From f9faf161817eef2b885bd47908ceaeef675ea72f Mon Sep 17 00:00:00 2001
From: sjwang05 <63834813+sjwang05@users.noreply.github.com>
Date: Thu, 11 Jan 2024 21:02:43 -0800
Subject: [PATCH] Suggest .swap() instead of mem::swap() in more cases
---
.../src/diagnostics/conflict_errors.rs | 99 +++++++++++++++++--
tests/ui/suggestions/suggest-slice-swap.fixed | 9 ++
tests/ui/suggestions/suggest-slice-swap.rs | 9 ++
.../ui/suggestions/suggest-slice-swap.stderr | 17 ++++
4 files changed, 127 insertions(+), 7 deletions(-)
create mode 100644 tests/ui/suggestions/suggest-slice-swap.fixed
create mode 100644 tests/ui/suggestions/suggest-slice-swap.rs
create mode 100644 tests/ui/suggestions/suggest-slice-swap.stderr
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index 5baa108ed3cce..a230ba0e439f4 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -1,3 +1,5 @@
+// ignore-tidy-filelength
+
use either::Either;
use rustc_data_structures::captures::Captures;
use rustc_data_structures::fx::FxIndexSet;
@@ -24,6 +26,7 @@ use rustc_span::hygiene::DesugaringKind;
use rustc_span::symbol::{kw, sym, Ident};
use rustc_span::{BytePos, Span, Symbol};
use rustc_trait_selection::infer::InferCtxtExt;
+use rustc_trait_selection::traits::error_reporting::FindExprBySpan;
use rustc_trait_selection::traits::ObligationCtxt;
use std::iter;
@@ -1295,14 +1298,96 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
place: Place<'tcx>,
borrowed_place: Place<'tcx>,
) {
- if let ([ProjectionElem::Index(_)], [ProjectionElem::Index(_)]) =
- (&place.projection[..], &borrowed_place.projection[..])
+ let tcx = self.infcx.tcx;
+ let hir = tcx.hir();
+
+ if let ([ProjectionElem::Index(index1)], [ProjectionElem::Index(index2)])
+ | (
+ [ProjectionElem::Deref, ProjectionElem::Index(index1)],
+ [ProjectionElem::Deref, ProjectionElem::Index(index2)],
+ ) = (&place.projection[..], &borrowed_place.projection[..])
{
- err.help(
- "consider using `.split_at_mut(position)` or similar method to obtain \
- two mutable non-overlapping sub-slices",
- )
- .help("consider using `.swap(index_1, index_2)` to swap elements at the specified indices");
+ let mut note_default_suggestion = || {
+ err.help(
+ "consider using `.split_at_mut(position)` or similar method to obtain \
+ two mutable non-overlapping sub-slices",
+ )
+ .help("consider using `.swap(index_1, index_2)` to swap elements at the specified indices");
+ };
+
+ let Some(body_id) = tcx.hir_node(self.mir_hir_id()).body_id() else {
+ note_default_suggestion();
+ return;
+ };
+
+ let mut expr_finder =
+ FindExprBySpan::new(self.body.local_decls[*index1].source_info.span);
+ expr_finder.visit_expr(hir.body(body_id).value);
+ let Some(index1) = expr_finder.result else {
+ note_default_suggestion();
+ return;
+ };
+
+ expr_finder = FindExprBySpan::new(self.body.local_decls[*index2].source_info.span);
+ expr_finder.visit_expr(hir.body(body_id).value);
+ let Some(index2) = expr_finder.result else {
+ note_default_suggestion();
+ return;
+ };
+
+ let sm = tcx.sess.source_map();
+
+ let Ok(index1_str) = sm.span_to_snippet(index1.span) else {
+ note_default_suggestion();
+ return;
+ };
+
+ let Ok(index2_str) = sm.span_to_snippet(index2.span) else {
+ note_default_suggestion();
+ return;
+ };
+
+ let Some(object) = hir.parent_id_iter(index1.hir_id).find_map(|id| {
+ if let hir::Node::Expr(expr) = tcx.hir_node(id)
+ && let hir::ExprKind::Index(obj, ..) = expr.kind
+ {
+ Some(obj)
+ } else {
+ None
+ }
+ }) else {
+ note_default_suggestion();
+ return;
+ };
+
+ let Ok(obj_str) = sm.span_to_snippet(object.span) else {
+ note_default_suggestion();
+ return;
+ };
+
+ let Some(swap_call) = hir.parent_id_iter(object.hir_id).find_map(|id| {
+ if let hir::Node::Expr(call) = tcx.hir_node(id)
+ && let hir::ExprKind::Call(callee, ..) = call.kind
+ && let hir::ExprKind::Path(qpath) = callee.kind
+ && let hir::QPath::Resolved(None, res) = qpath
+ && let hir::def::Res::Def(_, did) = res.res
+ && tcx.is_diagnostic_item(sym::mem_swap, did)
+ {
+ Some(call)
+ } else {
+ None
+ }
+ }) else {
+ note_default_suggestion();
+ return;
+ };
+
+ err.span_suggestion(
+ swap_call.span,
+ "use `.swap()` to swap elements at the specified indices instead",
+ format!("{obj_str}.swap({index1_str}, {index2_str})"),
+ Applicability::MachineApplicable,
+ );
}
}
diff --git a/tests/ui/suggestions/suggest-slice-swap.fixed b/tests/ui/suggestions/suggest-slice-swap.fixed
new file mode 100644
index 0000000000000..05b7ec2637985
--- /dev/null
+++ b/tests/ui/suggestions/suggest-slice-swap.fixed
@@ -0,0 +1,9 @@
+// run-rustfix
+#![allow(dead_code)]
+
+fn swap(arr: &mut [u32; 2]) {
+ arr.swap(1, 0);
+ //~^ ERROR cannot borrow `arr[_]` as mutable more than once at a time
+}
+
+fn main() {}
diff --git a/tests/ui/suggestions/suggest-slice-swap.rs b/tests/ui/suggestions/suggest-slice-swap.rs
new file mode 100644
index 0000000000000..9f3659aac1637
--- /dev/null
+++ b/tests/ui/suggestions/suggest-slice-swap.rs
@@ -0,0 +1,9 @@
+// run-rustfix
+#![allow(dead_code)]
+
+fn swap(arr: &mut [u32; 2]) {
+ std::mem::swap(&mut arr[0], &mut arr[1]);
+ //~^ ERROR cannot borrow `arr[_]` as mutable more than once at a time
+}
+
+fn main() {}
diff --git a/tests/ui/suggestions/suggest-slice-swap.stderr b/tests/ui/suggestions/suggest-slice-swap.stderr
new file mode 100644
index 0000000000000..2840fc0a76116
--- /dev/null
+++ b/tests/ui/suggestions/suggest-slice-swap.stderr
@@ -0,0 +1,17 @@
+error[E0499]: cannot borrow `arr[_]` as mutable more than once at a time
+ --> $DIR/suggest-slice-swap.rs:5:33
+ |
+LL | std::mem::swap(&mut arr[0], &mut arr[1]);
+ | -------------- ----------- ^^^^^^^^^^^ second mutable borrow occurs here
+ | | |
+ | | first mutable borrow occurs here
+ | first borrow later used by call
+ |
+help: use `.swap()` to swap elements at the specified indices instead
+ |
+LL | arr.swap(1, 0);
+ | ~~~~~~~~~~~~~~
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0499`.