%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1994
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[HsExpr]{Abstract Haskell syntax: expressions}
#include "HsVersions.h"
-- friends:
-import {-# SOURCE #-} HsMatches ( pprMatches, pprMatch, Match )
-
-import HsBinds ( HsBinds )
-import HsBasic ( HsLit )
-import BasicTypes ( Fixity(..), FixityDirection(..) )
+import HsBinds ( HsBinds(..), nullBinds )
+import HsLit ( HsLit, HsOverLit )
+import BasicTypes ( Fixity(..) )
import HsTypes ( HsType )
+import HsImpExp ( isOperator )
-- others:
-import Name ( NamedThing )
-import Id ( Id )
+import Name ( Name )
import Outputable
-import PprType ( pprGenType, pprParendGenType, GenType, GenTyVar )
+import PprType ( pprParendType )
+import Type ( Type )
+import Var ( TyVar )
+import DataCon ( DataCon )
+import CStrings ( CLabelString, pprCLabelString )
+import BasicTypes ( Boxity, tupleParens )
import SrcLoc ( SrcLoc )
\end{code}
%************************************************************************
\begin{code}
-data HsExpr flexi id pat
- = HsVar id -- variable
- | HsLit HsLit -- literal
- | HsLitOut HsLit -- TRANSLATION
- (GenType flexi) -- (with its type)
+data HsExpr id pat
+ = HsVar id -- variable
+ | HsIPVar id -- implicit parameter
+ | HsOverLit HsOverLit -- Overloaded literals; eliminated by type checker
+ | HsLit HsLit -- Simple (non-overloaded) literals
- | HsLam (Match flexi id pat) -- lambda
- | HsApp (HsExpr flexi id pat) -- application
- (HsExpr flexi id pat)
+ | HsLam (Match id pat) -- lambda
+ | HsApp (HsExpr id pat) -- application
+ (HsExpr id pat)
-- 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 flexi id pat) -- left operand
- (HsExpr flexi id pat) -- operator
+ | OpApp (HsExpr id pat) -- left operand
+ (HsExpr id pat) -- operator
Fixity -- Renamer adds fixity; bottom until then
- (HsExpr flexi id pat) -- right operand
+ (HsExpr id pat) -- right operand
-- We preserve prefix negation and parenthesis for the precedence parser.
-- They are eventually removed by the type checker.
- | NegApp (HsExpr flexi id pat) -- negated expr
- (HsExpr flexi id pat) -- the negate id (in a HsVar)
+ | NegApp (HsExpr id pat) -- negated expr
- | HsPar (HsExpr flexi id pat) -- parenthesised expr
+ | HsPar (HsExpr id pat) -- parenthesised expr
- | SectionL (HsExpr flexi id pat) -- operand
- (HsExpr flexi id pat) -- operator
- | SectionR (HsExpr flexi id pat) -- operator
- (HsExpr flexi id pat) -- operand
+ | SectionL (HsExpr id pat) -- operand
+ (HsExpr id pat) -- operator
+ | SectionR (HsExpr id pat) -- operator
+ (HsExpr id pat) -- operand
- | HsCase (HsExpr flexi id pat)
- [Match flexi id pat] -- must have at least one Match
+ | HsCase (HsExpr id pat)
+ [Match id pat]
SrcLoc
- | HsIf (HsExpr flexi id pat) -- predicate
- (HsExpr flexi id pat) -- then part
- (HsExpr flexi id pat) -- else part
+ | HsIf (HsExpr id pat) -- predicate
+ (HsExpr id pat) -- then part
+ (HsExpr id pat) -- else part
