checkTauTvUpdate: take synonym families into account

[ghc-hetmet.git] / compiler / types / TyCon.lhs

diff --git a/compiler/types/TyCon.lhs b/compiler/types/TyCon.lhs
index 144a670..6dba52b 100644 (file)
--- a/compiler/types/TyCon.lhs
+++ b/compiler/types/TyCon.lhs
@@ -17,8 +17,8 @@ module TyCon(
        SynTyConRhs(..),
 
        isFunTyCon, isUnLiftedTyCon, isProductTyCon, 
-       isAlgTyCon, isDataTyCon, isSynTyCon, isNewTyCon, isClosedNewTyCon,
-       isPrimTyCon, 
+       isAlgTyCon, isDataTyCon, isNewTyCon, isClosedNewTyCon, isSynTyCon,
+       isClosedSynTyCon, isPrimTyCon, 
        isEnumerationTyCon, isGadtSyntaxTyCon, isOpenTyCon,
        assocTyConArgPoss_maybe, isTyConAssoc, setTyConArgPoss,
        isTupleTyCon, isUnboxedTupleTyCon, isBoxedTupleTyCon, tupleTyConBoxity,
@@ -600,6 +600,13 @@ isSynTyCon :: TyCon -> Bool
 isSynTyCon (SynTyCon {}) = True
 isSynTyCon _            = False
 
+-- As for newtypes, it is in some contexts important to distinguish between
+-- closed synonyms and synonym families, as synonym families have no unique
+-- right hand side to which a synonym family application can expand.
+--
+isClosedSynTyCon :: TyCon -> Bool
+isClosedSynTyCon tycon = isSynTyCon tycon && not (isOpenTyCon tycon)
+
 isGadtSyntaxTyCon :: TyCon -> Bool
 isGadtSyntaxTyCon (AlgTyCon { algTcGadtSyntax = res }) = res
 isGadtSyntaxTyCon other                                       = False