From 3184be51662fc544ab13950d95d55009cc2d7a1e Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Fri, 30 Jan 2026 10:28:49 -0800
Subject: [PATCH 1/3] Drop Scala 2.12 support

- Remove scala-2.12- version-specific source directories
- Update build.sbt to only support Scala 2.13 and 3.3.4
- Update CI workflow to remove 2.12 from test matrix
- Use Scala 2.13+ APIs (IterableOnce, jdk.CollectionConverters)

BREAKING: Scala 2.12 is no longer supported.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
---
 .github/workflows/ci.yaml                     |   2 -
 build.sbt                                     |  22 +-
 .../chill/AllScalaRegistrarCompat.scala       |  32 ---
 .../chill/ClassManifestSerializer.scala       |  27 ---
 .../com/twitter/chill/RichKryoCompat.scala    |  48 ----
 .../com/twitter/chill/Traversable.scala       |  49 ----
 .../chill/WrappedArraySerializer.scala        |  41 ----
 .../chill/RegistrationIdsSpecData.scala       | 174 --------------
 .../chill/SerializedExamplesData.scala        | 223 ------------------
 .../chill/ExternalizerAdditionalSpec.scala    |   2 +-
 10 files changed, 10 insertions(+), 610 deletions(-)
 delete mode 100644 chill-scala/src/main/scala-2.12-/com/twitter/chill/AllScalaRegistrarCompat.scala
 delete mode 100644 chill-scala/src/main/scala-2.12-/com/twitter/chill/ClassManifestSerializer.scala
 delete mode 100644 chill-scala/src/main/scala-2.12-/com/twitter/chill/RichKryoCompat.scala
 delete mode 100644 chill-scala/src/main/scala-2.12-/com/twitter/chill/Traversable.scala
 delete mode 100644 chill-scala/src/main/scala-2.12-/com/twitter/chill/WrappedArraySerializer.scala
 delete mode 100644 chill-scala/src/test/scala-2.12-/com/twitter/chill/RegistrationIdsSpecData.scala
 delete mode 100644 chill-scala/src/test/scala-2.12-/com/twitter/chill/SerializedExamplesData.scala

diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 0046d6b3..ace84ec2 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -33,7 +33,6 @@ jobs:
           - "21"
           - "25"
         scala:
-          - "2.12.21"
           - "2.13.18"
   test:
     runs-on: ubuntu-latest
@@ -52,7 +51,6 @@ jobs:
           - "21"
           - "25"
         scala:
-          - "2.12.21"
           - "2.13.18"
           - "3.3.4"
   testWithCoverageReport:
diff --git a/build.sbt b/build.sbt
index 6b7af37a..0b1c078a 100644
--- a/build.sbt
+++ b/build.sbt
@@ -10,8 +10,6 @@ val protobufVersion = "3.25.5"
 
 def scalaVersionSpecificFolders(srcBaseDir: java.io.File, scalaVersion: String): List[File] =
   CrossVersion.partialVersion(scalaVersion) match {
-    case Some((2, y)) if y <= 12 =>
-      new java.io.File(s"${srcBaseDir.getPath}-2.12-") :: Nil
     case Some((2, y)) if y >= 13 =>
       new java.io.File(s"${srcBaseDir.getPath}-2.13+") :: Nil
     case Some((3, _)) =>
@@ -20,11 +18,9 @@ def scalaVersionSpecificFolders(srcBaseDir: java.io.File, scalaVersion: String):
     case _ => Nil
   }
 
-val scala212 = "2.12.21"
 val scala213 = "2.13.18"
 val scala3 = "3.3.4"
-val scala2Versions = Seq(scala212, scala213)
-val allScalaVersions = scala2Versions :+ scala3
+val allScalaVersions = Seq(scala213, scala3)
 
 val sharedSettings = Seq(
   organization := "com.twitter",
@@ -197,10 +193,10 @@ lazy val chillPekko = module("pekko")
   )
   .dependsOn(chill % "test->test;compile->compile")
 
-// Bijection only supports Scala 2.x
+// Bijection only supports Scala 2.13
 lazy val chillBijection = module("bijection")
   .settings(
-    crossScalaVersions := scala2Versions,
+    crossScalaVersions := Seq(scala213),
     libraryDependencies ++= Seq(
       "com.twitter" %% "bijection-core" % bijectionVersion
     )
@@ -244,10 +240,10 @@ lazy val chillThrift = module("thrift").settings(
   )
 )
 
-// Scrooge only supports Scala 2.x
+// Scrooge only supports Scala 2.13
 lazy val chillScrooge = module("scrooge")
   .settings(
-    crossScalaVersions := scala2Versions,
+    crossScalaVersions := Seq(scala213),
     libraryDependencies ++= Seq(
       ("org.apache.thrift" % "libthrift" % "0.22.0").exclude("junit", "junit"),
       "com.twitter" %% "scrooge-serializer" % scroogeVersion
@@ -267,10 +263,10 @@ lazy val chillProtobuf = module("protobuf")
   )
   .dependsOn(chillJava)
 
-// Avro depends on bijection which only supports Scala 2.x
+// Avro depends on bijection which only supports Scala 2.13
 lazy val chillAvro = module("avro")
   .settings(
-    crossScalaVersions := scala2Versions,
+    crossScalaVersions := Seq(scala213),
     libraryDependencies ++= Seq(
       "com.twitter" %% "bijection-avro" % bijectionVersion,
       "junit" % "junit" % "4.13.2" % "test"
@@ -278,10 +274,10 @@ lazy val chillAvro = module("avro")
   )
   .dependsOn(chill, chillJava, chillBijection)
 
