X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FhsSyn%2FHsExpr.lhs;h=8ea0c4fbf57fe9c06e1fa2cc7f417d0d455f9dc9;hp=5b552c6385bd7dc5a3d813a646f2701bf7559c50;hb=e5c3b478b3cd1707cf122833822f44b2ac09b8e9;hpb=ce43dfc719eda4752d8de67cefb61d03b05b8e3c diff --git a/compiler/hsSyn/HsExpr.lhs b/compiler/hsSyn/HsExpr.lhs index 5b552c6..8ea0c4f 100644 --- a/compiler/hsSyn/HsExpr.lhs +++ b/compiler/hsSyn/HsExpr.lhs @@ -2,17 +2,10 @@ % (c) The University of Glasgow 2006 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % - -HsExpr: Abstract Haskell syntax: expressions - \begin{code} -{-# OPTIONS -w #-} --- The above warning supression flag is a temporary kludge. --- While working on this module you are encouraged to remove it and fix --- any warnings in the module. See --- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings --- for details +{-# LANGUAGE DeriveDataTypeable #-} +-- | Abstract Haskell syntax for expressions. module HsExpr where #include "HsVersions.h" @@ -22,7 +15,6 @@ import HsDecls import HsPat import HsLit import HsTypes -import HsImpExp import HsBinds -- others: @@ -31,76 +23,92 @@ import Name import BasicTypes import DataCon import SrcLoc -import Outputable +import Util( dropTail ) +import StaticFlags( opt_PprStyle_Debug ) +import Outputable import FastString + +-- libraries: +import Data.Data hiding (Fixity) \end{code} %************************************************************************ -%* * +%* * \subsection{Expressions proper} -%* * +%* * %************************************************************************ \begin{code} +-- * Expressions proper + 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 +-- | PostTcExpr is an evidence expression attached to the syntax tree by the +-- type checker (c.f. postTcType). type PostTcExpr = HsExpr Id -type PostTcTable = [(Name, Id)] +-- | We use a PostTcTable where there are a bunch of pieces of evidence, more +-- than is convenient to keep individually. +type PostTcTable = [(Name, PostTcExpr)] noPostTcExpr :: PostTcExpr -noPostTcExpr = HsLit (HsString FSLIT("noPostTcExpr")) +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 +-- | 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 +-- etc 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")) +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 +-- ^ Currently used only for 'CmdTop' (sigh) -- --- * After the renamer, it takes the form [(std_name, HsVar actual_name)] +-- * 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, )] --- where is the evidence for the method +-- * 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, )]@ +-- where @@ is the evidence for the method noSyntaxTable :: SyntaxTable id noSyntaxTable = [] ------------------------- +-- | A Haskell expression. data HsExpr id - = HsVar id -- variable - | HsIPVar (IPName id) -- implicit parameter - | HsOverLit (HsOverLit id) -- Overloaded literals - | HsLit HsLit -- Simple (non-overloaded) literals + = 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 + | HsLam (MatchGroup id) -- Currently always a single match - | HsApp (LHsExpr id) -- Application - (LHsExpr id) + | HsApp (LHsExpr id) (LHsExpr id) -- Application + + | HsKappa (MatchGroup id) + + | HsKappaApp (LHsExpr id) (LHsExpr id) -- Operator applications: -- NB Bracketed ops such as (+) come out as Vars. @@ -108,176 +116,213 @@ data HsExpr id -- 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 + | 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 + + | ExplicitTuple -- Used for explicit tuples and sections thereof + [HsTupArg id] + Boxity + + | HsCase (LHsExpr id) + (MatchGroup id) + + | HsIf (Maybe (SyntaxExpr id)) -- cond function + -- Nothing => use the built-in 'if' + -- See Note [Rebindable if] + (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 + 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] + + -- 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) +-- (HsMatchGroup Id) -- Filled in by the type checker to be +-- -- a match that does the job + [DataCon] -- Filled in by the type checker to the + -- _non-empty_ list of DataCons that have + -- all the upd'd fields + [PostTcType] -- Argument types of *input* record type + [PostTcType] -- and *output* record type + -- For a type family, the arg types are of the *instance* tycon, + -- not the family tycon + + | ExprWithTySig -- e :: type + (LHsExpr id) + (LHsType id) - | NegApp (LHsExpr id) -- negated expr - (SyntaxExpr id) -- Name of 'negate' + | ExprWithTySigOut -- TRANSLATION + (LHsExpr id) + (LHsType Name) -- Retain the signature for + -- round-tripping purposes - | HsPar (LHsExpr id) -- parenthesised expr + | ArithSeq -- arithmetic sequence + PostTcExpr + (ArithSeqInfo id) - | 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) - [DataCon] -- Filled in by the type checker to the *non-empty* - -- list of DataCons that have all the upd'd fields - [PostTcType] -- Argument types of *input* record type - [PostTcType] -- and *output* record type - -- For a type family, the arg types are of the *instance* tycon, not the family tycon - - | 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 + | PArrSeq -- arith. sequence for parallel array + PostTcExpr -- [:e1..e2:] or [:e1, e2..e3:] + (ArithSeqInfo id) + + | HsSCC FastString -- "set cost centre" SCC pragma + (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 + | 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) - | HsSpliceE (HsSplice id) + | HsQuasiQuoteE (HsQuasiQuote id) + -- See Note [Quasi-quote overview] in TcSplice ----------------------------------------------------------- -- Arrow notation extension - | HsProc (LPat id) -- arrow abstraction, proc - (LHsCmdTop id) -- body of the abstraction - -- always has an empty stack + | HsProc (LPat id) -- arrow abstraction, proc + (LHsCmdTop id) -- body of the abstraction + -- always has an empty stack + + ----------------------------------------------------------- + -- Heterogeneous Metaprogramming extension + + | HsHetMetBrak PostTcType (LHsExpr id) -- code type brackets + | HsHetMetEsc PostTcType PostTcType (LHsExpr id) -- code type escape + | HsHetMetCSP PostTcType (LHsExpr id) -- code type cross-stage persistence --------------------------------------- -- 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) + | 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 + | 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 --------------------------------------- -- Haskell program coverage (Hpc) Support - | HsTick - Int -- module-local tick number + | HsTick + Int -- module-local tick number [id] -- variables in scope - (LHsExpr id) -- sub-expression + (LHsExpr id) -- sub-expression | HsBinTick - Int -- module-local tick number for True - Int -- module-local tick number for False - (LHsExpr id) -- sub-expression + Int -- module-local tick number for True + Int -- module-local tick number for False + (LHsExpr id) -- sub-expression - | HsTickPragma -- A pragma introduced tick - (FastString,(Int,Int),(Int,Int)) -- external span for this tick - (LHsExpr id) + | HsTickPragma -- A pragma introduced tick + (FastString,(Int,Int),(Int,Int)) -- external span for this tick + (LHsExpr id) --------------------------------------- -- These constructors only appear temporarily in the parser. -- The renamer translates them into the Right Thing. - | EWildPat -- wildcard + | EWildPat -- wildcard - | EAsPat (Located id) -- as pattern - (LHsExpr id) + | EAsPat (Located id) -- as pattern + (LHsExpr id) - | ELazyPat (LHsExpr id) -- ~ pattern + | EViewPat (LHsExpr id) -- view pattern + (LHsExpr id) - | HsType (LHsType id) -- Explicit type argument; e.g f {| Int |} x y + | ELazyPat (LHsExpr id) -- ~ pattern + + | HsType (LHsType id) -- Explicit type argument; e.g f {| Int |} x y --------------------------------------- -- Finally, HsWrap appears only in typechecker output - | HsWrap HsWrapper -- TRANSLATION - (HsExpr id) + | HsWrap HsWrapper -- TRANSLATION + (HsExpr id) + deriving (Data, Typeable) + +-- HsTupArg is used for tuple sections +-- (,a,) is represented by ExplicitTuple [Mising ty1, Present a, Missing ty3] +-- Which in turn stands for (\x:ty1 \y:ty2. (x,a,y)) +data HsTupArg id + = Present (LHsExpr id) -- The argument + | Missing PostTcType -- The argument is missing, but this is its type + deriving (Data, Typeable) -type PendingSplice = (Name, LHsExpr Id) -- Typechecked splices, waiting to be - -- pasted back in by the desugarer +tupArgPresent :: HsTupArg id -> Bool +tupArgPresent (Present {}) = True +tupArgPresent (Missing {}) = False + +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} +Note [Rebindable if] +~~~~~~~~~~~~~~~~~~~~ +The rebindable syntax for 'if' is a bit special, because when +rebindable syntax is *off* we do not want to treat + (if c then t else e) +as if it was an application (ifThenElse c t e). Why not? +Because we allow an 'if' to return *unboxed* results, thus + if blah then 3# else 4# +whereas that would not be possible using a all to a polymorphic function +(because you can't call a polymorphic function at an unboxed type). + +So we use Nothing to mean "use the old built-in typing rule". \begin{code} instance OutputableBndr id => Outputable (HsExpr id) where @@ -286,7 +331,7 @@ instance OutputableBndr id => Outputable (HsExpr id) where \begin{code} ----------------------- --- pprExpr, pprLExpr, pprBinds call pprDeeper; +-- pprExpr, pprLExpr, pprBinds call pprDeeper; -- the underscore versions do not pprLExpr :: OutputableBndr id => LHsExpr id -> SDoc pprLExpr (L _ e) = pprExpr e @@ -305,22 +350,29 @@ isQuietHsExpr (HsApp _ _) = True isQuietHsExpr (OpApp _ _ _ _) = True isQuietHsExpr _ = False -pprBinds :: OutputableBndr id => HsLocalBinds id -> SDoc +pprBinds :: (OutputableBndr idL, OutputableBndr idR) + => HsLocalBindsLR idL idR -> 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 :: OutputableBndr id => HsExpr id -> SDoc +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 (HsPar e) = parens (ppr_lexpr e) +ppr_expr (HsPar e) = parens (ppr_lexpr e) +ppr_expr (HsHetMetBrak _ e) = ptext (sLit "<[") <> (ppr_lexpr e) <> ptext (sLit "]>") +ppr_expr (HsHetMetEsc _ _ e) = ptext (sLit "~~") <> (ppr_lexpr e) +ppr_expr (HsHetMetCSP _ e) = ptext (sLit "%%") <> (ppr_lexpr e) ppr_expr (HsCoreAnn s e) - = vcat [ptext SLIT("HsCoreAnn") <+> ftext s, ppr_lexpr e] + = vcat [ptext (sLit "HsCoreAnn") <+> ftext s, ppr_lexpr e] +ppr_expr (HsKappaApp e1 e2) = ppr_expr $ HsApp e1 e2 +ppr_expr (HsKappa e) = ppr_expr $ HsLam e ppr_expr (HsApp e1 e2) = let (fun, args) = collect_args e1 [e2] in hang (ppr_lexpr fun) 2 (sep (map pprParendExpr args)) @@ -328,68 +380,82 @@ ppr_expr (HsApp e1 e2) 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) +ppr_expr (OpApp e1 op _ e2) = case unLoc op of HsVar v -> pp_infixly v - _ -> pp_prefixly + _ -> pp_prefixly where - pp_e1 = pprDebugParendExpr e1 -- In debug mode, add parens + pp_e1 = pprDebugParendExpr e1 -- In debug mode, add parens pp_e2 = pprDebugParendExpr e2 -- to make precedence clear pp_prefixly = hang (ppr op) 2 (sep [pp_e1, pp_e2]) pp_infixly v - = sep [nest 2 pp_e1, pprInfix v, nest 2 pp_e2] + = sep [nest 2 pp_e1, pprHsInfix v, nest 2 pp_e2] ppr_expr (NegApp e _) = char '-' <+> pprDebugParendExpr e ppr_expr (SectionL expr op) = case unLoc op of HsVar v -> pp_infixly v - _ -> pp_prefixly + _ -> pp_prefixly where pp_expr = pprDebugParendExpr 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]) + 4 (hsep [pp_expr, ptext (sLit "x_ )")]) + pp_infixly v = (sep [pp_expr, pprHsInfix v]) ppr_expr (SectionR op expr) = case unLoc op of HsVar v -> pp_infixly v - _ -> pp_prefixly + _ -> pp_prefixly where pp_expr = pprDebugParendExpr expr - pp_prefixly = hang (hsep [text "( \\ x_ ->", ppr op, ptext