From 8dd310ddd7524223c1405d22155ab41b546c746a Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Wed, 17 Jul 2024 20:59:46 +0200
Subject: [PATCH] Fix wrong suggestion for `single_element_loop` where parens
 were missing

---
 clippy_lints/src/loops/single_element_loop.rs |  7 +++++--
 tests/ui/single_element_loop.fixed            |  8 ++++++++
 tests/ui/single_element_loop.rs               |  7 +++++++
 tests/ui/single_element_loop.stderr           | 18 +++++++++++++++++-
 4 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/clippy_lints/src/loops/single_element_loop.rs b/clippy_lints/src/loops/single_element_loop.rs
index 108fdb69775..2b41911e8ec 100644
--- a/clippy_lints/src/loops/single_element_loop.rs
+++ b/clippy_lints/src/loops/single_element_loop.rs
@@ -5,7 +5,7 @@
 use rustc_ast::util::parser::PREC_PREFIX;
 use rustc_ast::Mutability;
 use rustc_errors::Applicability;
-use rustc_hir::{is_range_literal, BorrowKind, Expr, ExprKind, Pat};
+use rustc_hir::{is_range_literal, BorrowKind, Expr, ExprKind, Pat, PatKind};
 use rustc_lint::LateContext;
 use rustc_span::edition::Edition;
 use rustc_span::sym;
@@ -70,7 +70,10 @@ pub(super) fn check<'tcx>(
         && !contains_break_or_continue(body)
     {
         let mut applicability = Applicability::MachineApplicable;
-        let pat_snip = snippet_with_applicability(cx, pat.span, "..", &mut applicability);
+        let mut pat_snip = snippet_with_applicability(cx, pat.span, "..", &mut applicability);
+        if matches!(pat.kind, PatKind::Or(..)) {
+            pat_snip = format!("({pat_snip})").into();
+        }
         let mut arg_snip = snippet_with_applicability(cx, arg_expression.span, "..", &mut applicability);
         let mut block_str = snippet_with_applicability(cx, block.span, "..", &mut applicability).into_owned();
         block_str.remove(0);
diff --git a/tests/ui/single_element_loop.fixed b/tests/ui/single_element_loop.fixed
index 4e59c763198..64cbd5e9c90 100644
--- a/tests/ui/single_element_loop.fixed
+++ b/tests/ui/single_element_loop.fixed
@@ -57,4 +57,12 @@ fn main() {
             }
         };
     }
+
+    // Should lint with correct suggestion (issue #12782)
+    let res_void: Result<bool, bool> = Ok(true);
+
+    {
+        let (Ok(mut _x) | Err(mut _x)) = res_void;
+        let ptr: *const bool = std::ptr::null();
+    }
 }
diff --git a/tests/ui/single_element_loop.rs b/tests/ui/single_element_loop.rs
index a55ece6b065..92406f1c1ca 100644
--- a/tests/ui/single_element_loop.rs
+++ b/tests/ui/single_element_loop.rs
@@ -54,4 +54,11 @@ fn main() {
             }
         };
     }
+
+    // Should lint with correct suggestion (issue #12782)
+    let res_void: Result<bool, bool> = Ok(true);
+
+    for (Ok(mut _x) | Err(mut _x)) in [res_void] {
+        let ptr: *const bool = std::ptr::null();
+    }
 }
diff --git a/tests/ui/single_element_loop.stderr b/tests/ui/single_element_loop.stderr
index dfae5605b57..73453dd2dfd 100644
--- a/tests/ui/single_element_loop.stderr
+++ b/tests/ui/single_element_loop.stderr
@@ -83,5 +83,21 @@ LL +         };
 LL +     }
    |
 
-error: aborting due to 7 previous errors
+error: for loop over a single element
+  --> tests/ui/single_element_loop.rs:61:5
+   |
+LL | /     for (Ok(mut _x) | Err(mut _x)) in [res_void] {
+LL | |         let ptr: *const bool = std::ptr::null();
+LL | |     }
+   | |_____^
+   |
+help: try
+   |
+LL ~     {
+LL +         let (Ok(mut _x) | Err(mut _x)) = res_void;
+LL +         let ptr: *const bool = std::ptr::null();
+LL +     }
+   |
+
+error: aborting due to 8 previous errors