Commit aa1e0976 authored by Committed by email@example.com.Browse files
Add silent superclass parameters (again)
Silent superclass parameters solve the problem that the superclasses of a dicionary construction can easily turn out to be (wrongly) bottom. The problem and solution are described in Note [Silent superclass arguments] in TcInstDcls I first implemented this fix (with Dimitrios) in Dec 2010, but removed it again in Jun 2011 becuase we thought it wasn't necessary any more. (The reason we thought it wasn't necessary is that we'd stopped generating derived superclass constraints for *wanteds*. But we were wrong; that didn't solve the superclass-loop problem.) So we have to re-implement it. It's not hard. Main features: * The IdDetails for a DFunId says how many silent arguments it has * A DFunUnfolding describes which dictionary args are just parameters (DFunLamArg) and which are a function to apply to the parameters (DFunPolyArg). This adds the DFunArg type to CoreSyn * Consequential changes to IfaceSyn. (Binary hi file format changes slightly.) * TcInstDcls changes to generate the right dfuns * CoreSubst.exprIsConApp_maybe handles the new DFunUnfolding The thing taht is *not* done yet is to alter the vectoriser to pass the relevant extra argument when building a PA dictionary.
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