From 8bdd26e3d2864151c4d0dccbc530c2deac362892 Mon Sep 17 00:00:00 2001 From: Richard Eisenberg Date: Fri, 21 Dec 2012 20:56:25 -0500 Subject: Implement overlapping type family instances. An ordered, overlapping type family instance is introduced by 'type instance where', followed by equations. See the new section in the user manual (7.7.2.2) for details. The canonical example is Boolean equality at the type level: type family Equals (a :: k) (b :: k) :: Bool type instance where Equals a a = True Equals a b = False A branched family instance, such as this one, checks its equations in order and applies only the first the matches. As explained in the note [Instance checking within groups] in FamInstEnv.lhs, we must be careful not to simplify, say, (Equals Int b) to False, because b might later unify with Int. This commit includes all of the commits on the overlapping-tyfams branch. SPJ requested that I combine all my commits over the past several months into one monolithic commit. The following GHC repos are affected: ghc, testsuite, utils/haddock, libraries/template-haskell, and libraries/dph. Here are some details for the interested: - The definition of CoAxiom has been moved from TyCon.lhs to a new file CoAxiom.lhs. I made this decision because of the number of definitions necessary to support BranchList. - BranchList is a GADT whose type tracks whether it is a singleton list or not-necessarily-a-singleton-list. The reason I introduced this type is to increase static checking of places where GHC code assumes that a FamInst or CoAxiom is indeed a singleton. This assumption takes place roughly 10 times throughout the code. I was worried that a future change to GHC would invalidate the assumption, and GHC might subtly fail to do the right thing. By explicitly labeling CoAxioms and FamInsts as being Unbranched (singleton) or Branched (not-necessarily-singleton), we make this assumption explicit and checkable. Furthermore, to enforce the accuracy of this label, the list of branches of a CoAxiom or FamInst is stored using a BranchList, whose constructors constrain its type index appropriately. I think that the decision to use BranchList is probably the most controversial decision I made from a code design point of view. Although I provide conversions to/from ordinary lists, it is more efficient to use the brList... functions provided in CoAxiom than always to convert. The use of these functions does not wander far from the core CoAxiom/FamInst logic. BranchLists are motivated and explained in the note [Branched axioms] in CoAxiom.lhs. - The CoAxiom type has changed significantly. You can see the new type in CoAxiom.lhs. It uses a CoAxBranch type to track branches of the CoAxiom. Correspondingly various functions producing and consuming CoAxioms had to change, including the binary layout of interface files. - To get branched axioms to work correctly, it is important to have a notion of type "apartness": two types are apart if they cannot unify, and no substitution of variables can ever get them to unify, even after type family simplification. (This is different than the normal failure to unify because of the type family bit.) This notion in encoded in tcApartTys, in Unify.lhs. Because apartness is finer-grained than unification, the tcUnifyTys now calls tcApartTys. - CoreLinting axioms has been updated, both to reflect the new form of CoAxiom and to enforce the apartness rules of branch application. The formalization of the new rules is in docs/core-spec/core-spec.pdf. - The FamInst type (in types/FamInstEnv.lhs) has changed significantly, paralleling the changes to CoAxiom. Of course, this forced minor changes in many files. - There are several new Notes in FamInstEnv.lhs, including one discussing confluent overlap and why we're not doing it. - lookupFamInstEnv, lookupFamInstEnvConflicts, and lookup_fam_inst_env' (the function that actually does the work) have all been more-or-less completely rewritten. There is a Note [lookup_fam_inst_env' implementation] describing the implementation. One of the changes that affects other files is to change the type of matches from a pair of (FamInst, [Type]) to a new datatype (which now includes the index of the matching branch). This seemed a better design. - The TySynInstD constructor in Template Haskell was updated to use the new datatype TySynEqn. I also bumped the