X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcEnv.lhs;h=cc50e50d732837f6d30763423dc6f151deb867e6;hp=2e3b80ba7e356008476191881a40f513de80dba1;hb=f4510d27c5883fe7e8570f4dd49d45a8b0122f2c;hpb=d29f86b1fe7daf919e9b47a9003daed74b812790

diff --git a/compiler/typecheck/TcEnv.lhs b/compiler/typecheck/TcEnv.lhs
index 2e3b80b..cc50e50 100644
--- a/compiler/typecheck/TcEnv.lhs
+++ b/compiler/typecheck/TcEnv.lhs
@@ -400,6 +400,9 @@ refineEnvironment :: Refinement -> TcM a -> TcM a
 -- I don't think I have to refine the set of global type variables in scope
 -- Reason: the refinement never increases that set
 refineEnvironment reft thing_inside
+  | isEmptyRefinement reft		-- Common case
+  = thing_inside
+  | otherwise
   = do	{ env <- getLclEnv
 	; let le' = mapNameEnv refine (tcl_env env)
  	; setLclEnv (env {tcl_env = le'}) thing_inside }