Add variation on makeFree without type signatures?

[Gabriella439]

The reason I'm interested in a version of makeFree without type signatures is:

• So that I can provide type signatures specialized to a particular monad
• So that I can document auto-generated commands

As far as I can tell, the only way to document commands in haddocks is to put a comment above the type signature, but if I add my own type signature it conflicts with the auto-generated type signature.

[fizruk]

This makes perfect sense to me, I'd be happy to update TH module. Do you have a name for the command in mind? Or would it be better to pass options to makeFree?

[Gabriella439]

It's probably best not to change makeFree for backwards compatibility.

The issue with template haskell functions that take options is that in order to use them you have to apply them to their arguments in a separate module because of the stage restriction, so I wouldn't go down that route unless absolutely necessary. I'd be happy with just makeFree_ or makeFreeNoTypes.

[fizruk]

I think there might be one more nice command. We can introduce makeFreeCon for single constructors and prepend Haddock documentation to makeFreeCon invocation like this:

data LangF x
  = Input (String -> x)
  | Output String x
  | Halt
  deriving (Functor)

-- | Get string.
makeFreeCon 'Input

-- | Put string.
makeFreeCon 'Output

-- | Abort computation.
makeFreeCon 'Halt

This way one does not need to write down type signatures (which I find long and boring).

makeFree_ (and, perhaps, makeFreeCon_) would still make sense when one would like to comment individual arguments like this:

makeFreeCon_ 'Output

-- | Output.
output :: MonadFree LangF m =>
          String    -- ^ String to output.
          -> m ()   -- ^ No result.

[Gabriella439]

Yeah, I like that, too

[ekmett]

Merged