When trying to build darcs with ghc-7.8.2 I get following error:

    Resolving dependencies...
    cabal: Could not resolve dependencies:
    trying: darcs-2.8.4 (user goal)
    trying: random-1.0.1.1 (dependency of darcs-2.8.4)
    trying: time-1.4.2/installed-b47... (dependency of random-1.0.1.1)
    next goal: deepseq (dependency of time-1.4.2/installed-b47...)
    rejecting: deepseq-1.3.0.2/installed-716... (conflict: deepseq =>
    array==0.5.0.0/installed-9f2..., darcs => array>=0.1 && <0.5)
    rejecting: deepseq-1.3.0.2, 1.3.0.1, 1.3.0.0, 1.2.0.1, 1.2.0.0, 
1.1.0.2,
    1.1.0.1, 1.1.0.0, 1.0.0.0 (conflict: time =>
    deepseq==1.3.0.2/installed-716...)
    Dependency tree exhaustively searched.

    Note: when using a sandbox, all packages are required to have 
consistent
    dependencies. Try reinstalling/unregistering the offending packages 
or
    recreating the sandbox.

This is resolved in darcs HEAD and in the 2.8.4 release.