misc: use None in the pattern directly

this'll probably be marginally faster thanks to the equality check being
now structural

Author: ada4a

clippy_utils/src/lib.rs

@@ -1977,9 +1977,7 @@ pub fn is_expr_identity_of_pat(cx: &LateContext<'_>, pat: &Pat<'_>, expr: &Expr<
         {
             zip(pats, tup).all(|(pat, expr)| is_expr_identity_of_pat(cx, pat, expr, by_hir))
         },
-        (PatKind::Slice(before, slice, after), ExprKind::Array(arr))
-            if slice.is_none() && before.len() + after.len() == arr.len() =>
-        {
+        (PatKind::Slice(before, None, after), ExprKind::Array(arr)) if before.len() + after.len() == arr.len() => {
             zip(before.iter().chain(after), arr).all(|(pat, expr)| is_expr_identity_of_pat(cx, pat, expr, by_hir))
         },
         (PatKind::TupleStruct(pat_ident, field_pats, dotdot), ExprKind::Call(ident, fields))