From 2430870a2194bb16e867bf2d15ea45827e6d4f7e Mon Sep 17 00:00:00 2001
From: Andre Bogus <bogusandre@gmail.com>
Date: Wed, 19 Dec 2018 02:43:58 +0100
Subject: [PATCH] Make `SortedMap::new` const, also faster `is_empty`.

---
 src/librustc_data_structures/lib.rs        | 2 ++
 src/librustc_data_structures/sorted_map.rs | 6 +++---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/librustc_data_structures/lib.rs b/src/librustc_data_structures/lib.rs
index 8e0ecb70c6896..4187d7721c137 100644
--- a/src/librustc_data_structures/lib.rs
+++ b/src/librustc_data_structures/lib.rs
@@ -30,6 +30,8 @@
 #![feature(allow_internal_unstable)]
 #![feature(vec_resize_with)]
 #![feature(hash_raw_entry)]
+#![feature(const_fn)]
+#![feature(const_vec_new)]
 
 #![cfg_attr(unix, feature(libc))]
 #![cfg_attr(test, feature(test))]
diff --git a/src/librustc_data_structures/sorted_map.rs b/src/librustc_data_structures/sorted_map.rs
index 3bd3d11660797..edd7e9c3d7bd0 100644
--- a/src/librustc_data_structures/sorted_map.rs
+++ b/src/librustc_data_structures/sorted_map.rs
@@ -30,9 +30,9 @@ pub struct SortedMap<K: Ord, V> {
 
 impl<K: Ord, V> SortedMap<K, V> {
     #[inline]
-    pub fn new() -> SortedMap<K, V> {
+    pub const fn new() -> SortedMap<K, V> {
         SortedMap {
-            data: vec![]
+            data: Vec::new()
         }
     }
 
@@ -144,7 +144,7 @@ impl<K: Ord, V> SortedMap<K, V> {
 
     #[inline]
     pub fn is_empty(&self) -> bool {
-        self.len() == 0
+        self.data.is_empty()
     }
 
     #[inline]