Fix Trac #2114: error reporting for 'forall' without appropriate flags

[ghc-hetmet.git] / compiler / rename / RnEnv.lhs

diff --git a/compiler/rename/RnEnv.lhs b/compiler/rename/RnEnv.lhs
index 47595e2..59451fc 100644 (file)
--- a/compiler/rename/RnEnv.lhs
+++ b/compiler/rename/RnEnv.lhs
@@ -36,7 +36,7 @@ module RnEnv (
        mapFvRn, mapFvRnCPS,
        warnUnusedMatches, warnUnusedModules, warnUnusedImports, 
        warnUnusedTopBinds, warnUnusedLocalBinds,
-       dataTcOccs, unknownNameErr,
+       dataTcOccs, unknownNameErr
     ) where
 
 #include "HsVersions.h"
@@ -60,7 +60,8 @@ import DataCon                ( dataConFieldLabels )
 import OccName         ( OccName, tcName, isDataOcc, pprNonVarNameSpace, occNameSpace,
                          reportIfUnused, occNameFS )
 import Module          ( Module, ModuleName )
-import PrelNames       ( mkUnboundName, rOOT_MAIN, iNTERACTIVE, consDataConKey, hasKey )
+import PrelNames       ( mkUnboundName, rOOT_MAIN, iNTERACTIVE, 
+                         consDataConKey, hasKey, forall_tv_RDR )
 import UniqSupply
 import BasicTypes      ( IPName, mapIPName, Fixity )
 import SrcLoc          ( SrcSpan, srcSpanStart, Located(..), eqLocated, unLoc,
@@ -1018,9 +1019,14 @@ shadowedNameWarn doc occ shadowed_locs
     $$ doc
 
 unknownNameErr rdr_name
-  = sep [ptext SLIT("Not in scope:"), 
-        nest 2 $ pprNonVarNameSpace (occNameSpace (rdrNameOcc rdr_name))
-                 <+> quotes (ppr rdr_name)]
+  = vcat [ hang (ptext SLIT("Not in scope:")) 
+             2 (pprNonVarNameSpace (occNameSpace (rdrNameOcc rdr_name))
+                         <+> quotes (ppr rdr_name))
+        , extra ]
+  where
+    extra | rdr_name == forall_tv_RDR 
+         = ptext SLIT("Perhaps you intended to use -XRankNTypes or similar flag")
+         | otherwise = empty
 
 unknownSubordinateErr doc op   -- Doc is "method of class" or 
                                -- "field of constructor"