X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FhsSyn%2FHsExpr.lhs;h=f7b693f1573526d13084e6bbbda589a839a47b65;hp=bde737a25387a3deef726f30de0025a1a0f88918;hb=4ac2bb39dffb4b825ece73b349ff0d56d79092d7;hpb=b4556cace1b420341c3e3bc6c1d7a7f693c655e4 diff --git a/compiler/hsSyn/HsExpr.lhs b/compiler/hsSyn/HsExpr.lhs index bde737a..f7b693f 100644 --- a/compiler/hsSyn/HsExpr.lhs +++ b/compiler/hsSyn/HsExpr.lhs @@ -3,6 +3,7 @@ % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \begin{code} +{-# LANGUAGE DeriveDataTypeable #-} -- | Abstract Haskell syntax for expressions. module HsExpr where @@ -22,8 +23,12 @@ import Name import BasicTypes import DataCon import SrcLoc +import Util( dropTail ) import Outputable import FastString + +-- libraries: +import Data.Data hiding (Fixity) \end{code} @@ -44,7 +49,7 @@ type LHsExpr id = Located (HsExpr id) type PostTcExpr = HsExpr Id -- | We use a PostTcTable where there are a bunch of pieces of evidence, more -- than is convenient to keep individually. -type PostTcTable = [(Name, Id)] +type PostTcTable = [(Name, PostTcExpr)] noPostTcExpr :: PostTcExpr noPostTcExpr = HsLit (HsString (fsLit "noPostTcExpr")) @@ -58,7 +63,7 @@ noPostTcTable = [] -- -- 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 +-- etc type SyntaxExpr id = HsExpr id @@ -128,7 +133,10 @@ data HsExpr id | HsCase (LHsExpr id) (MatchGroup id) - | HsIf (LHsExpr id) -- predicate + | 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 @@ -139,8 +147,6 @@ data HsExpr id -- 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 @@ -275,6 +281,7 @@ data 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] @@ -282,6 +289,7 @@ data HsExpr id data HsTupArg id = Present (LHsExpr id) -- The argument | Missing PostTcType -- The argument is missing, but this is its type + deriving (Data, Typeable) tupArgPresent :: HsTupArg id -> Bool tupArgPresent (Present {}) = True @@ -291,11 +299,18 @@ 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 @@ -408,7 +423,7 @@ ppr_expr exprType@(HsCase expr matches) nest 2 (pprMatches (CaseAlt `asTypeOf` idType exprType) matches <+> char '}') ] where idType :: HsExpr id -> HsMatchContext id; idType = undefined -ppr_expr (HsIf e1 e2 e3) +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"), @@ -423,7 +438,7 @@ 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 (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))) @@ -559,7 +574,7 @@ pprParendExpr expr HsPar {} -> pp_as_was HsBracket {} -> pp_as_was HsBracketOut _ [] -> pp_as_was - HsDo sc _ _ _ + HsDo sc _ _ | isListCompExpr sc -> pp_as_was _ -> parens pp_as_was @@ -587,6 +602,7 @@ 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: @@ -612,7 +628,8 @@ The legal constructors for commands are: [Match id] -- bodies are HsCmd's SrcLoc - | HsIf (HsExpr id) -- predicate + | HsIf (Maybe (SyntaxExpr id)) -- cond function + (HsExpr id) -- predicate (HsCmd id) -- then part (HsCmd id) -- else part SrcLoc @@ -640,6 +657,7 @@ data HsCmdTop id PostTcType -- return type of the command (SyntaxTable id) -- after type checking: -- names used in the command's desugaring + deriving (Data, Typeable) \end{code} %************************************************************************ @@ -681,6 +699,7 @@ data MatchGroup id 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) @@ -690,6 +709,7 @@ data Match id (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 @@ -712,13 +732,14 @@ data GRHSs id = GRHSs { grhssGRHSs :: [LGRHS id], -- ^ Guarded RHSs grhssLocalBinds :: (HsLocalBinds id) -- ^ The where clause - } + } deriving (Data, Typeable) type LGRHS id = Located (GRHS id) -- | 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. @@ -737,16 +758,16 @@ pprFunBind fun inf matches = pprMatches (FunRhs fun inf) matches pprPatBind :: (OutputableBndr bndr, OutputableBndr id) => LPat bndr -> GRHSs id -> SDoc