Assertion failure when implicit argument of annotation can't be deduced

[TWal]

See the code below:

let test_annot (#a:Type0) (x:int) = ()

type test_type = {
  [@@@ test_annot 1337]
  x: int;
}

It gives the following error:

ASSERTION FAILURE: (<input>(6,7-6,17)) CheckNoUvars: Unexpected unification variable remains: (*?u3*) _
F* may be in an inconsistent state.
Please file a bug report, ideally with a minimized version of the program that triggered the error.