Don't default to YAML dumping when quoting values

This behavior exists only to support fixtures, so we should handle it
there. Leaving it in `#quote` can cause very subtle bugs to slip
through, by things appearing to work when they should be blowing up
loudly, such as #18385.

activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb

@@ -289,7 +289,13 @@ module ActiveRecord
           [columns[name], value]
         end
         key_list = fixture.keys.map { |name| quote_column_name(name) }
-        value_list = prepare_binds_for_database(binds).map { |_, value| quote(value) }
+        value_list = prepare_binds_for_database(binds).map do |_, value|
+          begin
+            quote(value)
+          rescue TypeError
+            quote(YAML.dump(value))
+          end
+        end
 
         execute "INSERT INTO #{quote_table_name(table_name)} (#{key_list.join(', ')}) VALUES (#{value_list.join(', ')})", 'Fixture Insert'
       end

activerecord/lib/active_record/connection_adapters/abstract/quoting.rb

@@ -125,8 +125,7 @@ module ActiveRecord
         when Date, Time then "'#{quoted_date(value)}'"
         when Symbol     then "'#{quote_string(value.to_s)}'"
         when Class      then "'#{value}'"
-        else
-          "'#{quote_string(YAML.dump(value))}'"
+        else raise TypeError, "can't quote #{value.class.name}"
         end
       end
 

activerecord/test/cases/quoting_test.rb

@@ -125,14 +125,11 @@ module ActiveRecord
       end
 
       def test_crazy_object
-        crazy = Class.new.new
-        expected = "'#{YAML.dump(crazy)}'"
-        assert_equal expected, @quoter.quote(crazy, nil)
-      end
-
-      def test_crazy_object_calls_quote_string
-        crazy = Class.new { def initialize; @lol = 'lo\l' end }.new
-        assert_match "lo\\\\l", @quoter.quote(crazy, nil)
+        crazy = Object.new
+        e = assert_raises(TypeError) do
+          @quoter.quote(crazy, nil)
+        end
+        assert_equal "can't quote Object", e.message
       end
 
       def test_quote_string_no_column