concat-plugin sometimes generates "Failed to load interface for ... hidden module"

[ryantrinkle]

The presence of imports sometimes causes ccc to try to load hidden modules, which causes compilation to fail. For example, this module:

{-# LANGUAGE TypeApplications #-}
{-# OPTIONS_GHC -fplugin=ConCat.Plugin -fplugin-opt ConCat.Plugin:trace #-}
module LoadsHiddenModule where

import ConCat.AltCat

import qualified Data.Aeson

f :: a -> a
f = ccc @(->) (\x -> x)

will produce output like this:

[1 of 1] Compiling LoadsHiddenModule ( LoadsHiddenModule.hs, LoadsHiddenModule.o )
go ccc (->): \ (x_adEQ :: a_adF0) -> x_adEQ :: a_adF0 -> a_adF0
Doing lam Id
user error (Errors:
<interactive>:1:1: error:
    Failed to load interface for ‘Data.Attoparsec.Text.Internal’
    it is a hidden module in the package ‘attoparsec-0.13.1.0’
    Use -v to see a list of the files searched for.
Warnings:)

However, if the import qualified Data.Aeson is removed, compilation will succeed and work as expected.

[conal]

Thanks for the report. I have a fragile workaround, and I'm working on a real solution, which requires that I remove hidden modules from the set of orphan modules (transitively for the module being compiled). Much of GHC is still pretty mysterious to me.

I'd love to hear about what you're up to with compiling to categories.

[conal]

@ryantrinkle I think it's fixed now. Fragile workaround banished! Please give it a spin, and let me know.