A little while ago I was contacted about a new merge tool from the company behind PlasticSCM. (I haven’t used Plastic myself, but I’d heard of it.) My initial reaction was that I wasn’t interested in anything which required me to learn yet another source control system, but SemanticMerge is independent of PlasticSCM.
My interested was piqued when I learned that SemanticMerge is actually built on Roslyn. I don’t generally care much about implementation details, but I’m looking out for uses of Roslyn outside Microsoft, partly to see if I can gain any inspiration for using it myself. Between the name and the implementation detail, it should be fairly obvious that this is a tool which understands changes in C# source code rather better than a plain text diff.
I’ve had SemanticMerge installed on one of my laptops for a month or so now. Unfortunately it’s getting pretty light use – my main coding outside work is on Noda Time, and as I perform the vast majority of the commits, the only time I really need to perform merges is when I’ve forgotten to push a commit from one machine before switching to another. I’ve used it for diffs though, and it seems to be doing the right thing there – showing which members have been added, moved, changed etc.
I don’t believe it can currently support multi-file changes – for example, spotting that a lot of changes are all due to a rename operation – but even if it doesn’t right now, I suspect that may be worked on in the future. And of course, the merge functionality is the main point.
SemanticMerge is now in beta, so pop over to the web site and give it a try.
Jon Skeet's coding blog 
Recently I have been interested in Roslyn, and I’m amazed about the possibilities it offers. I have in mind some search integrated in visual studio. But with semantics. R# have a little in that direction, but I think I can go way deeper.
So this one is a really awesome idea of a product. Will try to tell my comrades to use it.
By the way. Awesome book (C# in depth 3rd ed. MEAP) :)
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If you’re looking for novel uses for Roslyn then I’d recommend using it as a code re-writing tool.
I used it do a large refactoring over 200 files. The change involved removing about 4 properties including regions and comments, inheriting from a newly created base class and passing the value of those 4 properties into the constructor for the base class.
There were a few edge cases that it didn’t catch but it did the bulk of the work and I cleaned up the remaining code by hand.
If you were really ambitious I’m sure you could use it to implement a kind of compile time AOP (inserting the AOP stuff in code rather than in CIL) but I haven’t had a need for doing that so I haven’t looked at it.
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Skeet please do blog more, you’re a huge inspiration for a lot of us, I’ve read your awesome book and watched the tekpub vids and learned so much. Keep up the good work.
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