Don't emit to_time deprecations in known-safe contexts

If the value is already a local time, there's no difference, so no need
to warn.

Correspondingly, avoid calling to_time in the handful of places we were
using it internally: it's easy to do, and we know we don't care about
the zone.

activerecord/lib/active_record/timestamp.rb

@@ -162,7 +162,7 @@ def current_time_from_proper_timezone
 
     def max_updated_column_timestamp
       timestamp_attributes_for_update_in_model
-        .filter_map { |attr| self[attr]&.to_time }
+        .filter_map { |attr| (v = self[attr]) && (v.is_a?(::Time) ? v : v.to_time) }
         .max
     end
 

activesupport/lib/active_support/core_ext/time/calculations.rb

@@ -319,7 +319,12 @@ def compare_with_coercion(other)
     if other.class == Time
       compare_without_coercion(other)
     elsif other.is_a?(Time)
-      compare_without_coercion(other.to_time)
+      # also avoid ActiveSupport::TimeWithZone#to_time before Rails 8.0
+      if other.respond_to?(:comparable_time)
+        compare_without_coercion(other.comparable_time)
+      else
+        compare_without_coercion(other.to_time)
+      end
     else
       to_datetime <=> other
     end

activesupport/lib/active_support/core_ext/time/compatibility.rb

@@ -13,4 +13,20 @@ class Time
   def to_time
     preserve_timezone ? self : getlocal
   end
+
+  def preserve_timezone # :nodoc:
+    active_support_local_zone == zone || super
+  end
+
+  private
+    @@active_support_local_tz = nil
+
+    def active_support_local_zone
+      @@active_support_local_zone = nil if @@active_support_local_tz != ENV["TZ"]
+      @@active_support_local_zone ||=
+        begin
+          @@active_support_local_tz = ENV["TZ"]
+          Time.new.zone
+        end
+    end
 end

activesupport/lib/active_support/testing/time_helpers.rb

@@ -163,10 +163,10 @@ def travel_to(date_or_time, with_usec: false)
           now = date_or_time.midnight.to_time
         elsif date_or_time.is_a?(String)
           now = Time.zone.parse(date_or_time)
-        elsif with_usec
-          now = date_or_time.to_time
         else
-          now = date_or_time.to_time.change(usec: 0)
+          now = date_or_time
+          now = now.to_time unless now.is_a?(Time)
+          now = now.change(usec: 0) unless with_usec
         end
 
         # +now+ must be in local system timezone, because +Time.at(now)+

activesupport/test/core_ext/date_and_time_compatibility_test.rb

@@ -43,6 +43,35 @@ def test_time_to_time_does_not_preserve_time_zone
     end
   end
 
+  def test_time_to_time_without_preserve_configured
+    with_preserve_timezone(nil) do
+      with_env_tz "US/Eastern" do
+        source = Time.new(2016, 4, 23, 15, 11, 12)
+        # No warning because it's already local
+        base_time = source.to_time
+
+        utc_time = base_time.getutc
+        converted_time = assert_deprecated(ActiveSupport.deprecator) { utc_time.to_time }
+
+        assert_equal source, base_time
+        assert_equal source, converted_time
+        assert_equal @system_offset, base_time.utc_offset
+        assert_equal @system_offset, converted_time.utc_offset
+      end
+    end
+
+    with_preserve_timezone(nil) do
+      with_env_tz "US/Eastern" do
+        foreign_time = Time.new(2016, 4, 23, 15, 11, 12, in: "-0700")
+        converted_time = assert_deprecated(ActiveSupport.deprecator) { foreign_time.to_time }
+
+        assert_equal foreign_time, converted_time
+        assert_equal @system_offset, converted_time.utc_offset
+        assert_not_equal foreign_time.utc_offset, converted_time.utc_offset
+      end
+    end
+  end
+
   def test_time_to_time_frozen_preserves_timezone
     with_preserve_timezone(true) do
       with_env_tz "US/Eastern" do