Comment #0 by bearophile_hugs — 2013-02-05T16:55:27Z
See the thread:
http://forum.dlang.org/thread/[email protected]
That is about the article:
http://electronicdesign.com/contributing-technical-experts/contract-driven-programming-takes-specification-beyond-stone-age
It contains:
<<
In Ada 2012, predicates on a type (one particular type of invariant) are checked on parameter passing and assignment. So if we have Code 4, there will be a check failure on the assignment, since the predicate is not true. No check is generated on individual field modifications, though, so Code 5 does not raise an exception.
>>
http://electronicdesign.com/site-files/electronicdesign.com/files/uploads/2013/02/0307RequiemCode4.gifhttp://electronicdesign.com/site-files/electronicdesign.com/files/uploads/2013/02/0307RequiemCode5.gif
This D code doesn't asserts (unlike equivalent in Ada2011):
struct Foo {
int x = 200;
invariant() { assert(x > 100); }
}
void main() {
auto f = Foo(10);
}
So maybe it's a good to introduce in D as in Ada a call to the invariant when the whole struct is assigned.
Another case:
<<
Although the assignment to the V fields breaks the invariant [figure 5], no exception is raised on these two statements. Thankfully, as soon as a call using V as a parameter is done, a subtype check will occur and the inconsistency will be pointed out. Hopefully, this will not be too far from the introduction of the problem.
>>
Currently D doesn't call the invariant even in that second case too:
struct Foo {
int x = 200;
invariant() { assert(x > 100); }
}
void bar(Foo f) {}
void main() {
auto f = Foo(10);
bar(f);
}
Comment #1 by bearophile_hugs — 2013-02-06T03:19:30Z
Discussion thread:
http://forum.dlang.org/thread/[email protected]
This is a similar issue:
http://d.puremagic.com/issues/show_bug.cgi?id=519
They are very similar, the test case from Issue 519 uses a new:
class Foo {
invariant() {
assert (false);
}
}
void main() {
Foo foo = new Foo();
}
While in Issue 9454 (just like in that Ada code) there is no new:
struct Foo {
int x = 200;
invariant() { assert(x > 100); }
}
void main() {
auto f = Foo(10);
}
Comment #2 by robert.schadek — 2024-12-13T18:03:57Z