntityMeta[E]) =
     this(rawCollection)(meta)
 }
 
 object TypedMongoCollection {
   private def mkNativeCollection[E <: BaseMongoEntity: MongoEntityMeta](
-    rawCollection: MongoCollection[_]
+    rawCollection: MongoCollection[?]
   )(implicit meta: MongoEntityMeta[E]
   ): MongoCollection[E] = {
     import meta.format._

From e1905e596b3bb1bc5169e9e4904689e96e7dfbe2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bart=C5=82omiej=20Kozak?= <b.kozak@avsystem.com>
Date: Mon, 1 Jun 2026 19:44:22 +0200
Subject: [PATCH 5/6] docs(migration): record HKT wildcard tightening
 (type-level only, no source-compat)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Slice 3.2: `_` → `?` in applied positions across core + mongo.
Kind-parameter declarations preserved. Pure type-argument-position syntax
change; downstream callers unaffected.
---
 MIGRATION.md | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/MIGRATION.md b/MIGRATION.md
index b99395701..398bab961 100644
--- a/MIGRATION.md
+++ b/MIGRATION.md
@@ -54,6 +54,10 @@ the bottom of this file. Restoration ships incrementally per feature area.
   compiles).
 - `enum` was renamed to `e` at one call site in `GenKeyCodec` (`enum` is reserved in Scala 3).
 - `@targetName` annotation added to `CloseableIterator` overloaded methods.
+- HKT wildcard `_` → `?` in applied positions (slice 3.2). Type-argument-position syntax only;
+  kind-parameter declarations (`class Foo[F[_]]`, `def baz[M[_], A]`, etc.) preserved per Scala 3.
+  Pure type-level rename — no source-compat impact for downstream callers; type-argument site syntax
+  only.
 
 ### mongo
 
@@ -63,6 +67,8 @@ the bottom of this file. Restoration ships incrementally per feature area.
   Scala 3 forbids type projections on non-concrete prefixes). Public-API signature change.
 - `BsonValueOutput.write` / `BsonValueInput.read` call sites require explicit `using` keyword.
 - `MongoPolyDataCompanion` / `TypedMapFormat` / `TypedMapRefOps` widened from `K[_]` / `D[_]` to `K[Any]` / `D[Any]`.
+- HKT wildcard `_` → `?` in applied positions (slice 3.2). Same as core entry — pure
+  type-argument-position syntax change with no source-compat impact.
 
 ### hocon
 

From 6b1a6e1ba5bd7436840294961aabefdab152a742 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bart=C5=82omiej=20Kozak?= <b.kozak@avsystem.com>
Date: Mon, 1 Jun 2026 22:16:03 +0200
Subject: [PATCH 6/6] refactor(scala-3,mongo): tighten HKT wildcards with
 bounds in applied positions
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Prior sweep handled simple [_] / [_, _] applied positions. This polish
catches remaining sites flagged by user 2026-06-01:

- DocKey[A, _] / DocKey[_, _] / DocKey[_, _ <: BsonArray] → [A, ?] / [?, ?] / [?, ? <: BsonArray]
  in Filter, Sort, Update (object-level helpers)
- BsonRef[_, T] / BsonRef[_, C[E]] / BsonRef[_, _] in mongo/core/ops/* (8 files)
- DocKey[_, _] type ascriptions in KeyGetter
- MongoRef[E, _], MongoRef[_, _], MongoPropertyRef[E, _], MongoToplevelRef[E, _]
  type ascriptions (parameter and return types only — type-patterns in case
  clauses preserved as `_` to mirror fork master shape)
- MongoProjection[E, _] type ascription in ProjectionZippers

Type-pattern wildcards in `case x: T[_, _]` clauses intentionally kept as `_`
to match fork master @ origin/master (see MongoQueryOperator, MongoUpdate,
MongoUpdateOperator, MongoRef.computePath/extractBson, MongoFormat.fieldRefFor).
Per-file fork-shape comparison done; all applied-position rewrites mirror
fork's canonical scala-3 form.

