Where to find source code for android `dx` tool, version 1.16?

Question

googling "dx source code" gives this but it's version 1.7.

By going up the path, I can find later versions of the entire platform (it seems), but not clear to me which one contains which versions of dx. I could trial-and-error to find it, but there'a got to be a better way!

I found version 1.16 here at jar-download.com but I don't know if it's legit (I could theoretically hand-check it all...). It doesn't seem related to google. EDIT This turned out to be just the class files, no java source.