It doesn't seem to like signatures on pattern synonyms: about argon HOT 5 CLOSED

Thanks for the report! I'll look into it.

from argon.

I think that CPP is somehow messing up the code. The following raises the error:

{-# LANGUAGE CPP #-}
#ifndef HLINT
{-# LANGUAGE ViewPatterns #-}
#endif
{-# LANGUAGE PatternSynonyms #-}

data Counted a = Counted Int [a]
               deriving (Functor, Traversable, Eq, Ord, Read, Show)

pattern (:+) :: () => () => a -> Counted a -> Counted a
pattern a :+ as <- Counted (subtract 1 -> i) (a : (Counted i -> as)) where
  a :+ Counted i as = Counted (i+1) (a:as)

while this one does not

{-# LANGUAGE ViewPatterns #-}
{-# LANGUAGE PatternSynonyms #-}

data Counted a = Counted Int [a]
               deriving (Functor, Traversable, Eq, Ord, Read, Show)

pattern (:+) :: () => () => a -> Counted a -> Counted a
pattern a :+ as <- Counted (subtract 1 -> i) (a : (Counted i -> as)) where
  a :+ Counted i as = Counted (i+1) (a:as)

I also noticed that CPP-related errors sometimes show up when the syntax is correct.

from argon.

Now all files from the lens and concurrent packages are parsed correctly.
The only exception to this rule are C macros of the form __MIN_VERSION_{package}__ which are provided by Cabal and I have yet to figure out how to support them.

from argon.

One option for MIN_VERSION_foo would be to fake them by rummaging through
the package database (or just the output of ghc-pkg list) and taking the
latest version of each as a conservative over-approximation.

That doesn't really help scenarios like stack that avoid using the global
package DB though, there you'd need to find the current sandbox.

On Thu, Oct 29, 2015 at 6:08 AM, Michele Lacchia [email protected]
wrote:

Now all files from the lens and concurrent packages are parsed correctly.
The only exception to this rule are C macros of the form
MIN_VERSION_{package} which are provided by Cabal and I have yet to
figure out how to support them.

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#14 (comment).

from argon.

I was hoping that the cabal library had some functions to work with this. I have yet to investigate the issue though.

from argon.