% % (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 HsBinds ( HsBinds(..), nullBinds ) import HsPat ( Pat ) import HsLit ( HsLit, HsOverLit ) import HsTypes ( HsType, PostTcType, SyntaxName ) import HsImpExp ( isOperator, pprHsVar ) -- others: import ForeignCall ( Safety ) import PprType ( pprParendType ) import Type ( Type, TyThing ) import Var ( TyVar, Id ) import Name ( Name ) import DataCon ( DataCon ) import CStrings ( CLabelString, pprCLabelString ) import BasicTypes ( IPName, Boxity, tupleParens, Fixity(..) ) import SrcLoc ( SrcLoc ) import Outputable import FastString \end{code} %************************************************************************ %* * \subsection{Expressions proper} %* * %************************************************************************ \begin{code} data HsExpr id = HsVar id -- variable | HsIPVar (IPName id) -- implicit parameter | HsOverLit HsOverLit -- Overloaded literals; eliminated by type checker | HsLit HsLit -- Simple (non-overloaded) literals | HsLam (Match id) -- lambda | HsApp (HsExpr id) -- application (HsExpr 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 (HsExpr id) -- left operand (HsExpr id) -- operator Fixity -- Renamer adds fixity; bottom until then (HsExpr id) -- right operand -- We preserve prefix negation and parenthesis for the precedence parser. -- They are eventually removed by the type checker. | NegApp (HsExpr id) -- negated expr SyntaxName -- Name of 'negate' (see RnEnv.lookupSyntaxName) | HsPar (HsExpr id) -- parenthesised expr | SectionL (HsExpr id) -- operand (HsExpr id) -- operator | SectionR (HsExpr id) -- operator (HsExpr id) -- operand | HsCase (HsExpr id) [Match id] SrcLoc | HsIf (HsExpr id) -- predicate (HsExpr id) -- then part (HsExpr id) -- else part SrcLoc | HsLet (HsBinds id) -- let(rec) (HsExpr id) | HsDo (HsStmtContext Name) -- The parameterisation is unimportant -- because in this context we never use -- the PatGuard or ParStmt variant [Stmt id] -- "do":one or more stmts [id] -- Ids for [return,fail,>>=,>>] -- Brutal but simple -- Before type checking, used for rebindable syntax PostTcType -- Type of the whole expression SrcLoc | ExplicitList -- syntactic list PostTcType -- Gives type of components of list [HsExpr id] | ExplicitPArr -- syntactic parallel array: [:e1, ..., en:] PostTcType -- type of elements of the parallel array [HsExpr id] | ExplicitTuple -- tuple [HsExpr id] -- NB: Unit is ExplicitTuple [] -- for tuples, we can get the types -- direct from the components Boxity -- Record construction | RecordCon id -- The constructor (HsRecordBinds id) | RecordConOut DataCon (HsExpr id) -- Data con Id applied to type args (HsRecordBinds id) -- Record update | RecordUpd (HsExpr id) (HsRecordBinds id) | RecordUpdOut (HsExpr id) -- TRANSLATION Type -- Type of *input* record Type -- Type of *result* record (may differ from -- type of input record) (HsRecordBinds id) | ExprWithTySig -- signature binding (HsExpr id) (HsType id) | ArithSeqIn -- arithmetic sequence (ArithSeqInfo id) | ArithSeqOut (HsExpr id) -- (typechecked, of course) (ArithSeqInfo id) | PArrSeqIn -- arith. sequence for parallel array (ArithSeqInfo id) -- [:e1..e2:] or [:e1, e2..e3:] | PArrSeqOut (HsExpr id) -- (typechecked, of course) (ArithSeqInfo id) | HsCCall CLabelString -- call into the C world; string is [HsExpr id] -- the C function; exprs are the -- arguments to pass. Safety -- True <=> might cause Haskell -- garbage-collection (must generate -- more paranoid code) Bool -- True <=> it's really a "casm" -- NOTE: this CCall is the *boxed* -- version; the desugarer will convert -- it into the unboxed "ccall#". PostTcType -- The result type; will be *bottom* -- until the typechecker gets ahold of it | HsSCC FastString -- "set cost centre" (_scc_) annotation (HsExpr id) -- expr