Re: Design by Contract

On Wed, Feb 11, 2015 at 10:58 AM, Stanislav Malyshev <smalyshev@gmail.com> wrote: > Hi! > > > 1) contracts in doc-commetns https://wiki.php.net/rfc/dbc > > > > /** > > * @requires ($a >= 0) > > */ > > function foo($a) { > > } > > We've spent several years rejecting annotations because no information > can be in comments, not even a little bit, not even a tiny. Now we'd > have full-blown running code in comments? How would this code be > debugged/profiled/interpreted by tools? Writing PHP parser is not easy > right now, but this would turn it into nightmare (what if you have a > comment inside @requires? etc.) > I don't see how this can be implemented in PHP core as well. This approach is for external tools. > > > 2) contracts as part of the language > > https://wiki.php.net/rfc/dbc2 > > > > function foo($a) > > require($a >= 0) > > { > > } > > This is a step better but still we have the similar issues with > readability, to which reuse of 'require' is added. > > > 3) contracts in annotations > > > > <<requires($a >= 0)>> > > function foo($a) { > > } > > That one actually looks better to me, but: I'm not sure how annotation > syntax is supposed to support expressions or closures, keep AST. > yet more - how it > is supposed to share the scope with the function. I.e., if you define > annotation class/method/function/data structure/whatever it is, what it > is supposed to receive? We may have AST transformation pass that would convert these annotations into assert() and insert them into AST of the function. > Is it some special form of annotation for this > purpose only (meh)? > yes. some special attributes. requires/ensures/invariant > Oh, and <<>> syntax is *ugly* ;) > It's from HHVM. I don't like it as well, please, propose the better one. Thanks. Dmitry. > > -- > Stas Malyshev > smalyshev@gmail.com >