Update remap_mir_for_const_eval_select

src/mir.rs

@@ -77,8 +77,9 @@ fn remap_mir_for_const_eval_select<'tcx>(
             } if let ty::FnDef(def_id, _) = *const_.ty().kind()
                 && tcx.is_intrinsic(def_id, sym::const_eval_select) =>
             {
-                let [tupled_args, called_in_const, called_at_rt]: [_; 3] =
-                    std::mem::take(args).try_into().unwrap();
+                let Ok([tupled_args, called_in_const, called_at_rt]) = take_array(args) else {
+                    unreachable!()
+                };
                 let ty = tupled_args.node.ty(&body.local_decls, tcx);
                 let fields = ty.tuple_fields();
                 let num_args = fields.len();
@@ -137,6 +138,11 @@ fn remap_mir_for_const_eval_select<'tcx>(
     body
 }
 
+fn take_array<T, const N: usize>(b: &mut Box<[T]>) -> Result<[T; N], Box<[T]>> {
+    let b: Box<[T; N]> = std::mem::take(b).try_into()?;
+    Ok(*b)
+}
+
 memoize!(
     pub fn analysis_mir<'tcx>(cx: &AnalysisCtxt<'tcx>, def_id: DefId) -> &'tcx Body<'tcx> {
         if let Some(local_def_id) = def_id.as_local() {