fix [manual_flatten] help texts order

clippy_lints/src/loops/manual_flatten.rs

@@ -51,22 +51,32 @@ pub(super) fn check<'tcx>(
                 _ => ""
             };
 
+            let sugg = format!("{arg_snippet}{copied}.flatten()");
+
+            // If suggestion is not a one-liner, it won't be shown inline within the error message. In that case,
+            // it will be shown in the extra `help` message at the end, which is why the first `help_msg` needs
+            // to refer to the correct relative position of the suggestion.
+            let help_msg = if sugg.contains('\n') {
+                "remove the `if let` statement in the for loop and then..."
+            } else {
+                "...and remove the `if let` statement in the for loop"
+            };
+
             span_lint_and_then(
                 cx,
                 MANUAL_FLATTEN,
                 span,
                 &msg,
                 |diag| {
-                    let sugg = format!("{}{}.flatten()", arg_snippet, copied);
                     diag.span_suggestion(
                         arg.span,
                         "try",
                         sugg,
-                        Applicability::MaybeIncorrect,
+                        applicability,
                     );
                     diag.span_help(
                         inner_expr.span,
-                        "...and remove the `if let` statement in the for loop",
+                        help_msg,
                     );
                 }
             );

tests/lint_message_convention.rs

@@ -42,6 +42,7 @@ impl Message {
             r".*remove .*the return type...",
             r"note: Clippy version: .*",
             r"the compiler unexpectedly panicked. this is a bug.",
+            r"remove the `if let` statement in the for loop and then...",
         ])
         .unwrap();
 

tests/ui/manual_flatten.rs

@@ -106,4 +106,20 @@ fn main() {
     for n in vec![Some(1), Some(2), Some(3)].iter().flatten() {
         println!("{}", n);
     }
+
+    run_unformatted_tests();
+}
+
+#[rustfmt::skip]
+fn run_unformatted_tests() {
+    // Skip rustfmt here on purpose so the suggestion does not fit in one line
+    for n in vec![
+        Some(1),
+        Some(2),
+        Some(3)
+    ].iter() {
+        if let Some(n) = n {
+            println!("{:?}", n);
+        }
+    }
 }

tests/ui/manual_flatten.stderr

@@ -167,5 +167,33 @@ LL | |             println!("{:?}", n);
 LL | |         }
    | |_________^
 
-error: aborting due to 8 previous errors
+error: unnecessary `if let` since only the `Some` variant of the iterator element is used
+  --> $DIR/manual_flatten.rs:116:5
+   |
+LL | /     for n in vec![
+LL | |         Some(1),
+LL | |         Some(2),
+LL | |         Some(3)
+...  |
+LL | |         }
+LL | |     }
+   | |_____^
+   |
+help: remove the `if let` statement in the for loop and then...
+  --> $DIR/manual_flatten.rs:121:9
+   |
+LL | /         if let Some(n) = n {
+LL | |             println!("{:?}", n);
+LL | |         }
+   | |_________^
+help: try
+   |
+LL ~     for n in vec![
+LL +         Some(1),
+LL +         Some(2),
+LL +         Some(3)
+LL ~     ].iter().flatten() {
+   |
+
+error: aborting due to 9 previous errors