Simplifier ticks exhausted When trying UnfoldingDone ip_X7RI

When trying compiling the following code I get a ghc panic

import Network.Wai
import Network.Wai.Handler.Warp
import Network.HTTP.Types
  ( status200
  , status404)

import Blaze.ByteString.Builder (copyByteString)
import qualified Data.ByteString.UTF8 as BU
import Data.Monoid


main = do
    let port = 3000
    putStrLn $ "Listening on port " ++ show port
    run port app


app req respond =
    respond
      $ case pathInfo req of
        ["avOK"] -> avOK
        ["avWrong"] -> avWrong
        x -> index x


avOK =
    responseBuilder
    status200
    [("Content-Type", "text/html")]
    $ mconcat
    $ map copyByteString
    [ "<!DOCTYPE html>"
    , "<html>"
    , "<head>"
    , "<title>Title</title>"
    , "</head>"
    , "<body>"
    , "<div class=\"status\">"
    , "In stock, usually dispatched in 1 business day"
    , "</div>"
    , "</body>"
    , "</html>"]


avWrong =
    responseBuilder
    status404
    [("Content-Type", "text/html")]
    $ mconcat
    $ map copyByteString ["<p>wong!</p>"]


index x =
    responseBuilder
    status200
    [("Content-Type", "text/html")]
    $ mconcat
    $ map copyByteString
    [ "<p>Hello from "
    , BU.fromString $ show x
    , "!</p>"
    , "<p><a href='/yay'>yay</a></p>\n" ]

We get

<no location info>:
    ghc: panic! (the 'impossible' happened)
  (GHC version 7.10.2 for x86_64-unknown-linux):
        Simplifier ticks exhausted
  When trying UnfoldingDone ip_X7RI
  To increase the limit, use -fsimpl-tick-factor=N (default 100)
  If you need to do this, let GHC HQ know, and what factor you needed
  To see detailed counts use -ddump-simpl-stats
  Total ticks: 53522k

After a little bit of debugging I realised that it's the copyBytestring imported from import Blaze.ByteString.Builder function that is causing trouble, by reducing the number of elements in the list the function doesn't crash the compiler, so for instance:

avOK =
    responseBuilder
    status200
    [("Content-Type", "text/html")]
    $ mconcat
    $ map copyByteString
    [ "<!DOCTYPE html>"
    , "<html><head><title>Title</title></head>"
    , "<body>"
    , "<div class=\"status\">"
    , "In stock, usually dispatched in 1 business day"
    , "</div>"
    , "</body>"
    , "</html>"]

compiles happily. I'm using

bytestring-0.10.6.0
wai-3.0.4.0
warp-3.1.8
http-types-0.8.6
blaze-builder-0.4.0.1
utf8-string-1.0.1.1

Edited Mar 10, 2019 by Simon Peyton Jones

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