SLIT("x_")]) - 4 ((<>) pp_expr rparen) + 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) ] + = (sep [pprHsInfix v, pp_expr]) -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)] +ppr_expr (ExplicitTuple exprs boxity) + = tupleParens boxity (fcat (ppr_tup_args exprs)) + where + ppr_tup_args [] = [] + ppr_tup_args (Present e : es) = (ppr_lexpr e <> punc es) : ppr_tup_args es + ppr_tup_args (Missing _ : es) = punc es : ppr_tup_args es + + punc (Present {} : _) = comma <> space + punc (Missing {} : _) = comma + punc [] = empty + +--avoid using PatternSignatures for stage1 code portability +ppr_expr exprType@(HsLam matches) + = pprMatches (LambdaExpr `asTypeOf` idType exprType) matches + where idType :: HsExpr id -> HsMatchContext id; idType = undefined + +ppr_expr exprType@(HsCase expr matches) + = sep [ sep [ptext (sLit "case"), nest 4 (ppr expr), ptext (sLit "of {")], + nest 2 (pprMatches (CaseAlt `asTypeOf` idType exprType) matches <+> char '}') ] + where idType :: HsExpr id -> HsMatchContext id; idType = undefined + +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] + = 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)] + = 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 (HsDo do_or_list_comp stmts _) = pprDo do_or_list_comp stmts ppr_expr (ExplicitList _ exprs) = brackets (pprDeeperList fsep (punctuate comma (map ppr_lexpr exprs))) @@ -397,10 +463,7 @@ ppr_expr (ExplicitList _ exprs) ppr_expr (ExplicitPArr _ exprs) = pa_brackets (pprDeeperList 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) +ppr_expr (RecordCon con_id _ rbinds) = hang (ppr con_id) 2 (ppr rbinds) ppr_expr (RecordUpd aexp rbinds _ _ _) @@ -408,58 +471,73 @@ ppr_expr (RecordUpd aexp rbinds _ _ _) ppr_expr (ExprWithTySig expr sig) = hang (nest 2 (ppr_lexpr expr) <+> dcolon) - 4 (ppr sig) + 4 (ppr sig) ppr_expr (ExprWithTySigOut expr sig) = hang (nest 2 (ppr_lexpr expr) <+> dcolon) - 4 (ppr sig) + 4 (ppr sig) -ppr_expr (ArithSeq expr info) = brackets (ppr info) -ppr_expr (PArrSeq expr info) = pa_brackets (ppr info) +ppr_expr (ArithSeq _ info) = brackets (ppr info) +ppr_expr (PArrSeq _ 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 EWildPat = char '_' +ppr_expr (ELazyPat e) = char '~' <> pprParendExpr e +ppr_expr (EAsPat v e) = ppr v <> char '@' <> pprParendExpr e +ppr_expr (EViewPat p e) = ppr p <+> ptext (sLit "->") <+> ppr e ppr_expr (HsSCC lbl expr) - = sep [ ptext SLIT("_scc_") <+> doubleQuotes (ftext lbl), pprParendExpr expr ] + = sep [ ptext (sLit "_scc_") <+> doubleQuotes (ftext lbl), + pprParendExpr expr ] ppr_expr (HsWrap co_fn e) = pprHsWrapper (pprExpr e) co_fn -ppr_expr (HsType id) = ppr id +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 $$ ptext SLIT("pending") <+> ppr ps +ppr_expr (HsBracketOut e []) = ppr e +ppr_expr (HsBracketOut e ps) = ppr e $$ ptext (sLit "pending") <+> ppr ps +ppr_expr (HsQuasiQuoteE qq) = ppr qq ppr_expr (HsProc pat (L _ (HsCmdTop cmd _ _ _))) - = hsep [ptext SLIT("proc"), ppr pat, ptext SLIT("->"), ppr cmd] + = hsep [ptext (sLit "proc"), ppr pat, ptext (sLit "->"), ppr cmd] ppr_expr (HsTick tickId vars exp) - = hcat [ptext SLIT("tick<"), ppr tickId,ptext SLIT(">("), hsep (map pprHsVar vars), ppr exp,ptext SLIT(")")] + = pprTicks (ppr exp) $ + hcat [ptext (sLit "tick<"), + ppr tickId, + ptext (sLit ">("), + hsep (map pprHsVar vars), + ppr exp, + ptext (sLit ")")] ppr_expr (HsBinTick tickIdTrue tickIdFalse exp) - = hcat [ptext SLIT("bintick<"), - ppr tickIdTrue, - ptext SLIT(","), - ppr tickIdFalse, - ptext SLIT(">("), - ppr exp,ptext SLIT(")")] + = pprTicks (ppr exp) $ + hcat [ptext (sLit "bintick<"), + ppr tickIdTrue, + ptext (sLit ","), + ppr tickIdFalse, + ptext (sLit ">("), + ppr exp,ptext (sLit ")")] ppr_expr (HsTickPragma externalSrcLoc exp) - = hcat [ptext SLIT("tickpragma<"), ppr externalSrcLoc,ptext SLIT(">("), ppr exp,ptext SLIT(")")] + = pprTicks (ppr exp) $ + hcat [ptext (sLit "tickpragma<"), + ppr externalSrcLoc, + ptext (sLit ">("), + ppr exp, + ptext (sLit ")")] ppr_expr (HsArrApp arrow arg _ HsFirstOrderApp True) - = hsep [ppr_lexpr arrow, ptext SLIT("-<"), ppr_lexpr arg] + = 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] + = 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] + = 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] + = 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)]] + = sep [pprCmdArg (unLoc arg1), hsep [pprHsInfix v, pprCmdArg (unLoc arg2)]] ppr_expr (HsArrForm op _ args) - = hang (ptext SLIT("(|") <> ppr_lexpr op) - 4 (sep (map (pprCmdArg.unLoc) args) <> ptext SLIT("|)")) + = 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 [])) _ _ _) @@ -467,17 +545,13 @@ pprCmdArg (HsCmdTop cmd@(L _ (HsArrForm _ Nothing [])) _ _ _) 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 +instance OutputableBndr id => Outputable (HsCmdTop id) where + ppr = pprCmdArg -- add parallel array brackets around a document -- pa_brackets :: SDoc -> SDoc -pa_brackets p = ptext SLIT("[:") <> p <> ptext SLIT(":]") +pa_brackets p = ptext (sLit "[:") <> p <> ptext (sLit ":]") \end{code} HsSyn records exactly where the user put parens, with HsPar. @@ -495,44 +569,46 @@ pprDebugParendExpr :: OutputableBndr id => LHsExpr id -> SDoc pprDebugParendExpr expr = getPprStyle (\sty -> if debugStyle sty then pprParendExpr expr - else pprLExpr expr) - + else pprLExpr expr) + pprParendExpr :: OutputableBndr id => LHsExpr id -> SDoc pprParendExpr expr = let - pp_as_was = pprLExpr expr - -- Using pprLExpr makes sure that we go 'deeper' - -- I think that is usually (always?) right + pp_as_was = pprLExpr expr + -- Using pprLExpr makes sure that we go 'deeper' + -- I think that is usually (always?) right in case unLoc expr of - HsLit l -> pp_as_was - HsOverLit l -> pp_as_was - 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 - HsDo sc _ _ _ + ArithSeq {} -> pp_as_was + PArrSeq {} -> pp_as_was + HsLit {} -> pp_as_was + HsOverLit {} -> pp_as_was + HsVar {} -> pp_as_was + HsIPVar {} -> pp_as_was + ExplicitTuple {} -> pp_as_was + ExplicitList {} -> pp_as_was + ExplicitPArr {} -> pp_as_was + HsPar {} -> pp_as_was + HsBracket {} -> pp_as_was + HsBracketOut _ [] -> pp_as_was + HsDo sc _ _ | isListCompExpr sc -> pp_as_was - _ -> parens pp_as_was + _ -> parens pp_as_was -isAtomicHsExpr :: HsExpr id -> Bool -- A single token +isAtomicHsExpr :: HsExpr id -> Bool -- A single token isAtomicHsExpr (HsVar {}) = True isAtomicHsExpr (HsLit {}) = True isAtomicHsExpr (HsOverLit {}) = True isAtomicHsExpr (HsIPVar {}) = True isAtomicHsExpr (HsWrap _ e) = isAtomicHsExpr e isAtomicHsExpr (HsPar e) = isAtomicHsExpr (unLoc e) -isAtomicHsExpr e = False +isAtomicHsExpr _ = False \end{code} %************************************************************************ -%* * +%* * \subsection{Commands (in arrow abstractions)} -%* * +%* * %************************************************************************ We re-use HsExpr to represent these. @@ -543,45 +619,47 @@ type HsCmd id = HsExpr id type LHsCmd id = LHsExpr id data HsArrAppType = HsHigherOrderApp | HsFirstOrderApp + deriving (Data, Typeable) \end{code} The legal constructors for commands are: - = HsArrApp ... -- as above + = HsArrApp ... -- as above - | HsArrForm ... -- as above + | HsArrForm ... -- as above - | HsApp (HsCmd id) - (HsExpr id) + | HsApp (HsCmd id) + (HsExpr id) - | HsLam (Match id) -- kappa + | 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 + | OpApp (HsExpr id) -- left operand + (HsCmd id) -- operator + Fixity -- Renamer adds fixity; bottom until then + (HsCmd id) -- right operand - | HsPar (HsCmd id) -- parenthesised command + | HsPar (HsCmd id) -- parenthesised command - | HsCase (HsExpr id) - [Match id] -- bodies are HsCmd's - SrcLoc + | HsCase (HsExpr id) + [Match id] -- bodies are HsCmd's + SrcLoc - | HsIf (HsExpr id) -- predicate - (HsCmd id) -- then part - (HsCmd id) -- else part - SrcLoc + | HsIf (Maybe (SyntaxExpr id)) -- cond function + (HsExpr id) -- predicate + (HsCmd id) -- then part + (HsCmd id) -- else part + SrcLoc - | HsLet (HsLocalBinds id) -- let(rec) - (HsCmd id) + | 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 + | 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 @@ -591,18 +669,18 @@ argument of a command-forming operator. 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 + = 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 + deriving (Data, Typeable) \end{code} %************************************************************************ -%* * +%* * \subsection{Record binds} -%* * +%* * %************************************************************************ \begin{code} @@ -612,9 +690,9 @@ type HsRecordBinds id = HsRecFields id (LHsExpr id) %************************************************************************ -%* * +%* * \subsection{@Match@, @GRHSs@, and @GRHS@ datatypes} -%* * +%* * %************************************************************************ @Match@es are sets of pattern bindings and right hand sides for @@ -632,28 +710,33 @@ 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 +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 + deriving (Data, Typeable) 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) + [LPat id] -- The patterns + (Maybe (LHsType id)) -- A type signature for the result of the match + -- Nothing after typechecking + (GRHSs id) + deriving (Data, Typeable) + +isEmptyMatchGroup :: MatchGroup id -> Bool +isEmptyMatchGroup (MatchGroup ms _) = null ms matchGroupArity :: MatchGroup id -> Arity -matchGroupArity (MatchGroup [] _) - = panic "matchGroupArity" -- MatchGroup is never empty +matchGroupArity (MatchGroup [] _) + = panic "matchGroupArity" -- Precondition: MatchGroup is non-empty matchGroupArity (MatchGroup (match:matches) _) = ASSERT( all ((== n_pats) . length . hsLMatchPats) matches ) - -- Assertion just checks that all the matches have the same number of pats + -- Assertion just checks that all the matches have the same number of pats n_pats where n_pats = length (hsLMatchPats match) @@ -661,73 +744,85 @@ matchGroupArity (MatchGroup (match:matches) _) 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 +-- | GRHSs are used both for pattern bindings and for Matches +data GRHSs id + = GRHSs { + grhssGRHSs :: [LGRHS id], -- ^ Guarded RHSs + grhssLocalBinds :: (HsLocalBinds id) -- ^ The where clause + } deriving (Data, Typeable) type LGRHS id = Located (GRHS id) -data GRHS id = GRHS [LStmt id] -- Guards - (LHsExpr id) -- Right hand side +-- | Guarded Right Hand Side. +data GRHS id = GRHS [LStmt id] -- Guards + (LHsExpr id) -- Right hand side + deriving (Data, Typeable) \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 ty) = vcat (map (pprMatch ctxt) (map unLoc matches)) - -- Don't print the type; it's only - -- a place-holder before typechecking +pprMatches :: (OutputableBndr idL, OutputableBndr idR) => HsMatchContext idL -> MatchGroup idR -> SDoc +pprMatches ctxt (MatchGroup matches _) + = vcat (map (pprMatch ctxt) (map unLoc matches)) + -- Don't print the type; it's only a place-holder before typechecking -- Exported to HsBinds, which can't see the defn of HsMatchContext -pprFunBind :: (OutputableBndr id) => id -> Bool -> MatchGroup id -> SDoc +pprFunBind :: (OutputableBndr idL, OutputableBndr idR) => idL -> Bool -> MatchGroup idR -> SDoc pprFunBind fun inf matches = pprMatches (FunRhs fun inf) 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)] + => LPat bndr -> GRHSs id -> SDoc +pprPatBind pat ty@(grhss) + = sep [ppr pat, nest 2 (pprGRHSs (PatBindRhs `asTypeOf` idType ty) grhss)] +--avoid using PatternSignatures for stage1 code portability + where idType :: GRHSs id -> HsMatchContext id; idType = undefined -pprMatch :: OutputableBndr id => HsMatchContext id -> Match