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op_ref.rs
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use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::get_enclosing_block;
use clippy_utils::source::snippet;
use clippy_utils::ty::{implements_trait, is_copy};
use rustc_errors::Applicability;
use rustc_hir::def::Res;
use rustc_hir::def_id::DefId;
use rustc_hir::{BinOpKind, BorrowKind, Expr, ExprKind, GenericArg, ItemKind, QPath, TyKind};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
use super::OP_REF;
#[expect(clippy::too_many_lines)]
pub(crate) fn check<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
op: BinOpKind,
left: &'tcx Expr<'_>,
right: &'tcx Expr<'_>,
) {
let (trait_id, requires_ref) = match op {
BinOpKind::Add => (cx.tcx.lang_items().add_trait(), false),
BinOpKind::Sub => (cx.tcx.lang_items().sub_trait(), false),
BinOpKind::Mul => (cx.tcx.lang_items().mul_trait(), false),
BinOpKind::Div => (cx.tcx.lang_items().div_trait(), false),
BinOpKind::Rem => (cx.tcx.lang_items().rem_trait(), false),
// don't lint short circuiting ops
BinOpKind::And | BinOpKind::Or => return,
BinOpKind::BitXor => (cx.tcx.lang_items().bitxor_trait(), false),
BinOpKind::BitAnd => (cx.tcx.lang_items().bitand_trait(), false),
BinOpKind::BitOr => (cx.tcx.lang_items().bitor_trait(), false),
BinOpKind::Shl => (cx.tcx.lang_items().shl_trait(), false),
BinOpKind::Shr => (cx.tcx.lang_items().shr_trait(), false),
BinOpKind::Ne | BinOpKind::Eq => (cx.tcx.lang_items().eq_trait(), true),
BinOpKind::Lt | BinOpKind::Le | BinOpKind::Ge | BinOpKind::Gt => {
(cx.tcx.lang_items().partial_ord_trait(), true)
},
};
if let Some(trait_id) = trait_id {
match (&left.kind, &right.kind) {
// do not suggest to dereference literals
(&ExprKind::Lit(..), _) | (_, &ExprKind::Lit(..)) => {},
// &foo == &bar
(&ExprKind::AddrOf(BorrowKind::Ref, _, l), &ExprKind::AddrOf(BorrowKind::Ref, _, r)) => {
let lty = cx.typeck_results().expr_ty(l);
let rty = cx.typeck_results().expr_ty(r);
let lcpy = is_copy(cx, lty);
let rcpy = is_copy(cx, rty);
if let Some((self_ty, other_ty)) = in_impl(cx, e, trait_id)
&& ((are_equal(cx, rty, self_ty) && are_equal(cx, lty, other_ty))
|| (are_equal(cx, rty, other_ty) && are_equal(cx, lty, self_ty)))
{
return; // Don't lint
}
// either operator autorefs or both args are copyable
if (requires_ref || (lcpy && rcpy)) && implements_trait(cx, lty, trait_id, &[rty.into()]) {
span_lint_and_then(
cx,
OP_REF,
e.span,
"needlessly taken reference of both operands",
|diag| {
let lsnip = snippet(cx, l.span, "...").to_string();
let rsnip = snippet(cx, r.span, "...").to_string();
diag.multipart_suggestion(
"use the values directly",
vec![(left.span, lsnip), (right.span, rsnip)],
Applicability::MachineApplicable,
);
},
);
} else if lcpy
&& !rcpy
&& implements_trait(cx, lty, trait_id, &[cx.typeck_results().expr_ty(right).into()])
{
span_lint_and_then(
cx,
OP_REF,
e.span,
"needlessly taken reference of left operand",
|diag| {
let lsnip = snippet(cx, l.span, "...").to_string();
diag.span_suggestion(
left.span,
"use the left value directly",
lsnip,
Applicability::MachineApplicable,
);
},
