Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

Issue #2237101 by Mile23, cordoval, YesCT, dawehner, tim.plunkett: clean up for Core/DependencyInjection CompilerPasses

Issue #2550641 by damiankloip: Use assert() in Drupal\Core\DependencyInjection\Container::__sleep instead of trigger error

Issue #2497243 by Fabianx, znerol, fgm, Wim Leers, darol100, jhedstrom, hussainweb, pfrenssen, neclimdul, jibran, Nitesh Sethia, dawehner, chx, catch, benjy, Aki Tendo: Replace Symfony container with a Drupal one, stored in cache

Issue #2190643 by Berdir, amateescu, Xano, yched: Serializing the container is a very very bad idea, let's prevent it?.

Issue #2004282 by dawehner, smiletrl, amateescu, tim.plunkett: Injected dependencies and serialization hell .