Fixing bug and adding testcases

Author: EnzeXing

compiler/src/dotty/tools/dotc/transform/init/Objects.scala

@@ -865,7 +865,7 @@ class Objects(using Context @constructorOnly):
       Bottom
 
     case Bottom =>
-      if field.isStaticObject then ObjectRef(field.moduleClass.asClass)
+      if field.isStaticObject then accessObject(field.moduleClass.asClass)
       else Bottom
 
     case ValueSet(values) =>

tests/init-global/warn/cyclic-object.scala

@@ -0,0 +1,9 @@
+package cyclicObject
+
+object O1 { // warn
+  val o = cyclicObject.O2
+}
+
+object O2 {
+  val o = cyclicObject.O1
+}

tests/init-global/warn/deadlock.scala

@@ -0,0 +1,26 @@
+// example of cyclic initialization causing deadlock
+
+package pkg
+
+object Main extends App {
+  val createPredef = new Runnable { def run = { val _ = Predef } }
+  val createSeq = new Runnable { def run = { val _ = Seq } }
+  new Thread(createPredef).start()
+  new Thread(createSeq).start()
+  Thread.sleep(100)
+  val seq = Predef.seq
+  val predef = Seq.predef
+  println("done")
+}
+
+object Predef { // warn
+  Thread.sleep(10)
+  val seq = Seq
+  println("done Predef")
+}
+
+object Seq {
+  Thread.sleep(10)
+  val predef = Predef
+  println("done Seq")
+}