diff options
Diffstat (limited to 'compiler/rename/RnSource.hs')
| -rw-r--r-- | compiler/rename/RnSource.hs | 31 |
1 files changed, 13 insertions, 18 deletions
diff --git a/compiler/rename/RnSource.hs b/compiler/rename/RnSource.hs index c76eb31abc..5ec4e05cd1 100644 --- a/compiler/rename/RnSource.hs +++ b/compiler/rename/RnSource.hs @@ -652,7 +652,7 @@ rnClsInstDecl (ClsInstDecl { cid_poly_ty = inst_ty, cid_binds = mbinds ; let (ktv_names, _, head_ty') = splitLHsInstDeclTy inst_ty' ; let cls = case hsTyGetAppHead_maybe head_ty' of Nothing -> mkUnboundName (mkTcOccFS (fsLit "<class>")) - Just (dL->L _ cls, _) -> cls + Just (dL->L _ cls) -> cls -- rnLHsInstType has added an error message -- if hsTyGetAppHead_maybe fails @@ -710,7 +710,7 @@ rnFamInstEqn doc mb_cls rhs_kvars , feqn_fixity = fixity , feqn_rhs = payload }}) rn_payload = do { tycon' <- lookupFamInstName (fmap fst mb_cls) tycon - ; let pat_kity_vars_with_dups = extractHsTysRdrTyVarsDups pats + ; let pat_kity_vars_with_dups = extractHsTyArgRdrKiTyVarsDup pats -- Use the "...Dups" form because it's needed -- below to report unsed binder on the LHS ; let pat_kity_vars = rmDupsInRdrTyVars pat_kity_vars_with_dups @@ -745,7 +745,7 @@ rnFamInstEqn doc mb_cls rhs_kvars -- the user meant to bring in scope here. This is an explicit -- forall, so we want fresh names, not class variables. -- Thus: always pass Nothing - do { (pats', pat_fvs) <- rnLHsTypes (FamPatCtx tycon) pats + do { (pats', pat_fvs) <- rnLHsTypeArgs (FamPatCtx tycon) pats ; (payload', rhs_fvs) <- rn_payload doc payload -- Report unused binders on the LHS @@ -780,16 +780,10 @@ rnFamInstEqn doc mb_cls rhs_kvars ; return ((bndrs', pats', payload'), rhs_fvs `plusFV` pat_fvs) } - ; let anon_wcs = concatMap collectAnonWildCards pats' - all_ibs = anon_wcs ++ all_imp_var_names - -- all_ibs: include anonymous wildcards in the implicit - -- binders In a type pattern they behave just like any - -- other type variable except for being anoymous. See - -- Note [Wildcards in family instances] - all_fvs = fvs `addOneFV` unLoc tycon' - -- type instance => use, hence addOneFV + ; let all_fvs = fvs `addOneFV` unLoc tycon' + -- type instance => use, hence addOneFV - ; return (HsIB { hsib_ext = all_ibs + ; return (HsIB { hsib_ext = all_imp_var_names -- Note [Wildcards in family instances] , hsib_body = FamEqn { feqn_ext = noExt , feqn_tycon = tycon' @@ -915,12 +909,13 @@ is the same as type family F a b :: * type instance F Int b = Int -This is implemented as follows: during renaming anonymous wild cards -'_' are given freshly generated names. These names are collected after -renaming (rnFamInstEqn) and used to make new type variables during -type checking (tc_fam_ty_pats). One should not confuse these wild -cards with the ones from partial type signatures. The latter generate -fresh meta-variables whereas the former generate fresh skolems. +This is implemented as follows: Unnamed wildcards remain unchanged after +the renamer, and then given fresh meta-variables during typechecking, and +it is handled pretty much the same way as the ones in partial type signatures. +We however don't want to emit hole constraints on wildcards in family +instances, so we turn on PartialTypeSignatures and turn off warning flag to +let typechecker know this. +See related Note [Wildcards in visible kind application] in TcHsType.hs Note [Unused type variables in family instances] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |