path: root/ghc/compiler/hsSyn/HsUtils.lhs

%
% (c) The University of Glasgow, 1992-2003
%

Here we collect a variety of helper functions that construct or
analyse HsSyn.  All these functions deal with generic HsSyn; functions
which deal with the intantiated versions are located elsewhere:

   Parameterised by	Module
   ----------------     -------------
   RdrName		parser/RdrHsSyn
   Name			rename/RnHsSyn
   Id			typecheck/TcHsSyn	

\begin{code}
module HsUtils where

#include "HsVersions.h"

import HsBinds
import HsExpr
import HsPat
import HsTypes	
import HsLit

import RdrName		( RdrName, getRdrName, mkRdrUnqual )
import Var		( Id )
import Type		( Type )
import DataCon		( DataCon, dataConWrapId, dataConSourceArity )
import OccName		( mkVarOccFS )
import Name		( Name )
import BasicTypes	( RecFlag(..) )
import SrcLoc
import FastString	( mkFastString )
import Outputable
import Util		( nOfThem )
import Bag
\end{code}


%************************************************************************
%*									*
	Some useful helpers for constructing syntax
%*									*
%************************************************************************

These functions attempt to construct a not-completely-useless SrcSpan
from their components, compared with the nl* functions below which
just attach noSrcSpan to everything.

\begin{code}
mkHsPar :: LHsExpr id -> LHsExpr id
mkHsPar e = L (getLoc e) (HsPar e)

-- gaw 2004
mkSimpleMatch :: [LPat id] -> LHsExpr id -> LMatch id
mkSimpleMatch pats rhs 
  = L loc $
    Match pats Nothing (GRHSs (unguardedRHS rhs) emptyLocalBinds)
  where
    loc = case pats of
		[]      -> getLoc rhs
		(pat:_) -> combineSrcSpans (getLoc pat) (getLoc rhs)

unguardedRHS :: LHsExpr id -> [LGRHS id]
unguardedRHS rhs@(L loc _) = [L loc (GRHS [] rhs)]

mkHsAppTy :: LHsType name -> LHsType name -> LHsType name
mkHsAppTy t1 t2 = addCLoc t1 t2 (HsAppTy t1 t2)

mkHsApp :: LHsExpr name -> LHsExpr name -> LHsExpr name
mkHsApp e1 e2 = addCLoc e1 e2 (HsApp e1 e2)

mkHsTyApp :: LHsExpr name -> [Type] -> LHsExpr name
mkHsTyApp expr []  = expr
mkHsTyApp expr tys = L (getLoc expr) (TyApp expr tys)

mkHsDictApp :: LHsExpr name -> [name] -> LHsExpr name
mkHsDictApp expr []	 = expr
mkHsDictApp expr dict_vars = L (getLoc expr) (DictApp expr dict_vars)

mkHsCoerce :: ExprCoFn -> HsExpr id -> HsExpr id
mkHsCoerce co_fn e | isIdCoercion co_fn = e
		   | otherwise		= HsCoerce co_fn e

mkHsLam :: [LPat id] -> LHsExpr id -> LHsExpr id
mkHsLam pats body = mkHsPar (L (getLoc body) (HsLam matches))
	where
	  matches = mkMatchGroup [mkSimpleMatch pats body]

mkMatchGroup :: [LMatch id] -> MatchGroup id
mkMatchGroup matches = MatchGroup matches placeHolderType

mkHsTyLam []     expr = expr
mkHsTyLam tyvars expr = L (getLoc expr) (TyLam tyvars expr)

mkHsDictLam []    expr = expr
mkHsDictLam dicts expr = L (getLoc expr) (DictLam dicts expr)

mkHsDictLet :: LHsBinds Id -> LHsExpr Id -> LHsExpr Id
-- Used for the dictionary bindings gotten from TcSimplify
-- We make them recursive to be on the safe side
mkHsDictLet binds expr 
  | isEmptyLHsBinds binds = expr
  | otherwise             = L (getLoc expr) (HsLet (HsValBinds val_binds) expr)
			  where
			    val_binds = ValBindsOut [(Recursive, binds)] []

mkHsConApp :: DataCon -> [Type] -> [HsExpr Id] -> LHsExpr Id
-- Used for constructing dictinoary terms etc, so no locations 
mkHsConApp data_con tys args 
  = foldl mk_app (noLoc (HsVar (dataConWrapId data_con)) `mkHsTyApp` tys) args
  where
    mk_app f a = noLoc (HsApp f (noLoc a))

mkSimpleHsAlt :: LPat id -> LHsExpr id -> LMatch id
-- A simple lambda with a single pattern, no binds, no guards; pre-typechecking
mkSimpleHsAlt pat expr 
  = mkSimpleMatch [pat] expr

