Added test of interaction between Kotlin object singleton deserializa…

…tion and Jackson @JsonTypeInfo and @JsonIdentityInfo.

src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/GithubX.kt

@@ -0,0 +1,60 @@
+package com.fasterxml.jackson.module.kotlin.test
+
+import com.fasterxml.jackson.annotation.JsonIdentityInfo
+import com.fasterxml.jackson.annotation.JsonTypeInfo
+import com.fasterxml.jackson.annotation.ObjectIdGenerators
+import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
+import com.fasterxml.jackson.module.kotlin.jacksonTypeRef
+import com.fasterxml.jackson.module.kotlin.readValue
+import org.junit.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertSame
+
+@JsonTypeInfo(use = JsonTypeInfo.Id.MINIMAL_CLASS, include = JsonTypeInfo.As.PROPERTY, property = "@type")
+@JsonIdentityInfo(generator = ObjectIdGenerators.IntSequenceGenerator::class, property = "@id")
+interface Entity
+
+object NumberEntity : Entity
+
+data class NumberValue(val value: Int) {
+    val entity = NumberEntity
+}
+
+class TestGithubX {
+    private val json = """
+        [ {
+          "value" : 10,
+          "entity" : {
+            "@type" : ".NumberEntity",
+            "@id" : 1
+          }
+        }, {
+          "value" : 11,
+          "entity" : 1
+        } ]
+        """.trimIndent()
+
+    @Test
+    fun `test writing involving type, id and object`() {
+        val input = listOf(NumberValue(10), NumberValue(11))
+
+        val output = jacksonObjectMapper()
+            .writerFor(jacksonTypeRef<List<NumberValue>>())
+            .withDefaultPrettyPrinter()
+            .writeValueAsString(input)
+
+        assertEquals(json, output)
+    }
+
+    @Test
+    fun `test reading involving type, id and object`() {
+        val output = jacksonObjectMapper().readValue<List<NumberValue>>(json)
+
+        assertEquals(2, output.size)
+        val (a, b) = output
+        assertSame(NumberEntity::class.java, a.entity.javaClass)
+        assertSame(NumberEntity::class.java, b.entity.javaClass)
+        assertEquals(10, a.value)
+        assertEquals(11, b.value)
+    }
+}