From d4a22f436f8deb77f80ece751973f6c7b76dbd25 Mon Sep 17 00:00:00 2001
From: Matthew Hughes <matthewhughes934@gmail.com>
Date: Wed, 2 Sep 2026 19:50:34 +0100
Subject: [PATCH] `chain`: drop redundant check
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In the code: `chain_item` is a _child_ in the chain, and not the root,
e.g. `1.foo.bar` in `root.1.foo.bar`. So the question is, can a
`try!(..)` expression appear there, e.g. `root.try!(something).0`? My
conclusion is that it cannot: firstly note `try!` is not a valid
identifier (because of the `!`), so working through the possible chain
types (see `pop_expr_chain`):

* `MethodCallExpression → Expression . PathExprSegment ( CallParams? )`
  (e.g. `root.some_method()`): `PathExprSegment` starts with a
  `PathIdentSegment`, starts with a `IDENTIFIER`: `try!` doesn't match
* `FieldExpression → Expression . IDENTIFIER` (e.g. `root.sub`): `try!`
  doesn't match
* `TupleIndexingExpression → Expression . TUPLE_INDEX` (e.g. `root.0`):
  tuple index is repeated decimal digits: `try!` doesn't match
* keywords:`.await`, `.use`, `.yield`: `try!` doesn't
  match

Of course a: `try!` can be the _root_ of a chain `try!(foo).bar` is
perfectly valid.

This fixes an issue: as previously, if the `use_try_shorthand` config
was set we would skip over any comments in any children of the chain,
so they would be dropped. The added test case covers this situation.

Fixes: rust-lang/rustfmt#6121
---
 src/chains.rs          | 4 +---
 tests/source/chains.rs | 6 ++++++
 tests/target/chains.rs | 6 ++++++
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/chains.rs b/src/chains.rs
index 45d9d488c76..dd826734db4 100644
--- a/src/chains.rs
+++ b/src/chains.rs
@@ -458,9 +458,7 @@ impl Chain {
         }
         while let Some(chain_item) = iter.next() {
             let comment_snippet = context.snippet(chain_item.span);
-            // FIXME: Figure out the way to get a correct span when converting `try!` to `?`.
-            let handle_comment =
-                !(context.config.use_try_shorthand() || is_tries(comment_snippet.trim()));
+            let handle_comment = !is_tries(comment_snippet.trim());
 
             // Pre-comment
             if handle_comment {
diff --git a/tests/source/chains.rs b/tests/source/chains.rs
index c77f5bac4cb..a16712e5be1 100644
--- a/tests/source/chains.rs
+++ b/tests/source/chains.rs
@@ -264,3 +264,9 @@ fn issue_3034() {
     disallowed_headers.iter().any(|header| *header == name) ||
         disallowed_header_prefixes.iter().any(|prefix| name.starts_with(prefix))
 }
+
+fn issue_6121() {
+    let _ = foo // some comment
+            .bar // some other comment
+        .buz;
+}
diff --git a/tests/target/chains.rs b/tests/target/chains.rs
index 292da298195..4fc23745126 100644
--- a/tests/target/chains.rs
+++ b/tests/target/chains.rs
@@ -304,3 +304,9 @@ fn issue_3034() {
     disallowed_headers.iter().any(|header| *header == name)
         || disallowed_header_prefixes.iter().any(|prefix| name.starts_with(prefix))
 }
+
+fn issue_6121() {
+    let _ = foo // some comment
+        .bar // some other comment
+        .buz;
+}