[Haskell-cafe] GHC and backwards compatibility

[Ketil Malde]

I recently encountered the following problem:

--------------------------------------------------------------------------------
$ cabal install
Resolving dependencies...
Configuring array-0.4.0.1...
Building array-0.4.0.1...
Preprocessing library array-0.4.0.1...

Data/Array/IArray.hs:1:14: Unsupported extension: Trustworthy
cabal: Error: some packages failed to install:
array-0.4.0.1 failed during the building phase. The exception was:
ExitFailure 1
asmeval-0 depends on array-0.4.0.1 which failed to install.
binary-0.7.1.0 depends on array-0.4.0.1 which failed to install.
biocore-0.3.1 depends on array-0.4.0.1 which failed to install.
biofasta-0.0.3 depends on array-0.4.0.1 which failed to install.
biopsl-0.4 depends on array-0.4.0.1 which failed to install.
biosff-0.3.3 depends on array-0.4.0.1 which failed to install.
bytestring-0.10.2.0 depends on array-0.4.0.1 which failed to install.
containers-0.5.2.1 depends on array-0.4.0.1 which failed to install.
deepseq-1.3.0.1 depends on array-0.4.0.1 which failed to install.
hashable-1.2.0.10 depends on array-0.4.0.1 which failed to install.
stringable-0.1.1 depends on array-0.4.0.1 which failed to install.
system-filepath-0.4.7 depends on array-0.4.0.1 which failed to install.
text-0.11.3.1 depends on array-0.4.0.1 which failed to install.
unordered-containers-0.2.3.1 depends on array-0.4.0.1 which failed to install.
--------------------------------------------------------------------------------

The installed GHC is 7.0.4, and yes, that's many major versions ago, but
then again, it's only two years old, and from what I understand, it is
shipped by some conservative Linux distributions.

The problems here are that:

a) the installation tries to install array, but current array requires
the "Trustworthy" extension, which appeared in 7.2.1.  Ideally, packages
should try to be backwards compatible, e.g. by using conditional
sections.

b) the output isn't very helpful in tracking down the cause of this
problem, it claims that all these packages depend on array-0.4.0.1,
which is a lie.  Somewhere, somehow, somethings depends on this (or at
least a newer version), but I have no clue how to figure out which,
except examining each of these packages and their dependencies manually.
 
It is also possible that array shouldn't be upgraded like this, but then
that needs to be made clear to cabal somehow, so that I don't spend ages
trying to.

Are there any solutions to this?  Advice on how to proceed?

-k
-- 
If I haven't seen further, it is by standing in the footprints of giants