output

# zachchurchill @ developer1 in ~/Documents/grove/backend/service on git:master x [10:15:21] 
> nix-shell --run 'ghcid -c cabal new-repl'
these derivations will be built:
  /nix/store/wl7s679ap53p8nv7fgk3x3dk81zb4mj3-beam-migrate-0.3.2.1.drv
  /nix/store/5c2lwzjcqr7cd5kgdb3d5n8i89g763wk-beam-postgres-0.3.2.2.drv
  /nix/store/jy3q1q1wqvprq6dv7yf65fqnp2i6kk8l-beam-0.3.2.0.drv
  /nix/store/n7f4pxmlilmdylqj00pp2six53rc1zjp-ghc-8.4.4-with-packages.drv
building '/nix/store/jy3q1q1wqvprq6dv7yf65fqnp2i6kk8l-beam-0.3.2.0.drv'...
setupCompilerEnvironmentPhase
Build with /nix/store/s9a8h6qqdmignsqphir5jyllr5ivf0p3-ghc-8.4.4.
unpacking sources
unpacking source archive /nix/store/zm07nggq4slhhazi7bfg3a7m8dfkzw2d-beam-0.3.2.0.tar.gz
source root is beam-0.3.2.0
setting SOURCE_DATE_EPOCH to timestamp 1453790524 of file beam-0.3.2.0/src/Database/Beam/SQL/Types.hs
patching sources
Replace Cabal file with edited version from http://hackage.haskell.org/package/beam-0.3.2.0/revision/1.cabal.
compileBuildDriverPhase
setupCompileFlags: -package-db=/tmp/nix-build-beam-0.3.2.0.drv-0/setup-package.conf.d -j8 -threaded
[1 of 1] Compiling Main             ( Setup.hs, /tmp/nix-build-beam-0.3.2.0.drv-0/Main.o )
Linking Setup ...
configuring
configureFlags: --verbose --prefix=/nix/store/vs47jqykmr30jmk14lnq5az8w6xvs9qf-beam-0.3.2.0 --libdir=$prefix/lib/$compiler --libsubdir=$abi/$libname --with-gcc=gcc --package-db=/tmp/nix-build-beam-0.3.2.0.drv-0/package.conf.d --ghc-option=-j8 --disable-split-objs --disable-library-profiling --disable-profiling --enable-shared --disable-coverage --enable-static --disable-executable-dynamic --disable-tests --disable-benchmarks --enable-library-vanilla --enable-library-for-ghci --ghc-option=-split-sections --extra-lib-dirs=/nix/store/iirmif7qgp7pgbv80z5x1sj3hbay893d-ncurses-6.1/lib --extra-lib-dirs=/nix/store/p0z7zza48ffzcb2riaq26745s02yipfb-gmp-6.1.2/lib
Using Parsec parser
Configuring beam-0.3.2.0...
CallStack (from HasCallStack):
  die', called at libraries/Cabal/Cabal/Distribution/Simple/Configure.hs:958:20 in Cabal-2.2.0.1:Distribution.Simple.Configure
  configureFinalizedPackage, called at libraries/Cabal/Cabal/Distribution/Simple/Configure.hs:462:12 in Cabal-2.2.0.1:Distribution.Simple.Configure
  configure, called at libraries/Cabal/Cabal/Distribution/Simple.hs:596:20 in Cabal-2.2.0.1:Distribution.Simple
  confHook, called at libraries/Cabal/Cabal/Distribution/Simple/UserHooks.hs:67:5 in Cabal-2.2.0.1:Distribution.Simple.UserHooks
  configureAction, called at libraries/Cabal/Cabal/Distribution/Simple.hs:178:19 in Cabal-2.2.0.1:Distribution.Simple
  defaultMainHelper, called at libraries/Cabal/Cabal/Distribution/Simple.hs:115:27 in Cabal-2.2.0.1:Distribution.Simple
  defaultMain, called at Setup.hs:2:8 in main:Main
Setup: Encountered missing dependencies:
base ==4.8.*

builder for '/nix/store/jy3q1q1wqvprq6dv7yf65fqnp2i6kk8l-beam-0.3.2.0.drv' failed with exit code 1
cannot build derivation '/nix/store/n7f4pxmlilmdylqj00pp2six53rc1zjp-ghc-8.4.4-with-packages.drv': 1 dependencies couldn't be built
error: build of '/nix/store/n7f4pxmlilmdylqj00pp2six53rc1zjp-ghc-8.4.4-with-packages.drv' failed

This is not trying to build ghc. This is trying to build beam.

ya

ghc-${version}-with-packages is not ghc - when you're inside of a nix-shell involving haskell projects, you're just dropped into an environment with ghc equipped with (with) certain packages (those specified by your nix expression). So the very last thing that gets 'built'/realised in a shell of a haskell project is ghc-${version}-with-packages.drv