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Diffstat (limited to 'compiler/hsSyn/HsPat.lhs')
| -rw-r--r-- | compiler/hsSyn/HsPat.lhs | 324 |
1 files changed, 324 insertions, 0 deletions
diff --git a/compiler/hsSyn/HsPat.lhs b/compiler/hsSyn/HsPat.lhs new file mode 100644 index 0000000000..953d228942 --- /dev/null +++ b/compiler/hsSyn/HsPat.lhs @@ -0,0 +1,324 @@ +% +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 +% +\section[PatSyntax]{Abstract Haskell syntax---patterns} + +\begin{code} +module HsPat ( + Pat(..), InPat, OutPat, LPat, + + HsConDetails(..), hsConArgs, + + mkPrefixConPat, mkCharLitPat, mkNilPat, + + isBangHsBind, + patsAreAllCons, isConPat, isSigPat, isWildPat, + patsAreAllLits, isLitPat, isIrrefutableHsPat + ) where + +#include "HsVersions.h" + + +import {-# SOURCE #-} HsExpr ( SyntaxExpr ) + +-- friends: +import HsBinds ( DictBinds, HsBind(..), emptyLHsBinds, pprLHsBinds ) +import HsLit ( HsLit(HsCharPrim), HsOverLit ) +import HsTypes ( LHsType, PostTcType ) +import BasicTypes ( Boxity, tupleParens ) +-- others: +import PprCore ( {- instance OutputableBndr TyVar -} ) +import TysWiredIn ( nilDataCon, charDataCon, charTy ) +import Var ( TyVar ) +import DataCon ( DataCon, dataConTyCon ) +import TyCon ( isProductTyCon ) +import Outputable +import Type ( Type ) +import SrcLoc ( Located(..), unLoc, noLoc ) +\end{code} + + +\begin{code} +type InPat id = LPat id -- No 'Out' constructors +type OutPat id = LPat id -- No 'In' constructors + +type LPat id = Located (Pat id) + +data Pat id + = ------------ Simple patterns --------------- + WildPat PostTcType -- Wild card + | VarPat id -- Variable + | VarPatOut id (DictBinds id) -- Used only for overloaded Ids; the + -- bindings give its overloaded instances + | LazyPat (LPat id) -- Lazy pattern + | AsPat (Located id) (LPat id) -- As pattern + | ParPat (LPat id) -- Parenthesised pattern + | BangPat (LPat id) -- Bang patterng + + ------------ Lists, tuples, arrays --------------- + | ListPat [LPat id] -- Syntactic list + PostTcType -- The type of the elements + + | TuplePat [LPat id] -- Tuple + Boxity -- UnitPat is TuplePat [] + PostTcType + -- You might think that the PostTcType was redundant, but it's essential + -- data T a where + -- T1 :: Int -> T Int + -- f :: (T a, a) -> Int + -- f (T1 x, z) = z + -- When desugaring, we must generate + -- f = /\a. \v::a. case v of (t::T a, w::a) -> + -- case t of (T1 (x::Int)) -> + -- Note the (w::a), NOT (w::Int), because we have not yet + -- refined 'a' to Int. So we must know that the second component + -- of the tuple is of type 'a' not Int. See selectMatchVar + + | PArrPat [LPat id] -- Syntactic parallel array + PostTcType -- The type of the elements + + ------------ Constructor patterns --------------- + | ConPatIn (Located id) + (HsConDetails id (LPat id)) + + | ConPatOut (Located DataCon) + [TyVar] -- Existentially bound type variables + [id] -- Ditto dictionaries + (DictBinds id) -- Bindings involving those dictionaries + (HsConDetails id (LPat id)) + Type -- The type of the pattern + + ------------ Literal and n+k patterns --------------- + | LitPat HsLit -- Used for *non-overloaded* literal patterns: + -- Int#, Char#, Int, Char, String, etc. + + | NPat (HsOverLit id) -- ALWAYS positive + (Maybe (SyntaxExpr id)) -- Just (Name of 'negate') for negative + -- patterns, Nothing otherwise + (SyntaxExpr id) -- Equality checker, of type t->t->Bool + PostTcType -- Type of the pattern + + | NPlusKPat (Located id) -- n+k pattern + (HsOverLit id) -- It'll always be an HsIntegral + (SyntaxExpr id) -- (>=) function, of type t->t->Bool + (SyntaxExpr id) -- Name of '-' (see