Fix check of rhs of type family instances (#2157)

[ghc-hetmet.git] / compiler / typecheck / TcTyClsDecls.lhs

diff --git a/compiler/typecheck/TcTyClsDecls.lhs b/compiler/typecheck/TcTyClsDecls.lhs
index fa10fbf..4a2a289 100644 (file)
--- a/compiler/typecheck/TcTyClsDecls.lhs
+++ b/compiler/typecheck/TcTyClsDecls.lhs
@@ -224,6 +224,10 @@ mkGlobalThings decls things
         = (name, AClass cl)
     mk_thing (L _ decl, ~(ATyCon tc))
          = (tcdName decl, ATyCon tc)
+#if __GLASGOW_HASKELL__ < 605
+-- Old GHCs don't understand that ~... matches anything
+    mk_thing _ = panic "mkGlobalThings: Can't happen"
+#endif
 \end{code}
 
 
@@ -282,8 +286,7 @@ tcFamInstDecl1 (decl@TySynonym {tcdLName = L loc tc_name})
        ; t_typats <- mapM tcHsKindedType k_typats
        ; t_rhs    <- tcHsKindedType k_rhs
 
-         -- (3) check that 
-         --     - check the well-formedness of the instance
+         -- (3) check the well-formedness of the instance
        ; checkValidTypeInst t_typats t_rhs
 
          -- (4) construct representation tycon