Make ObjectIdentifier CustomDebugStringConvertible, add test

Author: xwu

stdlib/public/core/Reflection.swift

@@ -40,9 +40,9 @@ public struct ObjectIdentifier : Hashable, Comparable {
   }
 }
 
-extension ObjectIdentifier : CustomStringConvertible {
-  /// A textual representation of `self`.
-  public var description: String {
+extension ObjectIdentifier : CustomDebugStringConvertible {
+  /// A textual representation of `self`, suitable for debugging.
+  public var debugDescription: String {
     return "ObjectIdentifier(\(_rawPointerToString(_value)))"
   }
 }

test/1_stdlib/Runtime.swift.gyb

@@ -975,6 +975,14 @@ Reflection.test("CustomMirror") {
     expectEqual(
       [ ObjectIdentifier(a), ObjectIdentifier(b), ObjectIdentifier(c) ].sorted(),
       [ ObjectIdentifier(c), ObjectIdentifier(b), ObjectIdentifier(a) ].sorted())
+
+    // CustomDebugStringConvertible
+    expectEqual(
+      String(reflecting: ObjectIdentifier(a)),
+      String(reflecting: ObjectIdentifier(a)))
+    expectNotEqual(
+      String(reflecting: ObjectIdentifier(a)),
+      String(reflecting: ObjectIdentifier(b)))
   }
 }