Revert "Auto merge of #89450 - usbalbin:const_try_revert, r=oli-obk"

This reverts commit a8387aef8c378a771686878062e544af4d5e2245, reversing
changes made to 6e1211081239be62a5d0bb3bbcb29a9f14621c81.

4 files changed, 13 insertions, 5 deletions

diff --git a/library/core/src/convert/mod.rs b/library/core/src/convert/mod.rs
index 5aa53deee34..1c2e673d604 100644
--- a/library/core/src/convert/mod.rs
+++ b/library/core/src/convert/mod.rs
@@ -534,9 +534,10 @@ where
 
 // From implies Into
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T, U> Into<U> for T
+#[rustc_const_unstable(feature = "const_convert", issue = "88674")]
+impl<T, U> const Into<U> for T
 where
-    U: From<T>,
+    U: ~const From<T>,
 {
     fn into(self) -> U {
         U::from(self)
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index d9a40a9b2ec..04996368064 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -112,6 +112,7 @@
 #![feature(const_float_classify)]
 #![feature(const_fmt_arguments_new)]
 #![feature(const_heap)]
+#![feature(const_convert)]
 #![feature(const_inherent_unchecked_arith)]
 #![feature(const_int_unchecked_arith)]
 #![feature(const_intrinsic_copy)]
diff --git a/library/core/src/option.rs b/library/core/src/option.rs
index a6e7257448c..381e2d6eed3 100644
--- a/library/core/src/option.rs
+++ b/library/core/src/option.rs
@@ -2077,7 +2077,8 @@ impl<A, V: FromIterator<A>> FromIterator<Option<A>> for Option<V> {
 }
 
 #[unstable(feature = "try_trait_v2", issue = "84277")]
-impl<T> ops::Try for Option<T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "88674")]
+impl<T> const ops::Try for Option<T> {
     type Output = T;
     type Residual = Option<convert::Infallible>;
 
@@ -2096,6 +2097,7 @@ impl<T> ops::Try for Option<T> {
 }
 
 #[unstable(feature = "try_trait_v2", issue = "84277")]
+#[rustc_const_unstable(feature = "const_convert", issue = "88674")]
 impl<T> const ops::FromResidual for Option<T> {
     #[inline]
     fn from_residual(residual: Option<convert::Infallible>) -> Self {
diff --git a/library/core/src/result.rs b/library/core/src/result.rs
index ab067d57d08..8ef5ffb962b 100644
--- a/library/core/src/result.rs
+++ b/library/core/src/result.rs
@@ -1945,7 +1945,8 @@ impl<A, E, V: FromIterator<A>> FromIterator<Result<A, E>> for Result<V, E> {
 }
 
 #[unstable(feature = "try_trait_v2", issue = "84277")]
-impl<T, E> ops::Try for Result<T, E> {
+#[rustc_const_unstable(feature = "const_convert", issue = "88674")]
+impl<T, E> const ops::Try for Result<T, E> {
     type Output = T;
     type Residual = Result<convert::Infallible, E>;
 
@@ -1964,7 +1965,10 @@ impl<T, E> ops::Try for Result<T, E> {
 }
 
 #[unstable(feature = "try_trait_v2", issue = "84277")]
-impl<T, E, F: From<E>> ops::FromResidual<Result<convert::Infallible, E>> for Result<T, F> {
+#[rustc_const_unstable(feature = "const_convert", issue = "88674")]
+impl<T, E, F: ~const From<E>> const ops::FromResidual<Result<convert::Infallible, E>>
+    for Result<T, F>
+{
     #[inline]
     fn from_residual(residual: Result<convert::Infallible, E>) -> Self {
         match residual {