Constify conversion traits

44 files changed, 278 insertions, 171 deletions

diff --git a/library/alloc/src/borrow.rs b/library/alloc/src/borrow.rs
index 07f51b7614f..cb32896161e 100644
--- a/library/alloc/src/borrow.rs
+++ b/library/alloc/src/borrow.rs
@@ -17,9 +17,11 @@ use crate::fmt;
 use crate::string::String;
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, B: ?Sized> Borrow<B> for Cow<'a, B>
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<'a, B: ?Sized> const Borrow<B> for Cow<'a, B>
 where
     B: ToOwned,
+    B::Owned: [const] Borrow<B>,
 {
     fn borrow(&self) -> &B {
         &**self
@@ -326,9 +328,10 @@ impl<B: ?Sized + ToOwned> Cow<'_, B> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<B: ?Sized + ToOwned> Deref for Cow<'_, B>
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<B: ?Sized + ToOwned> const Deref for Cow<'_, B>
 where
-    B::Owned: Borrow<B>,
+    B::Owned: [const] Borrow<B>,
 {
     type Target = B;
 
@@ -439,7 +442,11 @@ where
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized + ToOwned> AsRef<T> for Cow<'_, T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T: ?Sized + ToOwned> const AsRef<T> for Cow<'_, T>
+where
+    T::Owned: [const] Borrow<T>,
+{
     fn as_ref(&self) -> &T {
         self
     }
diff --git a/library/alloc/src/collections/mod.rs b/library/alloc/src/collections/mod.rs
index fac4d1a65ab..212d7c8465b 100644
--- a/library/alloc/src/collections/mod.rs
+++ b/library/alloc/src/collections/mod.rs
@@ -128,8 +128,9 @@ pub use realalloc::collections::TryReserveErrorKind;
     reason = "Uncertain how much info should be exposed",
     issue = "48043"
 )]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 #[cfg(not(test))]
-impl From<TryReserveErrorKind> for TryReserveError {
+impl const From<TryReserveErrorKind> for TryReserveError {
     #[inline]
     fn from(kind: TryReserveErrorKind) -> Self {
         Self { kind }
@@ -137,8 +138,9 @@ impl From<TryReserveErrorKind> for TryReserveError {
 }
 
 #[unstable(feature = "try_reserve_kind", reason = "new API", issue = "48043")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 #[cfg(not(test))]
-impl From<LayoutError> for TryReserveErrorKind {
+impl const From<LayoutError> for TryReserveErrorKind {
     /// Always evaluates to [`TryReserveErrorKind::CapacityOverflow`].
     #[inline]
     fn from(_: LayoutError) -> Self {
diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index 711092ae8eb..cba1ce40f75 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -107,10 +107,10 @@
 #![feature(char_max_len)]
 #![feature(clone_to_uninit)]
 #![feature(coerce_unsized)]
+#![feature(const_convert)]
 #![feature(const_default)]
 #![feature(const_eval_select)]
 #![feature(const_heap)]
-#![feature(const_trait_impl)]
 #![feature(core_intrinsics)]
 #![feature(deprecated_suggestion)]
 #![feature(deref_pure_trait)]
@@ -168,6 +168,7 @@
 #![feature(allow_internal_unstable)]
 #![feature(cfg_sanitize)]
 #![feature(const_precise_live_drops)]
+#![feature(const_trait_impl)]
 #![feature(coroutine_trait)]
 #![feature(decl_macro)]
 #![feature(dropck_eyepatch)]
diff --git a/library/alloctests/lib.rs b/library/alloctests/lib.rs
index 97de7d6a701..0201c875221 100644
--- a/library/alloctests/lib.rs
+++ b/library/alloctests/lib.rs
@@ -49,6 +49,7 @@
 // Language features:
 // tidy-alphabetical-start
 #![feature(cfg_sanitize)]
+#![feature(const_trait_impl)]
 #![feature(dropck_eyepatch)]
 #![feature(lang_items)]
 #![feature(min_specialization)]
diff --git a/library/core/src/array/mod.rs b/library/core/src/array/mod.rs
index 835ee57ce23..915198e571f 100644
--- a/library/core/src/array/mod.rs
+++ b/library/core/src/array/mod.rs
@@ -192,7 +192,7 @@ impl fmt::Display for TryFromSliceError {
 impl Error for TryFromSliceError {}
 
 #[stable(feature = "try_from_slice_error", since = "1.36.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<Infallible> for TryFromSliceError {
     fn from(x: Infallible) -> TryFromSliceError {
         match x {}
@@ -200,7 +200,8 @@ impl const From<Infallible> for TryFromSliceError {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T, const N: usize> AsRef<[T]> for [T; N] {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T, const N: usize> const AsRef<[T]> for [T; N] {
     #[inline]
     fn as_ref(&self) -> &[T] {
         &self[..]
@@ -208,7 +209,8 @@ impl<T, const N: usize> AsRef<[T]> for [T; N] {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T, const N: usize> AsMut<[T]> for [T; N] {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T, const N: usize> const AsMut<[T]> for [T; N] {
     #[inline]
     fn as_mut(&mut self) -> &mut [T] {
         &mut self[..]
@@ -216,14 +218,16 @@ impl<T, const N: usize> AsMut<[T]> for [T; N] {
 }
 
 #[stable(feature = "array_borrow", since = "1.4.0")]
-impl<T, const N: usize> Borrow<[T]> for [T; N] {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T, const N: usize> const Borrow<[T]> for [T; N] {
     fn borrow(&self) -> &[T] {
         self
     }
 }
 
 #[stable(feature = "array_borrow", since = "1.4.0")]
-impl<T, const N: usize> BorrowMut<[T]> for [T; N] {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T, const N: usize> const BorrowMut<[T]> for [T; N] {
     fn borrow_mut(&mut self) -> &mut [T] {
         self
     }
@@ -242,7 +246,8 @@ impl<T, const N: usize> BorrowMut<[T]> for [T; N] {
 /// assert_eq!(512, u16::from_le_bytes(bytes_tail));
 /// ```
 #[stable(feature = "try_from", since = "1.34.0")]
-impl<T, const N: usize> TryFrom<&[T]> for [T; N]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T, const N: usize> const TryFrom<&[T]> for [T; N]
 where
     T: Copy,
 {
@@ -267,7 +272,8 @@ where
 /// assert_eq!(512, u16::from_le_bytes(bytes_tail));
 /// ```
 #[stable(feature = "try_from_mut_slice_to_array", since = "1.59.0")]
-impl<T, const N: usize> TryFrom<&mut [T]> for [T; N]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T, const N: usize> const TryFrom<&mut [T]> for [T; N]
 where
     T: Copy,
 {
@@ -292,7 +298,8 @@ where
 /// assert_eq!(512, u16::from_le_bytes(*bytes_tail));
 /// ```
 #[stable(feature = "try_from", since = "1.34.0")]
-impl<'a, T, const N: usize> TryFrom<&'a [T]> for &'a [T; N] {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<'a, T, const N: usize> const TryFrom<&'a [T]> for &'a [T; N] {
     type Error = TryFromSliceError;
 
     #[inline]
@@ -314,7 +321,8 @@ impl<'a, T, const N: usize> TryFrom<&'a [T]> for &'a [T; N] {
 /// assert_eq!(512, u16::from_le_bytes(*bytes_tail));
 /// ```
 #[stable(feature = "try_from", since = "1.34.0")]
-impl<'a, T, const N: usize> TryFrom<&'a mut [T]> for &'a mut [T; N] {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<'a, T, const N: usize> const TryFrom<&'a mut [T]> for &'a mut [T; N] {
     type Error = TryFromSliceError;
 