Acceptance gate: every remaining [_]/[_ <: X] in scope is either a kind-decl
position, a value-pattern wildcard, or a type-pattern in a case clause (fork-
canonical).

sbt compile Test/compile scalafmtCheckAll → exit 0, no new warnings, no
@nowarn / -Wconf added.
---
 .../com/avsystem/commons/mongo/Filter.scala   | 20 +++++++++----------
 .../com/avsystem/commons/mongo/Sort.scala     |  4 ++--
 .../com/avsystem/commons/mongo/Update.scala   |  6 +++---
 .../mongo/core/ops/BsonRefFiltering.scala     |  2 +-
 .../core/ops/BsonRefIterableFiltering.scala   |  2 +-
 .../core/ops/BsonRefIterableUpdating.scala    |  2 +-
 .../mongo/core/ops/BsonRefKeyHandling.scala   |  2 +-
 .../mongo/core/ops/BsonRefSorting.scala       |  2 +-
 .../mongo/core/ops/BsonRefUpdating.scala      |  2 +-
 .../commons/mongo/core/ops/KeyGetter.scala    |  8 ++++----
 .../mongo/typed/FilterDocBuilder.scala        |  2 +-
 .../commons/mongo/typed/MongoFilter.scala     |  2 +-
 .../commons/mongo/typed/MongoIndex.scala      |  8 ++++----
 .../commons/mongo/typed/MongoOrder.scala      | 16 +++++++--------
 .../commons/mongo/typed/MongoProjection.scala | 14 ++++++-------
 .../commons/mongo/typed/MongoRef.scala        |  2 +-
 .../commons/mongo/typed/MongoUpdate.scala     |  2 +-
 .../mongo/typed/ProjectionZippers.scala       |  4 ++--
 18 files changed, 50 insertions(+), 50 deletions(-)

diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/Filter.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/Filter.scala
index 06e898383..f9d8ec565 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/Filter.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/Filter.scala
@@ -18,13 +18,13 @@ object Filter {
   def or(filters: Bson*): Bson = F.or(filters.asJava)
 
   @deprecated(message = "Use `equal` instead", since = "1.19.9")
-  def eq[A](key: DocKey[A, _], value: A): Bson = equal(key, value)
+  def eq[A](key: DocKey[A, ?], value: A): Bson = equal(key, value)
 
   @deprecated(message = "Use `notEqual` instead", since = "1.19.9")
-  def ne[A](key: DocKey[A, _], value: A): Bson = notEqual(key, value)
+  def ne[A](key: DocKey[A, ?], value: A): Bson = notEqual(key, value)
 
-  def equal[A](key: DocKey[A, _], value: A): Bson = F.eq(key.key, key.codec.toBson(value))
-  def notEqual[A](key: DocKey[A, _], value: A): Bson = F.ne(key.key, key.codec.toBson(value))
+  def equal[A](key: DocKey[A, ?], value: A): Bson = F.eq(key.key, key.codec.toBson(value))
+  def notEqual[A](key: DocKey[A, ?], value: A): Bson = F.ne(key.key, key.codec.toBson(value))
 
   def lt[A, BSON <: BsonValue: CanCompare](key: DocKey[A, BSON], value: A): Bson = F.lt(key.key, key.codec.toBson(value))
 
@@ -36,19 +36,19 @@ object Filter {
   def gte[A, BSON <: BsonValue: CanCompare](key: DocKey[A, BSON], value: A): Bson =
     F.gte(key.key, key.codec.toBson(value))
 
-  def in[A](key: DocKey[A, _], values: Iterable[A]): Bson = F.in(key.key, values.map(key.codec.toBson).asJava)
+  def in[A](key: DocKey[A, ?], values: Iterable[A]): Bson = F.in(key.key, values.map(key.codec.toBson).asJava)
 
