[backport] SI-9375 add synthetic readResolve only for static modules

For inner modules, the synthetic readResolve method would cause the
module constructor to be invoked on de-serialization in certain
situations. See the discussion in the ticket.

Adds a comprehensive test around serializing and de-serializing
modules.

7 files changed, 356 insertions, 7 deletions

diff --git a/test/files/neg/t6666d.check b/test/files/neg/t6666d.check
deleted file mode 100644
index b4785f0129..0000000000
--- a/test/files/neg/t6666d.check
+++ /dev/null
@@ -1,4 +0,0 @@
-t6666d.scala:7: error: Implementation restriction: access of object TreeOrd$1 from object TreeOrd$2, would require illegal premature access to the unconstructed `this` of class Test
-    implicit object TreeOrd extends Ordering[K](){
-                    ^
-one error found
diff --git a/test/files/neg/t6666d.scala b/test/files/pos/t6666d.scala
index 49a688f91b..49a688f91b 100644
--- a/test/files/neg/t6666d.scala
+++ b/test/files/pos/t6666d.scala
diff --git a/test/files/run/idempotency-case-classes.check b/test/files/run/idempotency-case-classes.check
index 5a8d0ad9d3..ea698cec59 100644
--- a/test/files/run/idempotency-case-classes.check
+++ b/test/files/run/idempotency-case-classes.check
@@ -47,8 +47,7 @@ C(2,3)
     case <synthetic> def unapply(x$0: C): Option[(Int, Int)] = if (x$0.==(null))
       scala.this.None
     else
-      Some.apply[(Int, Int)](scala.Tuple2.apply[Int, Int](x$0.x, x$0.y));
-    <synthetic> private def readResolve(): Object = C
+      Some.apply[(Int, Int)](scala.Tuple2.apply[Int, Int](x$0.x, x$0.y))
   };
   Predef.println(C.apply(2, 3))
 }
diff --git a/test/files/run/repl-serialization.check b/test/files/run/repl-serialization.check
index eb62729f5c..bbbf0dcdf1 100644
--- a/test/files/run/repl-serialization.check
+++ b/test/files/run/repl-serialization.check
@@ -20,6 +20,5 @@ u: U = U
   evaluating O
   constructing A
 == reconstituting into a fresh classloader
-  evaluating O
 == evaluating reconstituted lambda
   constructing A
diff --git a/test/files/run/t9375.check b/test/files/run/t9375.check
new file mode 100644
index 0000000000..87551dccd1
--- /dev/null
+++ b/test/files/run/t9375.check
@@ -0,0 +1,60 @@
+  konstruktor: class A
+  konstruktor: class A$O$12$
+  konstruktor: class A$$anon$1
+  konstruktor: class A$A
+  konstruktor: class A$C
+  konstruktor: class C
+  konstruktor: class T$O$15$
+  konstruktor: class T$$anon$2
+  konstruktor: class T$A
+  konstruktor: class T$C
+  konstruktor: class A$N$
+  konstruktor: class T$N$
+serializing outer objects should not initialize any nested objects
+now initializing nested objects
+  konstruktor: class A$O$
+  konstruktor: class A$Op$
+  konstruktor: class A$N$O$
+  konstruktor: class A$N$Op$
+  konstruktor: class A$A$O$
+  konstruktor: class A$A$Op$
+  konstruktor: class A$T$O$
+  konstruktor: class A$T$Op$
+  konstruktor: class A$O$11$
+  konstruktor: class A$$anonfun$1$O$13$
+  konstruktor: class A$$anon$1$O$
+  konstruktor: class A$$anon$1$Op$
+  konstruktor: class T$O$
+  konstruktor: class T$Op$
+  konstruktor: class T$N$O$
+  konstruktor: class T$N$Op$
+  konstruktor: class T$A$O$
+  konstruktor: class T$A$Op$
+  konstruktor: class T$T$O$
+  konstruktor: class T$T$Op$
+  konstruktor: class T$O$14$
+  konstruktor: class T$$anonfun$2$O$16$
+  konstruktor: class T$$anon$2$O$
+  konstruktor: class T$$anon$2$Op$
+no object konstruktors called when serializing / deserializing objects (starting at the outer or the object itself)
+deserializing outer objects with non-initialized inners again
+accessing modules triggers initialization
+  konstruktor: class A$O$
+  konstruktor: class A$Op$
+  konstruktor: class A$N$O$
+  konstruktor: class A$N$Op$
+deserializing creates a new object graph, including new scala 'object' instances, no matter where serialization starts
+init static module M and field v
+  konstruktor: class M$
+  konstruktor: class M$O$18$
+serDeser does not initialize nested static modules
+init M.O
+  konstruktor: class M$O$
