From 6cce36f83aec33d33545e0ef2135894d22dff5ca Mon Sep 17 00:00:00 2001 From: Simon Peyton Jones Date: Fri, 15 Feb 2019 09:53:48 +0000 Subject: Add AnonArgFlag to FunTy The big payload of this patch is: Add an AnonArgFlag to the FunTy constructor of Type, so that (FunTy VisArg t1 t2) means (t1 -> t2) (FunTy InvisArg t1 t2) means (t1 => t2) The big payoff is that we have a simple, local test to make when decomposing a type, leading to many fewer calls to isPredTy. To me the code seems a lot tidier, and probably more efficient (isPredTy has to take the kind of the type). See Note [Function types] in TyCoRep. There are lots of consequences * I made FunTy into a record, so that it'll be easier when we add a linearity field, something that is coming down the road. * Lots of code gets touched in a routine way, simply because it pattern matches on FunTy. * I wanted to make a pattern synonym for (FunTy2 arg res), which picks out just the argument and result type from the record. But alas the pattern-match overlap checker has a heart attack, and either reports false positives, or takes too long. In the end I gave up on pattern synonyms. There's some commented-out code in TyCoRep that shows what I wanted to do. * Much more clarity about predicate types, constraint types and (in particular) equality constraints in kinds. See TyCoRep Note [Types for coercions, predicates, and evidence] and Note [Constraints in kinds]. This made me realise that we need an AnonArgFlag on AnonTCB in a TyConBinder, something that was really plain wrong before. See TyCon Note [AnonTCB InivsArg] * When building function types we must know whether we need VisArg (mkVisFunTy) or InvisArg (mkInvisFunTy). This turned out to be pretty easy in practice. * Pretty-printing of types, esp in IfaceType, gets tidier, because we were already recording the (->) vs (=>) distinction in an ad-hoc way. Death to IfaceFunTy. * mkLamType needs to keep track of whether it is building (t1 -> t2) or (t1 => t2). See Type Note [mkLamType: dictionary arguments] Other minor stuff * Some tidy-up in validity checking involving constraints; Trac #16263 --- compiler/hieFile/HieAst.hs | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'compiler/hieFile/HieAst.hs') diff --git a/compiler/hieFile/HieAst.hs b/compiler/hieFile/HieAst.hs index 7fd217cda5..9ac65ce399 100644 --- a/compiler/hieFile/HieAst.hs +++ b/compiler/hieFile/HieAst.hs @@ -31,7 +31,7 @@ import Name ( Name, nameSrcSpan, setNameLoc ) import NameEnv ( NameEnv, emptyNameEnv, extendNameEnv, lookupNameEnv ) import SrcLoc import TcHsSyn ( hsLitType, hsPatType ) -import Type ( mkFunTys, Type ) +import Type ( mkVisFunTys, Type ) import TysWiredIn ( mkListTy, mkSumTy ) import Var ( Id, Var, setVarName, varName, varType ) import TcRnTypes @@ -488,7 +488,7 @@ instance HasType (LHsExpr GhcTc) where fallback = makeNode e' spn matchGroupType :: MatchGroupTc -> Type - matchGroupType (MatchGroupTc args res) = mkFunTys args res + matchGroupType (MatchGroupTc args res) = mkVisFunTys args res -- | Skip desugaring of these expressions for performance reasons. -- -- cgit v1.2.1