Hi Simon,
my first guess is that: when working on the unsaturated type families
paper, you did `cabal install --lib report`; or something similar.
`report` is probably some internal library to that paper / project.
In that case, you are hitting the unfortunate cabal bug [1].
To confirm, check what is in your
~/.ghc/x86_64-linux-8.6.5/environments/default (or similar), is some
`package-id report-0.1.0.0-hexhash` line there? If so, the simplest fix
is to remove that environment file.
- [1] https://github.com/haskell/cabal/issues/5888
https://github.com/haskell/cabal/issues/5559
Cheers,
Oleg
On 30.5.2019 16.50, Simon Peyton Jones wrote:
Dear friendly Cabal folk
Here’s what happened to me today
bash$ cabal install lhs2tex
cabal: Could not resolve dependencies:
[__0] next goal: report (user goal)
[__0] rejecting: report-0.1.0.0 (conflict: requires
UnsaturatedTypeFamilies)
[__0] fail (backjumping, conflict set: report)
After searching the rest of the dependency tree exhaustively, these
were the
goals I've had most trouble fulfilling: report
Crumbs. What is ‘report’? Why does it need
UnsaturatedTypeFamilies? I’m totally lost.
Then, in an inspired moment, I thought to change to a different
directory, ~/tmp.
Then quite different things happened – it downloaded and built
relevant libraries.
I think that there just happened to be a .cabal file in the original
directory I was in at the time. That appears to affect what ‘cabal
install’ does in a truly radical way.
My point is this: this is terribly confusing for the user (at least
for this on). I’d be shocked if ‘apt install blah’ behaved utterly
differently in different directories. I’m going to make a little
empty directory somewhere, and cd to it before invoking cabal in
future. But that just feels like a workaround, not a solution.
I’m not saying it’s wrong – just giving you a data point that it had
one user completely stumped
Simon
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