Bug#906431: haskell-stack: FTBFS: Duplicate instance declarations

[Damyan Ivanov]

Package: haskell-stack
Version: 1.6.5-2
Severity: serious
Tags: ftbfs
Justification: fails to build from source (but built successfully in the past)

Hi,

Building haskell-stack in a current sid chroot/amd64 fails several errors like 
this:

src/test/Stack/StoreSpec.hs:54:3: error:
    Duplicate instance declarations:
      instance Monad m => Serial m Int64
        -- Defined at src/test/Stack/StoreSpec.hs:54:3
      instance [overlap ok] Monad m => Serial m Int64
        -- Defined in `Test.SmallCheck.Series'
   |
54 | $(do let ns = [ ''Int64, ''Word64, ''Word8
   |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^...
make: *** [/usr/share/cdbs/1/class/hlibrary.mk:147: build-ghc-stamp] Error 1

reproducible-builds also show this: 
https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/haskell-stack.html

Complete build log attached.

-- dam
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