1 use clippy_utils
::diagnostics
::span_lint_and_help
;
2 use clippy_utils
::visitors
::LocalUsedVisitor
;
3 use if_chain
::if_chain
;
4 use rustc_hir
::{Impl, ImplItem, ImplItemKind, ItemKind}
;
5 use rustc_lint
::{LateContext, LateLintPass}
;
6 use rustc_session
::{declare_lint_pass, declare_tool_lint}
;
10 /// Checks methods that contain a `self` argument but don't use it
12 /// ### Why is this bad?
13 /// It may be clearer to define the method as an associated function instead
14 /// of an instance method if it doesn't require `self`.
20 /// fn method(&self) {}
34 "methods that contain a `self` argument but don't use it"
37 declare_lint_pass
!(UnusedSelf
=> [UNUSED_SELF
]);
39 impl<'tcx
> LateLintPass
<'tcx
> for UnusedSelf
{
40 fn check_impl_item(&mut self, cx
: &LateContext
<'tcx
>, impl_item
: &ImplItem
<'_
>) {
41 if impl_item
.span
.from_expansion() {
44 let parent
= cx
.tcx
.hir().get_parent_item(impl_item
.hir_id());
45 let parent_item
= cx
.tcx
.hir().expect_item(parent
);
46 let assoc_item
= cx
.tcx
.associated_item(impl_item
.def_id
);
48 if let ItemKind
::Impl(Impl { of_trait: None, .. }
) = parent_item
.kind
;
49 if assoc_item
.fn_has_self_parameter
;
50 if let ImplItemKind
::Fn(.., body_id
) = &impl_item
.kind
;
51 let body
= cx
.tcx
.hir().body(*body_id
);
52 if let [self_param
, ..] = body
.params
;
53 let self_hir_id
= self_param
.pat
.hir_id
;
54 if !LocalUsedVisitor
::new(cx
, self_hir_id
).check_body(body
);
60 "unused `self` argument",
62 "consider refactoring to a associated function",