SrcLoc
- | HsLet (HsBinds flexi id pat) -- let(rec)
- (HsExpr flexi id pat)
+ | HsLet (HsBinds id pat) -- let(rec)
+ (HsExpr id pat)
+
+ | HsWith (HsExpr id pat) -- implicit parameter binding
+ [(id, HsExpr id pat)]
- | HsDo DoOrListComp
- [Stmt flexi id pat] -- "do":one or more stmts
+ | HsDo HsMatchContext
+ [Stmt id pat] -- "do":one or more stmts
SrcLoc
- | HsDoOut DoOrListComp
- [Stmt flexi id pat] -- "do":one or more stmts
- id -- id for return
- id -- id for >>=
- id -- id for zero
- (GenType flexi) -- Type of the whole expression
+ | HsDoOut HsMatchContext
+ [Stmt id pat] -- "do":one or more stmts
+ id -- id for return
+ id -- id for >>=
+ id -- id for fail
+ Type -- Type of the whole expression
SrcLoc
| ExplicitList -- syntactic list
- [HsExpr flexi id pat]
+ [HsExpr id pat]
| ExplicitListOut -- TRANSLATION
- (GenType flexi) -- Gives type of components of list
- [HsExpr flexi id pat]
+ Type -- Gives type of components of list
+ [HsExpr id pat]
| ExplicitTuple -- tuple
- [HsExpr flexi id pat]
+ [HsExpr id pat]
-- NB: Unit is ExplicitTuple []
-- for tuples, we can get the types
-- direct from the components
+ Boxity
- | HsCon Id -- TRANSLATION; a saturated constructor application
- [GenType flexi]
- [HsExpr flexi id pat]
-- Record construction
| RecordCon id -- The constructor
- (HsExpr flexi id pat) -- Always (HsVar id) until type checker,
- -- but the latter adds its type args too
- (HsRecordBinds flexi id pat)
+ (HsRecordBinds id pat)
+
+ | RecordConOut DataCon
+ (HsExpr id pat) -- Data con Id applied to type args
+ (HsRecordBinds id pat)
+
-- Record update
- | RecordUpd (HsExpr flexi id pat)
- (HsRecordBinds flexi id pat)
+ | RecordUpd (HsExpr id pat)
+ (HsRecordBinds id pat)
- | RecordUpdOut (HsExpr flexi id pat) -- TRANSLATION
- (GenType flexi) -- Type of *result* record (may differ from
+ | RecordUpdOut (HsExpr id pat) -- TRANSLATION
+ Type -- Type of *result* record (may differ from
-- type of input record)
- [id] -- Dicts needed for construction
- (HsRecordBinds flexi id pat)
+ [id] -- Dicts needed for construction
+ (HsRecordBinds id pat)
- | ExprWithTySig -- signature binding
- (HsExpr flexi id pat)
+ | ExprWithTySig -- signature binding
+ (HsExpr id pat)
(HsType id)
- | ArithSeqIn -- arithmetic sequence
- (ArithSeqInfo flexi id pat)
+ | ArithSeqIn -- arithmetic sequence
+ (ArithSeqInfo id pat)
| ArithSeqOut
- (HsExpr flexi id pat) -- (typechecked, of course)
- (ArithSeqInfo flexi id pat)
+ (HsExpr id pat) -- (typechecked, of course)
+ (ArithSeqInfo id pat)
- | CCall FAST_STRING -- call into the C world; string is
- [HsExpr flexi id pat] -- the C function; exprs are the
+ | HsCCall CLabelString -- call into the C world; string is
+ [HsExpr id pat] -- the C function; exprs are the
-- arguments to pass.
Bool -- True <=> might cause Haskell
-- garbage-collection (must generate
-- NOTE: this CCall is the *boxed*
-- version; the desugarer will convert
-- it into the unboxed "ccall#".