-------------------------------
-- These are the bits of syntax that contain rebindable names
-- See RnEnv.lookupSyntaxName

mkHsIntegral   i       = HsIntegral   i  noSyntaxExpr
mkHsFractional f       = HsFractional f  noSyntaxExpr
mkHsDo ctxt stmts body = HsDo ctxt stmts body placeHolderType

mkNPat lit neg     = NPat lit neg noSyntaxExpr placeHolderType
mkNPlusKPat id lit = NPlusKPat id lit noSyntaxExpr noSyntaxExpr

mkExprStmt expr	    = ExprStmt expr noSyntaxExpr placeHolderType
mkBindStmt pat expr = BindStmt pat expr noSyntaxExpr noSyntaxExpr
mkRecStmt stmts	    = RecStmt stmts [] [] [] emptyLHsBinds

-------------------------------
--- A useful function for building @OpApps@.  The operator is always a
-- variable, and we don't know the fixity yet.
mkHsOpApp e1 op e2 = OpApp e1 (noLoc (HsVar op)) (error "mkOpApp:fixity") e2

mkHsSplice e = HsSplice unqualSplice e

unqualSplice = mkRdrUnqual (mkVarOccFS FSLIT("splice"))
		-- A name (uniquified later) to
		-- identify the splice

mkHsString s = HsString (mkFastString s)

-------------
userHsTyVarBndrs :: [Located name] -> [Located (HsTyVarBndr name)]
userHsTyVarBndrs bndrs = [ L loc (UserTyVar v) | L loc v <- bndrs ]
\end{code}


%************************************************************************
%*									*
	Constructing syntax with no location info
%*									*
%************************************************************************

\begin{code}
nlHsVar :: id -> LHsExpr id
nlHsVar n = noLoc (HsVar n)

nlHsLit :: HsLit -> LHsExpr id
nlHsLit n = noLoc (HsLit n)

nlVarPat :: id -> LPat id
nlVarPat n = noLoc (VarPat n)

nlLitPat :: HsLit -> LPat id
nlLitPat l = noLoc (LitPat l)

nlHsApp :: LHsExpr id -> LHsExpr id -> LHsExpr id
nlHsApp f x = noLoc (HsApp f x)

nlHsIntLit n = noLoc (HsLit (HsInt n))

nlHsApps :: id -> [LHsExpr id] -> LHsExpr id
nlHsApps f xs = foldl nlHsApp (nlHsVar f) xs
	     
nlHsVarApps :: id -> [id] -> LHsExpr id
nlHsVarApps f xs = noLoc (foldl mk (HsVar f) (map HsVar xs))
		 where
		   mk f a = HsApp (noLoc f) (noLoc a)

nlConVarPat :: id -> [id] -> LPat id
nlConVarPat con vars = nlConPat con (map nlVarPat vars)

nlInfixConPat :: id -> LPat id -> LPat id -> LPat id
nlInfixConPat con l r = noLoc (ConPatIn (noLoc con) (InfixCon l r))

nlConPat :: id -> [LPat id] -> LPat id
nlConPat con pats = noLoc (ConPatIn (noLoc con) (PrefixCon pats))

nlNullaryConPat :: id -> LPat id
nlNullaryConPat con = noLoc (ConPatIn (noLoc con) (PrefixCon []))

nlWildConPat :: DataCon -> LPat RdrName
nlWildConPat con = noLoc (ConPatIn (noLoc (getRdrName con))
				   (PrefixCon (nOfThem (dataConSourceArity con) nlWildPat)))

nlTuplePat pats box = noLoc (TuplePat pats box placeHolderType)
nlWildPat  = noLoc (WildPat placeHolderType)	-- Pre-typechecking

nlHsDo :: HsStmtContext Name -> [LStmt id] -> LHsExpr id -> LHsExpr id
nlHsDo ctxt stmts body = noLoc (mkHsDo ctxt stmts body)

nlHsOpApp e1 op e2 = noLoc (mkHsOpApp e1 op e2)

nlHsLam	match		= noLoc (HsLam (mkMatchGroup [match]))
nlHsPar e		= noLoc (HsPar e)
nlHsIf cond true false	= noLoc (HsIf cond true false)
nlHsCase expr matches	= noLoc (HsCase expr (mkMatchGroup matches))
nlTuple exprs box	= noLoc (ExplicitTuple exprs box)
nlList exprs		= noLoc (ExplicitList placeHolderType exprs)

nlHsAppTy f t		= noLoc (HsAppTy f t)
nlHsTyVar x		= noLoc (HsTyVar x)
nlHsFunTy a b		= noLoc (HsFunTy a b)
\end{code}



