Add missing opt-ins for InternalForInheritanceCoroutinesApi (#4171)

Should have no effect on the user code, just fixing the internal warnings.

integration/kotlinx-coroutines-guava/src/ListenableFuture.kt

@@ -151,6 +151,7 @@ public fun <T> ListenableFuture<T>.asDeferred(): Deferred<T> {
         cancel(false)
     }
     // Return hides the CompletableDeferred. This should prevent casting.
+    @OptIn(InternalForInheritanceCoroutinesApi::class)
     return object : Deferred<T> by deferred {}
 }
 

integration/kotlinx-coroutines-play-services/src/Tasks.kt

@@ -87,6 +87,7 @@ private fun <T> Task<T>.asDeferredImpl(cancellationTokenSource: CancellationToke
         }
     }
     // Prevent casting to CompletableDeferred and manual completion.
+    @OptIn(InternalForInheritanceCoroutinesApi::class)
     return object : Deferred<T> by deferred {}
 }
 

kotlinx-coroutines-core/common/test/AwaitTest.kt

@@ -353,6 +353,7 @@ class AwaitTest : TestBase() {
     fun testAwaitAllDelegates() = runTest {
         expect(1)
         val deferred = CompletableDeferred<String>()
+        @OptIn(InternalForInheritanceCoroutinesApi::class)
         val delegate = object : Deferred<String> by deferred {}
         launch {
             expect(3)
@@ -367,6 +368,7 @@ class AwaitTest : TestBase() {
     fun testCancelAwaitAllDelegate() = runTest {
         expect(1)
         val deferred = CompletableDeferred<String>()
+        @OptIn(InternalForInheritanceCoroutinesApi::class)
         val delegate = object : Deferred<String> by deferred {}
         launch {
             expect(3)