I'm now able to look up value identifiers, type constructors (including classes), and regular data constructors, but not dictionary constructors. Here's my failing effort to look up a dictionary constructor (in CoreM):

    hasRepThing <-
      maybe (panic "HasRep lookup failure") lookupThing =<<
        (liftIO $
          lookupRdrNameInModuleForPlugins hsc_env (mkModuleName "Circat.Rep")
             (Unqual (mkDataOcc "C:HasRep")))
    pprTrace "mkReifyEnv HasRep thing:" (ppr hasRepThing) (return ())

Result:

    ghc-stage2: panic! (the 'impossible' happened)
      (GHC version 8.1.20160307 for x86_64-apple-darwin):
            HasRep lookup failure

Same failure when I use the name string "HasRep" in place of "C:HasRep".

Any idea what I'm doing wrong here?

-- Conal

On Tue, Mar 22, 2016 at 5:40 PM, Conal Elliott <conal@conal.net> wrote:
Got it. Silly me. Thanks!!  - Conal

On Tue, Mar 22, 2016 at 5:25 PM, Andrew Farmer <xichekolas@gmail.com> wrote:
Er, dictionary... sorry, mkDataOccFS

On Tue, Mar 22, 2016 at 5:24 PM, Andrew Farmer <xichekolas@gmail.com> wrote:
> mkVarUnqual calls mkVarOccFS, which constructs an OccName in the
> varName namespace. You need to construct your RdrName via mkTyVarOcc,
> which picks the Type/Class namespace.
>
> On Tue, Mar 22, 2016 at 5:09 PM, Conal Elliott <conal@conal.net> wrote:
>> I'm trying to construct a dictionary in a GHC plugin. I'm stuck on finding
>> the constructor for the dictionary. When I use `-ddump-simpl` on the module
>> that defines the class, I see "Circat.Rep.C:HasRep". To try finding that
>> constructor, I say
>>
>>> lookupRdrNameInModuleForPlugins hsc_env
>>>   (mkModuleName "Circat.Rep") (mkVarUnqual "C:HasRep")
>>
>> However, I keep getting `Nothing` as a result. (Same without the "C:".) I've
>> also had this same difficulty when looking up constructors for algebraic
>> data types and when looking up TyCons. For regular value Ids, lookup
>> succeeds.
>>
>> What am I missing?
>>
>> Thanks, - Conal
>>
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