Fix bad suggestion that needs curly braces for `match_single_binding` lint

3 files changed, 90 insertions, 1 deletions

diff --git a/tests/ui/match_single_binding.fixed b/tests/ui/match_single_binding.fixed
index 526e94b10bd..4709b5b0157 100644
--- a/tests/ui/match_single_binding.fixed
+++ b/tests/ui/match_single_binding.fixed
@@ -115,4 +115,33 @@ fn main() {
         // =>
         _ => println!("Not an array index start"),
     }
+    // Lint (additional curly braces needed, see #6572)
+    struct AppendIter<I>
+    where
+        I: Iterator,
+    {
+        inner: Option<(I, <I as Iterator>::Item)>,
+    }
+
+    #[allow(dead_code)]
+    fn size_hint<I: Iterator>(iter: &AppendIter<I>) -> (usize, Option<usize>) {
+        match &iter.inner {
+            Some((iter, _item)) => {
+                let (min, max) = iter.size_hint();
+                (min.saturating_add(1), max.and_then(|max| max.checked_add(1)))
+            },
+            None => (0, Some(0)),
+        }
+    }
+    // Lint (no additional curly braces needed)
+    let opt = Some((5, 2));
+    let get_tup = || -> (i32, i32) { (1, 2) };
+    match opt {
+        #[rustfmt::skip]
+        Some((first, _second)) => {
+            let (a, b) = get_tup();
+            println!("a {:?} and b {:?}", a, b);
+        },
+        None => println!("nothing"),
+    }
 }
diff --git a/tests/ui/match_single_binding.rs b/tests/ui/match_single_binding.rs
index 6a2ca7c5e93..6a6b3e8e8a9 100644
--- a/tests/ui/match_single_binding.rs
+++ b/tests/ui/match_single_binding.rs
@@ -132,4 +132,33 @@ fn main() {
         // =>
         _ => println!("Not an array index start"),
     }
+    // Lint (additional curly braces needed, see #6572)
+    struct AppendIter<I>
+    where
+        I: Iterator,
+    {
+        inner: Option<(I, <I as Iterator>::Item)>,
+    }
+
+    #[allow(dead_code)]
+    fn size_hint<I: Iterator>(iter: &AppendIter<I>) -> (usize, Option<usize>) {
+        match &iter.inner {
+            Some((iter, _item)) => match iter.size_hint() {
+                (min, max) => (min.saturating_add(1), max.and_then(|max| max.checked_add(1))),
+            },
+            None => (0, Some(0)),
+        }
+    }
+    // Lint (no additional curly braces needed)
+    let opt = Some((5, 2));
+    let get_tup = || -> (i32, i32) { (1, 2) };
+    match opt {
+        #[rustfmt::skip]
+        Some((first, _second)) => {
+            match get_tup() {
+                (a, b) => println!("a {:?} and b {:?}", a, b),
+            }
+        },
+        None => println!("nothing"),
+    }
 }
diff --git a/tests/ui/match_single_binding.stderr b/tests/ui/match_single_binding.stderr
index cbbf5d29c02..73cc867dd9f 100644
--- a/tests/ui/match_single_binding.stderr
+++ b/tests/ui/match_single_binding.stderr
@@ -178,5 +178,36 @@ LL | |         _ => println!("Single branch"),
 LL | |     }
    | |_____^ help: consider using the match body instead: `println!("Single branch");`
 
-error: aborting due to 12 previous errors
+error: this match could be written as a `let` statement
+  --> $DIR/match_single_binding.rs:146:36
+   |
+LL |               Some((iter, _item)) => match iter.size_hint() {
+   |  ____________________________________^
+LL | |                 (min, max) => (min.saturating_add(1), max.and_then(|max| max.checked_add(1))),
+LL | |             },
+   | |_____________^
+   |
+help: consider using `let` statement
+   |
+LL |             Some((iter, _item)) => {
+LL |                 let (min, max) = iter.size_hint();
+LL |                 (min.saturating_add(1), max.and_then(|max| max.checked_add(1)))
+LL |             },
+   |
+
+error: this match could be written as a `let` statement
+  --> $DIR/match_single_binding.rs:158:13
+   |
+LL | /             match get_tup() {
+LL | |                 (a, b) => println!("a {:?} and b {:?}", a, b),
+LL | |             }
+   | |_____________^
+   |
+help: consider using `let` statement
+   |
+LL |             let (a, b) = get_tup();
+LL |             println!("a {:?} and b {:?}", a, b);
+   |
+
+error: aborting due to 14 previous errors