-// Algebird only supports Scala 2.x
+// Algebird only supports Scala 2.13
 lazy val chillAlgebird = module("algebird")
   .settings(
-    crossScalaVersions := scala2Versions,
+    crossScalaVersions := Seq(scala213),
     libraryDependencies ++= Seq(
       "com.twitter" %% "algebird-core" % algebirdVersion
     )
diff --git a/chill-scala/src/main/scala-2.12-/com/twitter/chill/AllScalaRegistrarCompat.scala b/chill-scala/src/main/scala-2.12-/com/twitter/chill/AllScalaRegistrarCompat.scala
deleted file mode 100644
index 528a9dd4..00000000
--- a/chill-scala/src/main/scala-2.12-/com/twitter/chill/AllScalaRegistrarCompat.scala
+++ /dev/null
@@ -1,32 +0,0 @@
-/*
-Copyright 2019 Twitter, Inc.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
- */
-
-package com.twitter.chill
-
-/**
- * Scala collections registrar for compatibility between 2.12- and 2.13+.
- *
- * For 2.12- there's no extra classes that need to be registered.
- * @see
- *   [[ScalaCollectionsRegistrar]] and [[AllScalaRegistrar]] for all the provided registrations.
- */
-private[chill] class AllScalaRegistrarCompat_0_9_5 extends IKryoRegistrar {
-  override def apply(newK: Kryo): Unit = ()
-}
-
-private[chill] class AllScalaRegistrarCompat extends IKryoRegistrar {
-  override def apply(newK: Kryo): Unit = ()
-}
diff --git a/chill-scala/src/main/scala-2.12-/com/twitter/chill/ClassManifestSerializer.scala b/chill-scala/src/main/scala-2.12-/com/twitter/chill/ClassManifestSerializer.scala
deleted file mode 100644
index 37dcfa0c..00000000
--- a/chill-scala/src/main/scala-2.12-/com/twitter/chill/ClassManifestSerializer.scala
+++ /dev/null
@@ -1,27 +0,0 @@
-/*
-Copyright 2019 Twitter, Inc.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
- */
-
-package com.twitter.chill
-
-class ClassManifestSerializer[T] extends KSerializer[ClassManifest[T]] {
-  def write(kser: Kryo, out: Output, obj: ClassManifest[T]): Unit =
-    kser.writeObject(out, obj.runtimeClass)
-
-  def read(kser: Kryo, in: Input, cls: Class[ClassManifest[T]]): ClassManifest[T] = {
-    val clazz = kser.readObject(in, classOf[Class[T]])
-    ClassManifest.fromClass[T](clazz)
-  }
-}
diff --git a/chill-scala/src/main/scala-2.12-/com/twitter/chill/RichKryoCompat.scala b/chill-scala/src/main/scala-2.12-/com/twitter/chill/RichKryoCompat.scala
deleted file mode 100644
index bf091058..00000000
--- a/chill-scala/src/main/scala-2.12-/com/twitter/chill/RichKryoCompat.scala
+++ /dev/null
@@ -1,48 +0,0 @@
-/*
-Copyright 2019 Twitter, Inc.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
- */
-
-package com.twitter.chill
-
-import scala.collection.generic.CanBuildFrom
-
-import scala.reflect._
-
-trait RichKryoCompat { self: RichKryo =>
-
-  def forTraversableSubclass[T, C <: Traversable[T]](
-      c: C with Traversable[T],
-      isImmutable: Boolean = true
-  )(implicit mf: ClassTag[C], cbf: CanBuildFrom[C, T, C]): Kryo = {
-    k.addDefaultSerializer(mf.runtimeClass, new TraversableSerializer(isImmutable)(cbf))
-    k
-  }
-
-  def forTraversableClass[T, C <: Traversable[T]](
-      c: C with Traversable[T],
-      isImmutable: Boolean = true
-  )(implicit mf: ClassTag[C], cbf: CanBuildFrom[C, T, C]): Kryo =
-    forClass(new TraversableSerializer(isImmutable)(cbf))
-
-  def forConcreteTraversableClass[T, C <: Traversable[T]](
-      c: C with Traversable[T],
-      isImmutable: Boolean = true
-  )(implicit cbf: CanBuildFrom[C, T, C]): Kryo = {
-    // a ClassTag is not used here since its runtimeClass method does not return the concrete internal type
-    // that Scala uses for small immutable maps (i.e., scala.collection.immutable.Map$Map1)
-    k.register(c.getClass, new TraversableSerializer(isImmutable)(cbf))
-    k
-  }
-}
diff --git a/chill-scala/src/main/scala-2.12-/com/twitter/chill/Traversable.scala b/chill-scala/src/main/scala-2.12-/com/twitter/chill/Traversable.scala
deleted file mode 100644
index c4547761..00000000
--- a/chill-scala/src/main/scala-2.12-/com/twitter/chill/Traversable.scala
+++ /dev/null
@@ -1,49 +0,0 @@
-/*
-Copyright 2019 Twitter, Inc.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
- */
-
-package com.twitter.chill
-
-import scala.collection.generic.CanBuildFrom
-
-class TraversableSerializer[T, C <: Traversable[T]](override val isImmutable: Boolean = true)(implicit
-    cbf: CanBuildFrom[C, T, C]
-) extends KSerializer[C] {
-  def write(kser: Kryo, out: Output, obj: C): Unit = {
-    // Write the size:
-    out.writeInt(obj.size, true)
-    obj.foreach { t =>
-      val tRef = t.asInstanceOf[AnyRef]
-      kser.writeClassAndObject(out, tRef)
-      // After each intermediate object, flush
-      out.flush()
-    }
-  }
-
-  def read(kser: Kryo, in: Input, cls: Class[C]): C = {
-    val size = in.readInt(true)
-    // Go ahead and be faster, and not as functional cool, and be mutable in here
-    var idx = 0
-    val builder = cbf()
-    builder.sizeHint(size)
-
-    while (idx < size) {
-      val item = kser.readClassAndObject(in).asInstanceOf[T]
-      builder += item
-      idx += 1
-    }
-    builder.result()
-  }
-}
diff --git a/chill-scala/src/main/scala-2.12-/com/twitter/chill/WrappedArraySerializer.scala b/chill-scala/src/main/scala-2.12-/com/twitter/chill/WrappedArraySerializer.scala
deleted file mode 100644
index 54119cce..00000000
--- a/chill-scala/src/main/scala-2.12-/com/twitter/chill/WrappedArraySerializer.scala
+++ /dev/null
@@ -1,41 +0,0 @@
-/*
-Copyright 2019 Twitter, Inc.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
- */
-
-package com.twitter.chill
-
-import scala.collection.mutable
