Auto merge of #67136 - oli-obk:const_stability, r=Centril

Require stable/unstable annotations for the constness of all stable fns with a const modifier

r? @RalfJung @Centril

Every `#[stable]` const fn now needs either a `#[rustc_const_unstable]` attribute or a `#[rustc_const_stable]` attribute. You can't silently stabilize the constness of a function anymore.

4 files changed, 9 insertions, 2 deletions

diff --git a/src/libstd/ffi/c_str.rs b/src/libstd/ffi/c_str.rs
index 6dcda986310..14ca0423d8b 100644
--- a/src/libstd/ffi/c_str.rs
+++ b/src/libstd/ffi/c_str.rs
@@ -1065,7 +1065,8 @@ impl CStr {
     /// ```
     #[inline]
     #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
-    #[rustc_const_unstable(feature = "const_cstr_unchecked")]
+    #[cfg_attr(bootstrap, rustc_const_unstable(feature = "const_cstr_unchecked"))]
+    #[cfg_attr(not(bootstrap), rustc_const_unstable(feature = "const_cstr_unchecked", issue = "0"))]
     pub const unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
         &*(bytes as *const [u8] as *const CStr)
     }
@@ -1119,6 +1120,7 @@ impl CStr {
     /// [`CString`]: struct.CString.html
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_str_as_ptr", since = "1.32.0"))]
     pub const fn as_ptr(&self) -> *const c_char {
         self.inner.as_ptr()
     }
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 1dbb0c6ec83..8198ae73a31 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -293,7 +293,7 @@
 #![feature(raw)]
 #![feature(renamed_spin_loop)]
 #![feature(rustc_attrs)]
-#![feature(rustc_const_unstable)]
+#![cfg_attr(bootstrap, feature(rustc_const_unstable))]
 #![feature(rustc_private)]
 #![feature(shrink_to)]
 #![feature(slice_concat_ext)]
diff --git a/src/libstd/net/ip.rs b/src/libstd/net/ip.rs
index e51a9b62449..7d69f8f4b8d 100644
--- a/src/libstd/net/ip.rs
+++ b/src/libstd/net/ip.rs
@@ -319,6 +319,7 @@ impl Ipv4Addr {
     /// let addr = Ipv4Addr::new(127, 0, 0, 1);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_ipv4", since = "1.32.0"))]
     pub const fn new(a: u8, b: u8, c: u8, d: u8) -> Ipv4Addr {
         // FIXME: should just be u32::from_be_bytes([a, b, c, d]),
         // once that method is no longer rustc_const_unstable
@@ -406,6 +407,7 @@ impl Ipv4Addr {
     /// assert_eq!(Ipv4Addr::new(45, 22, 13, 197).is_unspecified(), false);
     /// ```
     #[stable(feature = "ip_shared", since = "1.12.0")]
+    #[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_ipv4", since = "1.32.0"))]
     pub const fn is_unspecified(&self) -> bool {
         self.inner.s_addr == 0
     }
@@ -1015,6 +1017,7 @@ impl Ipv6Addr {
     /// let addr = Ipv6Addr::new(0, 0, 0, 0, 0, 0xffff, 0xc00a, 0x2ff);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_ipv6", since = "1.32.0"))]
     pub const fn new(a: u16, b: u16, c: u16, d: u16, e: u16, f: u16,
                      g: u16, h: u16) -> Ipv6Addr {
         Ipv6Addr {
@@ -1480,6 +1483,7 @@ impl Ipv6Addr {
     ///            [255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
     /// ```
     #[stable(feature = "ipv6_to_octets", since = "1.12.0")]
+    #[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_ipv6", since = "1.32.0"))]
     pub const fn octets(&self) -> [u8; 16] {
         self.inner.s6_addr
     }
diff --git a/src/libstd/sync/once.rs b/src/libstd/sync/once.rs
index e8e395247f9..d8df09071cd 100644
--- a/src/libstd/sync/once.rs
+++ b/src/libstd/sync/once.rs
@@ -188,6 +188,7 @@ struct WaiterQueue<'a> {
 impl Once {
     /// Creates a new `Once` value.
     #[stable(feature = "once_new", since = "1.2.0")]
+    #[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_once_new", since = "1.32.0"))]
     pub const fn new() -> Once {
         Once { state_and_queue: AtomicUsize::new(INCOMPLETE), _marker: marker::PhantomData }
     }