X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcSimplify.lhs;h=e25f51015f2a41c99992cc2a0ea5741cd6d8f1a8;hp=197d6820b091ebe933aa9446385addf73d700ecd;hb=5882c5ff503c5b3b425708621cbc3371cc36e5de;hpb=024aa13a0a6bfd2d68f4c551824357b87e732f5b

diff --git a/compiler/typecheck/TcSimplify.lhs b/compiler/typecheck/TcSimplify.lhs
index 197d682..e25f510 100644
--- a/compiler/typecheck/TcSimplify.lhs
+++ b/compiler/typecheck/TcSimplify.lhs
@@ -642,6 +642,11 @@ solve_wanteds inert wanted@(WC { wc_flat = flats, wc_impl = implics, wc_insol =
   = do { traceTcS "solveWanteds {" (ppr wanted)
 
                  -- Try the flat bit
+                 -- Discard from insols all the derived/given constraints
+                 -- because they will show up again when we try to solve
+                 -- everything else.  Solving them a second time is a bit
+                 -- of a waste, but the code is simple, and the program is
+                 -- wrong anyway!
        ; let all_flats = flats `unionBags` keepWanted insols
        ; inert1 <- solveInteractWanted inert (bagToList all_flats)