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Diffstat (limited to 'compiler/hsSyn/HsExpr.lhs')
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diff --git a/compiler/hsSyn/HsExpr.lhs b/compiler/hsSyn/HsExpr.lhs new file mode 100644 index 0000000000..dbdd24c3c5 --- /dev/null +++ b/compiler/hsSyn/HsExpr.lhs @@ -0,0 +1,975 @@ +% +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 +% +\section[HsExpr]{Abstract Haskell syntax: expressions} + +\begin{code} +module HsExpr where + +#include "HsVersions.h" + +-- friends: +import HsDecls ( HsGroup ) +import HsPat ( LPat ) +import HsLit ( HsLit(..), HsOverLit ) +import HsTypes ( LHsType, PostTcType ) +import HsImpExp ( isOperator, pprHsVar ) +import HsBinds ( HsLocalBinds, DictBinds, ExprCoFn, isEmptyLocalBinds ) + +-- others: +import Type ( Type, pprParendType ) +import Var ( TyVar, Id ) +import Name ( Name ) +import BasicTypes ( IPName, Boxity, tupleParens, Arity, Fixity(..) ) +import SrcLoc ( Located(..), unLoc ) +import Outputable +import FastString +\end{code} + + +%************************************************************************ +%* * +\subsection{Expressions proper} +%* * +%************************************************************************ + +\begin{code} +type LHsExpr id = Located (HsExpr id) + +------------------------- +-- PostTcExpr is an evidence expression attached to the +-- syntax tree by the type checker (c.f. postTcType) +-- We use a PostTcTable where there are a bunch of pieces of +-- evidence, more than is convenient to keep individually +type PostTcExpr = HsExpr Id +type PostTcTable = [(Name, Id)] + +noPostTcExpr :: PostTcExpr +noPostTcExpr = HsLit (HsString FSLIT("noPostTcExpr")) + +noPostTcTable :: PostTcTable +noPostTcTable = [] + +------------------------- +-- SyntaxExpr is like PostTcExpr, but it's filled in a little earlier, +-- by the renamer. It's used for rebindable syntax. +-- E.g. (>>=) is filled in before the renamer by the appropriate Name +-- for (>>=), and then instantiated by the type checker with its +-- type args tec + +type SyntaxExpr id = HsExpr id + +noSyntaxExpr :: SyntaxExpr id -- Before renaming, and sometimes after, + -- (if the syntax slot makes no sense) +noSyntaxExpr = HsLit (HsString FSLIT("noSyntaxExpr")) + + +type SyntaxTable id = [(Name, SyntaxExpr id)] +-- *** Currently used only for CmdTop (sigh) *** +-- * Before the renamer, this list is noSyntaxTable +-- +-- * After the renamer, it takes the form [(std_name, HsVar actual_name)] +-- For example, for the 'return' op of a monad +-- normal case: (GHC.Base.return, HsVar GHC.Base.return) +-- with rebindable syntax: (GHC.Base.return, return_22) +-- where return_22 is whatever "return" is in scope +-- +-- * After the type checker, it takes the form [(std_name, <expression>)] +-- where <expression> is the evidence for the method + +noSyntaxTable :: SyntaxTable id +noSyntaxTable = [] + + +------------------------- +data HsExpr id + = HsVar id -- variable + | HsIPVar (IPName id) -- implicit parameter + | HsOverLit (HsOverLit id) -- Overloaded literals + | HsLit HsLit -- Simple (non-overloaded) literals + + | HsLam (MatchGroup id) -- Currently always a single match + + | HsApp (LHsExpr id) -- Application + (LHsExpr id) + + -- Operator applications: + -- NB Bracketed ops such as (+) come out as Vars. + + -- NB We need an expr for the operator in an OpApp/Section since + -- the typechecker may need to apply the operator to a few types. + + | OpApp (LHsExpr id) -- left operand + (LHsExpr id) -- operator + Fixity -- Renamer adds fixity; bottom until then + (LHsExpr id) -- right operand + + | NegApp (LHsExpr id) -- negated expr + (SyntaxExpr id) -- Name of 'negate' + + | HsPar (LHsExpr id) -- parenthesised expr + + | SectionL (LHsExpr id) -- operand + (LHsExpr id) -- operator + | SectionR (LHsExpr id) -- operator + (LHsExpr id) -- operand + + | HsCase (LHsExpr id) + (MatchGroup id) + + | HsIf (LHsExpr id) -- predicate + (LHsExpr id) -- then part + (LHsExpr id) -- else part + + | HsLet (HsLocalBinds id) -- let(rec) + (LHsExpr id) + + | HsDo (HsStmtContext Name) -- The parameterisation is unimportant + -- because in this context we never use + -- the PatGuard or ParStmt variant + [LStmt id] -- "do":one or more stmts + (LHsExpr id) -- The body; the last expression in the 'do' + -- of [ body | ... ] in a list comp + PostTcType -- Type of the whole expression + + | ExplicitList -- syntactic list + PostTcType -- Gives type of components of list + [LHsExpr id] + + | ExplicitPArr -- syntactic parallel array: [:e1, ..., en:] + PostTcType -- type of elements of the parallel array + [LHsExpr id] + + | ExplicitTuple -- tuple + [LHsExpr id] + -- NB: Unit is ExplicitTuple [] + -- for tuples, we can get the types + -- direct from the components + Boxity + + + -- Record construction + | RecordCon (Located id) -- The constructor. After type checking + -- it's the dataConWrapId of the constructor + PostTcExpr -- Data con Id applied to type args + (HsRecordBinds id) + + -- Record update + | RecordUpd (LHsExpr id) + (HsRecordBinds id) + PostTcType -- Type of *input* record + PostTcType -- Type of *result* record (may differ from + -- type of input record) + + | ExprWithTySig -- e :: type + (LHsExpr id) + (LHsType id) + + | ExprWithTySigOut -- TRANSLATION + (LHsExpr id) + (LHsType Name) -- Retain the signature for round-tripping purposes + + | ArithSeq -- arithmetic sequence + PostTcExpr + (ArithSeqInfo id) + + | PArrSeq -- arith. sequence for parallel array + PostTcExpr -- [:e1..e2:] or [:e1, e2..e3:] + (ArithSeqInfo id) + + | HsSCC FastString -- "set cost centre" (_scc_) annotation + (LHsExpr id) -- expr whose cost is to be measured + + | HsCoreAnn FastString -- hdaume: core annotation + (LHsExpr id) + + ----------------------------------------------------------- + -- MetaHaskell Extensions + | HsBracket (HsBracket id) + + | HsBracketOut (HsBracket Name) -- Output of the type checker is the *original* + [PendingSplice] -- renamed expression, plus *typechecked* splices + -- to be pasted back in by the desugarer + + | HsSpliceE (HsSplice id) + + ----------------------------------------------------------- + -- Arrow notation extension + + | HsProc (LPat id) -- arrow abstraction, proc + (LHsCmdTop id) -- body of the abstraction + -- always has an empty stack + + --------------------------------------- + -- The following are commands, not expressions proper + + | HsArrApp -- Arrow tail, or arrow application (f -< arg) + (LHsExpr id) -- arrow expression, f + (LHsExpr id) -- input expression, arg + PostTcType -- type of the arrow expressions f, + -- of the form a t t', where arg :: t + HsArrAppType -- higher-order (-<<) or first-order (-<) + Bool -- True => right-to-left (f -< arg) + -- False => left-to-right (arg >- f) + + | HsArrForm -- Command formation, (| e cmd1 .. cmdn |) + (LHsExpr id) -- the operator + -- after type-checking, a type abstraction to be + -- applied to the type of the local environment tuple + (Maybe Fixity) -- fixity (filled in by the renamer), for forms that + -- were converted from OpApp's by the renamer + [LHsCmdTop id] -- argument commands +\end{code} + + +These constructors only appear temporarily in the parser. +The renamer translates them into the Right Thing. + +\begin{code} + | EWildPat -- wildcard + + | EAsPat (Located id) -- as pattern + (LHsExpr id) + + | ELazyPat (LHsExpr id) -- ~ pattern + + | HsType (LHsType id) -- Explicit type argument; e.g f {| Int |} x y +\end{code} + +Everything from here on appears only in typechecker output. + +\begin{code} + | TyLam -- TRANSLATION + [TyVar] + (LHsExpr id) + | TyApp -- TRANSLATION + (LHsExpr id) -- generated by Spec + [Type] + + -- DictLam and DictApp are "inverses" + | DictLam + [id] + (LHsExpr id) + | DictApp + (LHsExpr id) + [id] + + | HsCoerce ExprCoFn -- TRANSLATION + (HsExpr id) + +type PendingSplice = (Name, LHsExpr Id) -- Typechecked splices, waiting to be + -- pasted back in by the desugarer +\end{code} + +A @Dictionary@, unless of length 0 or 1, becomes a tuple. A +@ClassDictLam dictvars methods expr@ is, therefore: +\begin{verbatim} +\ x -> case x of ( dictvars-and-methods-tuple ) -> expr +\end{verbatim} + +\begin{code} +instance OutputableBndr id => Outputable (HsExpr id) where + ppr expr = pprExpr expr +\end{code} + +\begin{code} +pprExpr :: OutputableBndr id => HsExpr id -> SDoc + +pprExpr e = pprDeeper (ppr_expr e) + +pprBinds :: OutputableBndr id => HsLocalBinds id -> SDoc +pprBinds b = pprDeeper (ppr b) + +ppr_lexpr :: OutputableBndr id => LHsExpr id -> SDoc +ppr_lexpr e = ppr_expr (unLoc e) + +ppr_expr (HsVar v) = pprHsVar v +ppr_expr (HsIPVar v) = ppr v +ppr_expr (HsLit lit) = ppr lit +ppr_expr (HsOverLit lit) = ppr lit + +ppr_expr (HsApp e1 e2) + = let (fun, args) = collect_args e1 [e2] in + (ppr_lexpr fun) <+> (sep (map pprParendExpr args)) + where + collect_args (L _ (HsApp fun arg)) args = collect_args fun (arg:args) + collect_args fun args = (fun, args) + +ppr_expr (OpApp e1 op fixity e2) + = case unLoc op of + HsVar v -> pp_infixly v + _ -> pp_prefixly + where + pp_e1 = pprParendExpr e1 -- Add parens to make precedence clear + pp_e2 = pprParendExpr e2 + + pp_prefixly + = hang (ppr op) 4 (sep [pp_e1, pp_e2]) + + pp_infixly v + = sep [pp_e1, hsep [pprInfix v, pp_e2]] + +ppr_expr (NegApp e _) = char '-' <+> pprParendExpr e + +ppr_expr (HsPar e) = parens (ppr_lexpr e) + +ppr_expr (SectionL expr op) + = case unLoc op of + HsVar v -> pp_infixly v + _ -> pp_prefixly + where + pp_expr = pprParendExpr expr + + pp_prefixly = hang (hsep [text " \\ x_ ->", ppr op]) + 4 (hsep [pp_expr, ptext SLIT("x_ )")]) + pp_infixly v = parens (sep [pp_expr, pprInfix v]) + +ppr_expr (SectionR op expr) + = case unLoc op of + HsVar v -> pp_infixly v + _ -> pp_prefixly + where + pp_expr = pprParendExpr expr + + pp_prefixly = hang (hsep [text "( \\ x_ ->", ppr op, ptext SLIT("x_")]) + 4 ((<>) pp_expr rparen) + pp_infixly v + = parens (sep [pprInfix v, pp_expr]) + +ppr_expr (HsLam matches) + = pprMatches LambdaExpr matches + +ppr_expr (HsCase expr matches) + = sep [ sep [ptext SLIT("case"), nest 4 (ppr expr), ptext SLIT("of")], + nest 2 (pprMatches CaseAlt matches) ] + +ppr_expr (HsIf e1 e2 e3) + = sep [hsep [ptext SLIT("if"), nest 2 (ppr e1), ptext SLIT("then")], + nest 4 (ppr e2), + ptext SLIT("else"), + nest 4 (ppr e3)] + +-- special case: let ... in let ... +ppr_expr (HsLet binds expr@(L _ (HsLet _ _))) + = sep [hang (ptext SLIT("let")) 2 (hsep [pprBinds binds, ptext SLIT("in")]), + ppr_lexpr expr] + +ppr_expr (HsLet binds expr) + = sep [hang (ptext SLIT("let")) 2 (pprBinds binds), + hang (ptext SLIT("in")) 2 (ppr expr)] + +ppr_expr (HsDo do_or_list_comp stmts body _) = pprDo do_or_list_comp stmts body + +ppr_expr (ExplicitList _ exprs) + = brackets (fsep (punctuate comma (map ppr_lexpr exprs))) + +ppr_expr (ExplicitPArr _ exprs) + = pa_brackets (fsep (punctuate comma (map ppr_lexpr exprs))) + +ppr_expr (ExplicitTuple exprs boxity) + = tupleParens boxity (sep (punctuate comma (map ppr_lexpr exprs))) + +ppr_expr (RecordCon con_id con_expr rbinds) + = pp_rbinds (ppr con_id) rbinds + +ppr_expr (RecordUpd aexp rbinds _ _) + = pp_rbinds (pprParendExpr aexp) rbinds + +ppr_expr (ExprWithTySig expr sig) + = hang (nest 2 (ppr_lexpr expr) <+> dcolon) + 4 (ppr sig) +ppr_expr (ExprWithTySigOut expr sig) + = hang (nest 2 (ppr_lexpr expr) <+> dcolon) + 4 (ppr sig) + +ppr_expr (ArithSeq expr info) = brackets (ppr info) +ppr_expr (PArrSeq expr info) = pa_brackets (ppr info) + +ppr_expr EWildPat = char '_' +ppr_expr (ELazyPat e) = char '~' <> pprParendExpr e +ppr_expr (EAsPat v e) = ppr v <> char '@' <> pprParendExpr e + +ppr_expr (HsSCC lbl expr) + = sep [ ptext SLIT("_scc_") <+> doubleQuotes (ftext lbl), pprParendExpr expr ] + +ppr_expr (TyLam tyvars expr) + = hang (hsep [ptext SLIT("/\\"), + hsep (map (pprBndr LambdaBind) tyvars), + ptext SLIT("->")]) + 4 (ppr_lexpr expr) + +ppr_expr (TyApp expr [ty]) + = hang (ppr_lexpr expr) 4 (pprParendType ty) + +ppr_expr (TyApp expr tys) + = hang (ppr_lexpr expr) + 4 (brackets (interpp'SP tys)) + +ppr_expr (DictLam dictvars expr) + = hang (hsep [ptext SLIT("\\{-dict-}"), + hsep (map (pprBndr LambdaBind) dictvars), + ptext SLIT("->")]) + 4 (ppr_lexpr expr) + +ppr_expr (DictApp expr [dname]) + = hang (ppr_lexpr expr) 4 (ppr dname) + +ppr_expr (DictApp expr dnames) + = hang (ppr_lexpr expr) + 4 (brackets (interpp'SP dnames)) + +ppr_expr (HsCoerce co_fn e) = ppr_expr e + +ppr_expr (HsType id) = ppr id + +ppr_expr (HsSpliceE s) = pprSplice s +ppr_expr (HsBracket b) = pprHsBracket b +ppr_expr (HsBracketOut e []) = ppr e +ppr_expr (HsBracketOut e ps) = ppr e $$ ptext SLIT("pending") <+> ppr ps + +ppr_expr (HsProc pat (L _ (HsCmdTop cmd _ _ _))) + = hsep [ptext SLIT("proc"), ppr pat, ptext SLIT("->"), ppr cmd] + +ppr_expr (HsArrApp arrow arg _ HsFirstOrderApp True) + = hsep [ppr_lexpr arrow, ptext SLIT("-<"), ppr_lexpr arg] +ppr_expr (HsArrApp arrow arg _ HsFirstOrderApp False) + = hsep [ppr_lexpr arg, ptext SLIT(">-"), ppr_lexpr arrow] +ppr_expr (HsArrApp arrow arg _ HsHigherOrderApp True) + = hsep [ppr_lexpr arrow, ptext SLIT("-<<"), ppr_lexpr arg] +ppr_expr (HsArrApp arrow arg _ HsHigherOrderApp False) + = hsep [ppr_lexpr arg, ptext SLIT(">>-"), ppr_lexpr arrow] + +ppr_expr (HsArrForm (L _ (HsVar v)) (Just _) [arg1, arg2]) + = sep [pprCmdArg (unLoc arg1), hsep [pprInfix v, pprCmdArg (unLoc arg2)]] +ppr_expr (HsArrForm op _ args) + = hang (ptext SLIT("(|") <> ppr_lexpr op) + 4 (sep (map (pprCmdArg.unLoc) args) <> ptext SLIT("|)")) + +pprCmdArg :: OutputableBndr id => HsCmdTop id -> SDoc +pprCmdArg (HsCmdTop cmd@(L _ (HsArrForm _ Nothing [])) _ _ _) + = ppr_lexpr cmd +pprCmdArg (HsCmdTop cmd _ _ _) + = parens (ppr_lexpr cmd) + +-- Put a var in backquotes if it's not an operator already +pprInfix :: Outputable name => name -> SDoc +pprInfix v | isOperator ppr_v = ppr_v + | otherwise = char '`' <> ppr_v <> char '`' + where + ppr_v = ppr v + +-- add parallel array brackets around a document +-- +pa_brackets :: SDoc -> SDoc +pa_brackets p = ptext SLIT("[:") <> p <> ptext SLIT(":]") +\end{code} + +Parenthesize unless very simple: +\begin{code} +pprParendExpr :: OutputableBndr id => LHsExpr id -> SDoc +pprParendExpr expr + = let + pp_as_was = ppr_lexpr expr + -- Using ppr_expr here avoids the call to 'deeper' + -- Not sure if that's always right. + in + case unLoc expr of + HsLit l -> ppr l + HsOverLit l -> ppr l + + HsVar _ -> pp_as_was + HsIPVar _ -> pp_as_was + ExplicitList _ _ -> pp_as_was + ExplicitPArr _ _ -> pp_as_was + ExplicitTuple _ _ -> pp_as_was + HsPar _ -> pp_as_was + HsBracket _ -> pp_as_was + HsBracketOut _ [] -> pp_as_was + + _ -> parens pp_as_was +\end{code} + +%************************************************************************ +%* * +\subsection{Commands (in arrow abstractions)} +%* * +%************************************************************************ + +We re-use HsExpr to represent these. + +\begin{code} +type HsCmd id = HsExpr id + +type LHsCmd id = LHsExpr id + +data HsArrAppType = HsHigherOrderApp | HsFirstOrderApp +\end{code} + +The legal constructors for commands are: + + = HsArrApp ... -- as above + + | HsArrForm ... -- as above + + | HsApp (HsCmd id) + (HsExpr id) + + | HsLam (Match id) -- kappa + + -- the renamer turns this one into HsArrForm + | OpApp (HsExpr id) -- left operand + (HsCmd id) -- operator + Fixity -- Renamer adds fixity; bottom until then + (HsCmd id) -- right operand + + | HsPar (HsCmd id) -- parenthesised