-  def nin[A](key: DocKey[A, _], values: Iterable[A]): Bson = F.nin(key.key, values.map(key.codec.toBson).asJava)
+  def nin[A](key: DocKey[A, ?], values: Iterable[A]): Bson = F.nin(key.key, values.map(key.codec.toBson).asJava)
 
   def regex[A](key: DocKey[A, BsonString], pattern: String): Bson = F.regex(key.key, pattern)
 
-  def exists(key: DocKey[_, _]): Bson = F.exists(key.key, true)
+  def exists(key: DocKey[?, ?]): Bson = F.exists(key.key, true)
 
-  def notExists(key: DocKey[_, _]): Bson = F.exists(key.key, false)
+  def notExists(key: DocKey[?, ?]): Bson = F.exists(key.key, false)
 
-  def elemMatch(key: DocKey[_, _ <: BsonArray], filter: Bson): Bson = F.elemMatch(key.key, filter)
+  def elemMatch(key: DocKey[?, ? <: BsonArray], filter: Bson): Bson = F.elemMatch(key.key, filter)
 
-  def contains[A, COL <: Iterable[A]](key: DocKey[COL, _ <: BsonArray], value: A)(implicit fac: Factory[A, COL]): Bson =
+  def contains[A, COL <: Iterable[A]](key: DocKey[COL, ? <: BsonArray], value: A)(implicit fac: Factory[A, COL]): Bson =
     F.eq(key.key, key.codec.toBson((fac.newBuilder += value).result()).asScala.head)
 
   object Limitations {
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/Sort.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/Sort.scala
index 26357af95..765874c40 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/Sort.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/Sort.scala
@@ -8,6 +8,6 @@ import org.bson.conversions.Bson
   *   MKej
   */
 object Sort {
-  def ascending(keys: DocKey[_, _]*): Bson = S.ascending(keys.map(_.key).asJava)
-  def descending(keys: DocKey[_, _]*): Bson = S.descending(keys.map(_.key).asJava)
+  def ascending(keys: DocKey[?, ?]*): Bson = S.ascending(keys.map(_.key).asJava)
+  def descending(keys: DocKey[?, ?]*): Bson = S.descending(keys.map(_.key).asJava)
 }
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/Update.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/Update.scala
index f50ff66a0..1e7153758 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/Update.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/Update.scala
@@ -10,8 +10,8 @@ import org.bson.conversions.Bson
 object Update {
   def combine(updates: Bson*): Bson = U.combine(updates.asJava)
 
-  def set[A](key: DocKey[A, _], value: A): Bson = U.set(key.key, key.codec.toBson(value))
-  def unset(key: DocKey[_, _]): Bson = U.unset(key.key)
+  def set[A](key: DocKey[A, ?], value: A): Bson = U.set(key.key, key.codec.toBson(value))
+  def unset(key: DocKey[?, ?]): Bson = U.unset(key.key)
 
-  def max[A](key: DocKey[A, _], value: A): Bson = U.max(key.key, key.codec.toBson(value))
+  def max[A](key: DocKey[A, ?], value: A): Bson = U.max(key.key, key.codec.toBson(value))
 }
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefFiltering.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefFiltering.scala
index ce3213157..88f1f2a1f 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefFiltering.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefFiltering.scala
@@ -3,5 +3,5 @@ package mongo.core.ops
 
 import com.avsystem.commons.mongo.BsonRef
 
-final class BsonRefFiltering[T](protected val bsonRef: BsonRef[_, T])
+final class BsonRefFiltering[T](protected val bsonRef: BsonRef[?, T])
   extends AnyVal with BaseFiltering[T] with BsonRefKeyValueHandling[T]
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefIterableFiltering.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefIterableFiltering.scala
index cebf0bc24..e96e1cd29 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefIterableFiltering.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefIterableFiltering.scala
@@ -5,7 +5,7 @@ import com.avsystem.commons.mongo.BsonRef
 import com.avsystem.commons.serialization.GenCodec
 