- (GenType flexi) -- The result type; will be *bottom*
+ Type -- The result type; will be *bottom*
-- until the typechecker gets ahold of it
| HsSCC FAST_STRING -- "set cost centre" (_scc_) annotation
- (HsExpr flexi id pat) -- expr whose cost is to be measured
+ (HsExpr id pat) -- expr whose cost is to be measured
+
+\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 pat)
+
+ | ELazyPat (HsExpr id pat) -- ~ 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
- [GenTyVar flexi]
- (HsExpr flexi id pat)
+ [TyVar]
+ (HsExpr id pat)
| TyApp -- TRANSLATION
- (HsExpr flexi id pat) -- generated by Spec
- [GenType flexi]
+ (HsExpr id pat) -- generated by Spec
+ [Type]
-- DictLam and DictApp are "inverses"
| DictLam
[id]
- (HsExpr flexi id pat)
+ (HsExpr id pat)
| DictApp
- (HsExpr flexi id pat)
+ (HsExpr id pat)
[id]
-type HsRecordBinds flexi id pat
- = [(id, HsExpr flexi id pat, Bool)]
+type HsRecordBinds id pat
+ = [(id, HsExpr id pat, Bool)]
-- True <=> source code used "punning",
-- i.e. {op1, op2} rather than {op1=e1, op2=e2}
\end{code}
\end{verbatim}
\begin{code}
-instance (NamedThing id, Outputable id, Outputable pat) =>
- Outputable (HsExpr flexi id pat) where
+instance (Outputable id, Outputable pat) =>
+ Outputable (HsExpr id pat) where
ppr expr = pprExpr expr
\end{code}
\begin{code}
-pprExpr :: (NamedThing id, Outputable id, Outputable pat)
- => HsExpr flexi id pat -> SDoc
+pprExpr :: (Outputable id, Outputable pat)
+ => HsExpr id pat -> SDoc
pprExpr e = pprDeeper (ppr_expr e)
+pprBinds b = pprDeeper (ppr b)
-ppr_expr (HsVar v) = ppr v
+ppr_expr (HsVar v)
+ -- Put it in parens if it's an operator
+ | isOperator v = parens (ppr v)
+ | otherwise = ppr v
-ppr_expr (HsLit lit) = ppr lit
-ppr_expr (HsLitOut lit _) = ppr lit
+ppr_expr (HsIPVar v) = {- char '?' <> -} ppr v
+ppr_expr (HsLit lit) = ppr lit
+ppr_expr (HsOverLit lit) = ppr lit
ppr_expr (HsLam match)
- = hsep [char '\\', nest 2 (pprMatch True match)]
+ = hsep [char '\\', nest 2 (pprMatch (True,empty) match)]
ppr_expr expr@(HsApp e1 e2)
= let (fun, args) = collect_args expr [] in
- (pprExpr fun) <+> (sep (map pprExpr args))
+ (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)
= hang (pprExpr op) 4 (sep [pp_e1, pp_e2])
pp_infixly v
- = sep [pp_e1, hsep [ppr v, pp_e2]]
+ = sep [pp_e1, hsep [pp_v_op, pp_e2]]
+ where
+ pp_v_op | isOperator 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 (NegApp e) = char '-' <+> pprParendExpr e
-ppr_expr (HsPar e)
- = parens (ppr_expr e)
+ppr_expr (HsPar e) = parens (ppr_expr e)
ppr_expr (SectionL expr op)
= case op of
= parens (sep [ppr v, pp_expr])
ppr_expr (HsCase expr matches _)
- = sep [ sep [ptext SLIT("case"), nest 4 (ppr_expr expr), ptext SLIT("of")],
+ = sep [ sep [ptext SLIT("case"), nest 4 (pprExpr expr), ptext SLIT("of")],
nest 2 (pprMatches (True, empty) matches) ]
ppr_expr (HsIf e1 e2 e3 _)
- = sep [hsep [ptext SLIT("if"), nest 2 (ppr_expr e1), ptext SLIT("then")],
- nest 4 (ppr_expr e2),
+ = sep [hsep [ptext SLIT("if"), nest 2 (pprExpr e1), ptext SLIT("then")],
+ nest 4 (pprExpr e2),
ptext SLIT("else"),
- nest 4 (ppr_expr e3)]
+ nest 4 (pprExpr e3)]
-- special case: let ... in let ...
