Bug#821453: haskell-lambdabot-haskell-plugins: FTBFS w/ src-exts 1.17.x

[Aaron M. Ucko]

Source: haskell-lambdabot-haskell-plugins
Version: 5.0.3-3
Severity: serious
Justification: fails to build from source

Builds of haskell-lambdabot-haskell-plugins against current unstable
have been failing with

  src/Lambdabot/Plugin/Haskell/Undo.hs:57:55:
      Couldn't match expected type `Maybe Binds' with actual type `Binds'
      In the fourth argument of `Alt', namely `(BDecls [])'
      In the expression: Alt s pat (UnGuardedRhs x) (BDecls [])

and three more such errors (on lines 72, 106, and 107).  The problem
appears to stem from an incompatible change between versions 1.16.x
and 1.17.x of libghc-src-exts-dev.

Could you please take a look?

Thanks!

-- System Information:
Debian Release: stretch/sid
  APT prefers testing
  APT policy: (500, 'testing'), (500, 'stable'), (300, 'unstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.3.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)