From c5a9a14c9f793ce20d34cffac09f4ee21d541565 Mon Sep 17 00:00:00 2001
From: Lukas Lueg <lukas.lueg@gmail.com>
Date: Wed, 1 Jan 2020 00:25:20 +0100
Subject: [PATCH] Constify alloc::Layout

Tracking issue #67521, Layout::new in #66254
---
 src/libcore/alloc.rs | 12 ++++++++----
 src/libcore/lib.rs   |  1 +
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/libcore/alloc.rs b/src/libcore/alloc.rs
index 163f9170b8bfb..4354e1c7b5f69 100644
--- a/src/libcore/alloc.rs
+++ b/src/libcore/alloc.rs
@@ -64,8 +64,9 @@ impl Layout {
     ///    must not overflow (i.e., the rounded value must be less than
     ///    `usize::MAX`).
     #[stable(feature = "alloc_layout", since = "1.28.0")]
+    #[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
     #[inline]
-    pub fn from_size_align(size: usize, align: usize) -> Result<Self, LayoutErr> {
+    pub const fn from_size_align(size: usize, align: usize) -> Result<Self, LayoutErr> {
         if !align.is_power_of_two() {
             return Err(LayoutErr { private: () });
         }
@@ -106,15 +107,17 @@ impl Layout {
 
     /// The minimum size in bytes for a memory block of this layout.
     #[stable(feature = "alloc_layout", since = "1.28.0")]
+    #[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
     #[inline]
-    pub fn size(&self) -> usize {
+    pub const fn size(&self) -> usize {
         self.size_
     }
 
     /// The minimum byte alignment for a memory block of this layout.
     #[stable(feature = "alloc_layout", since = "1.28.0")]
+    #[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
     #[inline]
-    pub fn align(&self) -> usize {
+    pub const fn align(&self) -> usize {
         self.align_.get()
     }
 
@@ -181,8 +184,9 @@ impl Layout {
     /// address for the whole allocated block of memory. One way to
     /// satisfy this constraint is to ensure `align <= self.align()`.
     #[unstable(feature = "alloc_layout_extra", issue = "55724")]
+    #[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
     #[inline]
-    pub fn padding_needed_for(&self, align: usize) -> usize {
+    pub const fn padding_needed_for(&self, align: usize) -> usize {
         let len = self.size();
 
         // Rounded up value is:
diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index 6c4956663841c..95ffe4f438f5f 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -70,6 +70,7 @@
 #![feature(bound_cloned)]
 #![feature(cfg_target_has_atomic)]
 #![feature(concat_idents)]
+#![feature(const_alloc_layout)]
 #![feature(const_if_match)]
 #![feature(const_panic)]
 #![feature(const_fn_union)]