From 2f717a41ad002789309894bfb4fd43cb25d26c2a Mon Sep 17 00:00:00 2001
From: Guillaume Martres <smarter@ubuntu.com>
Date: Mon, 14 Mar 2022 16:27:00 +0100
Subject: [PATCH] Emit all classes as public to avoid object deserialization
 issues

This aligns our behavior with Scala 2 and fixes the issue encountered in
https://github.com/typelevel/cats-effect/pull/2360#issuecomment-1066895758.

Alternatively, we could change ModuleSerializationProxy upstream to call
`setAccessible(true)` on the MODULE$ field, but this wouldn't work if the object
in question is inside a Java 9+ module.
---
 .../tools/backend/jvm/BTypesFromSymbols.scala     |  6 +++++-
 tests/run/i4404a.check                            | 12 ++++--------
 tests/run/i4404a.scala                            | 12 +++++-------
 tests/run/i4404b.check                            |  2 +-
 tests/run/serialize.scala                         | 15 +++++++++++++++
 5 files changed, 30 insertions(+), 17 deletions(-)

diff --git a/compiler/src/dotty/tools/backend/jvm/BTypesFromSymbols.scala b/compiler/src/dotty/tools/backend/jvm/BTypesFromSymbols.scala
index 25a05077626a..dbdc92f95e9f 100644
--- a/compiler/src/dotty/tools/backend/jvm/BTypesFromSymbols.scala
+++ b/compiler/src/dotty/tools/backend/jvm/BTypesFromSymbols.scala
@@ -296,7 +296,11 @@ class BTypesFromSymbols[I <: DottyBackendInterface](val int: I) extends BTypes {
    */
   final def javaFlags(sym: Symbol): Int = {
 
-    val privateFlag = sym.is(Private) || (sym.isPrimaryConstructor && sym.owner.isTopLevelModuleClass)
+    // Classes are always emitted as public. This matches the behavior of Scala 2
+    // and is necessary for object deserialization to work properly, otherwise
+    // ModuleSerializationProxy may fail with an accessiblity error (see
+    // tests/run/serialize.scala).
+    val privateFlag = !sym.isClass && (sym.is(Private) || (sym.isPrimaryConstructor && sym.owner.isTopLevelModuleClass))
 
     val finalFlag = sym.is(Final) && !toDenot(sym).isClassConstructor && !sym.is(Mutable) && !sym.enclosingClass.is(Trait)
 
diff --git a/tests/run/i4404a.check b/tests/run/i4404a.check
index 11444aa1f1fe..fa056b1cd9d5 100644
--- a/tests/run/i4404a.check
+++ b/tests/run/i4404a.check
@@ -1,8 +1,4 @@
-false
-false
-false
-true
-false
-true
-true
-true
+public class Car
+public final class Volvo
+public final class Car$
+public static final class Car$$anon$1
diff --git a/tests/run/i4404a.scala b/tests/run/i4404a.scala
index b322218cf930..41d5e7064714 100644
--- a/tests/run/i4404a.scala
+++ b/tests/run/i4404a.scala
@@ -8,12 +8,10 @@ object Car {
 }
 
 object Test {
-  def main(args: Array[String]) = {
-    List(new Car, new Volvo, Car, Car.car)
-      .map(_.getClass.getModifiers)
-      .foreach { m =>
-        println(Modifier.isPrivate(m))
-        println(Modifier.isFinal(m))
-      }
+  def main(args: Array[String]): Unit = {
+    val l =  List(new Car, new Volvo, Car, Car.car)
+      .map(_.getClass)
+      .map(cls => s"${Modifier.toString(cls.getModifiers)} $cls")
+    println(l.mkString("\n"))
   }
 }
diff --git a/tests/run/i4404b.check b/tests/run/i4404b.check
index bb101b641b9b..1d474d525571 100644
--- a/tests/run/i4404b.check
+++ b/tests/run/i4404b.check
@@ -1,2 +1,2 @@
-true
+false
 true
diff --git a/tests/run/serialize.scala b/tests/run/serialize.scala
index 0622807bee21..830c2935ac97 100644
--- a/tests/run/serialize.scala
+++ b/tests/run/serialize.scala
@@ -1,3 +1,14 @@
+package a {
+  object Outer extends Serializable {
+    private object Inner extends Serializable
+
+    val inner: AnyRef = Inner
+  }
+  class Bar extends Serializable {
+    val x: AnyRef = Outer.inner
+  }
+}
+
 object Test {
   def serializeDeserialize[T <: AnyRef](obj: T): T = {
     import java.io.*
@@ -26,5 +37,9 @@ object Test {
 
     val baz = serializeDeserialize(Baz)
     assert(baz ne Baz)
+
+    val bar = new a.Bar
+    val bar1 = serializeDeserialize(bar)
+    assert(bar.x eq bar1.x)
   }
 }