Fixing Bugs: D/Phobos
A large part of open development is giving back to projects that you use.
As a semicasual D programmer, I jumped at the opportunity to get class credit for using it. The HFOSS course has an assignment that requires us to submit a (reasonable) pull request to an open source project. After browsing through the bugs, I discovered Issue 4391. Due to my recent adventures with functional programming, I figured that it would be an exciting request to try.
That was when the compiler attacked.
One of my largest complaints with DMD and D compilers in general is that some things that “should work” seem to break for strange reasons. In this case, I admit that my code was a slight edge case, but still relevant.
Deriving some of the code from Philippe Sigaud in the issue, I set forth to create a slightly more modern implementation. There were a few issues I had with the initial code:
Init!Tdoesn’t exist, but
T.initworks for these purposes
- Several helpers that seemed to just clutter the namespace
- Uses string mixins, which I felt were overkill for this situation (templates are sufficient)
I was able to get the code mostly working, thanks in part to the sample code and leveraging
std.functional.partial, except for one irritating edge case:
- A templated delegate
- Within a unittest or function
- That isn’t marked as static
Removing the template, or marking it as static, or moving it outside the unittest, makes everything work cleanly. Despite double-checking with a couple of other D developers, it appeared that this wasn’t an issue with my code directly, but rather relating to the context pointer and where templates are instantiated.
My pull request, therefore, was reduced to “rename and fix documentation for curry”, so that it has a name that matches what it actually DOES - partial application. I left a
deprecated alias curry = partial in the code (with documentation) to preserve backwards compatibility, in the hopes that if/when I can complete the FULL intended pull, the name change won’t be as complex.