1 use clippy_utils::source::snippet_with_applicability;
2 use clippy_utils::ty::is_type_lang_item;
3 use if_chain::if_chain;
4 use rustc_errors::Applicability;
5 use rustc_hir::{Expr, ExprKind, LangItem};
6 use rustc_lint::{LateContext, LateLintPass, LintContext};
7 use rustc_middle::{lint::in_external_macro, ty::TyS};
8 use rustc_session::{declare_lint_pass, declare_tool_lint};
10 use crate::utils::span_lint_and_sugg;
12 declare_clippy_lint! {
13 /// **What it does:** Checks for redundant slicing expressions which use the full range, and
14 /// do not change the type.
16 /// **Why is this bad?** It unnecessarily adds complexity to the expression.
18 /// **Known problems:** If the type being sliced has an implementation of `Index<RangeFull>`
19 /// that actually changes anything then it can't be removed. However, this would be surprising
20 /// to people reading the code and should have a note with it.
25 /// fn get_slice(x: &[u32]) -> &[u32] {
31 /// fn get_slice(x: &[u32]) -> &[u32] {
35 pub REDUNDANT_SLICING,
37 "redundant slicing of the whole range of a type"
40 declare_lint_pass!(RedundantSlicing => [REDUNDANT_SLICING]);
42 impl LateLintPass<'_> for RedundantSlicing {
43 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
44 if in_external_macro(cx.sess(), expr.span) {
49 if let ExprKind::AddrOf(_, _, addressee) = expr.kind;
50 if let ExprKind::Index(indexed, range) = addressee.kind;
51 if is_type_lang_item(cx, cx.typeck_results().expr_ty_adjusted(range), LangItem::RangeFull);
52 if TyS::same_type(cx.typeck_results().expr_ty(expr), cx.typeck_results().expr_ty(indexed));
54 let mut app = Applicability::MachineApplicable;
55 let hint = snippet_with_applicability(cx, indexed.span, "..", &mut app).into_owned();
61 "redundant slicing of the whole range",
62 "use the original slice instead",