     #[inline]
diff --git a/library/core/src/ascii/ascii_char.rs b/library/core/src/ascii/ascii_char.rs
index 419e4694594..49d540314a2 100644
--- a/library/core/src/ascii/ascii_char.rs
+++ b/library/core/src/ascii/ascii_char.rs
@@ -1156,7 +1156,7 @@ macro_rules! into_int_impl {
     ($($ty:ty)*) => {
         $(
             #[unstable(feature = "ascii_char", issue = "110998")]
-            #[rustc_const_unstable(feature = "const_try", issue = "74935")]
+            #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
             impl const From<AsciiChar> for $ty {
                 #[inline]
                 fn from(chr: AsciiChar) -> $ty {
diff --git a/library/core/src/borrow.rs b/library/core/src/borrow.rs
index da05f236d2f..6ce7e4656b9 100644
--- a/library/core/src/borrow.rs
+++ b/library/core/src/borrow.rs
@@ -154,6 +154,8 @@
 /// [`String`]: ../../std/string/struct.String.html
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_diagnostic_item = "Borrow"]
+#[const_trait]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 pub trait Borrow<Borrowed: ?Sized> {
     /// Immutably borrows from an owned value.
     ///
@@ -185,6 +187,8 @@ pub trait Borrow<Borrowed: ?Sized> {
 /// for more information on borrowing as another type.
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_diagnostic_item = "BorrowMut"]
+#[const_trait]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 pub trait BorrowMut<Borrowed: ?Sized>: Borrow<Borrowed> {
     /// Mutably borrows from an owned value.
     ///
@@ -206,7 +210,8 @@ pub trait BorrowMut<Borrowed: ?Sized>: Borrow<Borrowed> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> Borrow<T> for T {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T: ?Sized> const Borrow<T> for T {
     #[rustc_diagnostic_item = "noop_method_borrow"]
     fn borrow(&self) -> &T {
         self
@@ -214,28 +219,32 @@ impl<T: ?Sized> Borrow<T> for T {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> BorrowMut<T> for T {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T: ?Sized> const BorrowMut<T> for T {
     fn borrow_mut(&mut self) -> &mut T {
         self
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> Borrow<T> for &T {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T: ?Sized> const Borrow<T> for &T {
     fn borrow(&self) -> &T {
         self
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> Borrow<T> for &mut T {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T: ?Sized> const Borrow<T> for &mut T {
     fn borrow(&self) -> &T {
         self
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> BorrowMut<T> for &mut T {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T: ?Sized> const BorrowMut<T> for &mut T {
     fn borrow_mut(&mut self) -> &mut T {
         self
     }
diff --git a/library/core/src/bstr/mod.rs b/library/core/src/bstr/mod.rs
index 13127d645a2..e13dc5cd44d 100644
--- a/library/core/src/bstr/mod.rs
+++ b/library/core/src/bstr/mod.rs
@@ -63,14 +63,16 @@ impl ByteStr {
     /// ```
     #[inline]
     #[unstable(feature = "bstr", issue = "134915")]
-    pub fn new<B: ?Sized + AsRef<[u8]>>(bytes: &B) -> &Self {
+    #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+    pub const fn new<B: ?Sized + [const] AsRef<[u8]>>(bytes: &B) -> &Self {
         ByteStr::from_bytes(bytes.as_ref())
     }
 
     #[doc(hidden)]
     #[unstable(feature = "bstr_internals", issue = "none")]
     #[inline]
-    pub fn from_bytes(slice: &[u8]) -> &Self {
+    #[rustc_const_unstable(feature = "bstr_internals", issue = "none")]
+    pub const fn from_bytes(slice: &[u8]) -> &Self {
         // SAFETY: `ByteStr` is a transparent wrapper around `[u8]`, so we can turn a reference to
         // the wrapped type into a reference to the wrapper type.
         unsafe { &*(slice as *const [u8] as *const Self) }
@@ -79,7 +81,8 @@ impl ByteStr {
     #[doc(hidden)]
     #[unstable(feature = "bstr_internals", issue = "none")]
     #[inline]
-    pub fn from_bytes_mut(slice: &mut [u8]) -> &mut Self {
+    #[rustc_const_unstable(feature = "bstr_internals", issue = "none")]
+    pub const fn from_bytes_mut(slice: &mut [u8]) -> &mut Self {
         // SAFETY: `ByteStr` is a transparent wrapper around `[u8]`, so we can turn a reference to
         // the wrapped type into a reference to the wrapper type.
         unsafe { &mut *(slice as *mut [u8] as *mut Self) }
@@ -88,20 +91,23 @@ impl ByteStr {
     #[doc(hidden)]
     #[unstable(feature = "bstr_internals", issue = "none")]
     #[inline]
-    pub fn as_bytes(&self) -> &[u8] {
+    #[rustc_const_unstable(feature = "bstr_internals", issue = "none")]
+    pub const fn as_bytes(&self) -> &[u8] {
         &self.0
     }
 
     #[doc(hidden)]
     #[unstable(feature = "bstr_internals", issue = "none")]
     #[inline]
-    pub fn as_bytes_mut(&mut self) -> &mut [u8] {
+    #[rustc_const_unstable(feature = "bstr_internals", issue = "none")]
+    pub const fn as_bytes_mut(&mut self) -> &mut [u8] {
         &mut self.0
     }
 }
 
 #[unstable(feature = "bstr", issue = "134915")]
-impl Deref for ByteStr {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const Deref for ByteStr {
     type Target = [u8];
 
     #[inline]
@@ -111,7 +117,8 @@ impl Deref for ByteStr {
 }
 
 #[unstable(feature = "bstr", issue = "134915")]
-impl DerefMut for ByteStr {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const DerefMut for ByteStr {
     #[inline]
     fn deref_mut(&mut self) -> &mut [u8] {
         &mut self.0
@@ -185,7 +192,8 @@ impl fmt::Display for ByteStr {
 }
 
 #[unstable(feature = "bstr", issue = "134915")]
-impl AsRef<[u8]> for ByteStr {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const AsRef<[u8]> for ByteStr {
     #[inline]
     fn as_ref(&self) -> &[u8] {
         &self.0
@@ -193,7 +201,8 @@ impl AsRef<[u8]> for ByteStr {
 }
 
 #[unstable(feature = "bstr", issue = "134915")]
-impl AsRef<ByteStr> for ByteStr {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const AsRef<ByteStr> for ByteStr {
     #[inline]
     fn as_ref(&self) -> &ByteStr {
         self
@@ -203,7 +212,8 @@ impl AsRef<ByteStr> for ByteStr {
 // `impl AsRef<ByteStr> for [u8]` omitted to avoid widespread inference failures
 
 #[unstable(feature = "bstr", issue = "134915")]
-impl AsRef<ByteStr> for str {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const AsRef<ByteStr> for str {
     #[inline]
     fn as_ref(&self) -> &ByteStr {
         ByteStr::new(self)
@@ -211,7 +221,8 @@ impl AsRef<ByteStr> for str {
 }
 
 #[unstable(feature = "bstr", issue = "134915")]
-impl AsMut<[u8]> for ByteStr {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const AsMut<[u8]> for ByteStr {
     #[inline]
     fn as_mut(&mut self) -> &mut [u8] {
         &mut self.0
@@ -225,7 +236,8 @@ impl AsMut<[u8]> for ByteStr {
 // `impl Borrow<ByteStr> for str` omitted to avoid widespread inference failures
 
 #[unstable(feature = "bstr", issue = "134915")]
-impl Borrow<[u8]> for ByteStr {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const Borrow<[u8]> for ByteStr {
     #[inline]
     fn borrow(&self) -> &[u8] {
         &self.0
@@ -235,7 +247,8 @@ impl Borrow<[u8]> for ByteStr {
 // `impl BorrowMut<ByteStr> for [u8]` omitted to avoid widespread inference failures
 
 #[unstable(feature = "bstr", issue = "134915")]
-impl BorrowMut<[u8]> for ByteStr {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const BorrowMut<[u8]> for ByteStr {
     #[inline]
     fn borrow_mut(&mut self) -> &mut [u8] {
         &mut self.0
@@ -303,7 +316,8 @@ impl<'a> Default for &'a mut ByteStr {
 // }
 
 #[unstable(feature = "bstr", issue = "134915")]
-impl<'a> TryFrom<&'a ByteStr> for &'a str {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<'a> const TryFrom<&'a ByteStr> for &'a str {
     type Error = crate::str::Utf8Error;
 
     #[inline]
@@ -313,7 +327,8 @@ impl<'a> TryFrom<&'a ByteStr> for &'a str {
 }
 
 #[unstable(feature = "bstr", issue = "134915")]
-impl<'a> TryFrom<&'a mut ByteStr> for &'a mut str {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<'a> const TryFrom<&'a mut ByteStr> for &'a mut str {
     type Error = crate::str::Utf8Error;
 
     #[inline]
diff --git a/library/core/src/cell.rs b/library/core/src/cell.rs
index 59a6aa70620..9b53b75ebee 100644
--- a/library/core/src/cell.rs
+++ b/library/core/src/cell.rs
@@ -390,7 +390,8 @@ impl<T: Ord + Copy> Ord for Cell<T> {
 }
 
 #[stable(feature = "cell_from", since = "1.12.0")]
-impl<T> From<T> for Cell<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T> const From<T> for Cell<T> {
     /// Creates a new `Cell<T>` containing the given value.
     fn from(t: T) -> Cell<T> {
         Cell::new(t)
@@ -1402,7 +1403,8 @@ impl<T: ?Sized + Ord> Ord for RefCell<T> {
 }
 
 #[stable(feature = "cell_from", since = "1.12.0")]
-impl<T> From<T> for RefCell<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T> const From<T> for RefCell<T> {
     /// Creates a new `RefCell<T>` containing the given value.
     fn from(t: T) -> RefCell<T> {
         RefCell::new(t)
@@ -1483,7 +1485,7 @@ pub struct Ref<'b, T: ?Sized + 'b> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_deref", issue = "88955")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T: ?Sized> const Deref for Ref<'_, T> {
     type Target = T;
 
