From 8f3021bd2cc49eda82ae01ac2e769a7e0fd0aa36 Mon Sep 17 00:00:00 2001
From: Dylan MacKenzie <ecstaticmorse@gmail.com>
Date: Tue, 10 Dec 2019 12:41:27 -0800
Subject: [PATCH] Get active features dynamically by their `Symbol`

---
 src/librustc_feature/active.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/librustc_feature/active.rs b/src/librustc_feature/active.rs
index 363621b3ca4..8794d830961 100644
--- a/src/librustc_feature/active.rs
+++ b/src/librustc_feature/active.rs
@@ -53,6 +53,18 @@ macro_rules! declare_features {
                 $(f(stringify!($feature), self.$feature);)+
             }
         }
+
+        impl std::ops::Index<Symbol> for Features {
+            type Output = bool;
+
+            fn index(&self, feature: Symbol) -> &Self::Output {
+                match feature {
+                    $( sym::$feature => &self.$feature, )*
+
+                    _ => panic!("{} was not defined in `declare_features`", feature),
+                }
+            }
+        }
     };
 }