[project @ 2005-07-25 11:24:24 by simonpj]

Better error recovery for type signatures

diff --git a/ghc/compiler/typecheck/TcBinds.lhs b/ghc/compiler/typecheck/TcBinds.lhs
index f410897..858512a 100644 (file)
--- a/ghc/compiler/typecheck/TcBinds.lhs
+++ b/ghc/compiler/typecheck/TcBinds.lhs
@@ -60,7 +60,7 @@ import SrcLoc         ( Located(..), unLoc, getLoc )
 import Bag
 import ErrUtils                ( Message )
 import Digraph         ( SCC(..), stronglyConnComp, flattenSCC )
-import Maybes          ( fromJust, isJust, orElse )
+import Maybes          ( fromJust, isJust, orElse, catMaybes )
 import Util            ( singleton )
 import BasicTypes      ( TopLevelFlag(..), isTopLevel, isNotTopLevel,
                          RecFlag(..), isNonRec )
@@ -882,17 +882,19 @@ Type signatures are tricky.  See Note [Signature skolems] in TcType
 
 \begin{code}
 tcTySigs :: [LSig Name] -> TcM [TcSigInfo]
-tcTySigs sigs = mappM tcTySig (filter isVanillaLSig sigs)
+tcTySigs sigs = do { mb_sigs <- mappM tcTySig (filter isVanillaLSig sigs)
+                  ; return (catMaybes mb_sigs) }
 
-tcTySig :: LSig Name -> TcM TcSigInfo
+tcTySig :: LSig Name -> TcM (Maybe TcSigInfo)
 tcTySig (L span (Sig (L _ name) ty))
-  = setSrcSpan span            $
+  = recoverM (return Nothing)  $
+    setSrcSpan span            $
     do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
        ; (tvs, theta, tau) <- tcInstSigType name scoped_names sigma_ty
        ; loc <- getInstLoc (SigOrigin (SigSkol name))
-       ; return (TcSigInfo { sig_id = mkLocalId name sigma_ty, 
-                             sig_tvs = tvs, sig_theta = theta, sig_tau = tau, 
-                             sig_scoped = scoped_names, sig_loc = loc }) }
+       ; return (Just (TcSigInfo { sig_id = mkLocalId name sigma_ty, 
+                                   sig_tvs = tvs, sig_theta = theta, sig_tau = tau, 
+                                   sig_scoped = scoped_names, sig_loc = loc })) }
   where
        -- The scoped names are the ones explicitly mentioned
        -- in the HsForAll.  (There may be more in sigma_ty, because