Use autoharness for char::convert::from_u32_unchecked

Author: tautschnig

.github/workflows/kani.yml

@@ -81,6 +81,7 @@ jobs:
           scripts/run-kani.sh --run autoharness --kani-args \
             --include-pattern alloc::layout::Layout::from_size_align \
             --include-pattern ascii::ascii_char::AsciiChar::from_u8 \
+            --include-pattern char::convert::from_u32_unchecked \
             --include-pattern ptr::align_offset::mod_inv \
             --include-pattern ptr::alignment::Alignment::as_nonzero \
             --include-pattern ptr::alignment::Alignment::as_usize \

library/core/src/char/convert.rs

@@ -288,15 +288,3 @@ pub(super) const fn from_digit(num: u32, radix: u32) -> Option<char> {
         None
     }
 }
-
-#[cfg(kani)]
-#[unstable(feature = "kani", issue = "none")]
-mod verify {
-    use super::*;
-
-    #[kani::proof_for_contract(from_u32_unchecked)]
-    fn check_from_u32_unchecked() {
-        let i: u32 = kani::any();
-        unsafe { from_u32_unchecked(i) };
-    }
-}