Warn about overlapping connected buildings

[naoliv]

It seems that for cases like this (also attached the example) JOSM should warn about the overlapping buildings.

We can only see an informational level message about "Overlapping Areas", but not any kind of warning about the overlapping buildings.

JOSM:

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2018-09-02 22:28:43 +0200 (Sun, 02 Sep 2018)
Revision:14220
Build-Date:2018-09-03 01:32:21
URL:https://josm.openstreetmap.de/svn/trunk

Identification: JOSM/1.5 (14220 en) Linux Debian GNU/Linux testing (buster)
Memory Usage: 819 MB / 7168 MB (329 MB allocated, but free)
Java version: 10.0.2+13-Debian-1, Oracle Corporation, OpenJDK 64-Bit Server VM
Screen: :0.0 1600x900, :0.1 1280x1024
Maximum Screen Size: 1600x1024
Java package: openjdk-10-jre:amd64-10.0.2+13-1
Java ATK Wrapper package: libatk-wrapper-java:all-0.33.3-21
VM arguments: [--add-modules=java.activation,java.se.ee, -Dawt.useSystemAAFontSettings=gasp]
Program arguments: [--language=en]
Dataset consistency test: No problems found

[Don-vip]

Not so easy as I thought. CrossingWays should probably be reworked to detect this, but it could quickly result in a major performance loss. Do we have a volunteer for the task? :)