From bb3e77d28443835d03c0148bfeb84ecad56b986d Mon Sep 17 00:00:00 2001
From: ljedrz <ljedrz@gmail.com>
Date: Mon, 29 Oct 2018 16:28:33 +0100
Subject: [PATCH] Change a flat_map with 0/1-element vecs to a filter_map

---
 src/librustc_traits/implied_outlives_bounds.rs | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/librustc_traits/implied_outlives_bounds.rs b/src/librustc_traits/implied_outlives_bounds.rs
index ad0a54e392f58..cde08f6832ace 100644
--- a/src/librustc_traits/implied_outlives_bounds.rs
+++ b/src/librustc_traits/implied_outlives_bounds.rs
@@ -159,14 +159,14 @@ fn implied_bounds_from_components(
 ) -> Vec<OutlivesBound<'tcx>> {
     sup_components
         .into_iter()
-        .flat_map(|component| {
+        .filter_map(|component| {
             match component {
                 Component::Region(r) =>
-                    vec![OutlivesBound::RegionSubRegion(sub_region, r)],
+                    Some(OutlivesBound::RegionSubRegion(sub_region, r)),
                 Component::Param(p) =>
-                    vec![OutlivesBound::RegionSubParam(sub_region, p)],
+                    Some(OutlivesBound::RegionSubParam(sub_region, p)),
                 Component::Projection(p) =>
-                    vec![OutlivesBound::RegionSubProjection(sub_region, p)],
+                    Some(OutlivesBound::RegionSubProjection(sub_region, p)),
                 Component::EscapingProjection(_) =>
                 // If the projection has escaping regions, don't
                 // try to infer any implied bounds even for its
@@ -176,9 +176,9 @@ fn implied_bounds_from_components(
                 // idea is that the WAY that the caller proves
                 // that may change in the future and we want to
                 // give ourselves room to get smarter here.
-                    vec![],
+                    None,
                 Component::UnresolvedInferenceVariable(..) =>
-                    vec![],
+                    None,
             }
         })
         .collect()