Apply suggestions from code review

Author: MichaelHatherly

src/utilities.jl

@@ -419,7 +419,7 @@ function keywords(func, m::Method)
     # table is a MethodTable object. For some reason, the :kwsorter field is not always
     # defined. An undefined kwsorter seems to imply that there are no methods in the
     # MethodTable with keyword arguments.
-    if  !hasfield(Core.MethodTable, :kwsorter) || isdefined(table, :kwsorter)
+    if  !(fieldindex(Core.MethodTable, :kwsorter, false) > 0) || isdefined(table, :kwsorter)
         # Fetching method keywords stolen from base/replutil.jl:572-576 (commit 3b45cdc9aab0):
         kwargs = VERSION < v"1.4.0-DEV.215" ? Base.kwarg_decl(m, typeof(table.kwsorter)) : Base.kwarg_decl(m)
         if isa(kwargs, Vector) && length(kwargs) > 0

test/tests.jl

@@ -42,7 +42,7 @@ end
         @test isdefined(methods(M.j_1), :mt)
         local mt = methods(M.j_1).mt
         @test isa(mt, Core.MethodTable)
-        if hasfield(Core.MethodTable, :kwsorter)
+        if fieldindex(Core.MethodTable, :kwsorter, false) > 0
             @test isdefined(mt, :kwsorter)
         end
         # .kwsorter is not always defined -- namely, it seems when none of the methods