Resolving dependencies...
Configuring mtl-2.2.1...
Building mtl-2.2.1...
Installed mtl-2.2.1
Configuring sessions-2007.6.14...
Building sessions-2007.6.14...
Failed to install sessions-2007.6.14
Build log ( /home/builder/.cabal/logs/sessions-2007.6.14.log ):
cabal: Entering directory '/tmp/cabal-tmp-3735/sessions-2007.6.14'
[1 of 1] Compiling Main             ( /tmp/cabal-tmp-3735/sessions-2007.6.14/dist/setup/setup.hs, /tmp/cabal-tmp-3735/sessions-2007.6.14/dist/setup/Main.o )
Linking /tmp/cabal-tmp-3735/sessions-2007.6.14/dist/setup/setup ...
Configuring sessions-2007.6.14...
Warning: No 'build-type' specified. If you do not need a custom Setup.hs or
./configure script then use 'build-type: Simple'.
Building sessions-2007.6.14...
Preprocessing library sessions-2007.6.14...

Control/Concurrent/Session/BaseClasses.hs:20:16: warning:
    -fglasgow-exts is deprecated: Use individual extensions instead

Control/Concurrent/Session/BaseClasses.hs:20:16: warning:
    -fallow-undecidable-instances is deprecated: use -XUndecidableInstances or pragma {-# LANGUAGE UndecidableInstances #-} instead

Control/Concurrent/Session/BaseClasses.hs:20:16: warning:
    -fallow-overlapping-instances is deprecated: use -XOverlappingInstances or pragma {-# LANGUAGE OverlappingInstances #-} instead

Control/Concurrent/Session/BaseTypes.hs:20:16: warning:
    -fglasgow-exts is deprecated: Use individual extensions instead

Control/Concurrent/Session/Choice.hs:20:16: warning:
    -fglasgow-exts is deprecated: Use individual extensions instead

Control/Concurrent/Session/Choice.hs:20:16: warning:
    -fallow-undecidable-instances is deprecated: use -XUndecidableInstances or pragma {-# LANGUAGE UndecidableInstances #-} instead

Control/Concurrent/Session/ExtraClasses.hs:20:16: warning:
    -fglasgow-exts is deprecated: Use individual extensions instead

Control/Concurrent/Session/List.hs:20:16: warning:
    -fglasgow-exts is deprecated: Use individual extensions instead

Control/Concurrent/Session/List.hs:20:16: warning:
    -fallow-undecidable-instances is deprecated: use -XUndecidableInstances or pragma {-# LANGUAGE UndecidableInstances #-} instead

Control/Concurrent/Session/Loop.hs:20:16: warning:
    -fglasgow-exts is deprecated: Use individual extensions instead

Control/Concurrent/Session/Loop.hs:20:16: warning:
    -fallow-undecidable-instances is deprecated: use -XUndecidableInstances or pragma {-# LANGUAGE UndecidableInstances #-} instead

Control/Concurrent/Session/Loop.hs:20:16: warning:
    -fallow-overlapping-instances is deprecated: use -XOverlappingInstances or pragma {-# LANGUAGE OverlappingInstances #-} instead

Control/Concurrent/Session/Runtime.hs:20:16: warning:
    -fglasgow-exts is deprecated: Use individual extensions instead

Control/Concurrent/Session/Runtime.hs:20:16: warning:
    -fallow-undecidable-instances is deprecated: use -XUndecidableInstances or pragma {-# LANGUAGE UndecidableInstances #-} instead

Control/Concurrent/Session/Runtime.hs:20:16: warning:
    -fallow-overlapping-instances is deprecated: use -XOverlappingInstances or pragma {-# LANGUAGE OverlappingInstances #-} instead

Control/Concurrent/Session/State.hs:20:16: warning:
    -fglasgow-exts is deprecated: Use individual extensions instead
[1 of 9] Compiling Control.Concurrent.Session.List ( Control/Concurrent/Session/List.hs, dist/build/Control/Concurrent/Session/List.o )

Control/Concurrent/Session/List.hs:25:1: error:
    • Illegal generalised algebraic data declaration for ‘List’
        (Use GADTs to allow GADTs)
    • In the data declaration for ‘List’
cabal: Leaving directory '/tmp/cabal-tmp-3735/sessions-2007.6.14'
cabal: Error: some packages failed to install:
sessions-2007.6.14 failed during the building phase. The exception was:
ExitFailure 1