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op_ref: clean-up, overhaul diagnostics #15869

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b1b9667
misc: reduce indentation
ada4a Oct 12, 2025
96ada86
clean-up
ada4a Oct 12, 2025
cbe8a71
make suggestions verbose
ada4a Oct 12, 2025
5a6e664
fix: actually use the `applicability`s
ada4a Oct 12, 2025
389d4fe
only highlight the reference to remove
ada4a Oct 12, 2025
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315 changes: 173 additions & 142 deletions clippy_lints/src/operators/op_ref.rs
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Original file line number Diff line number Diff line change
@@ -1,13 +1,13 @@
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::get_enclosing_block;
use clippy_utils::source::snippet_with_context;
use clippy_utils::source::walk_span_to_context;
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_hir::{self as hir, BinOpKind, BorrowKind, Expr, ExprKind, GenericArg, ItemKind, QPath, TyKind};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
use rustc_middle::ty::Ty;

use super::OP_REF;

Expand Down Expand Up @@ -37,139 +37,146 @@ pub(crate) fn check<'tcx>(
(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 mut applicability = Applicability::MachineApplicable;
let (lsnip, _) = snippet_with_context(cx, l.span, e.span.ctxt(), "...", &mut applicability);
let (rsnip, _) = snippet_with_context(cx, r.span, e.span.ctxt(), "...", &mut applicability);
diag.multipart_suggestion(
"use the values directly",
vec![(left.span, lsnip.to_string()), (right.span, rsnip.to_string())],
applicability,
);
},
);
} 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 mut applicability = Applicability::MachineApplicable;
let (lsnip, _) = snippet_with_context(cx, l.span, e.span.ctxt(), "...", &mut applicability);
diag.span_suggestion(left.span, "use the left value directly", lsnip, applicability);
},
);
} 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 mut applicability = Applicability::MachineApplicable;
let (rsnip, _) = snippet_with_context(cx, r.span, e.span.ctxt(), "...", &mut applicability);
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 mut applicability = Applicability::MachineApplicable;
let (lsnip, _) = snippet_with_context(cx, l.span, e.span.ctxt(), "...", &mut applicability);
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 mut applicability = Applicability::MachineApplicable;
let (rsnip, _) = snippet_with_context(cx, r.span, e.span.ctxt(), "...", &mut applicability);
diag.span_suggestion(
right.span,
let Some(trait_id) = trait_id else {
return;
};

let left_ty = cx.typeck_results().expr_ty(left);
let right_ty = cx.typeck_results().expr_ty(right);
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_pairwise_equal(cx, lty, rty, self_ty, other_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()])
&& let Some(l_span) = walk_span_to_context(l.span, e.span.ctxt())
&& let Some(r_span) = walk_span_to_context(r.span, e.span.ctxt())
{
span_lint_and_then(
cx,
OP_REF,
e.span,
"needlessly taken reference of both operands",
|diag| {
let applicability = Applicability::MachineApplicable;
diag.multipart_suggestion(
"use the values directly",
vec![
(left.span.until(l_span), String::new()),
(right.span.until(r_span), String::new()),
],
applicability,
);
},
);
} else if lcpy
&& !rcpy
&& implements_trait(cx, lty, trait_id, &[right_ty.into()])
&& let Some(l_span) = walk_span_to_context(l.span, e.span.ctxt())
{
span_lint_and_then(
cx,
OP_REF,
e.span,
"needlessly taken reference of left operand",
|diag| {
let applicability = Applicability::MachineApplicable;
diag.span_suggestion_verbose(
left.span.until(l_span),
"use the left value directly",
String::new(),
applicability,
);
},
);
} else if !lcpy
&& rcpy
&& implements_trait(cx, left_ty, trait_id, &[rty.into()])
&& let Some(r_span) = walk_span_to_context(r.span, e.span.ctxt())
{
span_lint_and_then(
cx,
OP_REF,
e.span,
"needlessly taken reference of right operand",
|diag| {
let applicability = Applicability::MachineApplicable;
diag.span_suggestion_verbose(
right.span.until(r_span),
"use the right value directly",
rsnip,
Applicability::MachineApplicable,
String::new(),
applicability,
);
});
}
},
_ => {},
}
},
);
}
},
// &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)
&& are_pairwise_equal(cx, lty, right_ty, self_ty, other_ty)
{
return; // Don't lint
}
let lcpy = is_copy(cx, lty);
if (requires_ref || lcpy)
&& implements_trait(cx, lty, trait_id, &[right_ty.into()])
&& let Some(l_span) = walk_span_to_context(l.span, e.span.ctxt())
{
span_lint_and_then(
cx,
OP_REF,
e.span,
"needlessly taken reference of left operand",
|diag| {
let applicability = Applicability::MachineApplicable;
diag.span_suggestion_verbose(
left.span.until(l_span),
"use the left value directly",
String::new(),
applicability,
);
},
);
}
},
// 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)
&& are_pairwise_equal(cx, left_ty, rty, self_ty, other_ty)
{
return; // Don't lint
}
let rcpy = is_copy(cx, rty);
if (requires_ref || rcpy)
&& implements_trait(cx, left_ty, trait_id, &[rty.into()])
&& let Some(r_span) = walk_span_to_context(r.span, e.span.ctxt())
{
span_lint_and_then(cx, OP_REF, e.span, "taken reference of right operand", |diag| {
let applicability = Applicability::MachineApplicable;
diag.span_suggestion_verbose(
right.span.until(r_span),
"use the right value directly",
String::new(),
applicability,
);
});
}
},
_ => {},
}
}

Expand All @@ -196,15 +203,39 @@ fn in_impl<'tcx>(
}
}

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
/// ```ignore
/// (ty1 == hir_ty1 && ty2 == hir_ty2)
/// || (ty1 == hir_ty2 && ty2 == hir_ty1)
/// ```
fn are_pairwise_equal(
cx: &LateContext<'_>,
ty1: Ty<'_>,
ty2: Ty<'_>,
hir_ty1: &hir::Ty<'_>,
hir_ty2: &hir::Ty<'_>,
) -> bool {
fn middle_ty_did(cx: &LateContext<'_>, ty: Ty<'_>) -> Option<DefId> {
let local_did = ty.ty_adt_def()?.did().as_local()?;
let item = cx.tcx.hir_expect_item(local_did);
Some(item.owner_id.to_def_id())
}

fn hir_ty_did(hir_ty: &hir::Ty<'_>) -> Option<DefId> {
if let TyKind::Path(QPath::Resolved(_, path)) = hir_ty.kind
&& let Res::Def(_, hir_ty_id) = path.res
{
Some(hir_ty_id)
} else {
None
}
}

if let Some(ty1_did) = middle_ty_did(cx, ty1)
&& let Some(ty2_did) = middle_ty_did(cx, ty2)
&& let Some(hir_ty1_did) = hir_ty_did(hir_ty1)
&& let Some(hir_ty2_did) = hir_ty_did(hir_ty2)
{
hir_ty_id == middle_ty_id
(ty1_did == hir_ty1_did && ty2_did == hir_ty2_did) || (ty2_did == hir_ty1_did && ty1_did == hir_ty2_did)
} else {
false
}
Expand Down
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