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.

src/liballoc/collections/linked_list.rs

@@ -275,6 +275,10 @@ impl<T> LinkedList<T> {
     /// let list: LinkedList<u32> = LinkedList::new();
     /// ```
     #[inline]
+    #[cfg_attr(
+        not(bootstrap),
+        rustc_const_stable(feature = "const_linked_list_new", since = "1.32.0"),
+    )]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub const fn new() -> Self {
         LinkedList {

src/liballoc/lib.rs

@@ -117,7 +117,7 @@
 #![feature(unsized_locals)]
 #![feature(allocator_internals)]
 #![cfg_attr(bootstrap, feature(on_unimplemented))]
-#![feature(rustc_const_unstable)]
+#![cfg_attr(bootstrap, feature(rustc_const_unstable))]
 #![feature(slice_partition_dedup)]
 #![feature(maybe_uninit_extra, maybe_uninit_slice)]
 #![feature(alloc_layout_extra)]

src/liballoc/string.rs

@@ -367,6 +367,10 @@ impl String {
     /// let s = String::new();
     /// ```
     #[inline]
+    #[cfg_attr(
+        not(bootstrap),
+        rustc_const_stable(feature = "const_string_new", since = "1.32.0"),
+    )]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub const fn new() -> String {
         String { vec: Vec::new() }

src/liballoc/vec.rs

@@ -315,6 +315,10 @@ impl<T> Vec<T> {
     /// let mut vec: Vec<i32> = Vec::new();
     /// ```
     #[inline]
+    #[cfg_attr(
+        not(bootstrap),
+        rustc_const_stable(feature = "const_vec_new", since = "1.32.0"),
+    )]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub const fn new() -> Vec<T> {
         Vec {

src/libcore/alloc.rs

@@ -100,6 +100,7 @@ impl Layout {
     /// This function is unsafe as it does not verify the preconditions from
     /// [`Layout::from_size_align`](#method.from_size_align).
     #[stable(feature = "alloc_layout", since = "1.28.0")]
+    #[cfg_attr(not(bootstrap), rustc_const_stable(feature = "alloc_layout", since = "1.28.0"))]
     #[inline]
     pub const unsafe fn from_size_align_unchecked(size: usize, align: usize) -> Self {
         Layout { size_: size, align_: NonZeroUsize::new_unchecked(align) }

src/libcore/any.rs

@@ -423,7 +423,8 @@ impl TypeId {
     /// assert_eq!(is_string(&"cookie monster".to_string()), true);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature="const_type_id")]
+    #[cfg_attr(bootstrap, rustc_const_unstable(feature="const_type_id"))]
+    #[cfg_attr(not(bootstrap), rustc_const_unstable(feature="const_type_id", issue = "41875"))]
     pub const fn of<T: ?Sized + 'static>() -> TypeId {
         TypeId {
             #[cfg(bootstrap)]
@@ -461,7 +462,8 @@ impl TypeId {
 /// );
 /// ```
 #[stable(feature = "type_name", since = "1.38.0")]
-#[rustc_const_unstable(feature = "const_type_name")]
+#[cfg_attr(bootstrap, rustc_const_unstable(feature = "const_type_name"))]
+#[cfg_attr(not(bootstrap), rustc_const_unstable(feature = "const_type_name", issue = "63084"))]
 pub const fn type_name<T: ?Sized>() -> &'static str {
     intrinsics::type_name::<T>()
 }
@@ -499,7 +501,8 @@ pub const fn type_name<T: ?Sized>() -> &'static str {
 /// println!("{}", type_name_of_val(&y));
 /// ```
 #[unstable(feature = "type_name_of_val", issue = "66359")]
-#[rustc_const_unstable(feature = "const_type_name")]
+#[cfg_attr(bootstrap, rustc_const_unstable(feature = "const_type_name"))]
+#[cfg_attr(not(bootstrap), rustc_const_unstable(feature = "const_type_name", issue = "63084"))]
 pub const fn type_name_of_val<T: ?Sized>(val: &T) -> &'static str {
     let _ = val;
     type_name::<T>()

src/libcore/cell.rs

@@ -324,6 +324,7 @@ impl<T> Cell<T> {
     /// let c = Cell::new(5);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_cell_new", since = "1.32.0"))]
     #[inline]
     pub const fn new(value: T) -> Cell<T> {
         Cell {
@@ -469,6 +470,7 @@ impl<T: ?Sized> Cell<T> {
     /// ```
     #[inline]
     #[stable(feature = "cell_as_ptr", since = "1.12.0")]
+    #[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_cell_as_ptr", since = "1.32.0"))]
     pub const fn as_ptr(&self) -> *mut T {
         self.value.get()
     }
@@ -649,6 +651,7 @@ impl<T> RefCell<T> {
     /// let c = RefCell::new(5);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_refcell_new", since = "1.32.0"))]
     #[inline]
     pub const fn new(value: T) -> RefCell<T> {
         RefCell {
@@ -1501,6 +1504,10 @@ impl<T> UnsafeCell<T> {
     /// let uc = UnsafeCell::new(5);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(
+        not(bootstrap),
+        rustc_const_stable(feature = "const_unsafe_cell_new", since = "1.32.0"),
+    )]
     #[inline]
     pub const fn new(value: T) -> UnsafeCell<T> {
         UnsafeCell { value }
@@ -1543,6 +1550,10 @@ impl<T: ?Sized> UnsafeCell<T> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(
+        not(bootstrap),
+        rustc_const_stable(feature = "const_unsafecell_get", since = "1.32.0"),
+    )]
     pub const fn get(&self) -> *mut T {
         // We can just cast the pointer from `UnsafeCell<T>` to `T` because of
         // #[repr(transparent)]. This exploits libstd's special status, there is