@@ -1967,7 +1969,7 @@ pub struct RefMut<'b, T: ?Sized + 'b> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_deref", issue = "88955")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T: ?Sized> const Deref for RefMut<'_, T> {
     type Target = T;
 
@@ -1979,7 +1981,7 @@ impl<T: ?Sized> const Deref for RefMut<'_, T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_deref", issue = "88955")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T: ?Sized> const DerefMut for RefMut<'_, T> {
     #[inline]
     fn deref_mut(&mut self) -> &mut T {
@@ -2434,7 +2436,8 @@ impl<T: [const] Default> const Default for UnsafeCell<T> {
 }
 
 #[stable(feature = "cell_from", since = "1.12.0")]
-impl<T> From<T> for UnsafeCell<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T> const From<T> for UnsafeCell<T> {
     /// Creates a new `UnsafeCell<T>` containing the given value.
     fn from(t: T) -> UnsafeCell<T> {
         UnsafeCell::new(t)
@@ -2539,7 +2542,8 @@ impl<T: [const] Default> const Default for SyncUnsafeCell<T> {
 }
 
 #[unstable(feature = "sync_unsafe_cell", issue = "95439")]
-impl<T> From<T> for SyncUnsafeCell<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T> const From<T> for SyncUnsafeCell<T> {
     /// Creates a new `SyncUnsafeCell<T>` containing the given value.
     fn from(t: T) -> SyncUnsafeCell<T> {
         SyncUnsafeCell::new(t)
diff --git a/library/core/src/cell/once.rs b/library/core/src/cell/once.rs
index c6c96571d33..833be059d75 100644
--- a/library/core/src/cell/once.rs
+++ b/library/core/src/cell/once.rs
@@ -395,7 +395,8 @@ impl<T: PartialEq> PartialEq for OnceCell<T> {
 impl<T: Eq> Eq for OnceCell<T> {}
 
 #[stable(feature = "once_cell", since = "1.70.0")]
-impl<T> From<T> for OnceCell<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T> const From<T> for OnceCell<T> {
     /// Creates a new `OnceCell<T>` which already contains the given `value`.
     #[inline]
     fn from(value: T) -> Self {
diff --git a/library/core/src/char/convert.rs b/library/core/src/char/convert.rs
index cf5a91bf8dd..6380f42d320 100644
--- a/library/core/src/char/convert.rs
+++ b/library/core/src/char/convert.rs
@@ -36,7 +36,7 @@ pub(super) const unsafe fn from_u32_unchecked(i: u32) -> char {
 }
 
 #[stable(feature = "char_convert", since = "1.13.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<char> for u32 {
     /// Converts a [`char`] into a [`u32`].
     ///
@@ -54,7 +54,7 @@ impl const From<char> for u32 {
 }
 
 #[stable(feature = "more_char_conversions", since = "1.51.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<char> for u64 {
     /// Converts a [`char`] into a [`u64`].
     ///
@@ -74,7 +74,7 @@ impl const From<char> for u64 {
 }
 
 #[stable(feature = "more_char_conversions", since = "1.51.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<char> for u128 {
     /// Converts a [`char`] into a [`u128`].
     ///
@@ -98,7 +98,8 @@ impl const From<char> for u128 {
 ///
 /// See [`impl From<u8> for char`](char#impl-From<u8>-for-char) for details on the encoding.
 #[stable(feature = "u8_from_char", since = "1.59.0")]
-impl TryFrom<char> for u8 {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const TryFrom<char> for u8 {
     type Error = TryFromCharError;
 
     /// Tries to convert a [`char`] into a [`u8`].
@@ -113,7 +114,11 @@ impl TryFrom<char> for u8 {
     /// ```
     #[inline]
     fn try_from(c: char) -> Result<u8, Self::Error> {
-        u8::try_from(u32::from(c)).map_err(|_| TryFromCharError(()))
+        // FIXME(const-hack): this should use map_err instead
+        match u8::try_from(u32::from(c)) {
+            Ok(b) => Ok(b),
+            Err(_) => Err(TryFromCharError(())),
+        }
     }
 }
 
@@ -122,7 +127,8 @@ impl TryFrom<char> for u8 {
 ///
 /// This corresponds to the UCS-2 encoding, as specified in ISO/IEC 10646:2003.
 #[stable(feature = "u16_from_char", since = "1.74.0")]
-impl TryFrom<char> for u16 {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const TryFrom<char> for u16 {
     type Error = TryFromCharError;
 
     /// Tries to convert a [`char`] into a [`u16`].
@@ -137,7 +143,11 @@ impl TryFrom<char> for u16 {
     /// ```
     #[inline]
     fn try_from(c: char) -> Result<u16, Self::Error> {
-        u16::try_from(u32::from(c)).map_err(|_| TryFromCharError(()))
+        // FIXME(const-hack): this should use map_err instead
+        match u16::try_from(u32::from(c)) {
+            Ok(x) => Ok(x),
+            Err(_) => Err(TryFromCharError(())),
+        }
     }
 }
 
@@ -160,7 +170,7 @@ impl TryFrom<char> for u16 {
 /// for a superset of Windows-1252 that fills the remaining blanks with corresponding
 /// C0 and C1 control codes.
 #[stable(feature = "char_convert", since = "1.13.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<u8> for char {
     /// Converts a [`u8`] into a [`char`].
     ///
@@ -246,7 +256,7 @@ const fn char_try_from_u32(i: u32) -> Result<char, CharTryFromError> {
 }
 
 #[stable(feature = "try_from", since = "1.34.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const TryFrom<u32> for char {
     type Error = CharTryFromError;
 
diff --git a/library/core/src/convert/mod.rs b/library/core/src/convert/mod.rs
index a0a7b7928d1..add21b491ad 100644
--- a/library/core/src/convert/mod.rs
+++ b/library/core/src/convert/mod.rs
@@ -217,7 +217,7 @@ pub const fn identity<T>(x: T) -> T {
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_diagnostic_item = "AsRef"]
 #[const_trait]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 pub trait AsRef<T: PointeeSized>: PointeeSized {
     /// Converts this type into a shared reference of the (usually inferred) input type.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -370,7 +370,7 @@ pub trait AsRef<T: PointeeSized>: PointeeSized {
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_diagnostic_item = "AsMut"]
 #[const_trait]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 pub trait AsMut<T: PointeeSized>: PointeeSized {
     /// Converts this type into a mutable reference of the (usually inferred) input type.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -449,7 +449,7 @@ pub trait AsMut<T: PointeeSized>: PointeeSized {
 #[rustc_diagnostic_item = "Into"]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[doc(search_unbox)]
-#[rustc_const_unstable(feature = "const_from", issue = "143773")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 #[const_trait]
 pub trait Into<T>: Sized {
     /// Converts this type into the (usually inferred) input type.
@@ -586,7 +586,7 @@ pub trait Into<T>: Sized {
     note = "to coerce a `{T}` into a `{Self}`, use `&*` as a prefix",
 ))]
 #[doc(search_unbox)]
-#[rustc_const_unstable(feature = "const_from", issue = "143773")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 #[const_trait]
 pub trait From<T>: Sized {
     /// Converts to this type from the input type.
@@ -615,7 +615,7 @@ pub trait From<T>: Sized {
 /// [`Into`], see there for details.
 #[rustc_diagnostic_item = "TryInto"]
 #[stable(feature = "try_from", since = "1.34.0")]
-#[rustc_const_unstable(feature = "const_from", issue = "143773")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 #[const_trait]
 pub trait TryInto<T>: Sized {
     /// The type returned in the event of a conversion error.
@@ -695,7 +695,7 @@ pub trait TryInto<T>: Sized {
 /// [`try_from`]: TryFrom::try_from
 #[rustc_diagnostic_item = "TryFrom"]
 #[stable(feature = "try_from", since = "1.34.0")]
-#[rustc_const_unstable(feature = "const_from", issue = "143773")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 #[const_trait]
 pub trait TryFrom<T>: Sized {
     /// The type returned in the event of a conversion error.
@@ -714,7 +714,7 @@ pub trait TryFrom<T>: Sized {
 
 // As lifts over &
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T: PointeeSized, U: PointeeSized> const AsRef<U> for &T
 where
     T: [const] AsRef<U>,
@@ -727,7 +727,7 @@ where
 
 // As lifts over &mut
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T: PointeeSized, U: PointeeSized> const AsRef<U> for &mut T
 where
     T: [const] AsRef<U>,
@@ -748,7 +748,7 @@ where
 
 // AsMut lifts over &mut
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T: PointeeSized, U: PointeeSized> const AsMut<U> for &mut T
 where
     T: [const] AsMut<U>,
@@ -769,7 +769,7 @@ where
 
 // From implies Into
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_from", issue = "143773")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T, U> const Into<U> for T
 where
     U: [const] From<T>,
@@ -787,7 +787,7 @@ where
 
