Support situation when argument for serializer<T>() function has SerialInfo annotations.

Because SerializationJvmIrIntrinsicSupport does not instantiate annotations yet,
this info could be lost. As a workaround, it is possible to call Companion.serializer()
functions instead of direct serializer instantiation, as they are plugin-generated
and correctly handle annotations.

Note that for some cases (enums & interfaces) this WA is not enough, so additional work
is needed later.

Fixes https://github.com/Kotlin/kotlinx.serialization/issues/2179

plugins/kotlinx-serialization/testData/boxIr/intrinsicAnnotations.kt

@@ -0,0 +1,40 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+// TARGET_BACKEND: JVM_IR
+
+// WITH_STDLIB
+
+import kotlinx.serialization.*
+import kotlinx.serialization.json.*
+import kotlinx.serialization.internal.*
+import kotlinx.serialization.descriptors.*
+import kotlinx.serialization.modules.*
+import kotlin.test.*
+
+@Serializable
+@JsonClassDiscriminator("sealed")
+sealed class Sealed
+
+@Serializable
+@JsonClassDiscriminator("abstract")
+abstract class Abstract
+
+@Serializable
+@JsonClassDiscriminator("object")
+object Object
+
+fun test(descriptor: SerialDescriptor, value: String, name: String = descriptor.serialName) {
+    val anno = descriptor.annotations.filterIsInstance<JsonClassDiscriminator>().singleOrNull()
+    requireNotNull(anno) { "Annotation value not found for $name" }
+    assertEquals(anno.discriminator, value, "Annotation value incorrect for $name")
+}
+
+fun box(): String {
+    test(serializer<Sealed>().descriptor, "sealed")
+    test(serializer<Abstract>().descriptor, "abstract")
+    test(serializer<Object>().descriptor, "object")
+    test(serializer<List<Sealed>>().descriptor.getElementDescriptor(0), "sealed", "List<Sealed>")
+    test(serializer<List<Abstract>>().descriptor.getElementDescriptor(0), "abstract", "List<Abstract>")
+    test(serializer<List<Object>>().descriptor.getElementDescriptor(0), "object", "List<Object>")
+    test(serializer<Array<Sealed>>().descriptor.getElementDescriptor(0), "sealed", "Array<Sealed>")
+    return "OK"
+}