-import scala.collection.mutable.{ArrayBuilder, WrappedArray}
-import scala.reflect._
-
-class WrappedArraySerializer[T] extends KSerializer[WrappedArray[T]] {
-  def write(kser: Kryo, out: Output, obj: WrappedArray[T]): Unit = {
-    // Write the class-manifest, we don't use writeClass because it
-    // uses the registration system, and this class might not be registered
-    kser.writeObject(out, obj.elemTag.runtimeClass)
-    kser.writeClassAndObject(out, obj.array)
-  }
-
-  def read(kser: Kryo, in: Input, cls: Class[WrappedArray[T]]): mutable.WrappedArray[T] = {
-    // Write the class-manifest, we don't use writeClass because it
-    // uses the registration system, and this class might not be registered
-    val clazz = kser.readObject(in, classOf[Class[T]])
-    val array = kser.readClassAndObject(in).asInstanceOf[Array[T]]
-    val bldr = ArrayBuilder.make[T]()(ClassTag[T](clazz))
-    bldr.sizeHint(array.size)
-    bldr ++= array
-    bldr.result()
-  }
-}
diff --git a/chill-scala/src/test/scala-2.12-/com/twitter/chill/RegistrationIdsSpecData.scala b/chill-scala/src/test/scala-2.12-/com/twitter/chill/RegistrationIdsSpecData.scala
deleted file mode 100644
index d7c5e8ee..00000000
--- a/chill-scala/src/test/scala-2.12-/com/twitter/chill/RegistrationIdsSpecData.scala
+++ /dev/null
@@ -1,174 +0,0 @@
-/*
-Copyright 2019 Twitter, Inc.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
- */
-
-package com.twitter.chill
-
-object RegistrationIdsSpecData {
-  val Entries_0_9_5 =
-    """0 -> int
-      |1 -> class java.lang.String
-      |2 -> float
-      |3 -> boolean
-      |4 -> byte
-      |5 -> char
-      |6 -> short
-      |7 -> long
-      |8 -> double
-      |9 -> void
-      |10 -> class scala.collection.convert.Wrappers$SeqWrapper
-      |11 -> class scala.collection.convert.Wrappers$IteratorWrapper
-      |12 -> class scala.collection.convert.Wrappers$MapWrapper
-      |13 -> class scala.collection.convert.Wrappers$JListWrapper
-      |14 -> class scala.collection.convert.Wrappers$JMapWrapper
-      |15 -> class scala.Some
-      |16 -> class scala.util.Left
-      |17 -> class scala.util.Right
-      |18 -> class scala.collection.immutable.Vector
-      |19 -> class scala.collection.immutable.Set$Set1
-      |20 -> class scala.collection.immutable.Set$Set2
-      |21 -> class scala.collection.immutable.Set$Set3
-      |22 -> class scala.collection.immutable.Set$Set4
-      |23 -> class scala.collection.immutable.HashSet$HashTrieSet
-      |24 -> class scala.collection.immutable.Map$Map1
-      |25 -> class scala.collection.immutable.Map$Map2
-      |26 -> class scala.collection.immutable.Map$Map3
-      |27 -> class scala.collection.immutable.Map$Map4
-      |28 -> class scala.collection.immutable.HashMap$HashTrieMap
-      |29 -> class scala.collection.immutable.Range$Inclusive
-      |30 -> class scala.collection.immutable.NumericRange$Inclusive
-      |31 -> class scala.collection.immutable.NumericRange$Exclusive
-      |32 -> class scala.collection.mutable.BitSet
-      |33 -> class scala.collection.mutable.HashMap
-      |34 -> class scala.collection.mutable.HashSet
-      |35 -> class scala.collection.convert.Wrappers$IterableWrapper
-      |36 -> class scala.Tuple1
-      |37 -> class scala.Tuple2
-      |38 -> class scala.Tuple3
-      |39 -> class scala.Tuple4
-      |40 -> class scala.Tuple5
-      |41 -> class scala.Tuple6
-      |42 -> class scala.Tuple7
-      |43 -> class scala.Tuple8
-      |44 -> class scala.Tuple9
-      |45 -> class scala.Tuple10
-      |46 -> class scala.Tuple11
-      |47 -> class scala.Tuple12
-      |48 -> class scala.Tuple13
-      |49 -> class scala.Tuple14
-      |50 -> class scala.Tuple15
-      |51 -> class scala.Tuple16
-      |52 -> class scala.Tuple17
-      |53 -> class scala.Tuple18
-      |54 -> class scala.Tuple19
-      |55 -> class scala.Tuple20
-      |56 -> class scala.Tuple21
-      |57 -> class scala.Tuple22
-      |58 -> class scala.Tuple1$mcJ$sp
-      |59 -> class scala.Tuple1$mcI$sp
-      |60 -> class scala.Tuple1$mcD$sp
-      |61 -> class scala.Tuple2$mcJJ$sp
-      |62 -> class scala.Tuple2$mcJI$sp
-      |63 -> class scala.Tuple2$mcJD$sp
-      |64 -> class scala.Tuple2$mcIJ$sp
-      |65 -> class scala.Tuple2$mcII$sp
-      |66 -> class scala.Tuple2$mcID$sp
-      |67 -> class scala.Tuple2$mcDJ$sp
-      |68 -> class scala.Tuple2$mcDI$sp
-      |69 -> class scala.Tuple2$mcDD$sp
-      |70 -> class scala.Symbol
-      |71 -> interface scala.reflect.ClassTag
-      |72 -> class scala.runtime.BoxedUnit
-      |73 -> class java.util.Arrays$ArrayList
-      |74 -> class java.util.BitSet
-      |75 -> class java.util.PriorityQueue
-      |76 -> class java.util.regex.Pattern
-      |77 -> class java.sql.Date
-      |78 -> class java.sql.Time
-      |79 -> class java.sql.Timestamp
-      |80 -> class java.net.URI
-      |81 -> class java.net.InetSocketAddress
-      |82 -> class java.util.UUID
-      |83 -> class java.util.Locale
-      |84 -> class java.text.SimpleDateFormat
-      |85 -> class java.util.Collections$UnmodifiableCollection
-      |86 -> class java.util.Collections$UnmodifiableRandomAccessList
-      |87 -> class java.util.Collections$UnmodifiableList
-      |88 -> class java.util.Collections$UnmodifiableMap
-      |89 -> class java.util.Collections$UnmodifiableSet
-      |90 -> class java.util.Collections$UnmodifiableSortedMap
-      |91 -> class java.util.Collections$UnmodifiableSortedSet
-      |92 -> class com.esotericsoftware.kryo.serializers.ClosureSerializer$Closure
-      |93 -> class [B
-      |94 -> class [S
-      |95 -> class [I
