I'm able to reproduce the following with a freshly cloned Propellor:

    > stack build
    propellor-5.3.5: build (lib + exe)
    Preprocessing library propellor-5.3.5...
    [ 43 of 171] Compiling Propellor.Types  ( src/Propellor/Types.hs, .stack-work/dist/x86_64-linux-nopie/Cabal-1.24.2.0/build/Propellor/Types.o )

    /home/jayess/code/propellor/src/Propellor/Types.hs:251:37: error:
        • Could not deduce (Monoid (Property setupmetatypes))
            arising from a use of ‘<>’
          from the context: (Sem.Semigroup (Property setupmetatypes),
                             Sem.Semigroup (Property undometatypes))
            bound by the instance declaration
            at src/Propellor/Types.hs:(245,9)-(248,74)
        • In the first argument of ‘RevertableProperty’, namely
            ‘(s1 <> s2)’
          In the expression: RevertableProperty (s1 <> s2) (u2 <> u1)
          In an equation for ‘<>’:
              (RevertableProperty s1 u1) <> (RevertableProperty s2 u2)
                = RevertableProperty (s1 <> s2) (u2 <> u1)

    /home/jayess/code/propellor/src/Propellor/Types.hs:251:48: error:
        • Could not deduce (Monoid (Property undometatypes))
            arising from a use of ‘<>’
          from the context: (Sem.Semigroup (Property setupmetatypes),
                             Sem.Semigroup (Property undometatypes))
            bound by the instance declaration
            at src/Propellor/Types.hs:(245,9)-(248,74)
        • In the second argument of ‘RevertableProperty’, namely
            ‘(u2 <> u1)’
          In the expression: RevertableProperty (s1 <> s2) (u2 <> u1)
          In an equation for ‘<>’:
              (RevertableProperty s1 u1) <> (RevertableProperty s2 u2)
                = RevertableProperty (s1 <> s2) (u2 <> u1)

    --  While building package propellor-5.3.5 using:
          /home/jayess/.stack/setup-exe-cache/x86_64-linux-nopie/Cabal-simple_mPHDZzAJ_1.24.2.0_ghc-8.0.2 --builddir=.stack-work/dist/x86_64-linux-nopie/Cabal-1.24.2.0 build lib:propellor exe:propellor exe:propellor-config --ghc-options " -ddump-hi -ddump-to-file"
        Process exited with code: ExitFailure 1
