[project @ 2004-11-18 00:56:18 by igloo]

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

diff --git a/ghc/compiler/typecheck/TcTyClsDecls.lhs b/ghc/compiler/typecheck/TcTyClsDecls.lhs
index 9662e43..3e72f0e 100644 (file)
--- a/ghc/compiler/typecheck/TcTyClsDecls.lhs
+++ b/ghc/compiler/typecheck/TcTyClsDecls.lhs
@@ -372,6 +372,9 @@ tcTyClDecl1 calc_vrcs calc_isrec
   ; want_generic <- doptM Opt_Generics
   ; tycon <- fixM (\ tycon -> do 
        { unbox_strict <- doptM Opt_UnboxStrictFields
+       ; gla_exts <- doptM Opt_GlasgowExts
+       ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
+
        ; data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data tycon tvs')) cons
        ; let tc_rhs = case new_or_data of
                        DataType -> mkDataTyConRhs stupid_theta data_cons
@@ -385,6 +388,9 @@ tcTyClDecl1 calc_vrcs calc_isrec
   where
     arg_vrcs = calc_vrcs tc_name
     is_rec   = calc_isrec tc_name
+    h98_syntax = case cons of  -- All constructors have same shape
+                       L _ (GadtDecl {}) : _ -> False
+                       other -> True
 
 tcTyClDecl1 calc_vrcs calc_isrec 
   (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs, 
@@ -441,6 +447,9 @@ tcConDecl unbox_strict DataType tycon tc_tvs        -- Ordinary data types
     ; let 
        is_vanilla = null ex_tvs && null (unLoc ex_ctxt) 
                -- Vanilla iff no ex_tvs and no context
+               -- Must check the context too because of
+               -- implicit params; e.g.
+               --  data T = (?x::Int) => MkT Int
 
        tc_datacon is_infix field_lbls btys
          = do { let { bangs = map getBangStrictness btys }
@@ -455,7 +464,10 @@ tcConDecl unbox_strict DataType tycon tc_tvs       -- Ordinary data types
     ; case details of
        PrefixCon btys     -> tc_datacon False [] btys
        InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
-       RecCon fields      -> do { checkTc is_vanilla (exRecConErr name)
+       RecCon fields      -> do { checkTc (null ex_tvs) (exRecConErr name)
+               -- It's ok to have an implicit-parameter context
+               -- for the data constructor, provided it binds
+               -- no type variables
                                 ; let { (field_names, btys) = unzip fields }
                                 ; tc_datacon False field_names btys } }
 
@@ -644,7 +656,7 @@ checkValidClass cls
 
                -- Check that for a generic method, the type of 
                -- the method is sufficiently simple
-       ; checkTc (dm /= GenDefMeth || validGenericMethodType op_ty)
+       ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
                  (badGenericMethodType op_name op_ty)
        }
        where
@@ -696,7 +708,7 @@ genericMultiParamErr clas
 badGenericMethodType op op_ty
   = hang (ptext SLIT("Generic method type is too complex"))
        4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
-               ptext SLIT("You can only use type variables, arrows, and tuples")])
+               ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
 
 recSynErr syn_decls
   = setSrcSpan (getLoc (head sorted_decls)) $
@@ -727,4 +739,8 @@ exRecConErr name
 badDataConTyCon data_con
   = hang (ptext SLIT("Data constructor does not return its parent type:"))
        2 (ppr data_con)
+
+badGadtDecl tc_name
+  = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
+        , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
 \end{code}