On Fri, 01 Jul 2011 02:39:29 -0400, Jens Mueller <jens.k.muel...@gmx.de>
wrote:
Robert Jacques wrote:
On Thu, 30 Jun 2011 06:42:57 -0400, Jens Mueller
<jens.k.muel...@gmx.de> wrote:
>bearophile wrote:
>>Jens Mueller:
>>
>>> unittest {
>>> class Base {
>>> void foo(uint i)
>>> in { assert(i <= 10); }
>>> body { }
>>> }
>>>
>>> class Sub : Base {
>>> override void foo(uint i)
>>> in { assert(i <= 5); } // fails to require less
>>but I won't know
>>> body
>>> {
>>> assert(i <= 5); // fails here because in contract
>>wasn't checked
>>> }
>>> }
>>>
>>> auto s = new Sub;
>>> //s.foo(10); // fails as expected
>>> s.foo(7); // due to shortcut evaluation of in contracts
>>this call passes all contracts
>>> }
>>
>>I think it's a DMD bug, fit for Bugzilla if not already present.
>
>The shortcut evaluation is specified in TDPL. That's why I assume the
>behavior is intended.
>
>Jens
A subclass must be able to handle all the inputs the base class
accepts, otherwise it isn't true polymorphism anymore. Not being
able to use Sub where Base is expected, and maybe only Base was
tested, can lead to major bugs.
So you agree that the current behavior is error-prone?
No. I think the current behavior is correct. In fact, if anything, D
shouldn't allow you to define an in contract on any override method. A Sub
is a Base and therefore must be able to handle all inputs that are valid
for a Base.