ppr_expr (HsLet binds expr@(HsLet _ _))
- = sep [hang (ptext SLIT("let")) 2 (hsep [ppr binds, ptext SLIT("in")]),
- ppr_expr expr]
+ = 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 (ppr binds),
+ = sep [hang (ptext SLIT("let")) 2 (pprBinds binds),
hang (ptext SLIT("in")) 2 (ppr expr)]
+ppr_expr (HsWith expr binds)
+ = hsep [ppr expr, ptext SLIT("with"), ppr binds]
+
ppr_expr (HsDo do_or_list_comp stmts _) = pprDo do_or_list_comp stmts
ppr_expr (HsDoOut do_or_list_comp stmts _ _ _ _ _) = pprDo do_or_list_comp stmts
ppr_expr (ExplicitList exprs)
- = brackets (fsep (punctuate comma (map pprExpr exprs)))
+ = brackets (fsep (punctuate comma (map ppr_expr exprs)))
ppr_expr (ExplicitListOut ty exprs)
- = hcat [ brackets (fsep (punctuate comma (map pprExpr exprs))),
- ifNotPprForUser ((<>) space (parens (pprGenType ty))) ]
+ = brackets (fsep (punctuate comma (map ppr_expr exprs)))
-ppr_expr (ExplicitTuple exprs)
- = parens (sep (punctuate comma (map pprExpr exprs)))
+ppr_expr (ExplicitTuple exprs boxity)
+ = tupleParens boxity (sep (punctuate comma (map ppr_expr exprs)))
-ppr_expr (HsCon con_id tys args)
- = ppr con_id <+> sep (map pprParendGenType tys ++
- map pprParendExpr args)
-
-ppr_expr (RecordCon con_id con rbinds)
+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 (ExprWithTySig expr sig)
- = hang (nest 2 (pprExpr expr) <+> ptext SLIT("::"))
+ = hang (nest 2 (ppr_expr expr) <+> dcolon)
4 (ppr sig)
ppr_expr (ArithSeqIn info)
ppr_expr (ArithSeqOut expr info)
= brackets (ppr info)
-ppr_expr (CCall fun args _ is_asm result_ty)
+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_ ``") <> ptext fun <> ptext SLIT("''")
- else ptext SLIT("_ccall_") <+> ptext fun)
+ then ptext SLIT("_casm_ ``") <> pprCLabelString fun <> ptext SLIT("''")
+ else ptext SLIT("_ccall_") <+> pprCLabelString fun)
4 (sep (map pprParendExpr args))
-ppr_expr (HsSCC label expr)
- = sep [ ptext SLIT("_scc_") <+> doubleQuotes (ptext label), pprParendExpr expr ]
+ppr_expr (HsSCC lbl expr)
+ = sep [ ptext SLIT("_scc_") <+> doubleQuotes (ptext lbl), pprParendExpr expr ]
ppr_expr (TyLam tyvars expr)
= hang (hsep [ptext SLIT("/\\"), interppSP tyvars, ptext SLIT("->")])
- 4 (pprExpr expr)
+ 4 (ppr_expr expr)
ppr_expr (TyApp expr [ty])
- = hang (pprExpr expr) 4 (pprParendGenType ty)
+ = hang (ppr_expr expr) 4 (pprParendType ty)
ppr_expr (TyApp expr tys)
- = hang (pprExpr expr)
+ = hang (ppr_expr expr)
4 (brackets (interpp'SP tys))
ppr_expr (DictLam dictvars expr)
= hang (hsep [ptext SLIT("\\{-dict-}"), interppSP dictvars, ptext SLIT("->")])
- 4 (pprExpr expr)
+ 4 (ppr_expr expr)
ppr_expr (DictApp expr [dname])
- = hang (pprExpr expr) 4 (ppr dname)
+ = hang (ppr_expr expr) 4 (ppr dname)
ppr_expr (DictApp expr dnames)
- = hang (pprExpr expr)
+ = hang (ppr_expr expr)
4 (brackets (interpp'SP dnames))
+ppr_expr (HsType id) = ppr id
+
\end{code}
