This grammar has a conflict with three possible actions: a shift in the middle of the `binary` rule and two reductions: one for `unary_a` and one for `unary_b`. Both `unary_a` and `unary_b` have a higher precedence than `binary`, therefore we can rule out the interpretation where a `binary` occurs *inside* of a `unary_a` or `unary_b`, so the error message (and suggested `conflict`) should not include that interpretation.