 final class BsonRefIterableFiltering[E, C[T] <: Iterable[T]](
-  protected val bsonRef: BsonRef[_, C[E]]
+  protected val bsonRef: BsonRef[?, C[E]]
 )(implicit protected val elementCodec: GenCodec[E]
 ) extends BaseIterableFiltering[E, C]
     with BsonRefKeyValueHandling[C[E]]
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefIterableUpdating.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefIterableUpdating.scala
index 3ba04cbab..7720fac0d 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefIterableUpdating.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefIterableUpdating.scala
@@ -5,7 +5,7 @@ import com.avsystem.commons.mongo.BsonRef
 import com.avsystem.commons.serialization.GenCodec
 
 final class BsonRefIterableUpdating[E, C[T] <: Iterable[T]](
-  protected val bsonRef: BsonRef[_, C[E]]
+  protected val bsonRef: BsonRef[?, C[E]]
 )(implicit protected val elementCodec: GenCodec[E]
 ) extends BaseIterableUpdating[E, C]
     with BsonRefKeyValueHandling[C[E]]
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefKeyHandling.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefKeyHandling.scala
index 8781163e7..a307ea1a7 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefKeyHandling.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefKeyHandling.scala
@@ -4,7 +4,7 @@ package mongo.core.ops
 import com.avsystem.commons.mongo.BsonRef
 
 trait BsonRefKeyHandling[T] extends Any with KeyHandling {
-  protected def bsonRef: BsonRef[_, T]
+  protected def bsonRef: BsonRef[?, T]
 
   override protected def key: String = bsonRef.path
 }
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefSorting.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefSorting.scala
index 658e8d91a..254a61c9e 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefSorting.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefSorting.scala
@@ -3,4 +3,4 @@ package mongo.core.ops
 
 import com.avsystem.commons.mongo.BsonRef
 
-class BsonRefSorting[T](val bsonRef: BsonRef[_, T]) extends AnyVal with BaseSorting with BsonRefKeyHandling[T]
+class BsonRefSorting[T](val bsonRef: BsonRef[?, T]) extends AnyVal with BaseSorting with BsonRefKeyHandling[T]
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefUpdating.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefUpdating.scala
index fe7faf119..8b43d3391 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefUpdating.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/BsonRefUpdating.scala
@@ -3,4 +3,4 @@ package mongo.core.ops
 
 import com.avsystem.commons.mongo.BsonRef
 
-class BsonRefUpdating[T](val bsonRef: BsonRef[_, T]) extends AnyVal with BaseUpdating[T] with BsonRefKeyValueHandling[T]
+class BsonRefUpdating[T](val bsonRef: BsonRef[?, T]) extends AnyVal with BaseUpdating[T] with BsonRefKeyValueHandling[T]
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/KeyGetter.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/KeyGetter.scala
index 41c7dd72e..0e40d280d 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/KeyGetter.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/core/ops/KeyGetter.scala
@@ -8,11 +8,11 @@ trait KeyGetter[-T] {
 }
 
 object KeyGetter {
-  implicit object bsonRefKeyGetter extends KeyGetter[BsonRef[_, _]] {
-    override def keyOf(t: BsonRef[_, _]): String = t.path
+  implicit object bsonRefKeyGetter extends KeyGetter[BsonRef[?, ?]] {
+    override def keyOf(t: BsonRef[?, ?]): String = t.path
   }
 
-  implicit object docKeyKeyGetter extends KeyGetter[DocKey[_, _]] {
-    override def keyOf(t: DocKey[_, _]): String = t.key
+  implicit object docKeyKeyGetter extends KeyGetter[DocKey[?, ?]] {
+    override def keyOf(t: DocKey[?, ?]): String = t.key
   }
 }
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/FilterDocBuilder.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/FilterDocBuilder.scala
index a841795e3..f5d815659 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/FilterDocBuilder.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/FilterDocBuilder.scala
@@ -12,7 +12,7 @@ private final class FilterDocBuilder(prefixPath: Opt[String], filterDocs: BsonAr
     new FilterDocBuilder(newPrefix.opt, filterDocs)
   }
 