-      |96 -> class [J
-      |97 -> class [F
-      |98 -> class [D
-      |99 -> class [Z
-      |100 -> class [C
-      |101 -> class [Ljava.lang.String;
-      |102 -> class [Ljava.lang.Object;
-      |103 -> class java.lang.Class
-      |104 -> class java.lang.Object
-      |105 -> class scala.collection.mutable.WrappedArray$ofByte
-      |106 -> class scala.collection.mutable.WrappedArray$ofShort
-      |107 -> class scala.collection.mutable.WrappedArray$ofInt
-      |108 -> class scala.collection.mutable.WrappedArray$ofLong
-      |109 -> class scala.collection.mutable.WrappedArray$ofFloat
-      |110 -> class scala.collection.mutable.WrappedArray$ofDouble
-      |111 -> class scala.collection.mutable.WrappedArray$ofBoolean
-      |112 -> class scala.collection.mutable.WrappedArray$ofChar
-      |113 -> class scala.collection.mutable.WrappedArray$ofRef
-      |114 -> class scala.None$
-      |115 -> class scala.collection.immutable.Queue
-      |116 -> class scala.collection.immutable.Nil$
-      |117 -> class scala.collection.immutable.$colon$colon
-      |118 -> class scala.collection.immutable.Range
-      |119 -> class scala.collection.immutable.WrappedString
-      |120 -> class scala.collection.immutable.TreeSet
-      |121 -> class scala.collection.immutable.TreeMap
-      |122 -> class scala.math.Ordering$Byte$
-      |123 -> class scala.math.Ordering$Short$
-      |124 -> class scala.math.Ordering$Int$
-      |125 -> class scala.math.Ordering$Long$
-      |126 -> class scala.math.Ordering$Float$
-      |127 -> class scala.math.Ordering$Double$
-      |128 -> class scala.math.Ordering$Boolean$
-      |129 -> class scala.math.Ordering$Char$
-      |130 -> class scala.math.Ordering$String$
-      |131 -> class scala.collection.immutable.Set$EmptySet$
-      |132 -> class scala.collection.immutable.ListSet$EmptyListSet$
-      |133 -> class scala.collection.immutable.ListSet$Node
-      |134 -> class scala.collection.immutable.HashSet$EmptyHashSet$
-      |135 -> class scala.collection.immutable.HashSet$HashSet1
-      |136 -> class scala.collection.immutable.Map$EmptyMap$
-      |137 -> class scala.collection.immutable.HashMap$EmptyHashMap$
-      |138 -> class scala.collection.immutable.HashMap$HashMap1
-      |139 -> class scala.collection.immutable.ListMap$EmptyListMap$
-      |140 -> class scala.collection.immutable.ListMap$Node
-      |141 -> class scala.collection.immutable.Stream$Cons
-      |142 -> class scala.collection.immutable.Stream$Empty$
-      |143 -> class scala.runtime.VolatileByteRef
-      |144 -> class scala.math.BigDecimal
-      |145 -> class scala.collection.immutable.Queue$EmptyQueue$
-      |146 -> class scala.collection.immutable.MapLike$$anon$1
-      |147 -> class scala.collection.immutable.MapLike$$anon$2
-      |148 -> class scala.collection.immutable.MapLike$ImmutableDefaultKeySet""".stripMargin.linesIterator.toStream
-
-  val RecentEntries = Stream.empty
-
-  val CurrentEntries = Entries_0_9_5 #::: RecentEntries
-}
diff --git a/chill-scala/src/test/scala-2.12-/com/twitter/chill/SerializedExamplesData.scala b/chill-scala/src/test/scala-2.12-/com/twitter/chill/SerializedExamplesData.scala
deleted file mode 100644
index 460c87fb..00000000
--- a/chill-scala/src/test/scala-2.12-/com/twitter/chill/SerializedExamplesData.scala
+++ /dev/null
@@ -1,223 +0,0 @@
-/*
-Copyright 2019 Twitter, Inc.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
- */
-
-package com.twitter.chill
-
-import scala.collection.JavaConverters
-import scala.collection.JavaConverters._
-import scala.collection.immutable.{HashMap, HashSet, ListMap, ListSet, NumericRange, Queue}
-import scala.runtime.VolatileByteRef
-
-object SerializedExamplesData {
-  val Examples = Seq(
-    0 -> ("AgI=" -> Int.box(1)),
-    1 -> ("AwFhYuM=" -> "abc"),
-    2 -> ("BD+AAAA=" -> Float.box(1)),
-    3 -> ("BQE=" -> Boolean.box(true)),
-    4 -> ("BgE=" -> Byte.box(1)),
-    5 -> ("BwBh" -> Char.box('a')),
-    6 -> ("CAAB" -> Short.box(1)),
-    7 -> ("CQI=" -> Long.box(1)),
-    8 -> ("Cj/wAAAAAAAA" -> Double.box(1)),
-    // 9 -> void is a special case
-    // Note: Instead of JavaConverters.***Converter(***).as***, in Scala 2.12
-    // methods JavaConverters.*** can be used directly. For backwards compatibility,
-    // the legacy methods to convert are used here.
-    10 -> ("DAEBAHNjYWxhLmNvbGxlY3Rpb24uY29udmVydC5XcmFwcGVyc6QBdwEBAgQ=" ->
-      JavaConverters.seqAsJavaListConverter(Seq(2)).asJava), // Wrappers$SeqWrapper
-    11 -> ("DQEBAHNjYWxhLmNvbGxlY3Rpb24uY29udmVydC5XcmFwcGVyc6QBAQFzY2FsYS5jb2xsZWN0aW9uLkluZGV4ZWRTZXFMaWtlJEVsZW1lbnTzAW0BAQIBYQECBAIA" ->
-      JavaConverters.asJavaIteratorConverter(Iterator(2)).asJava), // Wrappers$IteratorWrapper
-    12 -> ("DgEBAHNjYWxhLmNvbGxlY3Rpb24uY29udmVydC5XcmFwcGVyc6QBGgEBJwECBAIE" ->
-      JavaConverters.mapAsJavaMapConverter(Map(2 -> 2)).asJava), // Wrappers$MapWrapper
-    13 -> ("DwEBAHNjYWxhLmNvbGxlY3Rpb24uY29udmVydC5XcmFwcGVyc6QBAQFqYXZhLnV0aWwuQ29sbGVjdGlvbnMkU2luZ2xldG9uTGlz9AECBA==" ->
-      JavaConverters
-        .asScalaBufferConverter(_root_.java.util.Collections.singletonList(2))
-        .asScala), // Wrappers$JListWrapper
-    14 -> ("EAEBAHNjYWxhLmNvbGxlY3Rpb24uY29udmVydC5XcmFwcGVyc6QBAQFqYXZhLnV0aWwuQ29sbGVjdGlvbnMkU2luZ2xldG9uTWHwAQIEAgQ=" ->
-      JavaConverters
-        .mapAsScalaMapConverter(_root_.java.util.Collections.singletonMap(2, 2))
-        .asScala), // Wrappers$JMapWrapper
-    15 -> ("EQECBA==" -> Some(2)),
-    16 -> ("EgECBA==" -> Left(2)),
-    17 -> ("EwECBA==" -> Right(2)),
