106 lines
3.3 KiB
Rust
106 lines
3.3 KiB
Rust
use if_chain::if_chain;
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use rustc_hir::def::Res;
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use rustc_hir::intravisit::{walk_path, NestedVisitorMap, Visitor};
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use rustc_hir::{HirId, Impl, ImplItem, ImplItemKind, ItemKind, Path};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::hir::map::Map;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use crate::utils::span_lint_and_help;
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declare_clippy_lint! {
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/// **What it does:** Checks methods that contain a `self` argument but don't use it
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///
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/// **Why is this bad?** It may be clearer to define the method as an associated function instead
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/// of an instance method if it doesn't require `self`.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust,ignore
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/// struct A;
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/// impl A {
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/// fn method(&self) {}
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/// }
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/// ```
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///
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/// Could be written:
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///
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/// ```rust,ignore
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/// struct A;
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/// impl A {
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/// fn method() {}
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/// }
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/// ```
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pub UNUSED_SELF,
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pedantic,
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"methods that contain a `self` argument but don't use it"
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}
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declare_lint_pass!(UnusedSelf => [UNUSED_SELF]);
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impl<'tcx> LateLintPass<'tcx> for UnusedSelf {
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fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &ImplItem<'_>) {
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if impl_item.span.from_expansion() {
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return;
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}
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let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id);
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let parent_item = cx.tcx.hir().expect_item(parent);
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let def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
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let assoc_item = cx.tcx.associated_item(def_id);
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if_chain! {
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if let ItemKind::Impl(Impl { of_trait: None, .. }) = parent_item.kind;
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if assoc_item.fn_has_self_parameter;
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if let ImplItemKind::Fn(.., body_id) = &impl_item.kind;
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let body = cx.tcx.hir().body(*body_id);
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if !body.params.is_empty();
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then {
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let self_param = &body.params[0];
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let self_hir_id = self_param.pat.hir_id;
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let mut visitor = UnusedSelfVisitor {
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cx,
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uses_self: false,
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self_hir_id: &self_hir_id,
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};
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visitor.visit_body(body);
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if !visitor.uses_self {
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span_lint_and_help(
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cx,
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UNUSED_SELF,
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self_param.span,
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"unused `self` argument",
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None,
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"consider refactoring to a associated function",
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);
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return;
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}
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}
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}
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}
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}
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struct UnusedSelfVisitor<'a, 'tcx> {
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cx: &'a LateContext<'tcx>,
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uses_self: bool,
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self_hir_id: &'a HirId,
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}
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impl<'a, 'tcx> Visitor<'tcx> for UnusedSelfVisitor<'a, 'tcx> {
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type Map = Map<'tcx>;
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fn visit_path(&mut self, path: &'tcx Path<'_>, _id: HirId) {
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if self.uses_self {
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// This function already uses `self`
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return;
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}
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if let Res::Local(hir_id) = &path.res {
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self.uses_self = self.self_hir_id == hir_id
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}
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walk_path(self, path);
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}
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fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
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NestedVisitorMap::OnlyBodies(self.cx.tcx.hir())
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}
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}
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