rust-clippy/clippy_lints/src/unused_self.rs

104 lines
3.4 KiB
Rust
Raw Normal View History

2019-10-03 19:09:32 +00:00
use if_chain::if_chain;
2019-12-03 23:16:03 +00:00
use rustc::declare_lint_pass;
2019-10-03 19:09:32 +00:00
use rustc::hir::def::Res;
use rustc::hir::intravisit::{walk_path, NestedVisitorMap, Visitor};
use rustc::hir::{AssocItemKind, HirId, ImplItemKind, ImplItemRef, Item, ItemKind, Path};
use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
2019-12-03 23:16:03 +00:00
use rustc_session::declare_tool_lint;
2019-10-03 19:09:32 +00:00
use crate::utils::span_help_and_lint;
declare_clippy_lint! {
/// **What it does:** Checks methods that contain a `self` argument but don't use it
///
/// **Why is this bad?** It may be clearer to define the method as an associated function instead
2019-10-03 19:09:32 +00:00
/// of an instance method if it doesn't require `self`.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust,ignore
/// struct A;
/// impl A {
/// fn method(&self) {}
/// }
/// ```
///
/// Could be written:
///
/// ```rust,ignore
/// struct A;
/// impl A {
/// fn method() {}
/// }
/// ```
pub UNUSED_SELF,
2019-10-04 17:18:52 +00:00
pedantic,
2019-10-03 19:09:32 +00:00
"methods that contain a `self` argument but don't use it"
}
declare_lint_pass!(UnusedSelf => [UNUSED_SELF]);
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedSelf {
fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &Item) {
if item.span.from_expansion() {
return;
}
if let ItemKind::Impl(_, _, _, _, None, _, ref impl_item_refs) = item.kind {
for impl_item_ref in impl_item_refs {
if_chain! {
if let ImplItemRef {
kind: AssocItemKind::Method { has_self: true },
..
} = impl_item_ref;
let impl_item = cx.tcx.hir().impl_item(impl_item_ref.id);
if let ImplItemKind::Method(_, body_id) = &impl_item.kind;
then {
let body = cx.tcx.hir().body(*body_id);
let self_param = &body.params[0];
let self_hir_id = self_param.pat.hir_id;
2019-10-04 17:18:52 +00:00
let mut visitor = UnusedSelfVisitor {
2019-10-03 19:09:32 +00:00
cx,
uses_self: false,
self_hir_id: &self_hir_id,
};
visitor.visit_body(body);
if !visitor.uses_self {
span_help_and_lint(
cx,
UNUSED_SELF,
self_param.span,
"unused `self` argument",
"consider refactoring to a associated function",
2019-10-03 19:09:32 +00:00
)
}
}
}
}
};
}
}
struct UnusedSelfVisitor<'a, 'tcx> {
cx: &'a LateContext<'a, 'tcx>,
uses_self: bool,
self_hir_id: &'a HirId,
}
impl<'a, 'tcx> Visitor<'tcx> for UnusedSelfVisitor<'a, 'tcx> {
fn visit_path(&mut self, path: &'tcx Path, _id: HirId) {
if self.uses_self {
// This function already uses `self`
return;
}
if let Res::Local(hir_id) = &path.res {
self.uses_self = self.self_hir_id == hir_id
}
walk_path(self, path);
}
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2019-10-06 18:12:07 +00:00
NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())
2019-10-03 19:09:32 +00:00
}
}