Formatter Breaks Code When Using {_} in Pattern Matching

[namenu]

The following code demonstrates the issue:

  switch u {
  | {_} => Js.log("matched")
  }

When running the formatter on this code, it transforms the code into:

  switch u {
  | {, _} => Js.log("matched")
  }

This leads to a syntax error; see playground

It is unclear whether the original syntax {_} should be considered valid. If {_} is invalid syntax, the compiler should raise an error for the original code before formatting occurs.