RnEnv.lookupSyntaxName) + + ------------ Generics --------------- + | TypePat (LHsType id) -- Type pattern for generic definitions + -- e.g f{| a+b |} = ... + -- These show up only in class declarations, + -- and should be a top-level pattern + + ------------ Pattern type signatures --------------- + | SigPatIn (LPat id) -- Pattern with a type signature + (LHsType id) + + | SigPatOut (LPat id) -- Pattern with a type signature + Type + + ------------ Dictionary patterns (translation only) --------------- + | DictPat -- Used when destructing Dictionaries with an explicit case + [id] -- superclass dicts + [id] -- methods +\end{code} + +HsConDetails is use both for patterns and for data type declarations + +\begin{code} +data HsConDetails id arg + = PrefixCon [arg] -- C p1 p2 p3 + | RecCon [(Located id, arg)] -- C { x = p1, y = p2 } + | InfixCon arg arg -- p1 `C` p2 + +hsConArgs :: HsConDetails id arg -> [arg] +hsConArgs (PrefixCon ps) = ps +hsConArgs (RecCon fs) = map snd fs +hsConArgs (InfixCon p1 p2) = [p1,p2] +\end{code} + + +%************************************************************************ +%* * +%* Printing patterns +%* * +%************************************************************************ + +\begin{code} +instance (OutputableBndr name) => Outputable (Pat name) where + ppr = pprPat + +pprPatBndr :: OutputableBndr name => name -> SDoc +pprPatBndr var -- Print with type info if -dppr-debug is on + = getPprStyle $ \ sty -> + if debugStyle sty then + parens (pprBndr LambdaBind var) -- Could pass the site to pprPat + -- but is it worth it? + else + ppr var + +pprPat :: (OutputableBndr name) => Pat name -> SDoc +pprPat (VarPat var) = pprPatBndr var +pprPat (VarPatOut var bs) = parens (pprPatBndr var <+> braces (ppr bs)) +pprPat (WildPat _) = char '_' +pprPat (LazyPat pat) = char '~' <> ppr pat +pprPat (BangPat pat) = char '!' <> ppr pat +pprPat (AsPat name pat) = parens (hcat [ppr name, char '@', ppr pat]) +pprPat (ParPat pat) = parens (ppr pat) +pprPat (ListPat pats _) = brackets (interpp'SP pats) +pprPat (PArrPat pats _) = pabrackets (interpp'SP pats) +pprPat (TuplePat pats bx _) = tupleParens bx (interpp'SP pats) + +pprPat (ConPatIn con details) = pprUserCon con details +pprPat (ConPatOut con tvs dicts binds details _) + = getPprStyle $ \ sty -> -- Tiresome; in TcBinds.tcRhs we print out a + if debugStyle sty then -- typechecked Pat in an error message, + -- and we want to make sure it prints nicely + ppr con <+> sep [ hsep (map pprPatBndr tvs) <+> hsep (map pprPatBndr dicts), + pprLHsBinds binds, pprConArgs details] + else pprUserCon con details + +pprPat (LitPat s) = ppr s +pprPat (NPat l Nothing _ _) = ppr l +pprPat (NPat l (Just _) _ _) = char '-' <> ppr l +pprPat (NPlusKPat n k _ _) = hcat [ppr n, char '+', ppr k] +pprPat (TypePat ty) = ptext SLIT("{|") <> ppr ty <> ptext SLIT("|}") +pprPat (SigPatIn pat ty) = ppr pat <+> dcolon <+> ppr ty +pprPat (SigPatOut pat ty) = ppr pat <+> dcolon <+> ppr ty +pprPat (DictPat ds ms) = parens (sep [ptext SLIT("{-dict-}"), + brackets (interpp'SP ds), + brackets (interpp'SP ms)]) + +pprUserCon c (InfixCon p1 p2) = ppr p1 <+> ppr c <+> ppr p2 +pprUserCon c details = ppr c <+> pprConArgs details + +pprConArgs (PrefixCon pats) = interppSP pats +pprConArgs (InfixCon p1 p2) = interppSP [p1,p2] +pprConArgs (RecCon rpats) = braces (hsep (punctuate comma (map (pp_rpat) rpats))) + where + pp_rpat (v, p) = hsep [ppr v, char '=', ppr p] + + +-- add parallel array brackets around a document +-- +pabrackets :: SDoc -> SDoc +pabrackets p = ptext SLIT("[:") <> p <> ptext SLIT(":]") +\end{code} + + +%************************************************************************ +%* * +%* Building patterns +%* * +%************************************************************************ + +\begin{code} +mkPrefixConPat :: DataCon -> [OutPat id] -> Type -> OutPat id +-- Make a vanilla Prefix constructor pattern +mkPrefixConPat dc pats ty = noLoc $ ConPatOut (noLoc dc) [] [] emptyLHsBinds (PrefixCon pats) ty + +mkNilPat :: Type -> OutPat id +mkNilPat ty = mkPrefixConPat nilDataCon [] ty + +mkCharLitPat :: Char -> OutPat id +mkCharLitPat c = mkPrefixConPat charDataCon [noLoc $ LitPat (HsCharPrim c)] charTy +\end{code} + + +%************************************************************************ +%* * +%* Predicates for checking things about pattern-lists in EquationInfo * +%* * +%************************************************************************ + +\subsection[Pat-list-predicates]{Look for interesting things in patterns} + +Unlike in the Wadler chapter, where patterns are either ``variables'' +or ``constructors,'' here we distinguish between: +\begin{description} +\item[unfailable:] +Patterns that cannot fail to match: variables, wildcards, and lazy +patterns. + +These are the irrefutable patterns; the two other categories +are refutable patterns. + +\item[constructor:] +A non-literal constructor pattern (see next category). + +\item[literal patterns:] +At least the numeric ones may be overloaded. +\end{description} + +A pattern is in {\em exactly one} of the above three categories; `as' +patterns are treated specially, of course. + +The 1.3 report defines what ``irrefutable'' and ``failure-free'' patterns are. +\begin{code} +isWildPat (WildPat _) = True +isWildPat other = False + +patsAreAllCons :: [Pat id] -> Bool +patsAreAllCons pat_list = all isConPat pat_list + +isConPat (AsPat _ pat) = isConPat (unLoc pat) +isConPat (ConPatIn _ _) = True +isConPat (ConPatOut _ _ _ _ _ _) = True +isConPat (ListPat _ _) = True +isConPat (PArrPat _ _) = True +isConPat (TuplePat _ _ _) = True +isConPat (DictPat ds ms) = (length ds + length ms) > 1 +isConPat other = False + +isSigPat (SigPatIn _ _) = True +isSigPat (SigPatOut _ _) = True +isSigPat other = False + +patsAreAllLits :: [Pat id] -> Bool +patsAreAllLits pat_list = all isLitPat pat_list + +isLitPat (AsPat _ pat) = isLitPat (unLoc pat) +isLitPat (LitPat _) = True +isLitPat (NPat _ _ _ _) = True +isLitPat (NPlusKPat _ _ _ _) = True +isLitPat other = False + +isBangHsBind :: HsBind id -> Bool +-- In this module because HsPat is above HsBinds in the import graph +isBangHsBind (PatBind { pat_lhs = L _ (BangPat p) }) = True +isBangHsBind bind = False + +isIrrefutableHsPat :: LPat id -> Bool +-- This function returns False if it's in doubt; specifically +-- on a ConPatIn it doesn't know the size of the constructor family +-- But if it returns True, the pattern is definitely irrefutable +isIrrefutableHsPat pat + = go pat + where + go (L _ pat) = go1 pat + + go1 (WildPat _) = True + go1 (VarPat _) = True + go1 (VarPatOut _ _) = True + go1 (LazyPat pat) = True + go1 (BangPat pat) = go pat + go1 (ParPat pat) = go pat + go1 (AsPat _ pat) = go pat + go1 (SigPatIn pat _) = go pat + go1 (SigPatOut pat _) = go pat + go1 (TuplePat pats _ _) = all go pats + go1 (ListPat pats _) = False + go1 (PArrPat pats _) = False -- ? + + go1 (ConPatIn _ _) = False -- Conservative + go1 (ConPatOut (L _ con) _ _ _ details _) + = isProductTyCon (dataConTyCon con) + && all go (hsConArgs details) + + go1 (LitPat _) = False + go1 (NPat _ _ _ _) = False + go1 (NPlusKPat _ _ _ _) = False + + go1 (TypePat _) = panic "isIrrefutableHsPat: type pattern" + go1 (DictPat _ _) = panic "isIrrefutableHsPat: type pattern" +\end{code} + |