Module System.Random issue

[Humbert]

Hi,

I'm trying to use rndSelect in module System.Random. I did import System.Random in my code and:

choose : List (String, Maybe m) -> IO (String, Maybe m)

choose enabledTs = rndSelect enabledTs

I get this message:

Undefined name Data.List.NonEmpty at:

      choose enabledTs = rndSelect enabledTs

                                                 ^^^^^^^^^^^^^^^^^^^

Any idea on what am I doing wrong?

Thanks in advance,

Humbert.

[Denis Buzdalov]

Well, the reason for this is a known issue of the compile.

A function `rndSelect` from module `System.Random` uses a type `NonEmpty` from the module `Data.List` in its signature. Since `Data.List` is imported in `System.Random`, `NonEmpty` can be freely used inside of it. But `System.Random` does not import `Data.List` publicly, thus is does not reexport definitions from `Data.List` for those who are importing the `System.Random` module.

I.e. definitions are not reexported from imported modules even if they are used in the public interface of a module.

So, for now, to solve the problem for your module, you can just add `import Data.List` to your module. An alternative solution would be a PR replacing `import Data.List` to `import public Data.List` in `System.Random`.

[Humbert Fiorino]

Thanks a lot! 

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