1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::get_parent_expr;
3 use clippy_utils::source::snippet_with_context;
4 use clippy_utils::ty::is_type_lang_item;
5 use if_chain::if_chain;
6 use rustc_errors::Applicability;
7 use rustc_hir::{BorrowKind, Expr, ExprKind, LangItem, Mutability};
8 use rustc_lint::{LateContext, LateLintPass};
9 use rustc_session::{declare_lint_pass, declare_tool_lint};
11 declare_clippy_lint! {
13 /// Checks for redundant slicing expressions which use the full range, and
14 /// do not change the type.
16 /// ### Why is this bad?
17 /// It unnecessarily adds complexity to the expression.
19 /// ### Known problems
20 /// If the type being sliced has an implementation of `Index<RangeFull>`
21 /// that actually changes anything then it can't be removed. However, this would be surprising
22 /// to people reading the code and should have a note with it.
26 /// fn get_slice(x: &[u32]) -> &[u32] {
32 /// fn get_slice(x: &[u32]) -> &[u32] {
36 #[clippy::version = "1.51.0"]
37 pub REDUNDANT_SLICING,
39 "redundant slicing of the whole range of a type"
42 declare_lint_pass!(RedundantSlicing => [REDUNDANT_SLICING]);
44 impl<'tcx> LateLintPass<'tcx> for RedundantSlicing {
45 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
46 if expr.span.from_expansion() {
50 let ctxt = expr.span.ctxt();
52 if let ExprKind::AddrOf(BorrowKind::Ref, mutability, addressee) = expr.kind;
53 if addressee.span.ctxt() == ctxt;
54 if let ExprKind::Index(indexed, range) = addressee.kind;
55 if is_type_lang_item(cx, cx.typeck_results().expr_ty_adjusted(range), LangItem::RangeFull);
56 if cx.typeck_results().expr_ty(expr) == cx.typeck_results().expr_ty(indexed);
58 let mut app = Applicability::MachineApplicable;
59 let snip = snippet_with_context(cx, indexed.span, ctxt, "..", &mut app).0;
61 let (reborrow_str, help_str) = if mutability == Mutability::Mut {
62 // The slice was used to reborrow the mutable reference.
63 ("&mut *", "reborrow the original value instead")
65 get_parent_expr(cx, expr),
67 kind: ExprKind::AddrOf(BorrowKind::Ref, Mutability::Mut, _),
71 // The slice was used to make a temporary reference.
72 ("&*", "reborrow the original value instead")
74 ("", "use the original value instead")
81 "redundant slicing of the whole range",
83 format!("{}{}", reborrow_str, snip),