Split out from_u32_unchecked from const_char_convert

It relies on the Option::unwrap function which is not const-stable (yet).

Author: est31

library/core/src/char/convert.rs

@@ -18,7 +18,6 @@ pub(super) const fn from_u32(i: u32) -> Option<char> {
 }
 
 /// Converts a `u32` to a `char`, ignoring validity. See [`char::from_u32_unchecked`].
-#[rustc_const_unstable(feature = "const_char_convert", issue = "89259")]
 #[inline]
 #[must_use]
 pub(super) const unsafe fn from_u32_unchecked(i: u32) -> char {

library/core/src/char/methods.rs

@@ -183,7 +183,7 @@ impl char {
     /// assert_eq!('❤', c);
     /// ```
     #[stable(feature = "assoc_char_funcs", since = "1.52.0")]
-    #[rustc_const_unstable(feature = "const_char_convert", issue = "89259")]
+    #[rustc_const_unstable(feature = "const_char_from_u32_unchecked", issue = "89259")]
     #[must_use]
     #[inline]
     pub const unsafe fn from_u32_unchecked(i: u32) -> char {

library/core/src/char/mod.rs

@@ -120,7 +120,7 @@ pub const fn from_u32(i: u32) -> Option<char> {
 /// Converts a `u32` to a `char`, ignoring validity. Use [`char::from_u32_unchecked`].
 /// instead.
 #[stable(feature = "char_from_unchecked", since = "1.5.0")]
-#[rustc_const_unstable(feature = "const_char_convert", issue = "89259")]
+#[rustc_const_unstable(feature = "const_char_from_u32_unchecked", issue = "89259")]
 #[must_use]
 #[inline]
 pub const unsafe fn from_u32_unchecked(i: u32) -> char {

library/core/src/lib.rs

@@ -105,6 +105,7 @@
 #![feature(const_caller_location)]
 #![feature(const_cell_into_inner)]
 #![feature(const_char_convert)]
+#![feature(const_char_from_u32_unchecked)]
 #![feature(const_clone)]
 #![feature(const_cmp)]
 #![feature(const_discriminant)]