Type class instances in scope

[Tom Sydney Kerckhove]

Hi Edward,

I'm sorry to have to bother you with this again, but I seem to be stuck
with this approach.
I think I don't really understand what 'load the interfaces' means.

Here's what I tried:

``` Haskell
getInstancesFromTcmodule :: GhcMonad m => TypecheckedModule -> m ()
getInstancesFromTcmodule tmod = do
    let (tcenv, md) = tm_internals_ tmod
    let insts = tcg_insts tcenv
    printO insts
    printO $ md_insts md
    printO $ tcg_inst_env tcenv
    graph <- depanal [] True
    printO graph
    forM_ graph $ \mod_ -> do
        forM_ (ms_textual_imps mod_) $ \(_, imp) -> do
            let modname = unLoc imp
            addTarget
                (Target
                 { targetId = TargetModule modname
                 , targetAllowObjCode = True
                 , targetContents = Nothing
                 })
            loadSuccessfully $ LoadUpTo modname
            getModSummary (unLoc imp) >>= printO
        tcmod <- parseModule mod_ >>= typecheckModule >>= loadModule
        let (tcenv', md') = tm_internals_ tcmod
        printO $ tcg_insts tcenv'
        printO $ md_insts md'
        printO $ tcg_inst_env tcenv'
```

I just wanted to see if I could find all the relevant instances.

I do find all the instances in the current `TypecheckedModle`, but none
of the others because at `loadSuccessfully $ loadUpTo modname`, I get an
error saying that `Test.QuickCheck a package module`.
I think that means that it's not locally defined, but rather part of a
package that I'm using.
Unfortunately that means that I don't really understand how I can load
it to find the instances.

Would you please hint me at the next step?

Thank you for your time.


On 19-05-17 23:00:41, Tom Sydney Kerckhove wrote:
> On 19-05-17 08:35:32, Edward Z. Yang wrote:
> > Excerpts from Tom Sydney Kerckhove's message of 2017-05-19 11:05:17 +0200:
> > > > But if you
> > > > really need all instances, you will have to first arrange to load
> > > > the interfaces of ALL modules transitively imported by your module.
> > > 
> > > I don't really mind the time it takes to do this, but that's annoying to
> > > write.
> > > 
> > > Thank you for your help! I will look into it.
> > 
> > Another possibility is, if you can programatically list the types that
> > you are interested in, you can load all of those, and then the instances
> > for those types will be ready.
> 
> That's probably the most feasible approach.
> Then I'd have to find all the types in scope, and find their interfaces.
> 
> I know how to get all the TyThing's in scope, so it should be easy-ish
> to get started.
> 
> Thanks!
> 
> -- 
> Tom Sydney Kerckhove



-- 
Tom Sydney Kerckhove
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