consistently discard return value of constructors

[ynniv]

As per #1269, the return value of constructors should be discarded.

[ryanflorence]

Inverse pull request at #1435

[jashkenas]

I'm not sure about the semantics of the code in this pull request. I'd be glad to take a closer look at it with an accompanying test that demonstrates the desired change in behavior.

[ynniv]

You're just closing out old pull requests, and after much discussion regarding the return value of constructors, I just don't care anymore. If you truly believe that people should not return values from constructors, you should apply this patch to prevent people from returning values from a "constructor" attribute, which is currently capable of changing the value of the object being constructed.

[jashkenas]

I truly believe that folks shouldn't return "other" values from constructors, but I also believe that we shouldn't be inserting an extra function wrapper around your constructor just to force the issue. This isn't "nanny-state" programming ;)

[ynniv]

Look, I spent considerable time lobbying for ynniv@4d03d09, and wherever that change has arisen (#1269 #1216 and #1094) you have told people that they should not return values from constructors. So either you believe that the framework should explicitly prevent people from returning constructor values or not, but please be consistent.