remove empty dir

[ghc-hetmet.git] / ghc / compiler / typecheck / TcDefaults.lhs

diff --git a/ghc/compiler/typecheck/TcDefaults.lhs b/ghc/compiler/typecheck/TcDefaults.lhs
index 66e56ef..6c9de36 100644 (file)
--- a/ghc/compiler/typecheck/TcDefaults.lhs
+++ b/ghc/compiler/typecheck/TcDefaults.lhs
@@ -4,77 +4,76 @@
 \section[TcDefaults]{Typechecking \tr{default} declarations}
 
 \begin{code}
-module TcDefaults ( tcDefaults, defaultDefaultTys ) where
+module TcDefaults ( tcDefaults ) where
 
 #include "HsVersions.h"
 
-import HsSyn           ( HsDecl(..), DefaultDecl(..) )
-import RnHsSyn         ( RenamedHsDecl )
-
-import TcMonad
-import TcEnv           ( tcLookupGlobal_maybe )
-import TcMonoType      ( tcHsType )
-import TcSimplify      ( tcSimplifyCheckThetas )
-
-import TysWiredIn      ( integerTy, doubleTy )
-import TcType           ( Type, mkClassPred )
+import HsSyn           ( DefaultDecl(..), LDefaultDecl )
+import Name            ( Name )
+import TcRnMonad
+import TcEnv           ( tcLookupClass )
+import TcHsType                ( tcHsSigType, UserTypeCtxt( DefaultDeclCtxt ) )
+import TcSimplify      ( tcSimplifyDefault )
+import TcType           ( Type, mkClassPred, isTauTy )
 import PrelNames       ( numClassName )
+import SrcLoc          ( Located(..) )
 import Outputable
-import HscTypes                ( TyThing(..) )
 \end{code}
 
 \begin{code}
-defaultDefaultTys = [integerTy, doubleTy]
-
-tcDefaults :: [RenamedHsDecl]
-          -> TcM [Type]            -- defaulting types to heave
+tcDefaults :: [LDefaultDecl Name]
+          -> TcM (Maybe [Type])    -- Defaulting types to heave
                                    -- into Tc monad for later use
                                    -- in Disambig.
-tcDefaults decls = tc_defaults [default_decl | DefD default_decl <- decls]
-
-tc_defaults [] = returnTc defaultDefaultTys
-
-tc_defaults [DefaultDecl [] locn]
-  = returnTc []                -- no defaults
 
-tc_defaults [DefaultDecl mono_tys locn]
-  = tcLookupGlobal_maybe numClassName  `thenNF_Tc` \ maybe_num ->
-    case maybe_num of
-       Just (AClass num_class) -> common_case num_class
-       other                   -> returnTc []
-               -- In the Nothing case, Num has not been sucked in, so the 
-               -- defaults will never be used; so simply discard the default decl.
-               -- This slightly benefits modules that don't use any
-               -- numeric stuff at all, by avoid the necessity of
-               -- always sucking in Num
-  where
-    common_case num_class
-      = tcAddSrcLoc locn $
-       mapTc tcHsType mono_tys `thenTc` \ tau_tys ->
+tcDefaults [] 
+  = getDefaultTys              -- No default declaration, so get the
+                               -- default types from the envt; 
+                               -- i.e. use the curent ones
+                               -- (the caller will put them back there)
+       -- It's important not to return defaultDefaultTys here (which
+       -- we used to do) because in a TH program, tcDefaults [] is called
+       -- repeatedly, once for each group of declarations between top-level
+       -- splices.  We don't want to carefully set the default types in
+       -- one group, only for the next group to ignore them and install
+       -- defaultDefaultTys
+
+tcDefaults [L locn (DefaultDecl [])]
+  = returnM (Just [])          -- Default declaration specifying no types
+
+tcDefaults [L locn (DefaultDecl mono_tys)]
+  = setSrcSpan locn                    $
+    addErrCtxt defaultDeclCtxt         $
+    tcLookupClass numClassName         `thenM` \ num_class ->
+    mappM tc_default_ty mono_tys       `thenM` \ tau_tys ->
     
-               -- Check that all the types are instances of Num
-               -- We only care about whether it worked or not
-       tcAddErrCtxt defaultDeclCtxt            $
-       tcSimplifyCheckThetas
-                   [{- Nothing given -}]
-                   [ mkClassPred num_class [ty] | ty <- tau_tys ]      `thenTc_`
+       -- Check that all the types are instances of Num
+       -- We only care about whether it worked or not
+    tcSimplifyDefault [mkClassPred num_class [ty] | ty <- tau_tys]     `thenM_`
     
-       returnTc tau_tys
-
+    returnM (Just tau_tys)
 
-tc_defaults decls@(DefaultDecl _ loc : _) =
-    tcAddSrcLoc loc $
+tcDefaults decls@(L locn (DefaultDecl _) : _) =
+    setSrcSpan locn $
     failWithTc (dupDefaultDeclErr decls)
 
 
+tc_default_ty hs_ty 
+ = tcHsSigType DefaultDeclCtxt hs_ty           `thenM` \ ty ->
+   checkTc (isTauTy ty) (polyDefErr hs_ty)     `thenM_`
+   returnM ty
+
 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)
+dupDefaultDeclErr (L _ (DefaultDecl _) : dup_things)
   = hang (ptext SLIT("Multiple default declarations"))
       4  (vcat (map pp dup_things))
   where
-    pp (DefaultDecl _ locn) = ptext SLIT("here was another default declaration") <+> ppr locn
+    pp (L locn (DefaultDecl _)) = ptext SLIT("here was another default declaration") <+> ppr locn
+
+polyDefErr ty 
+  = hang (ptext SLIT("Illegal polymorphic type in default declaration") <> colon) 4 (ppr ty) 
 \end{code}