constify result unwrap unchecked

Author: bend-n

library/core/src/result.rs

@@ -1646,11 +1646,15 @@ impl<T, E> Result<T, E> {
     #[inline]
     #[track_caller]
     #[stable(feature = "option_result_unwrap_unchecked", since = "1.58.0")]
-    pub unsafe fn unwrap_unchecked(self) -> T {
+    #[rustc_const_unstable(feature = "const_result_unwrap_unchecked", issue = "none")]
+    pub const unsafe fn unwrap_unchecked(self) -> T {
         match self {
             Ok(t) => t,
-            // SAFETY: the safety contract must be upheld by the caller.
-            Err(_) => unsafe { hint::unreachable_unchecked() },
+            Err(e) => {
+                super::mem::forget(e);
+                // SAFETY: the safety contract must be upheld by the caller.
+                unsafe { hint::unreachable_unchecked() }
+            }
         }
     }