Resolving dependencies...
Configuring HMap-0.902...
Building HMap-0.902...
Preprocessing library HMap-0.902...
[1 of 1] Compiling Data.HMap        ( Data/HMap.hs, dist/build/Data/HMap.o )

Data/HMap.hs:171:1:
    ‘T’ has no constructors (EmptyDataDecls permits this)
    In the data declaration for ‘T’
Failed to install HMap-0.902
cabal: Error: some packages failed to install:
HMap-0.902 failed during the building phase. The exception was:
ExitFailure 1