1 files changed, 18 insertions, 0 deletions
diff --git a/main/core/src/util/EitherOps.scala b/main/core/src/util/EitherOps.scala
new file mode 100644
index 00000000..da2552c8
--- /dev/null
+++ b/main/core/src/util/EitherOps.scala
@@ -0,0 +1,18 @@
+package mill.util
+
+import scala.collection.generic.CanBuildFrom
+import scala.collection.mutable
+import scala.language.higherKinds
+
+object EitherOps {
+
+  // implementation similar to scala.concurrent.Future#sequence
+  def sequence[A, B, M[X] <: TraversableOnce[X]](in: M[Either[A, B]])(
+      implicit cbf: CanBuildFrom[M[Either[A, B]], B, M[B]]): Either[A, M[B]] = {
+    in.foldLeft[Either[A, mutable.Builder[B, M[B]]]](Right(cbf(in))) {
+        case (acc, el) =>
+          for (a <- acc; e <- el) yield a += e
+      }
+      .map(_.result())
+  }
+}