TH version number, requiring changes to DPH cabal files. (That's why the DPH repo has an overlapping-tyfams branch.) - As SPJ requested, I refactored some of the code in HsDecls: * splitting up TyDecl into SynDecl and DataDecl, correspondingly changing HsTyDefn to HsDataDefn (with only one constructor) * splitting FamInstD into TyFamInstD and DataFamInstD and splitting FamInstDecl into DataFamInstDecl and TyFamInstDecl * making the ClsInstD take a ClsInstDecl, for parallelism with InstDecl's other constructors * changing constructor TyFamily into FamDecl * creating a FamilyDecl type that stores the details for a family declaration; this is useful because FamilyDecls can appear in classes but other decls cannot * restricting the associated types and associated type defaults for a * class to be the new, more restrictive types * splitting cid_fam_insts into cid_tyfam_insts and cid_datafam_insts, according to the new types * perhaps one or two more that I'm overlooking None of these changes has far-reaching implications. - The user manual, section 7.7.2.2, is updated to describe the new type family instances. --- src/Haddock/Backends/Xhtml/Decl.hs | 62 ++++++++++++++++++++------------------ 1 file changed, 32 insertions(+), 30 deletions(-) (limited to 'src/Haddock/Backends/Xhtml') diff --git a/src/Haddock/Backends/Xhtml/Decl.hs b/src/Haddock/Backends/Xhtml/Decl.hs index 59be34f7..db39ccca 100644 --- a/src/Haddock/Backends/Xhtml/Decl.hs +++ b/src/Haddock/Backends/Xhtml/Decl.hs @@ -39,10 +39,9 @@ ppDecl :: Bool -> LinksInfo -> LHsDecl DocName -> DocForDecl DocName -> [DocInstance DocName] -> [(DocName, DocForDecl DocName)] -> Bool -> Qualification -> Html ppDecl summ links (L loc decl) (mbDoc, fnArgsDoc) instances subdocs unicode qual = case decl of - TyClD d@(TyFamily {}) -> ppTyFam summ False links loc mbDoc d unicode qual - TyClD d@(TyDecl{ tcdTyDefn = defn }) - | isHsDataDefn defn -> ppDataDecl summ links instances subdocs loc mbDoc d unicode qual - | otherwise -> ppTySyn summ links loc (mbDoc, fnArgsDoc) d unicode qual + TyClD (FamDecl d) -> ppTyFam summ False links loc mbDoc d unicode qual + TyClD d@(DataDecl {}) -> ppDataDecl summ links instances subdocs loc mbDoc d unicode qual + TyClD d@(SynDecl {}) -> ppTySyn summ links loc (mbDoc, fnArgsDoc) d unicode qual TyClD d@(ClassDecl {}) -> ppClassDecl summ links instances loc mbDoc subdocs d unicode qual SigD (TypeSig lnames (L _ t)) -> ppFunSig summ links loc (mbDoc, fnArgsDoc) (map unLoc lnames) t unicode qual ForD d -> ppFor summ links loc (mbDoc, fnArgsDoc) d unicode qual @@ -115,8 +114,8 @@ ppFor _ _ _ _ _ _ _ = error "ppFor" -- we skip type patterns for now ppTySyn :: Bool -> LinksInfo -> SrcSpan -> DocForDecl DocName -> TyClDecl DocName -> Bool -> Qualification -> Html -ppTySyn summary links loc doc (TyDecl { tcdLName = L _ name, tcdTyVars = ltyvars - , tcdTyDefn = TySynonym { td_synRhs = ltype } }) +ppTySyn summary links loc doc (SynDecl { tcdLName = L _ name, tcdTyVars = ltyvars + , tcdRhs = ltype }) unicode qual = ppTypeOrFunSig summary links loc [name] (unLoc ltype) doc (full, hdr, spaceHtml +++ equals) unicode qual @@ -145,10 +144,10 @@ ppTyName name -------------------------------------------------------------------------------- -ppTyFamHeader :: Bool -> Bool -> TyClDecl DocName -> Bool -> Qualification -> Html -ppTyFamHeader summary associated decl unicode qual = - - (case tcdFlavour decl of +ppTyFamHeader :: Bool -> Bool -> FamilyDecl DocName -> Bool -> Qualification -> Html +ppTyFamHeader summary associated d@(FamilyDecl { fdFlavour = flav + , fdKindSig = mkind }) unicode qual = + (case flav of TypeFamily | associated -> keyword "type" | otherwise -> keyword "type family" @@ -157,22 +156,22 @@ ppTyFamHeader summary associated decl unicode qual = | otherwise -> keyword "data family" ) <+> - ppTyClBinderWithVars summary decl <+> + ppFamDeclBinderWithVars summary d <+> - case tcdKindSig decl of + case mkind of Just kind -> dcolon unicode <+> ppLKind unicode qual kind Nothing -> noHtml ppTyFam :: Bool -> Bool -> LinksInfo -> SrcSpan -> Documentation DocName -> - TyClDecl DocName -> Bool -> Qualification -> Html + FamilyDecl DocName -> Bool -> Qualification -> Html ppTyFam summary associated links loc doc decl unicode qual | summary = ppTyFamHeader True associated decl unicode qual | otherwise = header_ +++ docSection qual doc +++ instancesBit