Coments and debug tracing only

See Trac #15205

compiler/typecheck/TcSimplify.hs

@@ -1696,6 +1696,7 @@ neededEvVars implic@(Implic { ic_given = givens
       ; traceTcS "neededEvVars" $
         vcat [ text "old_needs:" <+> ppr old_needs
              , text "seeds3:" <+> ppr seeds3
+             , text "tcvs:" <+> ppr tcvs
              , text "ev_binds:" <+> ppr ev_binds
              , text "live_ev_binds:" <+> ppr live_ev_binds ]
 
@@ -1756,6 +1757,9 @@ all done by neededEvVars.
 This led to a remarkable 25% overall compiler allocation decrease in
 test T12227.
 
+But we don't get to discard all redundant equality superclasses, alas;
+see Trac #15205.
+
 Note [Tracking redundant constraints]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 With Opt_WarnRedundantConstraints, GHC can report which