Type/type class information in GHC plugin
eir at cis.upenn.edu
Sun Apr 27 05:39:24 UTC 2014
I’m not sure if I’m answering exactly what you’re asking, but perhaps this can move you in the right direction:
- To apply an expression to some types, you can use mkTyApps, in the CoreSyn module. The type of that function (Expr b -> [Type] -> Expr b) should be self-explanatory.
- To get the instance environments (where all class instances are stored), use tcGetInstEnvs, in the Inst module.
- Then, to get the actual dictionary, you can do the lookup with lookupInstEnv, in the InstEnv module.
Does this move you in the right direction?
On Apr 24, 2014, at 5:37 PM, Shen Chen Xu <shenchenxu at gmail.com> wrote:
> Hello everyone,
> I would like to write a GHC plugin which adds wrapper to functions. Say I have
> a function
> addWrapper :: Ord a => (a -> b) -> a -> b
> which is supposed to transform (assuming the argument is in the Ord class)
> foo = \ x -> ...
> foo = addWrapper (\ x -> ...)
> This works fine if I'm only interested in wrapping functions of type Int ->
> Int, in which case I make addWrapper to also have type
> addWrapper :: (Int -> Int) -> Int -> Int
> and use mkCoreApp to apply addWrapper to the right hand side.
> However, if I want it to be polymorphic as described above, the transformed GHC
> Core for an Int -> Int function should look like
> foo = addHook @ GHC.Types.Int @ GHC.Types.Int GHC.Classes.$fOrdInt (\ x -> ...)
> My question is, given the right hand side of foo, how do I construct the
> type/type class information inside Core shown above?
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