 // From (and thus Into) is reflexive
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_from", issue = "143773")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T> const From<T> for T {
     /// Returns the argument unchanged.
     #[inline(always)]
@@ -804,7 +804,7 @@ impl<T> const From<T> for T {
 #[stable(feature = "convert_infallible", since = "1.34.0")]
 #[rustc_reservation_impl = "permitting this impl would forbid us from adding \
                             `impl<T> From<!> for T` later; see rust-lang/rust#64715 for details"]
-#[rustc_const_unstable(feature = "const_from", issue = "143773")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T> const From<!> for T {
     fn from(t: !) -> T {
         t
@@ -813,7 +813,7 @@ impl<T> const From<!> for T {
 
 // TryFrom implies TryInto
 #[stable(feature = "try_from", since = "1.34.0")]
-#[rustc_const_unstable(feature = "const_from", issue = "143773")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T, U> const TryInto<U> for T
 where
     U: [const] TryFrom<T>,
@@ -829,7 +829,7 @@ where
 // Infallible conversions are semantically equivalent to fallible conversions
 // with an uninhabited error type.
 #[stable(feature = "try_from", since = "1.34.0")]
-#[rustc_const_unstable(feature = "const_from", issue = "143773")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T, U> const TryFrom<U> for T
 where
     U: [const] Into<T>,
@@ -847,7 +847,7 @@ where
 ////////////////////////////////////////////////////////////////////////////////
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T> const AsRef<[T]> for [T] {
     #[inline(always)]
     fn as_ref(&self) -> &[T] {
@@ -856,7 +856,7 @@ impl<T> const AsRef<[T]> for [T] {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T> const AsMut<[T]> for [T] {
     #[inline(always)]
     fn as_mut(&mut self) -> &mut [T] {
@@ -865,7 +865,7 @@ impl<T> const AsMut<[T]> for [T] {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const AsRef<str> for str {
     #[inline(always)]
     fn as_ref(&self) -> &str {
@@ -874,7 +874,7 @@ impl const AsRef<str> for str {
 }
 
 #[stable(feature = "as_mut_str_for_str", since = "1.51.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const AsMut<str> for str {
     #[inline(always)]
     fn as_mut(&mut self) -> &mut str {
@@ -936,7 +936,7 @@ impl const AsMut<str> for str {
 pub enum Infallible {}
 
 #[stable(feature = "convert_infallible", since = "1.34.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_clone", issue = "142757")]
 impl const Clone for Infallible {
     fn clone(&self) -> Infallible {
         match *self {}
@@ -986,7 +986,7 @@ impl Ord for Infallible {
 }
 
 #[stable(feature = "convert_infallible", since = "1.34.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<!> for Infallible {
     #[inline]
     fn from(x: !) -> Self {
diff --git a/library/core/src/convert/num.rs b/library/core/src/convert/num.rs
index affb4eb64d3..6ae588a4e04 100644
--- a/library/core/src/convert/num.rs
+++ b/library/core/src/convert/num.rs
@@ -69,7 +69,7 @@ macro_rules! impl_from {
     };
     ($Small:ty => $Large:ty, #[$attr:meta], $doc:expr $(,)?) => {
         #[$attr]
-        #[rustc_const_unstable(feature = "const_try", issue = "74935")]
+        #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
         impl const From<$Small> for $Large {
             // Rustdocs on the impl block show a "[+] show undocumented items" toggle.
             // Rustdocs on functions do not.
@@ -201,7 +201,7 @@ macro_rules! impl_float_from_bool {
         )?
     ) => {
         #[stable(feature = "float_from_bool", since = "1.68.0")]
-        #[rustc_const_unstable(feature = "const_try", issue = "74935")]
+        #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
             impl const From<bool> for $float {
             #[doc = concat!("Converts a [`bool`] to [`", stringify!($float),"`] losslessly.")]
             /// The resulting value is positive `0.0` for `false` and `1.0` for `true` values.
@@ -252,7 +252,7 @@ impl_float_from_bool!(
 macro_rules! impl_try_from_unbounded {
     ($source:ty => $($target:ty),+) => {$(
         #[stable(feature = "try_from", since = "1.34.0")]
-        #[rustc_const_unstable(feature = "const_try", issue = "74935")]
+        #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
         impl const TryFrom<$source> for $target {
             type Error = TryFromIntError;
 
@@ -271,7 +271,7 @@ macro_rules! impl_try_from_unbounded {
 macro_rules! impl_try_from_lower_bounded {
     ($source:ty => $($target:ty),+) => {$(
         #[stable(feature = "try_from", since = "1.34.0")]
-        #[rustc_const_unstable(feature = "const_try", issue = "74935")]
+        #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
         impl const TryFrom<$source> for $target {
             type Error = TryFromIntError;
 
@@ -294,7 +294,7 @@ macro_rules! impl_try_from_lower_bounded {
 macro_rules! impl_try_from_upper_bounded {
     ($source:ty => $($target:ty),+) => {$(
         #[stable(feature = "try_from", since = "1.34.0")]
-        #[rustc_const_unstable(feature = "const_try", issue = "74935")]
+        #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
         impl const TryFrom<$source> for $target {
             type Error = TryFromIntError;
 
@@ -317,7 +317,7 @@ macro_rules! impl_try_from_upper_bounded {
 macro_rules! impl_try_from_both_bounded {
     ($source:ty => $($target:ty),+) => {$(
         #[stable(feature = "try_from", since = "1.34.0")]
-        #[rustc_const_unstable(feature = "const_try", issue = "74935")]
+        #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
         impl const TryFrom<$source> for $target {
             type Error = TryFromIntError;
 
@@ -456,7 +456,7 @@ use crate::num::NonZero;
 macro_rules! impl_nonzero_int_from_nonzero_int {
     ($Small:ty => $Large:ty) => {
         #[stable(feature = "nz_int_conv", since = "1.41.0")]
-        #[rustc_const_unstable(feature = "const_try", issue = "74935")]
+        #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
         impl const From<NonZero<$Small>> for NonZero<$Large> {
             // Rustdocs on the impl block show a "[+] show undocumented items" toggle.
             // Rustdocs on functions do not.
@@ -515,7 +515,8 @@ impl_nonzero_int_from_nonzero_int!(u64 => i128);
 macro_rules! impl_nonzero_int_try_from_int {
     ($Int:ty) => {
         #[stable(feature = "nzint_try_from_int_conv", since = "1.46.0")]
-        impl TryFrom<$Int> for NonZero<$Int> {
+        #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+        impl const TryFrom<$Int> for NonZero<$Int> {
             type Error = TryFromIntError;
 
             // Rustdocs on the impl block show a "[+] show undocumented items" toggle.
@@ -547,7 +548,7 @@ impl_nonzero_int_try_from_int!(isize);
 macro_rules! impl_nonzero_int_try_from_nonzero_int {
     ($source:ty => $($target:ty),+) => {$(
         #[stable(feature = "nzint_try_from_nzint_conv", since = "1.49.0")]
-        #[rustc_const_unstable(feature = "const_try", issue = "74935")]
+        #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
         impl const TryFrom<NonZero<$source>> for NonZero<$target> {
             type Error = TryFromIntError;
 
diff --git a/library/core/src/ffi/c_str.rs b/library/core/src/ffi/c_str.rs
index e6b599fafcf..d0b53e3a237 100644
--- a/library/core/src/ffi/c_str.rs
+++ b/library/core/src/ffi/c_str.rs
@@ -708,7 +708,8 @@ impl ops::Index<ops::RangeFrom<usize>> for CStr {
 }
 
 #[stable(feature = "cstring_asref", since = "1.7.0")]
-impl AsRef<CStr> for CStr {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const AsRef<CStr> for CStr {
     #[inline]
     fn as_ref(&self) -> &CStr {
         self
diff --git a/library/core/src/mem/manually_drop.rs b/library/core/src/mem/manually_drop.rs
index 02bb8179293..8868f05f1b9 100644
--- a/library/core/src/mem/manually_drop.rs
+++ b/library/core/src/mem/manually_drop.rs
@@ -258,7 +258,8 @@ impl<T: ?Sized> ManuallyDrop<T> {
 }
 
 #[stable(feature = "manually_drop", since = "1.20.0")]
-impl<T: ?Sized> Deref for ManuallyDrop<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T: ?Sized> const Deref for ManuallyDrop<T> {
     type Target = T;
     #[inline(always)]
     fn deref(&self) -> &T {
@@ -267,7 +268,8 @@ impl<T: ?Sized> Deref for ManuallyDrop<T> {
 }
 
 #[stable(feature = "manually_drop", since = "1.20.0")]
-impl<T: ?Sized> DerefMut for ManuallyDrop<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T: ?Sized> const DerefMut for ManuallyDrop<T> {
     #[inline(always)]
     fn deref_mut(&mut self) -> &mut T {
         &mut self.value
diff --git a/library/core/src/net/ip_addr.rs b/library/core/src/net/ip_addr.rs
index 3bf113d017c..9779fb8fe4d 100644
--- a/library/core/src/net/ip_addr.rs
+++ b/library/core/src/net/ip_addr.rs
@@ -1087,7 +1087,7 @@ impl fmt::Debug for IpAddr {
 }
 
