Start with the Class.  Use classTyCon to get the TyCon.  Use tyConDataCons to 
get the data constructor.

Simon

From: ghc-devs [mailto:[email protected]] On Behalf Of Conal Elliott
Sent: 23 March 2016 00:09
To: [email protected]
Subject: lookupRdrNameInModuleForPlugins with constructors

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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