Move `to_time` to `DateTime` compatibility.rb file

We are overriding it in `Time` and `ActiveSupport::TimeWithZone` so
there's no point in having it in the `DateAndTime::Compatibility`
module. Also add some docs for the `to_time` implementations.

3 files changed, 13 insertions, 5 deletions

diff --git a/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb b/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb
index 3f4e236ab7..ab80392460 100644
--- a/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb
+++ b/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb
@@ -10,9 +10,5 @@ module DateAndTime
     # this behavior, but new apps will have an initializer that sets
     # this to true, because the new behavior is preferred.
     mattr_accessor(:preserve_timezone, instance_writer: false) { false }
-
-    def to_time
-      preserve_timezone ? getlocal(utc_offset) : getlocal
-    end
   end
 end
diff --git a/activesupport/lib/active_support/core_ext/date_time/compatibility.rb b/activesupport/lib/active_support/core_ext/date_time/compatibility.rb
index 30bb7f4a60..eb8b8b2c65 100644
--- a/activesupport/lib/active_support/core_ext/date_time/compatibility.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/compatibility.rb
@@ -1,5 +1,15 @@
 require "active_support/core_ext/date_and_time/compatibility"
 
 class DateTime
-  prepend DateAndTime::Compatibility
+  include DateAndTime::Compatibility
+
+  remove_possible_method :to_time
+
+  # Either return an instance of `Time` with the same UTC offset
+  # as +self+ or an instance of `Time` representing the same time
+  # in the the local system timezone depending on the setting of
+  # on the setting of +ActiveSupport.to_time_preserves_timezone+.
+  def to_time
+    preserve_timezone ? getlocal(utc_offset) : getlocal
+  end
 end
diff --git a/activesupport/lib/active_support/core_ext/time/compatibility.rb b/activesupport/lib/active_support/core_ext/time/compatibility.rb
index 32e5608b32..45e86b77ce 100644
--- a/activesupport/lib/active_support/core_ext/time/compatibility.rb
+++ b/activesupport/lib/active_support/core_ext/time/compatibility.rb
@@ -6,6 +6,8 @@ class Time
 
   remove_possible_method :to_time
 
+  # Either return +self+ or the time in the local system timezone depending
+  # on the setting of +ActiveSupport.to_time_preserves_timezone+.
   def to_time
     preserve_timezone ? self : getlocal
   end