-  @tailrec def addImpliedFilters(ref: MongoRef[_, _]): Unit = ref match {
+  @tailrec def addImpliedFilters(ref: MongoRef[?, ?]): Unit = ref match {
     case MongoRef.RootRef(_) =>
 
     case MongoRef.RootSubtypeRef(fullRef, caseFieldName, caseNames, _) =>
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoFilter.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoFilter.scala
index 2d3d5362d..0e035817e 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoFilter.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoFilter.scala
@@ -143,7 +143,7 @@ sealed trait MongoDocumentFilter[E] extends MongoFilter[E] {
 
   def ||(other: MongoDocumentFilter[E]): MongoDocumentFilter[E] = or(other)
 
-  final def toFilterBson(prefixPath: Opt[String], projectionRefs: Set[MongoRef[E, _]]): BsonDocument = {
+  final def toFilterBson(prefixPath: Opt[String], projectionRefs: Set[MongoRef[E, ?]]): BsonDocument = {
     val builder = new FilterDocBuilder(prefixPath, new BsonArray)
     builder.addFilter(this)
     projectionRefs.foreach(builder.addImpliedFilters)
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoIndex.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoIndex.scala
index d2dc8cff3..15d588303 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoIndex.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoIndex.scala
@@ -36,7 +36,7 @@ import org.bson.{BsonDocument, BsonValue}
   *   type of the MongoDB entity
   */
 case class MongoIndex[E](
-  fields: Vector[(MongoPropertyRef[E, _], MongoIndexType)],
+  fields: Vector[(MongoPropertyRef[E, ?], MongoIndexType)],
   setupOptions: IndexOptions => IndexOptions = identity,
 ) {
   require(fields.nonEmpty, "MongoDB index cannot be empty")
@@ -57,13 +57,13 @@ case class MongoIndex[E](
   }
 }
 object MongoIndex {
-  def apply[E](fields: (MongoPropertyRef[E, _], MongoIndexType)*): MongoIndex[E] =
+  def apply[E](fields: (MongoPropertyRef[E, ?], MongoIndexType)*): MongoIndex[E] =
     MongoIndex(fields.toVector)
 
-  def ascending[E](fields: MongoPropertyRef[E, _]*): MongoIndex[E] =
+  def ascending[E](fields: MongoPropertyRef[E, ?]*): MongoIndex[E] =
     MongoIndex(fields.iterator.map(f => f -> MongoIndexType.Ascending).toVector)
 
-  def descending[E](fields: MongoPropertyRef[E, _]*): MongoIndex[E] =
+  def descending[E](fields: MongoPropertyRef[E, ?]*): MongoIndex[E] =
     MongoIndex(fields.iterator.map(f => f -> MongoIndexType.Descending).toVector)
 }
 
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoOrder.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoOrder.scala
index c43883f71..957ae7569 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoOrder.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoOrder.scala
@@ -21,7 +21,7 @@ object MongoOrder {
 
   def simple[T](ascending: Boolean): MongoOrder[T] = Simple(ascending)
 
-  def apply[E](refs: (MongoPropertyRef[E, _], Boolean)*): MongoDocumentOrder[E] =
+  def apply[E](refs: (MongoPropertyRef[E, ?], Boolean)*): MongoDocumentOrder[E] =
     MongoDocumentOrder(refs: _*)
 
   final case class Simple[T](ascending: Boolean) extends MongoOrder[T] {
@@ -52,17 +52,17 @@ object MongoOrder {
   * @tparam E
   *   type of the entity/document
   */
-case class MongoDocumentOrder[E](refs: Vector[(MongoPropertyRef[E, _], Boolean)]) extends MongoOrder[E] {
+case class MongoDocumentOrder[E](refs: Vector[(MongoPropertyRef[E, ?], Boolean)]) extends MongoOrder[E] {
   def andThen(other: MongoDocumentOrder[E]): MongoDocumentOrder[E] =
     MongoDocumentOrder(refs ++ other.refs)
 
