Add test case for rust-lang#6040

tests/source/issue_6040.rs

@@ -0,0 +1,21 @@
+fn main() {
+    match e { // this line still gets formatted
+            MyStruct {
+                field_a,
+                .. // this comment here apparently causes trouble
+            } => (),
+    _ => (), // this line is no longer formatted
+        };
+}
+
+fn main() {
+    match e {                                           // this line still gets formatted
+        MyStruct {
+            field_a,
+                field_b, // this should be aligned with field_a
+                    field_c, // this should be aligned with field_a
+                        } => (),
+
+        _ => (), // this line is no longer formatted
+    };
+}

tests/target/issue_6040.rs

@@ -0,0 +1,23 @@
+fn main() {
+    match e {
+        // this line still gets formatted
+        MyStruct {
+            field_a,
+            .. // this comment here apparently causes trouble
+        } => (),
+        _ => (), // this line is no longer formatted
+    };
+}
+
+fn main() {
+    match e {
+        // this line still gets formatted
+        MyStruct {
+            field_a,
+            field_b, // this should be aligned with field_a
+            field_c, // this should be aligned with field_a
+        } => (),
+
+        _ => (), // this line is no longer formatted
+    };
+}