CORDA-2099: Define TypeIdentifier (#4081)

* Corda-2099: Define TypeIdentifier

* Comments, naming and formatting tweaks

serialization/src/test/kotlin/net/corda/serialization/internal/model/TypeIdentifierTests.kt

@@ -0,0 +1,53 @@
+package net.corda.serialization.internal.model
+
+import com.google.common.reflect.TypeToken
+import net.corda.serialization.internal.model.TypeIdentifier.*
+import org.junit.Test
+import java.lang.reflect.Type
+import kotlin.test.assertEquals
+
+class TypeIdentifierTests {
+
+    @Test
+    fun `primitive types and arrays`() {
+        assertIdentified(Int::class.javaPrimitiveType!!, "int")
+        assertIdentified<Int>("Integer")
+        assertIdentified<IntArray>("int[]")
+        assertIdentified<Array<Int>>("Integer[]")
+    }
+
+    @Test
+    fun `erased and unerased`() {
+        assertIdentified(List::class.java, "List (erased)")
+        assertIdentified<List<Int>>("List<Integer>")
+    }
+
+    @Test
+    fun `nested parameterised`() {
+        assertIdentified<List<List<Int>>>("List<List<Integer>>")
+    }
+
+    interface HasArray<T> {
+        val array: Array<out List<T>>
+    }
+
+    class HasStringArray(override val array: Array<out List<String>>): HasArray<String>
+
+    @Test
+    fun `resolved against an owning type`() {
+        val fieldType = HasArray::class.java.getDeclaredMethod("getArray").genericReturnType
+        assertIdentified(fieldType, "List<*>[]")
+
+        assertEquals(
+                "List<String>[]",
+                TypeIdentifier.forGenericType(fieldType, HasStringArray::class.java).prettyPrint())
+    }
+
+    private fun assertIdentified(type: Type, expected: String) =
+            assertEquals(expected, TypeIdentifier.forGenericType(type).prettyPrint())
+
+    private inline fun <reified T> assertIdentified(expected: String) =
+            assertEquals(expected, TypeIdentifier.forGenericType(typeOf<T>()).prettyPrint())
+
+    private inline fun <reified T> typeOf() = object : TypeToken<T>() {}.type
+}