% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
-
-HsExpr: Abstract Haskell syntax: expressions
-
\begin{code}
+
+-- | Abstract Haskell syntax for expressions.
module HsExpr where
#include "HsVersions.h"
import HsPat
import HsLit
import HsTypes
-import HsImpExp
import HsBinds
-- others:
%************************************************************************
\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
+-- | We use a PostTcTable where there are a bunch of pieces of evidence, more
+-- than is convenient to keep individually.
type PostTcTable = [(Name, Id)]
noPostTcExpr :: PostTcExpr
noPostTcTable = []
-------------------------
--- SyntaxExpr is like PostTcExpr, but it's filled in a little earlier,
+-- | 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
+--
+-- 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
type SyntaxExpr id = HsExpr id
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
+ = HsVar id -- ^ variable
+ | HsIPVar (IPName id) -- ^ implicit parameter
+ | HsOverLit (HsOverLit id) -- ^ Overloaded literals
- | HsLit HsLit -- Simple (non-overloaded) literals
+ | HsLit HsLit -- ^ Simple (non-overloaded) literals
| HsLam (MatchGroup id) -- Currently always a single match
| SectionR (LHsExpr id) -- operator
(LHsExpr id) -- operand
+ | ExplicitTuple -- Used for explicit tuples and sections thereof
+ [HsTupArg id]
+ Boxity
+
| HsCase (LHsExpr id)
(MatchGroup id)
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
-- 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
+ -- _non-empty_ list of DataCons that have
-- all the upd'd fields
[PostTcType] -- Argument types of *input* record type
[PostTcType] -- and *output* record type
| HsBracketOut (HsBracket Name) -- Output of the type checker is
-- the *original*
[PendingSplice] -- renamed expression, plus
- -- *typechecked* splices to be
+ -- _typechecked_ splices to be
-- pasted back in by the desugarer
| HsSpliceE (HsSplice id)
| HsWrap HsWrapper -- TRANSLATION
(HsExpr id)
+-- 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
+
+tupArgPresent :: HsTupArg id -> Bool
+tupArgPresent (Present {}) = True
+tupArgPresent (Missing {}) = False
+
type PendingSplice = (Name, LHsExpr Id) -- Typechecked splices, waiting to be
-- pasted back in by the desugarer
\end{code}
= 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
pp_prefixly = hang (hsep [text " \\ x_ ->", ppr op])
4 (hsep [pp_expr, ptext (sLit "x_ )")])
- pp_infixly v = (sep [pp_expr, pprInfix v])
+ pp_infixly v = (sep [pp_expr, pprHsInfix v])
ppr_expr (SectionR op expr)
= case unLoc op of
pp_prefixly = hang (hsep [text "( \\ x_ ->", ppr op, ptext (sLit "x_")])
4 ((<>) pp_expr rparen)
pp_infixly v
- = (sep [pprInfix v, pp_expr])
+ = (sep [pprHsInfix v, pp_expr])
+
+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)
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) ]
+ = 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)
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 _ rbinds)
= hang (ppr con_id) 2 (ppr rbinds)
= 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<"),
+ = 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<"),
+ = pprTicks (ppr exp) $
+ hcat [ptext (sLit "tickpragma<"),
ppr externalSrcLoc,
ptext (sLit ">("),
ppr exp,
= 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 "|)"))
instance OutputableBndr id => Outputable (HsCmdTop id) where
ppr = pprCmdArg
--- 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
-
-- add parallel array brackets around a document
--
pa_brackets :: SDoc -> SDoc
-- I think that is usually (always?) right
in
case unLoc expr of
- HsLit _ -> pp_as_was
- HsOverLit _ -> 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
+ 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
-- Nothing after typechecking
(GRHSs id)
+isEmptyMatchGroup :: MatchGroup id -> Bool
+isEmptyMatchGroup (MatchGroup ms _) = null ms
+
matchGroupArity :: MatchGroup id -> Arity
matchGroupArity (MatchGroup [] _)
- = panic "matchGroupArity" -- MatchGroup is never empty
+ = 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
hsLMatchPats :: LMatch id -> [LPat id]
hsLMatchPats (L _ (Match pats _ _)) = pats
--- GRHSs are used both for pattern bindings and for Matches
+-- | GRHSs are used both for pattern bindings and for Matches
data GRHSs id
- = GRHSs [LGRHS id] -- Guarded RHSs
- (HsLocalBinds id) -- The where clause
+ = GRHSs {
+ grhssGRHSs :: [LGRHS id], -- ^ Guarded RHSs
+ grhssLocalBinds :: (HsLocalBinds id) -- ^ The where clause
+ }
type LGRHS id = Located (GRHS id)
+-- | Guarded Right Hand Side.
data GRHS id = GRHS [LStmt id] -- Guards
(LHsExpr id) -- Right hand side
\end{code}
-- the names which they group over in statements
-- Recursive statement (see Note [RecStmt] below)
- | RecStmt [LStmtLR idL idR]
- --- The next two fields are only valid after renaming
- [idR] -- The ids are a subset of the variables bound by the
- -- stmts that are used in stmts that follow the RecStmt
-
- [idR] -- 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
- -- 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*.
