Refine trace and error message for cycles

Author: liufengyun

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

@@ -146,15 +146,15 @@ class CycleChecker(cache: Cache) {
       val obj = dep.symbol
       if state.path.contains(obj) then
         val cycle = state.path.dropWhile(_ != obj)
-        val trace = state.trace.map(_.source) :+ dep.source
+        val trace = state.trace.dropWhile(_.symbol != obj).map(_.source) :+ dep.source
         if cycle.size > 1 then
-          CyclicObjectInit(obj, trace) :: Nil
+          CyclicObjectInit(cycle, trace) :: Nil
         else
           ObjectLeakDuringInit(obj, trace) :: Nil
       else
         val constr = obj.moduleClass.primaryConstructor
         state.visitObject(dep) {
-          check(StaticCall(constr.owner.asClass, constr)(constr.defTree))
+          check(StaticCall(constr.owner.asClass, constr)(obj.moduleClass.defTree))
         }
     }
 

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

@@ -69,13 +69,13 @@ object Errors {
       report.warning(show + stacktrace, field.srcPos)
   }
 
-  case class CyclicObjectInit(obj: Symbol, trace: Seq[Tree]) extends Error {
+  case class CyclicObjectInit(objs: Seq[Symbol], trace: Seq[Tree]) extends Error {
     def source: Tree = trace.last
     def show(using Context): String =
-      "Cyclic object initialization of " + obj.show + "."
+      "Cyclic object initialization for " + objs.map(_.show).mkString(", ") + "."
 
     override def issue(using Context): Unit =
-      report.warning(show + stacktrace, obj.srcPos)
+      report.warning(show + stacktrace, objs.head.srcPos)
   }
 
   case class ObjectLeakDuringInit(obj: Symbol, trace: Seq[Tree]) extends Error {