command + + | HsCase (HsExpr id) + [Match id] -- bodies are HsCmd's + SrcLoc + + | HsIf (HsExpr id) -- predicate + (HsCmd id) -- then part + (HsCmd id) -- else part + SrcLoc + + | HsLet (HsLocalBinds id) -- let(rec) + (HsCmd id) + + | HsDo (HsStmtContext Name) -- The parameterisation is unimportant + -- because in this context we never use + -- the PatGuard or ParStmt variant + [Stmt id] -- HsExpr's are really HsCmd's + PostTcType -- Type of the whole expression + SrcLoc + +Top-level command, introducing a new arrow. +This may occur inside a proc (where the stack is empty) or as an +argument of a command-forming operator. + +\begin{code} +type LHsCmdTop id = Located (HsCmdTop id) + +data HsCmdTop id + = HsCmdTop (LHsCmd id) + [PostTcType] -- types of inputs on the command's stack + PostTcType -- return type of the command + (SyntaxTable id) + -- after type checking: + -- names used in the command's desugaring +\end{code} + +%************************************************************************ +%* * +\subsection{Record binds} +%* * +%************************************************************************ + +\begin{code} +type HsRecordBinds id = [(Located id, LHsExpr id)] + +recBindFields :: HsRecordBinds id -> [id] +recBindFields rbinds = [unLoc field | (field,_) <- rbinds] + +pp_rbinds :: OutputableBndr id => SDoc -> HsRecordBinds id -> SDoc +pp_rbinds thing rbinds + = hang thing + 4 (braces (sep (punctuate comma (map (pp_rbind) rbinds)))) + where + pp_rbind (v, e) = hsep [pprBndr LetBind (unLoc v), char '=', ppr e] +\end{code} + + + +%************************************************************************ +%* * +\subsection{@Match@, @GRHSs@, and @GRHS@ datatypes} +%* * +%************************************************************************ + +@Match@es are sets of pattern bindings and right hand sides for +functions, patterns or case branches. For example, if a function @g@ +is defined as: +\begin{verbatim} +g (x,y) = y +g ((x:ys),y) = y+1, +\end{verbatim} +then \tr{g} has two @Match@es: @(x,y) = y@ and @((x:ys),y) = y+1@. + +It is always the case that each element of an @[Match]@ list has the +same number of @pats@s inside it. This corresponds to saying that +a function defined by pattern matching must have the same number of +patterns in each equation. + +\begin{code} +data MatchGroup id + = MatchGroup + [LMatch id] -- The alternatives + PostTcType -- The type is the type of the entire group + -- t1 -> ... -> tn -> tr + -- where there are n patterns + +type LMatch id = Located (Match id) + +data Match id + = Match + [LPat id] -- The patterns + (Maybe (LHsType id)) -- A type signature for the result of the match + -- Nothing after typechecking + (GRHSs id) + +matchGroupArity :: MatchGroup id -> Arity +matchGroupArity (MatchGroup (match:matches) _) + = ASSERT( all ((== n_pats) . length . hsLMatchPats) matches ) + -- Assertion just checks that all the matches have the same number of pats + n_pats + where + n_pats = length (hsLMatchPats match) + +hsLMatchPats :: LMatch id -> [LPat id] +hsLMatchPats (L _ (Match pats _ _)) = pats + +-- GRHSs are used both for pattern bindings and for Matches +data GRHSs id + = GRHSs [LGRHS id] -- Guarded RHSs + (HsLocalBinds id) -- The where clause + +type LGRHS id = Located (GRHS id) + +data GRHS id = GRHS [LStmt id] -- Guards + (LHsExpr id) -- Right hand side +\end{code} + +We know the list must have at least one @Match@ in it. + +\begin{code} +pprMatches :: (OutputableBndr id) => HsMatchContext id -> MatchGroup id -> SDoc +pprMatches ctxt (MatchGroup matches _) = vcat (map (pprMatch ctxt) (map unLoc matches)) + +-- Exported to HsBinds, which can't see the defn of HsMatchContext +pprFunBind :: (OutputableBndr id) => id -> MatchGroup id -> SDoc +pprFunBind fun matches = pprMatches (FunRhs fun) matches + +-- Exported to HsBinds, which can't see the