fix Comma in comment causes no formatting

src/lists.rs

@@ -612,7 +612,7 @@ pub fn extract_post_comment(
         post_snippet[1..].trim_matches(white_space)
     } else if post_snippet.starts_with(separator) {
         post_snippet[separator.len()..].trim_matches(white_space)
-    } else if post_snippet.ends_with(',') {
+    } else if post_snippet.ends_with(',') && !post_snippet.trim().starts_with("//") {
         post_snippet[..(post_snippet.len() - 1)].trim_matches(white_space)
     } else {
         post_snippet

tests/source/issue-3532.rs

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

tests/target/issue-3532.rs

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