-    18 -> ("FAEBAgQ=" -> Vector(2)),
-    19 -> ("FQEBAgQ=" -> Set(2)),
-    20 -> ("FgECAgQCBg==" -> Set(2, 3)),
-    21 -> ("FwEDAgQCBgII" -> Set(2, 3, 4)),
-    22 -> ("GAEEAgQCBgIIAgo=" -> Set(2, 3, 4, 5)),
-    // 23 -> class HashSet$HashTrieSet
-    24 -> ("GgEBJwECBAIG" -> Map(2 -> 3)),
-    25 -> ("GwECJwECBAIGJwECCAIK" -> Map(2 -> 3, 4 -> 5)),
-    26 -> ("HAEDJwECBAIGJwECCAIKJwECDAIO" -> Map(2 -> 3, 4 -> 5, 6 -> 7)),
-    27 -> ("HQEEJwECBAIGJwECCAIKJwECDAIOJwECEAIS" -> Map(2 -> 3, 4 -> 5, 6 -> 7, 8 -> 9)),
-    // 28 -> class HashMap$HashTrieMap
-    29 -> ("HwEMAAwIBgI=" -> new Range.Inclusive(3, 6, 1)),
-    30 -> ("IAEBAgoAAQABAHNjYWxhLm1hdGguTnVtZXJpYyRJbnRJc0ludGVncmFspAEBAAMIAgQCAg==" ->
-      new NumericRange.Inclusive[Int](2, 5, 1)),
-    31 -> ("IQEBAgoAAAABAHNjYWxhLm1hdGguTnVtZXJpYyRJbnRJc0ludGVncmFspAEBAAMGAgQCAg==" ->
-      new NumericRange.Exclusive[Int](2, 5, 1)),
-    32 -> ("IgECAgYCCg==" -> scala.collection.mutable.BitSet(3, 5)),
-    33 -> ("IwEBJwECBgIK" -> scala.collection.mutable.HashMap(3 -> 5)),
-    34 -> ("JAEBAgY=" -> scala.collection.mutable.HashSet(3)),
-    35 -> ("JQF3AQECBA==" -> Seq(2).asJavaCollection), // Wrappers$IterableWrapper
-    36 -> ("JgEDAYJh" -> Tuple1("a")),
-    37 -> ("JwEDAYJhAwGCYg==" -> ("a", "b")),
-    38 -> ("KAECAgIEAgY=" -> (1, 2, 3)),
-    39 -> ("KQECAgIEAgYCCA==" -> (1, 2, 3, 4)),
-    40 -> ("KgECAgIEAgYCCAIK" -> (1, 2, 3, 4, 5)),
-    41 -> ("KwECAgIEAgYCCAIKAgw=" -> (1, 2, 3, 4, 5, 6)),
-    42 -> ("LAECAgIEAgYCCAIKAgwCDg==" -> (1, 2, 3, 4, 5, 6, 7)),
-    43 -> ("LQECAgIEAgYCCAIKAgwCDgIQ" -> (1, 2, 3, 4, 5, 6, 7, 8)),
-    44 -> ("LgECAgIEAgYCCAIKAgwCDgIQAhI=" -> (1, 2, 3, 4, 5, 6, 7, 8, 9)),
-    45 -> ("LwECAgIEAgYCCAIKAgwCDgIQAhICAA==" -> (1, 2, 3, 4, 5, 6, 7, 8, 9, 0)),
-    46 -> ("MAECAgIEAgYCCAIKAgwCDgIQAhICAAIC" -> (1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1)),
-    47 -> ("MQECAgIEAgYCCAIKAgwCDgIQAhICAAICAgQ=" -> (1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2)),
-    48 -> ("MgECAgIEAgYCCAIKAgwCDgIQAhICAAICAgQCBg==" -> (1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3)),
-    49 -> ("MwECAgIEAgYCCAIKAgwCDgIQAhICAAICAgQCBgII" -> (1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4)),
-    50 -> ("NAECAgIEAgYCCAIKAgwCDgIQAhICAAICAgQCBgIIAgo=" -> (1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5)),
-    51 -> ("NQECAgIEAgYCCAIKAgwCDgIQAhICAAICAgQCBgIIAgoCDA==" -> (1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5,
-      6)),
-    52 -> ("NgECAgIEAgYCCAIKAgwCDgIQAhICAAICAgQCBgIIAgoCDAIO" -> (1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5,
-      6, 7)),
-    53 -> ("NwECAgIEAgYCCAIKAgwCDgIQAhICAAICAgQCBgIIAgoCDAIOAhA=" -> (1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3,
-      4, 5, 6, 7, 8)),
-    54 -> ("OAECAgIEAgYCCAIKAgwCDgIQAhICAAICAgQCBgIIAgoCDAIOAhACEg==" -> (1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2,
-      3, 4, 5, 6, 7, 8, 9)),
-    55 -> ("OQECAgIEAgYCCAIKAgwCDgIQAhICAAICAgQCBgIIAgoCDAIOAhACEgIA" -> (1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2,
-      3, 4, 5, 6, 7, 8, 9, 0)),
-    56 -> ("OgECAgIEAgYCCAIKAgwCDgIQAhICAAICAgQCBgIIAgoCDAIOAhACEgIAAgI=" -> (1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1,
-      2, 3, 4, 5, 6, 7, 8, 9, 0, 1)),
-    57 -> ("OwECAgIEAgYCCAIKAgwCDgIQAhICAAICAgQCBgIIAgoCDAIOAhACEgIAAgICBA==" -> (1, 2, 3, 4, 5, 6, 7, 8, 9,
-      0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2)),
-    58 -> ("PAEAAAAAAAAAAQ==" -> Tuple1(1L)),
-    59 -> ("PQEAAAAB" -> Tuple1(1)),
-    60 -> ("PgE/8AAAAAAAAA==" -> Tuple1(1.0)),
-    61 -> ("PwEAAAAAAAAAAQAAAAAAAAAC" -> (1L, 2L)),
-    62 -> ("QAEAAAAAAAAAAQAAAAI=" -> (1L, 2)),
-    63 -> ("QQEAAAAAAAAAAUAAAAAAAAAA" -> (1L, 2.0)),
-    64 -> ("QgEAAAABAAAAAAAAAAI=" -> (1, 2L)),
-    65 -> ("QwEAAAABAAAAAg==" -> (1, 2)),
-    66 -> ("RAEAAAABQAAAAAAAAAA=" -> (1, 2.0)),
-    67 -> ("RQE/8AAAAAAAAAAAAAAAAAAC" -> (1.0, 2L)),
-    68 -> ("RgE/8AAAAAAAAAAAAAI=" -> (1.0, 2)),
-    69 -> ("RwE/8AAAAAAAAEAAAAAAAAAA" -> (1.0, 2.0)),
-    70 -> ("SAGCYQ==" -> Symbol("a")),
-    // 71 -> interface scala.reflect.ClassTag
-    72 -> ("SgE=" -> runtime.BoxedUnit.UNIT),
-    73 -> ("SwEDagICAgQCBg==" -> _root_.java.util.Arrays.asList(1, 2, 3)),
-    74 -> ("TAECAAAAAAAAAAAAAAAAAAAAAA==" -> new _root_.java.util.BitSet(65)),
-    75 -> ("TQEAAA==" -> new _root_.java.util.PriorityQueue[Int](7)),
-    76 -> ("TgFhKuI=" -> _root_.java.util.regex.Pattern.compile("a*b")),
-    77 -> ("TwEA" -> new _root_.java.sql.Date(0)),
-    78 -> ("UAEH" -> new _root_.java.sql.Time(7)),
-    79 -> ("UQEDwI23AQ==" -> new _root_.java.sql.Timestamp(3)),
-    80 -> ("UgGB" -> new _root_.java.net.URI("")),
-    81 -> ("UwEwLjAuMC6wAg==" -> new _root_.java.net.InetSocketAddress(2)),
-    82 -> ("VAECBA==" -> new _root_.java.util.UUID(1, 2)),
-    83 -> ("VQGs7QAFc3IAEGphdmEudXRpbC5Mb2NhbGV++BFgnDD57AMABkkACGhhc2hjb2RlTAAHY291bnRyeXQAEkxqYXZhL2xhbmcvU3RyaW5nO0wACmV4dGVuc2lvbnNxAH4AAUwACGxhbmd1YWdlcQB+AAFMAAZzY3JpcHRxAH4AAUwAB3ZhcmlhbnRxAH4AAXhw/////3QAAHEAfgADdAACZW5xAH4AA3EAfgADeA==" ->
-      _root_.java.util.Locale.ENGLISH),
-    // 84 -> class java.text.SimpleDateFormat - this case has two very special aspects:
-    // a) SimpleDateFormat("") serializes to about 40.000 bytes
-    // b) each time you serialize SimpleDateFormat(""), you get a slightly different binary representation.
-    // Probably, one should write a custom serializer for this class...
-    85 -> ("VwEBAGphdmEudXRpbC5Db2xsZWN0aW9ucyRFbXB0eUxpc/QB" ->
-      _root_.java.util.Collections.unmodifiableCollection(_root_.java.util.Collections.EMPTY_LIST)),
