From 49025fa15c372bebb4c372bae206aa611b87ca1f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=AE=B8=E6=9D=B0=E5=8F=8B=20Jieyou=20Xu=20=28Joe=29?=
 <jieyouxu@outlook.com>
Date: Tue, 20 Feb 2024 11:35:13 +0000
Subject: [PATCH] Downgrade ambiguous_wide_pointer_comparisons suggestions to
 MaybeIncorrect

It is possible to have more than one valid suggestion, which when
applied together via rustfix causes the code to no longer compile.

This is a temporary workaround; the real long term solution to these
issues is to solve <https://github.com/rust-lang/rust/issues/53934>.
---
 compiler/rustc_lint/src/lints.rs              |  6 ++---
 ...wide_pointer_comparisons_suggestions.fixed | 25 +++++++++++++++++++
 ...us_wide_pointer_comparisons_suggestions.rs | 25 +++++++++++++++++++
 ...ide_pointer_comparisons_suggestions.stderr | 18 +++++++++++++
 4 files changed, 71 insertions(+), 3 deletions(-)
 create mode 100644 tests/ui/lint/ambiguous_wide_pointer_comparisons_suggestions.fixed
 create mode 100644 tests/ui/lint/ambiguous_wide_pointer_comparisons_suggestions.rs
 create mode 100644 tests/ui/lint/ambiguous_wide_pointer_comparisons_suggestions.stderr

diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index c204c67fc1f7c..826b49a0e33d8 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -1543,7 +1543,7 @@ pub enum AmbiguousWidePointerComparisons<'a> {
 #[multipart_suggestion(
     lint_addr_metadata_suggestion,
     style = "verbose",
-    applicability = "machine-applicable"
+    applicability = "maybe-incorrect"
 )]
 pub struct AmbiguousWidePointerComparisonsAddrMetadataSuggestion<'a> {
     pub ne: &'a str,
@@ -1562,7 +1562,7 @@ pub enum AmbiguousWidePointerComparisonsAddrSuggestion<'a> {
     #[multipart_suggestion(
         lint_addr_suggestion,
         style = "verbose",
-        applicability = "machine-applicable"
+        applicability = "maybe-incorrect"
     )]
     AddrEq {
         ne: &'a str,
@@ -1578,7 +1578,7 @@ pub enum AmbiguousWidePointerComparisonsAddrSuggestion<'a> {
     #[multipart_suggestion(
         lint_addr_suggestion,
         style = "verbose",
-        applicability = "machine-applicable"
+        applicability = "maybe-incorrect"
     )]
     Cast {
         deref_left: &'a str,
diff --git a/tests/ui/lint/ambiguous_wide_pointer_comparisons_suggestions.fixed b/tests/ui/lint/ambiguous_wide_pointer_comparisons_suggestions.fixed
new file mode 100644
index 0000000000000..0de6e3a2dd831
--- /dev/null
+++ b/tests/ui/lint/ambiguous_wide_pointer_comparisons_suggestions.fixed
@@ -0,0 +1,25 @@
+//@ run-rustfix
+//@ rustfix-only-machine-applicable
+//@ check-pass
+
+// See <https://github.com/rust-lang/rust/issues/121330>.
+
+use std::cmp::PartialEq;
+use std::rc::Rc;
+use std::sync::Arc;
+
+struct A;
+struct B;
+
+trait T {}
+impl T for A {}
+impl T for B {}
+
+fn main() {
+    fn cmp<T: ?Sized>(a: *mut T, b: *mut T) -> bool {
+        let _ = a == b;
+        //~^ WARN ambiguous wide pointer comparison
+
+        panic!();
+    }
+}
diff --git a/tests/ui/lint/ambiguous_wide_pointer_comparisons_suggestions.rs b/tests/ui/lint/ambiguous_wide_pointer_comparisons_suggestions.rs
new file mode 100644
index 0000000000000..0de6e3a2dd831
--- /dev/null
+++ b/tests/ui/lint/ambiguous_wide_pointer_comparisons_suggestions.rs
@@ -0,0 +1,25 @@
+//@ run-rustfix
+//@ rustfix-only-machine-applicable
+//@ check-pass
+
+// See <https://github.com/rust-lang/rust/issues/121330>.
+
+use std::cmp::PartialEq;
+use std::rc::Rc;
+use std::sync::Arc;
+
+struct A;
+struct B;
+
+trait T {}
+impl T for A {}
+impl T for B {}
+
+fn main() {
+    fn cmp<T: ?Sized>(a: *mut T, b: *mut T) -> bool {
+        let _ = a == b;
+        //~^ WARN ambiguous wide pointer comparison
+
+        panic!();
+    }
+}
diff --git a/tests/ui/lint/ambiguous_wide_pointer_comparisons_suggestions.stderr b/tests/ui/lint/ambiguous_wide_pointer_comparisons_suggestions.stderr
new file mode 100644
index 0000000000000..ea8383ad30eaf
--- /dev/null
+++ b/tests/ui/lint/ambiguous_wide_pointer_comparisons_suggestions.stderr
@@ -0,0 +1,18 @@
+warning: ambiguous wide pointer comparison, the comparison includes metadata which may not be expected
+  --> $DIR/ambiguous_wide_pointer_comparisons_suggestions.rs:20:17
+   |
+LL |         let _ = a == b;
+   |                 ^^^^^^
+   |
+   = note: `#[warn(ambiguous_wide_pointer_comparisons)]` on by default
+help: use `std::ptr::addr_eq` or untyped pointers to only compare their addresses
+   |
+LL |         let _ = std::ptr::addr_eq(a, b);
+   |                 ++++++++++++++++++ ~  +
+help: use explicit `std::ptr::eq` method to compare metadata and addresses
+   |
+LL |         let _ = std::ptr::eq(a, b);
+   |                 +++++++++++++ ~  +
+
+warning: 1 warning emitted
+