-%
+
% (c) The GRASP/AQUA Project, Glasgow University, 2000
%
\section[FunDeps]{FunDeps - functional dependencies}
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}
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])