From 4d386d9f049da498b5f072b6c358a6fbbe0baf59 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               |  9 ++++++---
 ..._wide_pointer_comparisons_suggestions.fixed | 13 +++++++++++++
 ...ous_wide_pointer_comparisons_suggestions.rs | 13 +++++++++++++
 ...wide_pointer_comparisons_suggestions.stderr | 18 ++++++++++++++++++
 4 files changed, 50 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 c204c67fc1f..71107be206b 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -1543,7 +1543,8 @@ pub enum AmbiguousWidePointerComparisons<'a> {
 #[multipart_suggestion(
     lint_addr_metadata_suggestion,
     style = "verbose",
-    applicability = "machine-applicable"
+    // FIXME(#53934): make machine-applicable again
+    applicability = "maybe-incorrect"
 )]
 pub struct AmbiguousWidePointerComparisonsAddrMetadataSuggestion<'a> {
     pub ne: &'a str,
@@ -1562,7 +1563,8 @@ pub enum AmbiguousWidePointerComparisonsAddrSuggestion<'a> {
     #[multipart_suggestion(
         lint_addr_suggestion,
         style = "verbose",
-        applicability = "machine-applicable"
+        // FIXME(#53934): make machine-applicable again
+        applicability = "maybe-incorrect"
     )]
     AddrEq {
         ne: &'a str,
@@ -1578,7 +1580,8 @@ pub enum AmbiguousWidePointerComparisonsAddrSuggestion<'a> {
     #[multipart_suggestion(
         lint_addr_suggestion,
         style = "verbose",
-        applicability = "machine-applicable"
+        // FIXME(#53934): make machine-applicable again
+        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 00000000000..6ce68ff9640
--- /dev/null
+++ b/tests/ui/lint/ambiguous_wide_pointer_comparisons_suggestions.fixed
@@ -0,0 +1,13 @@
+//@ run-rustfix
+//@ rustfix-only-machine-applicable
+//@ check-pass
+
+// See <https://github.com/rust-lang/rust/issues/121330>.
+
+fn cmp<T: ?Sized>(a: *mut T, b: *mut T) -> bool {
+    let _ = a == b;
+    //~^ WARN ambiguous wide pointer comparison
+    panic!();
+}
+
+fn main() {}
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 00000000000..6ce68ff9640
--- /dev/null
+++ b/tests/ui/lint/ambiguous_wide_pointer_comparisons_suggestions.rs
@@ -0,0 +1,13 @@
+//@ run-rustfix
+//@ rustfix-only-machine-applicable
+//@ check-pass
+
+// See <https://github.com/rust-lang/rust/issues/121330>.
+
+fn cmp<T: ?Sized>(a: *mut T, b: *mut T) -> bool {
+    let _ = a == b;
+    //~^ WARN ambiguous wide pointer comparison
+    panic!();
+}
+
+fn main() {}
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 00000000000..d9190dbb813
--- /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:8:13
+   |
+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
+