[K/N] Provide original class id for forward-declared declarataion

core/descriptors/src/org/jetbrains/kotlin/types/KotlinTypeFactory.kt

@@ -22,6 +22,7 @@ import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
 import org.jetbrains.kotlin.descriptors.annotations.Annotations
 import org.jetbrains.kotlin.descriptors.impl.getRefinedMemberScopeIfPossible
 import org.jetbrains.kotlin.descriptors.impl.getRefinedUnsubstitutedMemberScopeIfPossible
+import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.resolve.constants.IntegerLiteralTypeConstructor
 import org.jetbrains.kotlin.resolve.descriptorUtil.getKotlinTypeRefiner
 import org.jetbrains.kotlin.resolve.descriptorUtil.module
@@ -226,6 +227,31 @@ private class SimpleTypeImpl(
     }
 }
 
+// Note: a hack to support class descriptor overwriting in case of K/N forward declaration replacement and other such cases
+class SupposititiousSimpleType(private val realType: SimpleType, val overwrittenClass: ClassId) : SimpleType() {
+
+    private fun maybeWrap(newType: SimpleType): SupposititiousSimpleType {
+        return if (newType === realType) this
+        else SupposititiousSimpleType(newType, overwrittenClass)
+    }
+
+    override fun replaceAnnotations(newAnnotations: Annotations): SimpleType =
+            maybeWrap(realType.replaceAnnotations(newAnnotations))
+
+    override fun makeNullableAsSpecified(newNullability: Boolean): SimpleType =
+            maybeWrap(realType.makeNullableAsSpecified(newNullability))
+
+    @TypeRefinement
+    override fun refine(kotlinTypeRefiner: KotlinTypeRefiner): SimpleType =
+            maybeWrap(realType.refine(kotlinTypeRefiner))
+
+    override val constructor: TypeConstructor = realType.constructor
+    override val arguments: List<TypeProjection> = realType.arguments
+    override val isMarkedNullable: Boolean = realType.isMarkedNullable
+    override val memberScope: MemberScope = realType.memberScope
+    override val annotations: Annotations = realType.annotations
+}
+
 abstract class DelegatingSimpleTypeImpl(override val delegate: SimpleType) : DelegatingSimpleType() {
     override fun replaceAnnotations(newAnnotations: Annotations) =
         if (newAnnotations !== annotations)

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/TypeDeserializer.kt

@@ -11,6 +11,8 @@ import org.jetbrains.kotlin.descriptors.annotations.Annotations
 import org.jetbrains.kotlin.metadata.ProtoBuf
 import org.jetbrains.kotlin.metadata.deserialization.*
 import org.jetbrains.kotlin.name.ClassId
+import org.jetbrains.kotlin.name.FqName
+import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameOrNull
 import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
 import org.jetbrains.kotlin.serialization.deserialization.descriptors.DeserializedAnnotations
@@ -94,8 +96,25 @@ class TypeDeserializer(
             KotlinTypeFactory.simpleType(annotations, constructor, arguments, proto.nullable)
         }
 
-        val abbreviatedTypeProto = proto.abbreviatedType(c.typeTable) ?: return simpleType
+        val computedType = proto.abbreviatedType(c.typeTable)?.let {
-        return simpleType.withAbbreviation(simpleType(abbreviatedTypeProto))
+            simpleType.withAbbreviation(simpleType(it))
+        } ?: simpleType
+
+        // TODO: move this hack in some platform specific place ASAP
+        if (proto.hasClassName()) {
+            val classId = c.nameResolver.getClassId(proto.className)
+            val originalPackageFqn = classId.packageFqName
+            if (originalPackageFqn in forwardPackagesSet) {
+                // This hack is about keeping original class id written into proto which is required for correct IR linkage
+                val classDescriptor = constructor.declarationDescriptor as ClassDescriptor
+                val realPackageFqn = (classDescriptor.containingDeclaration as PackageFragmentDescriptor).fqName
+                if (originalPackageFqn != realPackageFqn) {
+                    return SupposititiousSimpleType(computedType, classId)
+                }
+            }
+        }
+
+        return computedType
     }
 
     private fun typeConstructor(proto: ProtoBuf.Type): TypeConstructor {
@@ -253,4 +272,15 @@ class TypeDeserializer(
     }
 
     override fun toString() = debugName + (if (parent == null) "" else ". Child of ${parent.debugName}")
+
+    companion object {
+        private val cNames = FqName("cnames")
+        private val cNamesStructs = cNames.child(Name.identifier("structs"))
+
+        private val objCNames = FqName("objcnames")
+        private val objCNamesClasses = objCNames.child(Name.identifier("classes"))
+        private val objCNamesProtocols = objCNames.child(Name.identifier("protocols"))
+
+        private val forwardPackagesSet = setOf(cNamesStructs, objCNamesClasses, objCNamesProtocols)
+    }
 }