%************************************************************************
%*									*
		Bindings; with a location at the top
%*									*
%************************************************************************

\begin{code}
mkFunBind :: Located id -> [LMatch id] -> HsBind id
-- Not infix, with place holders for coercion and free vars
mkFunBind fn ms = FunBind { fun_id = fn, fun_infix = False, fun_matches = mkMatchGroup ms,
			    fun_co_fn = idCoercion, bind_fvs = placeHolderNames }


mkVarBind :: SrcSpan -> RdrName -> LHsExpr RdrName -> LHsBind RdrName
mkVarBind loc var rhs = mk_easy_FunBind loc var [] rhs

------------
mk_easy_FunBind :: SrcSpan -> RdrName -> [LPat RdrName]
		-> LHsExpr RdrName -> LHsBind RdrName

mk_easy_FunBind loc fun pats expr
  = L loc $ mkFunBind (L loc fun) [mkMatch pats expr emptyLocalBinds]

------------
mk_FunBind :: SrcSpan -> RdrName
	   -> [([LPat RdrName], LHsExpr RdrName)]
	   -> LHsBind RdrName

mk_FunBind loc fun [] = panic "TcGenDeriv:mk_FunBind"
mk_FunBind loc fun pats_and_exprs
  = L loc $ mkFunBind (L loc fun) matches
  where
    matches = [mkMatch p e emptyLocalBinds | (p,e) <-pats_and_exprs]

------------
mkMatch :: [LPat id] -> LHsExpr id -> HsLocalBinds id -> LMatch id
mkMatch pats expr binds
  = noLoc (Match (map paren pats) Nothing 
		 (GRHSs (unguardedRHS expr) binds))
  where
    paren p = case p of
		L _ (VarPat _) -> p
		L l _	       -> L l (ParPat p)
\end{code}


%************************************************************************
%*									*
	Collecting binders from HsBindGroups and HsBinds
%*									*
%************************************************************************

Get all the binders in some HsBindGroups, IN THE ORDER OF APPEARANCE. eg.

...
where
  (x, y) = ...
  f i j  = ...
  [a, b] = ...

it should return [x, y, f, a, b] (remember, order important).

\begin{code}
collectLocalBinders :: HsLocalBinds name -> [Located name]
collectLocalBinders (HsValBinds val_binds) = collectHsValBinders val_binds
collectLocalBinders (HsIPBinds _)   = []
collectLocalBinders EmptyLocalBinds = []

collectHsValBinders :: HsValBinds name -> [Located name]
collectHsValBinders (ValBindsIn binds sigs)  = collectHsBindLocatedBinders binds
collectHsValBinders (ValBindsOut binds sigs) = foldr collect_one [] binds
  where
   collect_one (_,binds) acc = foldrBag (collectAcc . unLoc) acc binds

collectAcc :: HsBind name -> [Located name] -> [Located name]
collectAcc (PatBind { pat_lhs = p }) acc = collectLocatedPatBinders p ++ acc
collectAcc (FunBind { fun_id = f })  acc    = f : acc
collectAcc (VarBind { var_id = f })  acc    = noLoc f : acc
collectAcc (AbsBinds { abs_exports = dbinds, abs_binds = binds }) acc
  = [noLoc dp | (_,dp,_,_) <- dbinds] ++ acc
	-- ++ foldr collectAcc acc binds
	-- I don't think we want the binders from the nested binds
	-- The only time we collect binders from a typechecked 
	-- binding (hence see AbsBinds) is in zonking in TcHsSyn

collectHsBindBinders :: LHsBinds name -> [name]
collectHsBindBinders binds = map unLoc (collectHsBindLocatedBinders binds)

collectHsBindLocatedBinders :: LHsBinds name -> [Located name]
collectHsBindLocatedBinders binds = foldrBag (collectAcc . unLoc) [] binds
\end{code}


