Fixed issue with usage of generics and moved feature gate to crate root

Author: madhav-madhusoodanan

library/core/src/lib.rs

@@ -141,6 +141,7 @@
 #![feature(unchecked_shifts)]
 #![feature(utf16_extra)]
 #![feature(variant_count)]
+#![feature(control_flow_into_value)]
 // tidy-alphabetical-end
 //
 // Language features:

library/core/src/ops/control_flow.rs

@@ -1,4 +1,3 @@
-#![feature(control_flow_into_value)]
 use crate::{convert, ops};
 
 /// Used to tell an operation whether it should exit early or go on as usual.
@@ -242,7 +241,7 @@ impl<T> ControlFlow<T, T> {
     /// assert_eq!(ControlFlow::<i32, i32>::Continue(512).into_value(), 512);
     /// ```
     #[unstable(feature = "control_flow_into_value", issue = "137461")]
-    pub const fn into_value<T>(self) -> T {
+    pub const fn into_value(self) -> T {
         match self {
             ControlFlow::Continue(x) | ControlFlow::Break(x) => x,
         }