From 959dd53ec60e2aef4ce97707a07dbe732ea7f4f4 Mon Sep 17 00:00:00 2001
From: Nathaniel McCallum <npmccallum@redhat.com>
Date: Fri, 21 Sep 2018 12:42:40 -0400
Subject: [PATCH 1/2] Implement BitAnd-based truncation for integers

There are a variety of circumstances where a function wants to take n
low bits from a generic input type. These implementations support that
workflow.

Closes #54435
---
 src/libcore/ops/bit.rs | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/src/libcore/ops/bit.rs b/src/libcore/ops/bit.rs
index 3900f365b0ab1..b1fee5e8476eb 100644
--- a/src/libcore/ops/bit.rs
+++ b/src/libcore/ops/bit.rs
@@ -151,6 +151,44 @@ macro_rules! bitand_impl {
 
 bitand_impl! { bool usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 }
 
+macro_rules! bitand_trunc_impl {
+    ($($t:ty:$u:ty)*) => ($(
+        #[unstable(feature = "bitand_trunc", issue = "000000")]
+        impl BitAnd<$u> for $t {
+            type Output = $u;
+
+            #[inline]
+            fn bitand(self, rhs: $u) -> $u { self as $u & rhs }
+        }
+
+        forward_ref_binop! { impl BitAnd, bitand for $t, $u }
+    )*)
+}
+
+bitand_trunc_impl! {
+    u128:u64
+    u128:u32
+    u128:u16
+    u128:u8
+    u64:u32
+    u64:u16
+    u64:u8
+    u32:u16
+    u32:u8
+    u16:u8
+
+    i128:i64
+    i128:i32
+    i128:i16
+    i128:i8
+    i64:i32
+    i64:i16
+    i64:i8
+    i32:i16
+    i32:i8
+    i16:i8
+}
+
 /// The bitwise OR operator `|`.
 ///
 /// Note that `RHS` is `Self` by default, but this is not mandatory.

From 5ceea26e87faa35bd631011f251a5d5757625d92 Mon Sep 17 00:00:00 2001
From: Nathaniel McCallum <npmccallum@redhat.com>
Date: Fri, 21 Sep 2018 13:04:59 -0400
Subject: [PATCH 2/2] Add BitAnd-truncation to usize and isize

---
 src/libcore/ops/bit.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/libcore/ops/bit.rs b/src/libcore/ops/bit.rs
index b1fee5e8476eb..08c2d45dba617 100644
--- a/src/libcore/ops/bit.rs
+++ b/src/libcore/ops/bit.rs
@@ -166,6 +166,9 @@ macro_rules! bitand_trunc_impl {
 }
 
 bitand_trunc_impl! {
+    usize:u32
+    usize:u16
+    usize:u8
     u128:u64
     u128:u32
     u128:u16
@@ -177,6 +180,9 @@ bitand_trunc_impl! {
     u32:u8
     u16:u8
 
+    isize:i32
+    isize:i16
+    isize:i8
     i128:i64
     i128:i32
     i128:i16