%************************************************************************
%*									*
	Getting binders from statements
%*									*
%************************************************************************

\begin{code}
collectLStmtsBinders :: [LStmt id] -> [Located id]
collectLStmtsBinders = concatMap collectLStmtBinders

collectStmtsBinders :: [Stmt id] -> [Located id]
collectStmtsBinders = concatMap collectStmtBinders

collectLStmtBinders :: LStmt id -> [Located id]
collectLStmtBinders = collectStmtBinders . unLoc

collectStmtBinders :: Stmt id -> [Located id]
  -- Id Binders for a Stmt... [but what about pattern-sig type vars]?
collectStmtBinders (BindStmt pat _ _ _) = collectLocatedPatBinders pat
collectStmtBinders (LetStmt binds)      = collectLocalBinders binds
collectStmtBinders (ExprStmt _ _ _)   	= []
collectStmtBinders (RecStmt ss _ _ _ _)	= collectLStmtsBinders ss
collectStmtBinders other              	= panic "collectStmtBinders"
\end{code}


%************************************************************************
%*									*
%* 	Gathering stuff out of patterns
%*									*
%************************************************************************

This function @collectPatBinders@ works with the ``collectBinders''
functions for @HsBinds@, etc.  The order in which the binders are
collected is important; see @HsBinds.lhs@.

It collects the bounds *value* variables in renamed patterns; type variables
are *not* collected.

\begin{code}
collectPatBinders :: LPat a -> [a]
collectPatBinders pat = map unLoc (collectLocatedPatBinders pat)

collectLocatedPatBinders :: LPat a -> [Located a]
collectLocatedPatBinders pat = collectl pat []

collectPatsBinders :: [LPat a] -> [a]
collectPatsBinders pats = map unLoc (collectLocatedPatsBinders pats)

collectLocatedPatsBinders :: [LPat a] -> [Located a]
collectLocatedPatsBinders pats = foldr collectl [] pats

---------------------
collectl (L l pat) bndrs
  = go pat
  where
    go (VarPat var) 	   	  = L l var : bndrs
    go (VarPatOut var bs) 	  = L l var : collectHsBindLocatedBinders bs 
				    ++ bndrs
    go (WildPat _)	      	  = bndrs
    go (LazyPat pat)     	  = collectl pat bndrs
    go (BangPat pat)     	  = collectl pat bndrs
    go (AsPat a pat)     	  = a : collectl pat bndrs
    go (ParPat  pat)     	  = collectl pat bndrs
				  
    go (ListPat pats _)    	  = foldr collectl bndrs pats
    go (PArrPat pats _)    	  = foldr collectl bndrs pats
    go (TuplePat pats _ _)  	  = foldr collectl bndrs pats
				  
    go (ConPatIn c ps)   	  = foldr collectl bndrs (hsConArgs ps)
    go (ConPatOut c _ ds bs ps _) = map noLoc ds
				    ++ collectHsBindLocatedBinders bs
				    ++ foldr collectl bndrs (hsConArgs ps)
    go (LitPat _)	      	  = bndrs
    go (NPat _ _ _ _)		  = bndrs
    go (NPlusKPat n _ _ _)        = n : bndrs

    go (SigPatIn pat _)	 	  = collectl pat bndrs
    go (SigPatOut pat _)	  = collectl pat bndrs
    go (TypePat ty)               = bndrs
    go (DictPat ids1 ids2)        = map noLoc ids1 ++ map noLoc ids2
				    ++ bndrs
\end{code}

\begin{code}
collectSigTysFromPats :: [InPat name] -> [LHsType name]
collectSigTysFromPats pats = foldr collect_lpat [] pats

collectSigTysFromPat :: InPat name -> [LHsType name]
collectSigTysFromPat pat = collect_lpat pat []

collect_lpat pat acc = collect_pat (unLoc pat) acc

collect_pat (SigPatIn pat ty)  	acc = collect_lpat pat (ty:acc)
collect_pat (TypePat ty)       	acc = ty:acc

collect_pat (LazyPat pat)      	acc = collect_lpat pat acc
collect_pat (BangPat pat)      	acc = collect_lpat pat acc
collect_pat (AsPat a pat)      	acc = collect_lpat pat acc
collect_pat (ParPat  pat)      	acc = collect_lpat pat acc
collect_pat (ListPat pats _)   	acc = foldr collect_lpat acc pats
collect_pat (PArrPat pats _)   	acc = foldr collect_lpat acc pats
collect_pat (TuplePat pats _ _) acc = foldr collect_lpat acc pats
collect_pat (ConPatIn c ps)     acc = foldr collect_lpat acc (hsConArgs ps)
collect_pat other	        acc = acc 	-- Literals, vars, wildcard
\end{code}