 #[stable(feature = "ip_from_ip", since = "1.16.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<Ipv4Addr> for IpAddr {
     /// Copies this address to a new `IpAddr::V4`.
     ///
@@ -1110,7 +1110,7 @@ impl const From<Ipv4Addr> for IpAddr {
 }
 
 #[stable(feature = "ip_from_ip", since = "1.16.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<Ipv6Addr> for IpAddr {
     /// Copies this address to a new `IpAddr::V6`.
     ///
@@ -1221,7 +1221,7 @@ impl Ord for Ipv4Addr {
 }
 
 #[stable(feature = "ip_u32", since = "1.1.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<Ipv4Addr> for u32 {
     /// Uses [`Ipv4Addr::to_bits`] to convert an IPv4 address to a host byte order `u32`.
     #[inline]
@@ -1231,7 +1231,7 @@ impl const From<Ipv4Addr> for u32 {
 }
 
 #[stable(feature = "ip_u32", since = "1.1.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<u32> for Ipv4Addr {
     /// Uses [`Ipv4Addr::from_bits`] to convert a host byte order `u32` into an IPv4 address.
     #[inline]
@@ -1241,7 +1241,7 @@ impl const From<u32> for Ipv4Addr {
 }
 
 #[stable(feature = "from_slice_v4", since = "1.9.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<[u8; 4]> for Ipv4Addr {
     /// Creates an `Ipv4Addr` from a four element byte array.
     ///
@@ -1260,7 +1260,7 @@ impl const From<[u8; 4]> for Ipv4Addr {
 }
 
 #[stable(feature = "ip_from_slice", since = "1.17.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<[u8; 4]> for IpAddr {
     /// Creates an `IpAddr::V4` from a four element byte array.
     ///
@@ -2215,7 +2215,7 @@ impl Ord for Ipv6Addr {
 }
 
 #[stable(feature = "i128", since = "1.26.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<Ipv6Addr> for u128 {
     /// Uses [`Ipv6Addr::to_bits`] to convert an IPv6 address to a host byte order `u128`.
     #[inline]
@@ -2224,7 +2224,7 @@ impl const From<Ipv6Addr> for u128 {
     }
 }
 #[stable(feature = "i128", since = "1.26.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<u128> for Ipv6Addr {
     /// Uses [`Ipv6Addr::from_bits`] to convert a host byte order `u128` to an IPv6 address.
     #[inline]
@@ -2234,7 +2234,7 @@ impl const From<u128> for Ipv6Addr {
 }
 
 #[stable(feature = "ipv6_from_octets", since = "1.9.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<[u8; 16]> for Ipv6Addr {
     /// Creates an `Ipv6Addr` from a sixteen element byte array.
     ///
@@ -2262,7 +2262,7 @@ impl const From<[u8; 16]> for Ipv6Addr {
 }
 
 #[stable(feature = "ipv6_from_segments", since = "1.16.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<[u16; 8]> for Ipv6Addr {
     /// Creates an `Ipv6Addr` from an eight element 16-bit array.
     ///
@@ -2291,7 +2291,7 @@ impl const From<[u16; 8]> for Ipv6Addr {
 }
 
 #[stable(feature = "ip_from_slice", since = "1.17.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<[u8; 16]> for IpAddr {
     /// Creates an `IpAddr::V6` from a sixteen element byte array.
     ///
@@ -2319,7 +2319,7 @@ impl const From<[u8; 16]> for IpAddr {
 }
 
 #[stable(feature = "ip_from_slice", since = "1.17.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<[u16; 8]> for IpAddr {
     /// Creates an `IpAddr::V6` from an eight element 16-bit array.
     ///
diff --git a/library/core/src/net/socket_addr.rs b/library/core/src/net/socket_addr.rs
index df99e9b20c2..ccc53c156d3 100644
--- a/library/core/src/net/socket_addr.rs
+++ b/library/core/src/net/socket_addr.rs
@@ -592,7 +592,7 @@ impl SocketAddrV6 {
 }
 
 #[stable(feature = "ip_from_ip", since = "1.16.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<SocketAddrV4> for SocketAddr {
     /// Converts a [`SocketAddrV4`] into a [`SocketAddr::V4`].
     #[inline]
@@ -602,7 +602,7 @@ impl const From<SocketAddrV4> for SocketAddr {
 }
 
 #[stable(feature = "ip_from_ip", since = "1.16.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<SocketAddrV6> for SocketAddr {
     /// Converts a [`SocketAddrV6`] into a [`SocketAddr::V6`].
     #[inline]
@@ -612,7 +612,7 @@ impl const From<SocketAddrV6> for SocketAddr {
 }
 
 #[stable(feature = "addr_from_into_ip", since = "1.17.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<I: [const] Into<IpAddr>> const From<(I, u16)> for SocketAddr {
     /// Converts a tuple struct (Into<[`IpAddr`]>, `u16`) into a [`SocketAddr`].
     ///
diff --git a/library/core/src/num/error.rs b/library/core/src/num/error.rs
index faa52329827..8a353dc0fbe 100644
--- a/library/core/src/num/error.rs
+++ b/library/core/src/num/error.rs
@@ -20,7 +20,7 @@ impl fmt::Display for TryFromIntError {
 impl Error for TryFromIntError {}
 
 #[stable(feature = "try_from", since = "1.34.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<Infallible> for TryFromIntError {
     fn from(x: Infallible) -> TryFromIntError {
         match x {}
@@ -28,7 +28,7 @@ impl const From<Infallible> for TryFromIntError {
 }
 
 #[unstable(feature = "never_type", issue = "35121")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<!> for TryFromIntError {
     #[inline]
     fn from(never: !) -> TryFromIntError {
diff --git a/library/core/src/num/mod.rs b/library/core/src/num/mod.rs
index acfe38b7a37..69c6a7dbd89 100644
--- a/library/core/src/num/mod.rs
+++ b/library/core/src/num/mod.rs
@@ -1378,7 +1378,7 @@ const fn from_ascii_radix_panic(radix: u32) -> ! {
 macro_rules! from_str_int_impl {
     ($signedness:ident $($int_ty:ty)+) => {$(
         #[stable(feature = "rust1", since = "1.0.0")]
-        #[rustc_const_unstable(feature = "const_try", issue = "74935")]
+        #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
         impl const FromStr for $int_ty {
             type Err = ParseIntError;
 
diff --git a/library/core/src/num/nonzero.rs b/library/core/src/num/nonzero.rs
index e02d9260a16..0f38081c355 100644
--- a/library/core/src/num/nonzero.rs
+++ b/library/core/src/num/nonzero.rs
@@ -297,7 +297,7 @@ where
 }
 
 #[stable(feature = "from_nonzero", since = "1.31.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T> const From<NonZero<T>> for T
 where
     T: ZeroablePrimitive,
diff --git a/library/core/src/ops/deref.rs b/library/core/src/ops/deref.rs
index 5f68c1f55c2..877b83d3a61 100644
--- a/library/core/src/ops/deref.rs
+++ b/library/core/src/ops/deref.rs
@@ -136,7 +136,7 @@ use crate::marker::PointeeSized;
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_diagnostic_item = "Deref"]
 #[const_trait]
-#[rustc_const_unstable(feature = "const_deref", issue = "88955")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 pub trait Deref: PointeeSized {
     /// The resulting type after dereferencing.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -152,7 +152,7 @@ pub trait Deref: PointeeSized {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_deref", issue = "88955")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T: ?Sized> const Deref for &T {
     type Target = T;
 
@@ -166,7 +166,7 @@ impl<T: ?Sized> const Deref for &T {
 impl<T: ?Sized> !DerefMut for &T {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_deref", issue = "88955")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T: ?Sized> const Deref for &mut T {
     type Target = T;
 
@@ -268,7 +268,7 @@ impl<T: ?Sized> const Deref for &mut T {
 #[doc(alias = "*")]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[const_trait]
-#[rustc_const_unstable(feature = "const_deref", issue = "88955")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 pub trait DerefMut: [const] Deref + PointeeSized {
     /// Mutably dereferences the value.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -277,7 +277,7 @@ pub trait DerefMut: [const] Deref + PointeeSized {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_deref", issue = "88955")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T: ?Sized> const DerefMut for &mut T {
     fn deref_mut(&mut self) -> &mut T {
         self
diff --git a/library/core/src/option.rs b/library/core/src/option.rs
index fa09409b6da..2a57536500a 100644
--- a/library/core/src/option.rs
+++ b/library/core/src/option.rs
@@ -1379,11 +1379,12 @@ impl<T> Option<T> {
     /// ```
     #[inline]
     #[stable(feature = "option_deref", since = "1.40.0")]
-    pub fn as_deref(&self) -> Option<&T::Target>
+    #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+    pub const fn as_deref(&self) -> Option<&T::Target>
     where
-        T: Deref,
+        T: [const] Deref,
     {
-        self.as_ref().map(|t| t.deref())
+        self.as_ref().map(Deref::deref)
     }
 
