+ doptsTc Opt_GlasgowExts `thenTc` \ gla_ext_opt ->
+ let
+ gla_exts = gla_ext_opt || not (maybeToBool def_methods)
+ -- Accept extensions if gla_exts is on,
+ -- or if we're looking at an interface file decl
+ in -- (in which case def_methods = Nothing
+
+ checkTc (gla_exts || length tyvar_names == 1)