From a145b80be079fd6b299270f7fb97ed5ce0452d32 Mon Sep 17 00:00:00 2001
From: Lukas Lueg <lukas.lueg@gmail.com>
Date: Sat, 28 Dec 2019 21:33:36 +0100
Subject: [PATCH] Constify Result

---
 src/libcore/lib.rs    | 2 ++
 src/libcore/result.rs | 9 ++++++---
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index 7d11dd2800fd4..80310ebee7bce 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -72,8 +72,10 @@
 #![feature(concat_idents)]
 #![feature(const_fn)]
 #![feature(const_fn_union)]
+#![feature(const_if_match)]
 #![feature(const_generics)]
 #![feature(const_ptr_offset_from)]
+#![feature(const_result)]
 #![feature(const_type_name)]
 #![feature(custom_inner_attributes)]
 #![feature(decl_macro)]
diff --git a/src/libcore/result.rs b/src/libcore/result.rs
index ce4c8995a3c48..8e62a3e8f71f0 100644
--- a/src/libcore/result.rs
+++ b/src/libcore/result.rs
@@ -278,9 +278,10 @@ impl<T, E> Result<T, E> {
     /// assert_eq!(x.is_ok(), false);
     /// ```
     #[must_use = "if you intended to assert that this is ok, consider `.unwrap()` instead"]
+    #[rustc_const_unstable(feature = "const_result", issue = "67520")]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn is_ok(&self) -> bool {
+    pub const fn is_ok(&self) -> bool {
         match *self {
             Ok(_) => true,
             Err(_) => false,
@@ -303,9 +304,10 @@ impl<T, E> Result<T, E> {
     /// assert_eq!(x.is_err(), true);
     /// ```
     #[must_use = "if you intended to assert that this is err, consider `.unwrap_err()` instead"]
+    #[rustc_const_unstable(feature = "const_result", issue = "67520")]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn is_err(&self) -> bool {
+    pub const fn is_err(&self) -> bool {
         !self.is_ok()
     }
 
@@ -446,8 +448,9 @@ impl<T, E> Result<T, E> {
     /// assert_eq!(x.as_ref(), Err(&"Error"));
     /// ```
     #[inline]
+    #[rustc_const_unstable(feature = "const_result", issue = "67520")]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn as_ref(&self) -> Result<&T, &E> {
+    pub const fn as_ref(&self) -> Result<&T, &E> {
         match *self {
             Ok(ref x) => Ok(x),
             Err(ref x) => Err(x),