% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
-
-HsExpr: Abstract Haskell syntax: expressions
-
\begin{code}
+{-# LANGUAGE DeriveDataTypeable #-}
+
+-- | Abstract Haskell syntax for expressions.
module HsExpr where
#include "HsVersions.h"
import HsPat
import HsLit
import HsTypes
-import HsImpExp
import HsBinds
-- others:
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)
+--
+-- * Before the renamer, this list is 'noSyntaxTable'
--
--- * After the renamer, it takes the form [(std_name, HsVar actual_name)]
+-- * After the renamer, it takes the form @[(std_name, HsVar actual_name)]@
-- For example, for the 'return' op of a monad
--- normal case: (GHC.Base.return, HsVar GHC.Base.return)
--- with rebindable syntax: (GHC.Base.return, return_22)
--- where return_22 is whatever "return" is in scope
--
--- * After the type checker, it takes the form [(std_name, <expression>)]
--- where <expression> is the evidence for the method
+-- * normal case: @(GHC.Base.return, HsVar GHC.Base.return)@
+--
+-- * with rebindable syntax: @(GHC.Base.return, return_22)@
+-- where @return_22@ is whatever @return@ is in scope
+--
+-- * After the type checker, it takes the form @[(std_name, <expression>)]@
+-- where @<expression>@ is the evidence for the method
noSyntaxTable :: SyntaxTable id
noSyntaxTable = []
-------------------------
+-- | 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
- | HsLam (MatchGroup id) -- Currently always a single match
+ | HsLit HsLit -- ^ Simple (non-overloaded) literals
- | HsApp (LHsExpr id) -- Application
- (LHsExpr id)
+ | HsLam (MatchGroup id) -- Currently always a single match
+
+ | 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.
-- 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)
+
+ | ELazyPat (LHsExpr id) -- ~ pattern
- | HsType (LHsType id) -- Explicit type argument; e.g f {| Int |} x y
+ | 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)
+
+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
+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
\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
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))
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
+ = (sep [pprHsInfix v, pp_expr])
-ppr_expr (HsCase expr matches)
- = sep [ sep [ptext SLIT("case"), nest 4 (ppr expr), ptext SLIT("of")],
- nest 2 (pprMatches CaseAlt matches) ]
-
-ppr_expr (HsIf e1 e2 e3)
- = sep [hsep [ptext SLIT("if"), nest 2 (ppr e1), ptext SLIT("then")],
- nest 4 (ppr e2),
- ptext SLIT("else"),
- nest 4 (ppr e3)]
+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)))
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 _ _ _)
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 [])) _ _ _)
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.
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.
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
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}
%************************************************************************
-%* *
+%* *
\subsection{@Match@, @GRHSs@, and @GRHS@ datatypes}
-%* *
+%* *
%************************************************************************
@Match@es are sets of pattern bindings and right hand sides for
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)
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 -> MatchGroup id -> SDoc
-pprFunBind fun matches = pprMatches (FunRhs fun) matches
+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)
- = pp_name ctxt <+> sep [sep (map ppr 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
- pp_name (FunRhs fun) = ppr fun -- Not pprBndr; the AbsBinds will
- -- have printed the signature
- pp_name LambdaExpr = char '\\'
- pp_name other = empty
-
+ (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
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 $(f 4)
+ id -- The id is just a unique name to
+ (LHsExpr id) -- identify this splice point
+ deriving (Data, Typeable)
+
instance OutputableBndr id => Outputable (HsSplice id) where
ppr = pprSplice
pprSplice :: OutputableBndr id => HsSplice id -> SDoc
-pprSplice (HsSplice n e) = char '$' <> 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 -- Function binding for f
- | CaseAlt -- Guard on a case alternative
- | LambdaExpr -- Pattern of a lambda
- | ProcExpr -- Pattern of a proc
- | PatBindRhs -- Pattern binding
- | RecUpd -- Record update [used only in DsExpr to tell matchWrapper
- -- what sort of runtime error message to generate]
- | StmtCtxt (HsStmtContext id) -- Pattern of a do-stmt or list comprehension
- deriving ()
+data 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}
projects / ghc-hetmet.git / blobdiff