Yesod and Persistent cause compiler panic

Hello,

This is my first bug report for GHC, so excuse me if I don't have all the formatting correct, and please tell me how to correct it!

I am working on a yesod app, and upon running cabal run, I got this message:

Preprocessing executable 'creative-index-org' for creative-index-org-0.0.0...
[1 of 1] Compiling Main             ( Main.hs, dist/build/creative-index-org/creative-index-org-tmp/Main.o )

<no location info>: error:
    ghc: panic! (the 'impossible' happened)
  (GHC version 8.0.2 for x86_64-unknown-linux):
        initTc: unsolved constraints
  WC {wc_insol = [W] person_aodw :: t_aodv[tau:1] (CHoleCan: person)}

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

I have attached Main.hs, the cabal file, and a nix-shell file (in case you use nix) that contains the environment I was running this in.

Trac metadata

Trac field	Value
Version	8.0.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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