[Dispatch] Make comparisons with distantFuture work as expected

Author: lilyball

stdlib/public/SDK/Dispatch/Time.swift

@@ -45,7 +45,6 @@ public struct DispatchTime : Comparable {
 }
 
 public func <(a: DispatchTime, b: DispatchTime) -> Bool {
-	if a.rawValue == ~0 || b.rawValue == ~0 { return false }
 	return a.rawValue < b.rawValue
 }
 
@@ -73,7 +72,11 @@ public struct DispatchWallTime : Comparable {
 }
 
 public func <(a: DispatchWallTime, b: DispatchWallTime) -> Bool {
-	if a.rawValue == ~0 || b.rawValue == ~0 { return false }
+	if b.rawValue == ~0 {
+		return a.rawValue != ~0
+	} else if a.rawValue == ~0 {
+		return false
+	}
 	return -Int64(bitPattern: a.rawValue) < -Int64(bitPattern: b.rawValue)
 }
 

test/stdlib/Dispatch.swift

@@ -89,14 +89,14 @@ DispatchAPI.test("dispatch_data_t deallocator") {
 DispatchAPI.test("DispatchTime comparisons") {
     do {
         let now = DispatchTime.now()
-        checkComparable([now, now + .milliseconds(1)], oracle: {
+        checkComparable([now, now + .milliseconds(1), .distantFuture], oracle: {
             return $0 < $1 ? .lt : $0 == $1 ? .eq : .gt
         })
     }
 
     do {
         let now = DispatchWallTime.now()
-        checkComparable([now, now + .milliseconds(1)], oracle: {
+        checkComparable([now, now + .milliseconds(1), .distantFuture], oracle: {
             return $0 < $1 ? .lt : $0 == $1 ? .eq : .gt
         })
     }