On Wednesday, 13 May 2015 at 10:18:26 UTC, iackhtak wrote:
There was discussion about broken contract programing. Broken
thing was "in" contract within inheritance. If you add
different "in"-contract in overridden parent and derived
function only one will be checked.
I thought that solution is to ban "in"-contract for derived
function. "In"-contract says what you can pass. If you want to
accept input without any constraints you can't add new
constraint in inherited stuff because your inherited stuff can
by used in any context where base thing can. Within this
context any arguments can be passed. This way adding new
constraints on input brakes Liskov substitution principle and
have to be banned.
Theoretically it can be allowed to loose contract(and extend
interface) but the thing looks hard to implement.
Conversely "out" can be narrowed without any restrictions.
Wrong thread, sorry
