Do not check 'no ctor parameters' for serializable enums

fixes https://github.com/Kotlin/kotlinx.serialization/issues/742

Do not use serializableIrClass if it is not bound (this may happen
in case we're generating external serializer for library class)

fixes https://github.com/Kotlin/kotlinx.serialization/issues/744

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/SerializerForEnumsGenerator.kt

@@ -39,6 +39,7 @@ class SerializerForEnumsGenerator(
         val encodeEnum = encoderClass.referenceMethod(CallingConventions.encodeEnum)
         val serialDescGetter = irGet(descriptorGetterSymbol.owner.returnType, irThis(), descriptorGetterSymbol)
 
+        val serializableIrClass = requireNotNull(serializableIrClass) { "Enums do not support external serialization" }
         val ordinalProp = serializableIrClass.properties.single { it.name == Name.identifier("ordinal") }.getter!!
         val getOrdinal = irInvoke(irGet(saveFunc.valueParameters[1]), ordinalProp.symbol)
         val call = irInvoke(irGet(saveFunc.valueParameters[0]), encodeEnum, serialDescGetter, getOrdinal)
@@ -54,6 +55,7 @@ class SerializerForEnumsGenerator(
         val decode = decoderClass.referenceMethod(CallingConventions.decodeEnum)
         val serialDescGetter = irGet(descriptorGetterSymbol.owner.returnType, irThis(), descriptorGetterSymbol)
 
+        val serializableIrClass = requireNotNull(serializableIrClass) { "Enums do not support external serialization" }
         val valuesF = serializableIrClass.functions.single { it.name == DescriptorUtils.ENUM_VALUES }
         val getValues = irInvoke(dispatchReceiver = null, callee = valuesF.symbol)
 

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/SerializerIrGenerator.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -40,7 +40,7 @@ object SERIALIZABLE_PLUGIN_ORIGIN : IrDeclarationOriginImpl("SERIALIZER")
 
 open class SerializerIrGenerator(val irClass: IrClass, final override val compilerContext: SerializationPluginContext, bindingContext: BindingContext) :
     SerializerCodegen(irClass.descriptor, bindingContext), IrBuilderExtension {
-    protected val serializableIrClass = compilerContext.symbolTable.referenceClass(serializableDescriptor).owner
+    protected val serializableIrClass = compilerContext.symbolTable.referenceClass(serializableDescriptor).takeIf { it.isBound }?.owner
 
     override fun generateSerialDesc() {
         val desc: PropertyDescriptor = generatedSerialDescPropertyDescriptor ?: return
@@ -81,7 +81,7 @@ open class SerializerIrGenerator(val irClass: IrClass, final override val compil
                         addElementsContentToDescriptor(serialDescImplClass, localDesc, addFuncS)
                         // add class annotations
                         copySerialInfoAnnotationsToDescriptor(
-                            serializableIrClass.annotations,
+                            serializableIrClass?.annotations.orEmpty(),
                             localDesc,
                             serialDescImplClass.referenceMethod(CallingConventions.addClassAnnotation)
                         )
@@ -201,7 +201,9 @@ open class SerializerIrGenerator(val irClass: IrClass, final override val compil
     override fun generateSave(function: FunctionDescriptor) = irClass.contributeFunction(function) { saveFunc ->
 
         val fieldInitializer: (SerializableProperty) -> IrExpression? =
-            buildInitializersRemapping(serializableIrClass).run { { invoke(it.irField) } }
+            buildInitializersRemapping(
+                serializableIrClass ?: error("Please provide implementation of .deserialize method for external class")
+            ).run { { invoke(it.irField) } }
 
         fun irThis(): IrExpression =
             IrGetValueImpl(startOffset, endOffset, saveFunc.dispatchReceiverParameter!!.symbol)

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/diagnostic/SerializationPluginErrorsRendering.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -38,7 +38,7 @@ object SerializationPluginErrorsRendering : DefaultErrorMessages.Extension {
         )
         MAP.put(
             SerializationErrors.PRIMARY_CONSTRUCTOR_PARAMETER_IS_NOT_A_PROPERTY,
-            "This class is not serializable automatically because it has primary constructor parameters of which are not properties"
+            "This class is not serializable automatically because it has primary constructor parameters that are not properties"
         )
         MAP.put(
             SerializationErrors.DUPLICATE_SERIAL_NAME,

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/resolve/SerializableProperties.kt

@@ -1,17 +1,6 @@
 /*
- * Copyright 2010-2017 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
 package org.jetbrains.kotlinx.serialization.compiler.resolve
@@ -67,7 +56,8 @@ class SerializableProperties(private val serializableClass: ClassDescriptor, val
                 else
                     SerializableProperties(supers, bindingContext).serializableProperties + first + second
             }
-        isExternallySerializable = primaryConstructorParameters.size == primaryConstructorProperties.size
+        isExternallySerializable =
+            serializableClass.isSerializableEnum() || primaryConstructorParameters.size == primaryConstructorProperties.size
     }
 
     val serializableConstructorProperties: List<SerializableProperty> =