Parenthesize unless very simple:
\begin{code}
-pprParendExpr :: (NamedThing id, Outputable id, Outputable pat)
- => HsExpr flexi id pat -> SDoc
+pprParendExpr :: (Outputable id, Outputable pat)
+ => HsExpr id pat -> SDoc
pprParendExpr expr
= let
in
case expr of
HsLit l -> ppr l
- HsLitOut l _ -> ppr l
+ HsOverLit l -> ppr l
HsVar _ -> pp_as_was
+ HsIPVar _ -> pp_as_was
ExplicitList _ -> pp_as_was
ExplicitListOut _ _ -> pp_as_was
- ExplicitTuple _ -> pp_as_was
+ ExplicitTuple _ _ -> pp_as_was
HsPar _ -> pp_as_was
_ -> parens pp_as_was
%************************************************************************
\begin{code}
-pp_rbinds :: (NamedThing id, Outputable id, Outputable pat)
+pp_rbinds :: (Outputable id, Outputable pat)
=> SDoc
- -> HsRecordBinds flexi id pat -> SDoc
+ -> HsRecordBinds id pat -> SDoc
pp_rbinds thing rbinds
= hang thing
- 4 (braces (hsep (punctuate comma (map (pp_rbind) rbinds))))
+ 4 (braces (sep (punctuate comma (map (pp_rbind) rbinds))))
where
pp_rbind (v, e, pun_flag)
= getPprStyle $ \ sty ->
hsep [ppr v, char '=', ppr e]
\end{code}
+
+
%************************************************************************
%* *
-\subsection{Do stmts and list comprehensions}
+\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 DoOrListComp = DoStmt | ListComp | Guard
-
-pprDo DoStmt stmts
- = hang (ptext SLIT("do")) 2 (vcat (map ppr stmts))
-pprDo ListComp stmts
- = brackets $
- hang (pprExpr expr <+> char '|')
- 4 (interpp'SP quals)
- where
- ReturnStmt expr = last stmts -- Last stmt should be a ReturnStmt for list comps
- quals = init stmts
+data Match id pat
+ = Match
+ [id] -- Tyvars wrt which this match is universally quantified
+ -- empty after typechecking
+ [pat] -- The patterns
+ (Maybe (HsType id)) -- A type signature for the result of the match
+ -- Nothing after typechecking
+
+ (GRHSs id pat)
+
+-- GRHSs are used both for pattern bindings and for Matches
+data GRHSs id pat
+ = GRHSs [GRHS id pat] -- Guarded RHSs
+ (HsBinds id pat) -- The where clause
+ (Maybe Type) -- Just rhs_ty after type checking
+
+data GRHS id pat
+ = GRHS [Stmt id pat] -- The RHS is the final ExprStmt
+ -- I considered using a RetunStmt, but
+ -- it printed 'wrong' in error messages
+ SrcLoc
+
+mkSimpleMatch :: [pat] -> HsExpr id pat -> Maybe Type -> SrcLoc -> Match id pat
+mkSimpleMatch pats rhs maybe_rhs_ty locn
+ = Match [] pats Nothing (GRHSs (unguardedRHS rhs locn) EmptyBinds maybe_rhs_ty)
+
+unguardedRHS :: HsExpr id pat -> SrcLoc -> [GRHS id pat]
+unguardedRHS rhs loc = [GRHS [ExprStmt 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}
-data Stmt flexi id pat
- = BindStmt pat
- (HsExpr flexi id pat)
- SrcLoc
+getMatchLoc :: Match id pat -> SrcLoc
+getMatchLoc (Match _ _ _ (GRHSs (GRHS _ loc : _) _ _)) = loc
+\end{code}
- | LetStmt (HsBinds flexi id pat)
+We know the list must have at least one @Match@ in it.
