Make inline foldLeftBN into foldRightBN to avoid reversed params

Author: nicolasstucki

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

@@ -112,15 +112,12 @@ object Decorators {
         else x1 :: xs1
       }
 
-    def foldRightBN[U](z: => U)(op: (T, => U) => U): U =
-      xs.reverse.foldLeftBN(z)(op)
-
-    final def foldLeftBN[U](acc: => U)(op: (T, => U) => U): U = {
-      @tailrec def fold(xs: List[T], acc: => U): U = xs match {
-        case x :: xs1 => fold(xs1, op(x, acc))
+    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
       }
-      fold(xs, acc)
+      foldLeftBN(xs.reverse, z)
     }
 
     final def hasSameLengthAs[U](ys: List[U]): Boolean = {