From a12788a0d77f1ad906bc1d51c4684dd8723278e0 Mon Sep 17 00:00:00 2001
From: Trevor Spiteri <tspiteri@ieee.org>
Date: Thu, 22 Aug 2019 19:57:48 +0200
Subject: [PATCH] make is_power_of_two a const function

---
 src/libcore/num/mod.rs                    |  4 ++--
 src/test/ui/consts/const-int-pow-rpass.rs | 11 +++++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)
 create mode 100644 src/test/ui/consts/const-int-pow-rpass.rs

diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index ebde82de834..82c1943b7d0 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -3749,8 +3749,8 @@ assert!(!10", stringify!($SelfT), ".is_power_of_two());", $EndFeature, "
 ```"),
             #[stable(feature = "rust1", since = "1.0.0")]
             #[inline]
-            pub fn is_power_of_two(self) -> bool {
-                (self.wrapping_sub(1)) & self == 0 && !(self == 0)
+            pub const fn is_power_of_two(self) -> bool {
+                ((self.wrapping_sub(1)) & self == 0) & !(self == 0)
             }
         }
 
diff --git a/src/test/ui/consts/const-int-pow-rpass.rs b/src/test/ui/consts/const-int-pow-rpass.rs
new file mode 100644
index 00000000000..8e84a900605
--- /dev/null
+++ b/src/test/ui/consts/const-int-pow-rpass.rs
@@ -0,0 +1,11 @@
+// run-pass
+
+const IS_POWER_OF_TWO_A: bool = 0u32.is_power_of_two();
+const IS_POWER_OF_TWO_B: bool = 32u32.is_power_of_two();
+const IS_POWER_OF_TWO_C: bool = 33u32.is_power_of_two();
+
+fn main() {
+    assert!(!IS_POWER_OF_TWO_A);
+    assert!(IS_POWER_OF_TWO_B);
+    assert!(!IS_POWER_OF_TWO_C);
+}