I don't know what version of gedit you're using, but
https://github.com/JMoerman/valencia-1 works for me. (I'm using gedit
3.10)
I'll second this. Gedit + Valencia have worked very nicely for me.
It's true that there hasn't been much development of Valencia
recently, but I've found it doe
Valencia isn't limited to vala 0.24 (I've only used it with >= 0.28), you
can build it for 0.30 by running "LIBVALA=libvala-0.30 make" (or by
modifying the Makefile).
That error probably isn't related to Valencia, I mentioned that I'm using
Gedit 3.10 because I simply don't know if it will compile