);
} else if !lcpy
&& rcpy
&& implements_trait(cx, cx.typeck_results().expr_ty(left), trait_id, &[rty.into()])
{
span_lint_and_then(
cx,
OP_REF,
e.span,
"needlessly taken reference of right operand",
|diag| {
let rsnip = snippet(cx, r.span, "...").to_string();
diag.span_suggestion(
right.span,
"use the right value directly",
rsnip,
Applicability::MachineApplicable,
);
},
);
}
},
// &foo == bar
(&ExprKind::AddrOf(BorrowKind::Ref, _, l), _) => {
let lty = cx.typeck_results().expr_ty(l);
if let Some((self_ty, other_ty)) = in_impl(cx, e, trait_id) {
let rty = cx.typeck_results().expr_ty(right);
if (are_equal(cx, rty, self_ty) && are_equal(cx, lty, other_ty))
|| (are_equal(cx, rty, other_ty) && are_equal(cx, lty, self_ty))
{
return; // Don't lint
}
}
let lcpy = is_copy(cx, lty);
if (requires_ref || lcpy)
&& implements_trait(cx, lty, trait_id, &[cx.typeck_results().expr_ty(right).into()])
{
span_lint_and_then(
cx,
OP_REF,
e.span,
"needlessly taken reference of left operand",
|diag| {
let lsnip = snippet(cx, l.span, "...").to_string();
diag.span_suggestion(
left.span,
"use the left value directly",
lsnip,
Applicability::MachineApplicable,
);
},
);
}
},
// foo == &bar
(_, &ExprKind::AddrOf(BorrowKind::Ref, _, r)) => {
let rty = cx.typeck_results().expr_ty(r);
if let Some((self_ty, other_ty)) = in_impl(cx, e, trait_id) {
let lty = cx.typeck_results().expr_ty(left);
if (are_equal(cx, rty, self_ty) && are_equal(cx, lty, other_ty))
|| (are_equal(cx, rty, other_ty) && are_equal(cx, lty, self_ty))
{
return; // Don't lint
}
}
let rcpy = is_copy(cx, rty);
if (requires_ref || rcpy)
&& implements_trait(cx, cx.typeck_results().expr_ty(left), trait_id, &[rty.into()])
{
span_lint_and_then(cx, OP_REF, e.span, "taken reference of right operand", |diag| {
let rsnip = snippet(cx, r.span, "...").to_string();
diag.span_suggestion(
right.span,
"use the right value directly",
rsnip,
Applicability::MachineApplicable,
);
});
}
},
_ => {},
}
}
}
fn in_impl<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
bin_op: DefId,
) -> Option<(&'tcx rustc_hir::Ty<'tcx>, &'tcx rustc_hir::Ty<'tcx>)> {
if let Some(block) = get_enclosing_block(cx, e.hir_id)
&& let Some(impl_def_id) = cx.tcx.impl_of_method(block.hir_id.owner.to_def_id())
&& let item = cx.tcx.hir_expect_item(impl_def_id.expect_local())
&& let ItemKind::Impl(item) = &item.kind
&& let Some(of_trait) = &item.of_trait
&& let Some(seg) = of_trait.path.segments.last()
&& let Res::Def(_, trait_id) = seg.res
&& trait_id == bin_op
&& let Some(generic_args) = seg.args
&& let Some(GenericArg::Type(other_ty)) = generic_args.args.last()
{
// `_` is not permitted in impl headers
Some((item.self_ty, other_ty.as_unambig_ty()))
} else {
None
}
}
fn are_equal(cx: &LateContext<'_>, middle_ty: Ty<'_>, hir_ty: &rustc_hir::Ty<'_>) -> bool {
if let ty::Adt(adt_def, _) = middle_ty.kind()
&& let Some(local_did) = adt_def.did().as_local()
&& let item = cx.tcx.hir_expect_item(local_did)
&& let middle_ty_id = item.owner_id.to_def_id()
&& let TyKind::Path(QPath::Resolved(_, path)) = hir_ty.kind
&& let Res::Def(_, hir_ty_id) = path.res
{
hir_ty_id == middle_ty_id
} else {
false
}
}