[project @ 2002-09-09 12:50:26 by simonpj]

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

diff --git a/ghc/compiler/typecheck/TcMType.lhs b/ghc/compiler/typecheck/TcMType.lhs
index c13993a..d4d506a 100644 (file)
--- a/ghc/compiler/typecheck/TcMType.lhs
+++ b/ghc/compiler/typecheck/TcMType.lhs
@@ -936,6 +936,10 @@ check_valid_theta ctxt []
 check_valid_theta ctxt theta
   = getDOptsTc                                 `thenNF_Tc` \ dflags ->
     warnTc (notNull dups) (dupPredWarn dups)   `thenNF_Tc_`
+       -- Actually, in instance decls and type signatures, 
+       -- duplicate constraints are eliminated by TcMonoType.hoistForAllTys,
+       -- so this error can only fire for the context of a class or
+       -- data type decl.
     mapTc_ (check_source_ty dflags ctxt) theta
   where
     (_,dups) = removeDups tcCmpPred theta