cabal install hoogle error - BuilderResponse missing

Question

Warning: new Haskell user here

I'm trying to install the CLI version of Hoogle to follow along with a tutorial. I'm seeing the following on Haskell Platform 2013.2.0.0 for Mac OS X, 64 bit.

Other info: ~/Library/Haskell/bin is in my path. alex and happy (and wai, where I think BuilderResponse is actually defined) are installed. This isn't the transcript from the original installation (which installed a ton of stuff before failing), but it's where I'm at now. For giggles, I tried the same thing on Fedora 19 (X86_64) and it fails similarly so I don't think it's Mac-specific.

% cabal update
Downloading the latest package list from hackage.haskell.org
% cabal -V
cabal-install version 1.18.0.2
using version 1.18.1.2 of the Cabal library 
% cabal install hoogle
Resolving dependencies...
Configuring hoogle-4.2.23...
Building hoogle-4.2.23...
Preprocessing library hoogle-4.2.23...
[ 1 of 46] Compiling Paths_hoogle     ( dist/build/autogen/Paths_hoogle.hs, dist/build/Paths_hoogle.o )
[ 2 of 46] Compiling Data.TypeMap     ( src/Data/TypeMap.hs, dist/build/Data/TypeMap.o )
[ 3 of 46] Compiling Data.Heap        ( src/Data/Heap.hs, dist/build/Data/Heap.o )
[ 4 of 46] Compiling Hoogle.Score.Type ( src/Hoogle/Score/Type.hs, dist/build/Hoogle/Score/Type.o )
[ 5 of 46] Compiling Hoogle.Score.Scoring ( src/Hoogle/Score/Scoring.hs, dist/build/Hoogle/Score/Scoring.o )
[ 6 of 46] Compiling Hoogle.Score.All ( src/Hoogle/Score/All.hs, dist/build/Hoogle/Score/All.o )
[ 7 of 46] Compiling General.Base     ( src/General/Base.hs, dist/build/General/Base.o )
[ 8 of 46] Compiling General.System   ( src/General/System.hs, dist/build/General/System.o )
[ 9 of 46] Compiling Hoogle.Type.Language ( src/Hoogle/Type/Language.hs, dist/build/Hoogle/Type/Language.o )
[10 of 46] Compiling General.Util     ( src/General/Util.hs, dist/build/General/Util.o )
[11 of 46] Compiling General.Web      ( src/General/Web.hs, dist/build/General/Web.o )

src/General/Web.hs:44:19:
    Not in scope: data constructor `ResponseBuilder'
Failed to install hoogle-4.2.23
cabal: Error: some packages failed to install:
hoogle-4.2.23 failed during the building phase. The exception was:
ExitFailure 1

Answer 1

It looks like Neil hasn't updated hoogle to work with the latest wai package. The short-term solution is to force cabal to select an older version of the offending package (wai):

cabal install hoogle --constraint='wai<2.0'

EDIT: Note wai 2.0 was released just 4 days ago and hackage doesn't proactively inform developers about breakage, so this isn't really surprising.