+serDeser nested static module
+objects declared in field decls are not static modules, so they deserialize to new instances
+init lazy val M.w
+objects declared in lazy val are not static modules either
+  konstruktor: class M$O$19$
+object declared in a function: new instance created on each invocation
+  konstruktor: class M$$anonfun$3$O$20$
+  konstruktor: class M$$anonfun$3$O$20$
diff --git a/test/files/run/t9375.scala b/test/files/run/t9375.scala
new file mode 100644
index 0000000000..6ff4a425f8
--- /dev/null
+++ b/test/files/run/t9375.scala
@@ -0,0 +1,279 @@
+/*
+ * filter: inliner warning
+ */
+import java.io._
+
+object SerDes {
+  def serialize(obj: AnyRef): Array[Byte] = {
+    val buffer = new ByteArrayOutputStream
+    val out = new ObjectOutputStream(buffer)
+    out.writeObject(obj)
+    buffer.toByteArray
+  }
+
+  def deserialize(a: Array[Byte]): AnyRef = {
+    val in = new ObjectInputStream(new ByteArrayInputStream(a))
+    in.readObject
+  }
+
+  def serializeDeserialize[T <: AnyRef](obj: T) = deserialize(serialize(obj)).asInstanceOf[T]
+}
+
+import SerDes._
+
+// tests to make sure that de-serializing an object does not run its constructor
+
+trait S extends Serializable {
+  println("  konstruktor: " + this.getClass)
+}
+
+trait SE extends S {
+  def outer: Object
+}
+
+class A extends S {
+  object O extends SE { def outer = A.this }
+  private[this] object Op extends SE { def outer = A.this }
+  def P: SE = Op
+
+  object N extends S {
+    object O extends SE { def outer = N }
+    private[this] object Op extends SE { def outer = N }
+    def P: SE = Op
+  }
+
+  class A extends S {
+    object O extends SE { def outer = A.this }
+    private[this] object Op extends SE { def outer = A.this }
+    def P: SE = Op
+  }
+
+  trait T extends S {
+    object O extends SE { def outer = T.this }
+    private[this] object Op extends SE { def outer = T.this }
+    def P: SE = Op
+  }
+  class C extends T
+
+  def u: SE = {
+    object O extends SE { def outer = A.this }
+    O
+  }
+
+  val v: SE = {
+    object O extends SE { def outer = A.this }
+    O
+  }
+
+  val f: () => SE = () => {
+    object O extends SE { def outer = A.this }
+    O
+  }
+
+  trait GetObj { def O: SE; def P: SE }
+  val a: GetObj = new GetObj with S {
+    def anonThis = this
+    object O extends SE { def outer = anonThis }
+    private[this] object Op extends SE { def outer = anonThis }
+    def P: SE = Op
+  }
+}
+
+trait T extends S {
+  object O extends SE { def outer = T.this }
+  private[this] object Op extends SE { def outer = T.this }
+  def P: SE = Op
+
+  object N extends S {
+    object O extends SE { def outer = N }
+    private[this] object Op extends SE { def outer = N }
+    def P: SE = Op
+  }
+
+  class A extends S {
+    object O extends SE { def outer = A.this }
+    private[this] object Op extends SE { def outer = A.this }
+    def P: SE = Op
+  }
+
+  trait T extends S {
+    object O extends SE { def outer = T.this }
+    private[this] object Op extends SE { def outer = T.this }
+    def P: SE = Op
+  }
+  class C extends T
+
+  def u: SE = {
+    object O extends SE { def outer = T.this }
+    O
+  }
+
+  val v: SE = {
+    object O extends SE { def outer = T.this }
+    O
+  }
+
+  val f: () => SE = () => {
+    object O extends SE { def outer = T.this }
+    O
+  }
+
+  trait GetObj { def O: SE; def P: SE }
+  val a: GetObj = new GetObj with S {
+    def anonThis = this
+    object O extends SE { def outer = anonThis }
+    private[this] object Op extends SE { def outer = anonThis }
+    def P: SE = Op
+  }
+}
+
+class C extends T
+
+object DeserializeModuleNoConstructor {
+  def t(): Unit = {
+    val a = new A
+    val aa = new a.A
+    val ac = new a.C
+
+    val c = new C
+    val ca = new c.A
+    val cc = new c.C
+
+    val outers: List[Object] = List(
+      a, a.N, aa, ac, a.a,
+      c, c.N, ca, cc, c.a
+    )
+
+    println("serializing outer objects should not initialize any nested objects")
+
+    val serANotInit = serialize(a)