- | GuardStmt (HsExpr flexi id pat) -- List comps only
- SrcLoc
+\begin{code}
+pprMatches :: (Outputable id, Outputable pat)
+ => (Bool, SDoc) -> [Match id pat] -> SDoc
+pprMatches print_info matches = vcat (map (pprMatch print_info) matches)
+
+
+pprMatch :: (Outputable id, Outputable pat)
+ => (Bool, SDoc) -> Match id pat -> SDoc
+pprMatch print_info@(is_case, name) (Match _ pats maybe_ty grhss)
+ = maybe_name <+> sep [sep (map ppr pats),
+ ppr_maybe_ty,
+ nest 2 (pprGRHSs is_case grhss)]
+ where
+ maybe_name | is_case = empty
+ | otherwise = name
+ ppr_maybe_ty = case maybe_ty of
+ Just ty -> dcolon <+> ppr ty
+ Nothing -> empty
+
+
+pprGRHSs :: (Outputable id, Outputable pat)
+ => Bool -> GRHSs id pat -> SDoc
+pprGRHSs is_case (GRHSs grhss binds maybe_ty)
+ = vcat (map (pprGRHS is_case) grhss)
+ $$
+ (if nullBinds binds then empty
+ else text "where" $$ nest 4 (pprDeeper (ppr binds)))
+
+
+pprGRHS :: (Outputable id, Outputable pat)
+ => Bool -> GRHS id pat -> SDoc
+
+pprGRHS is_case (GRHS [ExprStmt expr _] locn)
+ = text (if is_case then "->" else "=") <+> pprDeeper (ppr expr)
+
+pprGRHS is_case (GRHS guarded locn)
+ = sep [char '|' <+> interpp'SP guards,
+ text (if is_case then "->" else "=") <+> pprDeeper (ppr expr)
+ ]
+ where
+ ExprStmt expr _ = last guarded -- Last stmt should be a ExprStmt for guards
+ guards = init guarded
+\end{code}
- | ExprStmt (HsExpr flexi id pat) -- Do stmts only
- SrcLoc
- | ReturnStmt (HsExpr flexi id pat) -- List comps only, at the end
+
+%************************************************************************
+%* *
+\subsection{Do stmts and list comprehensions}
+%* *
+%************************************************************************
+
+\begin{code}
+data Stmt id pat
+ = BindStmt pat (HsExpr id pat) SrcLoc
+ | LetStmt (HsBinds id pat)
+ | ExprStmt (HsExpr id pat) SrcLoc -- See notes that follow
+ | ParStmt [[Stmt id pat]] -- List comp only: parallel set of quals
+ | ParStmtOut [([id], [Stmt id pat])] -- PLC after renaming
\end{code}
+ExprStmts are a bit tricky, because what
+they mean depends on the context. Consider
+ ExprStmt E
+in the following contexts:
+
+ A do expression of type (m res_ty)
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ * Non-last stmt in list: do { ....; E; ... }
+ E :: m any_ty
+ Translation: E >> ...
+
+ * Last stmt in list: do { ....; E }
+ E :: m res_ty
+ Translation: E
+
+ A list comprehensions of type [elt_ty]
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ * Non-last stmt in list: [ .. | ..., E, ... ]
+ E :: Bool
+ Translation: if E then fail else ...
+
+ * Last stmt in list: [ E | ... ]
+ E :: elt_ty
+ Translation: return E
+
+ A guard list, guarding a RHS of type rhs_ty
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ * Non-last stmt in list: f x | ..., E, ... = ...rhs...
+ E :: Bool
+ Translation: if E then fail else ...
