| Where do I put -fno-ds-multi-tyvar so that the build system knows to use | it? I'm going to try build.mk. | | Ok that didn't work and I couldn't find anything about | -fno-ds-multi-tyvar in the documentation. Yes, in GhcLibHcOpts in build.mk is a good place. The flag isn't documented because it's a debug-only flag that I threw in so that I can measure the effect of this particular desugaring change. It's not really intended for users -- hard to explain just what it does. In any case I'm just about to push a patch which fixes the original problem and makes the flag unnecessary for your purposes. | The reason I'm compiling rather than installing is because I want to use | NDP. Great! I'm copying Roman, Gabi, and Manuel so they know you're doing this. Much of GHC is very stable but NDP emphatically isn't. We're working hard on it, the code is changing a lot, so you may well get short-lived build difficulties. So do have a go, but show us your code, and keep us in touch with what happens. Simon