Make ClassDescriptor#classId nullable

Local classes or anonymous objects do not have a class id. Use "!!" almost
everywhere to make assertion explicit

core/descriptors/src/org/jetbrains/kotlin/resolve/DescriptorUtils.kt

@@ -74,16 +74,13 @@ val ClassifierDescriptorWithTypeParameters.denotedClassDescriptor: ClassDescript
         else -> throw UnsupportedOperationException("Unexpected descriptor kind: $this")
     }
 
-val ClassDescriptor.classId: ClassId
-    get() {
-        val owner = containingDeclaration
-        if (owner is PackageFragmentDescriptor) {
-            return ClassId(owner.fqName, name)
+val ClassDescriptor.classId: ClassId?
+    get() = containingDeclaration.let { owner ->
+        when (owner) {
+            is PackageFragmentDescriptor -> ClassId(owner.fqName, name)
+            is ClassDescriptor -> owner.classId?.createNestedClassId(name)
+            else -> null
         }
-        else if (owner is ClassDescriptor) {
-            return owner.classId.createNestedClassId(name)
-        }
-        throw IllegalStateException("Illegal container: $owner")
     }
 
 val ClassifierDescriptorWithTypeParameters.hasCompanionObject: Boolean

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/descriptors/DeserializedClassDescriptor.kt

@@ -161,7 +161,7 @@ class DeserializedClassDescriptor(
             if (unresolved.isNotEmpty()) {
                 c.components.errorReporter.reportIncompleteHierarchy(
                         this@DeserializedClassDescriptor,
-                        unresolved.map { it.classId.asSingleFqName().asString() }
+                        unresolved.map { it.classId?.asSingleFqName()?.asString() ?: it.name.asString() }
                 )
             }
 

core/reflection.jvm/src/kotlin/reflect/jvm/internal/RuntimeTypeMapper.kt

@@ -271,7 +271,7 @@ internal object RuntimeTypeMapper {
 
         val classId = klass.classId
         if (!classId.isLocal) {
-            JavaToKotlinClassMap.INSTANCE.mapJavaToKotlin(classId.asSingleFqName(), DefaultBuiltIns.Instance)?.let { return it.classId }
+            JavaToKotlinClassMap.INSTANCE.mapJavaToKotlin(classId.asSingleFqName(), DefaultBuiltIns.Instance)?.let { return it.classId!! }
         }
 
         return classId

core/reflection.jvm/src/kotlin/reflect/jvm/internal/util.kt

@@ -51,7 +51,7 @@ internal fun ClassDescriptor.toJavaClass(): Class<*>? {
         else -> {
             // If this is neither a Kotlin class nor a Java class, it is either a built-in or some fake class descriptor like the one
             // that's created for java.io.Serializable in JvmBuiltInsSettings
-            val classId = JavaToKotlinClassMap.INSTANCE.mapKotlinToJava(DescriptorUtils.getFqName(this)) ?: classId
+            val classId = JavaToKotlinClassMap.INSTANCE.mapKotlinToJava(DescriptorUtils.getFqName(this)) ?: classId!!
             val packageName = classId.packageFqName.asString()
             val className = classId.relativeClassName.asString()
             // All pseudo-classes like kotlin.String.Companion must be accessible from the current class loader