Oh, I incorrectly assumed that the failure has anything to do with your overriding. But if you do
$ nix-build -E "with (import <nixpkgs> {}); with haskell.lib; dontCheck (haskell.packages.ghc801.comonad)" that does fail in the same way, so in fact the overriding is not related at all to the issue your encountering here. Since transformers is a library that is shipped with GHC itself, it's ok for it to not be in the dependencies of the comonad derivation. What really happens is that cabal's error message is a little bit bad in this case: it says that it can't find a package transformers *that matches the given version bounds*. There actually *is* a transformers package available at the build time of comonad, it's just that GHC 8.0 ships with `transformers-0.5.*`, which lies outside of the version bounds specified in comonad's cabal file. So the issue is not that `transformers` is missing, but rather that the ghc-provided version is too new for `comonad`. You can verify that by dropping into the nix-shell for the `ghc-8.0` package (that's how I've found out that transformers is indeed shipped with ghc): $ nix-shell --pure -p haskell.compiler.ghc801 --command "env TERM=xterm ghc-pkg list transformers" /nix/store/0ymhbixr9hdmr3sls7mn3qc6vb10kb8a-ghc-8.0.0.20160204/lib/ghc-8.0.0.20160204/package.conf.d transformers-0.5.1.0 [I hope my analysis is correct this time :D unfortunately, it seems that in the version of nixpkgs that I am using, I can't even get as far as build comonad: some dependencies before that already fail to build for me] To fix the issue, you can try overriding the `comonad` package to allow newer transformers versions: (no idea if comonad builds/works with newer transformers though as-is or if it needs additional patches by the maintainers first): comonad = doJailbreak old.comonad # add this line to your overrides Kosyrev Serge <_deepf...@feelingofgreen.ru> schrieb am So., 21. Feb. 2016 um 20:38 Uhr: > Benno Fünfstück <benno.fuenfstu...@gmail.com> writes: > > Oops, small to the code example: the line should be `let parent = > > (oldArgs.overrides or (_: _: {})) new old` (new instead of parent in > > the second to last word) > > Benno, thank you a lot for responding! > > Unfortunately it still doesn't work, for some reason, in the same way. > > In case you or anyone feels like taking a look -- I have posted the nix > expression at: > > https://gist.github.com/deepfire/e455da624417acc3091f > > -- > с уважениeм / respectfully, > Косырев Сергей >
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