+    outers foreach serializeDeserialize
+
+    println("now initializing nested objects")
+
+    val os: List[(SE, Object)] = List(
+      a.O   -> a,
+      a.P   -> a,
+      a.N.O -> a.N,
+      a.N.P -> a.N,
+      aa.O  -> aa,
+      aa.P  -> aa,
+      ac.O  -> ac,
+      ac.P  -> ac,
+      a.u   -> a,
+      a.v   -> a,
+      a.f() -> a,
+      a.a.O -> a.a,
+      a.a.P -> a.a,
+
+      c.O   -> c,
+      c.P   -> c,
+      c.N.O -> c.N,
+      c.N.P -> c.N,
+      ca.O  -> ca,
+      ca.P  -> ca,
+      cc.O  -> cc,
+      cc.P  -> cc,
+      c.u   -> c,
+      c.v   -> c,
+      c.f() -> c,
+      c.a.O -> c.a,
+      c.a.P -> c.a
+    )
+
+    println("no object konstruktors called when serializing / deserializing objects (starting at the outer or the object itself)")
+
+    for ((obj, outer) <- os) {
+      assert(obj.outer eq outer, s"${obj.outer} of $obj -- $outer")
+      serializeDeserialize(obj)
+      serializeDeserialize(outer)
+    }
+
+    println("deserializing outer objects with non-initialized inners again")
+    val aNotInit = deserialize(serANotInit).asInstanceOf[A]
+
+    println("accessing modules triggers initialization")
+    aNotInit.O
+    aNotInit.P
+    aNotInit.N.O
+    aNotInit.N.P
+
+    println("deserializing creates a new object graph, including new scala 'object' instances, no matter where serialization starts")
+    val deserializedAs: List[A] = List(
+      serializeDeserialize(a),
+      serializeDeserialize(a.O).outer.asInstanceOf[A],
+      serializeDeserialize(a.P).outer.asInstanceOf[A],
+      serializeDeserialize(a.v).outer.asInstanceOf[A]
+    )
+    for (aSD <- deserializedAs) {
+      assert(aSD ne a)
+      assert(aSD.O ne a.O)
+      assert(aSD.P ne a.P)
+      assert(aSD.N ne a.N)
+      assert(aSD.N.O ne a.N.O)
+      assert(aSD.N.P ne a.N.P)
+      assert(aSD.v ne a.v)
+      assert(aSD.a.O ne a.a.O)
+      assert(aSD.a.P ne a.a.P)
+    }
+  }
+}
+
+// tests for serializing / deserializing static modules
+
+object M extends S {
+  object O extends S
+
+  def u: S = {
+    object O extends S
+    O
+  }
+
+  val v: S = {
+    object O extends S
+    O
+  }
+
+  lazy val w: S = {
+    object O extends S
+    O
+  }
+
+  val f: () => S = () => {
+    object O extends S
+    O
+  }
+}
+
+object SerializingStaticModules {
+  def t(): Unit = {
+    println("init static module M and field v")
+    M
+
+    println("serDeser does not initialize nested static modules")
+    assert(serializeDeserialize(M) eq M)
+
+    println("init M.O")
+    M.O
+
+    println("serDeser nested static module")
+    assert(serializeDeserialize(M.O) eq M.O)
+
+    println("objects declared in field decls are not static modules, so they deserialize to new instances")
+    assert(serializeDeserialize(M.v) ne M.v)
+
+    println("init lazy val M.w")
+
+    println("objects declared in lazy val are not static modules either")
+    assert(serializeDeserialize(M.w) ne M.w)
+
+    println("object declared in a function: new instance created on each invocation")
+    assert(M.f() ne M.f())
+  }
+}
+
+
+object Test extends App {
+  DeserializeModuleNoConstructor.t()
+  SerializingStaticModules.t()
+}
diff --git a/test/files/run/t9388-bin-compat.scala b/test/files/run/t9388-bin-compat.scala
new file mode 100644
index 0000000000..a03646612f
--- /dev/null
+++ b/test/files/run/t9388-bin-compat.scala
@@ -0,0 +1,16 @@
+class C {
+  private object N extends Serializable { override def toString = "N" }
+  def foo = N.toString
+}
+object Test {
+  def main(args: Array[String]): Unit = {
+    val c = Class.forName("C")
+    assert(c.getDeclaredFields().toList.map(_.toString) ==
+      List("private volatile C$N$ C.C$$N$module")) // field is name-mangled (C$$N$module instead of just N$module)
+    assert(c.getDeclaredMethods().toList.map(_.toString).sorted ==
+      List("private C$N$ C.C$$N$lzycompute()",
+           "public C$N$ C.C$$N()",
+           "public java.lang.String C.foo()")) // accessor is public, name-mangled
+    assert((new C).foo == "N")
+  }
+}