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