Issue #3390903 by sakthi_dev, dpi, smustgrave: \Drupal\Core\Queue\QueueInterface::createItem is typehinted as possibly returning bool, but never returns true

Issue #2941148 by quietone, bruno.bicudo, ravi.shankar, Sweetchuck, beatrizrodrigues, lucienchalom, VitaliyB98, WagnerMelo, sophiavs, ankitjain28may, daffie, longwave, Sutharsan, borisson_, cosmicdreams, heykarthikwithu, catch: Fix Drupal.Commenting.FunctionComment.MissingReturnType

Issue #3175287 by murilohp, quietone, SivaprasadC, ankithashetty, anmolgoyal74, sarvjeetsingh, xjm, longwave: Remove accidentally duplicated words in code comments

Issue #2835989 by gwagroves, Jo Fitzgerald, alexpott: DatabaseQueue::numberOfItems should return an integer

Issue #2719695 by alexpott, Mile23: Fix 'Drupal.Classes.ClassDeclaration.CloseBraceAfterBody' coding standard

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

Issue #1392754 by tss, justAChris, jhodgdon: Comply with new documentation standards for @file for namespaced class files

Issue #1928056 by pwolanin: Queue system createItem() should return ID, and  properties should be documented.

Issue #1326664 by Lars Toomre, Albert Volkman, sven.lauer, tim.plunkett: API docs cleanup for parts of system module and other files