error[E02001]: duplicate declaration, item, or annotation
  ┌─ tests/move_check/expansion/duplicate_field_unpack.move:4:13
  │
4 │         let S { f, f } = S { f: 0 };
  │             ^^^^^^^^^^
  │             │   │  │
  │             │   │  Duplicate binding given for field 'f'
  │             │   Field previously defined here
  │             Invalid deconstruction binding

warning[W09003]: unused assignment
  ┌─ tests/move_check/expansion/duplicate_field_unpack.move:4:17
  │
4 │         let S { f, f } = S { f: 0 };
  │                 ^ Unused assignment or binding for local 'f'. Consider removing, replacing with '_', or prefixing with '_' (e.g., '_f')