1 use if_chain::if_chain;
2 use rustc_hir::{Impl, ImplItem, ImplItemKind, ItemKind};
3 use rustc_lint::{LateContext, LateLintPass};
4 use rustc_session::{declare_lint_pass, declare_tool_lint};
6 use crate::utils::span_lint_and_help;
7 use crate::utils::visitors::LocalUsedVisitor;
10 /// **What it does:** Checks methods that contain a `self` argument but don't use it
12 /// **Why is this bad?** It may be clearer to define the method as an associated function instead
13 /// of an instance method if it doesn't require `self`.
15 /// **Known problems:** None.
21 /// fn method(&self) {}
35 "methods that contain a `self` argument but don't use it"
38 declare_lint_pass!(UnusedSelf => [UNUSED_SELF]);
40 impl<'tcx> LateLintPass<'tcx> for UnusedSelf {
41 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &ImplItem<'_>) {
42 if impl_item.span.from_expansion() {
45 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
46 let parent_item = cx.tcx.hir().expect_item(parent);
47 let assoc_item = cx.tcx.associated_item(impl_item.def_id);
49 if let ItemKind::Impl(Impl { of_trait: None, .. }) = parent_item.kind;
50 if assoc_item.fn_has_self_parameter;
51 if let ImplItemKind::Fn(.., body_id) = &impl_item.kind;
52 let body = cx.tcx.hir().body(*body_id);
53 if !body.params.is_empty();
55 let self_param = &body.params[0];
56 let self_hir_id = self_param.pat.hir_id;
57 if !LocalUsedVisitor::new(cx, self_hir_id).check_body(body) {
62 "unused `self` argument",
64 "consider refactoring to a associated function",