From 891e38788a36c3d217e4e06d52e4ee67797b8ccb Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Sat, 4 Jan 2025 12:54:19 +0100
Subject: [PATCH 1/2] Don't emit machine applicable `map_flatten` lint if there
 are code comments

---
 clippy_lints/src/methods/map_flatten.rs | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/clippy_lints/src/methods/map_flatten.rs b/clippy_lints/src/methods/map_flatten.rs
index 07a7a12b1627..f7bb8c1d696d 100644
--- a/clippy_lints/src/methods/map_flatten.rs
+++ b/clippy_lints/src/methods/map_flatten.rs
@@ -1,7 +1,7 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
-use clippy_utils::is_trait_method;
 use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::{is_trait_method, span_contains_comment};
 use rustc_errors::Applicability;
 use rustc_hir::Expr;
 use rustc_lint::LateContext;
@@ -17,10 +17,15 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, map_
         let mut applicability = Applicability::MachineApplicable;
 
         let closure_snippet = snippet_with_applicability(cx, map_arg.span, "..", &mut applicability);
+        let span = expr.span.with_lo(map_span.lo());
+        // If the methods are separated with comments, we don't apply suggestion automatically.
+        if span_contains_comment(cx.tcx.sess.source_map(), span) {
+            applicability = Applicability::Unspecified;
+        }
         span_lint_and_sugg(
             cx,
             MAP_FLATTEN,
-            expr.span.with_lo(map_span.lo()),
+            span,
             format!("called `map(..).flatten()` on `{caller_ty_name}`"),
             format!("try replacing `map` with `{method_to_use}` and remove the `.flatten()`"),
             format!("{method_to_use}({closure_snippet})"),

From 78225ccca8980e357123ac936655a40e0b0c8b8f Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Sat, 4 Jan 2025 12:55:09 +0100
Subject: [PATCH 2/2] Add regression test for #8528

---
 tests/ui/map_flatten.rs     | 12 ++++++++++++
 tests/ui/map_flatten.stderr | 11 ++++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/tests/ui/map_flatten.rs b/tests/ui/map_flatten.rs
index 76916d465919..eafc8b6e81ca 100644
--- a/tests/ui/map_flatten.rs
+++ b/tests/ui/map_flatten.rs
@@ -55,6 +55,18 @@ fn long_span() {
         .collect();
 }
 
+#[allow(clippy::useless_vec)]
+fn no_suggestion_if_comments_present() {
+    let vec = vec![vec![1, 2, 3]];
+    let _ = vec
+        .iter()
+        // a lovely comment explaining the code in very detail
+        .map(|x| x.iter())
+        //~^ ERROR: called `map(..).flatten()` on `Iterator`
+        // the answer to life, the universe and everything could be here
+        .flatten();
+}
+
 fn main() {
     long_span();
 }
diff --git a/tests/ui/map_flatten.stderr b/tests/ui/map_flatten.stderr
index a5837b97617d..34bd174d7dde 100644
--- a/tests/ui/map_flatten.stderr
+++ b/tests/ui/map_flatten.stderr
@@ -102,5 +102,14 @@ LL +             }
 LL +         })
    |
 
-error: aborting due to 4 previous errors
+error: called `map(..).flatten()` on `Iterator`
+  --> tests/ui/map_flatten.rs:64:10
+   |
+LL |           .map(|x| x.iter())
+   |  __________^
+...  |
+LL | |         .flatten();
+   | |__________________^ help: try replacing `map` with `flat_map` and remove the `.flatten()`: `flat_map(|x| x.iter())`
+
+error: aborting due to 5 previous errors