where - docname = tcdName decl + docname = unLoc $ fdLName decl header_ = topDeclElem links loc [docname] (ppTyFamHeader summary associated decl unicode qual) @@ -187,23 +186,25 @@ ppTyFam summary associated links loc doc decl unicode qual -------------------------------------------------------------------------------- -ppAssocType :: Bool -> LinksInfo -> DocForDecl DocName -> LTyClDecl DocName -> Bool +ppAssocType :: Bool -> LinksInfo -> DocForDecl DocName -> LFamilyDecl DocName -> Bool -> Qualification -> Html ppAssocType summ links doc (L loc decl) unicode qual = - case decl of - TyFamily {} -> ppTyFam summ True links loc (fst doc) decl unicode qual - _ -> error "declaration type not supported by ppAssocType" + ppTyFam summ True links loc (fst doc) decl unicode qual -------------------------------------------------------------------------------- -- * TyClDecl helpers -------------------------------------------------------------------------------- +-- | Print a type family and its variables +ppFamDeclBinderWithVars :: Bool -> FamilyDecl DocName -> Html +ppFamDeclBinderWithVars summ (FamilyDecl { fdLName = lname, fdTyVars = tvs }) = + ppAppDocNameNames summ (unLoc lname) (tyvarNames tvs) --- | Print a type family / newtype / data / class binder and its variables -ppTyClBinderWithVars :: Bool -> TyClDecl DocName -> Html -ppTyClBinderWithVars summ decl = - ppAppDocNameNames summ (unLoc $ tcdLName decl) (tyvarNames $ tcdTyVars decl) +-- | Print a newtype / data binder and its variables +ppDataBinderWithVars :: Bool -> TyClDecl DocName -> Html +ppDataBinderWithVars summ decl = + ppAppDocNameNames summ (tcdName decl) (tyvarNames $ tcdTyVars decl) -------------------------------------------------------------------------------- @@ -303,7 +304,7 @@ ppShortClassDecl summary links (ClassDecl { tcdCtxt = lctxt, tcdLName = lname, t +++ shortSubDecls ( [ ppAssocType summary links doc at unicode qual | at <- ats - , let doc = lookupAnySubdoc (tcdName $ unL at) subdocs ] ++ + , let doc = lookupAnySubdoc (unL $ fdLName $ unL at) subdocs ] ++ -- ToDo: add associated type defaults @@ -336,14 +337,14 @@ ppClassDecl summary links instances loc d subdocs | null lsigs = topDeclElem links loc [nm] (hdr unicode qual) | otherwise = topDeclElem links loc [nm] (hdr unicode qual <+> keyword "where") - nm = unLoc $ tcdLName decl + nm = tcdName decl hdr = ppClassHdr summary lctxt (unLoc lname) ltyvars lfds -- ToDo: add assocatied typ defaults atBit = subAssociatedTypes [ ppAssocType summary links doc at unicode qual | at <- ats - , let doc = lookupAnySubdoc (tcdName $ unL at) subdocs ] + , let doc = lookupAnySubdoc (unL $ fdLName $ unL at) subdocs ] methodBit = subMethods [ ppFunSig summary links loc doc names typ unicode qual | L _ (TypeSig lnames (L _ typ)) <- lsigs @@ -401,7 +402,7 @@ ppShortDataDecl summary _links _loc dataDecl unicode qual doConstr c con = toHtml [c] <+> ppShortConstr summary (unLoc con) unicode qual doGADTConstr con = ppShortConstr summary (unLoc con) unicode qual - cons = td_cons (tcdTyDefn dataDecl) + cons = dd_cons (tcdDataDefn dataDecl) resTy = (con_res . unLoc . head) cons @@ -415,8 +416,8 @@ ppDataDecl summary links instances subdocs loc doc dataDecl unicode qual | otherwise = header_ +++ docSection qual doc +++ constrBit +++ instancesBit where - docname = unLoc . tcdLName $ dataDecl - cons = td_cons (tcdTyDefn dataDecl) + docname = tcdName dataDecl + cons = dd_cons (tcdDataDefn dataDecl) resTy = (con_res . unLoc . head) cons header_ = topDeclElem links loc [docname] (ppDataHeader summary dataDecl unicode qual @@ -570,14 +571,15 @@ ppShortField summary unicode qual (ConDeclField (L _ name) ltype _) -- | Print the LHS of a data\/newtype declaration. -- Currently doesn't handle 'data instance' decls or kind signatures ppDataHeader :: Bool -> TyClDecl DocName -> Bool -> Qualification -> Html -ppDataHeader summary decl@(TyDecl { tcdTyDefn = TyData { td_ND = nd, td_ctxt = ctxt } }) +ppDataHeader summary decl@(DataDecl { tcdDataDefn = HsDataDefn { dd_ND = nd + , dd_ctxt = ctxt } }) unicode qual = -- newtype or data (case nd of { NewType -> keyword "newtype"; DataType -> keyword "data" }) <+> -- context ppLContext ctxt unicode qual <+> -- T a b c ..., or a :+: b - ppTyClBinderWithVars summary decl + ppDataBinderWithVars summary decl ppDataHeader _ _ _ _ = error "ppDataHeader: illegal argument" -- cgit v1.2.3