[Haskell-cafe] GHC API: type class instance check

MigMit migmit at gmail.com
Fri Nov 11 09:07:16 UTC 2016

I'm no expert in GHC plugins, but isn't it true that class instances can be added in other modules? So that this information is simply not available when compiling one?

> On 11 Nov 2016, at 08:57, J. Stutterheim <j.stutterheim at me.com> wrote:
> Hi all,
> I'm writing a core-to-core GHC plugin and have two questions:
> - Given some t :: Type, how can I check whether there exists an instance of some type class C for t?
> - How can I check whether some type class C exists, and if so, how can I get a value c (presumably :: Class) of this class?
> Thanks!
> - Jurriƫn_______________________________________________
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