To compile the examples some modules of the library HList have to be exposed.
The following is an example of a file "HList.cabal" which makes the examples work:

Name:                HList
Version:             0.1
Category:            Data
Synopsis:            Heterogeneous lists
Description:         HList is a record system providing strongly typed heterogenous lists, records,
                     type-indexed products (TIP) and co-products; licensed under the MIT X License.
License:             OtherLicense
License-File:        LICENSE
Author:              2004 Oleg Kiselyov (FNMOC, Monterey), Ralf Laemmel (CWI/VU, Amsterdam),
                     Keean Schupke (Imperial College, London)
Maintainer:          oleg@pobox.com

Tested-With:         GHC==6.8.2
Build-Depends:       base, template-haskell
Build-Type:          Simple
Exposed-modules:     Data.HList, Data.HList.Label4, Data.HList.Record, Data.HList.TypeCastGeneric1, 
                     Data.HList.FakePrelude, Data.HList.TypeEqGeneric1, Data.HList.MakeLabels
Other-modules:       Data.HList.CommonMain, Data.HList.Variant, Data.HList.GhcSyntax,
                     Data.HList.GhcRecord,Data.HList.HZip, Data.HList.TIC, Data.HList.TIP,
                     Data.HList.HTypeIndexed, Data.HList.HOccurs, Data.HList.HArray, Data.HList.GhcExperiments,
                     Data.HList.HListPrelude, Data.HList.TypeEqBoolGeneric

extensions:          EmptyDataDecls, FlexibleContexts, FlexibleInstances, FunctionalDependencies,
                     MultiParamTypeClasses, OverlappingInstances, PatternSignatures, RankNTypes,
                     ScopedTypeVariables, TypeSynonymInstances, UndecidableInstances
ghc-options:         -O2 -Wall