twitter
diff --git a/‎CHANGES‎
Lines changed: 5 additions & 0 deletions b/‎CHANGES‎
Lines changed: 5 additions & 0 deletions
diff --git a/‎util-app/src/main/scala/com/twitter/app/Flag.scala‎
Lines changed: 3 additions & 3 deletions b/‎util-app/src/main/scala/com/twitter/app/Flag.scala‎
Lines changed: 3 additions & 3 deletions
diff --git a/‎util-app/src/test/scala/com/twitter/app/FlagTest.scala‎
Lines changed: 20 additions & 3 deletions b/‎util-app/src/test/scala/com/twitter/app/FlagTest.scala‎
Lines changed: 20 additions & 3 deletions
@@ -6,6 +6,11 @@ Note that ``PHAB_ID=#`` and ``RB_ID=#`` correspond to associated messages in com
 
 Next Version
 
+API Changes:
+
+  * util-app: c.t.app.Flag.let and letClear are now generic in their return type.
+    ``PHAB_ID=D93951``
+
 Runtime Behavior Changes:
 
   * util-security: Assert validity of X.509 certificates when read from a file.
 
@@ -149,7 +149,7 @@ class Flag[T: Flaggable] private[app] (
    *
    * @see [[letClear]]
    */
-  def let(t: T)(f: => Unit): Unit =
+  def let[R](t: T)(f: => R): R =
     let(Some(t), f)
 
   /**
@@ -159,10 +159,10 @@ class Flag[T: Flaggable] private[app] (
    *
    * @see [[let]]
    */
-  def letClear(f: => Unit): Unit =
+  def letClear[R](f: => R): R =
     let(None, f)
 
-  private[this] def let(t: Option[T], f: => Unit): Unit = {
+  private[this] def let[R](t: Option[T], f: => R): R = {
     val prev = localValue
     setLocalValue(t)
     try f
 
@@ -1,11 +1,8 @@
 package com.twitter.app
 
-import org.junit.runner.RunWith
 import org.scalatest.FunSuite
-import org.scalatest.junit.JUnitRunner
 import scala.collection.mutable.Buffer
 
-@RunWith(classOf[JUnitRunner])
 class FlagTest extends FunSuite {
 
   class Ctx(failFastUntilParsed: Boolean = false) {
@@ -77,6 +74,15 @@ class FlagTest extends FunSuite {
     assert(buf == Seq(1, 2, 3))
   }
 
+  test("Flag: let return values reflect bindings") {
+    def current: Boolean = MyGlobalBooleanFlag()
+
+    val res1 = MyGlobalBooleanFlag.let(true) { current.toString }
+    assert(res1 == "true")
+    val res2 = MyGlobalBooleanFlag.let(false) { current.toString }
+    assert(res2 == "false")
+  }
+
   test("Flag: letClear") {
     // track the order the blocks execute and that they only execute once
     var buf = Buffer[Int]()
@@ -95,6 +101,17 @@ class FlagTest extends FunSuite {
     assert(buf == Seq(1, 2, 3))
   }
 
+  test("Flag: letClear return values reflect bindings") {
+    def current: Boolean = MyGlobalBooleanFlag()
+
+    MyGlobalBooleanFlag.let(true) {
+      val res1 = current
+      val res2 = MyGlobalBooleanFlag.letClear { current }
+      assert(res1)
+      assert(!res2)
+    }
+  }
+
   class Dctx extends Ctx {
     val quuxFlag = flag[Int]("quux", "an int")
   }