defn of HsMatchContext +pprPatBind :: (OutputableBndr bndr, OutputableBndr id) + => LPat bndr -> GRHSs id -> SDoc +pprPatBind pat grhss = sep [ppr pat, nest 4 (pprGRHSs PatBindRhs grhss)] + + +pprMatch :: OutputableBndr id => HsMatchContext id -> Match id -> SDoc +pprMatch ctxt (Match pats maybe_ty grhss) + = pp_name ctxt <+> sep [sep (map ppr pats), + ppr_maybe_ty, + nest 2 (pprGRHSs ctxt grhss)] + where + pp_name (FunRhs fun) = ppr fun -- Not pprBndr; the AbsBinds will + -- have printed the signature + pp_name LambdaExpr = char '\\' + pp_name other = empty + + ppr_maybe_ty = case maybe_ty of + Just ty -> dcolon <+> ppr ty + Nothing -> empty + + +pprGRHSs :: OutputableBndr id => HsMatchContext id -> GRHSs id -> SDoc +pprGRHSs ctxt (GRHSs grhss binds) + = vcat (map (pprGRHS ctxt . unLoc) grhss) + $$ + (if isEmptyLocalBinds binds then empty + else text "where" $$ nest 4 (pprBinds binds)) + +pprGRHS :: OutputableBndr id => HsMatchContext id -> GRHS id -> SDoc + +pprGRHS ctxt (GRHS [] expr) + = pp_rhs ctxt expr + +pprGRHS ctxt (GRHS guards expr) + = sep [char '|' <+> interpp'SP guards, pp_rhs ctxt expr] + +pp_rhs ctxt rhs = matchSeparator ctxt <+> pprDeeper (ppr rhs) +\end{code} + +%************************************************************************ +%* * +\subsection{Do stmts and list comprehensions} +%* * +%************************************************************************ + +\begin{code} +type LStmt id = Located (Stmt id) + +-- The SyntaxExprs in here are used *only* for do-notation, which +-- has rebindable syntax. Otherwise they are unused. +data Stmt id + = BindStmt (LPat id) + (LHsExpr id) + (SyntaxExpr id) -- The (>>=) operator + (SyntaxExpr id) -- The fail operator + -- The fail operator is noSyntaxExpr + -- if the pattern match can't fail + + | ExprStmt (LHsExpr id) + (SyntaxExpr id) -- The (>>) operator + PostTcType -- Element type of the RHS (used for arrows) + + | LetStmt (HsLocalBinds id) + + -- ParStmts only occur in a list comprehension + | ParStmt [([LStmt id], [id])] -- After renaming, the ids are the binders + -- bound by the stmts and used subsequently + + -- Recursive statement (see Note [RecStmt] below) + | RecStmt [LStmt id] + --- The next two fields are only valid after renaming + [id] -- The ids are a subset of the variables bound by the stmts + -- that are used in stmts that follow the RecStmt + + [id] -- Ditto, but these variables are the "recursive" ones, that + -- are used before they are bound in the stmts of the RecStmt + -- From a type-checking point of view, these ones have to be monomorphic + + --- These fields are only valid after typechecking + [PostTcExpr] -- These expressions correspond + -- 1-to-1 with the "recursive" [id], and are the expresions that + -- should be returned by the recursion. They may not quite be the + -- Ids themselves, because the Id may be *polymorphic*, but + -- the returned thing has to be *monomorphic*. + (DictBinds id) -- Method bindings of Ids bound by the RecStmt, + -- and used afterwards +\end{code} + +ExprStmts are a bit tricky, because what they mean +depends on the context. Consider the following contexts: + + A do expression of type (m res_ty) + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + * ExprStmt E any_ty: do { ....; E; ... } + E :: m any_ty + Translation: E >> ... + + A list comprehensions of type [elt_ty] + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + * ExprStmt E Bool: [ .. | .... E ] + [ .. | ..., E, ... ] + [ .. | .... | ..., E | ... ] + E :: Bool + Translation: if E then fail else ... + + A guard list, guarding a RHS of type rhs_ty + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + * ExprStmt E Bool: f x | ..., E, ... = ...rhs... + E :: Bool + Translation: if E then fail else ... + +Array comprehensions are handled like list comprehensions -=chak + +Note [RecStmt] +~~~~~~~~~~~~~~ +Example: + HsDo [ BindStmt x ex + + , RecStmt [a::forall a. a -> a, b] + [a::Int -> Int, c] + [ BindStmt b (return x) + , LetStmt a = ea + , BindStmt c ec ] + + , return (a b) ] + +Here, the RecStmt binds a,b,c; but + - Only a,b are used in the stmts *following* the RecStmt, + This 'a' is *polymorphic' + - Only a,c are used in the stmts *inside* the RecStmt + *before* their bindings + This 'a' is monomorphic + +Nota Bene: the two a's have different types, even though they +have the same Name. + + +\begin{code} +instance OutputableBndr id => Outputable (Stmt id) where + ppr stmt = pprStmt stmt + +pprStmt (BindStmt pat expr _ _) = hsep [ppr pat, ptext SLIT("<-"), ppr expr] +pprStmt (LetStmt binds) = hsep [ptext SLIT("let"), pprBinds binds] +pprStmt (ExprStmt expr _ _) = ppr expr +pprStmt (ParStmt stmtss) = hsep (map (\stmts -> ptext SLIT("| ") <> ppr stmts) stmtss) +pprStmt (RecStmt segment _ _ _ _) = ptext SLIT("rec") <+> braces (vcat (map ppr segment)) + +pprDo :: OutputableBndr id => HsStmtContext any -> [LStmt id] -> LHsExpr id -> SDoc +pprDo DoExpr stmts body = hang (ptext SLIT("do")) 2 (vcat (map ppr stmts) $$ ppr body) +pprDo (MDoExpr _) stmts body = hang (ptext SLIT("mdo")) 3 (vcat (map ppr stmts) $$ ppr body) +pprDo ListComp stmts body = pprComp brackets stmts body +pprDo PArrComp stmts body = pprComp pa_brackets stmts body + +pprComp :: OutputableBndr id => (SDoc -> SDoc) -> [LStmt id] -> LHsExpr id -> SDoc +pprComp brack quals body + = brack $ + hang (ppr body <+> char '|') + 4 (interpp'SP quals) +\end{code} + +%************************************************************************ +%* * + Template Haskell quotation brackets +%* * +%************************************************************************ + +\begin{code} +data HsSplice id = HsSplice -- $z or $(f 4) + id -- The id is just a unique name to + (LHsExpr id) -- identify this splice point + +instance OutputableBndr id => Outputable (HsSplice id) where + ppr = pprSplice + +pprSplice :: OutputableBndr id => HsSplice id -> SDoc +pprSplice (HsSplice n e) = char '$' <> brackets (ppr n) <> pprParendExpr e + + +data HsBracket id = ExpBr (LHsExpr id) -- [| expr |] + | PatBr (LPat id) -- [p| pat |] + | DecBr (HsGroup id) -- [d| decls |] + | TypBr (LHsType id) -- [t| type |] + | VarBr id -- 'x, ''T + +instance OutputableBndr id => Outputable (HsBracket id) where + ppr = pprHsBracket + + +pprHsBracket (ExpBr e) = thBrackets empty (ppr e) +pprHsBracket (PatBr p) = thBrackets (char 'p') (ppr p) +pprHsBracket (DecBr d) = thBrackets (char 'd') (ppr d) +pprHsBracket (TypBr t) = thBrackets (char 't') (ppr t) +pprHsBracket (VarBr n) = char '\'' <> ppr n + -- Infelicity: can't show ' vs '', because + -- we can't ask n what its OccName is, because the + -- pretty-printer for HsExpr doesn't ask for NamedThings + -- But the pretty-printer for names will show the OccName class + +thBrackets pp_kind pp_body = char '[' <> pp_kind <> char '|' <+> + pp_body <+> ptext SLIT("|]") +\end{code} + +%************************************************************************ +%* * +\subsection{Enumerations and list comprehensions} +%* * +%************************************************************************ + +\begin{code} +data ArithSeqInfo id + = From (LHsExpr id) + | FromThen (LHsExpr id) + (LHsExpr id) + | FromTo (LHsExpr id) + (LHsExpr id) + | FromThenTo (LHsExpr id) + (LHsExpr id) + (LHsExpr id) +\end{code} + +\begin{code} +instance OutputableBndr id => Outputable (ArithSeqInfo id) where + ppr (From e1) = hcat [ppr e1, pp_dotdot] + ppr (FromThen e1 e2) = hcat [ppr e1, comma, space, ppr e2, pp_dotdot] + ppr (FromTo e1 e3) = hcat [ppr e1, pp_dotdot, ppr e3] + ppr (FromThenTo e1 e2 e3) + = hcat [ppr e1, comma, space, ppr e2, pp_dotdot, ppr e3] + +pp_dotdot = ptext SLIT(" .. ") +\end{code} + + +%************************************************************************ +%* * +\subsection{HsMatchCtxt} +%* * +%************************************************************************ + +\begin{code} +data HsMatchContext id -- Context of a Match + = FunRhs id -- Function binding for f + | CaseAlt -- Guard on a case alternative + | LambdaExpr -- Pattern of a lambda + | ProcExpr -- Pattern of a proc + | PatBindRhs -- Pattern binding + | RecUpd -- Record update [used only in DsExpr to tell matchWrapper + -- what sort of runtime error message to generate] + | StmtCtxt (HsStmtContext id) -- Pattern of a do-stmt or list comprehension + deriving () + +data HsStmtContext id + = ListComp + | DoExpr + | MDoExpr PostTcTable -- Recursive do-expression + -- (tiresomely, it needs table + -- of its return/bind ops) + | PArrComp -- Parallel array comprehension + | PatGuard (HsMatchContext id) -- Pattern guard for specified thing + | ParStmtCtxt (HsStmtContext id) -- A branch of a parallel stmt +\end{code} + +\begin{code} +isDoExpr :: HsStmtContext id -> Bool +isDoExpr DoExpr = True +isDoExpr (MDoExpr _) = True +isDoExpr other = False +\end{code} + +\begin{code} +matchSeparator (FunRhs _) = ptext SLIT("=") +matchSeparator CaseAlt = ptext SLIT("->") +matchSeparator LambdaExpr = ptext SLIT("->") +matchSeparator ProcExpr = ptext SLIT("->") +matchSeparator PatBindRhs = ptext SLIT("=") +matchSeparator (StmtCtxt _) = ptext SLIT("<-") +matchSeparator RecUpd = panic "unused" +\end{code} + +\begin{code} +pprMatchContext (FunRhs fun) = ptext SLIT("the definition of") <+> quotes (ppr fun) +pprMatchContext CaseAlt = ptext SLIT("a case alternative") +pprMatchContext RecUpd = ptext SLIT("a record-update construct") +pprMatchContext PatBindRhs = ptext SLIT("a pattern binding") +pprMatchContext LambdaExpr = ptext SLIT("a lambda abstraction") +pprMatchContext ProcExpr = ptext SLIT("an arrow abstraction") +pprMatchContext (StmtCtxt ctxt) = ptext SLIT("a pattern binding in") $$ pprStmtContext ctxt + +pprMatchRhsContext (FunRhs fun) = ptext SLIT("a right-hand side of function") <+> quotes (ppr fun) +pprMatchRhsContext CaseAlt = ptext SLIT("the body of a case alternative") +pprMatchRhsContext PatBindRhs = ptext SLIT("the right-hand side of a pattern binding") +pprMatchRhsContext LambdaExpr = ptext SLIT("the body of a lambda") +pprMatchRhsContext ProcExpr = ptext SLIT("the body of a proc") +pprMatchRhsContext RecUpd = panic "pprMatchRhsContext" + +pprStmtContext (ParStmtCtxt c) = sep [ptext SLIT("a parallel branch of"), pprStmtContext c] +pprStmtContext (PatGuard ctxt) = ptext SLIT("a pattern guard for") $$ pprMatchContext ctxt +pprStmtContext DoExpr = ptext SLIT("a 'do' expression") +pprStmtContext (MDoExpr _) = ptext SLIT("an 'mdo' expression") +pprStmtContext ListComp = ptext SLIT("a list comprehension") +pprStmtContext PArrComp = ptext SLIT("an array comprehension") + +-- Used for the result statement of comprehension +-- e.g. the 'e' in [ e | ... ] +-- or the 'r' in f x = r +pprStmtResultContext (PatGuard ctxt) = pprMatchRhsContext ctxt +pprStmtResultContext other = ptext SLIT("the result of") <+> pprStmtContext other + + +-- Used to generate the string for a *runtime* error message +matchContextErrString (FunRhs fun) = "function " ++ showSDoc (ppr fun) +matchContextErrString CaseAlt = "case" +matchContextErrString PatBindRhs = "pattern binding" +matchContextErrString RecUpd = "record update" +matchContextErrString LambdaExpr = "lambda" +matchContextErrString ProcExpr = "proc" +matchContextErrString (StmtCtxt (ParStmtCtxt c)) = matchContextErrString (StmtCtxt c) +matchContextErrString (StmtCtxt (PatGuard _)) = "pattern guard" +matchContextErrString (StmtCtxt DoExpr) = "'do' expression" +matchContextErrString (StmtCtxt (MDoExpr _)) = "'mdo' expression" +matchContextErrString (StmtCtxt ListComp) = "list comprehension" +matchContextErrString (StmtCtxt PArrComp) = "array comprehension" +\end{code} |