JVM_IR: Serialization: do not mess with return types of call expressions

If return type of IrConstructor is different from containing class, we will
generate call to wrong <init> method, leading to VerifyError.
If we do not specify the type of irNull, it, by default, will be Nothing?,
when really we need Any?. This leads to CCE: cannot cast to Void at runtime.

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

@@ -499,7 +499,8 @@ interface IrBuilderExtension {
                 null, compilerContext.symbolTable.referenceConstructor(nullableSerializerClass.descriptor.constructors.toList().first()),
                 typeArguments = listOf(type.makeNotNullable().toIrType()),
                 valueArguments = listOf(expression),
-                returnTypeHint = wrapIrTypeIntoKSerializerIrType(module, type.toIrType())
+                // Return type should not be different from declared class, otherwise, we will call wrong <init> method on runtime.
+                returnTypeHint = null
             )
         else
             expression
@@ -656,8 +657,8 @@ interface IrBuilderExtension {
             } else {
                 compilerContext.symbolTable.referenceConstructor(serializerClass.unsubstitutedPrimaryConstructor!!)
             }
-            val returnType = wrapIrTypeIntoKSerializerIrType(module, thisIrType)
-            return irInvoke(null, ctor, typeArguments = typeArgs, valueArguments = args, returnTypeHint = returnType)
+            // Return type should not be different from declared class, otherwise, we will call wrong <init> method on runtime.
+            return irInvoke(null, ctor, typeArguments = typeArgs, valueArguments = args, returnTypeHint = null)
         }
     }
 

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

@@ -311,7 +311,7 @@ open class SerializerIrGenerator(val irClass: IrClass, final override val compil
             else -> null
         }
         return if (defaultPrimitive == null)
-            irNull() to (compilerContext.builtIns.nullableAnyType)
+            irNull(compilerContext.irBuiltIns.anyNType) to (compilerContext.builtIns.nullableAnyType)
         else
             defaultPrimitive to kType
     }