funky span ranges

[twicedo]

for string " fn aa"
lexer generates

  [Annot{
      value: Fn,
      loc: Loc {
          f: 4,
          e: 6,
      },
  },
  Annot{
      value: Ident(
          "aa",
      ),
      loc: Loc {
          f: 5,
          e: 8,
      },
  },]
] 

aren't the ranges are overlapping (4,6) and next (5,8)