     /// Converts from `Option<T>` (or `&mut Option<T>`) to `Option<&mut T::Target>`.
@@ -1402,11 +1403,12 @@ impl<T> Option<T> {
     /// ```
     #[inline]
     #[stable(feature = "option_deref", since = "1.40.0")]
-    pub fn as_deref_mut(&mut self) -> Option<&mut T::Target>
+    #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+    pub const fn as_deref_mut(&mut self) -> Option<&mut T::Target>
     where
-        T: DerefMut,
+        T: [const] DerefMut,
     {
-        self.as_mut().map(|t| t.deref_mut())
+        self.as_mut().map(DerefMut::deref_mut)
     }
 
     /////////////////////////////////////////////////////////////////////////
@@ -2180,7 +2182,7 @@ const fn expect_failed(msg: &str) -> ! {
 /////////////////////////////////////////////////////////////////////////////
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_clone", issue = "142757")]
 impl<T> const Clone for Option<T>
 where
     // FIXME(const_hack): the T: ~const Destruct should be inferred from the Self: ~const Destruct in clone_from.
@@ -2269,7 +2271,7 @@ impl<'a, T> IntoIterator for &'a mut Option<T> {
 }
 
 #[stable(since = "1.12.0", feature = "option_from")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T> const From<T> for Option<T> {
     /// Moves `val` into a new [`Some`].
     ///
@@ -2286,7 +2288,7 @@ impl<T> const From<T> for Option<T> {
 }
 
 #[stable(feature = "option_ref_from_ref_option", since = "1.30.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<'a, T> const From<&'a Option<T>> for Option<&'a T> {
     /// Converts from `&Option<T>` to `Option<&T>`.
     ///
@@ -2314,7 +2316,7 @@ impl<'a, T> const From<&'a Option<T>> for Option<&'a T> {
 }
 
 #[stable(feature = "option_ref_from_ref_option", since = "1.30.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<'a, T> const From<&'a mut Option<T>> for Option<&'a mut T> {
     /// Converts from `&mut Option<T>` to `Option<&mut T>`
     ///
diff --git a/library/core/src/panic/unwind_safe.rs b/library/core/src/panic/unwind_safe.rs
index a60f0799c0e..722af551038 100644
--- a/library/core/src/panic/unwind_safe.rs
+++ b/library/core/src/panic/unwind_safe.rs
@@ -248,7 +248,8 @@ impl RefUnwindSafe for crate::sync::atomic::AtomicBool {}
 impl<T> RefUnwindSafe for crate::sync::atomic::AtomicPtr<T> {}
 
 #[stable(feature = "catch_unwind", since = "1.9.0")]
-impl<T> Deref for AssertUnwindSafe<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T> const Deref for AssertUnwindSafe<T> {
     type Target = T;
 
     fn deref(&self) -> &T {
@@ -257,7 +258,8 @@ impl<T> Deref for AssertUnwindSafe<T> {
 }
 
 #[stable(feature = "catch_unwind", since = "1.9.0")]
-impl<T> DerefMut for AssertUnwindSafe<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T> const DerefMut for AssertUnwindSafe<T> {
     fn deref_mut(&mut self) -> &mut T {
         &mut self.0
     }
diff --git a/library/core/src/pin.rs b/library/core/src/pin.rs
index 14bf7ba9015..535830f2e74 100644
--- a/library/core/src/pin.rs
+++ b/library/core/src/pin.rs
@@ -1359,7 +1359,11 @@ impl<Ptr: Deref> Pin<Ptr> {
     /// ruled out by the contract of `Pin::new_unchecked`.
     #[stable(feature = "pin", since = "1.33.0")]
     #[inline(always)]
-    pub fn as_ref(&self) -> Pin<&Ptr::Target> {
+    #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+    pub const fn as_ref(&self) -> Pin<&Ptr::Target>
+    where
+        Ptr: [const] Deref,
+    {
         // SAFETY: see documentation on this function
         unsafe { Pin::new_unchecked(&*self.pointer) }
     }
@@ -1403,7 +1407,11 @@ impl<Ptr: DerefMut> Pin<Ptr> {
     /// ```
     #[stable(feature = "pin", since = "1.33.0")]
     #[inline(always)]
-    pub fn as_mut(&mut self) -> Pin<&mut Ptr::Target> {
+    #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+    pub const fn as_mut(&mut self) -> Pin<&mut Ptr::Target>
+    where
+        Ptr: [const] DerefMut,
+    {
         // SAFETY: see documentation on this function
         unsafe { Pin::new_unchecked(&mut *self.pointer) }
     }
@@ -1418,7 +1426,11 @@ impl<Ptr: DerefMut> Pin<Ptr> {
     #[stable(feature = "pin_deref_mut", since = "1.84.0")]
     #[must_use = "`self` will be dropped if the result is not used"]
     #[inline(always)]
-    pub fn as_deref_mut(self: Pin<&mut Self>) -> Pin<&mut Ptr::Target> {
+    #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+    pub const fn as_deref_mut(self: Pin<&mut Self>) -> Pin<&mut Ptr::Target>
+    where
+        Ptr: [const] DerefMut,
+    {
         // SAFETY: What we're asserting here is that going from
         //
         //     Pin<&mut Pin<Ptr>>
@@ -1669,7 +1681,8 @@ impl<T: ?Sized> Pin<&'static mut T> {
 }
 
 #[stable(feature = "pin", since = "1.33.0")]
-impl<Ptr: Deref> Deref for Pin<Ptr> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<Ptr: [const] Deref> const Deref for Pin<Ptr> {
     type Target = Ptr::Target;
     fn deref(&self) -> &Ptr::Target {
         Pin::get_ref(Pin::as_ref(self))
@@ -1677,7 +1690,8 @@ impl<Ptr: Deref> Deref for Pin<Ptr> {
 }
 
 #[stable(feature = "pin", since = "1.33.0")]
-impl<Ptr: DerefMut<Target: Unpin>> DerefMut for Pin<Ptr> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<Ptr: [const] DerefMut<Target: Unpin>> const DerefMut for Pin<Ptr> {
     fn deref_mut(&mut self) -> &mut Ptr::Target {
         Pin::get_mut(Pin::as_mut(self))
     }
diff --git a/library/core/src/pin/unsafe_pinned.rs b/library/core/src/pin/unsafe_pinned.rs
index ede6e0d6106..ae03809b458 100644
--- a/library/core/src/pin/unsafe_pinned.rs
+++ b/library/core/src/pin/unsafe_pinned.rs
@@ -148,7 +148,8 @@ impl<T: Default> Default for UnsafePinned<T> {
 }
 
 #[unstable(feature = "unsafe_pinned", issue = "125735")]
-impl<T> From<T> for UnsafePinned<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T> const From<T> for UnsafePinned<T> {
     /// Creates a new `UnsafePinned<T>` containing the given value.
     fn from(value: T) -> Self {
         UnsafePinned::new(value)
diff --git a/library/core/src/ptr/alignment.rs b/library/core/src/ptr/alignment.rs
index 402634e49b3..bc7d3a1de71 100644
--- a/library/core/src/ptr/alignment.rs
+++ b/library/core/src/ptr/alignment.rs
@@ -171,7 +171,8 @@ impl fmt::Debug for Alignment {
 }
 
 #[unstable(feature = "ptr_alignment_type", issue = "102070")]
-impl TryFrom<NonZero<usize>> for Alignment {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const TryFrom<NonZero<usize>> for Alignment {
     type Error = num::TryFromIntError;
 
     #[inline]
@@ -181,7 +182,8 @@ impl TryFrom<NonZero<usize>> for Alignment {
 }
 
 #[unstable(feature = "ptr_alignment_type", issue = "102070")]
-impl TryFrom<usize> for Alignment {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const TryFrom<usize> for Alignment {
     type Error = num::TryFromIntError;
 
     #[inline]
@@ -191,7 +193,7 @@ impl TryFrom<usize> for Alignment {
 }
 
 #[unstable(feature = "ptr_alignment_type", issue = "102070")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<Alignment> for NonZero<usize> {
     #[inline]
     fn from(align: Alignment) -> NonZero<usize> {
@@ -200,7 +202,7 @@ impl const From<Alignment> for NonZero<usize> {
 }
 
 #[unstable(feature = "ptr_alignment_type", issue = "102070")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<Alignment> for usize {
     #[inline]
     fn from(align: Alignment) -> usize {
diff --git a/library/core/src/ptr/non_null.rs b/library/core/src/ptr/non_null.rs
index 117eb18826e..10f83120428 100644
--- a/library/core/src/ptr/non_null.rs
+++ b/library/core/src/ptr/non_null.rs
@@ -1711,7 +1711,8 @@ impl<T: PointeeSized> hash::Hash for NonNull<T> {
 }
 