+
+ * Last stmt in list: f x | ...guards... = E
+ E :: rhs_ty
+ Translation: E
+
\begin{code}
-instance (NamedThing id, Outputable id, Outputable pat) =>
- Outputable (Stmt flexi id pat) where
+consLetStmt :: HsBinds id pat -> [Stmt id pat] -> [Stmt id pat]
+consLetStmt EmptyBinds stmts = stmts
+consLetStmt binds stmts = LetStmt binds : stmts
+\end{code}
+
+\begin{code}
+instance (Outputable id, Outputable pat) =>
+ Outputable (Stmt id pat) where
ppr stmt = pprStmt stmt
+pprStmt (ParStmt stmtss)
+ = hsep (map (\stmts -> ptext SLIT("| ") <> ppr stmts) stmtss)
+pprStmt (ParStmtOut stmtss)
+ = hsep (map (\stmts -> ptext SLIT("| ") <> ppr stmts) stmtss)
pprStmt (BindStmt pat expr _)
= hsep [ppr pat, ptext SLIT("<-"), ppr expr]
pprStmt (LetStmt binds)
- = hsep [ptext SLIT("let"), ppr binds]
+ = hsep [ptext SLIT("let"), pprBinds binds]
pprStmt (ExprStmt expr _)
= ppr expr
-pprStmt (GuardStmt expr _)
- = ppr expr
-pprStmt (ReturnStmt expr)
- = hsep [ptext SLIT("return"), ppr expr]
+
+pprDo :: (Outputable id, Outputable pat) => HsMatchContext -> [Stmt id pat] -> SDoc
+pprDo DoExpr stmts = hang (ptext SLIT("do")) 2 (vcat (map ppr stmts))
+pprDo ListComp stmts = brackets $
+ hang (pprExpr expr <+> char '|')
+ 4 (interpp'SP quals)
+ where
+ ExprStmt expr _ = last stmts -- Last stmt should
+ quals = init stmts -- be an ExprStmt
\end{code}
%************************************************************************
%************************************************************************
\begin{code}
-data ArithSeqInfo flexi id pat
- = From (HsExpr flexi id pat)
- | FromThen (HsExpr flexi id pat)
- (HsExpr flexi id pat)
- | FromTo (HsExpr flexi id pat)
- (HsExpr flexi id pat)
- | FromThenTo (HsExpr flexi id pat)
- (HsExpr flexi id pat)
- (HsExpr flexi id pat)
+data ArithSeqInfo id pat
+ = From (HsExpr id pat)
+ | FromThen (HsExpr id pat)
+ (HsExpr id pat)
+ | FromTo (HsExpr id pat)
+ (HsExpr id pat)
+ | FromThenTo (HsExpr id pat)
+ (HsExpr id pat)
+ (HsExpr id pat)
\end{code}
\begin{code}
-instance (NamedThing id, Outputable id, Outputable pat) =>
- Outputable (ArithSeqInfo flexi id pat) where
+instance (Outputable id, Outputable pat) =>
+ Outputable (ArithSeqInfo id pat) 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]
pp_dotdot = ptext SLIT(" .. ")
\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{HsMatchCtxt}
+%* *
+%************************************************************************
+
+\begin{code}
+data HsMatchContext -- Context of a Match or Stmt
+ = ListComp -- List comprehension
+ | DoExpr -- Do Statment
+
+ | FunRhs Name -- Function binding for f
+ | CaseAlt -- Guard on a case alternative
+ | LambdaExpr -- Lambda
+ | PatBindRhs -- Pattern binding
+ | RecUpd -- Record update
+ deriving ()
+
+-- It's convenient to have FunRhs as a Name
+-- throughout so that HsMatchContext doesn't
+-- need to be parameterised.
+-- In the RdrName world we never use the FunRhs variant.
+\end{code}
+
+\begin{code}
+isDoExpr DoExpr = True
+isDoExpr other = False
+
+isDoOrListComp ListComp = True
+isDoOrListComp DoExpr = True
+isDoOrListComp other = False
+\end{code}
+
+\begin{code}
+matchSeparator (FunRhs _) = SLIT("=")
+matchSeparator CaseAlt = SLIT("->")
+matchSeparator LambdaExpr = SLIT("->")
+matchSeparator PatBindRhs = SLIT("=")
+matchSeparator DoExpr = SLIT("<-")
+matchSeparator ListComp = SLIT("<-")
+matchSeparator RecUpd = panic "When is this used?"
+\end{code}
+
+\begin{code}
+pprMatchContext (FunRhs fun) = ptext SLIT("in the definition of function") <+> quotes (ppr fun)
+pprMatchContext CaseAlt = ptext SLIT("in a group of case alternatives beginning")
+pprMatchContext RecUpd = ptext SLIT("in a record-update construct")
+pprMatchContext PatBindRhs = ptext SLIT("in a pattern binding")
+pprMatchContext LambdaExpr = ptext SLIT("in a lambda abstraction")
+pprMatchContext DoExpr = ptext SLIT("in a `do' expression pattern binding")
+pprMatchContext ListComp = ptext SLIT("in a `list comprension' pattern binding")
+\end{code}
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