95 lines
3.0 KiB
Rust
95 lines
3.0 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_help;
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use clippy_utils::macros::root_macro_call_first_node;
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use clippy_utils::visitors::is_local_used;
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use rustc_hir::{Body, Impl, ImplItem, ImplItemKind, ItemKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::impl_lint_pass;
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use std::ops::ControlFlow;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks methods that contain a `self` argument but don't use it
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///
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/// ### Why is this bad?
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/// 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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/// ### 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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#[clippy::version = "1.40.0"]
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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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pub struct UnusedSelf {
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avoid_breaking_exported_api: bool,
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}
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impl_lint_pass!(UnusedSelf => [UNUSED_SELF]);
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impl UnusedSelf {
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pub fn new(avoid_breaking_exported_api: bool) -> Self {
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Self {
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avoid_breaking_exported_api,
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}
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}
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}
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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()).def_id;
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let parent_item = cx.tcx.hir().expect_item(parent);
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let assoc_item = cx.tcx.associated_item(impl_item.owner_id);
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let contains_todo = |cx, body: &'_ Body<'_>| -> bool {
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clippy_utils::visitors::for_each_expr(body.value, |e| {
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if let Some(macro_call) = root_macro_call_first_node(cx, e) {
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if cx.tcx.item_name(macro_call.def_id).as_str() == "todo" {
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ControlFlow::Break(())
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} else {
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ControlFlow::Continue(())
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}
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} else {
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ControlFlow::Continue(())
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}
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})
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.is_some()
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};
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if let ItemKind::Impl(Impl { of_trait: None, .. }) = parent_item.kind
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&& assoc_item.fn_has_self_parameter
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&& let ImplItemKind::Fn(.., body_id) = &impl_item.kind
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&& (!cx.effective_visibilities.is_exported(impl_item.owner_id.def_id) || !self.avoid_breaking_exported_api)
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&& let body = cx.tcx.hir().body(*body_id)
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&& let [self_param, ..] = body.params
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&& !is_local_used(cx, body, self_param.pat.hir_id)
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&& !contains_todo(cx, body)
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{
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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 an associated function",
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);
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}
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}
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}
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