Expand type aliases in K2 when checking if serializable class' properties

have serializers.

#KT-56594 Fixed
#KT-56480 Fixed

plugins/kotlinx-serialization/testData/diagnostics/typeAliases.kt

@@ -0,0 +1,23 @@
+// FIR_IDENTICAL
+// FIR_DISABLE_LAZY_RESOLVE_CHECKS
+// WITH_STDLIB
+// SKIP_TXT
+
+import kotlinx.serialization.*
+
+typealias MyString = String
+typealias MyLong = Long
+
+@Serializable
+class Box<T>(val t: T)
+
+typealias MyBox<T> = Box<T>
+
+@Serializable
+class Foo(
+    val s: MyString,
+    val l: MyLong,
+    val b: Box<MyLong>,
+    val bb: MyBox<Long>,
+    val bbb: MyBox<MyLong>
+)

plugins/kotlinx-serialization/testData/diagnostics/typeAliasesCustomized.kt

@@ -0,0 +1,22 @@
+// FIR_IDENTICAL
+// FIR_DISABLE_LAZY_RESOLVE_CHECKS
+// WITH_STDLIB
+// SKIP_TXT
+
+import kotlinx.serialization.*
+import kotlinx.serialization.descriptors.*
+import kotlinx.serialization.encoding.*
+
+@Serializable(ExplicitSerializer::class)
+data class Klass(val s: String)
+
+object ExplicitSerializer : KSerializer<Klass> {
+    override val descriptor: SerialDescriptor get() = PrimitiveSerialDescriptor("klass", PrimitiveKind.STRING)
+    override fun serialize(encoder: Encoder, value: Klass) { encoder.encodeString(value.s) }
+    override fun deserialize(decoder: Decoder): Klass { return Klass(decoder.decodeString()) }
+}
+
+typealias KlassAlias = Klass
+
+@Serializable
+data class DataKlass(val k: KlassAlias)