Fixed trailing comment being moved when comma is inserted

src/formatting/lists.rs

@@ -632,23 +632,28 @@ pub(crate) fn extract_post_comment(
     post_snippet: &str,
     comment_end: usize,
     separator: &str,
+    leave_last: bool,
 ) -> Option<String> {
     let white_space: &[_] = &[' ', '\t'];
 
     // Cleanup post-comment: strip separators and whitespace.
-    let post_snippet = post_snippet[..comment_end].trim();
-    let post_snippet_trimmed = if post_snippet.starts_with(|c| c == ',' || c == ':') {
-        post_snippet[1..].trim_matches(white_space)
-    } else if let Some(post_snippet) = post_snippet.strip_prefix(separator) {
+    let (post_snippet, comment_end) = post_snippet.split_at(comment_end);
+    let post_snippet_trimmed = post_snippet.trim();
+
+    let post_snippet_trimmed = if post_snippet_trimmed.starts_with(|c| c == ',' || c == ':') {
+        post_snippet_trimmed[1..].trim_matches(white_space)
+    } else if let Some(post_snippet) = post_snippet_trimmed.strip_prefix(separator) {
         post_snippet.trim_matches(white_space)
     }
     // not comment or over two lines
-    else if post_snippet.ends_with(',')
-        && (!post_snippet.trim().starts_with("//") || post_snippet.trim().contains('\n'))
+    else if post_snippet_trimmed.ends_with(',')
+        && (!post_snippet_trimmed.starts_with("//") || post_snippet_trimmed.contains('\n'))
     {
-        post_snippet[..(post_snippet.len() - 1)].trim_matches(white_space)
+        post_snippet_trimmed[..(post_snippet_trimmed.len() - 1)].trim_matches(white_space)
+    } else if comment_end == ")" && !leave_last {
+        post_snippet_trimmed
     } else {
-        post_snippet
+        post_snippet.trim_start_matches(white_space).trim_end()
     };
     // FIXME(#3441): post_snippet includes 'const' now
     // it should not include here
@@ -776,7 +781,8 @@ where
                 self.inner.peek().is_none(),
             );
             let new_lines = has_extra_newline(post_snippet, comment_end);
-            let post_comment = extract_post_comment(post_snippet, comment_end, self.separator);
+            let post_comment =
+                extract_post_comment(post_snippet, comment_end, self.separator, self.leave_last);
 
             self.prev_span_end = (self.get_hi)(&item) + BytePos(comment_end as u32);
 

tests/source/issue-4654.rs

@@ -0,0 +1,45 @@
+struct Foo {
+    bar: ()
+        // Comment
+}
+
+struct Bar {
+    baz: ()
+/*
+Comment
+*/
+}
+
+struct Baz(
+    ()
+        // Comment
+);
+
+fn main() {
+    let _ = Foo {
+        bar: ()
+                // Comment
+    };
+
+    let _ = Bar {
+        baz: ()
+    /*
+    Comment
+    */
+    };
+
+    let _ = Baz(
+        ()
+
+            // Comment
+    );
+
+    match a {
+0 => {}
+        // Foo
+    1 => {} // Bar
+        // Baz
+            2 => {}
+// Qux
+    }
+}

tests/target/issue-3532.rs

@@ -1,6 +1,7 @@
 fn foo(a: T) {
     match a {
         1 => {}
-        0 => {} // _ => panic!("doesn't format!"),
+        0 => {}
+        // _ => panic!("doesn't format!"),
     }
 }

tests/target/issue-4654.rs

@@ -0,0 +1,44 @@
+struct Foo {
+    bar: (),
+    // Comment
+}
+
+struct Bar {
+    baz: (),
+    /*
+    Comment
+    */
+}
+
+struct Baz(
+    (),
+    // Comment
+);
+
+fn main() {
+    let _ = Foo {
+        bar: (),
+        // Comment
+    };
+
+    let _ = Bar {
+        baz: (),
+        /*
+        Comment
+        */
+    };
+
+    let _ = Baz(
+        (),
+        // Comment
+    );
+
+    match a {
+        0 => {}
+        // Foo
+        1 => {} // Bar
+        // Baz
+        2 => {}
+        // Qux
+    }
+}