Function parse_case 

pub fn parse_case(
    input: Cid,
    defs: Rc<RefCell<Defs>>,
    rec: Option<Name>,
    ctx: Ctx,
    quasi: Rc<VecDeque<Term>>,
) -> impl Fn(Span<'_>) -> IResult<Span<'_>, Term, ParseError<Span<'_>>>

Parses a self type destructor