Hi,

for the attached code I noticed some strange behaviors.
I compile the programm with: dmd main -unittest
The expected assertion of the method c pre condition is
not raised.
It is only raised if class A not implements interface I.

On the otherside the commented assertion in the invariant is working
fine.

Is this a bug?

Kind regards
André


interface I {
	void c();
}

class A : I {
	invariant() {
		//assert(false, "Assert INVARIANT"); // Working
	}

	void c()
	in {
		assert(false, "Assert IN");
	}
	body {

	}
}

unittest {
	A a = new A();
	a.c();
}

void main(){}

On Friday, 23 May 2014 at 13:45:07 UTC, Andre wrote:
> Hi,
>
> for the attached code I noticed some strange behaviors.
> I compile the programm with: dmd main -unittest
> The expected assertion of the method c pre condition is
> not raised.
> It is only raised if class A not implements interface I.
>
> On the otherside the commented assertion in the invariant is working
> fine.
>
> Is this a bug?
>
> Kind regards
> André
>
>
> interface I {
> 	void c();
> }
>
> class A : I {
> 	invariant() {
> 		//assert(false, "Assert INVARIANT"); // Working
> 	}
>
> 	void c()
> 	in {
> 		assert(false, "Assert IN");
> 	}
> 	body {
>
> 	}
> }
>
> unittest {
> 	A a = new A();
> 	a.c();
> }
>
> void main(){}

I'm not sure. An implementation shouldn't be allowed to have stricter pre-conditions than it's base class or interface. On the other hand it should be able to relax them.

Am 23.05.2014 16:34, schrieb Rene Zwanenburg:
> On Friday, 23 May 2014 at 13:45:07 UTC, Andre wrote:
>> Hi,
>>
>> for the attached code I noticed some strange behaviors.
>> I compile the programm with: dmd main -unittest
>> The expected assertion of the method c pre condition is
>> not raised.
>> It is only raised if class A not implements interface I.
>>
>> On the otherside the commented assertion in the invariant is working
>> fine.
>>
>> Is this a bug?
>>
>> Kind regards
>> André
>>
>>
>> interface I {
>>     void c();
>> }
>>
>> class A : I {
>>     invariant() {
>>         //assert(false, "Assert INVARIANT"); // Working
>>     }
>>
>>     void c()
>>     in {
>>         assert(false, "Assert IN");
>>     }
>>     body {
>>
>>     }
>> }
>>
>> unittest {
>>     A a = new A();
>>     a.c();
>> }
>>
>> void main(){}
>
> I'm not sure. An implementation shouldn't be allowed to have stricter
> pre-conditions than it's base class or interface. On the other hand it
> should be able to relax them.

In case there is a reason that the assertion is not run,
if feels very dangerous for me that all assertions can be
disabled by mistake just by adding an interface to a class.

At least a compiler messsage should be thrown to warn about
"useless" assertions

Kind regards
André

On Friday, 23 May 2014 at 14:38:27 UTC, Andre wrote:
> Am 23.05.2014 16:34, schrieb Rene Zwanenburg:
> In case there is a reason that the assertion is not run,
> if feels very dangerous for me that all assertions can be
> disabled by mistake just by adding an interface to a class.
>
> At least a compiler messsage should be thrown to warn about
> "useless" assertions
>
> Kind regards
> André

I completely agree. A quick search on the issue tracker shows there are some serious bugs involving in contracts and interfaces[0]. It's probably best to keep away from them until the situation improves.

[0]: https://issues.dlang.org/buglist.cgi?quicksearch=in%20contract%20interface

Am 23.05.2014 16:44, schrieb Rene Zwanenburg:
> On Friday, 23 May 2014 at 14:38:27 UTC, Andre wrote:
>> Am 23.05.2014 16:34, schrieb Rene Zwanenburg:
>> In case there is a reason that the assertion is not run,
>> if feels very dangerous for me that all assertions can be
>> disabled by mistake just by adding an interface to a class.
>>
>> At least a compiler messsage should be thrown to warn about
>> "useless" assertions
>>
>> Kind regards
>> André
>
> I completely agree. A quick search on the issue tracker shows there are
> some serious bugs involving in contracts and interfaces[0]. It's
> probably best to keep away from them until the situation improves.
>
> [0]:
> https://issues.dlang.org/buglist.cgi?quicksearch=in%20contract%20interface

): I found my issue: https://issues.dlang.org/show_bug.cgi?id=12321

I just think about whether it is possible to build a contracts library
similiar to C4J (Contracts 4 Java).
I like the classed based approach.

Kind regards
André