 #[unstable(feature = "ptr_internals", issue = "none")]
-impl<T: PointeeSized> From<Unique<T>> for NonNull<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T: PointeeSized> const From<Unique<T>> for NonNull<T> {
     #[inline]
     fn from(unique: Unique<T>) -> Self {
         unique.as_non_null_ptr()
@@ -1719,7 +1720,8 @@ impl<T: PointeeSized> From<Unique<T>> for NonNull<T> {
 }
 
 #[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: PointeeSized> From<&mut T> for NonNull<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T: PointeeSized> const From<&mut T> for NonNull<T> {
     /// Converts a `&mut T` to a `NonNull<T>`.
     ///
     /// This conversion is safe and infallible since references cannot be null.
@@ -1730,7 +1732,8 @@ impl<T: PointeeSized> From<&mut T> for NonNull<T> {
 }
 
 #[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: PointeeSized> From<&T> for NonNull<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T: PointeeSized> const From<&T> for NonNull<T> {
     /// Converts a `&T` to a `NonNull<T>`.
     ///
     /// This conversion is safe and infallible since references cannot be null.
diff --git a/library/core/src/ptr/unique.rs b/library/core/src/ptr/unique.rs
index 4302c1b1e44..cdc8b6cc936 100644
--- a/library/core/src/ptr/unique.rs
+++ b/library/core/src/ptr/unique.rs
@@ -189,7 +189,8 @@ impl<T: PointeeSized> fmt::Pointer for Unique<T> {
 }
 
 #[unstable(feature = "ptr_internals", issue = "none")]
-impl<T: PointeeSized> From<&mut T> for Unique<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T: PointeeSized> const From<&mut T> for Unique<T> {
     /// Converts a `&mut T` to a `Unique<T>`.
     ///
     /// This conversion is infallible since references cannot be null.
@@ -200,7 +201,8 @@ impl<T: PointeeSized> From<&mut T> for Unique<T> {
 }
 
 #[unstable(feature = "ptr_internals", issue = "none")]
-impl<T: PointeeSized> From<NonNull<T>> for Unique<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T: PointeeSized> const From<NonNull<T>> for Unique<T> {
     /// Converts a `NonNull<T>` to a `Unique<T>`.
     ///
     /// This conversion is infallible since `NonNull` cannot be null.
diff --git a/library/core/src/range.rs b/library/core/src/range.rs
index 7158fa0fcf0..332ae51d848 100644
--- a/library/core/src/range.rs
+++ b/library/core/src/range.rs
@@ -192,7 +192,7 @@ impl<T> IntoBounds<T> for Range<T> {
 }
 
 #[unstable(feature = "new_range_api", issue = "125687")]
-#[rustc_const_unstable(feature = "const_index", issue = "143775")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T> const From<Range<T>> for legacy::Range<T> {
     #[inline]
     fn from(value: Range<T>) -> Self {
@@ -201,7 +201,7 @@ impl<T> const From<Range<T>> for legacy::Range<T> {
 }
 
 #[unstable(feature = "new_range_api", issue = "125687")]
-#[rustc_const_unstable(feature = "const_index", issue = "143775")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T> const From<legacy::Range<T>> for Range<T> {
     #[inline]
     fn from(value: legacy::Range<T>) -> Self {
@@ -377,7 +377,7 @@ impl<T> IntoBounds<T> for RangeInclusive<T> {
 }
 
 #[unstable(feature = "new_range_api", issue = "125687")]
-#[rustc_const_unstable(feature = "const_index", issue = "143775")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl<T> const From<RangeInclusive<T>> for legacy::RangeInclusive<T> {
     #[inline]
     fn from(value: RangeInclusive<T>) -> Self {
@@ -385,7 +385,8 @@ impl<T> const From<RangeInclusive<T>> for legacy::RangeInclusive<T> {
     }
 }
 #[unstable(feature = "new_range_api", issue = "125687")]
-impl<T> From<legacy::RangeInclusive<T>> for RangeInclusive<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T> const From<legacy::RangeInclusive<T>> for RangeInclusive<T> {
     #[inline]
     fn from(value: legacy::RangeInclusive<T>) -> Self {
         assert!(
diff --git a/library/core/src/result.rs b/library/core/src/result.rs
index 6148bdb866a..7dffab9b316 100644
--- a/library/core/src/result.rs
+++ b/library/core/src/result.rs
@@ -1034,11 +1034,12 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "inner_deref", since = "1.47.0")]
-    pub fn as_deref(&self) -> Result<&T::Target, &E>
+    #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+    pub const fn as_deref(&self) -> Result<&T::Target, &E>
     where
-        T: Deref,
+        T: [const] Deref,
     {
-        self.as_ref().map(|t| t.deref())
+        self.as_ref().map(Deref::deref)
     }
 
     /// Converts from `Result<T, E>` (or `&mut Result<T, E>`) to `Result<&mut <T as DerefMut>::Target, &mut E>`.
@@ -1061,11 +1062,12 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "inner_deref", since = "1.47.0")]
-    pub fn as_deref_mut(&mut self) -> Result<&mut T::Target, &mut E>
+    #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+    pub const fn as_deref_mut(&mut self) -> Result<&mut T::Target, &mut E>
     where
-        T: DerefMut,
+        T: [const] DerefMut,
     {
-        self.as_mut().map(|t| t.deref_mut())
+        self.as_mut().map(DerefMut::deref_mut)
     }
 
     /////////////////////////////////////////////////////////////////////////
@@ -1347,7 +1349,7 @@ impl<T, E> Result<T, E> {
     #[unstable(feature = "unwrap_infallible", reason = "newly added", issue = "61695")]
     #[inline]
     #[rustc_allow_const_fn_unstable(const_precise_live_drops)]
-    #[rustc_const_unstable(feature = "const_try", issue = "74935")]
+    #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
     pub const fn into_ok(self) -> T
     where
         E: [const] Into<!>,
@@ -1384,7 +1386,7 @@ impl<T, E> Result<T, E> {
     #[unstable(feature = "unwrap_infallible", reason = "newly added", issue = "61695")]
     #[inline]
     #[rustc_allow_const_fn_unstable(const_precise_live_drops)]
-    #[rustc_const_unstable(feature = "const_try", issue = "74935")]
+    #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
     pub const fn into_err(self) -> E
     where
         T: [const] Into<!>,
diff --git a/library/core/src/str/mod.rs b/library/core/src/str/mod.rs
index 1a055a0a5ad..005793a6635 100644
--- a/library/core/src/str/mod.rs
+++ b/library/core/src/str/mod.rs
@@ -3078,7 +3078,8 @@ impl str {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl AsRef<[u8]> for str {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const AsRef<[u8]> for str {
     #[inline]
     fn as_ref(&self) -> &[u8] {
         self.as_bytes()
diff --git a/library/core/src/str/traits.rs b/library/core/src/str/traits.rs
index dc88f35eca7..971c8e829c6 100644
--- a/library/core/src/str/traits.rs
+++ b/library/core/src/str/traits.rs
@@ -826,7 +826,7 @@ unsafe impl const SliceIndex<str> for ops::RangeToInclusive<usize> {
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 #[const_trait]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 pub trait FromStr: Sized {
     /// The associated error which can be returned from parsing.
     #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/library/core/src/sync/atomic.rs b/library/core/src/sync/atomic.rs
index 44a6895f90a..d4d72c11170 100644
--- a/library/core/src/sync/atomic.rs
+++ b/library/core/src/sync/atomic.rs
@@ -2523,7 +2523,7 @@ impl<T> AtomicPtr<T> {
 
 #[cfg(target_has_atomic_load_store = "8")]
 #[stable(feature = "atomic_bool_from", since = "1.24.0")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 impl const From<bool> for AtomicBool {
     /// Converts a `bool` into an `AtomicBool`.
     ///
@@ -2542,7 +2542,8 @@ impl const From<bool> for AtomicBool {
 
 #[cfg(target_has_atomic_load_store = "ptr")]
 #[stable(feature = "atomic_from", since = "1.23.0")]
-impl<T> From<*mut T> for AtomicPtr<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T> const From<*mut T> for AtomicPtr<T> {
     /// Converts a `*mut T` into an `AtomicPtr<T>`.
     #[inline]
     fn from(p: *mut T) -> Self {
@@ -2621,7 +2622,7 @@ macro_rules! atomic_int {
         }
 
         #[$stable_from]
-        #[rustc_const_unstable(feature = "const_try", issue = "74935")]
+        #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
         impl const From<$int_type> for $atomic_type {
             #[doc = concat!("Converts an `", stringify!($int_type), "` into an `", stringify!($atomic_type), "`.")]
             #[inline]
diff --git a/library/core/src/sync/exclusive.rs b/library/core/src/sync/exclusive.rs
index 340b0b79e40..cf086bf4f50 100644
--- a/library/core/src/sync/exclusive.rs
+++ b/library/core/src/sync/exclusive.rs
@@ -163,7 +163,8 @@ impl<T: ?Sized> Exclusive<T> {
 }
 