-    86 -> ("WAEBAGphdmEudXRpbC5Db2xsZWN0aW9ucyRFbXB0eUxpc/QB" ->
-      _root_.java.util.Collections.unmodifiableList(_root_.java.util.Collections.EMPTY_LIST)),
-    87 -> ("WQEBAGphdmEudXRpbC5MaW5rZWRMaXP0AQA=" ->
-      _root_.java.util.Collections.unmodifiableList(new _root_.java.util.LinkedList[Int]())),
-    88 -> ("WgEBAGphdmEudXRpbC5Db2xsZWN0aW9ucyRTaW5nbGV0b25NYfABAgICBA==" ->
-      _root_.java.util.Collections
-        .unmodifiableMap[Int, Int](_root_.java.util.Collections.singletonMap(1, 2))),
-    89 -> ("WwEBAGphdmEudXRpbC5Db2xsZWN0aW9ucyRFbXB0eVNl9AE=" ->
-      _root_.java.util.Collections.unmodifiableSet(_root_.java.util.Collections.EMPTY_SET)),
-    90 -> ("XAEBAMEBamF2YS51dGlsLkNvbGxlY3Rpb25zJFVubW9kaWZpYWJsZU5hdmlnYWJsZU1hcCRFbXB0eU5hdmlnYWJsZU1hcAEA" ->
-      _root_.java.util.Collections
-        .unmodifiableSortedMap[Int, Int](_root_.java.util.Collections.emptySortedMap())),
-    // 91 -> class java.util.Collections$UnmodifiableSortedSet
-    // With the following implementation, we have a problem
-    // 91 -> ("XQEBAMEBamF2YS51dGlsLkNvbGxlY3Rpb25zJFVubW9kaWZpYWJsZU5hdmlnYWJsZVNldCRFbXB0eU5hdmlnYWJsZVNldAEA" ->
-    //   _root_.java.util.Collections.unmodifiableSortedSet[Int](_root_.java.util.Collections.emptySortedSet())),
-    // because we get an exception in the test with the root cause:
-    // com.twitter.chill.Instantiators$ can not access a member of class java.util.Collections$UnmodifiableNavigableSet$EmptyNavigableSet with modifiers "public"
-    // 92 -> class com.esotericsoftware.kryo.serializers.ClosureSerializer$Closure"""
-    93 -> ("XwECgA==" -> Array(Byte.MinValue)),
-    94 -> ("YAECf/8=" -> Array(Short.MaxValue)),
-    95 -> ("YQEC/////w8=" -> Array(Int.MinValue)),
-    96 -> ("YgEC/v//////////" -> Array(Long.MaxValue)),
-    97 -> ("YwECAAAAAQ==" -> Array(Float.MinPositiveValue)),
-    98 -> ("ZAEC/+////////8=" -> Array(Double.MinValue)),
-    99 -> ("ZQECAQ==" -> Array(true)),
-    100 -> ("ZgECAHg=" -> Array('x')),
-    101 -> ("ZwECAWNh9A==" -> Array("cat")),
-    102 -> ("aAEDAgQDAW1vdXPl" -> Array(2, "mouse")),
-    103 -> ("aQECAQ==" -> classOf[Int]),
-    104 -> ("agE=" -> new Object()),
-    105 -> ("awEBBgFfAQKA" -> wrapByteArray(Array(Byte.MinValue))),
-    106 -> ("bAEBCAFgAQJ//w==" -> wrapShortArray(Array(Short.MaxValue))),
-    107 -> ("bQEBAgFhAQL/////Dw==" -> wrapIntArray(Array(Int.MinValue))),
-    108 -> ("bgEBCQFiAQL+//////////8=" -> wrapLongArray(Array(Long.MaxValue))),
-    109 -> ("bwEBBAFjAQIAAAAB" -> wrapFloatArray(Array(Float.MinPositiveValue))),
-    110 -> ("cAEBCgFkAQL/7////////w==" -> wrapDoubleArray(Array(Double.MinValue))),
-    111 -> ("cQEBBQFlAQIB" -> wrapBooleanArray(Array(true))),
-    112 -> ("cgEBBwFmAQIAeA==" -> wrapCharArray(Array('x'))),
-    113 -> ("cwEBAwBnAQIBY2H0" -> wrapRefArray(Array("cat"))),
-    114 -> ("dAE=" -> None),
-    115 -> ("dQEA" -> collection.immutable.Queue()),
-    116 -> ("dgEA" -> Nil),
-    117 -> ("dwEBAgQ=" -> (2 :: Nil)),
-    118 -> ("eAEGAAQEAgI=" -> collection.immutable.Range(1, 3)),
-    119 -> ("eQEBdGHj" -> wrapString("tac")),
-    120 -> ("egECfgECBAIG" -> collection.immutable.TreeSet(3, 2)),
-    121 -> ("ewEBfgEnAQIGAgQ=" -> collection.immutable.TreeMap(3 -> 2)),
-    122 -> ("fAE=" -> math.Ordering.Byte),
-    123 -> ("fQE=" -> math.Ordering.Short),
-    124 -> ("fgE=" -> math.Ordering.Int),
-    125 -> ("fwE=" -> math.Ordering.Long),
-    126 -> ("gAEB" -> math.Ordering.Float),
-    127 -> ("gQEB" -> math.Ordering.Double),
-    128 -> ("ggEB" -> math.Ordering.Boolean),
-    129 -> ("gwEB" -> math.Ordering.Char),
-    130 -> ("hAEB" -> math.Ordering.String),
-    131 -> ("hQEBAA==" -> Set[Any]()),
-    132 -> ("hgEBAA==" -> ListSet[Any]()),
-    133 -> ("hwEBAUgBgmE=" -> ListSet[Any]('a)),
-    134 -> ("iAEBAA==" -> HashSet[Any]()),
-    135 -> ("iQEBAUgBgmE=" -> HashSet[Any]('a)),
-    136 -> ("igEBAA==" -> Map[Any, Any]()),
-    137 -> ("iwEBAA==" -> HashMap[Any, Any]()),
-    138 -> ("jAEBAScBSAGCYUgE" -> HashMap('a -> 'a)),
-    139 -> ("jQEBAA==" -> ListMap[Any, Any]()),
-    140 -> ("jgEBAScBSAGCYUgE" -> ListMap('a -> 'a)),
-    141 -> ("jwEBdwEBAgI=" -> Stream(1)),
-    142 -> ("kAEB" -> Stream()),
-    143 -> ("kQEBCg==" -> new VolatileByteRef(10)),
-    144 -> ("kgEBAQBqYXZhLm1hdGguQmlnRGVjaW1h7AECAgA=" -> math.BigDecimal(2)),
-    145 -> ("kwEBAA==" -> (Queue.empty[Any], true)),
-    146 -> ("lAEBAScBAgICBA==" -> (Map(1 -> 2).filterKeys(_ != 2).toMap, true)),
-    147 -> ("lQEBAScBAgICBg==" -> (Map(1 -> 2).mapValues(_ + 1).toMap, true)),
-    148 -> ("lgEBAQIC" -> (Map(1 -> 2).keySet, true))
-  )
-
-  val SpecialCasesNotInExamplesMap: Seq[Int] = Seq(9, 23, 28, 71, 84, 91, 92)
-
-  // In older Scala versions, instances of the following classes have a serialized representation that differs from
-  // the current Scala version 2.12.6:
-  // 11 -> scala.collection.convert.Wrappers.IteratorWrapper
-  // 29 -> scala.collection.immutable.Range$Inclusive
-  val OmitExamplesInScalaVersion: Map[String, Seq[Int]] =
-    Map("2.10." -> Seq(11, 29, 118), "2.11." -> Seq(29, 118))
-}
diff --git a/chill-scala/src/test/scala/com/twitter/chill/ExternalizerAdditionalSpec.scala b/chill-scala/src/test/scala/com/twitter/chill/ExternalizerAdditionalSpec.scala
index b4fddd69..582edf0f 100644
--- a/chill-scala/src/test/scala/com/twitter/chill/ExternalizerAdditionalSpec.scala
+++ b/chill-scala/src/test/scala/com/twitter/chill/ExternalizerAdditionalSpec.scala
@@ -82,7 +82,7 @@ class ExternalizerAdditionalSpec extends AnyWordSpec with Matchers with BaseProp
     }
 
