+++ /dev/null
-%
-% (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}
projects / ghc-hetmet.git / blobdiff