Both module and class being unpickled need to register links.

Author: DarkDimius

src/dotty/tools/dotc/core/pickling/UnPickler.scala

@@ -120,16 +120,22 @@ object UnPickler {
     if (!(denot.flagsUNSAFE is JavaModule)) ensureConstructor(denot.symbol.asClass, decls)
 
     val scalacCompanion = denot.classSymbol.scalacLinkedClass
-    if (denot.flagsUNSAFE is Module) {
-      val companionClassMethod = ctx.synthesizeCompanionMethod(nme.COMPANION_CLASS_METHOD, scalacCompanion, denot.classSymbol)
+
+    def registerCompanionPair(module: Symbol, claz: Symbol) = {
+      val companionClassMethod = ctx.synthesizeCompanionMethod(nme.COMPANION_CLASS_METHOD, claz, module)
       if (companionClassMethod.exists)
         companionClassMethod.entered
-    } else {
-      val companionModuleMethod = ctx.synthesizeCompanionMethod(nme.COMPANION_MODULE_METHOD, scalacCompanion, denot.classSymbol)
+      val companionModuleMethod = ctx.synthesizeCompanionMethod(nme.COMPANION_MODULE_METHOD, module, claz)
       if (companionModuleMethod.exists)
         companionModuleMethod.entered
     }
 
+    if (denot.flagsUNSAFE is Module) {
+      registerCompanionPair(denot.classSymbol, scalacCompanion)
+    } else {
+      registerCompanionPair(scalacCompanion, denot.classSymbol)
+    }
+
     denot.info = ClassInfo(denot.owner.thisType, denot.classSymbol, parentRefs, decls, ost)
   }
 }