src/libcore/char/methods.rs

@@ -911,6 +911,10 @@ impl char {
     /// assert!(!non_ascii.is_ascii());
     /// ```
     #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
+    #[cfg_attr(
+        not(bootstrap),
+        rustc_const_stable(feature = "const_ascii_methods_on_intrinsics", since = "1.32.0"),
+    )]
     #[inline]
     pub const fn is_ascii(&self) -> bool {
         *self as u32 <= 0x7F

src/libcore/convert/mod.rs

@@ -99,6 +99,7 @@ pub use num::FloatToInt;
 /// assert_eq!(vec![1, 3], filtered);
 /// ```
 #[stable(feature = "convert_id", since = "1.33.0")]
+#[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_identity", since = "1.33.0"))]
 #[inline]
 pub const fn identity<T>(x: T) -> T {
     x

src/libcore/intrinsics.rs

@@ -939,7 +939,11 @@ extern "rust-intrinsic" {
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_transmute")]
+    #[cfg_attr(bootstrap, rustc_const_unstable(feature = "const_transmute"))]
+    #[cfg_attr(
+        not(bootstrap),
+        rustc_const_unstable(feature = "const_transmute", issue = "53605"),
+    )]
     pub fn transmute<T, U>(e: T) -> U;
 
     /// Returns `true` if the actual type given as `T` requires drop

src/libcore/iter/sources.rs

@@ -281,6 +281,7 @@ impl<T> Default for Empty<T> {
 /// assert_eq!(None, nope.next());
 /// ```
 #[stable(feature = "iter_empty", since = "1.2.0")]
+#[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_iter_empty", since = "1.32.0"))]
 pub const fn empty<T>() -> Empty<T> {
     Empty(marker::PhantomData)
 }

src/libcore/lib.rs

@@ -96,7 +96,7 @@
 #![feature(prelude_import)]
 #![feature(repr_simd, platform_intrinsics)]
 #![feature(rustc_attrs)]
-#![feature(rustc_const_unstable)]
+#![cfg_attr(bootstrap, feature(rustc_const_unstable))]
 #![feature(simd_ffi)]
 #![feature(specialization)]
 #![feature(staged_api)]

src/libcore/mem/manually_drop.rs

@@ -63,6 +63,10 @@ impl<T> ManuallyDrop<T> {
     /// ManuallyDrop::new(Box::new(()));
     /// ```
     #[stable(feature = "manually_drop", since = "1.20.0")]
+    #[cfg_attr(
+        not(bootstrap),
+        rustc_const_stable(feature = "const_manually_drop", since = "1.36.0"),
+    )]
     #[inline(always)]
     pub const fn new(value: T) -> ManuallyDrop<T> {
         ManuallyDrop { value }
@@ -80,6 +84,10 @@ impl<T> ManuallyDrop<T> {
     /// let _: Box<()> = ManuallyDrop::into_inner(x); // This drops the `Box`.
     /// ```
     #[stable(feature = "manually_drop", since = "1.20.0")]
+    #[cfg_attr(
+        not(bootstrap),
+        rustc_const_stable(feature = "const_manually_drop", since = "1.36.0"),
+    )]
     #[inline(always)]
     pub const fn into_inner(slot: ManuallyDrop<T>) -> T {
         slot.value

src/libcore/mem/maybe_uninit.rs

@@ -250,6 +250,10 @@ impl<T> MaybeUninit<T> {
     ///
     /// [`assume_init`]: #method.assume_init
     #[stable(feature = "maybe_uninit", since = "1.36.0")]
+    #[cfg_attr(
+        not(bootstrap),
+        rustc_const_stable(feature = "const_maybe_uninit", since = "1.36.0"),
+    )]
     #[inline(always)]
     pub const fn new(val: T) -> MaybeUninit<T> {
         MaybeUninit { value: ManuallyDrop::new(val) }
@@ -264,6 +268,10 @@ impl<T> MaybeUninit<T> {
     ///
     /// [type]: union.MaybeUninit.html
     #[stable(feature = "maybe_uninit", since = "1.36.0")]
+    #[cfg_attr(
+        not(bootstrap),
+        rustc_const_stable(feature = "const_maybe_uninit", since = "1.36.0"),
+    )]
     #[inline(always)]
     #[cfg_attr(all(not(bootstrap)), rustc_diagnostic_item = "maybe_uninit_uninit")]
     pub const fn uninit() -> MaybeUninit<T> {

src/libcore/mem/mod.rs

@@ -271,6 +271,7 @@ pub fn forget_unsized<T: ?Sized>(t: T) {
 #[inline(always)]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_promotable]
+#[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_size_of", since = "1.32.0"))]
 pub const fn size_of<T>() -> usize {
     intrinsics::size_of::<T>()
 }
@@ -371,6 +372,7 @@ pub fn min_align_of_val<T: ?Sized>(val: &T) -> usize {
 #[inline(always)]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_promotable]
+#[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_align_of", since = "1.32.0"))]
 pub const fn align_of<T>() -> usize {
     intrinsics::min_align_of::<T>()
 }
@@ -453,6 +455,7 @@ pub fn align_of_val<T: ?Sized>(val: &T) -> usize {
 /// ```
 #[inline]
 #[stable(feature = "needs_drop", since = "1.21.0")]
+#[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_needs_drop", since = "1.36.0"))]
 pub const fn needs_drop<T>() -> bool {
     intrinsics::needs_drop::<T>()
 }