whose cost is to be measured -- MetaHaskell Extensions | HsBracket (HsBracket id) SrcLoc | 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 | HsSplice id (HsExpr id) SrcLoc -- $z or $(f 4) -- The id is just a unique name to -- identify this splice point | HsReify (HsReify id) -- reifyType t, reifyDecl i, reifyFixity \end{code} These constructors only appear temporarily in the parser. The renamer translates them into the Right Thing. \begin{code} | EWildPat -- wildcard | EAsPat id -- as pattern (HsExpr id) | ELazyPat (HsExpr id) -- ~ pattern | HsType (HsType 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] (HsExpr id) | TyApp -- TRANSLATION (HsExpr id) -- generated by Spec [Type] -- DictLam and DictApp are "inverses" | DictLam [id] (HsExpr id) | DictApp (HsExpr id) [id] type PendingSplice = (Name, HsExpr 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 b = pprDeeper (ppr b) 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 (HsLam match) = pprMatch LambdaExpr match ppr_expr expr@(HsApp e1 e2) = let (fun, args) = collect_args expr [] in (ppr_expr fun) <+> (sep (map ppr_expr args)) where collect_args (HsApp fun arg) args = collect_args fun (arg:args) collect_args fun args = (fun, args) ppr_expr (OpApp e1 op fixity e2) = case 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 (pprExpr op) 4 (sep [pp_e1, pp_e2]) pp_infixly v = sep [pp_e1, hsep [pp_v_op, pp_e2]] where ppr_v = ppr v pp_v_op | isOperator ppr_v = ppr_v | otherwise = char '`' <> ppr_v <> char '`' -- Put it in backquotes if it's not an operator already ppr_expr (NegApp e _) = char '-' <+> pprParendExpr e ppr_expr (HsPar e) = parens (ppr_expr e) ppr_expr (SectionL expr op) = case 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, ppr v]) ppr_expr (SectionR op expr) = case 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 [ppr v, pp_expr]) ppr_expr (HsCase expr matches _) = sep [ sep [ptext SLIT("case"), nest 4 (pprExpr expr), ptext SLIT("of")], nest 2 (pprMatches CaseAlt matches) ] ppr_expr (HsIf e1 e2 e3 _) = sep [hsep [ptext SLIT("if"), nest 2 (pprExpr e1), ptext SLIT("then")], nest 4 (pprExpr e2), ptext SLIT("else"), nest 4 (pprExpr e3)] -- special case: let ... in let ... ppr_expr (HsLet binds expr@(HsLet _ _)) = sep [hang (ptext SLIT("let")) 2 (hsep [pprBinds binds, ptext SLIT("in")]), pprExpr 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 _ _ _) = pprDo do_or_list_comp stmts ppr_expr (ExplicitList _ exprs) = brackets (fsep (punctuate comma (map ppr_expr exprs))) ppr_expr (ExplicitPArr _ exprs) = pa_brackets (fsep (punctuate comma (map ppr_expr exprs))) ppr_expr (ExplicitTuple exprs boxity) = tupleParens boxity (sep (punctuate comma (map ppr_expr exprs))) ppr_expr (RecordCon con_id rbinds) = pp_rbinds (ppr con_id) rbinds ppr_expr (RecordConOut data_con con rbinds) = pp_rbinds (ppr con) rbinds ppr_expr (RecordUpd aexp rbinds) = pp_rbinds (pprParendExpr aexp) rbinds ppr_expr (RecordUpdOut aexp _ _ rbinds) = pp_rbinds (pprParendExpr aexp) rbinds ppr_expr (ExprWithTySig expr sig) = hang (nest 2 (ppr_expr expr) <+> dcolon) 4 (ppr sig) ppr_expr (ArithSeqIn info) = brackets (ppr info) ppr_expr (ArithSeqOut expr info) = brackets (ppr info) ppr_expr (PArrSeqIn info) = pa_brackets (ppr info) ppr_expr (PArrSeqOut 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 (HsCCall fun args _ is_asm result_ty) = hang (if is_asm then ptext SLIT("_casm_ ``") <> pprCLabelString fun <> ptext SLIT("''") else ptext SLIT("_ccall_") <+> pprCLabelString fun) 4 (sep (map pprParendExpr args)) 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_expr expr) ppr_expr (TyApp expr [ty]) = hang (ppr_expr expr) 4 (pprParendType ty) ppr_expr (TyApp expr tys) = hang (ppr_expr 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_expr expr) ppr_expr (DictApp expr [dname]) = hang (ppr_expr expr) 4 (ppr dname) ppr_expr (DictApp expr dnames) = hang (ppr_expr expr) 4 (brackets (interpp'SP dnames)) ppr_expr (HsType id) = ppr id ppr_expr (HsSplice n e _) = char '$' <> brackets (ppr n) <> pprParendExpr e ppr_expr (HsBracket b _) = pprHsBracket b ppr_expr (HsBracketOut e ps) = ppr e $$ ptext SLIT("where") <+> ppr ps ppr_expr (HsReify r) = ppr r -- 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 => HsExpr id -> SDoc pprParendExpr expr = let pp_as_was = pprExpr expr in case 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 _ -> parens pp_as_was \end{code} %************************************************************************ %* * \subsection{Record binds} %* * %************************************************************************ \begin{code} type HsRecordBinds id = [(id, HsExpr id)] recBindFields :: HsRecordBinds id -> [id] recBindFields rbinds = [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 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 Match id = Match [Pat id] -- The patterns (Maybe (HsType id)) -- A type signature for the result of the match -- Nothing after typechecking (GRHSs id) -- GRHSs are used both for pattern bindings and for Matches data GRHSs id = GRHSs [GRHS id] -- Guarded RHSs (HsBinds id) -- The where clause PostTcType -- Type of RHS (after type checking) data GRHS id = GRHS [Stmt id] -- The RHS is the final ResultStmt SrcLoc mkSimpleMatch :: [Pat id] -> HsExpr id -> Type -> SrcLoc -> Match id mkSimpleMatch pats rhs rhs_ty locn = Match pats Nothing (GRHSs (unguardedRHS rhs locn) EmptyBinds rhs_ty) unguardedRHS :: HsExpr id -> SrcLoc -> [GRHS id] unguardedRHS rhs loc = [GRHS [ResultStmt rhs loc] loc] \end{code} @getMatchLoc@ takes a @Match@ and returns the source-location gotten from the GRHS inside. THis is something of a nuisance, but no more. \begin{code} getMatchLoc :: Match id -> SrcLoc getMatchLoc (Match _ _ (GRHSs (GRHS _ loc : _) _ _)) = loc \end{code} We know the list must have at least one @Match@ in it. \begin{code} pprMatches :: (OutputableBndr id) => HsMatchContext id -> [Match id] -> SDoc pprMatches ctxt matches = vcat (map (pprMatch ctxt) matches) -- Exported to HsBinds, which can't see the defn of HsMatchContext pprFunBind :: (OutputableBndr id) => id -> [Match id] -> SDoc pprFunBind fun matches = pprMatches (FunRhs fun) matches -- Exported to HsBinds, which can't see the defn of HsMatchContext pprPatBind :: (OutputableBndr id) => Pat id -> 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 ty) = vcat (map (pprGRHS ctxt) grhss) $$ (if nullBinds binds then empty else text "where" $$ nest 4 (pprDeeper (ppr binds))) pprGRHS :: OutputableBndr id => HsMatchContext id -> GRHS id -> SDoc pprGRHS ctxt (GRHS [ResultStmt expr _] locn) = pp_rhs ctxt expr pprGRHS ctxt (GRHS guarded locn) = sep [char '|' <+> interpp'SP guards, pp_rhs ctxt expr] where ResultStmt expr _ = last guarded -- Last stmt should be a ResultStmt for guards guards = init guarded pp_rhs ctxt rhs = matchSeparator ctxt <+> pprDeeper (ppr rhs) \end{code} %************************************************************************ %* * \subsection{Do stmts and list comprehensions} %* * %************************************************************************ \begin{code} data Stmt id = BindStmt (Pat id) (HsExpr id) SrcLoc | LetStmt (HsBinds id) | ResultStmt (HsExpr id) SrcLoc -- See notes that follow | ExprStmt (HsExpr id) PostTcType SrcLoc -- See notes that follow -- The type is the *element type* of the expression -- ParStmts only occur in a list comprehension | ParStmt [[Stmt id]] -- List comp only: parallel set of quals | ParStmtOut [([id], [Stmt id])] -- PLC after renaming; the ids are the binders -- bound by the stmts -- mdo-notation (only exists after renamer) -- The ids are a