-%
+
% (c) The GRASP/AQUA Project, Glasgow University, 2000
%
\section[FunDeps]{FunDeps - functional dependencies}
import Name ( Name, getSrcLoc )
import Var ( TyVar )
-import Class ( Class, FunDep, classTvsFds )
-import Unify ( tcUnifyTys, BindFlag(..) )
+import Class ( Class, FunDep, pprFundeps, classTvsFds )
+import TcGadt ( tcUnifyTys, BindFlag(..) )
import Type ( substTys, notElemTvSubst )
+import Coercion ( isEqPred )
import TcType ( Type, PredType(..), tcEqType,
predTyUnique, mkClassPred, tyVarsOfTypes, tyVarsOfPred )
import InstEnv ( Instance(..), InstEnv, instanceHead, classInstances,
\begin{code}
grow :: [PredType] -> TyVarSet -> TyVarSet
+-- See Note [Ambiguity] in TcSimplify
grow preds fixed_tvs
| null preds = fixed_tvs
| otherwise = loop fixed_tvs
\begin{code}
improve inst_env preds
- = [ eqn | group <- equivClassesByUniq (predTyUnique . fst) preds,
+ = [ eqn | group <- equivClassesByUniq (predTyUnique . fst) (filterEqPreds preds),
eqn <- checkGroup inst_env group ]
+ where
+ filterEqPreds = filter (not . isEqPred . fst)
+ -- Equality predicates don't have uniques
+ -- In any case, improvement *generates*, rather than
+ -- *consumes*, equality constraints
----------
checkGroup :: (Class -> [Instance])
\end{code}
-%************************************************************************
-%* *
-\subsection{Miscellaneous}
-%* *
-%************************************************************************
-
-\begin{code}
-pprFundeps :: Outputable a => [FunDep a] -> SDoc
-pprFundeps [] = empty
-pprFundeps fds = hsep (ptext SLIT("|") : punctuate comma (map ppr_fd fds))
-
-ppr_fd (us, vs) = hsep [interppSP us, ptext SLIT("->"), interppSP vs]
-\end{code}