%
-% (c) The AQUA Project, Glasgow University, 1993-1995
+% (c) The AQUA Project, Glasgow University, 1993-1998
%
\section[TcDefaults]{Typechecking \tr{default} declarations}
\begin{code}
+module TcDefaults ( tcDefaults ) where
+
#include "HsVersions.h"
-module TcDefaults ( tcDefaults ) where
+import HsSyn ( HsDecl(..), DefaultDecl(..) )
+import RnHsSyn ( RenamedHsDecl )
import TcMonad
-import AbsSyn
-
-import AbsPrel ( intTy, doubleTy, unitTy )
-import AbsUniType ( UniType
- IF_ATTACK_PRAGMAS(COMMA cmpUniType)
- )
-import CE ( lookupCE, CE(..) )
-import E
-import Inst
-import Name
-import TcMonoType ( tcMonoType )
+import TcEnv ( tcLookupClassByKey )
+import TcMonoType ( tcHsType )
import TcSimplify ( tcSimplifyCheckThetas )
-import TVE
-import Unique ( numClassKey, Unique )
+
+import TysWiredIn ( intTy, doubleTy )
+import Type ( Type )
+import Unique ( numClassKey )
+import ErrUtils ( addShortErrLocLine )
+import Outputable
import Util
\end{code}
\begin{code}
-tcDefaults :: E
- -> [RenamedDefaultDecl]
- -> TcM [UniType] -- defaulting types to heave
+default_default = [intTy, doubleTy] -- language-specified default `default'
+
+tcDefaults :: [RenamedHsDecl]
+ -> TcM s [Type] -- defaulting types to heave
-- into Tc monad for later use
-- in Disambig.
+tcDefaults decls = tc_defaults [default_decl | DefD default_decl <- decls]
-tcDefaults _ []
- = returnTc [intTy, doubleTy] -- language-specified default `default'
-
-tcDefaults e [DefaultDecl mono_tys locn]
- = let
- ce = getE_CE e
- tce = getE_TCE e
- tve = nullTVE
+tc_defaults [] = returnTc default_default
- num_clas = lookupCE ce (PreludeClass numClassKey (panic "tcDefaults"))
- in
- babyTcMtoTcM (mapB_Tc (tcMonoType ce tce tve) mono_tys) `thenTc` \ tau_tys ->
+tc_defaults [DefaultDecl mono_tys locn]
+ = tcAddSrcLoc locn $
+ mapTc tcHsType mono_tys `thenTc` \ tau_tys ->
- -- compensate for extreme parser hack: `default ()' actually
- -- sends the *type* () through to here. Squash it.
case tau_tys of
- [ty] | ty == unitTy -> returnTc []
-
- _ -> -- (Back to your regularly scheduled programming...)
+ [] -> returnTc [] -- no defaults
+ _ ->
-- Check that all the types are instances of Num
-
- tcSimplifyCheckThetas (DefaultDeclOrigin locn)
- [ (num_clas, ty) | ty <- tau_tys ] `thenTc` \ _ ->
-- We only care about whether it worked or not
- returnTc tau_tys -- caller will bung them into Tc monad
+ tcAddErrCtxt defaultDeclCtxt $
+ tcLookupClassByKey numClassKey `thenNF_Tc` \ num ->
+ tcSimplifyCheckThetas
+ [{- Nothing given -}]
+ [ (num, [ty]) | ty <- tau_tys ] `thenTc_`
+
+ returnTc tau_tys
+
+tc_defaults decls
+ = failWithTc (dupDefaultDeclErr decls)
+
+
+defaultDeclCtxt = ptext SLIT("when checking that each type in a default declaration")
+ $$ ptext SLIT("is an instance of class Num")
+
+
+dupDefaultDeclErr (DefaultDecl _ locn1 : dup_things)
+ = vcat (item1 : map dup_item dup_things)
+ where
+ item1
+ = addShortErrLocLine locn1 (ptext SLIT("multiple default declarations"))
-tcDefaults _ (_:_)
- = error "ERROR: You can only have one `default' declaration per module."
- -- ToDo: proper error msg.
+ dup_item (DefaultDecl _ locn)
+ = addShortErrLocLine locn (ptext SLIT("here was another default declaration"))
\end{code}