[ruby/date] Use `assert_deprecated_warn`

https://github.com/ruby/date/commit/c55004715a

test/date/test_date_parse.rb

@@ -864,7 +864,7 @@ class TestDateParse < Test::Unit::TestCase
     h = Date._iso8601(nil)
     assert_equal({}, h)
 
-    h = assert_warn(/deprecated/) {Date._iso8601('01-02-03T04:05:06Z'.to_sym)}
+    h = assert_deprecated_warn {Date._iso8601('01-02-03T04:05:06Z'.to_sym)}
     assert_equal([2001, 2, 3, 4, 5, 6, 0],
       h.values_at(:year, :mon, :mday, :hour, :min, :sec, :offset))
   end
@@ -886,7 +886,7 @@ class TestDateParse < Test::Unit::TestCase
     h = Date._rfc3339(nil)
     assert_equal({}, h)
 
-    h = assert_warn(/deprecated/) {Date._rfc3339('2001-02-03T04:05:06Z'.to_sym)}
+    h = assert_deprecated_warn {Date._rfc3339('2001-02-03T04:05:06Z'.to_sym)}
     assert_equal([2001, 2, 3, 4, 5, 6, 0],
       h.values_at(:year, :mon, :mday, :hour, :min, :sec, :offset))
   end
@@ -975,7 +975,7 @@ class TestDateParse < Test::Unit::TestCase
     h = Date._xmlschema(nil)
     assert_equal({}, h)
 
-    h = assert_warn(/deprecated/) {Date._xmlschema('2001-02-03'.to_sym)}
+    h = assert_deprecated_warn {Date._xmlschema('2001-02-03'.to_sym)}
     assert_equal([2001, 2, 3, nil, nil, nil, nil],
       h.values_at(:year, :mon, :mday, :hour, :min, :sec, :offset))
   end
@@ -1014,7 +1014,7 @@ class TestDateParse < Test::Unit::TestCase
     h = Date._rfc2822(nil)
     assert_equal({}, h)
 
-    h = assert_warn(/deprecated/) {Date._rfc2822('Sat, 3 Feb 2001 04:05:06 UT'.to_sym)}
+    h = assert_deprecated_warn {Date._rfc2822('Sat, 3 Feb 2001 04:05:06 UT'.to_sym)}
     assert_equal([2001, 2, 3, 4, 5, 6, 0],
       h.values_at(:year, :mon, :mday, :hour, :min, :sec, :offset))
   end
@@ -1041,7 +1041,7 @@ class TestDateParse < Test::Unit::TestCase
     h = Date._httpdate(nil)
     assert_equal({}, h)
 
-    h = assert_warn(/deprecated/) {Date._httpdate('Sat, 03 Feb 2001 04:05:06 GMT'.to_sym)}
+    h = assert_deprecated_warn {Date._httpdate('Sat, 03 Feb 2001 04:05:06 GMT'.to_sym)}
     assert_equal([2001, 2, 3, 4, 5, 6, 0],
       h.values_at(:year, :mon, :mday, :hour, :min, :sec, :offset))
   end
@@ -1124,7 +1124,7 @@ class TestDateParse < Test::Unit::TestCase
     h = Date._jisx0301(nil)
     assert_equal({}, h)
 
-    h = assert_warn(/deprecated/) {Date._jisx0301('H13.02.03T04:05:06.07+0100'.to_sym)}
+    h = assert_deprecated_warn {Date._jisx0301('H13.02.03T04:05:06.07+0100'.to_sym)}
     assert_equal([2001, 2, 3, 4, 5, 6, 3600],
       h.values_at(:year, :mon, :mday, :hour, :min, :sec, :offset))
   end

tool/lib/core_assertions.rb

@@ -592,14 +592,14 @@ eom
 
       def assert_deprecated_warning(mesg = /deprecated/)
         assert_warning(mesg) do
-          Warning[:deprecated] = true
+          Warning[:deprecated] = true if Warning.respond_to?(:[]=)
           yield
         end
       end
 
       def assert_deprecated_warn(mesg = /deprecated/)
         assert_warn(mesg) do
-          Warning[:deprecated] = true
+          Warning[:deprecated] = true if Warning.respond_to?(:[]=)
           yield
         end
       end