From 742ef5864a437a86600dc2d93461d781240ede7c Mon Sep 17 00:00:00 2001
From: Corey Farwell <coreyf@rwell.org>
Date: Mon, 30 Jul 2018 09:07:51 -0400
Subject: [PATCH] Implement Iterator::size_hint for Elaborator.

---
 src/librustc/traits/util.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/librustc/traits/util.rs b/src/librustc/traits/util.rs
index 875c7199f6d11..40f13ac06f56f 100644
--- a/src/librustc/traits/util.rs
+++ b/src/librustc/traits/util.rs
@@ -239,6 +239,10 @@ impl<'cx, 'gcx, 'tcx> Elaborator<'cx, 'gcx, 'tcx> {
 impl<'cx, 'gcx, 'tcx> Iterator for Elaborator<'cx, 'gcx, 'tcx> {
     type Item = ty::Predicate<'tcx>;
 
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.stack.len(), None)
+    }
+
     fn next(&mut self) -> Option<ty::Predicate<'tcx>> {
         // Extract next item from top-most stack frame, if any.
         let next_predicate = match self.stack.pop() {