subset of the variables bound by the stmts that -- either (a) are used before they are bound in the stmts -- or (b) are used in stmts that follow the RecStmt | RecStmt [id] [Stmt id] [HsExpr id] -- Post type-checking only; these expressions correspond -- 1-to-1 with the [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. \end{code} ExprStmts and ResultStmts 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 >> ... * ResultStmt E: do { ....; E } E :: m res_ty Translation: E A list comprehensions of type [elt_ty] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ * ExprStmt E Bool: [ .. | .... E ] [ .. | ..., E, ... ] [ .. | .... | ..., E | ... ] E :: Bool Translation: if E then fail else ... * ResultStmt E: [ E | ... ] E :: elt_ty Translation: return E 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 ... * ResultStmt E: f x | ...guards... = E E :: rhs_ty Translation: E Array comprehensions are handled like list comprehensions -=chak \begin{code} consLetStmt :: HsBinds id -> [Stmt id] -> [Stmt id] consLetStmt EmptyBinds stmts = stmts consLetStmt binds stmts = LetStmt binds : stmts \end{code} \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 (ResultStmt expr _) = ppr expr pprStmt (ParStmt stmtss) = hsep (map (\stmts -> ptext SLIT("| ") <> ppr stmts) stmtss) pprStmt (ParStmtOut stmtss) = hsep (map (\stmts -> ptext SLIT("| ") <> ppr stmts) stmtss) pprStmt (RecStmt _ segment _) = vcat (map ppr segment) pprDo :: OutputableBndr id => HsStmtContext any -> [Stmt id] -> SDoc pprDo DoExpr stmts = hang (ptext SLIT("do")) 2 (vcat (map ppr stmts)) pprDo MDoExpr stmts = hang (ptext SLIT("mdo")) 3 (vcat (map ppr stmts)) pprDo ListComp stmts = pprComp brackets stmts pprDo PArrComp stmts = pprComp pa_brackets stmts pprComp :: OutputableBndr id => (SDoc -> SDoc) -> [Stmt id] -> SDoc pprComp brack stmts = brack $ hang (pprExpr expr <+> char '|') 4 (interpp'SP quals) where ResultStmt expr _ = last stmts -- Last stmt should quals = init stmts -- be an ResultStmt \end{code} %************************************************************************ %* * Template Haskell quotation brackets %* * %************************************************************************ \begin{code} data HsBracket id = ExpBr (HsExpr id) | PatBr (Pat id) | DecBr (HsGroup id) | TypBr (HsType id) 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) thBrackets pp_kind pp_body = char '[' <> pp_kind <> char '|' <+> pp_body <+> ptext SLIT("|]") data HsReify id = Reify ReifyFlavour id -- Pre typechecking | ReifyOut ReifyFlavour Name -- Post typechecking -- The Name could be the name of -- an Id, TyCon, or Class data ReifyFlavour = ReifyDecl | ReifyType | ReifyFixity instance Outputable id => Outputable (HsReify id) where ppr (Reify flavour id) = ppr flavour <+> ppr id ppr (ReifyOut flavour thing) = ppr flavour <+> ppr thing instance Outputable ReifyFlavour where ppr ReifyDecl = ptext SLIT("reifyDecl") ppr ReifyType = ptext SLIT("reifyType") ppr ReifyFixity = ptext SLIT("reifyFixity") \end{code} %************************************************************************ %* * \subsection{Enumerations and list comprehensions} %* * %************************************************************************ \begin{code} data ArithSeqInfo id = From (HsExpr id) | FromThen (HsExpr id) (HsExpr id) | FromTo (HsExpr id) (HsExpr id) | FromThenTo (HsExpr id) (HsExpr id) (HsExpr 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 | 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 -- Recursive do-expression | 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 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 (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 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 (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}