pprPatBind pat ty@(grhss) - = sep [ppr pat, nest 4 (pprGRHSs (PatBindRhs `asTypeOf` idType 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 idL, OutputableBndr idR) => HsMatchContext idL -> Match idR -> SDoc pprMatch ctxt (Match pats maybe_ty grhss) - = herald <+> sep [sep (map pprParendLPat 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 @@ -808,10 +829,15 @@ type LStmtLR idL idR = Located (StmtLR idL idR) type Stmt id = StmtLR id id --- The SyntaxExprs in here are used *only* for do-notation, which --- has rebindable syntax. Otherwise they are unused. +-- 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 - = BindStmt (LPat idL) + = LastStmt -- Always the last Stmt in ListComp, MonadComp, PArrComp, DoExpr, MDoExpr + -- Not used for GhciStmt, PatGuard, which scope over other stuff + (LHsExpr idR) + (SyntaxExpr idR) -- The return operator, used only for MonadComp + -- See Note [Monad Comprehensions] + | BindStmt (LPat idL) (LHsExpr idR) (SyntaxExpr idR) -- The (>>=) operator (SyntaxExpr idR) -- The fail operator @@ -820,17 +846,25 @@ data StmtLR idL idR | ExprStmt (LHsExpr idR) -- See Note [ExprStmt] (SyntaxExpr idR) -- The (>>) operator + (SyntaxExpr idR) -- The `guard` operator + -- See notes [Monad Comprehensions] PostTcType -- Element type of the RHS (used for arrows) | LetStmt (HsLocalBindsLR idL idR) - -- ParStmts only occur in a list comprehension + -- 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 them - -- "qs, then f by e" ==> TransformStmt qs binders f (Just e) - -- "qs, then f" ==> TransformStmt qs binders f Nothing + -- "qs, then f by e" ==> TransformStmt qs binders f (Just e) (return) (>>=) + -- "qs, then f" ==> TransformStmt qs binders f Nothing (return) (>>=) | TransformStmt [LStmt idL] -- Stmts are the ones to the left of the 'then' @@ -841,6 +875,11 @@ data StmtLR idL idR (Maybe (LHsExpr idR)) -- "by e" (optional) + (SyntaxExpr idR) -- The 'return' function for inner monad + -- comprehensions + (SyntaxExpr idR) -- The '(>>=)' operator. + -- See Note [Monad Comprehensions] + | GroupStmt [LStmt idL] -- Stmts to the *left* of the 'group' -- which generates the tuples to be grouped @@ -852,7 +891,14 @@ data StmtLR idL idR (Either -- "using f" (LHsExpr idR) -- Left f => explicit "using f" (SyntaxExpr idR)) -- Right f => implicit; filled in with 'groupWith' - + -- (list comprehensions) or 'groupM' (monad + -- comprehensions) + + (SyntaxExpr idR) -- The 'return' function for inner monad + -- comprehensions + (SyntaxExpr idR) -- The '(>>=)' operator + (SyntaxExpr idR) -- The 'liftM' function from Control.Monad for desugaring + -- See Note [Monad Comprehensions] -- Recursive statement (see Note [How RecStmt works] below) | RecStmt @@ -884,9 +930,11 @@ data StmtLR idL idR -- the returned thing has to be *monomorphic*, -- so they may be type applications - , recS_dicts :: DictBinds idR -- Method bindings of Ids bound by the - -- RecStmt, and used afterwards + , 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) \end{code} Note [GroupStmt binder map] @@ -932,6 +980,12 @@ depends on the context. Consider the following contexts: 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 -=chak Note [How RecStmt works] @@ -973,22 +1027,62 @@ A (RecStmt stmts) types as if you had written 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 ] + +Normal expressions 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: + + [ 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 idL, OutputableBndr idR) => Outputable (StmtLR idL idR) where ppr stmt = pprStmt stmt pprStmt :: (OutputableBndr idL, OutputableBndr idR) => (StmtLR idL idR) -> SDoc +pprStmt (LastStmt expr _) = 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) +pprStmt (ExprStmt expr _ _ _) = ppr expr +pprStmt (ParStmt stmtss _ _ _) = hsep (map doStmts stmtss) where doStmts stmts = ptext (sLit "| ") <> ppr stmts -pprStmt (TransformStmt stmts _ using by) - = sep (ppr_lc_stmts stmts ++ [pprTransformStmt using by]) +pprStmt (TransformStmt stmts bndrs using by _ _) + = sep (ppr_lc_stmts stmts ++ [pprTransformStmt bndrs using by]) -pprStmt (GroupStmt stmts _ by using) +pprStmt (GroupStmt stmts _ by using _ _ _) = sep (ppr_lc_stmts stmts ++ [pprGroupStmt by using]) pprStmt (RecStmt { recS_stmts = segment, recS_rec_ids = rec_ids @@ -998,8 +1092,11 @@ pprStmt (RecStmt { recS_stmts = segment, recS_rec_ids = rec_ids , ifPprDebug (vcat [ ptext (sLit "rec_ids=") <> ppr rec_ids , ptext (sLit "later_ids=") <> ppr later_ids])] -pprTransformStmt :: OutputableBndr id => LHsExpr id -> Maybe (LHsExpr id) -> SDoc -pprTransformStmt using by = sep [ ptext (sLit "then"), nest 2 (ppr using), nest 2 (pprBy by)] +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)] pprGroupStmt :: OutputableBndr id => Maybe (LHsExpr id) -> Either (LHsExpr id) (SyntaxExpr is) @@ -1014,27 +1111,32 @@ 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] -> LHsExpr id -> SDoc -pprDo DoExpr stmts body = ptext (sLit "do") <+> ppr_do_stmts stmts body -pprDo GhciStmt stmts body = ptext (sLit "do") <+> ppr_do_stmts stmts body -pprDo (MDoExpr _) stmts body = ptext (sLit "mdo") <+> ppr_do_stmts stmts body -pprDo ListComp stmts body = brackets $ pprComp stmts body -pprDo PArrComp stmts body = pa_brackets $ pprComp stmts body -pprDo _ _ _ = panic "pprDo" -- PatGuard, ParStmtCxt +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 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] -> LHsExpr id -> SDoc +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 body - = lbrace <+> pprDeeperList vcat ([ppr s <> semi | s <- stmts] ++ [ppr body]) +ppr_do_stmts stmts + = lbrace <+> pprDeeperList vcat ([ppr s <> semi | s <- stmts]) <+> rbrace ppr_lc_stmts :: OutputableBndr id => [LStmt id] -> [SDoc] ppr_lc_stmts stmts = [ppr s <> comma | s <- stmts] -pprComp :: OutputableBndr id => [LStmt id] -> LHsExpr id -> SDoc -pprComp quals body -- Prints: body | qual1, ..., qualn - = hang (ppr body <+> char '|') 2 (interpp'SP quals) +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} %************************************************************************ @@ -1047,14 +1149,23 @@ pprComp quals body -- Prints: body | qual1, ..., qualn 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 - + = 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 |] @@ -1062,6 +1173,7 @@ data HsBracket id = ExpBr (LHsExpr id) -- [| expr |] | 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 @@ -1100,6 +1212,7 @@ data ArithSeqInfo id | FromThenTo (LHsExpr id) (LHsExpr id) (LHsExpr id) + deriving (Data, Typeable) \end{code} \begin{code} @@ -1124,40 +1237,53 @@ pp_dotdot = ptext (sLit " .. ") \begin{code} data HsMatchContext id -- Context of a Match = FunRhs id Bool -- Function binding for f; True <=> written infix - | CaseAlt -- Patterns and guards on a case alternative | LambdaExpr -- Patterns of a lambda + | CaseAlt -- Patterns and guards on a case alternative | ProcExpr -- Patterns of a proc - | PatBindRhs -- Patterns in the *guards* of a pattern binding + | 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 or list comprehension + + | StmtCtxt (HsStmtContext id) -- Pattern of a do-stmt, list comprehension, + -- pattern guard, etc + | ThPatQuote -- A Template Haskell pattern quotation [p| (a,b) |] - deriving () + deriving (Data, Typeable) data HsStmtContext id = ListComp - | DoExpr - | GhciStmt -- A command-line Stmt in GHCi pat <- rhs - | MDoExpr PostTcTable -- Recursive do-expression - -- (tiresomely, it needs table - -- of its return/bind ops) + | MonadComp | PArrComp -- Parallel array comprehension + + | DoExpr -- do { ... } + | MDoExpr -- mdo { ... } ie recursive do-expression + + | 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 | TransformStmtCtxt (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 +isDoExpr DoExpr = True +isDoExpr MDoExpr = True +isDoExpr _ = False isListCompExpr :: HsStmtContext id -> Bool -isListCompExpr ListComp = True -isListCompExpr PArrComp = True -isListCompExpr _ = False +isListCompExpr ListComp = True +isListCompExpr PArrComp = True +isListCompExpr MonadComp = True +isListCompExpr _ = False + +isMonadCompExpr :: HsStmtContext id -> Bool +isMonadCompExpr MonadComp = True +isMonadCompExpr (ParStmtCtxt ctxt) = isMonadCompExpr ctxt +isMonadCompExpr (TransformStmtCtxt ctxt) = isMonadCompExpr ctxt +isMonadCompExpr _ = False \end{code} \begin{code} @@ -1174,16 +1300,25 @@ matchSeparator ThPatQuote = panic "unused" \begin{code} pprMatchContext :: Outputable id => HsMatchContext id -> SDoc -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 ThPatQuote = ptext (sLit "a Template Haskell pattern quotation") -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") - $$ pprStmtContext ctxt +pprMatchContext ctxt + | want_an ctxt = ptext (sLit "an") <+> pprMatchContextNoun ctxt + | otherwise = ptext (sLit "a") <+> pprMatchContextNoun ctxt + where + want_an (FunRhs {}) = True -- Use "an" in front + want_an ProcExpr = True + want_an _ = False + +pprMatchContextNoun :: Outputable id => HsMatchContext id -> SDoc +pprMatchContextNoun (FunRhs fun _) = ptext (sLit "equation for") + <+> quotes (ppr fun) +pprMatchContextNoun CaseAlt = ptext (sLit "case alternative") +pprMatchContextNoun RecUpd = ptext (sLit "record-update construct") +pprMatchContextNoun ThPatQuote = ptext (sLit "Template Haskell pattern quotation") +pprMatchContextNoun PatBindRhs = ptext (sLit "pattern binding") +pprMatchContextNoun LambdaExpr = ptext (sLit "lambda abstraction") +pprMatchContextNoun ProcExpr = ptext (sLit "arrow abstraction") +pprMatchContextNoun (StmtCtxt ctxt) = ptext (sLit "pattern binding in") + $$ pprStmtContext ctxt pprStmtContext :: Outputable id => HsStmtContext id -> SDoc pprStmtContext (ParStmtCtxt c) @@ -1194,8 +1329,9 @@ pprStmtContext (PatGuard ctxt) = ptext (sLit "a pattern guard for") $$ pprMatchContext ctxt pprStmtContext GhciStmt = ptext (sLit "an interactive GHCi command") pprStmtContext DoExpr = ptext (sLit "a 'do' expression") -pprStmtContext (MDoExpr _) = ptext (sLit "an 'mdo' expression") +pprStmtContext MDoExpr = ptext (sLit "an 'mdo' expression") pprStmtContext ListComp = ptext (sLit "a list comprehension") +pprStmtContext MonadComp = ptext (sLit "a monad comprehension") pprStmtContext PArrComp = ptext (sLit "an array comprehension") {- @@ -1227,8 +1363,9 @@ matchContextErrString (StmtCtxt (TransformStmtCtxt c)) = matchContextErrString ( matchContextErrString (StmtCtxt (PatGuard _)) = ptext (sLit "pattern guard") matchContextErrString (StmtCtxt GhciStmt) = ptext (sLit "interactive GHCi command") matchContextErrString (StmtCtxt DoExpr) = ptext (sLit "'do' expression") -matchContextErrString (StmtCtxt (MDoExpr _)) = ptext (sLit "'mdo' expression") +matchContextErrString (StmtCtxt MDoExpr) = ptext (sLit "'mdo' expression") matchContextErrString (StmtCtxt ListComp) = ptext (sLit "list comprehension") +matchContextErrString (StmtCtxt MonadComp) = ptext (sLit "monad comprehension") matchContextErrString (StmtCtxt PArrComp) = ptext (sLit "array comprehension") \end{code} @@ -1244,7 +1381,7 @@ pprStmtInCtxt ctxt stmt = hang (ptext (sLit "In a stmt of") <+> pprStmtContext c 4 (ppr_stmt stmt) where -- For Group and Transform Stmts, don't print the nested stmts! - ppr_stmt (GroupStmt _ _ by using) = pprGroupStmt by using - ppr_stmt (TransformStmt _ _ using by) = pprTransformStmt using by - ppr_stmt stmt = pprStmt stmt + ppr_stmt (GroupStmt _ _ by using _ _ _) = pprGroupStmt by using + ppr_stmt (TransformStmt _ bndrs using by _ _) = pprTransformStmt bndrs using by + ppr_stmt stmt = pprStmt stmt \end{code}