- (DictBinds idR) -- Method bindings of Ids bound by the
- -- RecStmt, and used afterwards
+ | 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
+ -- The only reason they are separate is becuase the DsArrows
+ -- code uses them separately, and I don't understand it well
+ -- enough to change it
+
+ -- 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_dicts :: DictBinds idR -- Method bindings of Ids bound by the
+ -- RecStmt, and used afterwards
+ }
\end{code}
ExprStmts are a bit tricky, because what they mean
Array comprehensions are handled like list comprehensions -=chak
-Note [RecStmt]
-~~~~~~~~~~~~~~
+Note [How RecStmt works]
+~~~~~~~~~~~~~~~~~~~~~~~~
Example:
HsDo [ BindStmt x ex
Nota Bene: the two a's have different types, even though they
have the same Name.
+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
+
\begin{code}
instance (OutputableBndr idL, OutputableBndr idR) => Outputable (StmtLR idL idR) where
byExprDoc = maybe empty (\byExpr -> hsep [ptext (sLit "by"), ppr byExpr]) maybeByExpr
pprStmt (GroupStmt (stmts, _) groupByClause) = (hsep [stmtsDoc, ptext (sLit "then group"), pprGroupByClause groupByClause])
where stmtsDoc = interpp'SP stmts
-pprStmt (RecStmt segment _ _ _ _) = ptext (sLit "rec") <+> braces (vcat (map ppr segment))
+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])]
pprGroupByClause :: (OutputableBndr id) => GroupByClause id -> SDoc
pprGroupByClause (GroupByNothing usingExpr) = hsep [ptext (sLit "using"), ppr usingExpr]
where usingExprDoc = either (\usingExpr -> hsep [ptext (sLit "using"), ppr usingExpr]) (const empty) eitherUsingExpr
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 DoExpr stmts body = ptext (sLit "do") <+> ppr_do_stmts stmts body
+pprDo (MDoExpr _) stmts body = ptext (sLit "mdo") <+> ppr_do_stmts stmts body
pprDo ListComp stmts body = pprComp brackets stmts body
pprDo PArrComp stmts body = pprComp pa_brackets stmts body
pprDo _ _ _ = panic "pprDo" -- PatGuard, ParStmtCxt
+ppr_do_stmts :: OutputableBndr id => [LStmt id] -> LHsExpr id -> SDoc
+-- Print a bunch of do stmts, with explicit braces and semicolons,
+-- so that we are not vulnerable to layout bugs
+ppr_do_stmts stmts body
+ = lbrace <+> pprDeeperList vcat ([ ppr s <> semi | s <- stmts] ++ [ppr body])
+ <+> rbrace
+
pprComp :: OutputableBndr id => (SDoc -> SDoc) -> [LStmt id] -> LHsExpr id -> SDoc
pprComp brack quals body
= brack $
\begin{code}
data HsMatchContext id -- Context of a Match
= FunRhs id Bool -- Function binding for f; True <=> written infix
- | CaseAlt -- Guard on a case alternative
- | LambdaExpr -- Pattern of a lambda
- | ProcExpr -- Pattern of a proc
- | PatBindRhs -- Pattern binding
+ | CaseAlt -- Patterns and guards on a case alternative
+ | LambdaExpr -- Patterns of a lambda
+ | ProcExpr -- Patterns of a proc
+ | PatBindRhs -- Patterns in the *guards* of a pattern binding
| RecUpd -- Record update [used only in DsExpr to
-- tell matchWrapper what sort of
-- runtime error message to generate]
-}
-- Used to generate the string for a *runtime* error message
-matchContextErrString :: Outputable id => HsMatchContext id -> String
-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 :: 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 (StmtCtxt (ParStmtCtxt c)) = matchContextErrString (StmtCtxt c)
matchContextErrString (StmtCtxt (TransformStmtCtxt 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 (StmtCtxt (PatGuard _)) = ptext (sLit "pattern guard")
+matchContextErrString (StmtCtxt DoExpr) = ptext (sLit "'do' expression")
+matchContextErrString (StmtCtxt (MDoExpr _)) = ptext (sLit "'mdo' expression")
+matchContextErrString (StmtCtxt ListComp) = ptext (sLit "list comprehension")
+matchContextErrString (StmtCtxt PArrComp) = ptext (sLit "array comprehension")
\end{code}
\begin{code}
projects / ghc-hetmet.git / blobdiff