There are 'interface' files in D, too. They are rarely used and usually auto-generated by the compiler, but similar to header files in C. There is no syntactical difference in the content of .di compared to .d, so it can be added as an additional extension to the same mime type. Information: http://dlang.org/dmd-linux.html#interface_files
commit b1b4439904f534059f947e8f2503458ea0951738 Author: Bastien Nocera <hadess@hadess.net> Date: Tue Feb 12 15:29:10 2013 +0100 Add *.di as a glob for D interface source files https://bugs.freedesktop.org/show_bug.cgi?id=60605
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