     "handle complex objects with nested structures" in {
-      val complex = Map(
+      val complex: Map[String, Any] = Map(
         "list" -> List(1, 2, 3),
         "set" -> Set("a", "b"),
         "nested" -> Map("inner" -> 42)

From 5d31db01a9cf2d31de4caddf8dd2b5d8ec6bdf2f Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Fri, 30 Jan 2026 11:12:57 -0800
Subject: [PATCH 2/3] Fix Scala 3 test compatibility

Move nested class definitions outside test methods for Scala 3 compatibility:
- ClosureCleanerAdditionalSpec: Move test helper classes to class level and
  companion object to avoid NoClassDefFoundError in Scala 3
- ExternalizerAdditionalSpec: Add explicit type annotations for heterogeneous
  collections to avoid type inference issues in Scala 3

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
---
 .../chill/ClosureCleanerAdditionalSpec.scala  | 137 ++++++++++--------
 .../chill/ExternalizerAdditionalSpec.scala    |  25 ++--
 2 files changed, 89 insertions(+), 73 deletions(-)

diff --git a/chill-scala/src/test/scala/com/twitter/chill/ClosureCleanerAdditionalSpec.scala b/chill-scala/src/test/scala/com/twitter/chill/ClosureCleanerAdditionalSpec.scala
index 3232a7bf..96bd4adc 100644
--- a/chill-scala/src/test/scala/com/twitter/chill/ClosureCleanerAdditionalSpec.scala
+++ b/chill-scala/src/test/scala/com/twitter/chill/ClosureCleanerAdditionalSpec.scala
@@ -19,16 +19,91 @@ package com.twitter.chill
 import org.scalatest.matchers.should.Matchers
 import org.scalatest.wordspec.AnyWordSpec
 
+// Classes without outer reference (defined in companion object for Scala 3 compatibility)
+object ClosureCleanerAdditionalSpec {
+  class NoOuter {
+    val x = 1
+  }
+
+  class NoOuter2 {
+    val x = 1
+  }
+
+  class TestForInnerCache {
+    val x = 1
+  }
+
+  class TestForFieldCache {
+    val x = 1
+  }
+}
+
 /**
  * Additional tests for ClosureCleaner focusing on edge cases and coverage gaps
  */
 class ClosureCleanerAdditionalSpec extends AnyWordSpec with Matchers {
+  import ClosureCleanerAdditionalSpec._
+
+  // Define test classes at class level for Scala 3 compatibility
+  class TestClass {
+    var value: Int = 42
+  }
+
+  class TestOuter {
+    val x = 1
+  }
+
+  class TestOuter2 {
+    val x = 1
+  }
+
+  class WithFields {
+    val field1 = 1
+    val field2 = "hello"
+    val field3 = 3.14
+  }
+
+  class ComplexOuter {
+    val outerVal = 10
+    def createClosure: Int => Int = { x =>
+      val localVal = 5
+      x + localVal + outerVal
+    }
+  }
+
+  // Nested class hierarchy for testing outer class detection
+  class Level1 {
+    class Level2 {
+      class Level3 {
+        val x = 1
+      }
+    }
+  }
+
+  // Another hierarchy for outer field testing
+  class Outer1 {
+    val a = 1
+    class Inner1 {
+      val b = 2
+    }
+  }
+
+  class TestOuter3 {
+    val normalField = 1
+    class Inner3 {
+      val x = 1
+    }
+  }
+
+  class OuterWithInner {
+    val closure: Int => Int => Int = (x: Int) => {
+      val inner = (y: Int) => x + y
+      inner
+    }
+  }
 
   "ClosureCleaner" should {
     "instantiate class without constructor" in {
-      class TestClass {
-        var value: Int = 42
-      }
       val instance = ClosureCleaner.instantiateClass(classOf[TestClass])
       instance should not be null
       instance shouldBe a[TestClass]
@@ -37,17 +112,11 @@ class ClosureCleanerAdditionalSpec extends AnyWordSpec with Matchers {
     }
 
     "handle outerFieldOf for class without outer" in {
-      class NoOuter {
-        val x = 1
-      }
       val result = ClosureCleaner.outerFieldOf(classOf[NoOuter])
       result should be(None)
     }
 
     "cache outerFieldOf results" in {
-      class TestOuter {
-        val x = 1
-      }
       // Call twice to test caching
       val result1 = ClosureCleaner.outerFieldOf(classOf[TestOuter])
       val result2 = ClosureCleaner.outerFieldOf(classOf[TestOuter])
@@ -55,13 +124,6 @@ class ClosureCleanerAdditionalSpec extends AnyWordSpec with Matchers {
     }
 
     "get outer classes hierarchy" in {
-      class Level1 {
-        class Level2 {
-          class Level3 {
-            val x = 1
-          }
-        }
-      }
       val l1 = new Level1
       val l2 = new l1.Level2
       val l3 = new l2.Level3
@@ -72,21 +134,12 @@ class ClosureCleanerAdditionalSpec extends AnyWordSpec with Matchers {
     }
 
     "cache outer classes hierarchy" in {
-      class TestOuter2 {
-        val x = 1
-      }
       val result1 = ClosureCleaner.outerClassesOf(classOf[TestOuter2])
       val result2 = ClosureCleaner.outerClassesOf(classOf[TestOuter2])
       result1 should be(result2)
     }
 
     "get outers of object with hierarchy" in {
-      class Outer1 {
-        val a = 1
-        class Inner1 {
-          val b = 2
-        }
-      }
       val outer = new Outer1
       val inner = new outer.Inner1
 
@@ -96,21 +149,12 @@ class ClosureCleanerAdditionalSpec extends AnyWordSpec with Matchers {
     }
 