-  def andThenBy(ref: MongoPropertyRef[E, _], ascending: Boolean): MongoDocumentOrder[E] =
+  def andThenBy(ref: MongoPropertyRef[E, ?], ascending: Boolean): MongoDocumentOrder[E] =
     MongoDocumentOrder(refs :+ (ref -> ascending))
 
-  def andThenAscendingBy(ref: MongoPropertyRef[E, _]): MongoDocumentOrder[E] =
+  def andThenAscendingBy(ref: MongoPropertyRef[E, ?]): MongoDocumentOrder[E] =
     andThenBy(ref, ascending = true)
 
-  def andThenDescendingBy(ref: MongoPropertyRef[E, _]): MongoDocumentOrder[E] =
+  def andThenDescendingBy(ref: MongoPropertyRef[E, ?]): MongoDocumentOrder[E] =
     andThenBy(ref, ascending = false)
 
   // TODO: lambda-macro versions of andThenBy
@@ -73,12 +73,12 @@ case class MongoDocumentOrder[E](refs: Vector[(MongoPropertyRef[E, _], Boolean)]
 object MongoDocumentOrder {
   def unspecified[E]: MongoDocumentOrder[E] = MongoDocumentOrder(Vector.empty)
 
-  def apply[E](refs: (MongoPropertyRef[E, _], Boolean)*): MongoDocumentOrder[E] =
+  def apply[E](refs: (MongoPropertyRef[E, ?], Boolean)*): MongoDocumentOrder[E] =
     MongoDocumentOrder(refs.toVector)
 
-  def ascending[E](refs: MongoPropertyRef[E, _]*): MongoDocumentOrder[E] =
+  def ascending[E](refs: MongoPropertyRef[E, ?]*): MongoDocumentOrder[E] =
     MongoDocumentOrder(refs.iterator.map(r => r -> true).toVector)
 
-  def descending[E](refs: MongoPropertyRef[E, _]*): MongoDocumentOrder[E] =
+  def descending[E](refs: MongoPropertyRef[E, ?]*): MongoDocumentOrder[E] =
     MongoDocumentOrder(refs.iterator.map(r => r -> false).toVector)
 }
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoProjection.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoProjection.scala
index 3d7bdb327..e852f29f9 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoProjection.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoProjection.scala
@@ -35,7 +35,7 @@ import scala.annotation.tailrec
   *   [[https://docs.mongodb.com/manual/tutorial/project-fields-from-query-results/]]
   */
 trait MongoProjection[E, T] {
-  def projectionRefs: Set[MongoRef[E, _]]
+  def projectionRefs: Set[MongoRef[E, ?]]
   def decodeFrom(doc: BsonDocument): T
   def showRecordId: Boolean
 
@@ -70,12 +70,12 @@ trait MongoProjection[E, T] {
 
   final def toProjectionBson: BsonDocument = {
     val doc = new BsonDocument
-    @tailrec def loop(it: Iterator[MongoRef[E, _]]): Unit =
+    @tailrec def loop(it: Iterator[MongoRef[E, ?]]): Unit =
       if (it.hasNext) it.next() match {
-        case propRef: MongoPropertyRef[E, _] =>
+        case propRef: MongoPropertyRef[E, ?] =>
           doc.put(propRef.projectionPath, Bson.int(1))
           loop(it)
-        case _: MongoToplevelRef[E, _] =>
+        case _: MongoToplevelRef[E, ?] =>
           doc.clear()
       }
     loop(projectionRefs.iterator)
@@ -88,7 +88,7 @@ trait MongoProjection[E, T] {
 
