Mitigate #2924

Author: nicolasstucki

compiler/src/dotty/tools/dotc/core/Decorators.scala

@@ -112,12 +112,11 @@ object Decorators {
         else x1 :: xs1
       }
 
-    def foldRightBN[U](z: => U)(op: (T, => U) => U): U = {
-      @tailrec def foldLeftBN(xs: List[T], acc: => U): U = xs match {
-        case x :: xs1 => foldLeftBN(xs1, op(x, acc))
-        case Nil => acc
-      }
-      foldLeftBN(xs.reverse, z)
+    def foldRightBN[U](z: => U)(op: (T, => U) => U): U = xs.reverse.foldLeftBN(z)(op)
+
+    @tailrec final def foldLeftBN[U](z: => U)(op: (T, => U) => U): U = xs match {
+      case Nil => z
+      case x :: xs1 => xs1.foldLeftBN(op(x, z))(op)
     }
 
     final def hasSameLengthAs[U](ys: List[U]): Boolean = {