You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: needless_update.rs
    path of file: ./repos/rust-clippy/clippy_lints/src
    
    the code of the file until where you have to start completion: use clippy_utils::diagnostics::span_lint;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty;
use rustc_session::declare_lint_pass;

declare_clippy_lint! {
    /// ### What it does
    /// Checks for needlessly including a base struct on update
    /// when all fields are changed anyway.
    ///
    /// This lint is not applied to structs marked with
    /// [non_exhaustive](https://doc.rust-lang.org/re
    
    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
        if let ExprKind::Struct(_, fields, Some(base)) = expr.kind {
            let ty = cx.typeck_results().expr_ty(expr);
            if let ty::Adt(def, _) = ty.kind() {
                if fields.len() == def.non_enum_variant().fields.len()
                    && !def.variant(0_usize.into()).is_field_list_non_exhaustive()
                {
                    span_lint(
                        cx,
                        NEEDLESS_UPDATE,
                        base.span,
                        "struct update has no effect, all the fields in the struct have already been specified",
                    );
                }
            }
        }
    }