Tests for sealed generic serializers (#1767)

For commit JetBrains/kotlin@36484ab and issue #1646 and https://youtrack.jetbrains.com/issue/KT-49726

core/commonTest/src/kotlinx/serialization/SealedGenericClassesTest.kt

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2017-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package kotlinx.serialization
+
+import kotlinx.serialization.builtins.serializer
+import kotlinx.serialization.internal.UnitSerializer
+import kotlin.test.Test
+
+class SealedGenericClassesTest {
+    interface Output
+
+    @Serializable
+    data class Something(val s: String) : Output
+
+    @Serializable
+    sealed class Query<T : Output> {
+        @Serializable
+        data class SimpleQuery<T: Output>(val rawQuery: String) : Query<T>()
+    }
+
+    @Serializable
+    sealed class Fetcher<T : Output> {
+        abstract val query: Query<T>
+
+        @Serializable
+        data class SomethingFetcher(override val query: Query<Something>) : Fetcher<Something>()
+    }
+
+    // Test that compilation and retrieval is successful
+    @Test
+    fun testQuery() {
+        val serial1 = Query.SimpleQuery.serializer(String.serializer())
+        val serial2 = Query.serializer(UnitSerializer)
+    }
+
+    @Test
+    fun testFetcher() {
+        val serial1 = Fetcher.SomethingFetcher.serializer()
+        val serial2 = Fetcher.serializer(Something.serializer())
+    }
+}