From 7767e7fb165d527f1991175809a361f2d2313b80 Mon Sep 17 00:00:00 2001
From: Oliver Scherer <github35764891676564198441@oli-obk.de>
Date: Wed, 21 Aug 2019 02:23:46 +0200
Subject: Stabilize `str::len`, `[T]::len`, `is_empty` and `str::as_bytes` as
 const fn

---
 src/libcore/lib.rs       | 6 +++---
 src/libcore/slice/mod.rs | 6 ++++--
 src/libcore/str/mod.rs   | 8 +++++---
 3 files changed, 12 insertions(+), 8 deletions(-)

(limited to 'src/libcore')

diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index 5c681b3a5d8..8221df56a51 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -120,9 +120,9 @@
 #![feature(rtm_target_feature)]
 #![feature(f16c_target_feature)]
 #![feature(hexagon_target_feature)]
-#![feature(const_slice_len)]
-#![feature(const_str_as_bytes)]
-#![feature(const_str_len)]
+#![cfg_attr(bootstrap, feature(const_slice_len))]
+#![cfg_attr(bootstrap, feature(const_str_as_bytes))]
+#![cfg_attr(bootstrap, feature(const_str_len))]
 #![feature(const_int_conversion)]
 #![feature(const_transmute)]
 #![feature(non_exhaustive)]
diff --git a/src/libcore/slice/mod.rs b/src/libcore/slice/mod.rs
index 931768564ca..0c2a4e08672 100644
--- a/src/libcore/slice/mod.rs
+++ b/src/libcore/slice/mod.rs
@@ -62,7 +62,9 @@ impl<T> [T] {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
-    #[rustc_const_unstable(feature = "const_slice_len")]
+    #[cfg_attr(bootstrap, rustc_const_unstable(feature = "const_slice_len"))]
+    // SAFETY: const sound because we transmute out the length field as a usize (which it must be)
+    #[cfg_attr(not(bootstrap), allow_internal_unstable(const_fn_union))]
     pub const fn len(&self) -> usize {
         unsafe {
             crate::ptr::Repr { rust: self }.raw.len
@@ -79,7 +81,7 @@ impl<T> [T] {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
-    #[rustc_const_unstable(feature = "const_slice_len")]
+    #[cfg_attr(bootstrap, rustc_const_unstable(feature = "const_slice_len"))]
     pub const fn is_empty(&self) -> bool {
         self.len() == 0
     }
diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index 5e5b5593fd8..a6ec757faf1 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -2090,7 +2090,7 @@ impl str {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
-    #[rustc_const_unstable(feature = "const_str_len")]
+    #[cfg_attr(bootstrap, rustc_const_unstable(feature = "const_str_len"))]
     pub const fn len(&self) -> usize {
         self.as_bytes().len()
     }
@@ -2110,7 +2110,7 @@ impl str {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_str_len")]
+    #[cfg_attr(bootstrap, rustc_const_unstable(feature = "const_str_len"))]
     pub const fn is_empty(&self) -> bool {
         self.len() == 0
     }
@@ -2168,7 +2168,9 @@ impl str {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline(always)]
-    #[rustc_const_unstable(feature="const_str_as_bytes")]
+    #[cfg_attr(bootstrap, rustc_const_unstable(feature = "const_str_as_bytes"))]
+    // SAFETY: const sound because we transmute two types with the same layout
+    #[cfg_attr(not(bootstrap), allow_internal_unstable(const_fn_union))]
     pub const fn as_bytes(&self) -> &[u8] {
         #[repr(C)]
         union Slices<'a> {
-- 
cgit 1.4.1-3-g733a5