 #[unstable(feature = "exclusive_wrapper", issue = "98407")]
-impl<T> From<T> for Exclusive<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T> const From<T> for Exclusive<T> {
     #[inline]
     fn from(t: T) -> Self {
         Self::new(t)
diff --git a/library/core/src/task/poll.rs b/library/core/src/task/poll.rs
index 59ffe7ad49c..380abac0ae9 100644
--- a/library/core/src/task/poll.rs
+++ b/library/core/src/task/poll.rs
@@ -215,7 +215,8 @@ impl<T, E> Poll<Option<Result<T, E>>> {
 }
 
 #[stable(feature = "futures_api", since = "1.36.0")]
-impl<T> From<T> for Poll<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T> const From<T> for Poll<T> {
     /// Moves the value into a [`Poll::Ready`] to make a `Poll<T>`.
     ///
     /// # Example
diff --git a/library/core/src/task/wake.rs b/library/core/src/task/wake.rs
index bb7efe582f7..97eb9ec7dc5 100644
--- a/library/core/src/task/wake.rs
+++ b/library/core/src/task/wake.rs
@@ -901,7 +901,8 @@ impl Clone for LocalWaker {
 }
 
 #[unstable(feature = "local_waker", issue = "118959")]
-impl AsRef<LocalWaker> for Waker {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const AsRef<LocalWaker> for Waker {
     fn as_ref(&self) -> &LocalWaker {
         // SAFETY: LocalWaker is just Waker without thread safety
         unsafe { transmute(self) }
diff --git a/library/core/src/tuple.rs b/library/core/src/tuple.rs
index 23a0a6877df..2cdee1803a9 100644
--- a/library/core/src/tuple.rs
+++ b/library/core/src/tuple.rs
@@ -133,6 +133,7 @@ macro_rules! tuple_impls {
         maybe_tuple_doc! {
             $($T)+ @
             #[stable(feature = "array_tuple_conv", since = "1.71.0")]
+            // can't do const From due to https://github.com/rust-lang/rust/issues/144280
             impl<T> From<[T; ${count($T)}]> for ($(${ignore($T)} T,)+) {
                 #[inline]
                 #[allow(non_snake_case)]
@@ -146,6 +147,7 @@ macro_rules! tuple_impls {
         maybe_tuple_doc! {
             $($T)+ @
             #[stable(feature = "array_tuple_conv", since = "1.71.0")]
+            // can't do const From due to https://github.com/rust-lang/rust/issues/144280
             impl<T> From<($(${ignore($T)} T,)+)> for [T; ${count($T)}] {
                 #[inline]
                 #[allow(non_snake_case)]
diff --git a/library/coretests/tests/lib.rs b/library/coretests/tests/lib.rs
index b9b768f29d7..8e197e33ba6 100644
--- a/library/coretests/tests/lib.rs
+++ b/library/coretests/tests/lib.rs
@@ -15,10 +15,9 @@
 #![feature(cfg_target_has_reliable_f16_f128)]
 #![feature(char_max_len)]
 #![feature(clone_to_uninit)]
-#![feature(const_deref)]
+#![feature(const_convert)]
 #![feature(const_destruct)]
 #![feature(const_eval_select)]
-#![feature(const_from)]
 #![feature(const_ops)]
 #![feature(const_option_ops)]
 #![feature(const_ref_cell)]
diff --git a/library/std/src/ffi/os_str.rs b/library/std/src/ffi/os_str.rs
index 1214490caad..a39565d2159 100644
--- a/library/std/src/ffi/os_str.rs
+++ b/library/std/src/ffi/os_str.rs
@@ -828,7 +828,8 @@ impl OsStr {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn new<S: AsRef<OsStr> + ?Sized>(s: &S) -> &OsStr {
+    #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+    pub const fn new<S: [const] AsRef<OsStr> + ?Sized>(s: &S) -> &OsStr {
         s.as_ref()
     }
 
@@ -876,14 +877,16 @@ impl OsStr {
     }
 
     #[inline]
-    fn from_inner(inner: &Slice) -> &OsStr {
+    #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+    const fn from_inner(inner: &Slice) -> &OsStr {
         // SAFETY: OsStr is just a wrapper of Slice,
         // therefore converting &Slice to &OsStr is safe.
         unsafe { &*(inner as *const Slice as *const OsStr) }
     }
 
     #[inline]
-    fn from_inner_mut(inner: &mut Slice) -> &mut OsStr {
+    #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+    const fn from_inner_mut(inner: &mut Slice) -> &mut OsStr {
         // SAFETY: OsStr is just a wrapper of Slice,
         // therefore converting &mut Slice to &mut OsStr is safe.
         // Any method that mutates OsStr must be careful not to
@@ -1681,7 +1684,8 @@ impl ToOwned for OsStr {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl AsRef<OsStr> for OsStr {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const AsRef<OsStr> for OsStr {
     #[inline]
     fn as_ref(&self) -> &OsStr {
         self
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index 30a1b108817..a2f7701a5b3 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -334,6 +334,7 @@
 #![feature(char_internals)]
 #![feature(clone_to_uninit)]
 #![feature(const_cmp)]
+#![feature(const_convert)]
 #![feature(const_ops)]
 #![feature(const_option_ops)]
 #![feature(const_try)]
diff --git a/library/std/src/path.rs b/library/std/src/path.rs
index 470d300d2d9..5ccea1c972c 100644
--- a/library/std/src/path.rs
+++ b/library/std/src/path.rs
@@ -2264,11 +2264,13 @@ impl Path {
     /// assert_eq!(from_string, from_path);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn new<S: AsRef<OsStr> + ?Sized>(s: &S) -> &Path {
+    #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+    pub const fn new<S: [const] AsRef<OsStr> + ?Sized>(s: &S) -> &Path {
         unsafe { &*(s.as_ref() as *const OsStr as *const Path) }
     }
 
-    fn from_inner_mut(inner: &mut OsStr) -> &mut Path {
+    #[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+    const fn from_inner_mut(inner: &mut OsStr) -> &mut Path {
         // SAFETY: Path is just a wrapper around OsStr,
         // therefore converting &mut OsStr to &mut Path is safe.
         unsafe { &mut *(inner as *mut OsStr as *mut Path) }
@@ -3337,7 +3339,8 @@ unsafe impl CloneToUninit for Path {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl AsRef<OsStr> for Path {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const AsRef<OsStr> for Path {
     #[inline]
     fn as_ref(&self) -> &OsStr {
         &self.inner
@@ -3507,7 +3510,8 @@ impl Ord for Path {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl AsRef<Path> for Path {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const AsRef<Path> for Path {
     #[inline]
     fn as_ref(&self) -> &Path {
         self
@@ -3515,7 +3519,8 @@ impl AsRef<Path> for Path {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl AsRef<Path> for OsStr {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl const AsRef<Path> for OsStr {
     #[inline]
     fn as_ref(&self) -> &Path {
         Path::new(self)
diff --git a/tests/ui/traits/const-traits/enforce-deref-on-adjust.rs b/tests/ui/traits/const-traits/enforce-deref-on-adjust.rs
index d5240b7e18d..cba207f0953 100644
--- a/tests/ui/traits/const-traits/enforce-deref-on-adjust.rs
+++ b/tests/ui/traits/const-traits/enforce-deref-on-adjust.rs
@@ -1,6 +1,6 @@
 //@ check-pass
 
-#![feature(const_deref)]
+#![feature(const_convert)]
 #![feature(const_trait_impl)]
 
 use std::ops::Deref;
diff --git a/tests/ui/traits/const-traits/non-const-op-in-closure-in-const.rs b/tests/ui/traits/const-traits/non-const-op-in-closure-in-const.rs
index d5f80acc15b..50c985096d1 100644
--- a/tests/ui/traits/const-traits/non-const-op-in-closure-in-const.rs
+++ b/tests/ui/traits/const-traits/non-const-op-in-closure-in-const.rs
@@ -1,4 +1,4 @@
-#![feature(const_trait_impl, const_from)]
+#![feature(const_trait_impl, const_convert)]
 
 //@ check-pass
 
diff --git a/tests/ui/traits/const-traits/reservation-impl-ice.rs b/tests/ui/traits/const-traits/reservation-impl-ice.rs
index efaea1cc6b2..7fefb4ec543 100644
--- a/tests/ui/traits/const-traits/reservation-impl-ice.rs
+++ b/tests/ui/traits/const-traits/reservation-impl-ice.rs
@@ -1,5 +1,5 @@
 //@ compile-flags: -Znext-solver
-#![feature(const_from, never_type, const_trait_impl)]
+#![feature(const_convert, never_type, const_trait_impl)]
 
 const fn impls_from<T: ~const From<!>>() {}