Type signature displayed in Hoogle is inconsistent with type signature in source

[tbagrel1]

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By mistake, I searched for Monad m => m m a -> m a (instead of Monad m => m (m a) -> m a), and still got results:

join :: Monad m => m m a -> m a xlsx-tabular Codec.Xlsx.Util.Tabular.Imports, control-monad-free Control.Monad.Free

But in both packages, join is actually reexported from Control.Monad, and has signature join :: Monad m => m (m a) -> m a

If I search for Monad m => m (m a) -> m a, then I don't see xlsx-tabular Codec.Xlsx.Util.Tabular.Imports and control-monad-free Control.Monad.Free listed, so something wrong might happen when these packages are parsed/indexed.

[googleson78]

Also reproduces for me:

[ndmitchell]

The problem is that the associated file that Haddock generates at https://hackage.haskell.org/package/xlsx-tabular-0.2.2.1/docs/xlsx-tabular.txt contains:

join :: Monad m => m m a -> m a

That's a bug in Haddock. Probably an old Haddock (the first package is 4 years old). But given bad input in, there's not much hope of Hoogle getting this right.