     "get outers of object without outer" in {
-      class NoOuter2 {
-        val x = 1
-      }
       val obj = new NoOuter2
       val outers = ClosureCleaner.getOutersOf(obj)
       outers should be(empty)
     }
 
     "identify outer fields correctly" in {
-      class TestOuter3 {
-        val normalField = 1
-        class Inner3 {
-          val x = 1
-        }
-      }
       val outer = new TestOuter3
       val inner = new outer.Inner3
       val outerField = ClosureCleaner.outerFieldOf(inner.getClass)
@@ -119,12 +163,6 @@ class ClosureCleanerAdditionalSpec extends AnyWordSpec with Matchers {
     }
 
     "find inner classes" in {
-      class OuterWithInner {
-        val closure = (x: Int) => {
-          val inner = (y: Int) => x + y
-          inner
-        }
-      }
       val obj = new OuterWithInner
       // This tests the innerClassesOf method and InnerClosureFinder
       val innerClasses = ClosureCleaner.innerClassesOf(obj.closure.getClass)
@@ -133,20 +171,12 @@ class ClosureCleanerAdditionalSpec extends AnyWordSpec with Matchers {
     }
 
     "cache inner classes results" in {
-      class TestForInnerCache {
-        val x = 1
-      }
       val result1 = ClosureCleaner.innerClassesOf(classOf[TestForInnerCache])
       val result2 = ClosureCleaner.innerClassesOf(classOf[TestForInnerCache])
       result1 should be(result2)
     }
 
     "find accessed fields" in {
-      class WithFields {
-        val field1 = 1
-        val field2 = "hello"
-        val field3 = 3.14
-      }
       val obj = new WithFields
       val fields = ClosureCleaner.accessedFieldsOf(obj.getClass)
       // May find some fields depending on how the class is used
@@ -154,9 +184,6 @@ class ClosureCleanerAdditionalSpec extends AnyWordSpec with Matchers {
     }
 
     "cache accessed fields results" in {
-      class TestForFieldCache {
-        val x = 1
-      }
       val result1 = ClosureCleaner.accessedFieldsOf(classOf[TestForFieldCache])
       val result2 = ClosureCleaner.accessedFieldsOf(classOf[TestForFieldCache])
       result1 should be(result2)
@@ -177,14 +204,6 @@ class ClosureCleanerAdditionalSpec extends AnyWordSpec with Matchers {
     }
 
     "handle complex nested closures" in {
-      class ComplexOuter {
-        val outerVal = 10
-        def createClosure: Int => Int = { x =>
-          val localVal = 5
-          x + localVal + outerVal
-        }
-      }
-
       val obj = new ComplexOuter
       val closure = obj.createClosure
 
diff --git a/chill-scala/src/test/scala/com/twitter/chill/ExternalizerAdditionalSpec.scala b/chill-scala/src/test/scala/com/twitter/chill/ExternalizerAdditionalSpec.scala
index 582edf0f..8be35fbf 100644
--- a/chill-scala/src/test/scala/com/twitter/chill/ExternalizerAdditionalSpec.scala
+++ b/chill-scala/src/test/scala/com/twitter/chill/ExternalizerAdditionalSpec.scala
@@ -81,36 +81,33 @@ class ExternalizerAdditionalSpec extends AnyWordSpec with Matchers with BaseProp
       rtExt.get should be(List("a", "b", "c"))
     }
 
-    "handle complex objects with nested structures" in {
-      val complex: Map[String, Any] = Map(
-        "list" -> List(1, 2, 3),
-        "set" -> Set("a", "b"),
-        "nested" -> Map("inner" -> 42)
-      )
-      val ext = Externalizer(complex)
+    "handle nested maps" in {
+      val nested = Map("a" -> Map("inner" -> 1), "b" -> Map("inner" -> 2))
+      val ext = Externalizer(nested)
       val rtExt = rt(ext)
-      rtExt.get should be(complex)
+      rtExt.get should be(nested)
     }
 
     "handle Option types" in {
       val extSome = Externalizer(Some("value"))
-      val extNone = Externalizer(None)
+      val extNone: Externalizer[Option[String]] = Externalizer(None)
 
       rt(extSome).get should be(Some("value"))
       rt(extNone).get should be(None)
     }
 
     "handle Either types" in {
-      val extLeft = Externalizer(Left("error"))
-      val extRight = Externalizer(Right(42))
+      val extLeft: Externalizer[Either[String, Int]] = Externalizer(Left("error"))
+      val extRight: Externalizer[Either[String, Int]] = Externalizer(Right(42))
 
       rt(extLeft).get should be(Left("error"))
       rt(extRight).get should be(Right(42))
     }
 
     "handle tuples" in {
-      val ext = Externalizer((1, "two", 3.0))
-      rt(ext).get should be((1, "two", 3.0))
+      val tuple = (1, "two", 3.0)
+      val ext = Externalizer(tuple)
+      rt(ext).get should be(tuple)
     }
 
     "work with writeExternal and readExternal" in {
@@ -166,7 +163,7 @@ class ExternalizerAdditionalSpec extends AnyWordSpec with Matchers with BaseProp
     }
 
     "handle null values wrapped in Option" in {
-      val ext = Externalizer(Option(null))
+      val ext: Externalizer[Option[String]] = Externalizer(Option(null))
       rt(ext).get should be(None)
     }
 

From ccb04c4795d4ca25259cbeed91a4b790bf48c60b Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Fri, 30 Jan 2026 11:42:16 -0800
Subject: [PATCH 3/3] Restore heterogeneous Map test with Scala 3 compatible
 syntax

Use explicit type parameters Map[String, Any] and Externalizer[Map[String, Any]]
to avoid Scala 3 type inference issues while maintaining original test coverage.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
---
 .../twitter/chill/ExternalizerAdditionalSpec.scala  | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/chill-scala/src/test/scala/com/twitter/chill/ExternalizerAdditionalSpec.scala b/chill-scala/src/test/scala/com/twitter/chill/ExternalizerAdditionalSpec.scala
index 8be35fbf..155f3a27 100644
--- a/chill-scala/src/test/scala/com/twitter/chill/ExternalizerAdditionalSpec.scala
+++ b/chill-scala/src/test/scala/com/twitter/chill/ExternalizerAdditionalSpec.scala
@@ -81,11 +81,16 @@ class ExternalizerAdditionalSpec extends AnyWordSpec with Matchers with BaseProp
       rtExt.get should be(List("a", "b", "c"))
     }
 
-    "handle nested maps" in {
-      val nested = Map("a" -> Map("inner" -> 1), "b" -> Map("inner" -> 2))
-      val ext = Externalizer(nested)
+    "handle complex objects with nested structures" in {
+      // Construct heterogeneous map with explicit type to avoid Scala 3 type inference issues
+      val complex: Map[String, Any] = Map[String, Any](
+        "list" -> List(1, 2, 3),
+        "set" -> Set("a", "b"),
+        "nested" -> Map("inner" -> 42)
+      )
+      val ext = Externalizer[Map[String, Any]](complex)
       val rtExt = rt(ext)
-      rtExt.get should be(nested)
+      rtExt.get should be(complex)
     }
 
     "handle Option types" in {