id -> SDoc +pprMatch :: (OutputableBndr idL, OutputableBndr idR) => HsMatchContext idL -> Match idR -> SDoc pprMatch ctxt (Match pats maybe_ty grhss) - = herald <+> sep [sep (map ppr other_pats), - ppr_maybe_ty, - nest 2 (pprGRHSs ctxt grhss)] + = sep [ sep (herald : map (nest 2 . pprParendLPat) other_pats) + , nest 2 ppr_maybe_ty + , nest 2 (pprGRHSs ctxt grhss) ] where - (herald, other_pats) - = case ctxt of - FunRhs fun is_infix - | not is_infix -> (ppr fun, pats) - -- f x y z = e - -- Not pprBndr; the AbsBinds will - -- have printed the signature - - | null pats3 -> (pp_infix, []) - -- x &&& y = e - - | otherwise -> (parens pp_infix, pats3) - -- (x &&& y) z = e - where - (pat1:pat2:pats3) = pats - pp_infix = ppr pat1 <+> ppr fun <+> ppr pat2 - - LambdaExpr -> (char '\\', pats) - other -> (empty, pats) - + (herald, other_pats) + = case ctxt of + FunRhs fun is_infix + | not is_infix -> (ppr fun, pats) + -- f x y z = e + -- Not pprBndr; the AbsBinds will + -- have printed the signature + + | null pats2 -> (pp_infix, []) + -- x &&& y = e + + | otherwise -> (parens pp_infix, pats2) + -- (x &&& y) z = e + where + pp_infix = pprParendLPat pat1 <+> ppr fun <+> pprParendLPat pat2 + + LambdaExpr -> (char '\\', pats) + + _ -> ASSERT( null pats1 ) + (ppr pat1, []) -- No parens around the single pat + + (pat1:pats1) = pats + (pat2:pats2) = pats1 ppr_maybe_ty = case maybe_ty of - Just ty -> dcolon <+> ppr ty - Nothing -> empty + Just ty -> dcolon <+> ppr ty + Nothing -> empty -pprGRHSs :: OutputableBndr id => HsMatchContext id -> GRHSs id -> SDoc +pprGRHSs :: (OutputableBndr idL, OutputableBndr idR) + => HsMatchContext idL -> GRHSs idR -> SDoc pprGRHSs ctxt (GRHSs grhss binds) = vcat (map (pprGRHS ctxt . unLoc) grhss) - $$ if isEmptyLocalBinds binds then empty - else text "where" $$ nest 4 (pprBinds binds) + $$ ppUnless (isEmptyLocalBinds binds) + (text "where" $$ nest 4 (pprBinds binds)) -pprGRHS :: OutputableBndr id => HsMatchContext id -> GRHS id -> SDoc +pprGRHS :: (OutputableBndr idL, OutputableBndr idR) + => HsMatchContext idL -> GRHS idR -> SDoc pprGRHS ctxt (GRHS [] expr) = pp_rhs ctxt expr @@ -735,296 +830,589 @@ pprGRHS ctxt (GRHS [] expr) pprGRHS ctxt (GRHS guards expr) = sep [char '|' <+> interpp'SP guards, pp_rhs ctxt expr] +pp_rhs :: OutputableBndr idR => HsMatchContext idL -> LHsExpr idR -> SDoc 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 +type LStmt id = Located (StmtLR id id) +type LStmtLR idL idR = Located (StmtLR idL idR) + +type Stmt id = StmtLR id id + +-- The SyntaxExprs in here are used *only* for do-notation and monad +-- comprehensions, which have rebindable syntax. Otherwise they are unused. +data StmtLR idL idR + = LastStmt -- Always the last Stmt in ListComp, MonadComp, PArrComp, + -- and (after the renamer) DoExpr, MDoExpr + -- Not used for GhciStmt, PatGuard, which scope over other stuff + (LHsExpr idR) + (SyntaxExpr idR) -- The return operator, used only for MonadComp + -- For ListComp, PArrComp, we use the baked-in 'return' + -- For DoExpr, MDoExpr, we don't appply a 'return' at all + -- See Note [Monad Comprehensions] + | BindStmt (LPat idL) + (LHsExpr idR) + (SyntaxExpr idR) -- The (>>=) operator; see Note [The type of bind] + (SyntaxExpr idR) -- The fail operator + -- The fail operator is noSyntaxExpr + -- if the pattern match can't fail + + | ExprStmt (LHsExpr idR) -- See Note [ExprStmt] + (SyntaxExpr idR) -- The (>>) operator + (SyntaxExpr idR) -- The `guard` operator; used only in MonadComp + -- See notes [Monad Comprehensions] + PostTcType -- Element type of the RHS (used for arrows) + + | LetStmt (HsLocalBindsLR idL idR) + + -- ParStmts only occur in a list/monad comprehension + | ParStmt [([LStmt idL], [idR])] + (SyntaxExpr idR) -- Polymorphic `mzip` for monad comprehensions + (SyntaxExpr idR) -- The `>>=` operator + (SyntaxExpr idR) -- Polymorphic `return` operator + -- with type (forall a. a -> m a) + -- See notes [Monad Comprehensions] + -- After renaming, the ids are the binders + -- bound by the stmts and used after themp + + | TransStmt { + trS_form :: TransForm, + trS_stmts :: [LStmt idL], -- Stmts to the *left* of the 'group' + -- which generates the tuples to be grouped + + trS_bndrs :: [(idR, idR)], -- See Note [TransStmt binder map] + + trS_using :: LHsExpr idR, + trS_by :: Maybe (LHsExpr idR), -- "by e" (optional) + -- Invariant: if trS_form = GroupBy, then grp_by = Just e + + trS_ret :: SyntaxExpr idR, -- The monomorphic 'return' function for + -- the inner monad comprehensions + trS_bind :: SyntaxExpr idR, -- The '(>>=)' operator + trS_fmap :: SyntaxExpr idR -- The polymorphic 'fmap' function for desugaring + -- Only for 'group' forms + } -- See Note [Monad Comprehensions] + + -- Recursive statement (see Note [How RecStmt works] below) + | RecStmt + { recS_stmts :: [LStmtLR idL idR] + + -- The next two fields are only valid after renaming + , recS_later_ids :: [idR] -- The ids are a subset of the variables bound by the + -- stmts that are used in stmts that follow the RecStmt + + , recS_rec_ids :: [idR] -- Ditto, but these variables are the "recursive" ones, + -- that are used before they are bound in the stmts of + -- the RecStmt. + -- An Id can be in both groups + -- Both sets of Ids are (now) treated monomorphically + -- See Note [How RecStmt works] for why they are separate + + -- Rebindable syntax + , recS_bind_fn :: SyntaxExpr idR -- The bind function + , recS_ret_fn :: SyntaxExpr idR -- The return function + , recS_mfix_fn :: SyntaxExpr idR -- The mfix function + + -- These fields are only valid after typechecking + , recS_rec_rets :: [PostTcExpr] -- These expressions correspond 1-to-1 with + -- recS_rec_ids, and are the + -- expressions 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*, + -- so they may be type applications + + , recS_ret_ty :: PostTcType -- The type of of do { stmts; return (a,b,c) } + -- With rebindable syntax the type might not + -- be quite as simple as (m (tya, tyb, tyc)). + } + deriving (Data, Typeable) + +data TransForm -- The 'f' below is the 'using' function, 'e' is the by function + = ThenForm -- then f or then f by e + | GroupFormU -- group using f or group using f by e + | GroupFormB -- group by e + -- In the GroupByFormB, trS_using is filled in with + -- 'groupWith' (list comprehensions) or + -- 'groupM' (monad comprehensions) + deriving (Data, Typeable) \end{code} +Note [The type of bind in Stmts] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Some Stmts, notably BindStmt, keep the (>>=) bind operator. +We do NOT assume that it has type + (>>=) :: m a -> (a -> m b) -> m b +In some cases (see Trac #303, #1537) it might have a more +exotic type, such as + (>>=) :: m i j a -> (a -> m j k b) -> m i k b +So we must be careful not to make assumptions about the type. +In particular, the monad may not be uniform throughout. + +Note [TransStmt binder map] +~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The [(idR,idR)] in a TransStmt behaves as follows: + + * Before renaming: [] + + * After renaming: + [ (x27,x27), ..., (z35,z35) ] + These are the variables + bound by the stmts to the left of the 'group' + and used either in the 'by' clause, + or in the stmts following the 'group' + Each item is a pair of identical variables. + + * After typechecking: + [ (x27:Int, x27:[Int]), ..., (z35:Bool, z35:[Bool]) ] + Each pair has the same unique, but different *types*. + +Note [ExprStmt] +~~~~~~~~~~~~~~~ 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] -~~~~~~~~~~~~~~ + 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 ... + + A monad comprehension of type (m res_ty) + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + * ExprStmt E Bool: [ .. | .... E ] + E :: Bool + Translation: guard E >> ... + +Array comprehensions are handled like list comprehensions. + +Note [How RecStmt works] +~~~~~~~~~~~~~~~~~~~~~~~~ Example: - HsDo [ BindStmt x ex + 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 ] + , RecStmt { recS_rec_ids = [a, c] + , recS_stmts = [ BindStmt b (return (a,c)) + , LetStmt a = ...b... + , BindStmt c ec ] + , recS_later_ids = [a, b] - , return (a b) ] + , 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' +Here, the RecStmt binds a,b,c; but + - Only a,b are used in the stmts *following* the RecStmt, - Only a,c are used in the stmts *inside* the RecStmt - *before* their bindings - This 'a' is monomorphic + *before* their bindings + +Why do we need *both* rec_ids and later_ids? For monads they could be +combined into a single set of variables, but not for arrows. That +follows from the types of the respective feedback operators: + + mfix :: MonadFix m => (a -> m a) -> m a + loop :: ArrowLoop a => a (b,d) (c,d) -> a b c + +* For mfix, the 'a' covers the union of the later_ids and the rec_ids +* For 'loop', 'c' is the later_ids and 'd' is the rec_ids + +Note [Typing a RecStmt] +~~~~~~~~~~~~~~~~~~~~~~~ +A (RecStmt stmts) types as if you had written + + (v1,..,vn, _, ..., _) <- mfix (\~(_, ..., _, r1, ..., rm) -> + do { stmts + ; return (v1,..vn, r1, ..., rm) }) + +where v1..vn are the later_ids + r1..rm are the rec_ids + +Note [Monad Comprehensions] +~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Monad comprehensions require separate functions like 'return' and +'>>=' for desugaring. These functions are stored in the statements +used in monad comprehensions. For example, the 'return' of the 'LastStmt' +expression is used to lift the body of the monad comprehension: + + [ body | stmts ] + => + stmts >>= \bndrs -> return body + +In transform and grouping statements ('then ..' and 'then group ..') the +'return' function is required for nested monad comprehensions, for example: + + [ body | stmts, then f, rest ] + => + f [ env | stmts ] >>= \bndrs -> [ body | rest ] + +ExprStmts require the 'Control.Monad.guard' function for boolean +expressions: + + [ body | exp, stmts ] + => + guard exp >> [ body | stmts ] + +Grouping/parallel statements require the 'Control.Monad.Group.groupM' and +'Control.Monad.Zip.mzip' functions: -Nota Bene: the two a's have different types, even though they -have the same Name. + [ body | stmts, then group by e, rest] + => + groupM [ body | stmts ] >>= \bndrs -> [ body | rest ] + + [ body | stmts1 | stmts2 | .. ] + => + mzip stmts1 (mzip stmts2 (..)) >>= \(bndrs1, (bndrs2, ..)) -> return body + +In any other context than 'MonadComp', the fields for most of these +'SyntaxExpr's stay bottom. \begin{code} -instance OutputableBndr id => Outputable (Stmt id) where +instance (OutputableBndr idL, OutputableBndr idR) => Outputable (StmtLR idL idR) 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 = ptext SLIT("do") <+> pprDeeperList vcat (map ppr stmts ++ [ppr body]) -pprDo (MDoExpr _) stmts body = ptext SLIT("mdo") <+> pprDeeperList vcat (map ppr stmts ++ [ppr body]) -pprDo ListComp stmts body = pprComp brackets stmts body -pprDo PArrComp stmts body = pprComp pa_brackets stmts body -pprDo other stmts body = panic "pprDo" -- PatGuard, ParStmtCxt - -pprComp :: OutputableBndr id => (SDoc -> SDoc) -> [LStmt id] -> LHsExpr id -> SDoc -pprComp brack quals body - = brack $ - hang (ppr body <+> char '|') - 4 (interpp'SP quals) +pprStmt :: (OutputableBndr idL, OutputableBndr idR) => (StmtLR idL idR) -> SDoc +pprStmt (LastStmt expr _) = ifPprDebug (ptext (sLit "[last]")) <+> ppr expr +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 doStmts stmtss) + where doStmts stmts = ptext (sLit "| ") <> ppr stmts + +pprStmt (TransStmt { trS_stmts = stmts, trS_by = by, trS_using = using, trS_form = form }) + = sep (ppr_lc_stmts stmts ++ [pprTransStmt by using form]) + +pprStmt (RecStmt { recS_stmts = segment, recS_rec_ids = rec_ids + , recS_later_ids = later_ids }) + = ptext (sLit "rec") <+> + vcat [ braces (vcat (map ppr segment)) + , ifPprDebug (vcat [ ptext (sLit "rec_ids=") <> ppr rec_ids + , ptext (sLit "later_ids=") <> ppr later_ids])] + +pprTransformStmt :: OutputableBndr id => [id] -> LHsExpr id -> Maybe (LHsExpr id) -> SDoc +pprTransformStmt bndrs using by + = sep [ ptext (sLit "then") <+> ifPprDebug (braces (ppr bndrs)) + , nest 2 (ppr using) + , nest 2 (pprBy by)] + +pprTransStmt :: OutputableBndr id => Maybe (LHsExpr id) + -> LHsExpr id -> TransForm + -> SDoc +pprTransStmt by using ThenForm + = sep [ ptext (sLit "then"), nest 2 (ppr using), nest 2 (pprBy by)] +pprTransStmt by _ GroupFormB + = sep [ ptext (sLit "then group"), nest 2 (pprBy by) ] +pprTransStmt by using GroupFormU + = sep [ ptext (sLit "then group"), nest 2 (pprBy by), nest 2 (ptext (sLit "using") <+> ppr using)] + +pprBy :: OutputableBndr id => Maybe (LHsExpr id) -> SDoc +pprBy Nothing = empty +pprBy (Just e) = ptext (sLit "by") <+> ppr e + +pprDo :: OutputableBndr id => HsStmtContext any -> [LStmt id] -> SDoc +pprDo DoExpr stmts = ptext (sLit "do") <+> ppr_do_stmts stmts +pprDo GhciStmt stmts = ptext (sLit "do") <+> ppr_do_stmts stmts +pprDo ArrowExpr stmts = ptext (sLit "do") <+> ppr_do_stmts stmts +pprDo MDoExpr stmts = ptext (sLit "mdo") <+> ppr_do_stmts stmts +pprDo ListComp stmts = brackets $ pprComp stmts +pprDo PArrComp stmts = pa_brackets $ pprComp stmts +pprDo MonadComp stmts = brackets $ pprComp stmts +pprDo _ _ = panic "pprDo" -- PatGuard, ParStmtCxt + +ppr_do_stmts :: OutputableBndr id => [LStmt id] -> SDoc +-- Print a bunch of do stmts, with explicit braces and semicolons, +-- so that we are not vulnerable to layout bugs +ppr_do_stmts stmts + = lbrace <+> pprDeeperList vcat (punctuate semi (map ppr stmts)) + <+> rbrace + +ppr_lc_stmts :: OutputableBndr id => [LStmt id] -> [SDoc] +ppr_lc_stmts stmts = [ppr s <> comma | s <- stmts] + +pprComp :: OutputableBndr id => [LStmt id] -> SDoc +pprComp quals -- Prints: body | qual1, ..., qualn + | not (null quals) + , L _ (LastStmt body _) <- last quals + = hang (ppr body <+> char '|') 2 (interpp'SP (dropTail 1 quals)) + | otherwise + = pprPanic "pprComp" (interpp'SP quals) \end{code} %************************************************************************ -%* * - Template Haskell quotation brackets -%* * +%* * + 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 - +data HsSplice id = HsSplice -- $z or $(f 4) + id -- The id is just a unique name to + (LHsExpr id) -- identify this splice point + deriving (Data, Typeable) + instance OutputableBndr id => Outputable (HsSplice id) where ppr = pprSplice pprSplice :: OutputableBndr id => HsSplice id -> SDoc -pprSplice (HsSplice n e) = char '$' <> ifPprDebug (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 +pprSplice (HsSplice n e) + = char '$' <> ifPprDebug (brackets (ppr n)) <> eDoc + where + -- We use pprLExpr to match pprParendExpr: + -- Using pprLExpr makes sure that we go 'deeper' + -- I think that is usually (always?) right + pp_as_was = pprLExpr e + eDoc = case unLoc e of + HsPar _ -> pp_as_was + HsVar _ -> pp_as_was + _ -> parens pp_as_was + +data HsBracket id = ExpBr (LHsExpr id) -- [| expr |] + | PatBr (LPat id) -- [p| pat |] + | DecBrL [LHsDecl id] -- [d| decls |]; result of parser + | DecBrG (HsGroup id) -- [d| decls |]; result of renamer + | TypBr (LHsType id) -- [t| type |] + | VarBr id -- 'x, ''T + deriving (Data, Typeable) 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("|]") +pprHsBracket :: OutputableBndr id => HsBracket id -> SDoc +pprHsBracket (ExpBr e) = thBrackets empty (ppr e) +pprHsBracket (PatBr p) = thBrackets (char 'p') (ppr p) +pprHsBracket (DecBrG gp) = thBrackets (char 'd') (ppr gp) +pprHsBracket (DecBrL ds) = thBrackets (char 'd') (vcat (map ppr ds)) +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 :: SDoc -> SDoc -> SDoc +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) + = From (LHsExpr id) + | FromThen (LHsExpr id) + (LHsExpr id) + | FromTo (LHsExpr id) + (LHsExpr id) + | FromThenTo (LHsExpr id) + (LHsExpr id) + (LHsExpr id) + deriving (Data, Typeable) \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 (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(" .. ") +pp_dotdot :: SDoc +pp_dotdot = ptext (sLit " .. ") \end{code} %************************************************************************ -%* * +%* * \subsection{HsMatchCtxt} -%* * +%* * %************************************************************************ \begin{code} -data HsMatchContext id -- Context of a Match - = FunRhs id Bool -- Function binding for f; True <=> written infix - | 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 HsMatchContext id -- Context of a Match + = FunRhs id Bool -- Function binding for f; True <=> written infix + | LambdaExpr -- Patterns of a lambda + | CaseAlt -- Patterns and guards on a case alternative + | ProcExpr -- Patterns of a proc + | PatBindRhs -- A pattern binding eg [y] <- e = e + + | 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, list comprehension, + -- pattern guard, etc + + | ThPatQuote -- A Template Haskell pattern quotation [p| (a,b) |] + deriving (Data, Typeable) 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 + = ListComp + | MonadComp + | PArrComp -- Parallel array comprehension + + | DoExpr -- do { ... } + | MDoExpr -- mdo { ... } ie recursive do-expression + | ArrowExpr -- do-notation in an arrow-command context + + | GhciStmt -- A command-line Stmt in GHCi pat <- rhs + | PatGuard (HsMatchContext id) -- Pattern guard for specified thing + | ParStmtCtxt (HsStmtContext id) -- A branch of a parallel stmt + | TransStmtCtxt (HsStmtContext id) -- A branch of a transform stmt + deriving (Data, Typeable) \end{code} \begin{code} -isDoExpr :: HsStmtContext id -> Bool -isDoExpr DoExpr = True -isDoExpr (MDoExpr _) = True -isDoExpr _ = False - isListCompExpr :: HsStmtContext id -> Bool -isListCompExpr ListComp = True -isListCompExpr PArrComp = True -isListCompExpr _ = False +-- Uses syntax [ e | quals ] +isListCompExpr ListComp = True +isListCompExpr PArrComp = True +isListCompExpr MonadComp = True +isListCompExpr (ParStmtCtxt c) = isListCompExpr c +isListCompExpr (TransStmtCtxt c) = isListCompExpr c +isListCompExpr _ = False + +isMonadCompExpr :: HsStmtContext id -> Bool +isMonadCompExpr MonadComp = True +isMonadCompExpr (ParStmtCtxt ctxt) = isMonadCompExpr ctxt +isMonadCompExpr (TransStmtCtxt ctxt) = isMonadCompExpr ctxt +isMonadCompExpr _ = 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 :: HsMatchContext id -> SDoc +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" +matchSeparator ThPatQuote = 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") $$ pprStmtContext ctxt - -pprStmtContext (ParStmtCtxt c) = sep [ptext SLIT("a parallel branch of"), pprStmtContext c] -pprStmtContext (PatGuard ctxt) = ptext SLIT("a pattern guard for") $$ 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") - -{- -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 other = panic "pprMatchRhsContext" -- RecUpd, StmtCtxt - --- 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 --} +pprMatchContext :: Outputable id => HsMatchContext id -> SDoc +pprMatchContext ctxt + | want_an ctxt = ptext (sLit "an") <+> pprMatchContextNoun ctxt + | otherwise = ptext (sLit "a") <+> pprMatchContextNoun ctxt + where + want_an (FunRhs {}) = True -- Use "an" in front + want_an ProcExpr = True + want_an _ = False + +pprMatchContextNoun :: Outputable id => HsMatchContext id -> SDoc +pprMatchContextNoun (FunRhs fun _) = ptext (sLit "equation for") + <+> quotes (ppr fun) +pprMatchContextNoun CaseAlt = ptext (sLit "case alternative") +pprMatchContextNoun RecUpd = ptext (sLit "record-update construct") +pprMatchContextNoun ThPatQuote = ptext (sLit "Template Haskell pattern quotation") +pprMatchContextNoun PatBindRhs = ptext (sLit "pattern binding") +pprMatchContextNoun LambdaExpr = ptext (sLit "lambda abstraction") +pprMatchContextNoun ProcExpr = ptext (sLit "arrow abstraction") +pprMatchContextNoun (StmtCtxt ctxt) = ptext (sLit "pattern binding in") + $$ pprStmtContext ctxt + +----------------- +pprAStmtContext, pprStmtContext :: Outputable id => HsStmtContext id -> SDoc +pprAStmtContext ctxt = article <+> pprStmtContext ctxt + where + pp_an = ptext (sLit "an") + pp_a = ptext (sLit "a") + article = case ctxt of + MDoExpr -> pp_an + PArrComp -> pp_an + GhciStmt -> pp_an + _ -> pp_a + + +----------------- +pprStmtContext GhciStmt = ptext (sLit "interactive GHCi command") +pprStmtContext DoExpr = ptext (sLit "'do' block") +pprStmtContext MDoExpr = ptext (sLit "'mdo' block") +pprStmtContext ArrowExpr = ptext (sLit "'do' block in an arrow command") +pprStmtContext ListComp = ptext (sLit "list comprehension") +pprStmtContext MonadComp = ptext (sLit "monad comprehension") +pprStmtContext PArrComp = ptext (sLit "array comprehension") +pprStmtContext (PatGuard ctxt) = ptext (sLit "pattern guard for") $$ pprMatchContext ctxt + +-- Drop the inner contexts when reporting errors, else we get +-- Unexpected transform statement +-- in a transformed branch of +-- transformed branch of +-- transformed branch of monad comprehension +pprStmtContext (ParStmtCtxt c) + | opt_PprStyle_Debug = sep [ptext (sLit "parallel branch of"), pprAStmtContext c] + | otherwise = pprStmtContext c +pprStmtContext (TransStmtCtxt c) + | opt_PprStyle_Debug = sep [ptext (sLit "transformed branch of"), pprAStmtContext c] + | otherwise = pprStmtContext c + -- 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" +matchContextErrString :: Outputable id => HsMatchContext id -> SDoc +matchContextErrString (FunRhs fun _) = ptext (sLit "function") <+> ppr fun +matchContextErrString CaseAlt = ptext (sLit "case") +matchContextErrString PatBindRhs = ptext (sLit "pattern binding") +matchContextErrString RecUpd = ptext (sLit "record update") +matchContextErrString LambdaExpr = ptext (sLit "lambda") +matchContextErrString ProcExpr = ptext (sLit "proc") +matchContextErrString ThPatQuote = panic "matchContextErrString" -- Not used at runtime +matchContextErrString (StmtCtxt (ParStmtCtxt c)) = matchContextErrString (StmtCtxt c) +matchContextErrString (StmtCtxt (TransStmtCtxt c)) = matchContextErrString (StmtCtxt c) +matchContextErrString (StmtCtxt (PatGuard _)) = ptext (sLit "pattern guard") +matchContextErrString (StmtCtxt GhciStmt) = ptext (sLit "interactive GHCi command") +matchContextErrString (StmtCtxt DoExpr) = ptext (sLit "'do' block") +matchContextErrString (StmtCtxt ArrowExpr) = ptext (sLit "'do' block") +matchContextErrString (StmtCtxt MDoExpr) = ptext (sLit "'mdo' block") +matchContextErrString (StmtCtxt ListComp) = ptext (sLit "list comprehension") +matchContextErrString (StmtCtxt MonadComp) = ptext (sLit "monad comprehension") +matchContextErrString (StmtCtxt PArrComp) = ptext (sLit "array comprehension") +\end{code} + +\begin{code} +pprMatchInCtxt :: (OutputableBndr idL, OutputableBndr idR) + => HsMatchContext idL -> Match idR -> SDoc +pprMatchInCtxt ctxt match = hang (ptext (sLit "In") <+> pprMatchContext ctxt <> colon) + 4 (pprMatch ctxt match) + +pprStmtInCtxt :: (OutputableBndr idL, OutputableBndr idR) + => HsStmtContext idL -> StmtLR idL idR -> SDoc +pprStmtInCtxt ctxt (LastStmt e _) + | isListCompExpr ctxt -- For [ e | .. ], do not mutter about "stmts" + = hang (ptext (sLit "In the expression:")) 2 (ppr e) + +pprStmtInCtxt ctxt stmt + = hang (ptext (sLit "In a stmt of") <+> pprAStmtContext ctxt <> colon) + 2 (ppr_stmt stmt) + where + -- For Group and Transform Stmts, don't print the nested stmts! + ppr_stmt (TransStmt { trS_by = by, trS_using = using + , trS_form = form }) = pprTransStmt by using form + ppr_stmt stmt = pprStmt stmt \end{code}