 object MongoProjection extends ProjectionZippers {
   final class Mapped[E, T, T0](prev: MongoProjection[E, T], fun: T => T0) extends MongoProjection[E, T0] {
-    def projectionRefs: Set[MongoRef[E, _]] = prev.projectionRefs
+    def projectionRefs: Set[MongoRef[E, ?]] = prev.projectionRefs
     def showRecordId: Boolean = prev.showRecordId
     def decodeFrom(doc: BsonDocument): T0 = fun(prev.decodeFrom(doc))
     def on[E0](ref: MongoRef[E0, E]): MongoProjection[E0, T0] = new Mapped(prev.on(ref), fun)
@@ -99,7 +99,7 @@ object MongoProjection extends ProjectionZippers {
     second: MongoProjection[E, T0],
     fun: (T, T0) => T1,
   ) extends MongoProjection[E, T1] {
-    def projectionRefs: Set[MongoRef[E, _]] =
+    def projectionRefs: Set[MongoRef[E, ?]] =
       first.projectionRefs ++ second.projectionRefs
 
     def showRecordId: Boolean = first.showRecordId || second.showRecordId
@@ -114,7 +114,7 @@ object MongoProjection extends ProjectionZippers {
   final val RecordId = "$recordId"
 
   final case class ShowRecordId[E, T](projection: MongoProjection[E, T]) extends MongoProjection[E, WithRecordId[T]] {
-    def projectionRefs: Set[MongoRef[E, _]] = projection.projectionRefs
+    def projectionRefs: Set[MongoRef[E, ?]] = projection.projectionRefs
 
     def decodeFrom(doc: BsonDocument): WithRecordId[T] =
       WithRecordId(projection.decodeFrom(doc), doc.getInt64(RecordId).getValue)
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoRef.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoRef.scala
index 59926bf5d..7a46ec23a 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoRef.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoRef.scala
@@ -22,7 +22,7 @@ import scala.annotation.tailrec
   */
 sealed trait MongoRef[E, T] extends MongoProjection[E, T] with DataRefDsl[E, T] { self =>
   def format: MongoFormat[T]
-  def projectionRefs: Set[MongoRef[E, _]] = Set(this)
+  def projectionRefs: Set[MongoRef[E, ?]] = Set(this)
   def showRecordId: Boolean = false
 
   @macroPrivate def subtypeRefFor[C <: T: ClassTag]: MongoRef[E, C]
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoUpdate.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoUpdate.scala
index e12b24a28..5733c67a5 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoUpdate.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoUpdate.scala
@@ -81,7 +81,7 @@ object MongoUpdate {
   ) extends MongoUpdate[T]
 
   final case class MultiUpdate[E](
-    propUpdates: Vector[PropertyUpdate[E, _]]
+    propUpdates: Vector[PropertyUpdate[E, ?]]
   ) extends MongoDocumentUpdate[E]
 
   final case class PropertyUpdate[E, T](
diff --git a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/ProjectionZippers.scala b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/ProjectionZippers.scala
index 379e50296..9a6aaf404 100644
--- a/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/ProjectionZippers.scala
+++ b/mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/ProjectionZippers.scala
@@ -357,10 +357,10 @@ trait ProjectionZippers { this: MongoProjection.type =>
     )
 }
 
-final class ProductProjection[E, T](componentProjections: Seq[MongoProjection[E, _]])(implicit applier: Applier[T])
+final class ProductProjection[E, T](componentProjections: Seq[MongoProjection[E, ?]])(implicit applier: Applier[T])
   extends MongoProjection[E, T] {
 
-  def projectionRefs: Set[MongoRef[E, _]] =
+  def projectionRefs: Set[MongoRef[E, ?]] =
     componentProjections.iterator.flatMap(_.projectionRefs.iterator).toSet
 
   def showRecordId: Boolean =