Version 4.5.1 is the last one available from central - http://mvnrepository.com/artifact/org.eclipse.jdt.core.compiler/ecj/4.5.1
Unfortunately there is a nasty bug, which was fixed only in 4.5.2.
I cannot seem to find a binary package anywhere. I tried building it from sources but failed (details below). What is the recommended way to obtain 4.5.2 binary?
I tried https://github.com/eclipse/eclipse.jdt.core but it doesn't have any relevant tags.
I tried building the tag R4_5_2 from https://git.eclipse.org/c/jdt/eclipse.jdt.core.git/tag/?h=R4_5_2
Suprisingly it still has a snapshot version 4.5.2-SNAPSHOT and requires a parent of the same version. I can try building the parent project, but I'd expect it to be already available in some repository etc. Before proceeding I'd like at least to know if this path is going to lead anywhere.
Finally I came across Project Tycho but I think this is only relevant if I'm creating a new plugin.
I've found one here by random googling: http://download.eclipse.org/eclipse/downloads/drops4/R-4.5.2-201602121500/#JDTCORE
However the timestamp is different than what I get in my Eclipse Mars. Here it's 20160212-1500 and in Eclipse I have 20160128-0629